1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * kernel/sched/core.c
4 *
5 * Core kernel scheduler code and related syscalls
6 *
7 * Copyright (C) 1991-2002 Linus Torvalds
8 */
9 #include <linux/highmem.h>
10 #include <linux/hrtimer_api.h>
11 #include <linux/ktime_api.h>
12 #include <linux/sched/signal.h>
13 #include <linux/syscalls_api.h>
14 #include <linux/debug_locks.h>
15 #include <linux/prefetch.h>
16 #include <linux/capability.h>
17 #include <linux/pgtable_api.h>
18 #include <linux/wait_bit.h>
19 #include <linux/jiffies.h>
20 #include <linux/spinlock_api.h>
21 #include <linux/cpumask_api.h>
22 #include <linux/lockdep_api.h>
23 #include <linux/hardirq.h>
24 #include <linux/softirq.h>
25 #include <linux/refcount_api.h>
26 #include <linux/topology.h>
27 #include <linux/sched/clock.h>
28 #include <linux/sched/cond_resched.h>
29 #include <linux/sched/cputime.h>
30 #include <linux/sched/debug.h>
31 #include <linux/sched/hotplug.h>
32 #include <linux/sched/init.h>
33 #include <linux/sched/isolation.h>
34 #include <linux/sched/loadavg.h>
35 #include <linux/sched/mm.h>
36 #include <linux/sched/nohz.h>
37 #include <linux/sched/rseq_api.h>
38 #include <linux/sched/rt.h>
39
40 #include <linux/blkdev.h>
41 #include <linux/context_tracking.h>
42 #include <linux/cpuset.h>
43 #include <linux/delayacct.h>
44 #include <linux/init_task.h>
45 #include <linux/interrupt.h>
46 #include <linux/ioprio.h>
47 #include <linux/kallsyms.h>
48 #include <linux/kcov.h>
49 #include <linux/kprobes.h>
50 #include <linux/llist_api.h>
51 #include <linux/mmu_context.h>
52 #include <linux/mmzone.h>
53 #include <linux/mutex_api.h>
54 #include <linux/nmi.h>
55 #include <linux/nospec.h>
56 #include <linux/perf_event_api.h>
57 #include <linux/profile.h>
58 #include <linux/psi.h>
59 #include <linux/rcuwait_api.h>
60 #include <linux/sched/wake_q.h>
61 #include <linux/scs.h>
62 #include <linux/slab.h>
63 #include <linux/syscalls.h>
64 #include <linux/vtime.h>
65 #include <linux/wait_api.h>
66 #include <linux/workqueue_api.h>
67
68 #ifdef CONFIG_PREEMPT_DYNAMIC
69 # ifdef CONFIG_GENERIC_ENTRY
70 # include <linux/entry-common.h>
71 # endif
72 #endif
73
74 #include <uapi/linux/sched/types.h>
75
76 #include <asm/irq_regs.h>
77 #include <asm/switch_to.h>
78 #include <asm/tlb.h>
79
80 #define CREATE_TRACE_POINTS
81 #include <linux/sched/rseq_api.h>
82 #include <trace/events/sched.h>
83 #undef CREATE_TRACE_POINTS
84
85 #include "sched.h"
86 #include "stats.h"
87 #include "autogroup.h"
88
89 #include "autogroup.h"
90 #include "pelt.h"
91 #include "smp.h"
92 #include "stats.h"
93
94 #include "../workqueue_internal.h"
95 #include "../../io_uring/io-wq.h"
96 #include "../smpboot.h"
97
98 /*
99 * Export tracepoints that act as a bare tracehook (ie: have no trace event
100 * associated with them) to allow external modules to probe them.
101 */
102 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_cfs_tp);
103 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_rt_tp);
104 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp);
105 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp);
106 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp);
107 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_thermal_tp);
108 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_cpu_capacity_tp);
109 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp);
110 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp);
111 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp);
112 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
113
114 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
115
116 #ifdef CONFIG_SCHED_DEBUG
117 /*
118 * Debugging: various feature bits
119 *
120 * If SCHED_DEBUG is disabled, each compilation unit has its own copy of
121 * sysctl_sched_features, defined in sched.h, to allow constants propagation
122 * at compile time and compiler optimization based on features default.
123 */
124 #define SCHED_FEAT(name, enabled) \
125 (1UL << __SCHED_FEAT_##name) * enabled |
126 const_debug unsigned int sysctl_sched_features =
127 #include "features.h"
128 0;
129 #undef SCHED_FEAT
130
131 /*
132 * Print a warning if need_resched is set for the given duration (if
133 * LATENCY_WARN is enabled).
134 *
135 * If sysctl_resched_latency_warn_once is set, only one warning will be shown
136 * per boot.
137 */
138 __read_mostly int sysctl_resched_latency_warn_ms = 100;
139 __read_mostly int sysctl_resched_latency_warn_once = 1;
140 #endif /* CONFIG_SCHED_DEBUG */
141
142 /*
143 * Number of tasks to iterate in a single balance run.
144 * Limited because this is done with IRQs disabled.
145 */
146 const_debug unsigned int sysctl_sched_nr_migrate = SCHED_NR_MIGRATE_BREAK;
147
148 __read_mostly int scheduler_running;
149
150 #ifdef CONFIG_SCHED_CORE
151
152 DEFINE_STATIC_KEY_FALSE(__sched_core_enabled);
153
154 /* kernel prio, less is more */
__task_prio(struct task_struct * p)155 static inline int __task_prio(struct task_struct *p)
156 {
157 if (p->sched_class == &stop_sched_class) /* trumps deadline */
158 return -2;
159
160 if (rt_prio(p->prio)) /* includes deadline */
161 return p->prio; /* [-1, 99] */
162
163 if (p->sched_class == &idle_sched_class)
164 return MAX_RT_PRIO + NICE_WIDTH; /* 140 */
165
166 return MAX_RT_PRIO + MAX_NICE; /* 120, squash fair */
167 }
168
169 /*
170 * l(a,b)
171 * le(a,b) := !l(b,a)
172 * g(a,b) := l(b,a)
173 * ge(a,b) := !l(a,b)
174 */
175
176 /* real prio, less is less */
prio_less(struct task_struct * a,struct task_struct * b,bool in_fi)177 static inline bool prio_less(struct task_struct *a, struct task_struct *b, bool in_fi)
178 {
179
180 int pa = __task_prio(a), pb = __task_prio(b);
181
182 if (-pa < -pb)
183 return true;
184
185 if (-pb < -pa)
186 return false;
187
188 if (pa == -1) /* dl_prio() doesn't work because of stop_class above */
189 return !dl_time_before(a->dl.deadline, b->dl.deadline);
190
191 if (pa == MAX_RT_PRIO + MAX_NICE) /* fair */
192 return cfs_prio_less(a, b, in_fi);
193
194 return false;
195 }
196
__sched_core_less(struct task_struct * a,struct task_struct * b)197 static inline bool __sched_core_less(struct task_struct *a, struct task_struct *b)
198 {
199 if (a->core_cookie < b->core_cookie)
200 return true;
201
202 if (a->core_cookie > b->core_cookie)
203 return false;
204
205 /* flip prio, so high prio is leftmost */
206 if (prio_less(b, a, !!task_rq(a)->core->core_forceidle_count))
207 return true;
208
209 return false;
210 }
211
212 #define __node_2_sc(node) rb_entry((node), struct task_struct, core_node)
213
rb_sched_core_less(struct rb_node * a,const struct rb_node * b)214 static inline bool rb_sched_core_less(struct rb_node *a, const struct rb_node *b)
215 {
216 return __sched_core_less(__node_2_sc(a), __node_2_sc(b));
217 }
218
rb_sched_core_cmp(const void * key,const struct rb_node * node)219 static inline int rb_sched_core_cmp(const void *key, const struct rb_node *node)
220 {
221 const struct task_struct *p = __node_2_sc(node);
222 unsigned long cookie = (unsigned long)key;
223
224 if (cookie < p->core_cookie)
225 return -1;
226
227 if (cookie > p->core_cookie)
228 return 1;
229
230 return 0;
231 }
232
sched_core_enqueue(struct rq * rq,struct task_struct * p)233 void sched_core_enqueue(struct rq *rq, struct task_struct *p)
234 {
235 rq->core->core_task_seq++;
236
237 if (!p->core_cookie)
238 return;
239
240 rb_add(&p->core_node, &rq->core_tree, rb_sched_core_less);
241 }
242
sched_core_dequeue(struct rq * rq,struct task_struct * p,int flags)243 void sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags)
244 {
245 rq->core->core_task_seq++;
246
247 if (sched_core_enqueued(p)) {
248 rb_erase(&p->core_node, &rq->core_tree);
249 RB_CLEAR_NODE(&p->core_node);
250 }
251
252 /*
253 * Migrating the last task off the cpu, with the cpu in forced idle
254 * state. Reschedule to create an accounting edge for forced idle,
255 * and re-examine whether the core is still in forced idle state.
256 */
257 if (!(flags & DEQUEUE_SAVE) && rq->nr_running == 1 &&
258 rq->core->core_forceidle_count && rq->curr == rq->idle)
259 resched_curr(rq);
260 }
261
262 /*
263 * Find left-most (aka, highest priority) task matching @cookie.
264 */
sched_core_find(struct rq * rq,unsigned long cookie)265 static struct task_struct *sched_core_find(struct rq *rq, unsigned long cookie)
266 {
267 struct rb_node *node;
268
269 node = rb_find_first((void *)cookie, &rq->core_tree, rb_sched_core_cmp);
270 /*
271 * The idle task always matches any cookie!
272 */
273 if (!node)
274 return idle_sched_class.pick_task(rq);
275
276 return __node_2_sc(node);
277 }
278
sched_core_next(struct task_struct * p,unsigned long cookie)279 static struct task_struct *sched_core_next(struct task_struct *p, unsigned long cookie)
280 {
281 struct rb_node *node = &p->core_node;
282
283 node = rb_next(node);
284 if (!node)
285 return NULL;
286
287 p = container_of(node, struct task_struct, core_node);
288 if (p->core_cookie != cookie)
289 return NULL;
290
291 return p;
292 }
293
294 /*
295 * Magic required such that:
296 *
297 * raw_spin_rq_lock(rq);
298 * ...
299 * raw_spin_rq_unlock(rq);
300 *
301 * ends up locking and unlocking the _same_ lock, and all CPUs
302 * always agree on what rq has what lock.
303 *
304 * XXX entirely possible to selectively enable cores, don't bother for now.
305 */
306
307 static DEFINE_MUTEX(sched_core_mutex);
308 static atomic_t sched_core_count;
309 static struct cpumask sched_core_mask;
310
sched_core_lock(int cpu,unsigned long * flags)311 static void sched_core_lock(int cpu, unsigned long *flags)
312 {
313 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
314 int t, i = 0;
315
316 local_irq_save(*flags);
317 for_each_cpu(t, smt_mask)
318 raw_spin_lock_nested(&cpu_rq(t)->__lock, i++);
319 }
320
sched_core_unlock(int cpu,unsigned long * flags)321 static void sched_core_unlock(int cpu, unsigned long *flags)
322 {
323 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
324 int t;
325
326 for_each_cpu(t, smt_mask)
327 raw_spin_unlock(&cpu_rq(t)->__lock);
328 local_irq_restore(*flags);
329 }
330
__sched_core_flip(bool enabled)331 static void __sched_core_flip(bool enabled)
332 {
333 unsigned long flags;
334 int cpu, t;
335
336 cpus_read_lock();
337
338 /*
339 * Toggle the online cores, one by one.
340 */
341 cpumask_copy(&sched_core_mask, cpu_online_mask);
342 for_each_cpu(cpu, &sched_core_mask) {
343 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
344
345 sched_core_lock(cpu, &flags);
346
347 for_each_cpu(t, smt_mask)
348 cpu_rq(t)->core_enabled = enabled;
349
350 cpu_rq(cpu)->core->core_forceidle_start = 0;
351
352 sched_core_unlock(cpu, &flags);
353
354 cpumask_andnot(&sched_core_mask, &sched_core_mask, smt_mask);
355 }
356
357 /*
358 * Toggle the offline CPUs.
359 */
360 for_each_cpu_andnot(cpu, cpu_possible_mask, cpu_online_mask)
361 cpu_rq(cpu)->core_enabled = enabled;
362
363 cpus_read_unlock();
364 }
365
sched_core_assert_empty(void)366 static void sched_core_assert_empty(void)
367 {
368 int cpu;
369
370 for_each_possible_cpu(cpu)
371 WARN_ON_ONCE(!RB_EMPTY_ROOT(&cpu_rq(cpu)->core_tree));
372 }
373
__sched_core_enable(void)374 static void __sched_core_enable(void)
375 {
376 static_branch_enable(&__sched_core_enabled);
377 /*
378 * Ensure all previous instances of raw_spin_rq_*lock() have finished
379 * and future ones will observe !sched_core_disabled().
380 */
381 synchronize_rcu();
382 __sched_core_flip(true);
383 sched_core_assert_empty();
384 }
385
__sched_core_disable(void)386 static void __sched_core_disable(void)
387 {
388 sched_core_assert_empty();
389 __sched_core_flip(false);
390 static_branch_disable(&__sched_core_enabled);
391 }
392
sched_core_get(void)393 void sched_core_get(void)
394 {
395 if (atomic_inc_not_zero(&sched_core_count))
396 return;
397
398 mutex_lock(&sched_core_mutex);
399 if (!atomic_read(&sched_core_count))
400 __sched_core_enable();
401
402 smp_mb__before_atomic();
403 atomic_inc(&sched_core_count);
404 mutex_unlock(&sched_core_mutex);
405 }
406
__sched_core_put(struct work_struct * work)407 static void __sched_core_put(struct work_struct *work)
408 {
409 if (atomic_dec_and_mutex_lock(&sched_core_count, &sched_core_mutex)) {
410 __sched_core_disable();
411 mutex_unlock(&sched_core_mutex);
412 }
413 }
414
sched_core_put(void)415 void sched_core_put(void)
416 {
417 static DECLARE_WORK(_work, __sched_core_put);
418
419 /*
420 * "There can be only one"
421 *
422 * Either this is the last one, or we don't actually need to do any
423 * 'work'. If it is the last *again*, we rely on
424 * WORK_STRUCT_PENDING_BIT.
425 */
426 if (!atomic_add_unless(&sched_core_count, -1, 1))
427 schedule_work(&_work);
428 }
429
430 #else /* !CONFIG_SCHED_CORE */
431
sched_core_enqueue(struct rq * rq,struct task_struct * p)432 static inline void sched_core_enqueue(struct rq *rq, struct task_struct *p) { }
433 static inline void
sched_core_dequeue(struct rq * rq,struct task_struct * p,int flags)434 sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) { }
435
436 #endif /* CONFIG_SCHED_CORE */
437
438 /*
439 * Serialization rules:
440 *
441 * Lock order:
442 *
443 * p->pi_lock
444 * rq->lock
445 * hrtimer_cpu_base->lock (hrtimer_start() for bandwidth controls)
446 *
447 * rq1->lock
448 * rq2->lock where: rq1 < rq2
449 *
450 * Regular state:
451 *
452 * Normal scheduling state is serialized by rq->lock. __schedule() takes the
453 * local CPU's rq->lock, it optionally removes the task from the runqueue and
454 * always looks at the local rq data structures to find the most eligible task
455 * to run next.
456 *
457 * Task enqueue is also under rq->lock, possibly taken from another CPU.
458 * Wakeups from another LLC domain might use an IPI to transfer the enqueue to
459 * the local CPU to avoid bouncing the runqueue state around [ see
460 * ttwu_queue_wakelist() ]
461 *
462 * Task wakeup, specifically wakeups that involve migration, are horribly
463 * complicated to avoid having to take two rq->locks.
464 *
465 * Special state:
466 *
467 * System-calls and anything external will use task_rq_lock() which acquires
468 * both p->pi_lock and rq->lock. As a consequence the state they change is
469 * stable while holding either lock:
470 *
471 * - sched_setaffinity()/
472 * set_cpus_allowed_ptr(): p->cpus_ptr, p->nr_cpus_allowed
473 * - set_user_nice(): p->se.load, p->*prio
474 * - __sched_setscheduler(): p->sched_class, p->policy, p->*prio,
475 * p->se.load, p->rt_priority,
476 * p->dl.dl_{runtime, deadline, period, flags, bw, density}
477 * - sched_setnuma(): p->numa_preferred_nid
478 * - sched_move_task(): p->sched_task_group
479 * - uclamp_update_active() p->uclamp*
480 *
481 * p->state <- TASK_*:
482 *
483 * is changed locklessly using set_current_state(), __set_current_state() or
484 * set_special_state(), see their respective comments, or by
485 * try_to_wake_up(). This latter uses p->pi_lock to serialize against
486 * concurrent self.
487 *
488 * p->on_rq <- { 0, 1 = TASK_ON_RQ_QUEUED, 2 = TASK_ON_RQ_MIGRATING }:
489 *
490 * is set by activate_task() and cleared by deactivate_task(), under
491 * rq->lock. Non-zero indicates the task is runnable, the special
492 * ON_RQ_MIGRATING state is used for migration without holding both
493 * rq->locks. It indicates task_cpu() is not stable, see task_rq_lock().
494 *
495 * p->on_cpu <- { 0, 1 }:
496 *
497 * is set by prepare_task() and cleared by finish_task() such that it will be
498 * set before p is scheduled-in and cleared after p is scheduled-out, both
499 * under rq->lock. Non-zero indicates the task is running on its CPU.
500 *
501 * [ The astute reader will observe that it is possible for two tasks on one
502 * CPU to have ->on_cpu = 1 at the same time. ]
503 *
504 * task_cpu(p): is changed by set_task_cpu(), the rules are:
505 *
506 * - Don't call set_task_cpu() on a blocked task:
507 *
508 * We don't care what CPU we're not running on, this simplifies hotplug,
509 * the CPU assignment of blocked tasks isn't required to be valid.
510 *
511 * - for try_to_wake_up(), called under p->pi_lock:
512 *
513 * This allows try_to_wake_up() to only take one rq->lock, see its comment.
514 *
515 * - for migration called under rq->lock:
516 * [ see task_on_rq_migrating() in task_rq_lock() ]
517 *
518 * o move_queued_task()
519 * o detach_task()
520 *
521 * - for migration called under double_rq_lock():
522 *
523 * o __migrate_swap_task()
524 * o push_rt_task() / pull_rt_task()
525 * o push_dl_task() / pull_dl_task()
526 * o dl_task_offline_migration()
527 *
528 */
529
raw_spin_rq_lock_nested(struct rq * rq,int subclass)530 void raw_spin_rq_lock_nested(struct rq *rq, int subclass)
531 {
532 raw_spinlock_t *lock;
533
534 /* Matches synchronize_rcu() in __sched_core_enable() */
535 preempt_disable();
536 if (sched_core_disabled()) {
537 raw_spin_lock_nested(&rq->__lock, subclass);
538 /* preempt_count *MUST* be > 1 */
539 preempt_enable_no_resched();
540 return;
541 }
542
543 for (;;) {
544 lock = __rq_lockp(rq);
545 raw_spin_lock_nested(lock, subclass);
546 if (likely(lock == __rq_lockp(rq))) {
547 /* preempt_count *MUST* be > 1 */
548 preempt_enable_no_resched();
549 return;
550 }
551 raw_spin_unlock(lock);
552 }
553 }
554
raw_spin_rq_trylock(struct rq * rq)555 bool raw_spin_rq_trylock(struct rq *rq)
556 {
557 raw_spinlock_t *lock;
558 bool ret;
559
560 /* Matches synchronize_rcu() in __sched_core_enable() */
561 preempt_disable();
562 if (sched_core_disabled()) {
563 ret = raw_spin_trylock(&rq->__lock);
564 preempt_enable();
565 return ret;
566 }
567
568 for (;;) {
569 lock = __rq_lockp(rq);
570 ret = raw_spin_trylock(lock);
571 if (!ret || (likely(lock == __rq_lockp(rq)))) {
572 preempt_enable();
573 return ret;
574 }
575 raw_spin_unlock(lock);
576 }
577 }
578
raw_spin_rq_unlock(struct rq * rq)579 void raw_spin_rq_unlock(struct rq *rq)
580 {
581 raw_spin_unlock(rq_lockp(rq));
582 }
583
584 #ifdef CONFIG_SMP
585 /*
586 * double_rq_lock - safely lock two runqueues
587 */
double_rq_lock(struct rq * rq1,struct rq * rq2)588 void double_rq_lock(struct rq *rq1, struct rq *rq2)
589 {
590 lockdep_assert_irqs_disabled();
591
592 if (rq_order_less(rq2, rq1))
593 swap(rq1, rq2);
594
595 raw_spin_rq_lock(rq1);
596 if (__rq_lockp(rq1) != __rq_lockp(rq2))
597 raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING);
598
599 double_rq_clock_clear_update(rq1, rq2);
600 }
601 #endif
602
603 /*
604 * __task_rq_lock - lock the rq @p resides on.
605 */
__task_rq_lock(struct task_struct * p,struct rq_flags * rf)606 struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
607 __acquires(rq->lock)
608 {
609 struct rq *rq;
610
611 lockdep_assert_held(&p->pi_lock);
612
613 for (;;) {
614 rq = task_rq(p);
615 raw_spin_rq_lock(rq);
616 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
617 rq_pin_lock(rq, rf);
618 return rq;
619 }
620 raw_spin_rq_unlock(rq);
621
622 while (unlikely(task_on_rq_migrating(p)))
623 cpu_relax();
624 }
625 }
626
627 /*
628 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
629 */
task_rq_lock(struct task_struct * p,struct rq_flags * rf)630 struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
631 __acquires(p->pi_lock)
632 __acquires(rq->lock)
633 {
634 struct rq *rq;
635
636 for (;;) {
637 raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
638 rq = task_rq(p);
639 raw_spin_rq_lock(rq);
640 /*
641 * move_queued_task() task_rq_lock()
642 *
643 * ACQUIRE (rq->lock)
644 * [S] ->on_rq = MIGRATING [L] rq = task_rq()
645 * WMB (__set_task_cpu()) ACQUIRE (rq->lock);
646 * [S] ->cpu = new_cpu [L] task_rq()
647 * [L] ->on_rq
648 * RELEASE (rq->lock)
649 *
650 * If we observe the old CPU in task_rq_lock(), the acquire of
651 * the old rq->lock will fully serialize against the stores.
652 *
653 * If we observe the new CPU in task_rq_lock(), the address
654 * dependency headed by '[L] rq = task_rq()' and the acquire
655 * will pair with the WMB to ensure we then also see migrating.
656 */
657 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
658 rq_pin_lock(rq, rf);
659 return rq;
660 }
661 raw_spin_rq_unlock(rq);
662 raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
663
664 while (unlikely(task_on_rq_migrating(p)))
665 cpu_relax();
666 }
667 }
668
669 /*
670 * RQ-clock updating methods:
671 */
672
update_rq_clock_task(struct rq * rq,s64 delta)673 static void update_rq_clock_task(struct rq *rq, s64 delta)
674 {
675 /*
676 * In theory, the compile should just see 0 here, and optimize out the call
677 * to sched_rt_avg_update. But I don't trust it...
678 */
679 s64 __maybe_unused steal = 0, irq_delta = 0;
680
681 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
682 irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
683
684 /*
685 * Since irq_time is only updated on {soft,}irq_exit, we might run into
686 * this case when a previous update_rq_clock() happened inside a
687 * {soft,}irq region.
688 *
689 * When this happens, we stop ->clock_task and only update the
690 * prev_irq_time stamp to account for the part that fit, so that a next
691 * update will consume the rest. This ensures ->clock_task is
692 * monotonic.
693 *
694 * It does however cause some slight miss-attribution of {soft,}irq
695 * time, a more accurate solution would be to update the irq_time using
696 * the current rq->clock timestamp, except that would require using
697 * atomic ops.
698 */
699 if (irq_delta > delta)
700 irq_delta = delta;
701
702 rq->prev_irq_time += irq_delta;
703 delta -= irq_delta;
704 psi_account_irqtime(rq->curr, irq_delta);
705 #endif
706 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
707 if (static_key_false((¶virt_steal_rq_enabled))) {
708 steal = paravirt_steal_clock(cpu_of(rq));
709 steal -= rq->prev_steal_time_rq;
710
711 if (unlikely(steal > delta))
712 steal = delta;
713
714 rq->prev_steal_time_rq += steal;
715 delta -= steal;
716 }
717 #endif
718
719 rq->clock_task += delta;
720
721 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
722 if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
723 update_irq_load_avg(rq, irq_delta + steal);
724 #endif
725 update_rq_clock_pelt(rq, delta);
726 }
727
update_rq_clock(struct rq * rq)728 void update_rq_clock(struct rq *rq)
729 {
730 s64 delta;
731
732 lockdep_assert_rq_held(rq);
733
734 if (rq->clock_update_flags & RQCF_ACT_SKIP)
735 return;
736
737 #ifdef CONFIG_SCHED_DEBUG
738 if (sched_feat(WARN_DOUBLE_CLOCK))
739 SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED);
740 rq->clock_update_flags |= RQCF_UPDATED;
741 #endif
742
743 delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
744 if (delta < 0)
745 return;
746 rq->clock += delta;
747 update_rq_clock_task(rq, delta);
748 }
749
750 #ifdef CONFIG_SCHED_HRTICK
751 /*
752 * Use HR-timers to deliver accurate preemption points.
753 */
754
hrtick_clear(struct rq * rq)755 static void hrtick_clear(struct rq *rq)
756 {
757 if (hrtimer_active(&rq->hrtick_timer))
758 hrtimer_cancel(&rq->hrtick_timer);
759 }
760
761 /*
762 * High-resolution timer tick.
763 * Runs from hardirq context with interrupts disabled.
764 */
hrtick(struct hrtimer * timer)765 static enum hrtimer_restart hrtick(struct hrtimer *timer)
766 {
767 struct rq *rq = container_of(timer, struct rq, hrtick_timer);
768 struct rq_flags rf;
769
770 WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
771
772 rq_lock(rq, &rf);
773 update_rq_clock(rq);
774 rq->curr->sched_class->task_tick(rq, rq->curr, 1);
775 rq_unlock(rq, &rf);
776
777 return HRTIMER_NORESTART;
778 }
779
780 #ifdef CONFIG_SMP
781
__hrtick_restart(struct rq * rq)782 static void __hrtick_restart(struct rq *rq)
783 {
784 struct hrtimer *timer = &rq->hrtick_timer;
785 ktime_t time = rq->hrtick_time;
786
787 hrtimer_start(timer, time, HRTIMER_MODE_ABS_PINNED_HARD);
788 }
789
790 /*
791 * called from hardirq (IPI) context
792 */
__hrtick_start(void * arg)793 static void __hrtick_start(void *arg)
794 {
795 struct rq *rq = arg;
796 struct rq_flags rf;
797
798 rq_lock(rq, &rf);
799 __hrtick_restart(rq);
800 rq_unlock(rq, &rf);
801 }
802
803 /*
804 * Called to set the hrtick timer state.
805 *
806 * called with rq->lock held and irqs disabled
807 */
hrtick_start(struct rq * rq,u64 delay)808 void hrtick_start(struct rq *rq, u64 delay)
809 {
810 struct hrtimer *timer = &rq->hrtick_timer;
811 s64 delta;
812
813 /*
814 * Don't schedule slices shorter than 10000ns, that just
815 * doesn't make sense and can cause timer DoS.
816 */
817 delta = max_t(s64, delay, 10000LL);
818 rq->hrtick_time = ktime_add_ns(timer->base->get_time(), delta);
819
820 if (rq == this_rq())
821 __hrtick_restart(rq);
822 else
823 smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
824 }
825
826 #else
827 /*
828 * Called to set the hrtick timer state.
829 *
830 * called with rq->lock held and irqs disabled
831 */
hrtick_start(struct rq * rq,u64 delay)832 void hrtick_start(struct rq *rq, u64 delay)
833 {
834 /*
835 * Don't schedule slices shorter than 10000ns, that just
836 * doesn't make sense. Rely on vruntime for fairness.
837 */
838 delay = max_t(u64, delay, 10000LL);
839 hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
840 HRTIMER_MODE_REL_PINNED_HARD);
841 }
842
843 #endif /* CONFIG_SMP */
844
hrtick_rq_init(struct rq * rq)845 static void hrtick_rq_init(struct rq *rq)
846 {
847 #ifdef CONFIG_SMP
848 INIT_CSD(&rq->hrtick_csd, __hrtick_start, rq);
849 #endif
850 hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
851 rq->hrtick_timer.function = hrtick;
852 }
853 #else /* CONFIG_SCHED_HRTICK */
hrtick_clear(struct rq * rq)854 static inline void hrtick_clear(struct rq *rq)
855 {
856 }
857
hrtick_rq_init(struct rq * rq)858 static inline void hrtick_rq_init(struct rq *rq)
859 {
860 }
861 #endif /* CONFIG_SCHED_HRTICK */
862
863 /*
864 * cmpxchg based fetch_or, macro so it works for different integer types
865 */
866 #define fetch_or(ptr, mask) \
867 ({ \
868 typeof(ptr) _ptr = (ptr); \
869 typeof(mask) _mask = (mask); \
870 typeof(*_ptr) _val = *_ptr; \
871 \
872 do { \
873 } while (!try_cmpxchg(_ptr, &_val, _val | _mask)); \
874 _val; \
875 })
876
877 #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
878 /*
879 * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
880 * this avoids any races wrt polling state changes and thereby avoids
881 * spurious IPIs.
882 */
set_nr_and_not_polling(struct task_struct * p)883 static inline bool set_nr_and_not_polling(struct task_struct *p)
884 {
885 struct thread_info *ti = task_thread_info(p);
886 return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
887 }
888
889 /*
890 * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
891 *
892 * If this returns true, then the idle task promises to call
893 * sched_ttwu_pending() and reschedule soon.
894 */
set_nr_if_polling(struct task_struct * p)895 static bool set_nr_if_polling(struct task_struct *p)
896 {
897 struct thread_info *ti = task_thread_info(p);
898 typeof(ti->flags) val = READ_ONCE(ti->flags);
899
900 for (;;) {
901 if (!(val & _TIF_POLLING_NRFLAG))
902 return false;
903 if (val & _TIF_NEED_RESCHED)
904 return true;
905 if (try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED))
906 break;
907 }
908 return true;
909 }
910
911 #else
set_nr_and_not_polling(struct task_struct * p)912 static inline bool set_nr_and_not_polling(struct task_struct *p)
913 {
914 set_tsk_need_resched(p);
915 return true;
916 }
917
918 #ifdef CONFIG_SMP
set_nr_if_polling(struct task_struct * p)919 static inline bool set_nr_if_polling(struct task_struct *p)
920 {
921 return false;
922 }
923 #endif
924 #endif
925
__wake_q_add(struct wake_q_head * head,struct task_struct * task)926 static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task)
927 {
928 struct wake_q_node *node = &task->wake_q;
929
930 /*
931 * Atomically grab the task, if ->wake_q is !nil already it means
932 * it's already queued (either by us or someone else) and will get the
933 * wakeup due to that.
934 *
935 * In order to ensure that a pending wakeup will observe our pending
936 * state, even in the failed case, an explicit smp_mb() must be used.
937 */
938 smp_mb__before_atomic();
939 if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL)))
940 return false;
941
942 /*
943 * The head is context local, there can be no concurrency.
944 */
945 *head->lastp = node;
946 head->lastp = &node->next;
947 return true;
948 }
949
950 /**
951 * wake_q_add() - queue a wakeup for 'later' waking.
952 * @head: the wake_q_head to add @task to
953 * @task: the task to queue for 'later' wakeup
954 *
955 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
956 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
957 * instantly.
958 *
959 * This function must be used as-if it were wake_up_process(); IOW the task
960 * must be ready to be woken at this location.
961 */
wake_q_add(struct wake_q_head * head,struct task_struct * task)962 void wake_q_add(struct wake_q_head *head, struct task_struct *task)
963 {
964 if (__wake_q_add(head, task))
965 get_task_struct(task);
966 }
967
968 /**
969 * wake_q_add_safe() - safely queue a wakeup for 'later' waking.
970 * @head: the wake_q_head to add @task to
971 * @task: the task to queue for 'later' wakeup
972 *
973 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
974 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
975 * instantly.
976 *
977 * This function must be used as-if it were wake_up_process(); IOW the task
978 * must be ready to be woken at this location.
979 *
980 * This function is essentially a task-safe equivalent to wake_q_add(). Callers
981 * that already hold reference to @task can call the 'safe' version and trust
982 * wake_q to do the right thing depending whether or not the @task is already
983 * queued for wakeup.
984 */
wake_q_add_safe(struct wake_q_head * head,struct task_struct * task)985 void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task)
986 {
987 if (!__wake_q_add(head, task))
988 put_task_struct(task);
989 }
990
wake_up_q(struct wake_q_head * head)991 void wake_up_q(struct wake_q_head *head)
992 {
993 struct wake_q_node *node = head->first;
994
995 while (node != WAKE_Q_TAIL) {
996 struct task_struct *task;
997
998 task = container_of(node, struct task_struct, wake_q);
999 /* Task can safely be re-inserted now: */
1000 node = node->next;
1001 task->wake_q.next = NULL;
1002
1003 /*
1004 * wake_up_process() executes a full barrier, which pairs with
1005 * the queueing in wake_q_add() so as not to miss wakeups.
1006 */
1007 wake_up_process(task);
1008 put_task_struct(task);
1009 }
1010 }
1011
1012 /*
1013 * resched_curr - mark rq's current task 'to be rescheduled now'.
1014 *
1015 * On UP this means the setting of the need_resched flag, on SMP it
1016 * might also involve a cross-CPU call to trigger the scheduler on
1017 * the target CPU.
1018 */
resched_curr(struct rq * rq)1019 void resched_curr(struct rq *rq)
1020 {
1021 struct task_struct *curr = rq->curr;
1022 int cpu;
1023
1024 lockdep_assert_rq_held(rq);
1025
1026 if (test_tsk_need_resched(curr))
1027 return;
1028
1029 cpu = cpu_of(rq);
1030
1031 if (cpu == smp_processor_id()) {
1032 set_tsk_need_resched(curr);
1033 set_preempt_need_resched();
1034 return;
1035 }
1036
1037 if (set_nr_and_not_polling(curr))
1038 smp_send_reschedule(cpu);
1039 else
1040 trace_sched_wake_idle_without_ipi(cpu);
1041 }
1042
resched_cpu(int cpu)1043 void resched_cpu(int cpu)
1044 {
1045 struct rq *rq = cpu_rq(cpu);
1046 unsigned long flags;
1047
1048 raw_spin_rq_lock_irqsave(rq, flags);
1049 if (cpu_online(cpu) || cpu == smp_processor_id())
1050 resched_curr(rq);
1051 raw_spin_rq_unlock_irqrestore(rq, flags);
1052 }
1053
1054 #ifdef CONFIG_SMP
1055 #ifdef CONFIG_NO_HZ_COMMON
1056 /*
1057 * In the semi idle case, use the nearest busy CPU for migrating timers
1058 * from an idle CPU. This is good for power-savings.
1059 *
1060 * We don't do similar optimization for completely idle system, as
1061 * selecting an idle CPU will add more delays to the timers than intended
1062 * (as that CPU's timer base may not be uptodate wrt jiffies etc).
1063 */
get_nohz_timer_target(void)1064 int get_nohz_timer_target(void)
1065 {
1066 int i, cpu = smp_processor_id(), default_cpu = -1;
1067 struct sched_domain *sd;
1068 const struct cpumask *hk_mask;
1069
1070 if (housekeeping_cpu(cpu, HK_TYPE_TIMER)) {
1071 if (!idle_cpu(cpu))
1072 return cpu;
1073 default_cpu = cpu;
1074 }
1075
1076 hk_mask = housekeeping_cpumask(HK_TYPE_TIMER);
1077
1078 rcu_read_lock();
1079 for_each_domain(cpu, sd) {
1080 for_each_cpu_and(i, sched_domain_span(sd), hk_mask) {
1081 if (cpu == i)
1082 continue;
1083
1084 if (!idle_cpu(i)) {
1085 cpu = i;
1086 goto unlock;
1087 }
1088 }
1089 }
1090
1091 if (default_cpu == -1)
1092 default_cpu = housekeeping_any_cpu(HK_TYPE_TIMER);
1093 cpu = default_cpu;
1094 unlock:
1095 rcu_read_unlock();
1096 return cpu;
1097 }
1098
1099 /*
1100 * When add_timer_on() enqueues a timer into the timer wheel of an
1101 * idle CPU then this timer might expire before the next timer event
1102 * which is scheduled to wake up that CPU. In case of a completely
1103 * idle system the next event might even be infinite time into the
1104 * future. wake_up_idle_cpu() ensures that the CPU is woken up and
1105 * leaves the inner idle loop so the newly added timer is taken into
1106 * account when the CPU goes back to idle and evaluates the timer
1107 * wheel for the next timer event.
1108 */
wake_up_idle_cpu(int cpu)1109 static void wake_up_idle_cpu(int cpu)
1110 {
1111 struct rq *rq = cpu_rq(cpu);
1112
1113 if (cpu == smp_processor_id())
1114 return;
1115
1116 if (set_nr_and_not_polling(rq->idle))
1117 smp_send_reschedule(cpu);
1118 else
1119 trace_sched_wake_idle_without_ipi(cpu);
1120 }
1121
wake_up_full_nohz_cpu(int cpu)1122 static bool wake_up_full_nohz_cpu(int cpu)
1123 {
1124 /*
1125 * We just need the target to call irq_exit() and re-evaluate
1126 * the next tick. The nohz full kick at least implies that.
1127 * If needed we can still optimize that later with an
1128 * empty IRQ.
1129 */
1130 if (cpu_is_offline(cpu))
1131 return true; /* Don't try to wake offline CPUs. */
1132 if (tick_nohz_full_cpu(cpu)) {
1133 if (cpu != smp_processor_id() ||
1134 tick_nohz_tick_stopped())
1135 tick_nohz_full_kick_cpu(cpu);
1136 return true;
1137 }
1138
1139 return false;
1140 }
1141
1142 /*
1143 * Wake up the specified CPU. If the CPU is going offline, it is the
1144 * caller's responsibility to deal with the lost wakeup, for example,
1145 * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
1146 */
wake_up_nohz_cpu(int cpu)1147 void wake_up_nohz_cpu(int cpu)
1148 {
1149 if (!wake_up_full_nohz_cpu(cpu))
1150 wake_up_idle_cpu(cpu);
1151 }
1152
nohz_csd_func(void * info)1153 static void nohz_csd_func(void *info)
1154 {
1155 struct rq *rq = info;
1156 int cpu = cpu_of(rq);
1157 unsigned int flags;
1158
1159 /*
1160 * Release the rq::nohz_csd.
1161 */
1162 flags = atomic_fetch_andnot(NOHZ_KICK_MASK | NOHZ_NEWILB_KICK, nohz_flags(cpu));
1163 WARN_ON(!(flags & NOHZ_KICK_MASK));
1164
1165 rq->idle_balance = idle_cpu(cpu);
1166 if (rq->idle_balance && !need_resched()) {
1167 rq->nohz_idle_balance = flags;
1168 raise_softirq_irqoff(SCHED_SOFTIRQ);
1169 }
1170 }
1171
1172 #endif /* CONFIG_NO_HZ_COMMON */
1173
1174 #ifdef CONFIG_NO_HZ_FULL
sched_can_stop_tick(struct rq * rq)1175 bool sched_can_stop_tick(struct rq *rq)
1176 {
1177 int fifo_nr_running;
1178
1179 /* Deadline tasks, even if single, need the tick */
1180 if (rq->dl.dl_nr_running)
1181 return false;
1182
1183 /*
1184 * If there are more than one RR tasks, we need the tick to affect the
1185 * actual RR behaviour.
1186 */
1187 if (rq->rt.rr_nr_running) {
1188 if (rq->rt.rr_nr_running == 1)
1189 return true;
1190 else
1191 return false;
1192 }
1193
1194 /*
1195 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
1196 * forced preemption between FIFO tasks.
1197 */
1198 fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
1199 if (fifo_nr_running)
1200 return true;
1201
1202 /*
1203 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
1204 * if there's more than one we need the tick for involuntary
1205 * preemption.
1206 */
1207 if (rq->nr_running > 1)
1208 return false;
1209
1210 return true;
1211 }
1212 #endif /* CONFIG_NO_HZ_FULL */
1213 #endif /* CONFIG_SMP */
1214
1215 #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
1216 (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
1217 /*
1218 * Iterate task_group tree rooted at *from, calling @down when first entering a
1219 * node and @up when leaving it for the final time.
1220 *
1221 * Caller must hold rcu_lock or sufficient equivalent.
1222 */
walk_tg_tree_from(struct task_group * from,tg_visitor down,tg_visitor up,void * data)1223 int walk_tg_tree_from(struct task_group *from,
1224 tg_visitor down, tg_visitor up, void *data)
1225 {
1226 struct task_group *parent, *child;
1227 int ret;
1228
1229 parent = from;
1230
1231 down:
1232 ret = (*down)(parent, data);
1233 if (ret)
1234 goto out;
1235 list_for_each_entry_rcu(child, &parent->children, siblings) {
1236 parent = child;
1237 goto down;
1238
1239 up:
1240 continue;
1241 }
1242 ret = (*up)(parent, data);
1243 if (ret || parent == from)
1244 goto out;
1245
1246 child = parent;
1247 parent = parent->parent;
1248 if (parent)
1249 goto up;
1250 out:
1251 return ret;
1252 }
1253
tg_nop(struct task_group * tg,void * data)1254 int tg_nop(struct task_group *tg, void *data)
1255 {
1256 return 0;
1257 }
1258 #endif
1259
set_load_weight(struct task_struct * p,bool update_load)1260 static void set_load_weight(struct task_struct *p, bool update_load)
1261 {
1262 int prio = p->static_prio - MAX_RT_PRIO;
1263 struct load_weight *load = &p->se.load;
1264
1265 /*
1266 * SCHED_IDLE tasks get minimal weight:
1267 */
1268 if (task_has_idle_policy(p)) {
1269 load->weight = scale_load(WEIGHT_IDLEPRIO);
1270 load->inv_weight = WMULT_IDLEPRIO;
1271 return;
1272 }
1273
1274 /*
1275 * SCHED_OTHER tasks have to update their load when changing their
1276 * weight
1277 */
1278 if (update_load && p->sched_class == &fair_sched_class) {
1279 reweight_task(p, prio);
1280 } else {
1281 load->weight = scale_load(sched_prio_to_weight[prio]);
1282 load->inv_weight = sched_prio_to_wmult[prio];
1283 }
1284 }
1285
1286 #ifdef CONFIG_UCLAMP_TASK
1287 /*
1288 * Serializes updates of utilization clamp values
1289 *
1290 * The (slow-path) user-space triggers utilization clamp value updates which
1291 * can require updates on (fast-path) scheduler's data structures used to
1292 * support enqueue/dequeue operations.
1293 * While the per-CPU rq lock protects fast-path update operations, user-space
1294 * requests are serialized using a mutex to reduce the risk of conflicting
1295 * updates or API abuses.
1296 */
1297 static DEFINE_MUTEX(uclamp_mutex);
1298
1299 /* Max allowed minimum utilization */
1300 static unsigned int __maybe_unused sysctl_sched_uclamp_util_min = SCHED_CAPACITY_SCALE;
1301
1302 /* Max allowed maximum utilization */
1303 static unsigned int __maybe_unused sysctl_sched_uclamp_util_max = SCHED_CAPACITY_SCALE;
1304
1305 /*
1306 * By default RT tasks run at the maximum performance point/capacity of the
1307 * system. Uclamp enforces this by always setting UCLAMP_MIN of RT tasks to
1308 * SCHED_CAPACITY_SCALE.
1309 *
1310 * This knob allows admins to change the default behavior when uclamp is being
1311 * used. In battery powered devices, particularly, running at the maximum
1312 * capacity and frequency will increase energy consumption and shorten the
1313 * battery life.
1314 *
1315 * This knob only affects RT tasks that their uclamp_se->user_defined == false.
1316 *
1317 * This knob will not override the system default sched_util_clamp_min defined
1318 * above.
1319 */
1320 static unsigned int sysctl_sched_uclamp_util_min_rt_default = SCHED_CAPACITY_SCALE;
1321
1322 /* All clamps are required to be less or equal than these values */
1323 static struct uclamp_se uclamp_default[UCLAMP_CNT];
1324
1325 /*
1326 * This static key is used to reduce the uclamp overhead in the fast path. It
1327 * primarily disables the call to uclamp_rq_{inc, dec}() in
1328 * enqueue/dequeue_task().
1329 *
1330 * This allows users to continue to enable uclamp in their kernel config with
1331 * minimum uclamp overhead in the fast path.
1332 *
1333 * As soon as userspace modifies any of the uclamp knobs, the static key is
1334 * enabled, since we have an actual users that make use of uclamp
1335 * functionality.
1336 *
1337 * The knobs that would enable this static key are:
1338 *
1339 * * A task modifying its uclamp value with sched_setattr().
1340 * * An admin modifying the sysctl_sched_uclamp_{min, max} via procfs.
1341 * * An admin modifying the cgroup cpu.uclamp.{min, max}
1342 */
1343 DEFINE_STATIC_KEY_FALSE(sched_uclamp_used);
1344
1345 /* Integer rounded range for each bucket */
1346 #define UCLAMP_BUCKET_DELTA DIV_ROUND_CLOSEST(SCHED_CAPACITY_SCALE, UCLAMP_BUCKETS)
1347
1348 #define for_each_clamp_id(clamp_id) \
1349 for ((clamp_id) = 0; (clamp_id) < UCLAMP_CNT; (clamp_id)++)
1350
uclamp_bucket_id(unsigned int clamp_value)1351 static inline unsigned int uclamp_bucket_id(unsigned int clamp_value)
1352 {
1353 return min_t(unsigned int, clamp_value / UCLAMP_BUCKET_DELTA, UCLAMP_BUCKETS - 1);
1354 }
1355
uclamp_none(enum uclamp_id clamp_id)1356 static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
1357 {
1358 if (clamp_id == UCLAMP_MIN)
1359 return 0;
1360 return SCHED_CAPACITY_SCALE;
1361 }
1362
uclamp_se_set(struct uclamp_se * uc_se,unsigned int value,bool user_defined)1363 static inline void uclamp_se_set(struct uclamp_se *uc_se,
1364 unsigned int value, bool user_defined)
1365 {
1366 uc_se->value = value;
1367 uc_se->bucket_id = uclamp_bucket_id(value);
1368 uc_se->user_defined = user_defined;
1369 }
1370
1371 static inline unsigned int
uclamp_idle_value(struct rq * rq,enum uclamp_id clamp_id,unsigned int clamp_value)1372 uclamp_idle_value(struct rq *rq, enum uclamp_id clamp_id,
1373 unsigned int clamp_value)
1374 {
1375 /*
1376 * Avoid blocked utilization pushing up the frequency when we go
1377 * idle (which drops the max-clamp) by retaining the last known
1378 * max-clamp.
1379 */
1380 if (clamp_id == UCLAMP_MAX) {
1381 rq->uclamp_flags |= UCLAMP_FLAG_IDLE;
1382 return clamp_value;
1383 }
1384
1385 return uclamp_none(UCLAMP_MIN);
1386 }
1387
uclamp_idle_reset(struct rq * rq,enum uclamp_id clamp_id,unsigned int clamp_value)1388 static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
1389 unsigned int clamp_value)
1390 {
1391 /* Reset max-clamp retention only on idle exit */
1392 if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
1393 return;
1394
1395 uclamp_rq_set(rq, clamp_id, clamp_value);
1396 }
1397
1398 static inline
uclamp_rq_max_value(struct rq * rq,enum uclamp_id clamp_id,unsigned int clamp_value)1399 unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
1400 unsigned int clamp_value)
1401 {
1402 struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket;
1403 int bucket_id = UCLAMP_BUCKETS - 1;
1404
1405 /*
1406 * Since both min and max clamps are max aggregated, find the
1407 * top most bucket with tasks in.
1408 */
1409 for ( ; bucket_id >= 0; bucket_id--) {
1410 if (!bucket[bucket_id].tasks)
1411 continue;
1412 return bucket[bucket_id].value;
1413 }
1414
1415 /* No tasks -- default clamp values */
1416 return uclamp_idle_value(rq, clamp_id, clamp_value);
1417 }
1418
__uclamp_update_util_min_rt_default(struct task_struct * p)1419 static void __uclamp_update_util_min_rt_default(struct task_struct *p)
1420 {
1421 unsigned int default_util_min;
1422 struct uclamp_se *uc_se;
1423
1424 lockdep_assert_held(&p->pi_lock);
1425
1426 uc_se = &p->uclamp_req[UCLAMP_MIN];
1427
1428 /* Only sync if user didn't override the default */
1429 if (uc_se->user_defined)
1430 return;
1431
1432 default_util_min = sysctl_sched_uclamp_util_min_rt_default;
1433 uclamp_se_set(uc_se, default_util_min, false);
1434 }
1435
uclamp_update_util_min_rt_default(struct task_struct * p)1436 static void uclamp_update_util_min_rt_default(struct task_struct *p)
1437 {
1438 struct rq_flags rf;
1439 struct rq *rq;
1440
1441 if (!rt_task(p))
1442 return;
1443
1444 /* Protect updates to p->uclamp_* */
1445 rq = task_rq_lock(p, &rf);
1446 __uclamp_update_util_min_rt_default(p);
1447 task_rq_unlock(rq, p, &rf);
1448 }
1449
1450 static inline struct uclamp_se
uclamp_tg_restrict(struct task_struct * p,enum uclamp_id clamp_id)1451 uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id)
1452 {
1453 /* Copy by value as we could modify it */
1454 struct uclamp_se uc_req = p->uclamp_req[clamp_id];
1455 #ifdef CONFIG_UCLAMP_TASK_GROUP
1456 unsigned int tg_min, tg_max, value;
1457
1458 /*
1459 * Tasks in autogroups or root task group will be
1460 * restricted by system defaults.
1461 */
1462 if (task_group_is_autogroup(task_group(p)))
1463 return uc_req;
1464 if (task_group(p) == &root_task_group)
1465 return uc_req;
1466
1467 tg_min = task_group(p)->uclamp[UCLAMP_MIN].value;
1468 tg_max = task_group(p)->uclamp[UCLAMP_MAX].value;
1469 value = uc_req.value;
1470 value = clamp(value, tg_min, tg_max);
1471 uclamp_se_set(&uc_req, value, false);
1472 #endif
1473
1474 return uc_req;
1475 }
1476
1477 /*
1478 * The effective clamp bucket index of a task depends on, by increasing
1479 * priority:
1480 * - the task specific clamp value, when explicitly requested from userspace
1481 * - the task group effective clamp value, for tasks not either in the root
1482 * group or in an autogroup
1483 * - the system default clamp value, defined by the sysadmin
1484 */
1485 static inline struct uclamp_se
uclamp_eff_get(struct task_struct * p,enum uclamp_id clamp_id)1486 uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
1487 {
1488 struct uclamp_se uc_req = uclamp_tg_restrict(p, clamp_id);
1489 struct uclamp_se uc_max = uclamp_default[clamp_id];
1490
1491 /* System default restrictions always apply */
1492 if (unlikely(uc_req.value > uc_max.value))
1493 return uc_max;
1494
1495 return uc_req;
1496 }
1497
uclamp_eff_value(struct task_struct * p,enum uclamp_id clamp_id)1498 unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
1499 {
1500 struct uclamp_se uc_eff;
1501
1502 /* Task currently refcounted: use back-annotated (effective) value */
1503 if (p->uclamp[clamp_id].active)
1504 return (unsigned long)p->uclamp[clamp_id].value;
1505
1506 uc_eff = uclamp_eff_get(p, clamp_id);
1507
1508 return (unsigned long)uc_eff.value;
1509 }
1510
1511 /*
1512 * When a task is enqueued on a rq, the clamp bucket currently defined by the
1513 * task's uclamp::bucket_id is refcounted on that rq. This also immediately
1514 * updates the rq's clamp value if required.
1515 *
1516 * Tasks can have a task-specific value requested from user-space, track
1517 * within each bucket the maximum value for tasks refcounted in it.
1518 * This "local max aggregation" allows to track the exact "requested" value
1519 * for each bucket when all its RUNNABLE tasks require the same clamp.
1520 */
uclamp_rq_inc_id(struct rq * rq,struct task_struct * p,enum uclamp_id clamp_id)1521 static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
1522 enum uclamp_id clamp_id)
1523 {
1524 struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
1525 struct uclamp_se *uc_se = &p->uclamp[clamp_id];
1526 struct uclamp_bucket *bucket;
1527
1528 lockdep_assert_rq_held(rq);
1529
1530 /* Update task effective clamp */
1531 p->uclamp[clamp_id] = uclamp_eff_get(p, clamp_id);
1532
1533 bucket = &uc_rq->bucket[uc_se->bucket_id];
1534 bucket->tasks++;
1535 uc_se->active = true;
1536
1537 uclamp_idle_reset(rq, clamp_id, uc_se->value);
1538
1539 /*
1540 * Local max aggregation: rq buckets always track the max
1541 * "requested" clamp value of its RUNNABLE tasks.
1542 */
1543 if (bucket->tasks == 1 || uc_se->value > bucket->value)
1544 bucket->value = uc_se->value;
1545
1546 if (uc_se->value > uclamp_rq_get(rq, clamp_id))
1547 uclamp_rq_set(rq, clamp_id, uc_se->value);
1548 }
1549
1550 /*
1551 * When a task is dequeued from a rq, the clamp bucket refcounted by the task
1552 * is released. If this is the last task reference counting the rq's max
1553 * active clamp value, then the rq's clamp value is updated.
1554 *
1555 * Both refcounted tasks and rq's cached clamp values are expected to be
1556 * always valid. If it's detected they are not, as defensive programming,
1557 * enforce the expected state and warn.
1558 */
uclamp_rq_dec_id(struct rq * rq,struct task_struct * p,enum uclamp_id clamp_id)1559 static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
1560 enum uclamp_id clamp_id)
1561 {
1562 struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
1563 struct uclamp_se *uc_se = &p->uclamp[clamp_id];
1564 struct uclamp_bucket *bucket;
1565 unsigned int bkt_clamp;
1566 unsigned int rq_clamp;
1567
1568 lockdep_assert_rq_held(rq);
1569
1570 /*
1571 * If sched_uclamp_used was enabled after task @p was enqueued,
1572 * we could end up with unbalanced call to uclamp_rq_dec_id().
1573 *
1574 * In this case the uc_se->active flag should be false since no uclamp
1575 * accounting was performed at enqueue time and we can just return
1576 * here.
1577 *
1578 * Need to be careful of the following enqueue/dequeue ordering
1579 * problem too
1580 *
1581 * enqueue(taskA)
1582 * // sched_uclamp_used gets enabled
1583 * enqueue(taskB)
1584 * dequeue(taskA)
1585 * // Must not decrement bucket->tasks here
1586 * dequeue(taskB)
1587 *
1588 * where we could end up with stale data in uc_se and
1589 * bucket[uc_se->bucket_id].
1590 *
1591 * The following check here eliminates the possibility of such race.
1592 */
1593 if (unlikely(!uc_se->active))
1594 return;
1595
1596 bucket = &uc_rq->bucket[uc_se->bucket_id];
1597
1598 SCHED_WARN_ON(!bucket->tasks);
1599 if (likely(bucket->tasks))
1600 bucket->tasks--;
1601
1602 uc_se->active = false;
1603
1604 /*
1605 * Keep "local max aggregation" simple and accept to (possibly)
1606 * overboost some RUNNABLE tasks in the same bucket.
1607 * The rq clamp bucket value is reset to its base value whenever
1608 * there are no more RUNNABLE tasks refcounting it.
1609 */
1610 if (likely(bucket->tasks))
1611 return;
1612
1613 rq_clamp = uclamp_rq_get(rq, clamp_id);
1614 /*
1615 * Defensive programming: this should never happen. If it happens,
1616 * e.g. due to future modification, warn and fixup the expected value.
1617 */
1618 SCHED_WARN_ON(bucket->value > rq_clamp);
1619 if (bucket->value >= rq_clamp) {
1620 bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value);
1621 uclamp_rq_set(rq, clamp_id, bkt_clamp);
1622 }
1623 }
1624
uclamp_rq_inc(struct rq * rq,struct task_struct * p)1625 static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
1626 {
1627 enum uclamp_id clamp_id;
1628
1629 /*
1630 * Avoid any overhead until uclamp is actually used by the userspace.
1631 *
1632 * The condition is constructed such that a NOP is generated when
1633 * sched_uclamp_used is disabled.
1634 */
1635 if (!static_branch_unlikely(&sched_uclamp_used))
1636 return;
1637
1638 if (unlikely(!p->sched_class->uclamp_enabled))
1639 return;
1640
1641 for_each_clamp_id(clamp_id)
1642 uclamp_rq_inc_id(rq, p, clamp_id);
1643
1644 /* Reset clamp idle holding when there is one RUNNABLE task */
1645 if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
1646 rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
1647 }
1648
uclamp_rq_dec(struct rq * rq,struct task_struct * p)1649 static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p)
1650 {
1651 enum uclamp_id clamp_id;
1652
1653 /*
1654 * Avoid any overhead until uclamp is actually used by the userspace.
1655 *
1656 * The condition is constructed such that a NOP is generated when
1657 * sched_uclamp_used is disabled.
1658 */
1659 if (!static_branch_unlikely(&sched_uclamp_used))
1660 return;
1661
1662 if (unlikely(!p->sched_class->uclamp_enabled))
1663 return;
1664
1665 for_each_clamp_id(clamp_id)
1666 uclamp_rq_dec_id(rq, p, clamp_id);
1667 }
1668
uclamp_rq_reinc_id(struct rq * rq,struct task_struct * p,enum uclamp_id clamp_id)1669 static inline void uclamp_rq_reinc_id(struct rq *rq, struct task_struct *p,
1670 enum uclamp_id clamp_id)
1671 {
1672 if (!p->uclamp[clamp_id].active)
1673 return;
1674
1675 uclamp_rq_dec_id(rq, p, clamp_id);
1676 uclamp_rq_inc_id(rq, p, clamp_id);
1677
1678 /*
1679 * Make sure to clear the idle flag if we've transiently reached 0
1680 * active tasks on rq.
1681 */
1682 if (clamp_id == UCLAMP_MAX && (rq->uclamp_flags & UCLAMP_FLAG_IDLE))
1683 rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
1684 }
1685
1686 static inline void
uclamp_update_active(struct task_struct * p)1687 uclamp_update_active(struct task_struct *p)
1688 {
1689 enum uclamp_id clamp_id;
1690 struct rq_flags rf;
1691 struct rq *rq;
1692
1693 /*
1694 * Lock the task and the rq where the task is (or was) queued.
1695 *
1696 * We might lock the (previous) rq of a !RUNNABLE task, but that's the
1697 * price to pay to safely serialize util_{min,max} updates with
1698 * enqueues, dequeues and migration operations.
1699 * This is the same locking schema used by __set_cpus_allowed_ptr().
1700 */
1701 rq = task_rq_lock(p, &rf);
1702
1703 /*
1704 * Setting the clamp bucket is serialized by task_rq_lock().
1705 * If the task is not yet RUNNABLE and its task_struct is not
1706 * affecting a valid clamp bucket, the next time it's enqueued,
1707 * it will already see the updated clamp bucket value.
1708 */
1709 for_each_clamp_id(clamp_id)
1710 uclamp_rq_reinc_id(rq, p, clamp_id);
1711
1712 task_rq_unlock(rq, p, &rf);
1713 }
1714
1715 #ifdef CONFIG_UCLAMP_TASK_GROUP
1716 static inline void
uclamp_update_active_tasks(struct cgroup_subsys_state * css)1717 uclamp_update_active_tasks(struct cgroup_subsys_state *css)
1718 {
1719 struct css_task_iter it;
1720 struct task_struct *p;
1721
1722 css_task_iter_start(css, 0, &it);
1723 while ((p = css_task_iter_next(&it)))
1724 uclamp_update_active(p);
1725 css_task_iter_end(&it);
1726 }
1727
1728 static void cpu_util_update_eff(struct cgroup_subsys_state *css);
1729 #endif
1730
1731 #ifdef CONFIG_SYSCTL
1732 #ifdef CONFIG_UCLAMP_TASK
1733 #ifdef CONFIG_UCLAMP_TASK_GROUP
uclamp_update_root_tg(void)1734 static void uclamp_update_root_tg(void)
1735 {
1736 struct task_group *tg = &root_task_group;
1737
1738 uclamp_se_set(&tg->uclamp_req[UCLAMP_MIN],
1739 sysctl_sched_uclamp_util_min, false);
1740 uclamp_se_set(&tg->uclamp_req[UCLAMP_MAX],
1741 sysctl_sched_uclamp_util_max, false);
1742
1743 rcu_read_lock();
1744 cpu_util_update_eff(&root_task_group.css);
1745 rcu_read_unlock();
1746 }
1747 #else
uclamp_update_root_tg(void)1748 static void uclamp_update_root_tg(void) { }
1749 #endif
1750
uclamp_sync_util_min_rt_default(void)1751 static void uclamp_sync_util_min_rt_default(void)
1752 {
1753 struct task_struct *g, *p;
1754
1755 /*
1756 * copy_process() sysctl_uclamp
1757 * uclamp_min_rt = X;
1758 * write_lock(&tasklist_lock) read_lock(&tasklist_lock)
1759 * // link thread smp_mb__after_spinlock()
1760 * write_unlock(&tasklist_lock) read_unlock(&tasklist_lock);
1761 * sched_post_fork() for_each_process_thread()
1762 * __uclamp_sync_rt() __uclamp_sync_rt()
1763 *
1764 * Ensures that either sched_post_fork() will observe the new
1765 * uclamp_min_rt or for_each_process_thread() will observe the new
1766 * task.
1767 */
1768 read_lock(&tasklist_lock);
1769 smp_mb__after_spinlock();
1770 read_unlock(&tasklist_lock);
1771
1772 rcu_read_lock();
1773 for_each_process_thread(g, p)
1774 uclamp_update_util_min_rt_default(p);
1775 rcu_read_unlock();
1776 }
1777
sysctl_sched_uclamp_handler(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)1778 static int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
1779 void *buffer, size_t *lenp, loff_t *ppos)
1780 {
1781 bool update_root_tg = false;
1782 int old_min, old_max, old_min_rt;
1783 int result;
1784
1785 mutex_lock(&uclamp_mutex);
1786 old_min = sysctl_sched_uclamp_util_min;
1787 old_max = sysctl_sched_uclamp_util_max;
1788 old_min_rt = sysctl_sched_uclamp_util_min_rt_default;
1789
1790 result = proc_dointvec(table, write, buffer, lenp, ppos);
1791 if (result)
1792 goto undo;
1793 if (!write)
1794 goto done;
1795
1796 if (sysctl_sched_uclamp_util_min > sysctl_sched_uclamp_util_max ||
1797 sysctl_sched_uclamp_util_max > SCHED_CAPACITY_SCALE ||
1798 sysctl_sched_uclamp_util_min_rt_default > SCHED_CAPACITY_SCALE) {
1799
1800 result = -EINVAL;
1801 goto undo;
1802 }
1803
1804 if (old_min != sysctl_sched_uclamp_util_min) {
1805 uclamp_se_set(&uclamp_default[UCLAMP_MIN],
1806 sysctl_sched_uclamp_util_min, false);
1807 update_root_tg = true;
1808 }
1809 if (old_max != sysctl_sched_uclamp_util_max) {
1810 uclamp_se_set(&uclamp_default[UCLAMP_MAX],
1811 sysctl_sched_uclamp_util_max, false);
1812 update_root_tg = true;
1813 }
1814
1815 if (update_root_tg) {
1816 static_branch_enable(&sched_uclamp_used);
1817 uclamp_update_root_tg();
1818 }
1819
1820 if (old_min_rt != sysctl_sched_uclamp_util_min_rt_default) {
1821 static_branch_enable(&sched_uclamp_used);
1822 uclamp_sync_util_min_rt_default();
1823 }
1824
1825 /*
1826 * We update all RUNNABLE tasks only when task groups are in use.
1827 * Otherwise, keep it simple and do just a lazy update at each next
1828 * task enqueue time.
1829 */
1830
1831 goto done;
1832
1833 undo:
1834 sysctl_sched_uclamp_util_min = old_min;
1835 sysctl_sched_uclamp_util_max = old_max;
1836 sysctl_sched_uclamp_util_min_rt_default = old_min_rt;
1837 done:
1838 mutex_unlock(&uclamp_mutex);
1839
1840 return result;
1841 }
1842 #endif
1843 #endif
1844
uclamp_validate(struct task_struct * p,const struct sched_attr * attr)1845 static int uclamp_validate(struct task_struct *p,
1846 const struct sched_attr *attr)
1847 {
1848 int util_min = p->uclamp_req[UCLAMP_MIN].value;
1849 int util_max = p->uclamp_req[UCLAMP_MAX].value;
1850
1851 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) {
1852 util_min = attr->sched_util_min;
1853
1854 if (util_min + 1 > SCHED_CAPACITY_SCALE + 1)
1855 return -EINVAL;
1856 }
1857
1858 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) {
1859 util_max = attr->sched_util_max;
1860
1861 if (util_max + 1 > SCHED_CAPACITY_SCALE + 1)
1862 return -EINVAL;
1863 }
1864
1865 if (util_min != -1 && util_max != -1 && util_min > util_max)
1866 return -EINVAL;
1867
1868 /*
1869 * We have valid uclamp attributes; make sure uclamp is enabled.
1870 *
1871 * We need to do that here, because enabling static branches is a
1872 * blocking operation which obviously cannot be done while holding
1873 * scheduler locks.
1874 */
1875 static_branch_enable(&sched_uclamp_used);
1876
1877 return 0;
1878 }
1879
uclamp_reset(const struct sched_attr * attr,enum uclamp_id clamp_id,struct uclamp_se * uc_se)1880 static bool uclamp_reset(const struct sched_attr *attr,
1881 enum uclamp_id clamp_id,
1882 struct uclamp_se *uc_se)
1883 {
1884 /* Reset on sched class change for a non user-defined clamp value. */
1885 if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)) &&
1886 !uc_se->user_defined)
1887 return true;
1888
1889 /* Reset on sched_util_{min,max} == -1. */
1890 if (clamp_id == UCLAMP_MIN &&
1891 attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN &&
1892 attr->sched_util_min == -1) {
1893 return true;
1894 }
1895
1896 if (clamp_id == UCLAMP_MAX &&
1897 attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX &&
1898 attr->sched_util_max == -1) {
1899 return true;
1900 }
1901
1902 return false;
1903 }
1904
__setscheduler_uclamp(struct task_struct * p,const struct sched_attr * attr)1905 static void __setscheduler_uclamp(struct task_struct *p,
1906 const struct sched_attr *attr)
1907 {
1908 enum uclamp_id clamp_id;
1909
1910 for_each_clamp_id(clamp_id) {
1911 struct uclamp_se *uc_se = &p->uclamp_req[clamp_id];
1912 unsigned int value;
1913
1914 if (!uclamp_reset(attr, clamp_id, uc_se))
1915 continue;
1916
1917 /*
1918 * RT by default have a 100% boost value that could be modified
1919 * at runtime.
1920 */
1921 if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN))
1922 value = sysctl_sched_uclamp_util_min_rt_default;
1923 else
1924 value = uclamp_none(clamp_id);
1925
1926 uclamp_se_set(uc_se, value, false);
1927
1928 }
1929
1930 if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)))
1931 return;
1932
1933 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN &&
1934 attr->sched_util_min != -1) {
1935 uclamp_se_set(&p->uclamp_req[UCLAMP_MIN],
1936 attr->sched_util_min, true);
1937 }
1938
1939 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX &&
1940 attr->sched_util_max != -1) {
1941 uclamp_se_set(&p->uclamp_req[UCLAMP_MAX],
1942 attr->sched_util_max, true);
1943 }
1944 }
1945
uclamp_fork(struct task_struct * p)1946 static void uclamp_fork(struct task_struct *p)
1947 {
1948 enum uclamp_id clamp_id;
1949
1950 /*
1951 * We don't need to hold task_rq_lock() when updating p->uclamp_* here
1952 * as the task is still at its early fork stages.
1953 */
1954 for_each_clamp_id(clamp_id)
1955 p->uclamp[clamp_id].active = false;
1956
1957 if (likely(!p->sched_reset_on_fork))
1958 return;
1959
1960 for_each_clamp_id(clamp_id) {
1961 uclamp_se_set(&p->uclamp_req[clamp_id],
1962 uclamp_none(clamp_id), false);
1963 }
1964 }
1965
uclamp_post_fork(struct task_struct * p)1966 static void uclamp_post_fork(struct task_struct *p)
1967 {
1968 uclamp_update_util_min_rt_default(p);
1969 }
1970
init_uclamp_rq(struct rq * rq)1971 static void __init init_uclamp_rq(struct rq *rq)
1972 {
1973 enum uclamp_id clamp_id;
1974 struct uclamp_rq *uc_rq = rq->uclamp;
1975
1976 for_each_clamp_id(clamp_id) {
1977 uc_rq[clamp_id] = (struct uclamp_rq) {
1978 .value = uclamp_none(clamp_id)
1979 };
1980 }
1981
1982 rq->uclamp_flags = UCLAMP_FLAG_IDLE;
1983 }
1984
init_uclamp(void)1985 static void __init init_uclamp(void)
1986 {
1987 struct uclamp_se uc_max = {};
1988 enum uclamp_id clamp_id;
1989 int cpu;
1990
1991 for_each_possible_cpu(cpu)
1992 init_uclamp_rq(cpu_rq(cpu));
1993
1994 for_each_clamp_id(clamp_id) {
1995 uclamp_se_set(&init_task.uclamp_req[clamp_id],
1996 uclamp_none(clamp_id), false);
1997 }
1998
1999 /* System defaults allow max clamp values for both indexes */
2000 uclamp_se_set(&uc_max, uclamp_none(UCLAMP_MAX), false);
2001 for_each_clamp_id(clamp_id) {
2002 uclamp_default[clamp_id] = uc_max;
2003 #ifdef CONFIG_UCLAMP_TASK_GROUP
2004 root_task_group.uclamp_req[clamp_id] = uc_max;
2005 root_task_group.uclamp[clamp_id] = uc_max;
2006 #endif
2007 }
2008 }
2009
2010 #else /* CONFIG_UCLAMP_TASK */
uclamp_rq_inc(struct rq * rq,struct task_struct * p)2011 static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p) { }
uclamp_rq_dec(struct rq * rq,struct task_struct * p)2012 static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { }
uclamp_validate(struct task_struct * p,const struct sched_attr * attr)2013 static inline int uclamp_validate(struct task_struct *p,
2014 const struct sched_attr *attr)
2015 {
2016 return -EOPNOTSUPP;
2017 }
__setscheduler_uclamp(struct task_struct * p,const struct sched_attr * attr)2018 static void __setscheduler_uclamp(struct task_struct *p,
2019 const struct sched_attr *attr) { }
uclamp_fork(struct task_struct * p)2020 static inline void uclamp_fork(struct task_struct *p) { }
uclamp_post_fork(struct task_struct * p)2021 static inline void uclamp_post_fork(struct task_struct *p) { }
init_uclamp(void)2022 static inline void init_uclamp(void) { }
2023 #endif /* CONFIG_UCLAMP_TASK */
2024
sched_task_on_rq(struct task_struct * p)2025 bool sched_task_on_rq(struct task_struct *p)
2026 {
2027 return task_on_rq_queued(p);
2028 }
2029
get_wchan(struct task_struct * p)2030 unsigned long get_wchan(struct task_struct *p)
2031 {
2032 unsigned long ip = 0;
2033 unsigned int state;
2034
2035 if (!p || p == current)
2036 return 0;
2037
2038 /* Only get wchan if task is blocked and we can keep it that way. */
2039 raw_spin_lock_irq(&p->pi_lock);
2040 state = READ_ONCE(p->__state);
2041 smp_rmb(); /* see try_to_wake_up() */
2042 if (state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq)
2043 ip = __get_wchan(p);
2044 raw_spin_unlock_irq(&p->pi_lock);
2045
2046 return ip;
2047 }
2048
enqueue_task(struct rq * rq,struct task_struct * p,int flags)2049 static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
2050 {
2051 if (!(flags & ENQUEUE_NOCLOCK))
2052 update_rq_clock(rq);
2053
2054 if (!(flags & ENQUEUE_RESTORE)) {
2055 sched_info_enqueue(rq, p);
2056 psi_enqueue(p, flags & ENQUEUE_WAKEUP);
2057 }
2058
2059 uclamp_rq_inc(rq, p);
2060 p->sched_class->enqueue_task(rq, p, flags);
2061
2062 if (sched_core_enabled(rq))
2063 sched_core_enqueue(rq, p);
2064 }
2065
dequeue_task(struct rq * rq,struct task_struct * p,int flags)2066 static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
2067 {
2068 if (sched_core_enabled(rq))
2069 sched_core_dequeue(rq, p, flags);
2070
2071 if (!(flags & DEQUEUE_NOCLOCK))
2072 update_rq_clock(rq);
2073
2074 if (!(flags & DEQUEUE_SAVE)) {
2075 sched_info_dequeue(rq, p);
2076 psi_dequeue(p, flags & DEQUEUE_SLEEP);
2077 }
2078
2079 uclamp_rq_dec(rq, p);
2080 p->sched_class->dequeue_task(rq, p, flags);
2081 }
2082
activate_task(struct rq * rq,struct task_struct * p,int flags)2083 void activate_task(struct rq *rq, struct task_struct *p, int flags)
2084 {
2085 enqueue_task(rq, p, flags);
2086
2087 p->on_rq = TASK_ON_RQ_QUEUED;
2088 }
2089
deactivate_task(struct rq * rq,struct task_struct * p,int flags)2090 void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
2091 {
2092 p->on_rq = (flags & DEQUEUE_SLEEP) ? 0 : TASK_ON_RQ_MIGRATING;
2093
2094 dequeue_task(rq, p, flags);
2095 }
2096
__normal_prio(int policy,int rt_prio,int nice)2097 static inline int __normal_prio(int policy, int rt_prio, int nice)
2098 {
2099 int prio;
2100
2101 if (dl_policy(policy))
2102 prio = MAX_DL_PRIO - 1;
2103 else if (rt_policy(policy))
2104 prio = MAX_RT_PRIO - 1 - rt_prio;
2105 else
2106 prio = NICE_TO_PRIO(nice);
2107
2108 return prio;
2109 }
2110
2111 /*
2112 * Calculate the expected normal priority: i.e. priority
2113 * without taking RT-inheritance into account. Might be
2114 * boosted by interactivity modifiers. Changes upon fork,
2115 * setprio syscalls, and whenever the interactivity
2116 * estimator recalculates.
2117 */
normal_prio(struct task_struct * p)2118 static inline int normal_prio(struct task_struct *p)
2119 {
2120 return __normal_prio(p->policy, p->rt_priority, PRIO_TO_NICE(p->static_prio));
2121 }
2122
2123 /*
2124 * Calculate the current priority, i.e. the priority
2125 * taken into account by the scheduler. This value might
2126 * be boosted by RT tasks, or might be boosted by
2127 * interactivity modifiers. Will be RT if the task got
2128 * RT-boosted. If not then it returns p->normal_prio.
2129 */
effective_prio(struct task_struct * p)2130 static int effective_prio(struct task_struct *p)
2131 {
2132 p->normal_prio = normal_prio(p);
2133 /*
2134 * If we are RT tasks or we were boosted to RT priority,
2135 * keep the priority unchanged. Otherwise, update priority
2136 * to the normal priority:
2137 */
2138 if (!rt_prio(p->prio))
2139 return p->normal_prio;
2140 return p->prio;
2141 }
2142
2143 /**
2144 * task_curr - is this task currently executing on a CPU?
2145 * @p: the task in question.
2146 *
2147 * Return: 1 if the task is currently executing. 0 otherwise.
2148 */
task_curr(const struct task_struct * p)2149 inline int task_curr(const struct task_struct *p)
2150 {
2151 return cpu_curr(task_cpu(p)) == p;
2152 }
2153
2154 /*
2155 * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
2156 * use the balance_callback list if you want balancing.
2157 *
2158 * this means any call to check_class_changed() must be followed by a call to
2159 * balance_callback().
2160 */
check_class_changed(struct rq * rq,struct task_struct * p,const struct sched_class * prev_class,int oldprio)2161 static inline void check_class_changed(struct rq *rq, struct task_struct *p,
2162 const struct sched_class *prev_class,
2163 int oldprio)
2164 {
2165 if (prev_class != p->sched_class) {
2166 if (prev_class->switched_from)
2167 prev_class->switched_from(rq, p);
2168
2169 p->sched_class->switched_to(rq, p);
2170 } else if (oldprio != p->prio || dl_task(p))
2171 p->sched_class->prio_changed(rq, p, oldprio);
2172 }
2173
check_preempt_curr(struct rq * rq,struct task_struct * p,int flags)2174 void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
2175 {
2176 if (p->sched_class == rq->curr->sched_class)
2177 rq->curr->sched_class->check_preempt_curr(rq, p, flags);
2178 else if (sched_class_above(p->sched_class, rq->curr->sched_class))
2179 resched_curr(rq);
2180
2181 /*
2182 * A queue event has occurred, and we're going to schedule. In
2183 * this case, we can save a useless back to back clock update.
2184 */
2185 if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
2186 rq_clock_skip_update(rq);
2187 }
2188
2189 #ifdef CONFIG_SMP
2190
2191 static void
2192 __do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32 flags);
2193
2194 static int __set_cpus_allowed_ptr(struct task_struct *p,
2195 const struct cpumask *new_mask,
2196 u32 flags);
2197
migrate_disable_switch(struct rq * rq,struct task_struct * p)2198 static void migrate_disable_switch(struct rq *rq, struct task_struct *p)
2199 {
2200 if (likely(!p->migration_disabled))
2201 return;
2202
2203 if (p->cpus_ptr != &p->cpus_mask)
2204 return;
2205
2206 /*
2207 * Violates locking rules! see comment in __do_set_cpus_allowed().
2208 */
2209 __do_set_cpus_allowed(p, cpumask_of(rq->cpu), SCA_MIGRATE_DISABLE);
2210 }
2211
migrate_disable(void)2212 void migrate_disable(void)
2213 {
2214 struct task_struct *p = current;
2215
2216 if (p->migration_disabled) {
2217 p->migration_disabled++;
2218 return;
2219 }
2220
2221 preempt_disable();
2222 this_rq()->nr_pinned++;
2223 p->migration_disabled = 1;
2224 preempt_enable();
2225 }
2226 EXPORT_SYMBOL_GPL(migrate_disable);
2227
migrate_enable(void)2228 void migrate_enable(void)
2229 {
2230 struct task_struct *p = current;
2231
2232 if (p->migration_disabled > 1) {
2233 p->migration_disabled--;
2234 return;
2235 }
2236
2237 if (WARN_ON_ONCE(!p->migration_disabled))
2238 return;
2239
2240 /*
2241 * Ensure stop_task runs either before or after this, and that
2242 * __set_cpus_allowed_ptr(SCA_MIGRATE_ENABLE) doesn't schedule().
2243 */
2244 preempt_disable();
2245 if (p->cpus_ptr != &p->cpus_mask)
2246 __set_cpus_allowed_ptr(p, &p->cpus_mask, SCA_MIGRATE_ENABLE);
2247 /*
2248 * Mustn't clear migration_disabled() until cpus_ptr points back at the
2249 * regular cpus_mask, otherwise things that race (eg.
2250 * select_fallback_rq) get confused.
2251 */
2252 barrier();
2253 p->migration_disabled = 0;
2254 this_rq()->nr_pinned--;
2255 preempt_enable();
2256 }
2257 EXPORT_SYMBOL_GPL(migrate_enable);
2258
rq_has_pinned_tasks(struct rq * rq)2259 static inline bool rq_has_pinned_tasks(struct rq *rq)
2260 {
2261 return rq->nr_pinned;
2262 }
2263
2264 /*
2265 * Per-CPU kthreads are allowed to run on !active && online CPUs, see
2266 * __set_cpus_allowed_ptr() and select_fallback_rq().
2267 */
is_cpu_allowed(struct task_struct * p,int cpu)2268 static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
2269 {
2270 /* When not in the task's cpumask, no point in looking further. */
2271 if (!cpumask_test_cpu(cpu, p->cpus_ptr))
2272 return false;
2273
2274 /* migrate_disabled() must be allowed to finish. */
2275 if (is_migration_disabled(p))
2276 return cpu_online(cpu);
2277
2278 /* Non kernel threads are not allowed during either online or offline. */
2279 if (!(p->flags & PF_KTHREAD))
2280 return cpu_active(cpu) && task_cpu_possible(cpu, p);
2281
2282 /* KTHREAD_IS_PER_CPU is always allowed. */
2283 if (kthread_is_per_cpu(p))
2284 return cpu_online(cpu);
2285
2286 /* Regular kernel threads don't get to stay during offline. */
2287 if (cpu_dying(cpu))
2288 return false;
2289
2290 /* But are allowed during online. */
2291 return cpu_online(cpu);
2292 }
2293
2294 /*
2295 * This is how migration works:
2296 *
2297 * 1) we invoke migration_cpu_stop() on the target CPU using
2298 * stop_one_cpu().
2299 * 2) stopper starts to run (implicitly forcing the migrated thread
2300 * off the CPU)
2301 * 3) it checks whether the migrated task is still in the wrong runqueue.
2302 * 4) if it's in the wrong runqueue then the migration thread removes
2303 * it and puts it into the right queue.
2304 * 5) stopper completes and stop_one_cpu() returns and the migration
2305 * is done.
2306 */
2307
2308 /*
2309 * move_queued_task - move a queued task to new rq.
2310 *
2311 * Returns (locked) new rq. Old rq's lock is released.
2312 */
move_queued_task(struct rq * rq,struct rq_flags * rf,struct task_struct * p,int new_cpu)2313 static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf,
2314 struct task_struct *p, int new_cpu)
2315 {
2316 lockdep_assert_rq_held(rq);
2317
2318 deactivate_task(rq, p, DEQUEUE_NOCLOCK);
2319 set_task_cpu(p, new_cpu);
2320 rq_unlock(rq, rf);
2321
2322 rq = cpu_rq(new_cpu);
2323
2324 rq_lock(rq, rf);
2325 WARN_ON_ONCE(task_cpu(p) != new_cpu);
2326 activate_task(rq, p, 0);
2327 check_preempt_curr(rq, p, 0);
2328
2329 return rq;
2330 }
2331
2332 struct migration_arg {
2333 struct task_struct *task;
2334 int dest_cpu;
2335 struct set_affinity_pending *pending;
2336 };
2337
2338 /*
2339 * @refs: number of wait_for_completion()
2340 * @stop_pending: is @stop_work in use
2341 */
2342 struct set_affinity_pending {
2343 refcount_t refs;
2344 unsigned int stop_pending;
2345 struct completion done;
2346 struct cpu_stop_work stop_work;
2347 struct migration_arg arg;
2348 };
2349
2350 /*
2351 * Move (not current) task off this CPU, onto the destination CPU. We're doing
2352 * this because either it can't run here any more (set_cpus_allowed()
2353 * away from this CPU, or CPU going down), or because we're
2354 * attempting to rebalance this task on exec (sched_exec).
2355 *
2356 * So we race with normal scheduler movements, but that's OK, as long
2357 * as the task is no longer on this CPU.
2358 */
__migrate_task(struct rq * rq,struct rq_flags * rf,struct task_struct * p,int dest_cpu)2359 static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf,
2360 struct task_struct *p, int dest_cpu)
2361 {
2362 /* Affinity changed (again). */
2363 if (!is_cpu_allowed(p, dest_cpu))
2364 return rq;
2365
2366 update_rq_clock(rq);
2367 rq = move_queued_task(rq, rf, p, dest_cpu);
2368
2369 return rq;
2370 }
2371
2372 /*
2373 * migration_cpu_stop - this will be executed by a highprio stopper thread
2374 * and performs thread migration by bumping thread off CPU then
2375 * 'pushing' onto another runqueue.
2376 */
migration_cpu_stop(void * data)2377 static int migration_cpu_stop(void *data)
2378 {
2379 struct migration_arg *arg = data;
2380 struct set_affinity_pending *pending = arg->pending;
2381 struct task_struct *p = arg->task;
2382 struct rq *rq = this_rq();
2383 bool complete = false;
2384 struct rq_flags rf;
2385
2386 /*
2387 * The original target CPU might have gone down and we might
2388 * be on another CPU but it doesn't matter.
2389 */
2390 local_irq_save(rf.flags);
2391 /*
2392 * We need to explicitly wake pending tasks before running
2393 * __migrate_task() such that we will not miss enforcing cpus_ptr
2394 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
2395 */
2396 flush_smp_call_function_queue();
2397
2398 raw_spin_lock(&p->pi_lock);
2399 rq_lock(rq, &rf);
2400
2401 /*
2402 * If we were passed a pending, then ->stop_pending was set, thus
2403 * p->migration_pending must have remained stable.
2404 */
2405 WARN_ON_ONCE(pending && pending != p->migration_pending);
2406
2407 /*
2408 * If task_rq(p) != rq, it cannot be migrated here, because we're
2409 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
2410 * we're holding p->pi_lock.
2411 */
2412 if (task_rq(p) == rq) {
2413 if (is_migration_disabled(p))
2414 goto out;
2415
2416 if (pending) {
2417 p->migration_pending = NULL;
2418 complete = true;
2419
2420 if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask))
2421 goto out;
2422 }
2423
2424 if (task_on_rq_queued(p))
2425 rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
2426 else
2427 p->wake_cpu = arg->dest_cpu;
2428
2429 /*
2430 * XXX __migrate_task() can fail, at which point we might end
2431 * up running on a dodgy CPU, AFAICT this can only happen
2432 * during CPU hotplug, at which point we'll get pushed out
2433 * anyway, so it's probably not a big deal.
2434 */
2435
2436 } else if (pending) {
2437 /*
2438 * This happens when we get migrated between migrate_enable()'s
2439 * preempt_enable() and scheduling the stopper task. At that
2440 * point we're a regular task again and not current anymore.
2441 *
2442 * A !PREEMPT kernel has a giant hole here, which makes it far
2443 * more likely.
2444 */
2445
2446 /*
2447 * The task moved before the stopper got to run. We're holding
2448 * ->pi_lock, so the allowed mask is stable - if it got
2449 * somewhere allowed, we're done.
2450 */
2451 if (cpumask_test_cpu(task_cpu(p), p->cpus_ptr)) {
2452 p->migration_pending = NULL;
2453 complete = true;
2454 goto out;
2455 }
2456
2457 /*
2458 * When migrate_enable() hits a rq mis-match we can't reliably
2459 * determine is_migration_disabled() and so have to chase after
2460 * it.
2461 */
2462 WARN_ON_ONCE(!pending->stop_pending);
2463 task_rq_unlock(rq, p, &rf);
2464 stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop,
2465 &pending->arg, &pending->stop_work);
2466 return 0;
2467 }
2468 out:
2469 if (pending)
2470 pending->stop_pending = false;
2471 task_rq_unlock(rq, p, &rf);
2472
2473 if (complete)
2474 complete_all(&pending->done);
2475
2476 return 0;
2477 }
2478
push_cpu_stop(void * arg)2479 int push_cpu_stop(void *arg)
2480 {
2481 struct rq *lowest_rq = NULL, *rq = this_rq();
2482 struct task_struct *p = arg;
2483
2484 raw_spin_lock_irq(&p->pi_lock);
2485 raw_spin_rq_lock(rq);
2486
2487 if (task_rq(p) != rq)
2488 goto out_unlock;
2489
2490 if (is_migration_disabled(p)) {
2491 p->migration_flags |= MDF_PUSH;
2492 goto out_unlock;
2493 }
2494
2495 p->migration_flags &= ~MDF_PUSH;
2496
2497 if (p->sched_class->find_lock_rq)
2498 lowest_rq = p->sched_class->find_lock_rq(p, rq);
2499
2500 if (!lowest_rq)
2501 goto out_unlock;
2502
2503 // XXX validate p is still the highest prio task
2504 if (task_rq(p) == rq) {
2505 deactivate_task(rq, p, 0);
2506 set_task_cpu(p, lowest_rq->cpu);
2507 activate_task(lowest_rq, p, 0);
2508 resched_curr(lowest_rq);
2509 }
2510
2511 double_unlock_balance(rq, lowest_rq);
2512
2513 out_unlock:
2514 rq->push_busy = false;
2515 raw_spin_rq_unlock(rq);
2516 raw_spin_unlock_irq(&p->pi_lock);
2517
2518 put_task_struct(p);
2519 return 0;
2520 }
2521
2522 /*
2523 * sched_class::set_cpus_allowed must do the below, but is not required to
2524 * actually call this function.
2525 */
set_cpus_allowed_common(struct task_struct * p,const struct cpumask * new_mask,u32 flags)2526 void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask, u32 flags)
2527 {
2528 if (flags & (SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) {
2529 p->cpus_ptr = new_mask;
2530 return;
2531 }
2532
2533 cpumask_copy(&p->cpus_mask, new_mask);
2534 p->nr_cpus_allowed = cpumask_weight(new_mask);
2535 }
2536
2537 static void
__do_set_cpus_allowed(struct task_struct * p,const struct cpumask * new_mask,u32 flags)2538 __do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32 flags)
2539 {
2540 struct rq *rq = task_rq(p);
2541 bool queued, running;
2542
2543 /*
2544 * This here violates the locking rules for affinity, since we're only
2545 * supposed to change these variables while holding both rq->lock and
2546 * p->pi_lock.
2547 *
2548 * HOWEVER, it magically works, because ttwu() is the only code that
2549 * accesses these variables under p->pi_lock and only does so after
2550 * smp_cond_load_acquire(&p->on_cpu, !VAL), and we're in __schedule()
2551 * before finish_task().
2552 *
2553 * XXX do further audits, this smells like something putrid.
2554 */
2555 if (flags & SCA_MIGRATE_DISABLE)
2556 SCHED_WARN_ON(!p->on_cpu);
2557 else
2558 lockdep_assert_held(&p->pi_lock);
2559
2560 queued = task_on_rq_queued(p);
2561 running = task_current(rq, p);
2562
2563 if (queued) {
2564 /*
2565 * Because __kthread_bind() calls this on blocked tasks without
2566 * holding rq->lock.
2567 */
2568 lockdep_assert_rq_held(rq);
2569 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
2570 }
2571 if (running)
2572 put_prev_task(rq, p);
2573
2574 p->sched_class->set_cpus_allowed(p, new_mask, flags);
2575
2576 if (queued)
2577 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
2578 if (running)
2579 set_next_task(rq, p);
2580 }
2581
do_set_cpus_allowed(struct task_struct * p,const struct cpumask * new_mask)2582 void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
2583 {
2584 __do_set_cpus_allowed(p, new_mask, 0);
2585 }
2586
dup_user_cpus_ptr(struct task_struct * dst,struct task_struct * src,int node)2587 int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src,
2588 int node)
2589 {
2590 cpumask_t *user_mask;
2591 unsigned long flags;
2592
2593 /*
2594 * Always clear dst->user_cpus_ptr first as their user_cpus_ptr's
2595 * may differ by now due to racing.
2596 */
2597 dst->user_cpus_ptr = NULL;
2598
2599 /*
2600 * This check is racy and losing the race is a valid situation.
2601 * It is not worth the extra overhead of taking the pi_lock on
2602 * every fork/clone.
2603 */
2604 if (data_race(!src->user_cpus_ptr))
2605 return 0;
2606
2607 user_mask = kmalloc_node(cpumask_size(), GFP_KERNEL, node);
2608 if (!user_mask)
2609 return -ENOMEM;
2610
2611 /*
2612 * Use pi_lock to protect content of user_cpus_ptr
2613 *
2614 * Though unlikely, user_cpus_ptr can be reset to NULL by a concurrent
2615 * do_set_cpus_allowed().
2616 */
2617 raw_spin_lock_irqsave(&src->pi_lock, flags);
2618 if (src->user_cpus_ptr) {
2619 swap(dst->user_cpus_ptr, user_mask);
2620 cpumask_copy(dst->user_cpus_ptr, src->user_cpus_ptr);
2621 }
2622 raw_spin_unlock_irqrestore(&src->pi_lock, flags);
2623
2624 if (unlikely(user_mask))
2625 kfree(user_mask);
2626
2627 return 0;
2628 }
2629
clear_user_cpus_ptr(struct task_struct * p)2630 static inline struct cpumask *clear_user_cpus_ptr(struct task_struct *p)
2631 {
2632 struct cpumask *user_mask = NULL;
2633
2634 swap(p->user_cpus_ptr, user_mask);
2635
2636 return user_mask;
2637 }
2638
release_user_cpus_ptr(struct task_struct * p)2639 void release_user_cpus_ptr(struct task_struct *p)
2640 {
2641 kfree(clear_user_cpus_ptr(p));
2642 }
2643
2644 /*
2645 * This function is wildly self concurrent; here be dragons.
2646 *
2647 *
2648 * When given a valid mask, __set_cpus_allowed_ptr() must block until the
2649 * designated task is enqueued on an allowed CPU. If that task is currently
2650 * running, we have to kick it out using the CPU stopper.
2651 *
2652 * Migrate-Disable comes along and tramples all over our nice sandcastle.
2653 * Consider:
2654 *
2655 * Initial conditions: P0->cpus_mask = [0, 1]
2656 *
2657 * P0@CPU0 P1
2658 *
2659 * migrate_disable();
2660 * <preempted>
2661 * set_cpus_allowed_ptr(P0, [1]);
2662 *
2663 * P1 *cannot* return from this set_cpus_allowed_ptr() call until P0 executes
2664 * its outermost migrate_enable() (i.e. it exits its Migrate-Disable region).
2665 * This means we need the following scheme:
2666 *
2667 * P0@CPU0 P1
2668 *
2669 * migrate_disable();
2670 * <preempted>
2671 * set_cpus_allowed_ptr(P0, [1]);
2672 * <blocks>
2673 * <resumes>
2674 * migrate_enable();
2675 * __set_cpus_allowed_ptr();
2676 * <wakes local stopper>
2677 * `--> <woken on migration completion>
2678 *
2679 * Now the fun stuff: there may be several P1-like tasks, i.e. multiple
2680 * concurrent set_cpus_allowed_ptr(P0, [*]) calls. CPU affinity changes of any
2681 * task p are serialized by p->pi_lock, which we can leverage: the one that
2682 * should come into effect at the end of the Migrate-Disable region is the last
2683 * one. This means we only need to track a single cpumask (i.e. p->cpus_mask),
2684 * but we still need to properly signal those waiting tasks at the appropriate
2685 * moment.
2686 *
2687 * This is implemented using struct set_affinity_pending. The first
2688 * __set_cpus_allowed_ptr() caller within a given Migrate-Disable region will
2689 * setup an instance of that struct and install it on the targeted task_struct.
2690 * Any and all further callers will reuse that instance. Those then wait for
2691 * a completion signaled at the tail of the CPU stopper callback (1), triggered
2692 * on the end of the Migrate-Disable region (i.e. outermost migrate_enable()).
2693 *
2694 *
2695 * (1) In the cases covered above. There is one more where the completion is
2696 * signaled within affine_move_task() itself: when a subsequent affinity request
2697 * occurs after the stopper bailed out due to the targeted task still being
2698 * Migrate-Disable. Consider:
2699 *
2700 * Initial conditions: P0->cpus_mask = [0, 1]
2701 *
2702 * CPU0 P1 P2
2703 * <P0>
2704 * migrate_disable();
2705 * <preempted>
2706 * set_cpus_allowed_ptr(P0, [1]);
2707 * <blocks>
2708 * <migration/0>
2709 * migration_cpu_stop()
2710 * is_migration_disabled()
2711 * <bails>
2712 * set_cpus_allowed_ptr(P0, [0, 1]);
2713 * <signal completion>
2714 * <awakes>
2715 *
2716 * Note that the above is safe vs a concurrent migrate_enable(), as any
2717 * pending affinity completion is preceded by an uninstallation of
2718 * p->migration_pending done with p->pi_lock held.
2719 */
affine_move_task(struct rq * rq,struct task_struct * p,struct rq_flags * rf,int dest_cpu,unsigned int flags)2720 static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flags *rf,
2721 int dest_cpu, unsigned int flags)
2722 {
2723 struct set_affinity_pending my_pending = { }, *pending = NULL;
2724 bool stop_pending, complete = false;
2725
2726 /* Can the task run on the task's current CPU? If so, we're done */
2727 if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) {
2728 struct task_struct *push_task = NULL;
2729
2730 if ((flags & SCA_MIGRATE_ENABLE) &&
2731 (p->migration_flags & MDF_PUSH) && !rq->push_busy) {
2732 rq->push_busy = true;
2733 push_task = get_task_struct(p);
2734 }
2735
2736 /*
2737 * If there are pending waiters, but no pending stop_work,
2738 * then complete now.
2739 */
2740 pending = p->migration_pending;
2741 if (pending && !pending->stop_pending) {
2742 p->migration_pending = NULL;
2743 complete = true;
2744 }
2745
2746 task_rq_unlock(rq, p, rf);
2747
2748 if (push_task) {
2749 stop_one_cpu_nowait(rq->cpu, push_cpu_stop,
2750 p, &rq->push_work);
2751 }
2752
2753 if (complete)
2754 complete_all(&pending->done);
2755
2756 return 0;
2757 }
2758
2759 if (!(flags & SCA_MIGRATE_ENABLE)) {
2760 /* serialized by p->pi_lock */
2761 if (!p->migration_pending) {
2762 /* Install the request */
2763 refcount_set(&my_pending.refs, 1);
2764 init_completion(&my_pending.done);
2765 my_pending.arg = (struct migration_arg) {
2766 .task = p,
2767 .dest_cpu = dest_cpu,
2768 .pending = &my_pending,
2769 };
2770
2771 p->migration_pending = &my_pending;
2772 } else {
2773 pending = p->migration_pending;
2774 refcount_inc(&pending->refs);
2775 /*
2776 * Affinity has changed, but we've already installed a
2777 * pending. migration_cpu_stop() *must* see this, else
2778 * we risk a completion of the pending despite having a
2779 * task on a disallowed CPU.
2780 *
2781 * Serialized by p->pi_lock, so this is safe.
2782 */
2783 pending->arg.dest_cpu = dest_cpu;
2784 }
2785 }
2786 pending = p->migration_pending;
2787 /*
2788 * - !MIGRATE_ENABLE:
2789 * we'll have installed a pending if there wasn't one already.
2790 *
2791 * - MIGRATE_ENABLE:
2792 * we're here because the current CPU isn't matching anymore,
2793 * the only way that can happen is because of a concurrent
2794 * set_cpus_allowed_ptr() call, which should then still be
2795 * pending completion.
2796 *
2797 * Either way, we really should have a @pending here.
2798 */
2799 if (WARN_ON_ONCE(!pending)) {
2800 task_rq_unlock(rq, p, rf);
2801 return -EINVAL;
2802 }
2803
2804 if (task_on_cpu(rq, p) || READ_ONCE(p->__state) == TASK_WAKING) {
2805 /*
2806 * MIGRATE_ENABLE gets here because 'p == current', but for
2807 * anything else we cannot do is_migration_disabled(), punt
2808 * and have the stopper function handle it all race-free.
2809 */
2810 stop_pending = pending->stop_pending;
2811 if (!stop_pending)
2812 pending->stop_pending = true;
2813
2814 if (flags & SCA_MIGRATE_ENABLE)
2815 p->migration_flags &= ~MDF_PUSH;
2816
2817 task_rq_unlock(rq, p, rf);
2818
2819 if (!stop_pending) {
2820 stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
2821 &pending->arg, &pending->stop_work);
2822 }
2823
2824 if (flags & SCA_MIGRATE_ENABLE)
2825 return 0;
2826 } else {
2827
2828 if (!is_migration_disabled(p)) {
2829 if (task_on_rq_queued(p))
2830 rq = move_queued_task(rq, rf, p, dest_cpu);
2831
2832 if (!pending->stop_pending) {
2833 p->migration_pending = NULL;
2834 complete = true;
2835 }
2836 }
2837 task_rq_unlock(rq, p, rf);
2838
2839 if (complete)
2840 complete_all(&pending->done);
2841 }
2842
2843 wait_for_completion(&pending->done);
2844
2845 if (refcount_dec_and_test(&pending->refs))
2846 wake_up_var(&pending->refs); /* No UaF, just an address */
2847
2848 /*
2849 * Block the original owner of &pending until all subsequent callers
2850 * have seen the completion and decremented the refcount
2851 */
2852 wait_var_event(&my_pending.refs, !refcount_read(&my_pending.refs));
2853
2854 /* ARGH */
2855 WARN_ON_ONCE(my_pending.stop_pending);
2856
2857 return 0;
2858 }
2859
2860 /*
2861 * Called with both p->pi_lock and rq->lock held; drops both before returning.
2862 */
__set_cpus_allowed_ptr_locked(struct task_struct * p,const struct cpumask * new_mask,u32 flags,struct rq * rq,struct rq_flags * rf)2863 static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
2864 const struct cpumask *new_mask,
2865 u32 flags,
2866 struct rq *rq,
2867 struct rq_flags *rf)
2868 __releases(rq->lock)
2869 __releases(p->pi_lock)
2870 {
2871 const struct cpumask *cpu_allowed_mask = task_cpu_possible_mask(p);
2872 const struct cpumask *cpu_valid_mask = cpu_active_mask;
2873 bool kthread = p->flags & PF_KTHREAD;
2874 struct cpumask *user_mask = NULL;
2875 unsigned int dest_cpu;
2876 int ret = 0;
2877
2878 update_rq_clock(rq);
2879
2880 if (kthread || is_migration_disabled(p)) {
2881 /*
2882 * Kernel threads are allowed on online && !active CPUs,
2883 * however, during cpu-hot-unplug, even these might get pushed
2884 * away if not KTHREAD_IS_PER_CPU.
2885 *
2886 * Specifically, migration_disabled() tasks must not fail the
2887 * cpumask_any_and_distribute() pick below, esp. so on
2888 * SCA_MIGRATE_ENABLE, otherwise we'll not call
2889 * set_cpus_allowed_common() and actually reset p->cpus_ptr.
2890 */
2891 cpu_valid_mask = cpu_online_mask;
2892 }
2893
2894 if (!kthread && !cpumask_subset(new_mask, cpu_allowed_mask)) {
2895 ret = -EINVAL;
2896 goto out;
2897 }
2898
2899 /*
2900 * Must re-check here, to close a race against __kthread_bind(),
2901 * sched_setaffinity() is not guaranteed to observe the flag.
2902 */
2903 if ((flags & SCA_CHECK) && (p->flags & PF_NO_SETAFFINITY)) {
2904 ret = -EINVAL;
2905 goto out;
2906 }
2907
2908 if (!(flags & SCA_MIGRATE_ENABLE)) {
2909 if (cpumask_equal(&p->cpus_mask, new_mask))
2910 goto out;
2911
2912 if (WARN_ON_ONCE(p == current &&
2913 is_migration_disabled(p) &&
2914 !cpumask_test_cpu(task_cpu(p), new_mask))) {
2915 ret = -EBUSY;
2916 goto out;
2917 }
2918 }
2919
2920 /*
2921 * Picking a ~random cpu helps in cases where we are changing affinity
2922 * for groups of tasks (ie. cpuset), so that load balancing is not
2923 * immediately required to distribute the tasks within their new mask.
2924 */
2925 dest_cpu = cpumask_any_and_distribute(cpu_valid_mask, new_mask);
2926 if (dest_cpu >= nr_cpu_ids) {
2927 ret = -EINVAL;
2928 goto out;
2929 }
2930
2931 __do_set_cpus_allowed(p, new_mask, flags);
2932
2933 if (flags & SCA_USER)
2934 user_mask = clear_user_cpus_ptr(p);
2935
2936 ret = affine_move_task(rq, p, rf, dest_cpu, flags);
2937
2938 kfree(user_mask);
2939
2940 return ret;
2941
2942 out:
2943 task_rq_unlock(rq, p, rf);
2944
2945 return ret;
2946 }
2947
2948 /*
2949 * Change a given task's CPU affinity. Migrate the thread to a
2950 * proper CPU and schedule it away if the CPU it's executing on
2951 * is removed from the allowed bitmask.
2952 *
2953 * NOTE: the caller must have a valid reference to the task, the
2954 * task must not exit() & deallocate itself prematurely. The
2955 * call is not atomic; no spinlocks may be held.
2956 */
__set_cpus_allowed_ptr(struct task_struct * p,const struct cpumask * new_mask,u32 flags)2957 static int __set_cpus_allowed_ptr(struct task_struct *p,
2958 const struct cpumask *new_mask, u32 flags)
2959 {
2960 struct rq_flags rf;
2961 struct rq *rq;
2962
2963 rq = task_rq_lock(p, &rf);
2964 return __set_cpus_allowed_ptr_locked(p, new_mask, flags, rq, &rf);
2965 }
2966
set_cpus_allowed_ptr(struct task_struct * p,const struct cpumask * new_mask)2967 int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
2968 {
2969 return __set_cpus_allowed_ptr(p, new_mask, 0);
2970 }
2971 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
2972
2973 /*
2974 * Change a given task's CPU affinity to the intersection of its current
2975 * affinity mask and @subset_mask, writing the resulting mask to @new_mask
2976 * and pointing @p->user_cpus_ptr to a copy of the old mask.
2977 * If the resulting mask is empty, leave the affinity unchanged and return
2978 * -EINVAL.
2979 */
restrict_cpus_allowed_ptr(struct task_struct * p,struct cpumask * new_mask,const struct cpumask * subset_mask)2980 static int restrict_cpus_allowed_ptr(struct task_struct *p,
2981 struct cpumask *new_mask,
2982 const struct cpumask *subset_mask)
2983 {
2984 struct cpumask *user_mask = NULL;
2985 struct rq_flags rf;
2986 struct rq *rq;
2987 int err;
2988
2989 if (!p->user_cpus_ptr) {
2990 user_mask = kmalloc(cpumask_size(), GFP_KERNEL);
2991 if (!user_mask)
2992 return -ENOMEM;
2993 }
2994
2995 rq = task_rq_lock(p, &rf);
2996
2997 /*
2998 * Forcefully restricting the affinity of a deadline task is
2999 * likely to cause problems, so fail and noisily override the
3000 * mask entirely.
3001 */
3002 if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
3003 err = -EPERM;
3004 goto err_unlock;
3005 }
3006
3007 if (!cpumask_and(new_mask, &p->cpus_mask, subset_mask)) {
3008 err = -EINVAL;
3009 goto err_unlock;
3010 }
3011
3012 /*
3013 * We're about to butcher the task affinity, so keep track of what
3014 * the user asked for in case we're able to restore it later on.
3015 */
3016 if (user_mask) {
3017 cpumask_copy(user_mask, p->cpus_ptr);
3018 p->user_cpus_ptr = user_mask;
3019 }
3020
3021 return __set_cpus_allowed_ptr_locked(p, new_mask, 0, rq, &rf);
3022
3023 err_unlock:
3024 task_rq_unlock(rq, p, &rf);
3025 kfree(user_mask);
3026 return err;
3027 }
3028
3029 /*
3030 * Restrict the CPU affinity of task @p so that it is a subset of
3031 * task_cpu_possible_mask() and point @p->user_cpu_ptr to a copy of the
3032 * old affinity mask. If the resulting mask is empty, we warn and walk
3033 * up the cpuset hierarchy until we find a suitable mask.
3034 */
force_compatible_cpus_allowed_ptr(struct task_struct * p)3035 void force_compatible_cpus_allowed_ptr(struct task_struct *p)
3036 {
3037 cpumask_var_t new_mask;
3038 const struct cpumask *override_mask = task_cpu_possible_mask(p);
3039
3040 alloc_cpumask_var(&new_mask, GFP_KERNEL);
3041
3042 /*
3043 * __migrate_task() can fail silently in the face of concurrent
3044 * offlining of the chosen destination CPU, so take the hotplug
3045 * lock to ensure that the migration succeeds.
3046 */
3047 cpus_read_lock();
3048 if (!cpumask_available(new_mask))
3049 goto out_set_mask;
3050
3051 if (!restrict_cpus_allowed_ptr(p, new_mask, override_mask))
3052 goto out_free_mask;
3053
3054 /*
3055 * We failed to find a valid subset of the affinity mask for the
3056 * task, so override it based on its cpuset hierarchy.
3057 */
3058 cpuset_cpus_allowed(p, new_mask);
3059 override_mask = new_mask;
3060
3061 out_set_mask:
3062 if (printk_ratelimit()) {
3063 printk_deferred("Overriding affinity for process %d (%s) to CPUs %*pbl\n",
3064 task_pid_nr(p), p->comm,
3065 cpumask_pr_args(override_mask));
3066 }
3067
3068 WARN_ON(set_cpus_allowed_ptr(p, override_mask));
3069 out_free_mask:
3070 cpus_read_unlock();
3071 free_cpumask_var(new_mask);
3072 }
3073
3074 static int
3075 __sched_setaffinity(struct task_struct *p, const struct cpumask *mask);
3076
3077 /*
3078 * Restore the affinity of a task @p which was previously restricted by a
3079 * call to force_compatible_cpus_allowed_ptr(). This will clear (and free)
3080 * @p->user_cpus_ptr.
3081 *
3082 * It is the caller's responsibility to serialise this with any calls to
3083 * force_compatible_cpus_allowed_ptr(@p).
3084 */
relax_compatible_cpus_allowed_ptr(struct task_struct * p)3085 void relax_compatible_cpus_allowed_ptr(struct task_struct *p)
3086 {
3087 struct cpumask *user_mask = p->user_cpus_ptr;
3088 unsigned long flags;
3089
3090 /*
3091 * Try to restore the old affinity mask. If this fails, then
3092 * we free the mask explicitly to avoid it being inherited across
3093 * a subsequent fork().
3094 */
3095 if (!user_mask || !__sched_setaffinity(p, user_mask))
3096 return;
3097
3098 raw_spin_lock_irqsave(&p->pi_lock, flags);
3099 user_mask = clear_user_cpus_ptr(p);
3100 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
3101
3102 kfree(user_mask);
3103 }
3104
set_task_cpu(struct task_struct * p,unsigned int new_cpu)3105 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
3106 {
3107 #ifdef CONFIG_SCHED_DEBUG
3108 unsigned int state = READ_ONCE(p->__state);
3109
3110 /*
3111 * We should never call set_task_cpu() on a blocked task,
3112 * ttwu() will sort out the placement.
3113 */
3114 WARN_ON_ONCE(state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq);
3115
3116 /*
3117 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
3118 * because schedstat_wait_{start,end} rebase migrating task's wait_start
3119 * time relying on p->on_rq.
3120 */
3121 WARN_ON_ONCE(state == TASK_RUNNING &&
3122 p->sched_class == &fair_sched_class &&
3123 (p->on_rq && !task_on_rq_migrating(p)));
3124
3125 #ifdef CONFIG_LOCKDEP
3126 /*
3127 * The caller should hold either p->pi_lock or rq->lock, when changing
3128 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
3129 *
3130 * sched_move_task() holds both and thus holding either pins the cgroup,
3131 * see task_group().
3132 *
3133 * Furthermore, all task_rq users should acquire both locks, see
3134 * task_rq_lock().
3135 */
3136 WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
3137 lockdep_is_held(__rq_lockp(task_rq(p)))));
3138 #endif
3139 /*
3140 * Clearly, migrating tasks to offline CPUs is a fairly daft thing.
3141 */
3142 WARN_ON_ONCE(!cpu_online(new_cpu));
3143
3144 WARN_ON_ONCE(is_migration_disabled(p));
3145 #endif
3146
3147 trace_sched_migrate_task(p, new_cpu);
3148
3149 if (task_cpu(p) != new_cpu) {
3150 if (p->sched_class->migrate_task_rq)
3151 p->sched_class->migrate_task_rq(p, new_cpu);
3152 p->se.nr_migrations++;
3153 rseq_migrate(p);
3154 perf_event_task_migrate(p);
3155 }
3156
3157 __set_task_cpu(p, new_cpu);
3158 }
3159
3160 #ifdef CONFIG_NUMA_BALANCING
__migrate_swap_task(struct task_struct * p,int cpu)3161 static void __migrate_swap_task(struct task_struct *p, int cpu)
3162 {
3163 if (task_on_rq_queued(p)) {
3164 struct rq *src_rq, *dst_rq;
3165 struct rq_flags srf, drf;
3166
3167 src_rq = task_rq(p);
3168 dst_rq = cpu_rq(cpu);
3169
3170 rq_pin_lock(src_rq, &srf);
3171 rq_pin_lock(dst_rq, &drf);
3172
3173 deactivate_task(src_rq, p, 0);
3174 set_task_cpu(p, cpu);
3175 activate_task(dst_rq, p, 0);
3176 check_preempt_curr(dst_rq, p, 0);
3177
3178 rq_unpin_lock(dst_rq, &drf);
3179 rq_unpin_lock(src_rq, &srf);
3180
3181 } else {
3182 /*
3183 * Task isn't running anymore; make it appear like we migrated
3184 * it before it went to sleep. This means on wakeup we make the
3185 * previous CPU our target instead of where it really is.
3186 */
3187 p->wake_cpu = cpu;
3188 }
3189 }
3190
3191 struct migration_swap_arg {
3192 struct task_struct *src_task, *dst_task;
3193 int src_cpu, dst_cpu;
3194 };
3195
migrate_swap_stop(void * data)3196 static int migrate_swap_stop(void *data)
3197 {
3198 struct migration_swap_arg *arg = data;
3199 struct rq *src_rq, *dst_rq;
3200 int ret = -EAGAIN;
3201
3202 if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
3203 return -EAGAIN;
3204
3205 src_rq = cpu_rq(arg->src_cpu);
3206 dst_rq = cpu_rq(arg->dst_cpu);
3207
3208 double_raw_lock(&arg->src_task->pi_lock,
3209 &arg->dst_task->pi_lock);
3210 double_rq_lock(src_rq, dst_rq);
3211
3212 if (task_cpu(arg->dst_task) != arg->dst_cpu)
3213 goto unlock;
3214
3215 if (task_cpu(arg->src_task) != arg->src_cpu)
3216 goto unlock;
3217
3218 if (!cpumask_test_cpu(arg->dst_cpu, arg->src_task->cpus_ptr))
3219 goto unlock;
3220
3221 if (!cpumask_test_cpu(arg->src_cpu, arg->dst_task->cpus_ptr))
3222 goto unlock;
3223
3224 __migrate_swap_task(arg->src_task, arg->dst_cpu);
3225 __migrate_swap_task(arg->dst_task, arg->src_cpu);
3226
3227 ret = 0;
3228
3229 unlock:
3230 double_rq_unlock(src_rq, dst_rq);
3231 raw_spin_unlock(&arg->dst_task->pi_lock);
3232 raw_spin_unlock(&arg->src_task->pi_lock);
3233
3234 return ret;
3235 }
3236
3237 /*
3238 * Cross migrate two tasks
3239 */
migrate_swap(struct task_struct * cur,struct task_struct * p,int target_cpu,int curr_cpu)3240 int migrate_swap(struct task_struct *cur, struct task_struct *p,
3241 int target_cpu, int curr_cpu)
3242 {
3243 struct migration_swap_arg arg;
3244 int ret = -EINVAL;
3245
3246 arg = (struct migration_swap_arg){
3247 .src_task = cur,
3248 .src_cpu = curr_cpu,
3249 .dst_task = p,
3250 .dst_cpu = target_cpu,
3251 };
3252
3253 if (arg.src_cpu == arg.dst_cpu)
3254 goto out;
3255
3256 /*
3257 * These three tests are all lockless; this is OK since all of them
3258 * will be re-checked with proper locks held further down the line.
3259 */
3260 if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
3261 goto out;
3262
3263 if (!cpumask_test_cpu(arg.dst_cpu, arg.src_task->cpus_ptr))
3264 goto out;
3265
3266 if (!cpumask_test_cpu(arg.src_cpu, arg.dst_task->cpus_ptr))
3267 goto out;
3268
3269 trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
3270 ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
3271
3272 out:
3273 return ret;
3274 }
3275 #endif /* CONFIG_NUMA_BALANCING */
3276
3277 /*
3278 * wait_task_inactive - wait for a thread to unschedule.
3279 *
3280 * Wait for the thread to block in any of the states set in @match_state.
3281 * If it changes, i.e. @p might have woken up, then return zero. When we
3282 * succeed in waiting for @p to be off its CPU, we return a positive number
3283 * (its total switch count). If a second call a short while later returns the
3284 * same number, the caller can be sure that @p has remained unscheduled the
3285 * whole time.
3286 *
3287 * The caller must ensure that the task *will* unschedule sometime soon,
3288 * else this function might spin for a *long* time. This function can't
3289 * be called with interrupts off, or it may introduce deadlock with
3290 * smp_call_function() if an IPI is sent by the same process we are
3291 * waiting to become inactive.
3292 */
wait_task_inactive(struct task_struct * p,unsigned int match_state)3293 unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state)
3294 {
3295 int running, queued;
3296 struct rq_flags rf;
3297 unsigned long ncsw;
3298 struct rq *rq;
3299
3300 for (;;) {
3301 /*
3302 * We do the initial early heuristics without holding
3303 * any task-queue locks at all. We'll only try to get
3304 * the runqueue lock when things look like they will
3305 * work out!
3306 */
3307 rq = task_rq(p);
3308
3309 /*
3310 * If the task is actively running on another CPU
3311 * still, just relax and busy-wait without holding
3312 * any locks.
3313 *
3314 * NOTE! Since we don't hold any locks, it's not
3315 * even sure that "rq" stays as the right runqueue!
3316 * But we don't care, since "task_on_cpu()" will
3317 * return false if the runqueue has changed and p
3318 * is actually now running somewhere else!
3319 */
3320 while (task_on_cpu(rq, p)) {
3321 if (!(READ_ONCE(p->__state) & match_state))
3322 return 0;
3323 cpu_relax();
3324 }
3325
3326 /*
3327 * Ok, time to look more closely! We need the rq
3328 * lock now, to be *sure*. If we're wrong, we'll
3329 * just go back and repeat.
3330 */
3331 rq = task_rq_lock(p, &rf);
3332 trace_sched_wait_task(p);
3333 running = task_on_cpu(rq, p);
3334 queued = task_on_rq_queued(p);
3335 ncsw = 0;
3336 if (READ_ONCE(p->__state) & match_state)
3337 ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
3338 task_rq_unlock(rq, p, &rf);
3339
3340 /*
3341 * If it changed from the expected state, bail out now.
3342 */
3343 if (unlikely(!ncsw))
3344 break;
3345
3346 /*
3347 * Was it really running after all now that we
3348 * checked with the proper locks actually held?
3349 *
3350 * Oops. Go back and try again..
3351 */
3352 if (unlikely(running)) {
3353 cpu_relax();
3354 continue;
3355 }
3356
3357 /*
3358 * It's not enough that it's not actively running,
3359 * it must be off the runqueue _entirely_, and not
3360 * preempted!
3361 *
3362 * So if it was still runnable (but just not actively
3363 * running right now), it's preempted, and we should
3364 * yield - it could be a while.
3365 */
3366 if (unlikely(queued)) {
3367 ktime_t to = NSEC_PER_SEC / HZ;
3368
3369 set_current_state(TASK_UNINTERRUPTIBLE);
3370 schedule_hrtimeout(&to, HRTIMER_MODE_REL_HARD);
3371 continue;
3372 }
3373
3374 /*
3375 * Ahh, all good. It wasn't running, and it wasn't
3376 * runnable, which means that it will never become
3377 * running in the future either. We're all done!
3378 */
3379 break;
3380 }
3381
3382 return ncsw;
3383 }
3384
3385 /***
3386 * kick_process - kick a running thread to enter/exit the kernel
3387 * @p: the to-be-kicked thread
3388 *
3389 * Cause a process which is running on another CPU to enter
3390 * kernel-mode, without any delay. (to get signals handled.)
3391 *
3392 * NOTE: this function doesn't have to take the runqueue lock,
3393 * because all it wants to ensure is that the remote task enters
3394 * the kernel. If the IPI races and the task has been migrated
3395 * to another CPU then no harm is done and the purpose has been
3396 * achieved as well.
3397 */
kick_process(struct task_struct * p)3398 void kick_process(struct task_struct *p)
3399 {
3400 int cpu;
3401
3402 preempt_disable();
3403 cpu = task_cpu(p);
3404 if ((cpu != smp_processor_id()) && task_curr(p))
3405 smp_send_reschedule(cpu);
3406 preempt_enable();
3407 }
3408 EXPORT_SYMBOL_GPL(kick_process);
3409
3410 /*
3411 * ->cpus_ptr is protected by both rq->lock and p->pi_lock
3412 *
3413 * A few notes on cpu_active vs cpu_online:
3414 *
3415 * - cpu_active must be a subset of cpu_online
3416 *
3417 * - on CPU-up we allow per-CPU kthreads on the online && !active CPU,
3418 * see __set_cpus_allowed_ptr(). At this point the newly online
3419 * CPU isn't yet part of the sched domains, and balancing will not
3420 * see it.
3421 *
3422 * - on CPU-down we clear cpu_active() to mask the sched domains and
3423 * avoid the load balancer to place new tasks on the to be removed
3424 * CPU. Existing tasks will remain running there and will be taken
3425 * off.
3426 *
3427 * This means that fallback selection must not select !active CPUs.
3428 * And can assume that any active CPU must be online. Conversely
3429 * select_task_rq() below may allow selection of !active CPUs in order
3430 * to satisfy the above rules.
3431 */
select_fallback_rq(int cpu,struct task_struct * p)3432 static int select_fallback_rq(int cpu, struct task_struct *p)
3433 {
3434 int nid = cpu_to_node(cpu);
3435 const struct cpumask *nodemask = NULL;
3436 enum { cpuset, possible, fail } state = cpuset;
3437 int dest_cpu;
3438
3439 /*
3440 * If the node that the CPU is on has been offlined, cpu_to_node()
3441 * will return -1. There is no CPU on the node, and we should
3442 * select the CPU on the other node.
3443 */
3444 if (nid != -1) {
3445 nodemask = cpumask_of_node(nid);
3446
3447 /* Look for allowed, online CPU in same node. */
3448 for_each_cpu(dest_cpu, nodemask) {
3449 if (is_cpu_allowed(p, dest_cpu))
3450 return dest_cpu;
3451 }
3452 }
3453
3454 for (;;) {
3455 /* Any allowed, online CPU? */
3456 for_each_cpu(dest_cpu, p->cpus_ptr) {
3457 if (!is_cpu_allowed(p, dest_cpu))
3458 continue;
3459
3460 goto out;
3461 }
3462
3463 /* No more Mr. Nice Guy. */
3464 switch (state) {
3465 case cpuset:
3466 if (cpuset_cpus_allowed_fallback(p)) {
3467 state = possible;
3468 break;
3469 }
3470 fallthrough;
3471 case possible:
3472 /*
3473 * XXX When called from select_task_rq() we only
3474 * hold p->pi_lock and again violate locking order.
3475 *
3476 * More yuck to audit.
3477 */
3478 do_set_cpus_allowed(p, task_cpu_possible_mask(p));
3479 state = fail;
3480 break;
3481 case fail:
3482 BUG();
3483 break;
3484 }
3485 }
3486
3487 out:
3488 if (state != cpuset) {
3489 /*
3490 * Don't tell them about moving exiting tasks or
3491 * kernel threads (both mm NULL), since they never
3492 * leave kernel.
3493 */
3494 if (p->mm && printk_ratelimit()) {
3495 printk_deferred("process %d (%s) no longer affine to cpu%d\n",
3496 task_pid_nr(p), p->comm, cpu);
3497 }
3498 }
3499
3500 return dest_cpu;
3501 }
3502
3503 /*
3504 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_ptr is stable.
3505 */
3506 static inline
select_task_rq(struct task_struct * p,int cpu,int wake_flags)3507 int select_task_rq(struct task_struct *p, int cpu, int wake_flags)
3508 {
3509 lockdep_assert_held(&p->pi_lock);
3510
3511 if (p->nr_cpus_allowed > 1 && !is_migration_disabled(p))
3512 cpu = p->sched_class->select_task_rq(p, cpu, wake_flags);
3513 else
3514 cpu = cpumask_any(p->cpus_ptr);
3515
3516 /*
3517 * In order not to call set_task_cpu() on a blocking task we need
3518 * to rely on ttwu() to place the task on a valid ->cpus_ptr
3519 * CPU.
3520 *
3521 * Since this is common to all placement strategies, this lives here.
3522 *
3523 * [ this allows ->select_task() to simply return task_cpu(p) and
3524 * not worry about this generic constraint ]
3525 */
3526 if (unlikely(!is_cpu_allowed(p, cpu)))
3527 cpu = select_fallback_rq(task_cpu(p), p);
3528
3529 return cpu;
3530 }
3531
sched_set_stop_task(int cpu,struct task_struct * stop)3532 void sched_set_stop_task(int cpu, struct task_struct *stop)
3533 {
3534 static struct lock_class_key stop_pi_lock;
3535 struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
3536 struct task_struct *old_stop = cpu_rq(cpu)->stop;
3537
3538 if (stop) {
3539 /*
3540 * Make it appear like a SCHED_FIFO task, its something
3541 * userspace knows about and won't get confused about.
3542 *
3543 * Also, it will make PI more or less work without too
3544 * much confusion -- but then, stop work should not
3545 * rely on PI working anyway.
3546 */
3547 sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m);
3548
3549 stop->sched_class = &stop_sched_class;
3550
3551 /*
3552 * The PI code calls rt_mutex_setprio() with ->pi_lock held to
3553 * adjust the effective priority of a task. As a result,
3554 * rt_mutex_setprio() can trigger (RT) balancing operations,
3555 * which can then trigger wakeups of the stop thread to push
3556 * around the current task.
3557 *
3558 * The stop task itself will never be part of the PI-chain, it
3559 * never blocks, therefore that ->pi_lock recursion is safe.
3560 * Tell lockdep about this by placing the stop->pi_lock in its
3561 * own class.
3562 */
3563 lockdep_set_class(&stop->pi_lock, &stop_pi_lock);
3564 }
3565
3566 cpu_rq(cpu)->stop = stop;
3567
3568 if (old_stop) {
3569 /*
3570 * Reset it back to a normal scheduling class so that
3571 * it can die in pieces.
3572 */
3573 old_stop->sched_class = &rt_sched_class;
3574 }
3575 }
3576
3577 #else /* CONFIG_SMP */
3578
__set_cpus_allowed_ptr(struct task_struct * p,const struct cpumask * new_mask,u32 flags)3579 static inline int __set_cpus_allowed_ptr(struct task_struct *p,
3580 const struct cpumask *new_mask,
3581 u32 flags)
3582 {
3583 return set_cpus_allowed_ptr(p, new_mask);
3584 }
3585
migrate_disable_switch(struct rq * rq,struct task_struct * p)3586 static inline void migrate_disable_switch(struct rq *rq, struct task_struct *p) { }
3587
rq_has_pinned_tasks(struct rq * rq)3588 static inline bool rq_has_pinned_tasks(struct rq *rq)
3589 {
3590 return false;
3591 }
3592
3593 #endif /* !CONFIG_SMP */
3594
3595 static void
ttwu_stat(struct task_struct * p,int cpu,int wake_flags)3596 ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
3597 {
3598 struct rq *rq;
3599
3600 if (!schedstat_enabled())
3601 return;
3602
3603 rq = this_rq();
3604
3605 #ifdef CONFIG_SMP
3606 if (cpu == rq->cpu) {
3607 __schedstat_inc(rq->ttwu_local);
3608 __schedstat_inc(p->stats.nr_wakeups_local);
3609 } else {
3610 struct sched_domain *sd;
3611
3612 __schedstat_inc(p->stats.nr_wakeups_remote);
3613 rcu_read_lock();
3614 for_each_domain(rq->cpu, sd) {
3615 if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
3616 __schedstat_inc(sd->ttwu_wake_remote);
3617 break;
3618 }
3619 }
3620 rcu_read_unlock();
3621 }
3622
3623 if (wake_flags & WF_MIGRATED)
3624 __schedstat_inc(p->stats.nr_wakeups_migrate);
3625 #endif /* CONFIG_SMP */
3626
3627 __schedstat_inc(rq->ttwu_count);
3628 __schedstat_inc(p->stats.nr_wakeups);
3629
3630 if (wake_flags & WF_SYNC)
3631 __schedstat_inc(p->stats.nr_wakeups_sync);
3632 }
3633
3634 /*
3635 * Mark the task runnable and perform wakeup-preemption.
3636 */
ttwu_do_wakeup(struct rq * rq,struct task_struct * p,int wake_flags,struct rq_flags * rf)3637 static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags,
3638 struct rq_flags *rf)
3639 {
3640 check_preempt_curr(rq, p, wake_flags);
3641 WRITE_ONCE(p->__state, TASK_RUNNING);
3642 trace_sched_wakeup(p);
3643
3644 #ifdef CONFIG_SMP
3645 if (p->sched_class->task_woken) {
3646 /*
3647 * Our task @p is fully woken up and running; so it's safe to
3648 * drop the rq->lock, hereafter rq is only used for statistics.
3649 */
3650 rq_unpin_lock(rq, rf);
3651 p->sched_class->task_woken(rq, p);
3652 rq_repin_lock(rq, rf);
3653 }
3654
3655 if (rq->idle_stamp) {
3656 u64 delta = rq_clock(rq) - rq->idle_stamp;
3657 u64 max = 2*rq->max_idle_balance_cost;
3658
3659 update_avg(&rq->avg_idle, delta);
3660
3661 if (rq->avg_idle > max)
3662 rq->avg_idle = max;
3663
3664 rq->wake_stamp = jiffies;
3665 rq->wake_avg_idle = rq->avg_idle / 2;
3666
3667 rq->idle_stamp = 0;
3668 }
3669 #endif
3670 }
3671
3672 static void
ttwu_do_activate(struct rq * rq,struct task_struct * p,int wake_flags,struct rq_flags * rf)3673 ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
3674 struct rq_flags *rf)
3675 {
3676 int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
3677
3678 lockdep_assert_rq_held(rq);
3679
3680 if (p->sched_contributes_to_load)
3681 rq->nr_uninterruptible--;
3682
3683 #ifdef CONFIG_SMP
3684 if (wake_flags & WF_MIGRATED)
3685 en_flags |= ENQUEUE_MIGRATED;
3686 else
3687 #endif
3688 if (p->in_iowait) {
3689 delayacct_blkio_end(p);
3690 atomic_dec(&task_rq(p)->nr_iowait);
3691 }
3692
3693 activate_task(rq, p, en_flags);
3694 ttwu_do_wakeup(rq, p, wake_flags, rf);
3695 }
3696
3697 /*
3698 * Consider @p being inside a wait loop:
3699 *
3700 * for (;;) {
3701 * set_current_state(TASK_UNINTERRUPTIBLE);
3702 *
3703 * if (CONDITION)
3704 * break;
3705 *
3706 * schedule();
3707 * }
3708 * __set_current_state(TASK_RUNNING);
3709 *
3710 * between set_current_state() and schedule(). In this case @p is still
3711 * runnable, so all that needs doing is change p->state back to TASK_RUNNING in
3712 * an atomic manner.
3713 *
3714 * By taking task_rq(p)->lock we serialize against schedule(), if @p->on_rq
3715 * then schedule() must still happen and p->state can be changed to
3716 * TASK_RUNNING. Otherwise we lost the race, schedule() has happened, and we
3717 * need to do a full wakeup with enqueue.
3718 *
3719 * Returns: %true when the wakeup is done,
3720 * %false otherwise.
3721 */
ttwu_runnable(struct task_struct * p,int wake_flags)3722 static int ttwu_runnable(struct task_struct *p, int wake_flags)
3723 {
3724 struct rq_flags rf;
3725 struct rq *rq;
3726 int ret = 0;
3727
3728 rq = __task_rq_lock(p, &rf);
3729 if (task_on_rq_queued(p)) {
3730 /* check_preempt_curr() may use rq clock */
3731 update_rq_clock(rq);
3732 ttwu_do_wakeup(rq, p, wake_flags, &rf);
3733 ret = 1;
3734 }
3735 __task_rq_unlock(rq, &rf);
3736
3737 return ret;
3738 }
3739
3740 #ifdef CONFIG_SMP
sched_ttwu_pending(void * arg)3741 void sched_ttwu_pending(void *arg)
3742 {
3743 struct llist_node *llist = arg;
3744 struct rq *rq = this_rq();
3745 struct task_struct *p, *t;
3746 struct rq_flags rf;
3747
3748 if (!llist)
3749 return;
3750
3751 /*
3752 * rq::ttwu_pending racy indication of out-standing wakeups.
3753 * Races such that false-negatives are possible, since they
3754 * are shorter lived that false-positives would be.
3755 */
3756 WRITE_ONCE(rq->ttwu_pending, 0);
3757
3758 rq_lock_irqsave(rq, &rf);
3759 update_rq_clock(rq);
3760
3761 llist_for_each_entry_safe(p, t, llist, wake_entry.llist) {
3762 if (WARN_ON_ONCE(p->on_cpu))
3763 smp_cond_load_acquire(&p->on_cpu, !VAL);
3764
3765 if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq)))
3766 set_task_cpu(p, cpu_of(rq));
3767
3768 ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf);
3769 }
3770
3771 rq_unlock_irqrestore(rq, &rf);
3772 }
3773
send_call_function_single_ipi(int cpu)3774 void send_call_function_single_ipi(int cpu)
3775 {
3776 struct rq *rq = cpu_rq(cpu);
3777
3778 if (!set_nr_if_polling(rq->idle))
3779 arch_send_call_function_single_ipi(cpu);
3780 else
3781 trace_sched_wake_idle_without_ipi(cpu);
3782 }
3783
3784 /*
3785 * Queue a task on the target CPUs wake_list and wake the CPU via IPI if
3786 * necessary. The wakee CPU on receipt of the IPI will queue the task
3787 * via sched_ttwu_wakeup() for activation so the wakee incurs the cost
3788 * of the wakeup instead of the waker.
3789 */
__ttwu_queue_wakelist(struct task_struct * p,int cpu,int wake_flags)3790 static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
3791 {
3792 struct rq *rq = cpu_rq(cpu);
3793
3794 p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
3795
3796 WRITE_ONCE(rq->ttwu_pending, 1);
3797 __smp_call_single_queue(cpu, &p->wake_entry.llist);
3798 }
3799
wake_up_if_idle(int cpu)3800 void wake_up_if_idle(int cpu)
3801 {
3802 struct rq *rq = cpu_rq(cpu);
3803 struct rq_flags rf;
3804
3805 rcu_read_lock();
3806
3807 if (!is_idle_task(rcu_dereference(rq->curr)))
3808 goto out;
3809
3810 rq_lock_irqsave(rq, &rf);
3811 if (is_idle_task(rq->curr))
3812 resched_curr(rq);
3813 /* Else CPU is not idle, do nothing here: */
3814 rq_unlock_irqrestore(rq, &rf);
3815
3816 out:
3817 rcu_read_unlock();
3818 }
3819
cpus_share_cache(int this_cpu,int that_cpu)3820 bool cpus_share_cache(int this_cpu, int that_cpu)
3821 {
3822 if (this_cpu == that_cpu)
3823 return true;
3824
3825 return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
3826 }
3827
ttwu_queue_cond(struct task_struct * p,int cpu)3828 static inline bool ttwu_queue_cond(struct task_struct *p, int cpu)
3829 {
3830 /*
3831 * Do not complicate things with the async wake_list while the CPU is
3832 * in hotplug state.
3833 */
3834 if (!cpu_active(cpu))
3835 return false;
3836
3837 /* Ensure the task will still be allowed to run on the CPU. */
3838 if (!cpumask_test_cpu(cpu, p->cpus_ptr))
3839 return false;
3840
3841 /*
3842 * If the CPU does not share cache, then queue the task on the
3843 * remote rqs wakelist to avoid accessing remote data.
3844 */
3845 if (!cpus_share_cache(smp_processor_id(), cpu))
3846 return true;
3847
3848 if (cpu == smp_processor_id())
3849 return false;
3850
3851 /*
3852 * If the wakee cpu is idle, or the task is descheduling and the
3853 * only running task on the CPU, then use the wakelist to offload
3854 * the task activation to the idle (or soon-to-be-idle) CPU as
3855 * the current CPU is likely busy. nr_running is checked to
3856 * avoid unnecessary task stacking.
3857 *
3858 * Note that we can only get here with (wakee) p->on_rq=0,
3859 * p->on_cpu can be whatever, we've done the dequeue, so
3860 * the wakee has been accounted out of ->nr_running.
3861 */
3862 if (!cpu_rq(cpu)->nr_running)
3863 return true;
3864
3865 return false;
3866 }
3867
ttwu_queue_wakelist(struct task_struct * p,int cpu,int wake_flags)3868 static bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
3869 {
3870 if (sched_feat(TTWU_QUEUE) && ttwu_queue_cond(p, cpu)) {
3871 sched_clock_cpu(cpu); /* Sync clocks across CPUs */
3872 __ttwu_queue_wakelist(p, cpu, wake_flags);
3873 return true;
3874 }
3875
3876 return false;
3877 }
3878
3879 #else /* !CONFIG_SMP */
3880
ttwu_queue_wakelist(struct task_struct * p,int cpu,int wake_flags)3881 static inline bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
3882 {
3883 return false;
3884 }
3885
3886 #endif /* CONFIG_SMP */
3887
ttwu_queue(struct task_struct * p,int cpu,int wake_flags)3888 static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
3889 {
3890 struct rq *rq = cpu_rq(cpu);
3891 struct rq_flags rf;
3892
3893 if (ttwu_queue_wakelist(p, cpu, wake_flags))
3894 return;
3895
3896 rq_lock(rq, &rf);
3897 update_rq_clock(rq);
3898 ttwu_do_activate(rq, p, wake_flags, &rf);
3899 rq_unlock(rq, &rf);
3900 }
3901
3902 /*
3903 * Invoked from try_to_wake_up() to check whether the task can be woken up.
3904 *
3905 * The caller holds p::pi_lock if p != current or has preemption
3906 * disabled when p == current.
3907 *
3908 * The rules of PREEMPT_RT saved_state:
3909 *
3910 * The related locking code always holds p::pi_lock when updating
3911 * p::saved_state, which means the code is fully serialized in both cases.
3912 *
3913 * The lock wait and lock wakeups happen via TASK_RTLOCK_WAIT. No other
3914 * bits set. This allows to distinguish all wakeup scenarios.
3915 */
3916 static __always_inline
ttwu_state_match(struct task_struct * p,unsigned int state,int * success)3917 bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success)
3918 {
3919 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) {
3920 WARN_ON_ONCE((state & TASK_RTLOCK_WAIT) &&
3921 state != TASK_RTLOCK_WAIT);
3922 }
3923
3924 if (READ_ONCE(p->__state) & state) {
3925 *success = 1;
3926 return true;
3927 }
3928
3929 #ifdef CONFIG_PREEMPT_RT
3930 /*
3931 * Saved state preserves the task state across blocking on
3932 * an RT lock. If the state matches, set p::saved_state to
3933 * TASK_RUNNING, but do not wake the task because it waits
3934 * for a lock wakeup. Also indicate success because from
3935 * the regular waker's point of view this has succeeded.
3936 *
3937 * After acquiring the lock the task will restore p::__state
3938 * from p::saved_state which ensures that the regular
3939 * wakeup is not lost. The restore will also set
3940 * p::saved_state to TASK_RUNNING so any further tests will
3941 * not result in false positives vs. @success
3942 */
3943 if (p->saved_state & state) {
3944 p->saved_state = TASK_RUNNING;
3945 *success = 1;
3946 }
3947 #endif
3948 return false;
3949 }
3950
3951 /*
3952 * Notes on Program-Order guarantees on SMP systems.
3953 *
3954 * MIGRATION
3955 *
3956 * The basic program-order guarantee on SMP systems is that when a task [t]
3957 * migrates, all its activity on its old CPU [c0] happens-before any subsequent
3958 * execution on its new CPU [c1].
3959 *
3960 * For migration (of runnable tasks) this is provided by the following means:
3961 *
3962 * A) UNLOCK of the rq(c0)->lock scheduling out task t
3963 * B) migration for t is required to synchronize *both* rq(c0)->lock and
3964 * rq(c1)->lock (if not at the same time, then in that order).
3965 * C) LOCK of the rq(c1)->lock scheduling in task
3966 *
3967 * Release/acquire chaining guarantees that B happens after A and C after B.
3968 * Note: the CPU doing B need not be c0 or c1
3969 *
3970 * Example:
3971 *
3972 * CPU0 CPU1 CPU2
3973 *
3974 * LOCK rq(0)->lock
3975 * sched-out X
3976 * sched-in Y
3977 * UNLOCK rq(0)->lock
3978 *
3979 * LOCK rq(0)->lock // orders against CPU0
3980 * dequeue X
3981 * UNLOCK rq(0)->lock
3982 *
3983 * LOCK rq(1)->lock
3984 * enqueue X
3985 * UNLOCK rq(1)->lock
3986 *
3987 * LOCK rq(1)->lock // orders against CPU2
3988 * sched-out Z
3989 * sched-in X
3990 * UNLOCK rq(1)->lock
3991 *
3992 *
3993 * BLOCKING -- aka. SLEEP + WAKEUP
3994 *
3995 * For blocking we (obviously) need to provide the same guarantee as for
3996 * migration. However the means are completely different as there is no lock
3997 * chain to provide order. Instead we do:
3998 *
3999 * 1) smp_store_release(X->on_cpu, 0) -- finish_task()
4000 * 2) smp_cond_load_acquire(!X->on_cpu) -- try_to_wake_up()
4001 *
4002 * Example:
4003 *
4004 * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule)
4005 *
4006 * LOCK rq(0)->lock LOCK X->pi_lock
4007 * dequeue X
4008 * sched-out X
4009 * smp_store_release(X->on_cpu, 0);
4010 *
4011 * smp_cond_load_acquire(&X->on_cpu, !VAL);
4012 * X->state = WAKING
4013 * set_task_cpu(X,2)
4014 *
4015 * LOCK rq(2)->lock
4016 * enqueue X
4017 * X->state = RUNNING
4018 * UNLOCK rq(2)->lock
4019 *
4020 * LOCK rq(2)->lock // orders against CPU1
4021 * sched-out Z
4022 * sched-in X
4023 * UNLOCK rq(2)->lock
4024 *
4025 * UNLOCK X->pi_lock
4026 * UNLOCK rq(0)->lock
4027 *
4028 *
4029 * However, for wakeups there is a second guarantee we must provide, namely we
4030 * must ensure that CONDITION=1 done by the caller can not be reordered with
4031 * accesses to the task state; see try_to_wake_up() and set_current_state().
4032 */
4033
4034 /**
4035 * try_to_wake_up - wake up a thread
4036 * @p: the thread to be awakened
4037 * @state: the mask of task states that can be woken
4038 * @wake_flags: wake modifier flags (WF_*)
4039 *
4040 * Conceptually does:
4041 *
4042 * If (@state & @p->state) @p->state = TASK_RUNNING.
4043 *
4044 * If the task was not queued/runnable, also place it back on a runqueue.
4045 *
4046 * This function is atomic against schedule() which would dequeue the task.
4047 *
4048 * It issues a full memory barrier before accessing @p->state, see the comment
4049 * with set_current_state().
4050 *
4051 * Uses p->pi_lock to serialize against concurrent wake-ups.
4052 *
4053 * Relies on p->pi_lock stabilizing:
4054 * - p->sched_class
4055 * - p->cpus_ptr
4056 * - p->sched_task_group
4057 * in order to do migration, see its use of select_task_rq()/set_task_cpu().
4058 *
4059 * Tries really hard to only take one task_rq(p)->lock for performance.
4060 * Takes rq->lock in:
4061 * - ttwu_runnable() -- old rq, unavoidable, see comment there;
4062 * - ttwu_queue() -- new rq, for enqueue of the task;
4063 * - psi_ttwu_dequeue() -- much sadness :-( accounting will kill us.
4064 *
4065 * As a consequence we race really badly with just about everything. See the
4066 * many memory barriers and their comments for details.
4067 *
4068 * Return: %true if @p->state changes (an actual wakeup was done),
4069 * %false otherwise.
4070 */
4071 static int
try_to_wake_up(struct task_struct * p,unsigned int state,int wake_flags)4072 try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
4073 {
4074 unsigned long flags;
4075 int cpu, success = 0;
4076
4077 preempt_disable();
4078 if (p == current) {
4079 /*
4080 * We're waking current, this means 'p->on_rq' and 'task_cpu(p)
4081 * == smp_processor_id()'. Together this means we can special
4082 * case the whole 'p->on_rq && ttwu_runnable()' case below
4083 * without taking any locks.
4084 *
4085 * In particular:
4086 * - we rely on Program-Order guarantees for all the ordering,
4087 * - we're serialized against set_special_state() by virtue of
4088 * it disabling IRQs (this allows not taking ->pi_lock).
4089 */
4090 if (!ttwu_state_match(p, state, &success))
4091 goto out;
4092
4093 trace_sched_waking(p);
4094 WRITE_ONCE(p->__state, TASK_RUNNING);
4095 trace_sched_wakeup(p);
4096 goto out;
4097 }
4098
4099 /*
4100 * If we are going to wake up a thread waiting for CONDITION we
4101 * need to ensure that CONDITION=1 done by the caller can not be
4102 * reordered with p->state check below. This pairs with smp_store_mb()
4103 * in set_current_state() that the waiting thread does.
4104 */
4105 raw_spin_lock_irqsave(&p->pi_lock, flags);
4106 smp_mb__after_spinlock();
4107 if (!ttwu_state_match(p, state, &success))
4108 goto unlock;
4109
4110 trace_sched_waking(p);
4111
4112 /*
4113 * Ensure we load p->on_rq _after_ p->state, otherwise it would
4114 * be possible to, falsely, observe p->on_rq == 0 and get stuck
4115 * in smp_cond_load_acquire() below.
4116 *
4117 * sched_ttwu_pending() try_to_wake_up()
4118 * STORE p->on_rq = 1 LOAD p->state
4119 * UNLOCK rq->lock
4120 *
4121 * __schedule() (switch to task 'p')
4122 * LOCK rq->lock smp_rmb();
4123 * smp_mb__after_spinlock();
4124 * UNLOCK rq->lock
4125 *
4126 * [task p]
4127 * STORE p->state = UNINTERRUPTIBLE LOAD p->on_rq
4128 *
4129 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
4130 * __schedule(). See the comment for smp_mb__after_spinlock().
4131 *
4132 * A similar smb_rmb() lives in try_invoke_on_locked_down_task().
4133 */
4134 smp_rmb();
4135 if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags))
4136 goto unlock;
4137
4138 #ifdef CONFIG_SMP
4139 /*
4140 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
4141 * possible to, falsely, observe p->on_cpu == 0.
4142 *
4143 * One must be running (->on_cpu == 1) in order to remove oneself
4144 * from the runqueue.
4145 *
4146 * __schedule() (switch to task 'p') try_to_wake_up()
4147 * STORE p->on_cpu = 1 LOAD p->on_rq
4148 * UNLOCK rq->lock
4149 *
4150 * __schedule() (put 'p' to sleep)
4151 * LOCK rq->lock smp_rmb();
4152 * smp_mb__after_spinlock();
4153 * STORE p->on_rq = 0 LOAD p->on_cpu
4154 *
4155 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
4156 * __schedule(). See the comment for smp_mb__after_spinlock().
4157 *
4158 * Form a control-dep-acquire with p->on_rq == 0 above, to ensure
4159 * schedule()'s deactivate_task() has 'happened' and p will no longer
4160 * care about it's own p->state. See the comment in __schedule().
4161 */
4162 smp_acquire__after_ctrl_dep();
4163
4164 /*
4165 * We're doing the wakeup (@success == 1), they did a dequeue (p->on_rq
4166 * == 0), which means we need to do an enqueue, change p->state to
4167 * TASK_WAKING such that we can unlock p->pi_lock before doing the
4168 * enqueue, such as ttwu_queue_wakelist().
4169 */
4170 WRITE_ONCE(p->__state, TASK_WAKING);
4171
4172 /*
4173 * If the owning (remote) CPU is still in the middle of schedule() with
4174 * this task as prev, considering queueing p on the remote CPUs wake_list
4175 * which potentially sends an IPI instead of spinning on p->on_cpu to
4176 * let the waker make forward progress. This is safe because IRQs are
4177 * disabled and the IPI will deliver after on_cpu is cleared.
4178 *
4179 * Ensure we load task_cpu(p) after p->on_cpu:
4180 *
4181 * set_task_cpu(p, cpu);
4182 * STORE p->cpu = @cpu
4183 * __schedule() (switch to task 'p')
4184 * LOCK rq->lock
4185 * smp_mb__after_spin_lock() smp_cond_load_acquire(&p->on_cpu)
4186 * STORE p->on_cpu = 1 LOAD p->cpu
4187 *
4188 * to ensure we observe the correct CPU on which the task is currently
4189 * scheduling.
4190 */
4191 if (smp_load_acquire(&p->on_cpu) &&
4192 ttwu_queue_wakelist(p, task_cpu(p), wake_flags))
4193 goto unlock;
4194
4195 /*
4196 * If the owning (remote) CPU is still in the middle of schedule() with
4197 * this task as prev, wait until it's done referencing the task.
4198 *
4199 * Pairs with the smp_store_release() in finish_task().
4200 *
4201 * This ensures that tasks getting woken will be fully ordered against
4202 * their previous state and preserve Program Order.
4203 */
4204 smp_cond_load_acquire(&p->on_cpu, !VAL);
4205
4206 cpu = select_task_rq(p, p->wake_cpu, wake_flags | WF_TTWU);
4207 if (task_cpu(p) != cpu) {
4208 if (p->in_iowait) {
4209 delayacct_blkio_end(p);
4210 atomic_dec(&task_rq(p)->nr_iowait);
4211 }
4212
4213 wake_flags |= WF_MIGRATED;
4214 psi_ttwu_dequeue(p);
4215 set_task_cpu(p, cpu);
4216 }
4217 #else
4218 cpu = task_cpu(p);
4219 #endif /* CONFIG_SMP */
4220
4221 ttwu_queue(p, cpu, wake_flags);
4222 unlock:
4223 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4224 out:
4225 if (success)
4226 ttwu_stat(p, task_cpu(p), wake_flags);
4227 preempt_enable();
4228
4229 return success;
4230 }
4231
__task_needs_rq_lock(struct task_struct * p)4232 static bool __task_needs_rq_lock(struct task_struct *p)
4233 {
4234 unsigned int state = READ_ONCE(p->__state);
4235
4236 /*
4237 * Since pi->lock blocks try_to_wake_up(), we don't need rq->lock when
4238 * the task is blocked. Make sure to check @state since ttwu() can drop
4239 * locks at the end, see ttwu_queue_wakelist().
4240 */
4241 if (state == TASK_RUNNING || state == TASK_WAKING)
4242 return true;
4243
4244 /*
4245 * Ensure we load p->on_rq after p->__state, otherwise it would be
4246 * possible to, falsely, observe p->on_rq == 0.
4247 *
4248 * See try_to_wake_up() for a longer comment.
4249 */
4250 smp_rmb();
4251 if (p->on_rq)
4252 return true;
4253
4254 #ifdef CONFIG_SMP
4255 /*
4256 * Ensure the task has finished __schedule() and will not be referenced
4257 * anymore. Again, see try_to_wake_up() for a longer comment.
4258 */
4259 smp_rmb();
4260 smp_cond_load_acquire(&p->on_cpu, !VAL);
4261 #endif
4262
4263 return false;
4264 }
4265
4266 /**
4267 * task_call_func - Invoke a function on task in fixed state
4268 * @p: Process for which the function is to be invoked, can be @current.
4269 * @func: Function to invoke.
4270 * @arg: Argument to function.
4271 *
4272 * Fix the task in it's current state by avoiding wakeups and or rq operations
4273 * and call @func(@arg) on it. This function can use ->on_rq and task_curr()
4274 * to work out what the state is, if required. Given that @func can be invoked
4275 * with a runqueue lock held, it had better be quite lightweight.
4276 *
4277 * Returns:
4278 * Whatever @func returns
4279 */
task_call_func(struct task_struct * p,task_call_f func,void * arg)4280 int task_call_func(struct task_struct *p, task_call_f func, void *arg)
4281 {
4282 struct rq *rq = NULL;
4283 struct rq_flags rf;
4284 int ret;
4285
4286 raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
4287
4288 if (__task_needs_rq_lock(p))
4289 rq = __task_rq_lock(p, &rf);
4290
4291 /*
4292 * At this point the task is pinned; either:
4293 * - blocked and we're holding off wakeups (pi->lock)
4294 * - woken, and we're holding off enqueue (rq->lock)
4295 * - queued, and we're holding off schedule (rq->lock)
4296 * - running, and we're holding off de-schedule (rq->lock)
4297 *
4298 * The called function (@func) can use: task_curr(), p->on_rq and
4299 * p->__state to differentiate between these states.
4300 */
4301 ret = func(p, arg);
4302
4303 if (rq)
4304 rq_unlock(rq, &rf);
4305
4306 raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
4307 return ret;
4308 }
4309
4310 /**
4311 * cpu_curr_snapshot - Return a snapshot of the currently running task
4312 * @cpu: The CPU on which to snapshot the task.
4313 *
4314 * Returns the task_struct pointer of the task "currently" running on
4315 * the specified CPU. If the same task is running on that CPU throughout,
4316 * the return value will be a pointer to that task's task_struct structure.
4317 * If the CPU did any context switches even vaguely concurrently with the
4318 * execution of this function, the return value will be a pointer to the
4319 * task_struct structure of a randomly chosen task that was running on
4320 * that CPU somewhere around the time that this function was executing.
4321 *
4322 * If the specified CPU was offline, the return value is whatever it
4323 * is, perhaps a pointer to the task_struct structure of that CPU's idle
4324 * task, but there is no guarantee. Callers wishing a useful return
4325 * value must take some action to ensure that the specified CPU remains
4326 * online throughout.
4327 *
4328 * This function executes full memory barriers before and after fetching
4329 * the pointer, which permits the caller to confine this function's fetch
4330 * with respect to the caller's accesses to other shared variables.
4331 */
cpu_curr_snapshot(int cpu)4332 struct task_struct *cpu_curr_snapshot(int cpu)
4333 {
4334 struct task_struct *t;
4335
4336 smp_mb(); /* Pairing determined by caller's synchronization design. */
4337 t = rcu_dereference(cpu_curr(cpu));
4338 smp_mb(); /* Pairing determined by caller's synchronization design. */
4339 return t;
4340 }
4341
4342 /**
4343 * wake_up_process - Wake up a specific process
4344 * @p: The process to be woken up.
4345 *
4346 * Attempt to wake up the nominated process and move it to the set of runnable
4347 * processes.
4348 *
4349 * Return: 1 if the process was woken up, 0 if it was already running.
4350 *
4351 * This function executes a full memory barrier before accessing the task state.
4352 */
wake_up_process(struct task_struct * p)4353 int wake_up_process(struct task_struct *p)
4354 {
4355 return try_to_wake_up(p, TASK_NORMAL, 0);
4356 }
4357 EXPORT_SYMBOL(wake_up_process);
4358
wake_up_state(struct task_struct * p,unsigned int state)4359 int wake_up_state(struct task_struct *p, unsigned int state)
4360 {
4361 return try_to_wake_up(p, state, 0);
4362 }
4363
4364 /*
4365 * Perform scheduler related setup for a newly forked process p.
4366 * p is forked by current.
4367 *
4368 * __sched_fork() is basic setup used by init_idle() too:
4369 */
__sched_fork(unsigned long clone_flags,struct task_struct * p)4370 static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
4371 {
4372 p->on_rq = 0;
4373
4374 p->se.on_rq = 0;
4375 p->se.exec_start = 0;
4376 p->se.sum_exec_runtime = 0;
4377 p->se.prev_sum_exec_runtime = 0;
4378 p->se.nr_migrations = 0;
4379 p->se.vruntime = 0;
4380 INIT_LIST_HEAD(&p->se.group_node);
4381
4382 #ifdef CONFIG_FAIR_GROUP_SCHED
4383 p->se.cfs_rq = NULL;
4384 #endif
4385
4386 #ifdef CONFIG_SCHEDSTATS
4387 /* Even if schedstat is disabled, there should not be garbage */
4388 memset(&p->stats, 0, sizeof(p->stats));
4389 #endif
4390
4391 RB_CLEAR_NODE(&p->dl.rb_node);
4392 init_dl_task_timer(&p->dl);
4393 init_dl_inactive_task_timer(&p->dl);
4394 __dl_clear_params(p);
4395
4396 INIT_LIST_HEAD(&p->rt.run_list);
4397 p->rt.timeout = 0;
4398 p->rt.time_slice = sched_rr_timeslice;
4399 p->rt.on_rq = 0;
4400 p->rt.on_list = 0;
4401
4402 #ifdef CONFIG_PREEMPT_NOTIFIERS
4403 INIT_HLIST_HEAD(&p->preempt_notifiers);
4404 #endif
4405
4406 #ifdef CONFIG_COMPACTION
4407 p->capture_control = NULL;
4408 #endif
4409 init_numa_balancing(clone_flags, p);
4410 #ifdef CONFIG_SMP
4411 p->wake_entry.u_flags = CSD_TYPE_TTWU;
4412 p->migration_pending = NULL;
4413 #endif
4414 }
4415
4416 DEFINE_STATIC_KEY_FALSE(sched_numa_balancing);
4417
4418 #ifdef CONFIG_NUMA_BALANCING
4419
4420 int sysctl_numa_balancing_mode;
4421
__set_numabalancing_state(bool enabled)4422 static void __set_numabalancing_state(bool enabled)
4423 {
4424 if (enabled)
4425 static_branch_enable(&sched_numa_balancing);
4426 else
4427 static_branch_disable(&sched_numa_balancing);
4428 }
4429
set_numabalancing_state(bool enabled)4430 void set_numabalancing_state(bool enabled)
4431 {
4432 if (enabled)
4433 sysctl_numa_balancing_mode = NUMA_BALANCING_NORMAL;
4434 else
4435 sysctl_numa_balancing_mode = NUMA_BALANCING_DISABLED;
4436 __set_numabalancing_state(enabled);
4437 }
4438
4439 #ifdef CONFIG_PROC_SYSCTL
reset_memory_tiering(void)4440 static void reset_memory_tiering(void)
4441 {
4442 struct pglist_data *pgdat;
4443
4444 for_each_online_pgdat(pgdat) {
4445 pgdat->nbp_threshold = 0;
4446 pgdat->nbp_th_nr_cand = node_page_state(pgdat, PGPROMOTE_CANDIDATE);
4447 pgdat->nbp_th_start = jiffies_to_msecs(jiffies);
4448 }
4449 }
4450
sysctl_numa_balancing(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)4451 int sysctl_numa_balancing(struct ctl_table *table, int write,
4452 void *buffer, size_t *lenp, loff_t *ppos)
4453 {
4454 struct ctl_table t;
4455 int err;
4456 int state = sysctl_numa_balancing_mode;
4457
4458 if (write && !capable(CAP_SYS_ADMIN))
4459 return -EPERM;
4460
4461 t = *table;
4462 t.data = &state;
4463 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
4464 if (err < 0)
4465 return err;
4466 if (write) {
4467 if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) &&
4468 (state & NUMA_BALANCING_MEMORY_TIERING))
4469 reset_memory_tiering();
4470 sysctl_numa_balancing_mode = state;
4471 __set_numabalancing_state(state);
4472 }
4473 return err;
4474 }
4475 #endif
4476 #endif
4477
4478 #ifdef CONFIG_SCHEDSTATS
4479
4480 DEFINE_STATIC_KEY_FALSE(sched_schedstats);
4481
set_schedstats(bool enabled)4482 static void set_schedstats(bool enabled)
4483 {
4484 if (enabled)
4485 static_branch_enable(&sched_schedstats);
4486 else
4487 static_branch_disable(&sched_schedstats);
4488 }
4489
force_schedstat_enabled(void)4490 void force_schedstat_enabled(void)
4491 {
4492 if (!schedstat_enabled()) {
4493 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
4494 static_branch_enable(&sched_schedstats);
4495 }
4496 }
4497
setup_schedstats(char * str)4498 static int __init setup_schedstats(char *str)
4499 {
4500 int ret = 0;
4501 if (!str)
4502 goto out;
4503
4504 if (!strcmp(str, "enable")) {
4505 set_schedstats(true);
4506 ret = 1;
4507 } else if (!strcmp(str, "disable")) {
4508 set_schedstats(false);
4509 ret = 1;
4510 }
4511 out:
4512 if (!ret)
4513 pr_warn("Unable to parse schedstats=\n");
4514
4515 return ret;
4516 }
4517 __setup("schedstats=", setup_schedstats);
4518
4519 #ifdef CONFIG_PROC_SYSCTL
sysctl_schedstats(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)4520 static int sysctl_schedstats(struct ctl_table *table, int write, void *buffer,
4521 size_t *lenp, loff_t *ppos)
4522 {
4523 struct ctl_table t;
4524 int err;
4525 int state = static_branch_likely(&sched_schedstats);
4526
4527 if (write && !capable(CAP_SYS_ADMIN))
4528 return -EPERM;
4529
4530 t = *table;
4531 t.data = &state;
4532 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
4533 if (err < 0)
4534 return err;
4535 if (write)
4536 set_schedstats(state);
4537 return err;
4538 }
4539 #endif /* CONFIG_PROC_SYSCTL */
4540 #endif /* CONFIG_SCHEDSTATS */
4541
4542 #ifdef CONFIG_SYSCTL
4543 static struct ctl_table sched_core_sysctls[] = {
4544 #ifdef CONFIG_SCHEDSTATS
4545 {
4546 .procname = "sched_schedstats",
4547 .data = NULL,
4548 .maxlen = sizeof(unsigned int),
4549 .mode = 0644,
4550 .proc_handler = sysctl_schedstats,
4551 .extra1 = SYSCTL_ZERO,
4552 .extra2 = SYSCTL_ONE,
4553 },
4554 #endif /* CONFIG_SCHEDSTATS */
4555 #ifdef CONFIG_UCLAMP_TASK
4556 {
4557 .procname = "sched_util_clamp_min",
4558 .data = &sysctl_sched_uclamp_util_min,
4559 .maxlen = sizeof(unsigned int),
4560 .mode = 0644,
4561 .proc_handler = sysctl_sched_uclamp_handler,
4562 },
4563 {
4564 .procname = "sched_util_clamp_max",
4565 .data = &sysctl_sched_uclamp_util_max,
4566 .maxlen = sizeof(unsigned int),
4567 .mode = 0644,
4568 .proc_handler = sysctl_sched_uclamp_handler,
4569 },
4570 {
4571 .procname = "sched_util_clamp_min_rt_default",
4572 .data = &sysctl_sched_uclamp_util_min_rt_default,
4573 .maxlen = sizeof(unsigned int),
4574 .mode = 0644,
4575 .proc_handler = sysctl_sched_uclamp_handler,
4576 },
4577 #endif /* CONFIG_UCLAMP_TASK */
4578 {}
4579 };
sched_core_sysctl_init(void)4580 static int __init sched_core_sysctl_init(void)
4581 {
4582 register_sysctl_init("kernel", sched_core_sysctls);
4583 return 0;
4584 }
4585 late_initcall(sched_core_sysctl_init);
4586 #endif /* CONFIG_SYSCTL */
4587
4588 /*
4589 * fork()/clone()-time setup:
4590 */
sched_fork(unsigned long clone_flags,struct task_struct * p)4591 int sched_fork(unsigned long clone_flags, struct task_struct *p)
4592 {
4593 __sched_fork(clone_flags, p);
4594 /*
4595 * We mark the process as NEW here. This guarantees that
4596 * nobody will actually run it, and a signal or other external
4597 * event cannot wake it up and insert it on the runqueue either.
4598 */
4599 p->__state = TASK_NEW;
4600
4601 /*
4602 * Make sure we do not leak PI boosting priority to the child.
4603 */
4604 p->prio = current->normal_prio;
4605
4606 uclamp_fork(p);
4607
4608 /*
4609 * Revert to default priority/policy on fork if requested.
4610 */
4611 if (unlikely(p->sched_reset_on_fork)) {
4612 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
4613 p->policy = SCHED_NORMAL;
4614 p->static_prio = NICE_TO_PRIO(0);
4615 p->rt_priority = 0;
4616 } else if (PRIO_TO_NICE(p->static_prio) < 0)
4617 p->static_prio = NICE_TO_PRIO(0);
4618
4619 p->prio = p->normal_prio = p->static_prio;
4620 set_load_weight(p, false);
4621
4622 /*
4623 * We don't need the reset flag anymore after the fork. It has
4624 * fulfilled its duty:
4625 */
4626 p->sched_reset_on_fork = 0;
4627 }
4628
4629 if (dl_prio(p->prio))
4630 return -EAGAIN;
4631 else if (rt_prio(p->prio))
4632 p->sched_class = &rt_sched_class;
4633 else
4634 p->sched_class = &fair_sched_class;
4635
4636 init_entity_runnable_average(&p->se);
4637
4638
4639 #ifdef CONFIG_SCHED_INFO
4640 if (likely(sched_info_on()))
4641 memset(&p->sched_info, 0, sizeof(p->sched_info));
4642 #endif
4643 #if defined(CONFIG_SMP)
4644 p->on_cpu = 0;
4645 #endif
4646 init_task_preempt_count(p);
4647 #ifdef CONFIG_SMP
4648 plist_node_init(&p->pushable_tasks, MAX_PRIO);
4649 RB_CLEAR_NODE(&p->pushable_dl_tasks);
4650 #endif
4651 return 0;
4652 }
4653
sched_cgroup_fork(struct task_struct * p,struct kernel_clone_args * kargs)4654 void sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs)
4655 {
4656 unsigned long flags;
4657
4658 /*
4659 * Because we're not yet on the pid-hash, p->pi_lock isn't strictly
4660 * required yet, but lockdep gets upset if rules are violated.
4661 */
4662 raw_spin_lock_irqsave(&p->pi_lock, flags);
4663 #ifdef CONFIG_CGROUP_SCHED
4664 if (1) {
4665 struct task_group *tg;
4666 tg = container_of(kargs->cset->subsys[cpu_cgrp_id],
4667 struct task_group, css);
4668 tg = autogroup_task_group(p, tg);
4669 p->sched_task_group = tg;
4670 }
4671 #endif
4672 rseq_migrate(p);
4673 /*
4674 * We're setting the CPU for the first time, we don't migrate,
4675 * so use __set_task_cpu().
4676 */
4677 __set_task_cpu(p, smp_processor_id());
4678 if (p->sched_class->task_fork)
4679 p->sched_class->task_fork(p);
4680 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4681 }
4682
sched_post_fork(struct task_struct * p)4683 void sched_post_fork(struct task_struct *p)
4684 {
4685 uclamp_post_fork(p);
4686 }
4687
to_ratio(u64 period,u64 runtime)4688 unsigned long to_ratio(u64 period, u64 runtime)
4689 {
4690 if (runtime == RUNTIME_INF)
4691 return BW_UNIT;
4692
4693 /*
4694 * Doing this here saves a lot of checks in all
4695 * the calling paths, and returning zero seems
4696 * safe for them anyway.
4697 */
4698 if (period == 0)
4699 return 0;
4700
4701 return div64_u64(runtime << BW_SHIFT, period);
4702 }
4703
4704 /*
4705 * wake_up_new_task - wake up a newly created task for the first time.
4706 *
4707 * This function will do some initial scheduler statistics housekeeping
4708 * that must be done for every newly created context, then puts the task
4709 * on the runqueue and wakes it.
4710 */
wake_up_new_task(struct task_struct * p)4711 void wake_up_new_task(struct task_struct *p)
4712 {
4713 struct rq_flags rf;
4714 struct rq *rq;
4715
4716 raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
4717 WRITE_ONCE(p->__state, TASK_RUNNING);
4718 #ifdef CONFIG_SMP
4719 /*
4720 * Fork balancing, do it here and not earlier because:
4721 * - cpus_ptr can change in the fork path
4722 * - any previously selected CPU might disappear through hotplug
4723 *
4724 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
4725 * as we're not fully set-up yet.
4726 */
4727 p->recent_used_cpu = task_cpu(p);
4728 rseq_migrate(p);
4729 __set_task_cpu(p, select_task_rq(p, task_cpu(p), WF_FORK));
4730 #endif
4731 rq = __task_rq_lock(p, &rf);
4732 update_rq_clock(rq);
4733 post_init_entity_util_avg(p);
4734
4735 activate_task(rq, p, ENQUEUE_NOCLOCK);
4736 trace_sched_wakeup_new(p);
4737 check_preempt_curr(rq, p, WF_FORK);
4738 #ifdef CONFIG_SMP
4739 if (p->sched_class->task_woken) {
4740 /*
4741 * Nothing relies on rq->lock after this, so it's fine to
4742 * drop it.
4743 */
4744 rq_unpin_lock(rq, &rf);
4745 p->sched_class->task_woken(rq, p);
4746 rq_repin_lock(rq, &rf);
4747 }
4748 #endif
4749 task_rq_unlock(rq, p, &rf);
4750 }
4751
4752 #ifdef CONFIG_PREEMPT_NOTIFIERS
4753
4754 static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key);
4755
preempt_notifier_inc(void)4756 void preempt_notifier_inc(void)
4757 {
4758 static_branch_inc(&preempt_notifier_key);
4759 }
4760 EXPORT_SYMBOL_GPL(preempt_notifier_inc);
4761
preempt_notifier_dec(void)4762 void preempt_notifier_dec(void)
4763 {
4764 static_branch_dec(&preempt_notifier_key);
4765 }
4766 EXPORT_SYMBOL_GPL(preempt_notifier_dec);
4767
4768 /**
4769 * preempt_notifier_register - tell me when current is being preempted & rescheduled
4770 * @notifier: notifier struct to register
4771 */
preempt_notifier_register(struct preempt_notifier * notifier)4772 void preempt_notifier_register(struct preempt_notifier *notifier)
4773 {
4774 if (!static_branch_unlikely(&preempt_notifier_key))
4775 WARN(1, "registering preempt_notifier while notifiers disabled\n");
4776
4777 hlist_add_head(¬ifier->link, ¤t->preempt_notifiers);
4778 }
4779 EXPORT_SYMBOL_GPL(preempt_notifier_register);
4780
4781 /**
4782 * preempt_notifier_unregister - no longer interested in preemption notifications
4783 * @notifier: notifier struct to unregister
4784 *
4785 * This is *not* safe to call from within a preemption notifier.
4786 */
preempt_notifier_unregister(struct preempt_notifier * notifier)4787 void preempt_notifier_unregister(struct preempt_notifier *notifier)
4788 {
4789 hlist_del(¬ifier->link);
4790 }
4791 EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
4792
__fire_sched_in_preempt_notifiers(struct task_struct * curr)4793 static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
4794 {
4795 struct preempt_notifier *notifier;
4796
4797 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
4798 notifier->ops->sched_in(notifier, raw_smp_processor_id());
4799 }
4800
fire_sched_in_preempt_notifiers(struct task_struct * curr)4801 static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
4802 {
4803 if (static_branch_unlikely(&preempt_notifier_key))
4804 __fire_sched_in_preempt_notifiers(curr);
4805 }
4806
4807 static void
__fire_sched_out_preempt_notifiers(struct task_struct * curr,struct task_struct * next)4808 __fire_sched_out_preempt_notifiers(struct task_struct *curr,
4809 struct task_struct *next)
4810 {
4811 struct preempt_notifier *notifier;
4812
4813 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
4814 notifier->ops->sched_out(notifier, next);
4815 }
4816
4817 static __always_inline void
fire_sched_out_preempt_notifiers(struct task_struct * curr,struct task_struct * next)4818 fire_sched_out_preempt_notifiers(struct task_struct *curr,
4819 struct task_struct *next)
4820 {
4821 if (static_branch_unlikely(&preempt_notifier_key))
4822 __fire_sched_out_preempt_notifiers(curr, next);
4823 }
4824
4825 #else /* !CONFIG_PREEMPT_NOTIFIERS */
4826
fire_sched_in_preempt_notifiers(struct task_struct * curr)4827 static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
4828 {
4829 }
4830
4831 static inline void
fire_sched_out_preempt_notifiers(struct task_struct * curr,struct task_struct * next)4832 fire_sched_out_preempt_notifiers(struct task_struct *curr,
4833 struct task_struct *next)
4834 {
4835 }
4836
4837 #endif /* CONFIG_PREEMPT_NOTIFIERS */
4838
prepare_task(struct task_struct * next)4839 static inline void prepare_task(struct task_struct *next)
4840 {
4841 #ifdef CONFIG_SMP
4842 /*
4843 * Claim the task as running, we do this before switching to it
4844 * such that any running task will have this set.
4845 *
4846 * See the smp_load_acquire(&p->on_cpu) case in ttwu() and
4847 * its ordering comment.
4848 */
4849 WRITE_ONCE(next->on_cpu, 1);
4850 #endif
4851 }
4852
finish_task(struct task_struct * prev)4853 static inline void finish_task(struct task_struct *prev)
4854 {
4855 #ifdef CONFIG_SMP
4856 /*
4857 * This must be the very last reference to @prev from this CPU. After
4858 * p->on_cpu is cleared, the task can be moved to a different CPU. We
4859 * must ensure this doesn't happen until the switch is completely
4860 * finished.
4861 *
4862 * In particular, the load of prev->state in finish_task_switch() must
4863 * happen before this.
4864 *
4865 * Pairs with the smp_cond_load_acquire() in try_to_wake_up().
4866 */
4867 smp_store_release(&prev->on_cpu, 0);
4868 #endif
4869 }
4870
4871 #ifdef CONFIG_SMP
4872
do_balance_callbacks(struct rq * rq,struct balance_callback * head)4873 static void do_balance_callbacks(struct rq *rq, struct balance_callback *head)
4874 {
4875 void (*func)(struct rq *rq);
4876 struct balance_callback *next;
4877
4878 lockdep_assert_rq_held(rq);
4879
4880 while (head) {
4881 func = (void (*)(struct rq *))head->func;
4882 next = head->next;
4883 head->next = NULL;
4884 head = next;
4885
4886 func(rq);
4887 }
4888 }
4889
4890 static void balance_push(struct rq *rq);
4891
4892 /*
4893 * balance_push_callback is a right abuse of the callback interface and plays
4894 * by significantly different rules.
4895 *
4896 * Where the normal balance_callback's purpose is to be ran in the same context
4897 * that queued it (only later, when it's safe to drop rq->lock again),
4898 * balance_push_callback is specifically targeted at __schedule().
4899 *
4900 * This abuse is tolerated because it places all the unlikely/odd cases behind
4901 * a single test, namely: rq->balance_callback == NULL.
4902 */
4903 struct balance_callback balance_push_callback = {
4904 .next = NULL,
4905 .func = balance_push,
4906 };
4907
4908 static inline struct balance_callback *
__splice_balance_callbacks(struct rq * rq,bool split)4909 __splice_balance_callbacks(struct rq *rq, bool split)
4910 {
4911 struct balance_callback *head = rq->balance_callback;
4912
4913 if (likely(!head))
4914 return NULL;
4915
4916 lockdep_assert_rq_held(rq);
4917 /*
4918 * Must not take balance_push_callback off the list when
4919 * splice_balance_callbacks() and balance_callbacks() are not
4920 * in the same rq->lock section.
4921 *
4922 * In that case it would be possible for __schedule() to interleave
4923 * and observe the list empty.
4924 */
4925 if (split && head == &balance_push_callback)
4926 head = NULL;
4927 else
4928 rq->balance_callback = NULL;
4929
4930 return head;
4931 }
4932
splice_balance_callbacks(struct rq * rq)4933 static inline struct balance_callback *splice_balance_callbacks(struct rq *rq)
4934 {
4935 return __splice_balance_callbacks(rq, true);
4936 }
4937
__balance_callbacks(struct rq * rq)4938 static void __balance_callbacks(struct rq *rq)
4939 {
4940 do_balance_callbacks(rq, __splice_balance_callbacks(rq, false));
4941 }
4942
balance_callbacks(struct rq * rq,struct balance_callback * head)4943 static inline void balance_callbacks(struct rq *rq, struct balance_callback *head)
4944 {
4945 unsigned long flags;
4946
4947 if (unlikely(head)) {
4948 raw_spin_rq_lock_irqsave(rq, flags);
4949 do_balance_callbacks(rq, head);
4950 raw_spin_rq_unlock_irqrestore(rq, flags);
4951 }
4952 }
4953
4954 #else
4955
__balance_callbacks(struct rq * rq)4956 static inline void __balance_callbacks(struct rq *rq)
4957 {
4958 }
4959
splice_balance_callbacks(struct rq * rq)4960 static inline struct balance_callback *splice_balance_callbacks(struct rq *rq)
4961 {
4962 return NULL;
4963 }
4964
balance_callbacks(struct rq * rq,struct balance_callback * head)4965 static inline void balance_callbacks(struct rq *rq, struct balance_callback *head)
4966 {
4967 }
4968
4969 #endif
4970
4971 static inline void
prepare_lock_switch(struct rq * rq,struct task_struct * next,struct rq_flags * rf)4972 prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf)
4973 {
4974 /*
4975 * Since the runqueue lock will be released by the next
4976 * task (which is an invalid locking op but in the case
4977 * of the scheduler it's an obvious special-case), so we
4978 * do an early lockdep release here:
4979 */
4980 rq_unpin_lock(rq, rf);
4981 spin_release(&__rq_lockp(rq)->dep_map, _THIS_IP_);
4982 #ifdef CONFIG_DEBUG_SPINLOCK
4983 /* this is a valid case when another task releases the spinlock */
4984 rq_lockp(rq)->owner = next;
4985 #endif
4986 }
4987
finish_lock_switch(struct rq * rq)4988 static inline void finish_lock_switch(struct rq *rq)
4989 {
4990 /*
4991 * If we are tracking spinlock dependencies then we have to
4992 * fix up the runqueue lock - which gets 'carried over' from
4993 * prev into current:
4994 */
4995 spin_acquire(&__rq_lockp(rq)->dep_map, 0, 0, _THIS_IP_);
4996 __balance_callbacks(rq);
4997 raw_spin_rq_unlock_irq(rq);
4998 }
4999
5000 /*
5001 * NOP if the arch has not defined these:
5002 */
5003
5004 #ifndef prepare_arch_switch
5005 # define prepare_arch_switch(next) do { } while (0)
5006 #endif
5007
5008 #ifndef finish_arch_post_lock_switch
5009 # define finish_arch_post_lock_switch() do { } while (0)
5010 #endif
5011
kmap_local_sched_out(void)5012 static inline void kmap_local_sched_out(void)
5013 {
5014 #ifdef CONFIG_KMAP_LOCAL
5015 if (unlikely(current->kmap_ctrl.idx))
5016 __kmap_local_sched_out();
5017 #endif
5018 }
5019
kmap_local_sched_in(void)5020 static inline void kmap_local_sched_in(void)
5021 {
5022 #ifdef CONFIG_KMAP_LOCAL
5023 if (unlikely(current->kmap_ctrl.idx))
5024 __kmap_local_sched_in();
5025 #endif
5026 }
5027
5028 /**
5029 * prepare_task_switch - prepare to switch tasks
5030 * @rq: the runqueue preparing to switch
5031 * @prev: the current task that is being switched out
5032 * @next: the task we are going to switch to.
5033 *
5034 * This is called with the rq lock held and interrupts off. It must
5035 * be paired with a subsequent finish_task_switch after the context
5036 * switch.
5037 *
5038 * prepare_task_switch sets up locking and calls architecture specific
5039 * hooks.
5040 */
5041 static inline void
prepare_task_switch(struct rq * rq,struct task_struct * prev,struct task_struct * next)5042 prepare_task_switch(struct rq *rq, struct task_struct *prev,
5043 struct task_struct *next)
5044 {
5045 kcov_prepare_switch(prev);
5046 sched_info_switch(rq, prev, next);
5047 perf_event_task_sched_out(prev, next);
5048 rseq_preempt(prev);
5049 fire_sched_out_preempt_notifiers(prev, next);
5050 kmap_local_sched_out();
5051 prepare_task(next);
5052 prepare_arch_switch(next);
5053 }
5054
5055 /**
5056 * finish_task_switch - clean up after a task-switch
5057 * @prev: the thread we just switched away from.
5058 *
5059 * finish_task_switch must be called after the context switch, paired
5060 * with a prepare_task_switch call before the context switch.
5061 * finish_task_switch will reconcile locking set up by prepare_task_switch,
5062 * and do any other architecture-specific cleanup actions.
5063 *
5064 * Note that we may have delayed dropping an mm in context_switch(). If
5065 * so, we finish that here outside of the runqueue lock. (Doing it
5066 * with the lock held can cause deadlocks; see schedule() for
5067 * details.)
5068 *
5069 * The context switch have flipped the stack from under us and restored the
5070 * local variables which were saved when this task called schedule() in the
5071 * past. prev == current is still correct but we need to recalculate this_rq
5072 * because prev may have moved to another CPU.
5073 */
finish_task_switch(struct task_struct * prev)5074 static struct rq *finish_task_switch(struct task_struct *prev)
5075 __releases(rq->lock)
5076 {
5077 struct rq *rq = this_rq();
5078 struct mm_struct *mm = rq->prev_mm;
5079 unsigned int prev_state;
5080
5081 /*
5082 * The previous task will have left us with a preempt_count of 2
5083 * because it left us after:
5084 *
5085 * schedule()
5086 * preempt_disable(); // 1
5087 * __schedule()
5088 * raw_spin_lock_irq(&rq->lock) // 2
5089 *
5090 * Also, see FORK_PREEMPT_COUNT.
5091 */
5092 if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
5093 "corrupted preempt_count: %s/%d/0x%x\n",
5094 current->comm, current->pid, preempt_count()))
5095 preempt_count_set(FORK_PREEMPT_COUNT);
5096
5097 rq->prev_mm = NULL;
5098
5099 /*
5100 * A task struct has one reference for the use as "current".
5101 * If a task dies, then it sets TASK_DEAD in tsk->state and calls
5102 * schedule one last time. The schedule call will never return, and
5103 * the scheduled task must drop that reference.
5104 *
5105 * We must observe prev->state before clearing prev->on_cpu (in
5106 * finish_task), otherwise a concurrent wakeup can get prev
5107 * running on another CPU and we could rave with its RUNNING -> DEAD
5108 * transition, resulting in a double drop.
5109 */
5110 prev_state = READ_ONCE(prev->__state);
5111 vtime_task_switch(prev);
5112 perf_event_task_sched_in(prev, current);
5113 finish_task(prev);
5114 tick_nohz_task_switch();
5115 finish_lock_switch(rq);
5116 finish_arch_post_lock_switch();
5117 kcov_finish_switch(current);
5118 /*
5119 * kmap_local_sched_out() is invoked with rq::lock held and
5120 * interrupts disabled. There is no requirement for that, but the
5121 * sched out code does not have an interrupt enabled section.
5122 * Restoring the maps on sched in does not require interrupts being
5123 * disabled either.
5124 */
5125 kmap_local_sched_in();
5126
5127 fire_sched_in_preempt_notifiers(current);
5128 /*
5129 * When switching through a kernel thread, the loop in
5130 * membarrier_{private,global}_expedited() may have observed that
5131 * kernel thread and not issued an IPI. It is therefore possible to
5132 * schedule between user->kernel->user threads without passing though
5133 * switch_mm(). Membarrier requires a barrier after storing to
5134 * rq->curr, before returning to userspace, so provide them here:
5135 *
5136 * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
5137 * provided by mmdrop(),
5138 * - a sync_core for SYNC_CORE.
5139 */
5140 if (mm) {
5141 membarrier_mm_sync_core_before_usermode(mm);
5142 mmdrop_sched(mm);
5143 }
5144 if (unlikely(prev_state == TASK_DEAD)) {
5145 if (prev->sched_class->task_dead)
5146 prev->sched_class->task_dead(prev);
5147
5148 /* Task is done with its stack. */
5149 put_task_stack(prev);
5150
5151 put_task_struct_rcu_user(prev);
5152 }
5153
5154 return rq;
5155 }
5156
5157 /**
5158 * schedule_tail - first thing a freshly forked thread must call.
5159 * @prev: the thread we just switched away from.
5160 */
schedule_tail(struct task_struct * prev)5161 asmlinkage __visible void schedule_tail(struct task_struct *prev)
5162 __releases(rq->lock)
5163 {
5164 /*
5165 * New tasks start with FORK_PREEMPT_COUNT, see there and
5166 * finish_task_switch() for details.
5167 *
5168 * finish_task_switch() will drop rq->lock() and lower preempt_count
5169 * and the preempt_enable() will end up enabling preemption (on
5170 * PREEMPT_COUNT kernels).
5171 */
5172
5173 finish_task_switch(prev);
5174 preempt_enable();
5175
5176 if (current->set_child_tid)
5177 put_user(task_pid_vnr(current), current->set_child_tid);
5178
5179 calculate_sigpending();
5180 }
5181
5182 /*
5183 * context_switch - switch to the new MM and the new thread's register state.
5184 */
5185 static __always_inline struct rq *
context_switch(struct rq * rq,struct task_struct * prev,struct task_struct * next,struct rq_flags * rf)5186 context_switch(struct rq *rq, struct task_struct *prev,
5187 struct task_struct *next, struct rq_flags *rf)
5188 {
5189 prepare_task_switch(rq, prev, next);
5190
5191 /*
5192 * For paravirt, this is coupled with an exit in switch_to to
5193 * combine the page table reload and the switch backend into
5194 * one hypercall.
5195 */
5196 arch_start_context_switch(prev);
5197
5198 /*
5199 * kernel -> kernel lazy + transfer active
5200 * user -> kernel lazy + mmgrab() active
5201 *
5202 * kernel -> user switch + mmdrop() active
5203 * user -> user switch
5204 */
5205 if (!next->mm) { // to kernel
5206 enter_lazy_tlb(prev->active_mm, next);
5207
5208 next->active_mm = prev->active_mm;
5209 if (prev->mm) // from user
5210 mmgrab(prev->active_mm);
5211 else
5212 prev->active_mm = NULL;
5213 } else { // to user
5214 membarrier_switch_mm(rq, prev->active_mm, next->mm);
5215 /*
5216 * sys_membarrier() requires an smp_mb() between setting
5217 * rq->curr / membarrier_switch_mm() and returning to userspace.
5218 *
5219 * The below provides this either through switch_mm(), or in
5220 * case 'prev->active_mm == next->mm' through
5221 * finish_task_switch()'s mmdrop().
5222 */
5223 switch_mm_irqs_off(prev->active_mm, next->mm, next);
5224 lru_gen_use_mm(next->mm);
5225
5226 if (!prev->mm) { // from kernel
5227 /* will mmdrop() in finish_task_switch(). */
5228 rq->prev_mm = prev->active_mm;
5229 prev->active_mm = NULL;
5230 }
5231 }
5232
5233 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
5234
5235 prepare_lock_switch(rq, next, rf);
5236
5237 /* Here we just switch the register state and the stack. */
5238 switch_to(prev, next, prev);
5239 barrier();
5240
5241 return finish_task_switch(prev);
5242 }
5243
5244 /*
5245 * nr_running and nr_context_switches:
5246 *
5247 * externally visible scheduler statistics: current number of runnable
5248 * threads, total number of context switches performed since bootup.
5249 */
nr_running(void)5250 unsigned int nr_running(void)
5251 {
5252 unsigned int i, sum = 0;
5253
5254 for_each_online_cpu(i)
5255 sum += cpu_rq(i)->nr_running;
5256
5257 return sum;
5258 }
5259
5260 /*
5261 * Check if only the current task is running on the CPU.
5262 *
5263 * Caution: this function does not check that the caller has disabled
5264 * preemption, thus the result might have a time-of-check-to-time-of-use
5265 * race. The caller is responsible to use it correctly, for example:
5266 *
5267 * - from a non-preemptible section (of course)
5268 *
5269 * - from a thread that is bound to a single CPU
5270 *
5271 * - in a loop with very short iterations (e.g. a polling loop)
5272 */
single_task_running(void)5273 bool single_task_running(void)
5274 {
5275 return raw_rq()->nr_running == 1;
5276 }
5277 EXPORT_SYMBOL(single_task_running);
5278
nr_context_switches(void)5279 unsigned long long nr_context_switches(void)
5280 {
5281 int i;
5282 unsigned long long sum = 0;
5283
5284 for_each_possible_cpu(i)
5285 sum += cpu_rq(i)->nr_switches;
5286
5287 return sum;
5288 }
5289
5290 /*
5291 * Consumers of these two interfaces, like for example the cpuidle menu
5292 * governor, are using nonsensical data. Preferring shallow idle state selection
5293 * for a CPU that has IO-wait which might not even end up running the task when
5294 * it does become runnable.
5295 */
5296
nr_iowait_cpu(int cpu)5297 unsigned int nr_iowait_cpu(int cpu)
5298 {
5299 return atomic_read(&cpu_rq(cpu)->nr_iowait);
5300 }
5301
5302 /*
5303 * IO-wait accounting, and how it's mostly bollocks (on SMP).
5304 *
5305 * The idea behind IO-wait account is to account the idle time that we could
5306 * have spend running if it were not for IO. That is, if we were to improve the
5307 * storage performance, we'd have a proportional reduction in IO-wait time.
5308 *
5309 * This all works nicely on UP, where, when a task blocks on IO, we account
5310 * idle time as IO-wait, because if the storage were faster, it could've been
5311 * running and we'd not be idle.
5312 *
5313 * This has been extended to SMP, by doing the same for each CPU. This however
5314 * is broken.
5315 *
5316 * Imagine for instance the case where two tasks block on one CPU, only the one
5317 * CPU will have IO-wait accounted, while the other has regular idle. Even
5318 * though, if the storage were faster, both could've ran at the same time,
5319 * utilising both CPUs.
5320 *
5321 * This means, that when looking globally, the current IO-wait accounting on
5322 * SMP is a lower bound, by reason of under accounting.
5323 *
5324 * Worse, since the numbers are provided per CPU, they are sometimes
5325 * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
5326 * associated with any one particular CPU, it can wake to another CPU than it
5327 * blocked on. This means the per CPU IO-wait number is meaningless.
5328 *
5329 * Task CPU affinities can make all that even more 'interesting'.
5330 */
5331
nr_iowait(void)5332 unsigned int nr_iowait(void)
5333 {
5334 unsigned int i, sum = 0;
5335
5336 for_each_possible_cpu(i)
5337 sum += nr_iowait_cpu(i);
5338
5339 return sum;
5340 }
5341
5342 #ifdef CONFIG_SMP
5343
5344 /*
5345 * sched_exec - execve() is a valuable balancing opportunity, because at
5346 * this point the task has the smallest effective memory and cache footprint.
5347 */
sched_exec(void)5348 void sched_exec(void)
5349 {
5350 struct task_struct *p = current;
5351 unsigned long flags;
5352 int dest_cpu;
5353
5354 raw_spin_lock_irqsave(&p->pi_lock, flags);
5355 dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), WF_EXEC);
5356 if (dest_cpu == smp_processor_id())
5357 goto unlock;
5358
5359 if (likely(cpu_active(dest_cpu))) {
5360 struct migration_arg arg = { p, dest_cpu };
5361
5362 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
5363 stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
5364 return;
5365 }
5366 unlock:
5367 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
5368 }
5369
5370 #endif
5371
5372 DEFINE_PER_CPU(struct kernel_stat, kstat);
5373 DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
5374
5375 EXPORT_PER_CPU_SYMBOL(kstat);
5376 EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
5377
5378 /*
5379 * The function fair_sched_class.update_curr accesses the struct curr
5380 * and its field curr->exec_start; when called from task_sched_runtime(),
5381 * we observe a high rate of cache misses in practice.
5382 * Prefetching this data results in improved performance.
5383 */
prefetch_curr_exec_start(struct task_struct * p)5384 static inline void prefetch_curr_exec_start(struct task_struct *p)
5385 {
5386 #ifdef CONFIG_FAIR_GROUP_SCHED
5387 struct sched_entity *curr = (&p->se)->cfs_rq->curr;
5388 #else
5389 struct sched_entity *curr = (&task_rq(p)->cfs)->curr;
5390 #endif
5391 prefetch(curr);
5392 prefetch(&curr->exec_start);
5393 }
5394
5395 /*
5396 * Return accounted runtime for the task.
5397 * In case the task is currently running, return the runtime plus current's
5398 * pending runtime that have not been accounted yet.
5399 */
task_sched_runtime(struct task_struct * p)5400 unsigned long long task_sched_runtime(struct task_struct *p)
5401 {
5402 struct rq_flags rf;
5403 struct rq *rq;
5404 u64 ns;
5405
5406 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
5407 /*
5408 * 64-bit doesn't need locks to atomically read a 64-bit value.
5409 * So we have a optimization chance when the task's delta_exec is 0.
5410 * Reading ->on_cpu is racy, but this is ok.
5411 *
5412 * If we race with it leaving CPU, we'll take a lock. So we're correct.
5413 * If we race with it entering CPU, unaccounted time is 0. This is
5414 * indistinguishable from the read occurring a few cycles earlier.
5415 * If we see ->on_cpu without ->on_rq, the task is leaving, and has
5416 * been accounted, so we're correct here as well.
5417 */
5418 if (!p->on_cpu || !task_on_rq_queued(p))
5419 return p->se.sum_exec_runtime;
5420 #endif
5421
5422 rq = task_rq_lock(p, &rf);
5423 /*
5424 * Must be ->curr _and_ ->on_rq. If dequeued, we would
5425 * project cycles that may never be accounted to this
5426 * thread, breaking clock_gettime().
5427 */
5428 if (task_current(rq, p) && task_on_rq_queued(p)) {
5429 prefetch_curr_exec_start(p);
5430 update_rq_clock(rq);
5431 p->sched_class->update_curr(rq);
5432 }
5433 ns = p->se.sum_exec_runtime;
5434 task_rq_unlock(rq, p, &rf);
5435
5436 return ns;
5437 }
5438
5439 #ifdef CONFIG_SCHED_DEBUG
cpu_resched_latency(struct rq * rq)5440 static u64 cpu_resched_latency(struct rq *rq)
5441 {
5442 int latency_warn_ms = READ_ONCE(sysctl_resched_latency_warn_ms);
5443 u64 resched_latency, now = rq_clock(rq);
5444 static bool warned_once;
5445
5446 if (sysctl_resched_latency_warn_once && warned_once)
5447 return 0;
5448
5449 if (!need_resched() || !latency_warn_ms)
5450 return 0;
5451
5452 if (system_state == SYSTEM_BOOTING)
5453 return 0;
5454
5455 if (!rq->last_seen_need_resched_ns) {
5456 rq->last_seen_need_resched_ns = now;
5457 rq->ticks_without_resched = 0;
5458 return 0;
5459 }
5460
5461 rq->ticks_without_resched++;
5462 resched_latency = now - rq->last_seen_need_resched_ns;
5463 if (resched_latency <= latency_warn_ms * NSEC_PER_MSEC)
5464 return 0;
5465
5466 warned_once = true;
5467
5468 return resched_latency;
5469 }
5470
setup_resched_latency_warn_ms(char * str)5471 static int __init setup_resched_latency_warn_ms(char *str)
5472 {
5473 long val;
5474
5475 if ((kstrtol(str, 0, &val))) {
5476 pr_warn("Unable to set resched_latency_warn_ms\n");
5477 return 1;
5478 }
5479
5480 sysctl_resched_latency_warn_ms = val;
5481 return 1;
5482 }
5483 __setup("resched_latency_warn_ms=", setup_resched_latency_warn_ms);
5484 #else
cpu_resched_latency(struct rq * rq)5485 static inline u64 cpu_resched_latency(struct rq *rq) { return 0; }
5486 #endif /* CONFIG_SCHED_DEBUG */
5487
5488 /*
5489 * This function gets called by the timer code, with HZ frequency.
5490 * We call it with interrupts disabled.
5491 */
scheduler_tick(void)5492 void scheduler_tick(void)
5493 {
5494 int cpu = smp_processor_id();
5495 struct rq *rq = cpu_rq(cpu);
5496 struct task_struct *curr = rq->curr;
5497 struct rq_flags rf;
5498 unsigned long thermal_pressure;
5499 u64 resched_latency;
5500
5501 if (housekeeping_cpu(cpu, HK_TYPE_TICK))
5502 arch_scale_freq_tick();
5503
5504 sched_clock_tick();
5505
5506 rq_lock(rq, &rf);
5507
5508 update_rq_clock(rq);
5509 thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
5510 update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure);
5511 curr->sched_class->task_tick(rq, curr, 0);
5512 if (sched_feat(LATENCY_WARN))
5513 resched_latency = cpu_resched_latency(rq);
5514 calc_global_load_tick(rq);
5515 sched_core_tick(rq);
5516
5517 rq_unlock(rq, &rf);
5518
5519 if (sched_feat(LATENCY_WARN) && resched_latency)
5520 resched_latency_warn(cpu, resched_latency);
5521
5522 perf_event_task_tick();
5523
5524 #ifdef CONFIG_SMP
5525 rq->idle_balance = idle_cpu(cpu);
5526 trigger_load_balance(rq);
5527 #endif
5528 }
5529
5530 #ifdef CONFIG_NO_HZ_FULL
5531
5532 struct tick_work {
5533 int cpu;
5534 atomic_t state;
5535 struct delayed_work work;
5536 };
5537 /* Values for ->state, see diagram below. */
5538 #define TICK_SCHED_REMOTE_OFFLINE 0
5539 #define TICK_SCHED_REMOTE_OFFLINING 1
5540 #define TICK_SCHED_REMOTE_RUNNING 2
5541
5542 /*
5543 * State diagram for ->state:
5544 *
5545 *
5546 * TICK_SCHED_REMOTE_OFFLINE
5547 * | ^
5548 * | |
5549 * | | sched_tick_remote()
5550 * | |
5551 * | |
5552 * +--TICK_SCHED_REMOTE_OFFLINING
5553 * | ^
5554 * | |
5555 * sched_tick_start() | | sched_tick_stop()
5556 * | |
5557 * V |
5558 * TICK_SCHED_REMOTE_RUNNING
5559 *
5560 *
5561 * Other transitions get WARN_ON_ONCE(), except that sched_tick_remote()
5562 * and sched_tick_start() are happy to leave the state in RUNNING.
5563 */
5564
5565 static struct tick_work __percpu *tick_work_cpu;
5566
sched_tick_remote(struct work_struct * work)5567 static void sched_tick_remote(struct work_struct *work)
5568 {
5569 struct delayed_work *dwork = to_delayed_work(work);
5570 struct tick_work *twork = container_of(dwork, struct tick_work, work);
5571 int cpu = twork->cpu;
5572 struct rq *rq = cpu_rq(cpu);
5573 struct task_struct *curr;
5574 struct rq_flags rf;
5575 u64 delta;
5576 int os;
5577
5578 /*
5579 * Handle the tick only if it appears the remote CPU is running in full
5580 * dynticks mode. The check is racy by nature, but missing a tick or
5581 * having one too much is no big deal because the scheduler tick updates
5582 * statistics and checks timeslices in a time-independent way, regardless
5583 * of when exactly it is running.
5584 */
5585 if (!tick_nohz_tick_stopped_cpu(cpu))
5586 goto out_requeue;
5587
5588 rq_lock_irq(rq, &rf);
5589 curr = rq->curr;
5590 if (cpu_is_offline(cpu))
5591 goto out_unlock;
5592
5593 update_rq_clock(rq);
5594
5595 if (!is_idle_task(curr)) {
5596 /*
5597 * Make sure the next tick runs within a reasonable
5598 * amount of time.
5599 */
5600 delta = rq_clock_task(rq) - curr->se.exec_start;
5601 WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
5602 }
5603 curr->sched_class->task_tick(rq, curr, 0);
5604
5605 calc_load_nohz_remote(rq);
5606 out_unlock:
5607 rq_unlock_irq(rq, &rf);
5608 out_requeue:
5609
5610 /*
5611 * Run the remote tick once per second (1Hz). This arbitrary
5612 * frequency is large enough to avoid overload but short enough
5613 * to keep scheduler internal stats reasonably up to date. But
5614 * first update state to reflect hotplug activity if required.
5615 */
5616 os = atomic_fetch_add_unless(&twork->state, -1, TICK_SCHED_REMOTE_RUNNING);
5617 WARN_ON_ONCE(os == TICK_SCHED_REMOTE_OFFLINE);
5618 if (os == TICK_SCHED_REMOTE_RUNNING)
5619 queue_delayed_work(system_unbound_wq, dwork, HZ);
5620 }
5621
sched_tick_start(int cpu)5622 static void sched_tick_start(int cpu)
5623 {
5624 int os;
5625 struct tick_work *twork;
5626
5627 if (housekeeping_cpu(cpu, HK_TYPE_TICK))
5628 return;
5629
5630 WARN_ON_ONCE(!tick_work_cpu);
5631
5632 twork = per_cpu_ptr(tick_work_cpu, cpu);
5633 os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_RUNNING);
5634 WARN_ON_ONCE(os == TICK_SCHED_REMOTE_RUNNING);
5635 if (os == TICK_SCHED_REMOTE_OFFLINE) {
5636 twork->cpu = cpu;
5637 INIT_DELAYED_WORK(&twork->work, sched_tick_remote);
5638 queue_delayed_work(system_unbound_wq, &twork->work, HZ);
5639 }
5640 }
5641
5642 #ifdef CONFIG_HOTPLUG_CPU
sched_tick_stop(int cpu)5643 static void sched_tick_stop(int cpu)
5644 {
5645 struct tick_work *twork;
5646 int os;
5647
5648 if (housekeeping_cpu(cpu, HK_TYPE_TICK))
5649 return;
5650
5651 WARN_ON_ONCE(!tick_work_cpu);
5652
5653 twork = per_cpu_ptr(tick_work_cpu, cpu);
5654 /* There cannot be competing actions, but don't rely on stop-machine. */
5655 os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_OFFLINING);
5656 WARN_ON_ONCE(os != TICK_SCHED_REMOTE_RUNNING);
5657 /* Don't cancel, as this would mess up the state machine. */
5658 }
5659 #endif /* CONFIG_HOTPLUG_CPU */
5660
sched_tick_offload_init(void)5661 int __init sched_tick_offload_init(void)
5662 {
5663 tick_work_cpu = alloc_percpu(struct tick_work);
5664 BUG_ON(!tick_work_cpu);
5665 return 0;
5666 }
5667
5668 #else /* !CONFIG_NO_HZ_FULL */
sched_tick_start(int cpu)5669 static inline void sched_tick_start(int cpu) { }
sched_tick_stop(int cpu)5670 static inline void sched_tick_stop(int cpu) { }
5671 #endif
5672
5673 #if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \
5674 defined(CONFIG_TRACE_PREEMPT_TOGGLE))
5675 /*
5676 * If the value passed in is equal to the current preempt count
5677 * then we just disabled preemption. Start timing the latency.
5678 */
preempt_latency_start(int val)5679 static inline void preempt_latency_start(int val)
5680 {
5681 if (preempt_count() == val) {
5682 unsigned long ip = get_lock_parent_ip();
5683 #ifdef CONFIG_DEBUG_PREEMPT
5684 current->preempt_disable_ip = ip;
5685 #endif
5686 trace_preempt_off(CALLER_ADDR0, ip);
5687 }
5688 }
5689
preempt_count_add(int val)5690 void preempt_count_add(int val)
5691 {
5692 #ifdef CONFIG_DEBUG_PREEMPT
5693 /*
5694 * Underflow?
5695 */
5696 if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
5697 return;
5698 #endif
5699 __preempt_count_add(val);
5700 #ifdef CONFIG_DEBUG_PREEMPT
5701 /*
5702 * Spinlock count overflowing soon?
5703 */
5704 DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
5705 PREEMPT_MASK - 10);
5706 #endif
5707 preempt_latency_start(val);
5708 }
5709 EXPORT_SYMBOL(preempt_count_add);
5710 NOKPROBE_SYMBOL(preempt_count_add);
5711
5712 /*
5713 * If the value passed in equals to the current preempt count
5714 * then we just enabled preemption. Stop timing the latency.
5715 */
preempt_latency_stop(int val)5716 static inline void preempt_latency_stop(int val)
5717 {
5718 if (preempt_count() == val)
5719 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
5720 }
5721
preempt_count_sub(int val)5722 void preempt_count_sub(int val)
5723 {
5724 #ifdef CONFIG_DEBUG_PREEMPT
5725 /*
5726 * Underflow?
5727 */
5728 if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
5729 return;
5730 /*
5731 * Is the spinlock portion underflowing?
5732 */
5733 if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
5734 !(preempt_count() & PREEMPT_MASK)))
5735 return;
5736 #endif
5737
5738 preempt_latency_stop(val);
5739 __preempt_count_sub(val);
5740 }
5741 EXPORT_SYMBOL(preempt_count_sub);
5742 NOKPROBE_SYMBOL(preempt_count_sub);
5743
5744 #else
preempt_latency_start(int val)5745 static inline void preempt_latency_start(int val) { }
preempt_latency_stop(int val)5746 static inline void preempt_latency_stop(int val) { }
5747 #endif
5748
get_preempt_disable_ip(struct task_struct * p)5749 static inline unsigned long get_preempt_disable_ip(struct task_struct *p)
5750 {
5751 #ifdef CONFIG_DEBUG_PREEMPT
5752 return p->preempt_disable_ip;
5753 #else
5754 return 0;
5755 #endif
5756 }
5757
5758 /*
5759 * Print scheduling while atomic bug:
5760 */
__schedule_bug(struct task_struct * prev)5761 static noinline void __schedule_bug(struct task_struct *prev)
5762 {
5763 /* Save this before calling printk(), since that will clobber it */
5764 unsigned long preempt_disable_ip = get_preempt_disable_ip(current);
5765
5766 if (oops_in_progress)
5767 return;
5768
5769 printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
5770 prev->comm, prev->pid, preempt_count());
5771
5772 debug_show_held_locks(prev);
5773 print_modules();
5774 if (irqs_disabled())
5775 print_irqtrace_events(prev);
5776 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
5777 && in_atomic_preempt_off()) {
5778 pr_err("Preemption disabled at:");
5779 print_ip_sym(KERN_ERR, preempt_disable_ip);
5780 }
5781 check_panic_on_warn("scheduling while atomic");
5782
5783 dump_stack();
5784 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
5785 }
5786
5787 /*
5788 * Various schedule()-time debugging checks and statistics:
5789 */
schedule_debug(struct task_struct * prev,bool preempt)5790 static inline void schedule_debug(struct task_struct *prev, bool preempt)
5791 {
5792 #ifdef CONFIG_SCHED_STACK_END_CHECK
5793 if (task_stack_end_corrupted(prev))
5794 panic("corrupted stack end detected inside scheduler\n");
5795
5796 if (task_scs_end_corrupted(prev))
5797 panic("corrupted shadow stack detected inside scheduler\n");
5798 #endif
5799
5800 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
5801 if (!preempt && READ_ONCE(prev->__state) && prev->non_block_count) {
5802 printk(KERN_ERR "BUG: scheduling in a non-blocking section: %s/%d/%i\n",
5803 prev->comm, prev->pid, prev->non_block_count);
5804 dump_stack();
5805 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
5806 }
5807 #endif
5808
5809 if (unlikely(in_atomic_preempt_off())) {
5810 __schedule_bug(prev);
5811 preempt_count_set(PREEMPT_DISABLED);
5812 }
5813 rcu_sleep_check();
5814 SCHED_WARN_ON(ct_state() == CONTEXT_USER);
5815
5816 profile_hit(SCHED_PROFILING, __builtin_return_address(0));
5817
5818 schedstat_inc(this_rq()->sched_count);
5819 }
5820
put_prev_task_balance(struct rq * rq,struct task_struct * prev,struct rq_flags * rf)5821 static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
5822 struct rq_flags *rf)
5823 {
5824 #ifdef CONFIG_SMP
5825 const struct sched_class *class;
5826 /*
5827 * We must do the balancing pass before put_prev_task(), such
5828 * that when we release the rq->lock the task is in the same
5829 * state as before we took rq->lock.
5830 *
5831 * We can terminate the balance pass as soon as we know there is
5832 * a runnable task of @class priority or higher.
5833 */
5834 for_class_range(class, prev->sched_class, &idle_sched_class) {
5835 if (class->balance(rq, prev, rf))
5836 break;
5837 }
5838 #endif
5839
5840 put_prev_task(rq, prev);
5841 }
5842
5843 /*
5844 * Pick up the highest-prio task:
5845 */
5846 static inline struct task_struct *
__pick_next_task(struct rq * rq,struct task_struct * prev,struct rq_flags * rf)5847 __pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
5848 {
5849 const struct sched_class *class;
5850 struct task_struct *p;
5851
5852 /*
5853 * Optimization: we know that if all tasks are in the fair class we can
5854 * call that function directly, but only if the @prev task wasn't of a
5855 * higher scheduling class, because otherwise those lose the
5856 * opportunity to pull in more work from other CPUs.
5857 */
5858 if (likely(!sched_class_above(prev->sched_class, &fair_sched_class) &&
5859 rq->nr_running == rq->cfs.h_nr_running)) {
5860
5861 p = pick_next_task_fair(rq, prev, rf);
5862 if (unlikely(p == RETRY_TASK))
5863 goto restart;
5864
5865 /* Assume the next prioritized class is idle_sched_class */
5866 if (!p) {
5867 put_prev_task(rq, prev);
5868 p = pick_next_task_idle(rq);
5869 }
5870
5871 return p;
5872 }
5873
5874 restart:
5875 put_prev_task_balance(rq, prev, rf);
5876
5877 for_each_class(class) {
5878 p = class->pick_next_task(rq);
5879 if (p)
5880 return p;
5881 }
5882
5883 BUG(); /* The idle class should always have a runnable task. */
5884 }
5885
5886 #ifdef CONFIG_SCHED_CORE
is_task_rq_idle(struct task_struct * t)5887 static inline bool is_task_rq_idle(struct task_struct *t)
5888 {
5889 return (task_rq(t)->idle == t);
5890 }
5891
cookie_equals(struct task_struct * a,unsigned long cookie)5892 static inline bool cookie_equals(struct task_struct *a, unsigned long cookie)
5893 {
5894 return is_task_rq_idle(a) || (a->core_cookie == cookie);
5895 }
5896
cookie_match(struct task_struct * a,struct task_struct * b)5897 static inline bool cookie_match(struct task_struct *a, struct task_struct *b)
5898 {
5899 if (is_task_rq_idle(a) || is_task_rq_idle(b))
5900 return true;
5901
5902 return a->core_cookie == b->core_cookie;
5903 }
5904
pick_task(struct rq * rq)5905 static inline struct task_struct *pick_task(struct rq *rq)
5906 {
5907 const struct sched_class *class;
5908 struct task_struct *p;
5909
5910 for_each_class(class) {
5911 p = class->pick_task(rq);
5912 if (p)
5913 return p;
5914 }
5915
5916 BUG(); /* The idle class should always have a runnable task. */
5917 }
5918
5919 extern void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi);
5920
5921 static void queue_core_balance(struct rq *rq);
5922
5923 static struct task_struct *
pick_next_task(struct rq * rq,struct task_struct * prev,struct rq_flags * rf)5924 pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
5925 {
5926 struct task_struct *next, *p, *max = NULL;
5927 const struct cpumask *smt_mask;
5928 bool fi_before = false;
5929 bool core_clock_updated = (rq == rq->core);
5930 unsigned long cookie;
5931 int i, cpu, occ = 0;
5932 struct rq *rq_i;
5933 bool need_sync;
5934
5935 if (!sched_core_enabled(rq))
5936 return __pick_next_task(rq, prev, rf);
5937
5938 cpu = cpu_of(rq);
5939
5940 /* Stopper task is switching into idle, no need core-wide selection. */
5941 if (cpu_is_offline(cpu)) {
5942 /*
5943 * Reset core_pick so that we don't enter the fastpath when
5944 * coming online. core_pick would already be migrated to
5945 * another cpu during offline.
5946 */
5947 rq->core_pick = NULL;
5948 return __pick_next_task(rq, prev, rf);
5949 }
5950
5951 /*
5952 * If there were no {en,de}queues since we picked (IOW, the task
5953 * pointers are all still valid), and we haven't scheduled the last
5954 * pick yet, do so now.
5955 *
5956 * rq->core_pick can be NULL if no selection was made for a CPU because
5957 * it was either offline or went offline during a sibling's core-wide
5958 * selection. In this case, do a core-wide selection.
5959 */
5960 if (rq->core->core_pick_seq == rq->core->core_task_seq &&
5961 rq->core->core_pick_seq != rq->core_sched_seq &&
5962 rq->core_pick) {
5963 WRITE_ONCE(rq->core_sched_seq, rq->core->core_pick_seq);
5964
5965 next = rq->core_pick;
5966 if (next != prev) {
5967 put_prev_task(rq, prev);
5968 set_next_task(rq, next);
5969 }
5970
5971 rq->core_pick = NULL;
5972 goto out;
5973 }
5974
5975 put_prev_task_balance(rq, prev, rf);
5976
5977 smt_mask = cpu_smt_mask(cpu);
5978 need_sync = !!rq->core->core_cookie;
5979
5980 /* reset state */
5981 rq->core->core_cookie = 0UL;
5982 if (rq->core->core_forceidle_count) {
5983 if (!core_clock_updated) {
5984 update_rq_clock(rq->core);
5985 core_clock_updated = true;
5986 }
5987 sched_core_account_forceidle(rq);
5988 /* reset after accounting force idle */
5989 rq->core->core_forceidle_start = 0;
5990 rq->core->core_forceidle_count = 0;
5991 rq->core->core_forceidle_occupation = 0;
5992 need_sync = true;
5993 fi_before = true;
5994 }
5995
5996 /*
5997 * core->core_task_seq, core->core_pick_seq, rq->core_sched_seq
5998 *
5999 * @task_seq guards the task state ({en,de}queues)
6000 * @pick_seq is the @task_seq we did a selection on
6001 * @sched_seq is the @pick_seq we scheduled
6002 *
6003 * However, preemptions can cause multiple picks on the same task set.
6004 * 'Fix' this by also increasing @task_seq for every pick.
6005 */
6006 rq->core->core_task_seq++;
6007
6008 /*
6009 * Optimize for common case where this CPU has no cookies
6010 * and there are no cookied tasks running on siblings.
6011 */
6012 if (!need_sync) {
6013 next = pick_task(rq);
6014 if (!next->core_cookie) {
6015 rq->core_pick = NULL;
6016 /*
6017 * For robustness, update the min_vruntime_fi for
6018 * unconstrained picks as well.
6019 */
6020 WARN_ON_ONCE(fi_before);
6021 task_vruntime_update(rq, next, false);
6022 goto out_set_next;
6023 }
6024 }
6025
6026 /*
6027 * For each thread: do the regular task pick and find the max prio task
6028 * amongst them.
6029 *
6030 * Tie-break prio towards the current CPU
6031 */
6032 for_each_cpu_wrap(i, smt_mask, cpu) {
6033 rq_i = cpu_rq(i);
6034
6035 /*
6036 * Current cpu always has its clock updated on entrance to
6037 * pick_next_task(). If the current cpu is not the core,
6038 * the core may also have been updated above.
6039 */
6040 if (i != cpu && (rq_i != rq->core || !core_clock_updated))
6041 update_rq_clock(rq_i);
6042
6043 p = rq_i->core_pick = pick_task(rq_i);
6044 if (!max || prio_less(max, p, fi_before))
6045 max = p;
6046 }
6047
6048 cookie = rq->core->core_cookie = max->core_cookie;
6049
6050 /*
6051 * For each thread: try and find a runnable task that matches @max or
6052 * force idle.
6053 */
6054 for_each_cpu(i, smt_mask) {
6055 rq_i = cpu_rq(i);
6056 p = rq_i->core_pick;
6057
6058 if (!cookie_equals(p, cookie)) {
6059 p = NULL;
6060 if (cookie)
6061 p = sched_core_find(rq_i, cookie);
6062 if (!p)
6063 p = idle_sched_class.pick_task(rq_i);
6064 }
6065
6066 rq_i->core_pick = p;
6067
6068 if (p == rq_i->idle) {
6069 if (rq_i->nr_running) {
6070 rq->core->core_forceidle_count++;
6071 if (!fi_before)
6072 rq->core->core_forceidle_seq++;
6073 }
6074 } else {
6075 occ++;
6076 }
6077 }
6078
6079 if (schedstat_enabled() && rq->core->core_forceidle_count) {
6080 rq->core->core_forceidle_start = rq_clock(rq->core);
6081 rq->core->core_forceidle_occupation = occ;
6082 }
6083
6084 rq->core->core_pick_seq = rq->core->core_task_seq;
6085 next = rq->core_pick;
6086 rq->core_sched_seq = rq->core->core_pick_seq;
6087
6088 /* Something should have been selected for current CPU */
6089 WARN_ON_ONCE(!next);
6090
6091 /*
6092 * Reschedule siblings
6093 *
6094 * NOTE: L1TF -- at this point we're no longer running the old task and
6095 * sending an IPI (below) ensures the sibling will no longer be running
6096 * their task. This ensures there is no inter-sibling overlap between
6097 * non-matching user state.
6098 */
6099 for_each_cpu(i, smt_mask) {
6100 rq_i = cpu_rq(i);
6101
6102 /*
6103 * An online sibling might have gone offline before a task
6104 * could be picked for it, or it might be offline but later
6105 * happen to come online, but its too late and nothing was
6106 * picked for it. That's Ok - it will pick tasks for itself,
6107 * so ignore it.
6108 */
6109 if (!rq_i->core_pick)
6110 continue;
6111
6112 /*
6113 * Update for new !FI->FI transitions, or if continuing to be in !FI:
6114 * fi_before fi update?
6115 * 0 0 1
6116 * 0 1 1
6117 * 1 0 1
6118 * 1 1 0
6119 */
6120 if (!(fi_before && rq->core->core_forceidle_count))
6121 task_vruntime_update(rq_i, rq_i->core_pick, !!rq->core->core_forceidle_count);
6122
6123 rq_i->core_pick->core_occupation = occ;
6124
6125 if (i == cpu) {
6126 rq_i->core_pick = NULL;
6127 continue;
6128 }
6129
6130 /* Did we break L1TF mitigation requirements? */
6131 WARN_ON_ONCE(!cookie_match(next, rq_i->core_pick));
6132
6133 if (rq_i->curr == rq_i->core_pick) {
6134 rq_i->core_pick = NULL;
6135 continue;
6136 }
6137
6138 resched_curr(rq_i);
6139 }
6140
6141 out_set_next:
6142 set_next_task(rq, next);
6143 out:
6144 if (rq->core->core_forceidle_count && next == rq->idle)
6145 queue_core_balance(rq);
6146
6147 return next;
6148 }
6149
try_steal_cookie(int this,int that)6150 static bool try_steal_cookie(int this, int that)
6151 {
6152 struct rq *dst = cpu_rq(this), *src = cpu_rq(that);
6153 struct task_struct *p;
6154 unsigned long cookie;
6155 bool success = false;
6156
6157 local_irq_disable();
6158 double_rq_lock(dst, src);
6159
6160 cookie = dst->core->core_cookie;
6161 if (!cookie)
6162 goto unlock;
6163
6164 if (dst->curr != dst->idle)
6165 goto unlock;
6166
6167 p = sched_core_find(src, cookie);
6168 if (p == src->idle)
6169 goto unlock;
6170
6171 do {
6172 if (p == src->core_pick || p == src->curr)
6173 goto next;
6174
6175 if (!is_cpu_allowed(p, this))
6176 goto next;
6177
6178 if (p->core_occupation > dst->idle->core_occupation)
6179 goto next;
6180
6181 deactivate_task(src, p, 0);
6182 set_task_cpu(p, this);
6183 activate_task(dst, p, 0);
6184
6185 resched_curr(dst);
6186
6187 success = true;
6188 break;
6189
6190 next:
6191 p = sched_core_next(p, cookie);
6192 } while (p);
6193
6194 unlock:
6195 double_rq_unlock(dst, src);
6196 local_irq_enable();
6197
6198 return success;
6199 }
6200
steal_cookie_task(int cpu,struct sched_domain * sd)6201 static bool steal_cookie_task(int cpu, struct sched_domain *sd)
6202 {
6203 int i;
6204
6205 for_each_cpu_wrap(i, sched_domain_span(sd), cpu) {
6206 if (i == cpu)
6207 continue;
6208
6209 if (need_resched())
6210 break;
6211
6212 if (try_steal_cookie(cpu, i))
6213 return true;
6214 }
6215
6216 return false;
6217 }
6218
sched_core_balance(struct rq * rq)6219 static void sched_core_balance(struct rq *rq)
6220 {
6221 struct sched_domain *sd;
6222 int cpu = cpu_of(rq);
6223
6224 preempt_disable();
6225 rcu_read_lock();
6226 raw_spin_rq_unlock_irq(rq);
6227 for_each_domain(cpu, sd) {
6228 if (need_resched())
6229 break;
6230
6231 if (steal_cookie_task(cpu, sd))
6232 break;
6233 }
6234 raw_spin_rq_lock_irq(rq);
6235 rcu_read_unlock();
6236 preempt_enable();
6237 }
6238
6239 static DEFINE_PER_CPU(struct balance_callback, core_balance_head);
6240
queue_core_balance(struct rq * rq)6241 static void queue_core_balance(struct rq *rq)
6242 {
6243 if (!sched_core_enabled(rq))
6244 return;
6245
6246 if (!rq->core->core_cookie)
6247 return;
6248
6249 if (!rq->nr_running) /* not forced idle */
6250 return;
6251
6252 queue_balance_callback(rq, &per_cpu(core_balance_head, rq->cpu), sched_core_balance);
6253 }
6254
sched_core_cpu_starting(unsigned int cpu)6255 static void sched_core_cpu_starting(unsigned int cpu)
6256 {
6257 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
6258 struct rq *rq = cpu_rq(cpu), *core_rq = NULL;
6259 unsigned long flags;
6260 int t;
6261
6262 sched_core_lock(cpu, &flags);
6263
6264 WARN_ON_ONCE(rq->core != rq);
6265
6266 /* if we're the first, we'll be our own leader */
6267 if (cpumask_weight(smt_mask) == 1)
6268 goto unlock;
6269
6270 /* find the leader */
6271 for_each_cpu(t, smt_mask) {
6272 if (t == cpu)
6273 continue;
6274 rq = cpu_rq(t);
6275 if (rq->core == rq) {
6276 core_rq = rq;
6277 break;
6278 }
6279 }
6280
6281 if (WARN_ON_ONCE(!core_rq)) /* whoopsie */
6282 goto unlock;
6283
6284 /* install and validate core_rq */
6285 for_each_cpu(t, smt_mask) {
6286 rq = cpu_rq(t);
6287
6288 if (t == cpu)
6289 rq->core = core_rq;
6290
6291 WARN_ON_ONCE(rq->core != core_rq);
6292 }
6293
6294 unlock:
6295 sched_core_unlock(cpu, &flags);
6296 }
6297
sched_core_cpu_deactivate(unsigned int cpu)6298 static void sched_core_cpu_deactivate(unsigned int cpu)
6299 {
6300 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
6301 struct rq *rq = cpu_rq(cpu), *core_rq = NULL;
6302 unsigned long flags;
6303 int t;
6304
6305 sched_core_lock(cpu, &flags);
6306
6307 /* if we're the last man standing, nothing to do */
6308 if (cpumask_weight(smt_mask) == 1) {
6309 WARN_ON_ONCE(rq->core != rq);
6310 goto unlock;
6311 }
6312
6313 /* if we're not the leader, nothing to do */
6314 if (rq->core != rq)
6315 goto unlock;
6316
6317 /* find a new leader */
6318 for_each_cpu(t, smt_mask) {
6319 if (t == cpu)
6320 continue;
6321 core_rq = cpu_rq(t);
6322 break;
6323 }
6324
6325 if (WARN_ON_ONCE(!core_rq)) /* impossible */
6326 goto unlock;
6327
6328 /* copy the shared state to the new leader */
6329 core_rq->core_task_seq = rq->core_task_seq;
6330 core_rq->core_pick_seq = rq->core_pick_seq;
6331 core_rq->core_cookie = rq->core_cookie;
6332 core_rq->core_forceidle_count = rq->core_forceidle_count;
6333 core_rq->core_forceidle_seq = rq->core_forceidle_seq;
6334 core_rq->core_forceidle_occupation = rq->core_forceidle_occupation;
6335
6336 /*
6337 * Accounting edge for forced idle is handled in pick_next_task().
6338 * Don't need another one here, since the hotplug thread shouldn't
6339 * have a cookie.
6340 */
6341 core_rq->core_forceidle_start = 0;
6342
6343 /* install new leader */
6344 for_each_cpu(t, smt_mask) {
6345 rq = cpu_rq(t);
6346 rq->core = core_rq;
6347 }
6348
6349 unlock:
6350 sched_core_unlock(cpu, &flags);
6351 }
6352
sched_core_cpu_dying(unsigned int cpu)6353 static inline void sched_core_cpu_dying(unsigned int cpu)
6354 {
6355 struct rq *rq = cpu_rq(cpu);
6356
6357 if (rq->core != rq)
6358 rq->core = rq;
6359 }
6360
6361 #else /* !CONFIG_SCHED_CORE */
6362
sched_core_cpu_starting(unsigned int cpu)6363 static inline void sched_core_cpu_starting(unsigned int cpu) {}
sched_core_cpu_deactivate(unsigned int cpu)6364 static inline void sched_core_cpu_deactivate(unsigned int cpu) {}
sched_core_cpu_dying(unsigned int cpu)6365 static inline void sched_core_cpu_dying(unsigned int cpu) {}
6366
6367 static struct task_struct *
pick_next_task(struct rq * rq,struct task_struct * prev,struct rq_flags * rf)6368 pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6369 {
6370 return __pick_next_task(rq, prev, rf);
6371 }
6372
6373 #endif /* CONFIG_SCHED_CORE */
6374
6375 /*
6376 * Constants for the sched_mode argument of __schedule().
6377 *
6378 * The mode argument allows RT enabled kernels to differentiate a
6379 * preemption from blocking on an 'sleeping' spin/rwlock. Note that
6380 * SM_MASK_PREEMPT for !RT has all bits set, which allows the compiler to
6381 * optimize the AND operation out and just check for zero.
6382 */
6383 #define SM_NONE 0x0
6384 #define SM_PREEMPT 0x1
6385 #define SM_RTLOCK_WAIT 0x2
6386
6387 #ifndef CONFIG_PREEMPT_RT
6388 # define SM_MASK_PREEMPT (~0U)
6389 #else
6390 # define SM_MASK_PREEMPT SM_PREEMPT
6391 #endif
6392
6393 /*
6394 * __schedule() is the main scheduler function.
6395 *
6396 * The main means of driving the scheduler and thus entering this function are:
6397 *
6398 * 1. Explicit blocking: mutex, semaphore, waitqueue, etc.
6399 *
6400 * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
6401 * paths. For example, see arch/x86/entry_64.S.
6402 *
6403 * To drive preemption between tasks, the scheduler sets the flag in timer
6404 * interrupt handler scheduler_tick().
6405 *
6406 * 3. Wakeups don't really cause entry into schedule(). They add a
6407 * task to the run-queue and that's it.
6408 *
6409 * Now, if the new task added to the run-queue preempts the current
6410 * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
6411 * called on the nearest possible occasion:
6412 *
6413 * - If the kernel is preemptible (CONFIG_PREEMPTION=y):
6414 *
6415 * - in syscall or exception context, at the next outmost
6416 * preempt_enable(). (this might be as soon as the wake_up()'s
6417 * spin_unlock()!)
6418 *
6419 * - in IRQ context, return from interrupt-handler to
6420 * preemptible context
6421 *
6422 * - If the kernel is not preemptible (CONFIG_PREEMPTION is not set)
6423 * then at the next:
6424 *
6425 * - cond_resched() call
6426 * - explicit schedule() call
6427 * - return from syscall or exception to user-space
6428 * - return from interrupt-handler to user-space
6429 *
6430 * WARNING: must be called with preemption disabled!
6431 */
__schedule(unsigned int sched_mode)6432 static void __sched notrace __schedule(unsigned int sched_mode)
6433 {
6434 struct task_struct *prev, *next;
6435 unsigned long *switch_count;
6436 unsigned long prev_state;
6437 struct rq_flags rf;
6438 struct rq *rq;
6439 int cpu;
6440
6441 cpu = smp_processor_id();
6442 rq = cpu_rq(cpu);
6443 prev = rq->curr;
6444
6445 schedule_debug(prev, !!sched_mode);
6446
6447 if (sched_feat(HRTICK) || sched_feat(HRTICK_DL))
6448 hrtick_clear(rq);
6449
6450 local_irq_disable();
6451 rcu_note_context_switch(!!sched_mode);
6452
6453 /*
6454 * Make sure that signal_pending_state()->signal_pending() below
6455 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
6456 * done by the caller to avoid the race with signal_wake_up():
6457 *
6458 * __set_current_state(@state) signal_wake_up()
6459 * schedule() set_tsk_thread_flag(p, TIF_SIGPENDING)
6460 * wake_up_state(p, state)
6461 * LOCK rq->lock LOCK p->pi_state
6462 * smp_mb__after_spinlock() smp_mb__after_spinlock()
6463 * if (signal_pending_state()) if (p->state & @state)
6464 *
6465 * Also, the membarrier system call requires a full memory barrier
6466 * after coming from user-space, before storing to rq->curr.
6467 */
6468 rq_lock(rq, &rf);
6469 smp_mb__after_spinlock();
6470
6471 /* Promote REQ to ACT */
6472 rq->clock_update_flags <<= 1;
6473 update_rq_clock(rq);
6474
6475 switch_count = &prev->nivcsw;
6476
6477 /*
6478 * We must load prev->state once (task_struct::state is volatile), such
6479 * that we form a control dependency vs deactivate_task() below.
6480 */
6481 prev_state = READ_ONCE(prev->__state);
6482 if (!(sched_mode & SM_MASK_PREEMPT) && prev_state) {
6483 if (signal_pending_state(prev_state, prev)) {
6484 WRITE_ONCE(prev->__state, TASK_RUNNING);
6485 } else {
6486 prev->sched_contributes_to_load =
6487 (prev_state & TASK_UNINTERRUPTIBLE) &&
6488 !(prev_state & TASK_NOLOAD) &&
6489 !(prev_state & TASK_FROZEN);
6490
6491 if (prev->sched_contributes_to_load)
6492 rq->nr_uninterruptible++;
6493
6494 /*
6495 * __schedule() ttwu()
6496 * prev_state = prev->state; if (p->on_rq && ...)
6497 * if (prev_state) goto out;
6498 * p->on_rq = 0; smp_acquire__after_ctrl_dep();
6499 * p->state = TASK_WAKING
6500 *
6501 * Where __schedule() and ttwu() have matching control dependencies.
6502 *
6503 * After this, schedule() must not care about p->state any more.
6504 */
6505 deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK);
6506
6507 if (prev->in_iowait) {
6508 atomic_inc(&rq->nr_iowait);
6509 delayacct_blkio_start();
6510 }
6511 }
6512 switch_count = &prev->nvcsw;
6513 }
6514
6515 next = pick_next_task(rq, prev, &rf);
6516 clear_tsk_need_resched(prev);
6517 clear_preempt_need_resched();
6518 #ifdef CONFIG_SCHED_DEBUG
6519 rq->last_seen_need_resched_ns = 0;
6520 #endif
6521
6522 if (likely(prev != next)) {
6523 rq->nr_switches++;
6524 /*
6525 * RCU users of rcu_dereference(rq->curr) may not see
6526 * changes to task_struct made by pick_next_task().
6527 */
6528 RCU_INIT_POINTER(rq->curr, next);
6529 /*
6530 * The membarrier system call requires each architecture
6531 * to have a full memory barrier after updating
6532 * rq->curr, before returning to user-space.
6533 *
6534 * Here are the schemes providing that barrier on the
6535 * various architectures:
6536 * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC.
6537 * switch_mm() rely on membarrier_arch_switch_mm() on PowerPC.
6538 * - finish_lock_switch() for weakly-ordered
6539 * architectures where spin_unlock is a full barrier,
6540 * - switch_to() for arm64 (weakly-ordered, spin_unlock
6541 * is a RELEASE barrier),
6542 */
6543 ++*switch_count;
6544
6545 migrate_disable_switch(rq, prev);
6546 psi_sched_switch(prev, next, !task_on_rq_queued(prev));
6547
6548 trace_sched_switch(sched_mode & SM_MASK_PREEMPT, prev, next, prev_state);
6549
6550 /* Also unlocks the rq: */
6551 rq = context_switch(rq, prev, next, &rf);
6552 } else {
6553 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
6554
6555 rq_unpin_lock(rq, &rf);
6556 __balance_callbacks(rq);
6557 raw_spin_rq_unlock_irq(rq);
6558 }
6559 }
6560
do_task_dead(void)6561 void __noreturn do_task_dead(void)
6562 {
6563 /* Causes final put_task_struct in finish_task_switch(): */
6564 set_special_state(TASK_DEAD);
6565
6566 /* Tell freezer to ignore us: */
6567 current->flags |= PF_NOFREEZE;
6568
6569 __schedule(SM_NONE);
6570 BUG();
6571
6572 /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
6573 for (;;)
6574 cpu_relax();
6575 }
6576
sched_submit_work(struct task_struct * tsk)6577 static inline void sched_submit_work(struct task_struct *tsk)
6578 {
6579 unsigned int task_flags;
6580
6581 if (task_is_running(tsk))
6582 return;
6583
6584 task_flags = tsk->flags;
6585 /*
6586 * If a worker goes to sleep, notify and ask workqueue whether it
6587 * wants to wake up a task to maintain concurrency.
6588 */
6589 if (task_flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
6590 if (task_flags & PF_WQ_WORKER)
6591 wq_worker_sleeping(tsk);
6592 else
6593 io_wq_worker_sleeping(tsk);
6594 }
6595
6596 /*
6597 * spinlock and rwlock must not flush block requests. This will
6598 * deadlock if the callback attempts to acquire a lock which is
6599 * already acquired.
6600 */
6601 SCHED_WARN_ON(current->__state & TASK_RTLOCK_WAIT);
6602
6603 /*
6604 * If we are going to sleep and we have plugged IO queued,
6605 * make sure to submit it to avoid deadlocks.
6606 */
6607 blk_flush_plug(tsk->plug, true);
6608 }
6609
sched_update_worker(struct task_struct * tsk)6610 static void sched_update_worker(struct task_struct *tsk)
6611 {
6612 if (tsk->flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
6613 if (tsk->flags & PF_WQ_WORKER)
6614 wq_worker_running(tsk);
6615 else
6616 io_wq_worker_running(tsk);
6617 }
6618 }
6619
schedule(void)6620 asmlinkage __visible void __sched schedule(void)
6621 {
6622 struct task_struct *tsk = current;
6623
6624 sched_submit_work(tsk);
6625 do {
6626 preempt_disable();
6627 __schedule(SM_NONE);
6628 sched_preempt_enable_no_resched();
6629 } while (need_resched());
6630 sched_update_worker(tsk);
6631 }
6632 EXPORT_SYMBOL(schedule);
6633
6634 /*
6635 * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
6636 * state (have scheduled out non-voluntarily) by making sure that all
6637 * tasks have either left the run queue or have gone into user space.
6638 * As idle tasks do not do either, they must not ever be preempted
6639 * (schedule out non-voluntarily).
6640 *
6641 * schedule_idle() is similar to schedule_preempt_disable() except that it
6642 * never enables preemption because it does not call sched_submit_work().
6643 */
schedule_idle(void)6644 void __sched schedule_idle(void)
6645 {
6646 /*
6647 * As this skips calling sched_submit_work(), which the idle task does
6648 * regardless because that function is a nop when the task is in a
6649 * TASK_RUNNING state, make sure this isn't used someplace that the
6650 * current task can be in any other state. Note, idle is always in the
6651 * TASK_RUNNING state.
6652 */
6653 WARN_ON_ONCE(current->__state);
6654 do {
6655 __schedule(SM_NONE);
6656 } while (need_resched());
6657 }
6658
6659 #if defined(CONFIG_CONTEXT_TRACKING_USER) && !defined(CONFIG_HAVE_CONTEXT_TRACKING_USER_OFFSTACK)
schedule_user(void)6660 asmlinkage __visible void __sched schedule_user(void)
6661 {
6662 /*
6663 * If we come here after a random call to set_need_resched(),
6664 * or we have been woken up remotely but the IPI has not yet arrived,
6665 * we haven't yet exited the RCU idle mode. Do it here manually until
6666 * we find a better solution.
6667 *
6668 * NB: There are buggy callers of this function. Ideally we
6669 * should warn if prev_state != CONTEXT_USER, but that will trigger
6670 * too frequently to make sense yet.
6671 */
6672 enum ctx_state prev_state = exception_enter();
6673 schedule();
6674 exception_exit(prev_state);
6675 }
6676 #endif
6677
6678 /**
6679 * schedule_preempt_disabled - called with preemption disabled
6680 *
6681 * Returns with preemption disabled. Note: preempt_count must be 1
6682 */
schedule_preempt_disabled(void)6683 void __sched schedule_preempt_disabled(void)
6684 {
6685 sched_preempt_enable_no_resched();
6686 schedule();
6687 preempt_disable();
6688 }
6689
6690 #ifdef CONFIG_PREEMPT_RT
schedule_rtlock(void)6691 void __sched notrace schedule_rtlock(void)
6692 {
6693 do {
6694 preempt_disable();
6695 __schedule(SM_RTLOCK_WAIT);
6696 sched_preempt_enable_no_resched();
6697 } while (need_resched());
6698 }
6699 NOKPROBE_SYMBOL(schedule_rtlock);
6700 #endif
6701
preempt_schedule_common(void)6702 static void __sched notrace preempt_schedule_common(void)
6703 {
6704 do {
6705 /*
6706 * Because the function tracer can trace preempt_count_sub()
6707 * and it also uses preempt_enable/disable_notrace(), if
6708 * NEED_RESCHED is set, the preempt_enable_notrace() called
6709 * by the function tracer will call this function again and
6710 * cause infinite recursion.
6711 *
6712 * Preemption must be disabled here before the function
6713 * tracer can trace. Break up preempt_disable() into two
6714 * calls. One to disable preemption without fear of being
6715 * traced. The other to still record the preemption latency,
6716 * which can also be traced by the function tracer.
6717 */
6718 preempt_disable_notrace();
6719 preempt_latency_start(1);
6720 __schedule(SM_PREEMPT);
6721 preempt_latency_stop(1);
6722 preempt_enable_no_resched_notrace();
6723
6724 /*
6725 * Check again in case we missed a preemption opportunity
6726 * between schedule and now.
6727 */
6728 } while (need_resched());
6729 }
6730
6731 #ifdef CONFIG_PREEMPTION
6732 /*
6733 * This is the entry point to schedule() from in-kernel preemption
6734 * off of preempt_enable.
6735 */
preempt_schedule(void)6736 asmlinkage __visible void __sched notrace preempt_schedule(void)
6737 {
6738 /*
6739 * If there is a non-zero preempt_count or interrupts are disabled,
6740 * we do not want to preempt the current task. Just return..
6741 */
6742 if (likely(!preemptible()))
6743 return;
6744 preempt_schedule_common();
6745 }
6746 NOKPROBE_SYMBOL(preempt_schedule);
6747 EXPORT_SYMBOL(preempt_schedule);
6748
6749 #ifdef CONFIG_PREEMPT_DYNAMIC
6750 #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
6751 #ifndef preempt_schedule_dynamic_enabled
6752 #define preempt_schedule_dynamic_enabled preempt_schedule
6753 #define preempt_schedule_dynamic_disabled NULL
6754 #endif
6755 DEFINE_STATIC_CALL(preempt_schedule, preempt_schedule_dynamic_enabled);
6756 EXPORT_STATIC_CALL_TRAMP(preempt_schedule);
6757 #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
6758 static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule);
dynamic_preempt_schedule(void)6759 void __sched notrace dynamic_preempt_schedule(void)
6760 {
6761 if (!static_branch_unlikely(&sk_dynamic_preempt_schedule))
6762 return;
6763 preempt_schedule();
6764 }
6765 NOKPROBE_SYMBOL(dynamic_preempt_schedule);
6766 EXPORT_SYMBOL(dynamic_preempt_schedule);
6767 #endif
6768 #endif
6769
6770 /**
6771 * preempt_schedule_notrace - preempt_schedule called by tracing
6772 *
6773 * The tracing infrastructure uses preempt_enable_notrace to prevent
6774 * recursion and tracing preempt enabling caused by the tracing
6775 * infrastructure itself. But as tracing can happen in areas coming
6776 * from userspace or just about to enter userspace, a preempt enable
6777 * can occur before user_exit() is called. This will cause the scheduler
6778 * to be called when the system is still in usermode.
6779 *
6780 * To prevent this, the preempt_enable_notrace will use this function
6781 * instead of preempt_schedule() to exit user context if needed before
6782 * calling the scheduler.
6783 */
preempt_schedule_notrace(void)6784 asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
6785 {
6786 enum ctx_state prev_ctx;
6787
6788 if (likely(!preemptible()))
6789 return;
6790
6791 do {
6792 /*
6793 * Because the function tracer can trace preempt_count_sub()
6794 * and it also uses preempt_enable/disable_notrace(), if
6795 * NEED_RESCHED is set, the preempt_enable_notrace() called
6796 * by the function tracer will call this function again and
6797 * cause infinite recursion.
6798 *
6799 * Preemption must be disabled here before the function
6800 * tracer can trace. Break up preempt_disable() into two
6801 * calls. One to disable preemption without fear of being
6802 * traced. The other to still record the preemption latency,
6803 * which can also be traced by the function tracer.
6804 */
6805 preempt_disable_notrace();
6806 preempt_latency_start(1);
6807 /*
6808 * Needs preempt disabled in case user_exit() is traced
6809 * and the tracer calls preempt_enable_notrace() causing
6810 * an infinite recursion.
6811 */
6812 prev_ctx = exception_enter();
6813 __schedule(SM_PREEMPT);
6814 exception_exit(prev_ctx);
6815
6816 preempt_latency_stop(1);
6817 preempt_enable_no_resched_notrace();
6818 } while (need_resched());
6819 }
6820 EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
6821
6822 #ifdef CONFIG_PREEMPT_DYNAMIC
6823 #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
6824 #ifndef preempt_schedule_notrace_dynamic_enabled
6825 #define preempt_schedule_notrace_dynamic_enabled preempt_schedule_notrace
6826 #define preempt_schedule_notrace_dynamic_disabled NULL
6827 #endif
6828 DEFINE_STATIC_CALL(preempt_schedule_notrace, preempt_schedule_notrace_dynamic_enabled);
6829 EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace);
6830 #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
6831 static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule_notrace);
dynamic_preempt_schedule_notrace(void)6832 void __sched notrace dynamic_preempt_schedule_notrace(void)
6833 {
6834 if (!static_branch_unlikely(&sk_dynamic_preempt_schedule_notrace))
6835 return;
6836 preempt_schedule_notrace();
6837 }
6838 NOKPROBE_SYMBOL(dynamic_preempt_schedule_notrace);
6839 EXPORT_SYMBOL(dynamic_preempt_schedule_notrace);
6840 #endif
6841 #endif
6842
6843 #endif /* CONFIG_PREEMPTION */
6844
6845 /*
6846 * This is the entry point to schedule() from kernel preemption
6847 * off of irq context.
6848 * Note, that this is called and return with irqs disabled. This will
6849 * protect us against recursive calling from irq.
6850 */
preempt_schedule_irq(void)6851 asmlinkage __visible void __sched preempt_schedule_irq(void)
6852 {
6853 enum ctx_state prev_state;
6854
6855 /* Catch callers which need to be fixed */
6856 BUG_ON(preempt_count() || !irqs_disabled());
6857
6858 prev_state = exception_enter();
6859
6860 do {
6861 preempt_disable();
6862 local_irq_enable();
6863 __schedule(SM_PREEMPT);
6864 local_irq_disable();
6865 sched_preempt_enable_no_resched();
6866 } while (need_resched());
6867
6868 exception_exit(prev_state);
6869 }
6870
default_wake_function(wait_queue_entry_t * curr,unsigned mode,int wake_flags,void * key)6871 int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
6872 void *key)
6873 {
6874 WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG) && wake_flags & ~WF_SYNC);
6875 return try_to_wake_up(curr->private, mode, wake_flags);
6876 }
6877 EXPORT_SYMBOL(default_wake_function);
6878
__setscheduler_prio(struct task_struct * p,int prio)6879 static void __setscheduler_prio(struct task_struct *p, int prio)
6880 {
6881 if (dl_prio(prio))
6882 p->sched_class = &dl_sched_class;
6883 else if (rt_prio(prio))
6884 p->sched_class = &rt_sched_class;
6885 else
6886 p->sched_class = &fair_sched_class;
6887
6888 p->prio = prio;
6889 }
6890
6891 #ifdef CONFIG_RT_MUTEXES
6892
__rt_effective_prio(struct task_struct * pi_task,int prio)6893 static inline int __rt_effective_prio(struct task_struct *pi_task, int prio)
6894 {
6895 if (pi_task)
6896 prio = min(prio, pi_task->prio);
6897
6898 return prio;
6899 }
6900
rt_effective_prio(struct task_struct * p,int prio)6901 static inline int rt_effective_prio(struct task_struct *p, int prio)
6902 {
6903 struct task_struct *pi_task = rt_mutex_get_top_task(p);
6904
6905 return __rt_effective_prio(pi_task, prio);
6906 }
6907
6908 /*
6909 * rt_mutex_setprio - set the current priority of a task
6910 * @p: task to boost
6911 * @pi_task: donor task
6912 *
6913 * This function changes the 'effective' priority of a task. It does
6914 * not touch ->normal_prio like __setscheduler().
6915 *
6916 * Used by the rt_mutex code to implement priority inheritance
6917 * logic. Call site only calls if the priority of the task changed.
6918 */
rt_mutex_setprio(struct task_struct * p,struct task_struct * pi_task)6919 void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
6920 {
6921 int prio, oldprio, queued, running, queue_flag =
6922 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
6923 const struct sched_class *prev_class;
6924 struct rq_flags rf;
6925 struct rq *rq;
6926
6927 /* XXX used to be waiter->prio, not waiter->task->prio */
6928 prio = __rt_effective_prio(pi_task, p->normal_prio);
6929
6930 /*
6931 * If nothing changed; bail early.
6932 */
6933 if (p->pi_top_task == pi_task && prio == p->prio && !dl_prio(prio))
6934 return;
6935
6936 rq = __task_rq_lock(p, &rf);
6937 update_rq_clock(rq);
6938 /*
6939 * Set under pi_lock && rq->lock, such that the value can be used under
6940 * either lock.
6941 *
6942 * Note that there is loads of tricky to make this pointer cache work
6943 * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
6944 * ensure a task is de-boosted (pi_task is set to NULL) before the
6945 * task is allowed to run again (and can exit). This ensures the pointer
6946 * points to a blocked task -- which guarantees the task is present.
6947 */
6948 p->pi_top_task = pi_task;
6949
6950 /*
6951 * For FIFO/RR we only need to set prio, if that matches we're done.
6952 */
6953 if (prio == p->prio && !dl_prio(prio))
6954 goto out_unlock;
6955
6956 /*
6957 * Idle task boosting is a nono in general. There is one
6958 * exception, when PREEMPT_RT and NOHZ is active:
6959 *
6960 * The idle task calls get_next_timer_interrupt() and holds
6961 * the timer wheel base->lock on the CPU and another CPU wants
6962 * to access the timer (probably to cancel it). We can safely
6963 * ignore the boosting request, as the idle CPU runs this code
6964 * with interrupts disabled and will complete the lock
6965 * protected section without being interrupted. So there is no
6966 * real need to boost.
6967 */
6968 if (unlikely(p == rq->idle)) {
6969 WARN_ON(p != rq->curr);
6970 WARN_ON(p->pi_blocked_on);
6971 goto out_unlock;
6972 }
6973
6974 trace_sched_pi_setprio(p, pi_task);
6975 oldprio = p->prio;
6976
6977 if (oldprio == prio)
6978 queue_flag &= ~DEQUEUE_MOVE;
6979
6980 prev_class = p->sched_class;
6981 queued = task_on_rq_queued(p);
6982 running = task_current(rq, p);
6983 if (queued)
6984 dequeue_task(rq, p, queue_flag);
6985 if (running)
6986 put_prev_task(rq, p);
6987
6988 /*
6989 * Boosting condition are:
6990 * 1. -rt task is running and holds mutex A
6991 * --> -dl task blocks on mutex A
6992 *
6993 * 2. -dl task is running and holds mutex A
6994 * --> -dl task blocks on mutex A and could preempt the
6995 * running task
6996 */
6997 if (dl_prio(prio)) {
6998 if (!dl_prio(p->normal_prio) ||
6999 (pi_task && dl_prio(pi_task->prio) &&
7000 dl_entity_preempt(&pi_task->dl, &p->dl))) {
7001 p->dl.pi_se = pi_task->dl.pi_se;
7002 queue_flag |= ENQUEUE_REPLENISH;
7003 } else {
7004 p->dl.pi_se = &p->dl;
7005 }
7006 } else if (rt_prio(prio)) {
7007 if (dl_prio(oldprio))
7008 p->dl.pi_se = &p->dl;
7009 if (oldprio < prio)
7010 queue_flag |= ENQUEUE_HEAD;
7011 } else {
7012 if (dl_prio(oldprio))
7013 p->dl.pi_se = &p->dl;
7014 if (rt_prio(oldprio))
7015 p->rt.timeout = 0;
7016 }
7017
7018 __setscheduler_prio(p, prio);
7019
7020 if (queued)
7021 enqueue_task(rq, p, queue_flag);
7022 if (running)
7023 set_next_task(rq, p);
7024
7025 check_class_changed(rq, p, prev_class, oldprio);
7026 out_unlock:
7027 /* Avoid rq from going away on us: */
7028 preempt_disable();
7029
7030 rq_unpin_lock(rq, &rf);
7031 __balance_callbacks(rq);
7032 raw_spin_rq_unlock(rq);
7033
7034 preempt_enable();
7035 }
7036 #else
rt_effective_prio(struct task_struct * p,int prio)7037 static inline int rt_effective_prio(struct task_struct *p, int prio)
7038 {
7039 return prio;
7040 }
7041 #endif
7042
set_user_nice(struct task_struct * p,long nice)7043 void set_user_nice(struct task_struct *p, long nice)
7044 {
7045 bool queued, running;
7046 int old_prio;
7047 struct rq_flags rf;
7048 struct rq *rq;
7049
7050 if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
7051 return;
7052 /*
7053 * We have to be careful, if called from sys_setpriority(),
7054 * the task might be in the middle of scheduling on another CPU.
7055 */
7056 rq = task_rq_lock(p, &rf);
7057 update_rq_clock(rq);
7058
7059 /*
7060 * The RT priorities are set via sched_setscheduler(), but we still
7061 * allow the 'normal' nice value to be set - but as expected
7062 * it won't have any effect on scheduling until the task is
7063 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
7064 */
7065 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
7066 p->static_prio = NICE_TO_PRIO(nice);
7067 goto out_unlock;
7068 }
7069 queued = task_on_rq_queued(p);
7070 running = task_current(rq, p);
7071 if (queued)
7072 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
7073 if (running)
7074 put_prev_task(rq, p);
7075
7076 p->static_prio = NICE_TO_PRIO(nice);
7077 set_load_weight(p, true);
7078 old_prio = p->prio;
7079 p->prio = effective_prio(p);
7080
7081 if (queued)
7082 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
7083 if (running)
7084 set_next_task(rq, p);
7085
7086 /*
7087 * If the task increased its priority or is running and
7088 * lowered its priority, then reschedule its CPU:
7089 */
7090 p->sched_class->prio_changed(rq, p, old_prio);
7091
7092 out_unlock:
7093 task_rq_unlock(rq, p, &rf);
7094 }
7095 EXPORT_SYMBOL(set_user_nice);
7096
7097 /*
7098 * is_nice_reduction - check if nice value is an actual reduction
7099 *
7100 * Similar to can_nice() but does not perform a capability check.
7101 *
7102 * @p: task
7103 * @nice: nice value
7104 */
is_nice_reduction(const struct task_struct * p,const int nice)7105 static bool is_nice_reduction(const struct task_struct *p, const int nice)
7106 {
7107 /* Convert nice value [19,-20] to rlimit style value [1,40]: */
7108 int nice_rlim = nice_to_rlimit(nice);
7109
7110 return (nice_rlim <= task_rlimit(p, RLIMIT_NICE));
7111 }
7112
7113 /*
7114 * can_nice - check if a task can reduce its nice value
7115 * @p: task
7116 * @nice: nice value
7117 */
can_nice(const struct task_struct * p,const int nice)7118 int can_nice(const struct task_struct *p, const int nice)
7119 {
7120 return is_nice_reduction(p, nice) || capable(CAP_SYS_NICE);
7121 }
7122
7123 #ifdef __ARCH_WANT_SYS_NICE
7124
7125 /*
7126 * sys_nice - change the priority of the current process.
7127 * @increment: priority increment
7128 *
7129 * sys_setpriority is a more generic, but much slower function that
7130 * does similar things.
7131 */
SYSCALL_DEFINE1(nice,int,increment)7132 SYSCALL_DEFINE1(nice, int, increment)
7133 {
7134 long nice, retval;
7135
7136 /*
7137 * Setpriority might change our priority at the same moment.
7138 * We don't have to worry. Conceptually one call occurs first
7139 * and we have a single winner.
7140 */
7141 increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
7142 nice = task_nice(current) + increment;
7143
7144 nice = clamp_val(nice, MIN_NICE, MAX_NICE);
7145 if (increment < 0 && !can_nice(current, nice))
7146 return -EPERM;
7147
7148 retval = security_task_setnice(current, nice);
7149 if (retval)
7150 return retval;
7151
7152 set_user_nice(current, nice);
7153 return 0;
7154 }
7155
7156 #endif
7157
7158 /**
7159 * task_prio - return the priority value of a given task.
7160 * @p: the task in question.
7161 *
7162 * Return: The priority value as seen by users in /proc.
7163 *
7164 * sched policy return value kernel prio user prio/nice
7165 *
7166 * normal, batch, idle [0 ... 39] [100 ... 139] 0/[-20 ... 19]
7167 * fifo, rr [-2 ... -100] [98 ... 0] [1 ... 99]
7168 * deadline -101 -1 0
7169 */
task_prio(const struct task_struct * p)7170 int task_prio(const struct task_struct *p)
7171 {
7172 return p->prio - MAX_RT_PRIO;
7173 }
7174
7175 /**
7176 * idle_cpu - is a given CPU idle currently?
7177 * @cpu: the processor in question.
7178 *
7179 * Return: 1 if the CPU is currently idle. 0 otherwise.
7180 */
idle_cpu(int cpu)7181 int idle_cpu(int cpu)
7182 {
7183 struct rq *rq = cpu_rq(cpu);
7184
7185 if (rq->curr != rq->idle)
7186 return 0;
7187
7188 if (rq->nr_running)
7189 return 0;
7190
7191 #ifdef CONFIG_SMP
7192 if (rq->ttwu_pending)
7193 return 0;
7194 #endif
7195
7196 return 1;
7197 }
7198
7199 /**
7200 * available_idle_cpu - is a given CPU idle for enqueuing work.
7201 * @cpu: the CPU in question.
7202 *
7203 * Return: 1 if the CPU is currently idle. 0 otherwise.
7204 */
available_idle_cpu(int cpu)7205 int available_idle_cpu(int cpu)
7206 {
7207 if (!idle_cpu(cpu))
7208 return 0;
7209
7210 if (vcpu_is_preempted(cpu))
7211 return 0;
7212
7213 return 1;
7214 }
7215
7216 /**
7217 * idle_task - return the idle task for a given CPU.
7218 * @cpu: the processor in question.
7219 *
7220 * Return: The idle task for the CPU @cpu.
7221 */
idle_task(int cpu)7222 struct task_struct *idle_task(int cpu)
7223 {
7224 return cpu_rq(cpu)->idle;
7225 }
7226
7227 #ifdef CONFIG_SMP
7228 /*
7229 * This function computes an effective utilization for the given CPU, to be
7230 * used for frequency selection given the linear relation: f = u * f_max.
7231 *
7232 * The scheduler tracks the following metrics:
7233 *
7234 * cpu_util_{cfs,rt,dl,irq}()
7235 * cpu_bw_dl()
7236 *
7237 * Where the cfs,rt and dl util numbers are tracked with the same metric and
7238 * synchronized windows and are thus directly comparable.
7239 *
7240 * The cfs,rt,dl utilization are the running times measured with rq->clock_task
7241 * which excludes things like IRQ and steal-time. These latter are then accrued
7242 * in the irq utilization.
7243 *
7244 * The DL bandwidth number otoh is not a measured metric but a value computed
7245 * based on the task model parameters and gives the minimal utilization
7246 * required to meet deadlines.
7247 */
effective_cpu_util(int cpu,unsigned long util_cfs,enum cpu_util_type type,struct task_struct * p)7248 unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
7249 enum cpu_util_type type,
7250 struct task_struct *p)
7251 {
7252 unsigned long dl_util, util, irq, max;
7253 struct rq *rq = cpu_rq(cpu);
7254
7255 max = arch_scale_cpu_capacity(cpu);
7256
7257 if (!uclamp_is_used() &&
7258 type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt)) {
7259 return max;
7260 }
7261
7262 /*
7263 * Early check to see if IRQ/steal time saturates the CPU, can be
7264 * because of inaccuracies in how we track these -- see
7265 * update_irq_load_avg().
7266 */
7267 irq = cpu_util_irq(rq);
7268 if (unlikely(irq >= max))
7269 return max;
7270
7271 /*
7272 * Because the time spend on RT/DL tasks is visible as 'lost' time to
7273 * CFS tasks and we use the same metric to track the effective
7274 * utilization (PELT windows are synchronized) we can directly add them
7275 * to obtain the CPU's actual utilization.
7276 *
7277 * CFS and RT utilization can be boosted or capped, depending on
7278 * utilization clamp constraints requested by currently RUNNABLE
7279 * tasks.
7280 * When there are no CFS RUNNABLE tasks, clamps are released and
7281 * frequency will be gracefully reduced with the utilization decay.
7282 */
7283 util = util_cfs + cpu_util_rt(rq);
7284 if (type == FREQUENCY_UTIL)
7285 util = uclamp_rq_util_with(rq, util, p);
7286
7287 dl_util = cpu_util_dl(rq);
7288
7289 /*
7290 * For frequency selection we do not make cpu_util_dl() a permanent part
7291 * of this sum because we want to use cpu_bw_dl() later on, but we need
7292 * to check if the CFS+RT+DL sum is saturated (ie. no idle time) such
7293 * that we select f_max when there is no idle time.
7294 *
7295 * NOTE: numerical errors or stop class might cause us to not quite hit
7296 * saturation when we should -- something for later.
7297 */
7298 if (util + dl_util >= max)
7299 return max;
7300
7301 /*
7302 * OTOH, for energy computation we need the estimated running time, so
7303 * include util_dl and ignore dl_bw.
7304 */
7305 if (type == ENERGY_UTIL)
7306 util += dl_util;
7307
7308 /*
7309 * There is still idle time; further improve the number by using the
7310 * irq metric. Because IRQ/steal time is hidden from the task clock we
7311 * need to scale the task numbers:
7312 *
7313 * max - irq
7314 * U' = irq + --------- * U
7315 * max
7316 */
7317 util = scale_irq_capacity(util, irq, max);
7318 util += irq;
7319
7320 /*
7321 * Bandwidth required by DEADLINE must always be granted while, for
7322 * FAIR and RT, we use blocked utilization of IDLE CPUs as a mechanism
7323 * to gracefully reduce the frequency when no tasks show up for longer
7324 * periods of time.
7325 *
7326 * Ideally we would like to set bw_dl as min/guaranteed freq and util +
7327 * bw_dl as requested freq. However, cpufreq is not yet ready for such
7328 * an interface. So, we only do the latter for now.
7329 */
7330 if (type == FREQUENCY_UTIL)
7331 util += cpu_bw_dl(rq);
7332
7333 return min(max, util);
7334 }
7335
sched_cpu_util(int cpu)7336 unsigned long sched_cpu_util(int cpu)
7337 {
7338 return effective_cpu_util(cpu, cpu_util_cfs(cpu), ENERGY_UTIL, NULL);
7339 }
7340 #endif /* CONFIG_SMP */
7341
7342 /**
7343 * find_process_by_pid - find a process with a matching PID value.
7344 * @pid: the pid in question.
7345 *
7346 * The task of @pid, if found. %NULL otherwise.
7347 */
find_process_by_pid(pid_t pid)7348 static struct task_struct *find_process_by_pid(pid_t pid)
7349 {
7350 return pid ? find_task_by_vpid(pid) : current;
7351 }
7352
7353 /*
7354 * sched_setparam() passes in -1 for its policy, to let the functions
7355 * it calls know not to change it.
7356 */
7357 #define SETPARAM_POLICY -1
7358
__setscheduler_params(struct task_struct * p,const struct sched_attr * attr)7359 static void __setscheduler_params(struct task_struct *p,
7360 const struct sched_attr *attr)
7361 {
7362 int policy = attr->sched_policy;
7363
7364 if (policy == SETPARAM_POLICY)
7365 policy = p->policy;
7366
7367 p->policy = policy;
7368
7369 if (dl_policy(policy))
7370 __setparam_dl(p, attr);
7371 else if (fair_policy(policy))
7372 p->static_prio = NICE_TO_PRIO(attr->sched_nice);
7373
7374 /*
7375 * __sched_setscheduler() ensures attr->sched_priority == 0 when
7376 * !rt_policy. Always setting this ensures that things like
7377 * getparam()/getattr() don't report silly values for !rt tasks.
7378 */
7379 p->rt_priority = attr->sched_priority;
7380 p->normal_prio = normal_prio(p);
7381 set_load_weight(p, true);
7382 }
7383
7384 /*
7385 * Check the target process has a UID that matches the current process's:
7386 */
check_same_owner(struct task_struct * p)7387 static bool check_same_owner(struct task_struct *p)
7388 {
7389 const struct cred *cred = current_cred(), *pcred;
7390 bool match;
7391
7392 rcu_read_lock();
7393 pcred = __task_cred(p);
7394 match = (uid_eq(cred->euid, pcred->euid) ||
7395 uid_eq(cred->euid, pcred->uid));
7396 rcu_read_unlock();
7397 return match;
7398 }
7399
7400 /*
7401 * Allow unprivileged RT tasks to decrease priority.
7402 * Only issue a capable test if needed and only once to avoid an audit
7403 * event on permitted non-privileged operations:
7404 */
user_check_sched_setscheduler(struct task_struct * p,const struct sched_attr * attr,int policy,int reset_on_fork)7405 static int user_check_sched_setscheduler(struct task_struct *p,
7406 const struct sched_attr *attr,
7407 int policy, int reset_on_fork)
7408 {
7409 if (fair_policy(policy)) {
7410 if (attr->sched_nice < task_nice(p) &&
7411 !is_nice_reduction(p, attr->sched_nice))
7412 goto req_priv;
7413 }
7414
7415 if (rt_policy(policy)) {
7416 unsigned long rlim_rtprio = task_rlimit(p, RLIMIT_RTPRIO);
7417
7418 /* Can't set/change the rt policy: */
7419 if (policy != p->policy && !rlim_rtprio)
7420 goto req_priv;
7421
7422 /* Can't increase priority: */
7423 if (attr->sched_priority > p->rt_priority &&
7424 attr->sched_priority > rlim_rtprio)
7425 goto req_priv;
7426 }
7427
7428 /*
7429 * Can't set/change SCHED_DEADLINE policy at all for now
7430 * (safest behavior); in the future we would like to allow
7431 * unprivileged DL tasks to increase their relative deadline
7432 * or reduce their runtime (both ways reducing utilization)
7433 */
7434 if (dl_policy(policy))
7435 goto req_priv;
7436
7437 /*
7438 * Treat SCHED_IDLE as nice 20. Only allow a switch to
7439 * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
7440 */
7441 if (task_has_idle_policy(p) && !idle_policy(policy)) {
7442 if (!is_nice_reduction(p, task_nice(p)))
7443 goto req_priv;
7444 }
7445
7446 /* Can't change other user's priorities: */
7447 if (!check_same_owner(p))
7448 goto req_priv;
7449
7450 /* Normal users shall not reset the sched_reset_on_fork flag: */
7451 if (p->sched_reset_on_fork && !reset_on_fork)
7452 goto req_priv;
7453
7454 return 0;
7455
7456 req_priv:
7457 if (!capable(CAP_SYS_NICE))
7458 return -EPERM;
7459
7460 return 0;
7461 }
7462
__sched_setscheduler(struct task_struct * p,const struct sched_attr * attr,bool user,bool pi)7463 static int __sched_setscheduler(struct task_struct *p,
7464 const struct sched_attr *attr,
7465 bool user, bool pi)
7466 {
7467 int oldpolicy = -1, policy = attr->sched_policy;
7468 int retval, oldprio, newprio, queued, running;
7469 const struct sched_class *prev_class;
7470 struct balance_callback *head;
7471 struct rq_flags rf;
7472 int reset_on_fork;
7473 int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
7474 struct rq *rq;
7475
7476 /* The pi code expects interrupts enabled */
7477 BUG_ON(pi && in_interrupt());
7478 recheck:
7479 /* Double check policy once rq lock held: */
7480 if (policy < 0) {
7481 reset_on_fork = p->sched_reset_on_fork;
7482 policy = oldpolicy = p->policy;
7483 } else {
7484 reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
7485
7486 if (!valid_policy(policy))
7487 return -EINVAL;
7488 }
7489
7490 if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV))
7491 return -EINVAL;
7492
7493 /*
7494 * Valid priorities for SCHED_FIFO and SCHED_RR are
7495 * 1..MAX_RT_PRIO-1, valid priority for SCHED_NORMAL,
7496 * SCHED_BATCH and SCHED_IDLE is 0.
7497 */
7498 if (attr->sched_priority > MAX_RT_PRIO-1)
7499 return -EINVAL;
7500 if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
7501 (rt_policy(policy) != (attr->sched_priority != 0)))
7502 return -EINVAL;
7503
7504 if (user) {
7505 retval = user_check_sched_setscheduler(p, attr, policy, reset_on_fork);
7506 if (retval)
7507 return retval;
7508
7509 if (attr->sched_flags & SCHED_FLAG_SUGOV)
7510 return -EINVAL;
7511
7512 retval = security_task_setscheduler(p);
7513 if (retval)
7514 return retval;
7515 }
7516
7517 /* Update task specific "requested" clamps */
7518 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) {
7519 retval = uclamp_validate(p, attr);
7520 if (retval)
7521 return retval;
7522 }
7523
7524 if (pi)
7525 cpuset_read_lock();
7526
7527 /*
7528 * Make sure no PI-waiters arrive (or leave) while we are
7529 * changing the priority of the task:
7530 *
7531 * To be able to change p->policy safely, the appropriate
7532 * runqueue lock must be held.
7533 */
7534 rq = task_rq_lock(p, &rf);
7535 update_rq_clock(rq);
7536
7537 /*
7538 * Changing the policy of the stop threads its a very bad idea:
7539 */
7540 if (p == rq->stop) {
7541 retval = -EINVAL;
7542 goto unlock;
7543 }
7544
7545 /*
7546 * If not changing anything there's no need to proceed further,
7547 * but store a possible modification of reset_on_fork.
7548 */
7549 if (unlikely(policy == p->policy)) {
7550 if (fair_policy(policy) && attr->sched_nice != task_nice(p))
7551 goto change;
7552 if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
7553 goto change;
7554 if (dl_policy(policy) && dl_param_changed(p, attr))
7555 goto change;
7556 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
7557 goto change;
7558
7559 p->sched_reset_on_fork = reset_on_fork;
7560 retval = 0;
7561 goto unlock;
7562 }
7563 change:
7564
7565 if (user) {
7566 #ifdef CONFIG_RT_GROUP_SCHED
7567 /*
7568 * Do not allow realtime tasks into groups that have no runtime
7569 * assigned.
7570 */
7571 if (rt_bandwidth_enabled() && rt_policy(policy) &&
7572 task_group(p)->rt_bandwidth.rt_runtime == 0 &&
7573 !task_group_is_autogroup(task_group(p))) {
7574 retval = -EPERM;
7575 goto unlock;
7576 }
7577 #endif
7578 #ifdef CONFIG_SMP
7579 if (dl_bandwidth_enabled() && dl_policy(policy) &&
7580 !(attr->sched_flags & SCHED_FLAG_SUGOV)) {
7581 cpumask_t *span = rq->rd->span;
7582
7583 /*
7584 * Don't allow tasks with an affinity mask smaller than
7585 * the entire root_domain to become SCHED_DEADLINE. We
7586 * will also fail if there's no bandwidth available.
7587 */
7588 if (!cpumask_subset(span, p->cpus_ptr) ||
7589 rq->rd->dl_bw.bw == 0) {
7590 retval = -EPERM;
7591 goto unlock;
7592 }
7593 }
7594 #endif
7595 }
7596
7597 /* Re-check policy now with rq lock held: */
7598 if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
7599 policy = oldpolicy = -1;
7600 task_rq_unlock(rq, p, &rf);
7601 if (pi)
7602 cpuset_read_unlock();
7603 goto recheck;
7604 }
7605
7606 /*
7607 * If setscheduling to SCHED_DEADLINE (or changing the parameters
7608 * of a SCHED_DEADLINE task) we need to check if enough bandwidth
7609 * is available.
7610 */
7611 if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) {
7612 retval = -EBUSY;
7613 goto unlock;
7614 }
7615
7616 p->sched_reset_on_fork = reset_on_fork;
7617 oldprio = p->prio;
7618
7619 newprio = __normal_prio(policy, attr->sched_priority, attr->sched_nice);
7620 if (pi) {
7621 /*
7622 * Take priority boosted tasks into account. If the new
7623 * effective priority is unchanged, we just store the new
7624 * normal parameters and do not touch the scheduler class and
7625 * the runqueue. This will be done when the task deboost
7626 * itself.
7627 */
7628 newprio = rt_effective_prio(p, newprio);
7629 if (newprio == oldprio)
7630 queue_flags &= ~DEQUEUE_MOVE;
7631 }
7632
7633 queued = task_on_rq_queued(p);
7634 running = task_current(rq, p);
7635 if (queued)
7636 dequeue_task(rq, p, queue_flags);
7637 if (running)
7638 put_prev_task(rq, p);
7639
7640 prev_class = p->sched_class;
7641
7642 if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) {
7643 __setscheduler_params(p, attr);
7644 __setscheduler_prio(p, newprio);
7645 }
7646 __setscheduler_uclamp(p, attr);
7647
7648 if (queued) {
7649 /*
7650 * We enqueue to tail when the priority of a task is
7651 * increased (user space view).
7652 */
7653 if (oldprio < p->prio)
7654 queue_flags |= ENQUEUE_HEAD;
7655
7656 enqueue_task(rq, p, queue_flags);
7657 }
7658 if (running)
7659 set_next_task(rq, p);
7660
7661 check_class_changed(rq, p, prev_class, oldprio);
7662
7663 /* Avoid rq from going away on us: */
7664 preempt_disable();
7665 head = splice_balance_callbacks(rq);
7666 task_rq_unlock(rq, p, &rf);
7667
7668 if (pi) {
7669 cpuset_read_unlock();
7670 rt_mutex_adjust_pi(p);
7671 }
7672
7673 /* Run balance callbacks after we've adjusted the PI chain: */
7674 balance_callbacks(rq, head);
7675 preempt_enable();
7676
7677 return 0;
7678
7679 unlock:
7680 task_rq_unlock(rq, p, &rf);
7681 if (pi)
7682 cpuset_read_unlock();
7683 return retval;
7684 }
7685
_sched_setscheduler(struct task_struct * p,int policy,const struct sched_param * param,bool check)7686 static int _sched_setscheduler(struct task_struct *p, int policy,
7687 const struct sched_param *param, bool check)
7688 {
7689 struct sched_attr attr = {
7690 .sched_policy = policy,
7691 .sched_priority = param->sched_priority,
7692 .sched_nice = PRIO_TO_NICE(p->static_prio),
7693 };
7694
7695 /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
7696 if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
7697 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
7698 policy &= ~SCHED_RESET_ON_FORK;
7699 attr.sched_policy = policy;
7700 }
7701
7702 return __sched_setscheduler(p, &attr, check, true);
7703 }
7704 /**
7705 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
7706 * @p: the task in question.
7707 * @policy: new policy.
7708 * @param: structure containing the new RT priority.
7709 *
7710 * Use sched_set_fifo(), read its comment.
7711 *
7712 * Return: 0 on success. An error code otherwise.
7713 *
7714 * NOTE that the task may be already dead.
7715 */
sched_setscheduler(struct task_struct * p,int policy,const struct sched_param * param)7716 int sched_setscheduler(struct task_struct *p, int policy,
7717 const struct sched_param *param)
7718 {
7719 return _sched_setscheduler(p, policy, param, true);
7720 }
7721
sched_setattr(struct task_struct * p,const struct sched_attr * attr)7722 int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
7723 {
7724 return __sched_setscheduler(p, attr, true, true);
7725 }
7726
sched_setattr_nocheck(struct task_struct * p,const struct sched_attr * attr)7727 int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr)
7728 {
7729 return __sched_setscheduler(p, attr, false, true);
7730 }
7731 EXPORT_SYMBOL_GPL(sched_setattr_nocheck);
7732
7733 /**
7734 * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
7735 * @p: the task in question.
7736 * @policy: new policy.
7737 * @param: structure containing the new RT priority.
7738 *
7739 * Just like sched_setscheduler, only don't bother checking if the
7740 * current context has permission. For example, this is needed in
7741 * stop_machine(): we create temporary high priority worker threads,
7742 * but our caller might not have that capability.
7743 *
7744 * Return: 0 on success. An error code otherwise.
7745 */
sched_setscheduler_nocheck(struct task_struct * p,int policy,const struct sched_param * param)7746 int sched_setscheduler_nocheck(struct task_struct *p, int policy,
7747 const struct sched_param *param)
7748 {
7749 return _sched_setscheduler(p, policy, param, false);
7750 }
7751
7752 /*
7753 * SCHED_FIFO is a broken scheduler model; that is, it is fundamentally
7754 * incapable of resource management, which is the one thing an OS really should
7755 * be doing.
7756 *
7757 * This is of course the reason it is limited to privileged users only.
7758 *
7759 * Worse still; it is fundamentally impossible to compose static priority
7760 * workloads. You cannot take two correctly working static prio workloads
7761 * and smash them together and still expect them to work.
7762 *
7763 * For this reason 'all' FIFO tasks the kernel creates are basically at:
7764 *
7765 * MAX_RT_PRIO / 2
7766 *
7767 * The administrator _MUST_ configure the system, the kernel simply doesn't
7768 * know enough information to make a sensible choice.
7769 */
sched_set_fifo(struct task_struct * p)7770 void sched_set_fifo(struct task_struct *p)
7771 {
7772 struct sched_param sp = { .sched_priority = MAX_RT_PRIO / 2 };
7773 WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
7774 }
7775 EXPORT_SYMBOL_GPL(sched_set_fifo);
7776
7777 /*
7778 * For when you don't much care about FIFO, but want to be above SCHED_NORMAL.
7779 */
sched_set_fifo_low(struct task_struct * p)7780 void sched_set_fifo_low(struct task_struct *p)
7781 {
7782 struct sched_param sp = { .sched_priority = 1 };
7783 WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
7784 }
7785 EXPORT_SYMBOL_GPL(sched_set_fifo_low);
7786
sched_set_normal(struct task_struct * p,int nice)7787 void sched_set_normal(struct task_struct *p, int nice)
7788 {
7789 struct sched_attr attr = {
7790 .sched_policy = SCHED_NORMAL,
7791 .sched_nice = nice,
7792 };
7793 WARN_ON_ONCE(sched_setattr_nocheck(p, &attr) != 0);
7794 }
7795 EXPORT_SYMBOL_GPL(sched_set_normal);
7796
7797 static int
do_sched_setscheduler(pid_t pid,int policy,struct sched_param __user * param)7798 do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
7799 {
7800 struct sched_param lparam;
7801 struct task_struct *p;
7802 int retval;
7803
7804 if (!param || pid < 0)
7805 return -EINVAL;
7806 if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
7807 return -EFAULT;
7808
7809 rcu_read_lock();
7810 retval = -ESRCH;
7811 p = find_process_by_pid(pid);
7812 if (likely(p))
7813 get_task_struct(p);
7814 rcu_read_unlock();
7815
7816 if (likely(p)) {
7817 retval = sched_setscheduler(p, policy, &lparam);
7818 put_task_struct(p);
7819 }
7820
7821 return retval;
7822 }
7823
7824 /*
7825 * Mimics kernel/events/core.c perf_copy_attr().
7826 */
sched_copy_attr(struct sched_attr __user * uattr,struct sched_attr * attr)7827 static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr)
7828 {
7829 u32 size;
7830 int ret;
7831
7832 /* Zero the full structure, so that a short copy will be nice: */
7833 memset(attr, 0, sizeof(*attr));
7834
7835 ret = get_user(size, &uattr->size);
7836 if (ret)
7837 return ret;
7838
7839 /* ABI compatibility quirk: */
7840 if (!size)
7841 size = SCHED_ATTR_SIZE_VER0;
7842 if (size < SCHED_ATTR_SIZE_VER0 || size > PAGE_SIZE)
7843 goto err_size;
7844
7845 ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size);
7846 if (ret) {
7847 if (ret == -E2BIG)
7848 goto err_size;
7849 return ret;
7850 }
7851
7852 if ((attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) &&
7853 size < SCHED_ATTR_SIZE_VER1)
7854 return -EINVAL;
7855
7856 /*
7857 * XXX: Do we want to be lenient like existing syscalls; or do we want
7858 * to be strict and return an error on out-of-bounds values?
7859 */
7860 attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
7861
7862 return 0;
7863
7864 err_size:
7865 put_user(sizeof(*attr), &uattr->size);
7866 return -E2BIG;
7867 }
7868
get_params(struct task_struct * p,struct sched_attr * attr)7869 static void get_params(struct task_struct *p, struct sched_attr *attr)
7870 {
7871 if (task_has_dl_policy(p))
7872 __getparam_dl(p, attr);
7873 else if (task_has_rt_policy(p))
7874 attr->sched_priority = p->rt_priority;
7875 else
7876 attr->sched_nice = task_nice(p);
7877 }
7878
7879 /**
7880 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
7881 * @pid: the pid in question.
7882 * @policy: new policy.
7883 * @param: structure containing the new RT priority.
7884 *
7885 * Return: 0 on success. An error code otherwise.
7886 */
SYSCALL_DEFINE3(sched_setscheduler,pid_t,pid,int,policy,struct sched_param __user *,param)7887 SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param)
7888 {
7889 if (policy < 0)
7890 return -EINVAL;
7891
7892 return do_sched_setscheduler(pid, policy, param);
7893 }
7894
7895 /**
7896 * sys_sched_setparam - set/change the RT priority of a thread
7897 * @pid: the pid in question.
7898 * @param: structure containing the new RT priority.
7899 *
7900 * Return: 0 on success. An error code otherwise.
7901 */
SYSCALL_DEFINE2(sched_setparam,pid_t,pid,struct sched_param __user *,param)7902 SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
7903 {
7904 return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
7905 }
7906
7907 /**
7908 * sys_sched_setattr - same as above, but with extended sched_attr
7909 * @pid: the pid in question.
7910 * @uattr: structure containing the extended parameters.
7911 * @flags: for future extension.
7912 */
SYSCALL_DEFINE3(sched_setattr,pid_t,pid,struct sched_attr __user *,uattr,unsigned int,flags)7913 SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
7914 unsigned int, flags)
7915 {
7916 struct sched_attr attr;
7917 struct task_struct *p;
7918 int retval;
7919
7920 if (!uattr || pid < 0 || flags)
7921 return -EINVAL;
7922
7923 retval = sched_copy_attr(uattr, &attr);
7924 if (retval)
7925 return retval;
7926
7927 if ((int)attr.sched_policy < 0)
7928 return -EINVAL;
7929 if (attr.sched_flags & SCHED_FLAG_KEEP_POLICY)
7930 attr.sched_policy = SETPARAM_POLICY;
7931
7932 rcu_read_lock();
7933 retval = -ESRCH;
7934 p = find_process_by_pid(pid);
7935 if (likely(p))
7936 get_task_struct(p);
7937 rcu_read_unlock();
7938
7939 if (likely(p)) {
7940 if (attr.sched_flags & SCHED_FLAG_KEEP_PARAMS)
7941 get_params(p, &attr);
7942 retval = sched_setattr(p, &attr);
7943 put_task_struct(p);
7944 }
7945
7946 return retval;
7947 }
7948
7949 /**
7950 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
7951 * @pid: the pid in question.
7952 *
7953 * Return: On success, the policy of the thread. Otherwise, a negative error
7954 * code.
7955 */
SYSCALL_DEFINE1(sched_getscheduler,pid_t,pid)7956 SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
7957 {
7958 struct task_struct *p;
7959 int retval;
7960
7961 if (pid < 0)
7962 return -EINVAL;
7963
7964 retval = -ESRCH;
7965 rcu_read_lock();
7966 p = find_process_by_pid(pid);
7967 if (p) {
7968 retval = security_task_getscheduler(p);
7969 if (!retval)
7970 retval = p->policy
7971 | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
7972 }
7973 rcu_read_unlock();
7974 return retval;
7975 }
7976
7977 /**
7978 * sys_sched_getparam - get the RT priority of a thread
7979 * @pid: the pid in question.
7980 * @param: structure containing the RT priority.
7981 *
7982 * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
7983 * code.
7984 */
SYSCALL_DEFINE2(sched_getparam,pid_t,pid,struct sched_param __user *,param)7985 SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
7986 {
7987 struct sched_param lp = { .sched_priority = 0 };
7988 struct task_struct *p;
7989 int retval;
7990
7991 if (!param || pid < 0)
7992 return -EINVAL;
7993
7994 rcu_read_lock();
7995 p = find_process_by_pid(pid);
7996 retval = -ESRCH;
7997 if (!p)
7998 goto out_unlock;
7999
8000 retval = security_task_getscheduler(p);
8001 if (retval)
8002 goto out_unlock;
8003
8004 if (task_has_rt_policy(p))
8005 lp.sched_priority = p->rt_priority;
8006 rcu_read_unlock();
8007
8008 /*
8009 * This one might sleep, we cannot do it with a spinlock held ...
8010 */
8011 retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
8012
8013 return retval;
8014
8015 out_unlock:
8016 rcu_read_unlock();
8017 return retval;
8018 }
8019
8020 /*
8021 * Copy the kernel size attribute structure (which might be larger
8022 * than what user-space knows about) to user-space.
8023 *
8024 * Note that all cases are valid: user-space buffer can be larger or
8025 * smaller than the kernel-space buffer. The usual case is that both
8026 * have the same size.
8027 */
8028 static int
sched_attr_copy_to_user(struct sched_attr __user * uattr,struct sched_attr * kattr,unsigned int usize)8029 sched_attr_copy_to_user(struct sched_attr __user *uattr,
8030 struct sched_attr *kattr,
8031 unsigned int usize)
8032 {
8033 unsigned int ksize = sizeof(*kattr);
8034
8035 if (!access_ok(uattr, usize))
8036 return -EFAULT;
8037
8038 /*
8039 * sched_getattr() ABI forwards and backwards compatibility:
8040 *
8041 * If usize == ksize then we just copy everything to user-space and all is good.
8042 *
8043 * If usize < ksize then we only copy as much as user-space has space for,
8044 * this keeps ABI compatibility as well. We skip the rest.
8045 *
8046 * If usize > ksize then user-space is using a newer version of the ABI,
8047 * which part the kernel doesn't know about. Just ignore it - tooling can
8048 * detect the kernel's knowledge of attributes from the attr->size value
8049 * which is set to ksize in this case.
8050 */
8051 kattr->size = min(usize, ksize);
8052
8053 if (copy_to_user(uattr, kattr, kattr->size))
8054 return -EFAULT;
8055
8056 return 0;
8057 }
8058
8059 /**
8060 * sys_sched_getattr - similar to sched_getparam, but with sched_attr
8061 * @pid: the pid in question.
8062 * @uattr: structure containing the extended parameters.
8063 * @usize: sizeof(attr) for fwd/bwd comp.
8064 * @flags: for future extension.
8065 */
SYSCALL_DEFINE4(sched_getattr,pid_t,pid,struct sched_attr __user *,uattr,unsigned int,usize,unsigned int,flags)8066 SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
8067 unsigned int, usize, unsigned int, flags)
8068 {
8069 struct sched_attr kattr = { };
8070 struct task_struct *p;
8071 int retval;
8072
8073 if (!uattr || pid < 0 || usize > PAGE_SIZE ||
8074 usize < SCHED_ATTR_SIZE_VER0 || flags)
8075 return -EINVAL;
8076
8077 rcu_read_lock();
8078 p = find_process_by_pid(pid);
8079 retval = -ESRCH;
8080 if (!p)
8081 goto out_unlock;
8082
8083 retval = security_task_getscheduler(p);
8084 if (retval)
8085 goto out_unlock;
8086
8087 kattr.sched_policy = p->policy;
8088 if (p->sched_reset_on_fork)
8089 kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
8090 get_params(p, &kattr);
8091 kattr.sched_flags &= SCHED_FLAG_ALL;
8092
8093 #ifdef CONFIG_UCLAMP_TASK
8094 /*
8095 * This could race with another potential updater, but this is fine
8096 * because it'll correctly read the old or the new value. We don't need
8097 * to guarantee who wins the race as long as it doesn't return garbage.
8098 */
8099 kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
8100 kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
8101 #endif
8102
8103 rcu_read_unlock();
8104
8105 return sched_attr_copy_to_user(uattr, &kattr, usize);
8106
8107 out_unlock:
8108 rcu_read_unlock();
8109 return retval;
8110 }
8111
8112 #ifdef CONFIG_SMP
dl_task_check_affinity(struct task_struct * p,const struct cpumask * mask)8113 int dl_task_check_affinity(struct task_struct *p, const struct cpumask *mask)
8114 {
8115 int ret = 0;
8116
8117 /*
8118 * If the task isn't a deadline task or admission control is
8119 * disabled then we don't care about affinity changes.
8120 */
8121 if (!task_has_dl_policy(p) || !dl_bandwidth_enabled())
8122 return 0;
8123
8124 /*
8125 * Since bandwidth control happens on root_domain basis,
8126 * if admission test is enabled, we only admit -deadline
8127 * tasks allowed to run on all the CPUs in the task's
8128 * root_domain.
8129 */
8130 rcu_read_lock();
8131 if (!cpumask_subset(task_rq(p)->rd->span, mask))
8132 ret = -EBUSY;
8133 rcu_read_unlock();
8134 return ret;
8135 }
8136 #endif
8137
8138 static int
__sched_setaffinity(struct task_struct * p,const struct cpumask * mask)8139 __sched_setaffinity(struct task_struct *p, const struct cpumask *mask)
8140 {
8141 int retval;
8142 cpumask_var_t cpus_allowed, new_mask;
8143
8144 if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL))
8145 return -ENOMEM;
8146
8147 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
8148 retval = -ENOMEM;
8149 goto out_free_cpus_allowed;
8150 }
8151
8152 cpuset_cpus_allowed(p, cpus_allowed);
8153 cpumask_and(new_mask, mask, cpus_allowed);
8154
8155 retval = dl_task_check_affinity(p, new_mask);
8156 if (retval)
8157 goto out_free_new_mask;
8158 again:
8159 retval = __set_cpus_allowed_ptr(p, new_mask, SCA_CHECK | SCA_USER);
8160 if (retval)
8161 goto out_free_new_mask;
8162
8163 cpuset_cpus_allowed(p, cpus_allowed);
8164 if (!cpumask_subset(new_mask, cpus_allowed)) {
8165 /*
8166 * We must have raced with a concurrent cpuset update.
8167 * Just reset the cpumask to the cpuset's cpus_allowed.
8168 */
8169 cpumask_copy(new_mask, cpus_allowed);
8170 goto again;
8171 }
8172
8173 out_free_new_mask:
8174 free_cpumask_var(new_mask);
8175 out_free_cpus_allowed:
8176 free_cpumask_var(cpus_allowed);
8177 return retval;
8178 }
8179
sched_setaffinity(pid_t pid,const struct cpumask * in_mask)8180 long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
8181 {
8182 struct task_struct *p;
8183 int retval;
8184
8185 rcu_read_lock();
8186
8187 p = find_process_by_pid(pid);
8188 if (!p) {
8189 rcu_read_unlock();
8190 return -ESRCH;
8191 }
8192
8193 /* Prevent p going away */
8194 get_task_struct(p);
8195 rcu_read_unlock();
8196
8197 if (p->flags & PF_NO_SETAFFINITY) {
8198 retval = -EINVAL;
8199 goto out_put_task;
8200 }
8201
8202 if (!check_same_owner(p)) {
8203 rcu_read_lock();
8204 if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
8205 rcu_read_unlock();
8206 retval = -EPERM;
8207 goto out_put_task;
8208 }
8209 rcu_read_unlock();
8210 }
8211
8212 retval = security_task_setscheduler(p);
8213 if (retval)
8214 goto out_put_task;
8215
8216 retval = __sched_setaffinity(p, in_mask);
8217 out_put_task:
8218 put_task_struct(p);
8219 return retval;
8220 }
8221
get_user_cpu_mask(unsigned long __user * user_mask_ptr,unsigned len,struct cpumask * new_mask)8222 static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
8223 struct cpumask *new_mask)
8224 {
8225 if (len < cpumask_size())
8226 cpumask_clear(new_mask);
8227 else if (len > cpumask_size())
8228 len = cpumask_size();
8229
8230 return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
8231 }
8232
8233 /**
8234 * sys_sched_setaffinity - set the CPU affinity of a process
8235 * @pid: pid of the process
8236 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
8237 * @user_mask_ptr: user-space pointer to the new CPU mask
8238 *
8239 * Return: 0 on success. An error code otherwise.
8240 */
SYSCALL_DEFINE3(sched_setaffinity,pid_t,pid,unsigned int,len,unsigned long __user *,user_mask_ptr)8241 SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
8242 unsigned long __user *, user_mask_ptr)
8243 {
8244 cpumask_var_t new_mask;
8245 int retval;
8246
8247 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
8248 return -ENOMEM;
8249
8250 retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
8251 if (retval == 0)
8252 retval = sched_setaffinity(pid, new_mask);
8253 free_cpumask_var(new_mask);
8254 return retval;
8255 }
8256
sched_getaffinity(pid_t pid,struct cpumask * mask)8257 long sched_getaffinity(pid_t pid, struct cpumask *mask)
8258 {
8259 struct task_struct *p;
8260 unsigned long flags;
8261 int retval;
8262
8263 rcu_read_lock();
8264
8265 retval = -ESRCH;
8266 p = find_process_by_pid(pid);
8267 if (!p)
8268 goto out_unlock;
8269
8270 retval = security_task_getscheduler(p);
8271 if (retval)
8272 goto out_unlock;
8273
8274 raw_spin_lock_irqsave(&p->pi_lock, flags);
8275 cpumask_and(mask, &p->cpus_mask, cpu_active_mask);
8276 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
8277
8278 out_unlock:
8279 rcu_read_unlock();
8280
8281 return retval;
8282 }
8283
8284 /**
8285 * sys_sched_getaffinity - get the CPU affinity of a process
8286 * @pid: pid of the process
8287 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
8288 * @user_mask_ptr: user-space pointer to hold the current CPU mask
8289 *
8290 * Return: size of CPU mask copied to user_mask_ptr on success. An
8291 * error code otherwise.
8292 */
SYSCALL_DEFINE3(sched_getaffinity,pid_t,pid,unsigned int,len,unsigned long __user *,user_mask_ptr)8293 SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
8294 unsigned long __user *, user_mask_ptr)
8295 {
8296 int ret;
8297 cpumask_var_t mask;
8298
8299 if ((len * BITS_PER_BYTE) < nr_cpu_ids)
8300 return -EINVAL;
8301 if (len & (sizeof(unsigned long)-1))
8302 return -EINVAL;
8303
8304 if (!alloc_cpumask_var(&mask, GFP_KERNEL))
8305 return -ENOMEM;
8306
8307 ret = sched_getaffinity(pid, mask);
8308 if (ret == 0) {
8309 unsigned int retlen = min(len, cpumask_size());
8310
8311 if (copy_to_user(user_mask_ptr, mask, retlen))
8312 ret = -EFAULT;
8313 else
8314 ret = retlen;
8315 }
8316 free_cpumask_var(mask);
8317
8318 return ret;
8319 }
8320
do_sched_yield(void)8321 static void do_sched_yield(void)
8322 {
8323 struct rq_flags rf;
8324 struct rq *rq;
8325
8326 rq = this_rq_lock_irq(&rf);
8327
8328 schedstat_inc(rq->yld_count);
8329 current->sched_class->yield_task(rq);
8330
8331 preempt_disable();
8332 rq_unlock_irq(rq, &rf);
8333 sched_preempt_enable_no_resched();
8334
8335 schedule();
8336 }
8337
8338 /**
8339 * sys_sched_yield - yield the current processor to other threads.
8340 *
8341 * This function yields the current CPU to other tasks. If there are no
8342 * other threads running on this CPU then this function will return.
8343 *
8344 * Return: 0.
8345 */
SYSCALL_DEFINE0(sched_yield)8346 SYSCALL_DEFINE0(sched_yield)
8347 {
8348 do_sched_yield();
8349 return 0;
8350 }
8351
8352 #if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC)
__cond_resched(void)8353 int __sched __cond_resched(void)
8354 {
8355 if (should_resched(0)) {
8356 preempt_schedule_common();
8357 return 1;
8358 }
8359 /*
8360 * In preemptible kernels, ->rcu_read_lock_nesting tells the tick
8361 * whether the current CPU is in an RCU read-side critical section,
8362 * so the tick can report quiescent states even for CPUs looping
8363 * in kernel context. In contrast, in non-preemptible kernels,
8364 * RCU readers leave no in-memory hints, which means that CPU-bound
8365 * processes executing in kernel context might never report an
8366 * RCU quiescent state. Therefore, the following code causes
8367 * cond_resched() to report a quiescent state, but only when RCU
8368 * is in urgent need of one.
8369 */
8370 #ifndef CONFIG_PREEMPT_RCU
8371 rcu_all_qs();
8372 #endif
8373 return 0;
8374 }
8375 EXPORT_SYMBOL(__cond_resched);
8376 #endif
8377
8378 #ifdef CONFIG_PREEMPT_DYNAMIC
8379 #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
8380 #define cond_resched_dynamic_enabled __cond_resched
8381 #define cond_resched_dynamic_disabled ((void *)&__static_call_return0)
8382 DEFINE_STATIC_CALL_RET0(cond_resched, __cond_resched);
8383 EXPORT_STATIC_CALL_TRAMP(cond_resched);
8384
8385 #define might_resched_dynamic_enabled __cond_resched
8386 #define might_resched_dynamic_disabled ((void *)&__static_call_return0)
8387 DEFINE_STATIC_CALL_RET0(might_resched, __cond_resched);
8388 EXPORT_STATIC_CALL_TRAMP(might_resched);
8389 #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
8390 static DEFINE_STATIC_KEY_FALSE(sk_dynamic_cond_resched);
dynamic_cond_resched(void)8391 int __sched dynamic_cond_resched(void)
8392 {
8393 if (!static_branch_unlikely(&sk_dynamic_cond_resched))
8394 return 0;
8395 return __cond_resched();
8396 }
8397 EXPORT_SYMBOL(dynamic_cond_resched);
8398
8399 static DEFINE_STATIC_KEY_FALSE(sk_dynamic_might_resched);
dynamic_might_resched(void)8400 int __sched dynamic_might_resched(void)
8401 {
8402 if (!static_branch_unlikely(&sk_dynamic_might_resched))
8403 return 0;
8404 return __cond_resched();
8405 }
8406 EXPORT_SYMBOL(dynamic_might_resched);
8407 #endif
8408 #endif
8409
8410 /*
8411 * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
8412 * call schedule, and on return reacquire the lock.
8413 *
8414 * This works OK both with and without CONFIG_PREEMPTION. We do strange low-level
8415 * operations here to prevent schedule() from being called twice (once via
8416 * spin_unlock(), once by hand).
8417 */
__cond_resched_lock(spinlock_t * lock)8418 int __cond_resched_lock(spinlock_t *lock)
8419 {
8420 int resched = should_resched(PREEMPT_LOCK_OFFSET);
8421 int ret = 0;
8422
8423 lockdep_assert_held(lock);
8424
8425 if (spin_needbreak(lock) || resched) {
8426 spin_unlock(lock);
8427 if (!_cond_resched())
8428 cpu_relax();
8429 ret = 1;
8430 spin_lock(lock);
8431 }
8432 return ret;
8433 }
8434 EXPORT_SYMBOL(__cond_resched_lock);
8435
__cond_resched_rwlock_read(rwlock_t * lock)8436 int __cond_resched_rwlock_read(rwlock_t *lock)
8437 {
8438 int resched = should_resched(PREEMPT_LOCK_OFFSET);
8439 int ret = 0;
8440
8441 lockdep_assert_held_read(lock);
8442
8443 if (rwlock_needbreak(lock) || resched) {
8444 read_unlock(lock);
8445 if (!_cond_resched())
8446 cpu_relax();
8447 ret = 1;
8448 read_lock(lock);
8449 }
8450 return ret;
8451 }
8452 EXPORT_SYMBOL(__cond_resched_rwlock_read);
8453
__cond_resched_rwlock_write(rwlock_t * lock)8454 int __cond_resched_rwlock_write(rwlock_t *lock)
8455 {
8456 int resched = should_resched(PREEMPT_LOCK_OFFSET);
8457 int ret = 0;
8458
8459 lockdep_assert_held_write(lock);
8460
8461 if (rwlock_needbreak(lock) || resched) {
8462 write_unlock(lock);
8463 if (!_cond_resched())
8464 cpu_relax();
8465 ret = 1;
8466 write_lock(lock);
8467 }
8468 return ret;
8469 }
8470 EXPORT_SYMBOL(__cond_resched_rwlock_write);
8471
8472 #ifdef CONFIG_PREEMPT_DYNAMIC
8473
8474 #ifdef CONFIG_GENERIC_ENTRY
8475 #include <linux/entry-common.h>
8476 #endif
8477
8478 /*
8479 * SC:cond_resched
8480 * SC:might_resched
8481 * SC:preempt_schedule
8482 * SC:preempt_schedule_notrace
8483 * SC:irqentry_exit_cond_resched
8484 *
8485 *
8486 * NONE:
8487 * cond_resched <- __cond_resched
8488 * might_resched <- RET0
8489 * preempt_schedule <- NOP
8490 * preempt_schedule_notrace <- NOP
8491 * irqentry_exit_cond_resched <- NOP
8492 *
8493 * VOLUNTARY:
8494 * cond_resched <- __cond_resched
8495 * might_resched <- __cond_resched
8496 * preempt_schedule <- NOP
8497 * preempt_schedule_notrace <- NOP
8498 * irqentry_exit_cond_resched <- NOP
8499 *
8500 * FULL:
8501 * cond_resched <- RET0
8502 * might_resched <- RET0
8503 * preempt_schedule <- preempt_schedule
8504 * preempt_schedule_notrace <- preempt_schedule_notrace
8505 * irqentry_exit_cond_resched <- irqentry_exit_cond_resched
8506 */
8507
8508 enum {
8509 preempt_dynamic_undefined = -1,
8510 preempt_dynamic_none,
8511 preempt_dynamic_voluntary,
8512 preempt_dynamic_full,
8513 };
8514
8515 int preempt_dynamic_mode = preempt_dynamic_undefined;
8516
sched_dynamic_mode(const char * str)8517 int sched_dynamic_mode(const char *str)
8518 {
8519 if (!strcmp(str, "none"))
8520 return preempt_dynamic_none;
8521
8522 if (!strcmp(str, "voluntary"))
8523 return preempt_dynamic_voluntary;
8524
8525 if (!strcmp(str, "full"))
8526 return preempt_dynamic_full;
8527
8528 return -EINVAL;
8529 }
8530
8531 #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
8532 #define preempt_dynamic_enable(f) static_call_update(f, f##_dynamic_enabled)
8533 #define preempt_dynamic_disable(f) static_call_update(f, f##_dynamic_disabled)
8534 #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
8535 #define preempt_dynamic_enable(f) static_key_enable(&sk_dynamic_##f.key)
8536 #define preempt_dynamic_disable(f) static_key_disable(&sk_dynamic_##f.key)
8537 #else
8538 #error "Unsupported PREEMPT_DYNAMIC mechanism"
8539 #endif
8540
sched_dynamic_update(int mode)8541 void sched_dynamic_update(int mode)
8542 {
8543 /*
8544 * Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in
8545 * the ZERO state, which is invalid.
8546 */
8547 preempt_dynamic_enable(cond_resched);
8548 preempt_dynamic_enable(might_resched);
8549 preempt_dynamic_enable(preempt_schedule);
8550 preempt_dynamic_enable(preempt_schedule_notrace);
8551 preempt_dynamic_enable(irqentry_exit_cond_resched);
8552
8553 switch (mode) {
8554 case preempt_dynamic_none:
8555 preempt_dynamic_enable(cond_resched);
8556 preempt_dynamic_disable(might_resched);
8557 preempt_dynamic_disable(preempt_schedule);
8558 preempt_dynamic_disable(preempt_schedule_notrace);
8559 preempt_dynamic_disable(irqentry_exit_cond_resched);
8560 pr_info("Dynamic Preempt: none\n");
8561 break;
8562
8563 case preempt_dynamic_voluntary:
8564 preempt_dynamic_enable(cond_resched);
8565 preempt_dynamic_enable(might_resched);
8566 preempt_dynamic_disable(preempt_schedule);
8567 preempt_dynamic_disable(preempt_schedule_notrace);
8568 preempt_dynamic_disable(irqentry_exit_cond_resched);
8569 pr_info("Dynamic Preempt: voluntary\n");
8570 break;
8571
8572 case preempt_dynamic_full:
8573 preempt_dynamic_disable(cond_resched);
8574 preempt_dynamic_disable(might_resched);
8575 preempt_dynamic_enable(preempt_schedule);
8576 preempt_dynamic_enable(preempt_schedule_notrace);
8577 preempt_dynamic_enable(irqentry_exit_cond_resched);
8578 pr_info("Dynamic Preempt: full\n");
8579 break;
8580 }
8581
8582 preempt_dynamic_mode = mode;
8583 }
8584
setup_preempt_mode(char * str)8585 static int __init setup_preempt_mode(char *str)
8586 {
8587 int mode = sched_dynamic_mode(str);
8588 if (mode < 0) {
8589 pr_warn("Dynamic Preempt: unsupported mode: %s\n", str);
8590 return 0;
8591 }
8592
8593 sched_dynamic_update(mode);
8594 return 1;
8595 }
8596 __setup("preempt=", setup_preempt_mode);
8597
preempt_dynamic_init(void)8598 static void __init preempt_dynamic_init(void)
8599 {
8600 if (preempt_dynamic_mode == preempt_dynamic_undefined) {
8601 if (IS_ENABLED(CONFIG_PREEMPT_NONE)) {
8602 sched_dynamic_update(preempt_dynamic_none);
8603 } else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)) {
8604 sched_dynamic_update(preempt_dynamic_voluntary);
8605 } else {
8606 /* Default static call setting, nothing to do */
8607 WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT));
8608 preempt_dynamic_mode = preempt_dynamic_full;
8609 pr_info("Dynamic Preempt: full\n");
8610 }
8611 }
8612 }
8613
8614 #define PREEMPT_MODEL_ACCESSOR(mode) \
8615 bool preempt_model_##mode(void) \
8616 { \
8617 WARN_ON_ONCE(preempt_dynamic_mode == preempt_dynamic_undefined); \
8618 return preempt_dynamic_mode == preempt_dynamic_##mode; \
8619 } \
8620 EXPORT_SYMBOL_GPL(preempt_model_##mode)
8621
8622 PREEMPT_MODEL_ACCESSOR(none);
8623 PREEMPT_MODEL_ACCESSOR(voluntary);
8624 PREEMPT_MODEL_ACCESSOR(full);
8625
8626 #else /* !CONFIG_PREEMPT_DYNAMIC */
8627
preempt_dynamic_init(void)8628 static inline void preempt_dynamic_init(void) { }
8629
8630 #endif /* #ifdef CONFIG_PREEMPT_DYNAMIC */
8631
8632 /**
8633 * yield - yield the current processor to other threads.
8634 *
8635 * Do not ever use this function, there's a 99% chance you're doing it wrong.
8636 *
8637 * The scheduler is at all times free to pick the calling task as the most
8638 * eligible task to run, if removing the yield() call from your code breaks
8639 * it, it's already broken.
8640 *
8641 * Typical broken usage is:
8642 *
8643 * while (!event)
8644 * yield();
8645 *
8646 * where one assumes that yield() will let 'the other' process run that will
8647 * make event true. If the current task is a SCHED_FIFO task that will never
8648 * happen. Never use yield() as a progress guarantee!!
8649 *
8650 * If you want to use yield() to wait for something, use wait_event().
8651 * If you want to use yield() to be 'nice' for others, use cond_resched().
8652 * If you still want to use yield(), do not!
8653 */
yield(void)8654 void __sched yield(void)
8655 {
8656 set_current_state(TASK_RUNNING);
8657 do_sched_yield();
8658 }
8659 EXPORT_SYMBOL(yield);
8660
8661 /**
8662 * yield_to - yield the current processor to another thread in
8663 * your thread group, or accelerate that thread toward the
8664 * processor it's on.
8665 * @p: target task
8666 * @preempt: whether task preemption is allowed or not
8667 *
8668 * It's the caller's job to ensure that the target task struct
8669 * can't go away on us before we can do any checks.
8670 *
8671 * Return:
8672 * true (>0) if we indeed boosted the target task.
8673 * false (0) if we failed to boost the target.
8674 * -ESRCH if there's no task to yield to.
8675 */
yield_to(struct task_struct * p,bool preempt)8676 int __sched yield_to(struct task_struct *p, bool preempt)
8677 {
8678 struct task_struct *curr = current;
8679 struct rq *rq, *p_rq;
8680 unsigned long flags;
8681 int yielded = 0;
8682
8683 local_irq_save(flags);
8684 rq = this_rq();
8685
8686 again:
8687 p_rq = task_rq(p);
8688 /*
8689 * If we're the only runnable task on the rq and target rq also
8690 * has only one task, there's absolutely no point in yielding.
8691 */
8692 if (rq->nr_running == 1 && p_rq->nr_running == 1) {
8693 yielded = -ESRCH;
8694 goto out_irq;
8695 }
8696
8697 double_rq_lock(rq, p_rq);
8698 if (task_rq(p) != p_rq) {
8699 double_rq_unlock(rq, p_rq);
8700 goto again;
8701 }
8702
8703 if (!curr->sched_class->yield_to_task)
8704 goto out_unlock;
8705
8706 if (curr->sched_class != p->sched_class)
8707 goto out_unlock;
8708
8709 if (task_on_cpu(p_rq, p) || !task_is_running(p))
8710 goto out_unlock;
8711
8712 yielded = curr->sched_class->yield_to_task(rq, p);
8713 if (yielded) {
8714 schedstat_inc(rq->yld_count);
8715 /*
8716 * Make p's CPU reschedule; pick_next_entity takes care of
8717 * fairness.
8718 */
8719 if (preempt && rq != p_rq)
8720 resched_curr(p_rq);
8721 }
8722
8723 out_unlock:
8724 double_rq_unlock(rq, p_rq);
8725 out_irq:
8726 local_irq_restore(flags);
8727
8728 if (yielded > 0)
8729 schedule();
8730
8731 return yielded;
8732 }
8733 EXPORT_SYMBOL_GPL(yield_to);
8734
io_schedule_prepare(void)8735 int io_schedule_prepare(void)
8736 {
8737 int old_iowait = current->in_iowait;
8738
8739 current->in_iowait = 1;
8740 blk_flush_plug(current->plug, true);
8741 return old_iowait;
8742 }
8743
io_schedule_finish(int token)8744 void io_schedule_finish(int token)
8745 {
8746 current->in_iowait = token;
8747 }
8748
8749 /*
8750 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
8751 * that process accounting knows that this is a task in IO wait state.
8752 */
io_schedule_timeout(long timeout)8753 long __sched io_schedule_timeout(long timeout)
8754 {
8755 int token;
8756 long ret;
8757
8758 token = io_schedule_prepare();
8759 ret = schedule_timeout(timeout);
8760 io_schedule_finish(token);
8761
8762 return ret;
8763 }
8764 EXPORT_SYMBOL(io_schedule_timeout);
8765
io_schedule(void)8766 void __sched io_schedule(void)
8767 {
8768 int token;
8769
8770 token = io_schedule_prepare();
8771 schedule();
8772 io_schedule_finish(token);
8773 }
8774 EXPORT_SYMBOL(io_schedule);
8775
8776 /**
8777 * sys_sched_get_priority_max - return maximum RT priority.
8778 * @policy: scheduling class.
8779 *
8780 * Return: On success, this syscall returns the maximum
8781 * rt_priority that can be used by a given scheduling class.
8782 * On failure, a negative error code is returned.
8783 */
SYSCALL_DEFINE1(sched_get_priority_max,int,policy)8784 SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
8785 {
8786 int ret = -EINVAL;
8787
8788 switch (policy) {
8789 case SCHED_FIFO:
8790 case SCHED_RR:
8791 ret = MAX_RT_PRIO-1;
8792 break;
8793 case SCHED_DEADLINE:
8794 case SCHED_NORMAL:
8795 case SCHED_BATCH:
8796 case SCHED_IDLE:
8797 ret = 0;
8798 break;
8799 }
8800 return ret;
8801 }
8802
8803 /**
8804 * sys_sched_get_priority_min - return minimum RT priority.
8805 * @policy: scheduling class.
8806 *
8807 * Return: On success, this syscall returns the minimum
8808 * rt_priority that can be used by a given scheduling class.
8809 * On failure, a negative error code is returned.
8810 */
SYSCALL_DEFINE1(sched_get_priority_min,int,policy)8811 SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
8812 {
8813 int ret = -EINVAL;
8814
8815 switch (policy) {
8816 case SCHED_FIFO:
8817 case SCHED_RR:
8818 ret = 1;
8819 break;
8820 case SCHED_DEADLINE:
8821 case SCHED_NORMAL:
8822 case SCHED_BATCH:
8823 case SCHED_IDLE:
8824 ret = 0;
8825 }
8826 return ret;
8827 }
8828
sched_rr_get_interval(pid_t pid,struct timespec64 * t)8829 static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
8830 {
8831 struct task_struct *p;
8832 unsigned int time_slice;
8833 struct rq_flags rf;
8834 struct rq *rq;
8835 int retval;
8836
8837 if (pid < 0)
8838 return -EINVAL;
8839
8840 retval = -ESRCH;
8841 rcu_read_lock();
8842 p = find_process_by_pid(pid);
8843 if (!p)
8844 goto out_unlock;
8845
8846 retval = security_task_getscheduler(p);
8847 if (retval)
8848 goto out_unlock;
8849
8850 rq = task_rq_lock(p, &rf);
8851 time_slice = 0;
8852 if (p->sched_class->get_rr_interval)
8853 time_slice = p->sched_class->get_rr_interval(rq, p);
8854 task_rq_unlock(rq, p, &rf);
8855
8856 rcu_read_unlock();
8857 jiffies_to_timespec64(time_slice, t);
8858 return 0;
8859
8860 out_unlock:
8861 rcu_read_unlock();
8862 return retval;
8863 }
8864
8865 /**
8866 * sys_sched_rr_get_interval - return the default timeslice of a process.
8867 * @pid: pid of the process.
8868 * @interval: userspace pointer to the timeslice value.
8869 *
8870 * this syscall writes the default timeslice value of a given process
8871 * into the user-space timespec buffer. A value of '0' means infinity.
8872 *
8873 * Return: On success, 0 and the timeslice is in @interval. Otherwise,
8874 * an error code.
8875 */
SYSCALL_DEFINE2(sched_rr_get_interval,pid_t,pid,struct __kernel_timespec __user *,interval)8876 SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
8877 struct __kernel_timespec __user *, interval)
8878 {
8879 struct timespec64 t;
8880 int retval = sched_rr_get_interval(pid, &t);
8881
8882 if (retval == 0)
8883 retval = put_timespec64(&t, interval);
8884
8885 return retval;
8886 }
8887
8888 #ifdef CONFIG_COMPAT_32BIT_TIME
SYSCALL_DEFINE2(sched_rr_get_interval_time32,pid_t,pid,struct old_timespec32 __user *,interval)8889 SYSCALL_DEFINE2(sched_rr_get_interval_time32, pid_t, pid,
8890 struct old_timespec32 __user *, interval)
8891 {
8892 struct timespec64 t;
8893 int retval = sched_rr_get_interval(pid, &t);
8894
8895 if (retval == 0)
8896 retval = put_old_timespec32(&t, interval);
8897 return retval;
8898 }
8899 #endif
8900
sched_show_task(struct task_struct * p)8901 void sched_show_task(struct task_struct *p)
8902 {
8903 unsigned long free = 0;
8904 int ppid;
8905
8906 if (!try_get_task_stack(p))
8907 return;
8908
8909 pr_info("task:%-15.15s state:%c", p->comm, task_state_to_char(p));
8910
8911 if (task_is_running(p))
8912 pr_cont(" running task ");
8913 #ifdef CONFIG_DEBUG_STACK_USAGE
8914 free = stack_not_used(p);
8915 #endif
8916 ppid = 0;
8917 rcu_read_lock();
8918 if (pid_alive(p))
8919 ppid = task_pid_nr(rcu_dereference(p->real_parent));
8920 rcu_read_unlock();
8921 pr_cont(" stack:%-5lu pid:%-5d ppid:%-6d flags:0x%08lx\n",
8922 free, task_pid_nr(p), ppid,
8923 read_task_thread_flags(p));
8924
8925 print_worker_info(KERN_INFO, p);
8926 print_stop_info(KERN_INFO, p);
8927 show_stack(p, NULL, KERN_INFO);
8928 put_task_stack(p);
8929 }
8930 EXPORT_SYMBOL_GPL(sched_show_task);
8931
8932 static inline bool
state_filter_match(unsigned long state_filter,struct task_struct * p)8933 state_filter_match(unsigned long state_filter, struct task_struct *p)
8934 {
8935 unsigned int state = READ_ONCE(p->__state);
8936
8937 /* no filter, everything matches */
8938 if (!state_filter)
8939 return true;
8940
8941 /* filter, but doesn't match */
8942 if (!(state & state_filter))
8943 return false;
8944
8945 /*
8946 * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
8947 * TASK_KILLABLE).
8948 */
8949 if (state_filter == TASK_UNINTERRUPTIBLE && (state & TASK_NOLOAD))
8950 return false;
8951
8952 return true;
8953 }
8954
8955
show_state_filter(unsigned int state_filter)8956 void show_state_filter(unsigned int state_filter)
8957 {
8958 struct task_struct *g, *p;
8959
8960 rcu_read_lock();
8961 for_each_process_thread(g, p) {
8962 /*
8963 * reset the NMI-timeout, listing all files on a slow
8964 * console might take a lot of time:
8965 * Also, reset softlockup watchdogs on all CPUs, because
8966 * another CPU might be blocked waiting for us to process
8967 * an IPI.
8968 */
8969 touch_nmi_watchdog();
8970 touch_all_softlockup_watchdogs();
8971 if (state_filter_match(state_filter, p))
8972 sched_show_task(p);
8973 }
8974
8975 #ifdef CONFIG_SCHED_DEBUG
8976 if (!state_filter)
8977 sysrq_sched_debug_show();
8978 #endif
8979 rcu_read_unlock();
8980 /*
8981 * Only show locks if all tasks are dumped:
8982 */
8983 if (!state_filter)
8984 debug_show_all_locks();
8985 }
8986
8987 /**
8988 * init_idle - set up an idle thread for a given CPU
8989 * @idle: task in question
8990 * @cpu: CPU the idle task belongs to
8991 *
8992 * NOTE: this function does not set the idle thread's NEED_RESCHED
8993 * flag, to make booting more robust.
8994 */
init_idle(struct task_struct * idle,int cpu)8995 void __init init_idle(struct task_struct *idle, int cpu)
8996 {
8997 struct rq *rq = cpu_rq(cpu);
8998 unsigned long flags;
8999
9000 __sched_fork(0, idle);
9001
9002 raw_spin_lock_irqsave(&idle->pi_lock, flags);
9003 raw_spin_rq_lock(rq);
9004
9005 idle->__state = TASK_RUNNING;
9006 idle->se.exec_start = sched_clock();
9007 /*
9008 * PF_KTHREAD should already be set at this point; regardless, make it
9009 * look like a proper per-CPU kthread.
9010 */
9011 idle->flags |= PF_IDLE | PF_KTHREAD | PF_NO_SETAFFINITY;
9012 kthread_set_per_cpu(idle, cpu);
9013
9014 #ifdef CONFIG_SMP
9015 /*
9016 * It's possible that init_idle() gets called multiple times on a task,
9017 * in that case do_set_cpus_allowed() will not do the right thing.
9018 *
9019 * And since this is boot we can forgo the serialization.
9020 */
9021 set_cpus_allowed_common(idle, cpumask_of(cpu), 0);
9022 #endif
9023 /*
9024 * We're having a chicken and egg problem, even though we are
9025 * holding rq->lock, the CPU isn't yet set to this CPU so the
9026 * lockdep check in task_group() will fail.
9027 *
9028 * Similar case to sched_fork(). / Alternatively we could
9029 * use task_rq_lock() here and obtain the other rq->lock.
9030 *
9031 * Silence PROVE_RCU
9032 */
9033 rcu_read_lock();
9034 __set_task_cpu(idle, cpu);
9035 rcu_read_unlock();
9036
9037 rq->idle = idle;
9038 rcu_assign_pointer(rq->curr, idle);
9039 idle->on_rq = TASK_ON_RQ_QUEUED;
9040 #ifdef CONFIG_SMP
9041 idle->on_cpu = 1;
9042 #endif
9043 raw_spin_rq_unlock(rq);
9044 raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
9045
9046 /* Set the preempt count _outside_ the spinlocks! */
9047 init_idle_preempt_count(idle, cpu);
9048
9049 /*
9050 * The idle tasks have their own, simple scheduling class:
9051 */
9052 idle->sched_class = &idle_sched_class;
9053 ftrace_graph_init_idle_task(idle, cpu);
9054 vtime_init_idle(idle, cpu);
9055 #ifdef CONFIG_SMP
9056 sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
9057 #endif
9058 }
9059
9060 #ifdef CONFIG_SMP
9061
cpuset_cpumask_can_shrink(const struct cpumask * cur,const struct cpumask * trial)9062 int cpuset_cpumask_can_shrink(const struct cpumask *cur,
9063 const struct cpumask *trial)
9064 {
9065 int ret = 1;
9066
9067 if (cpumask_empty(cur))
9068 return ret;
9069
9070 ret = dl_cpuset_cpumask_can_shrink(cur, trial);
9071
9072 return ret;
9073 }
9074
task_can_attach(struct task_struct * p,const struct cpumask * cs_effective_cpus)9075 int task_can_attach(struct task_struct *p,
9076 const struct cpumask *cs_effective_cpus)
9077 {
9078 int ret = 0;
9079
9080 /*
9081 * Kthreads which disallow setaffinity shouldn't be moved
9082 * to a new cpuset; we don't want to change their CPU
9083 * affinity and isolating such threads by their set of
9084 * allowed nodes is unnecessary. Thus, cpusets are not
9085 * applicable for such threads. This prevents checking for
9086 * success of set_cpus_allowed_ptr() on all attached tasks
9087 * before cpus_mask may be changed.
9088 */
9089 if (p->flags & PF_NO_SETAFFINITY) {
9090 ret = -EINVAL;
9091 goto out;
9092 }
9093
9094 if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
9095 cs_effective_cpus)) {
9096 int cpu = cpumask_any_and(cpu_active_mask, cs_effective_cpus);
9097
9098 if (unlikely(cpu >= nr_cpu_ids))
9099 return -EINVAL;
9100 ret = dl_cpu_busy(cpu, p);
9101 }
9102
9103 out:
9104 return ret;
9105 }
9106
9107 bool sched_smp_initialized __read_mostly;
9108
9109 #ifdef CONFIG_NUMA_BALANCING
9110 /* Migrate current task p to target_cpu */
migrate_task_to(struct task_struct * p,int target_cpu)9111 int migrate_task_to(struct task_struct *p, int target_cpu)
9112 {
9113 struct migration_arg arg = { p, target_cpu };
9114 int curr_cpu = task_cpu(p);
9115
9116 if (curr_cpu == target_cpu)
9117 return 0;
9118
9119 if (!cpumask_test_cpu(target_cpu, p->cpus_ptr))
9120 return -EINVAL;
9121
9122 /* TODO: This is not properly updating schedstats */
9123
9124 trace_sched_move_numa(p, curr_cpu, target_cpu);
9125 return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
9126 }
9127
9128 /*
9129 * Requeue a task on a given node and accurately track the number of NUMA
9130 * tasks on the runqueues
9131 */
sched_setnuma(struct task_struct * p,int nid)9132 void sched_setnuma(struct task_struct *p, int nid)
9133 {
9134 bool queued, running;
9135 struct rq_flags rf;
9136 struct rq *rq;
9137
9138 rq = task_rq_lock(p, &rf);
9139 queued = task_on_rq_queued(p);
9140 running = task_current(rq, p);
9141
9142 if (queued)
9143 dequeue_task(rq, p, DEQUEUE_SAVE);
9144 if (running)
9145 put_prev_task(rq, p);
9146
9147 p->numa_preferred_nid = nid;
9148
9149 if (queued)
9150 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
9151 if (running)
9152 set_next_task(rq, p);
9153 task_rq_unlock(rq, p, &rf);
9154 }
9155 #endif /* CONFIG_NUMA_BALANCING */
9156
9157 #ifdef CONFIG_HOTPLUG_CPU
9158 /*
9159 * Ensure that the idle task is using init_mm right before its CPU goes
9160 * offline.
9161 */
idle_task_exit(void)9162 void idle_task_exit(void)
9163 {
9164 struct mm_struct *mm = current->active_mm;
9165
9166 BUG_ON(cpu_online(smp_processor_id()));
9167 BUG_ON(current != this_rq()->idle);
9168
9169 if (mm != &init_mm) {
9170 switch_mm(mm, &init_mm, current);
9171 finish_arch_post_lock_switch();
9172 }
9173
9174 /* finish_cpu(), as ran on the BP, will clean up the active_mm state */
9175 }
9176
__balance_push_cpu_stop(void * arg)9177 static int __balance_push_cpu_stop(void *arg)
9178 {
9179 struct task_struct *p = arg;
9180 struct rq *rq = this_rq();
9181 struct rq_flags rf;
9182 int cpu;
9183
9184 raw_spin_lock_irq(&p->pi_lock);
9185 rq_lock(rq, &rf);
9186
9187 update_rq_clock(rq);
9188
9189 if (task_rq(p) == rq && task_on_rq_queued(p)) {
9190 cpu = select_fallback_rq(rq->cpu, p);
9191 rq = __migrate_task(rq, &rf, p, cpu);
9192 }
9193
9194 rq_unlock(rq, &rf);
9195 raw_spin_unlock_irq(&p->pi_lock);
9196
9197 put_task_struct(p);
9198
9199 return 0;
9200 }
9201
9202 static DEFINE_PER_CPU(struct cpu_stop_work, push_work);
9203
9204 /*
9205 * Ensure we only run per-cpu kthreads once the CPU goes !active.
9206 *
9207 * This is enabled below SCHED_AP_ACTIVE; when !cpu_active(), but only
9208 * effective when the hotplug motion is down.
9209 */
balance_push(struct rq * rq)9210 static void balance_push(struct rq *rq)
9211 {
9212 struct task_struct *push_task = rq->curr;
9213
9214 lockdep_assert_rq_held(rq);
9215
9216 /*
9217 * Ensure the thing is persistent until balance_push_set(.on = false);
9218 */
9219 rq->balance_callback = &balance_push_callback;
9220
9221 /*
9222 * Only active while going offline and when invoked on the outgoing
9223 * CPU.
9224 */
9225 if (!cpu_dying(rq->cpu) || rq != this_rq())
9226 return;
9227
9228 /*
9229 * Both the cpu-hotplug and stop task are in this case and are
9230 * required to complete the hotplug process.
9231 */
9232 if (kthread_is_per_cpu(push_task) ||
9233 is_migration_disabled(push_task)) {
9234
9235 /*
9236 * If this is the idle task on the outgoing CPU try to wake
9237 * up the hotplug control thread which might wait for the
9238 * last task to vanish. The rcuwait_active() check is
9239 * accurate here because the waiter is pinned on this CPU
9240 * and can't obviously be running in parallel.
9241 *
9242 * On RT kernels this also has to check whether there are
9243 * pinned and scheduled out tasks on the runqueue. They
9244 * need to leave the migrate disabled section first.
9245 */
9246 if (!rq->nr_running && !rq_has_pinned_tasks(rq) &&
9247 rcuwait_active(&rq->hotplug_wait)) {
9248 raw_spin_rq_unlock(rq);
9249 rcuwait_wake_up(&rq->hotplug_wait);
9250 raw_spin_rq_lock(rq);
9251 }
9252 return;
9253 }
9254
9255 get_task_struct(push_task);
9256 /*
9257 * Temporarily drop rq->lock such that we can wake-up the stop task.
9258 * Both preemption and IRQs are still disabled.
9259 */
9260 raw_spin_rq_unlock(rq);
9261 stop_one_cpu_nowait(rq->cpu, __balance_push_cpu_stop, push_task,
9262 this_cpu_ptr(&push_work));
9263 /*
9264 * At this point need_resched() is true and we'll take the loop in
9265 * schedule(). The next pick is obviously going to be the stop task
9266 * which kthread_is_per_cpu() and will push this task away.
9267 */
9268 raw_spin_rq_lock(rq);
9269 }
9270
balance_push_set(int cpu,bool on)9271 static void balance_push_set(int cpu, bool on)
9272 {
9273 struct rq *rq = cpu_rq(cpu);
9274 struct rq_flags rf;
9275
9276 rq_lock_irqsave(rq, &rf);
9277 if (on) {
9278 WARN_ON_ONCE(rq->balance_callback);
9279 rq->balance_callback = &balance_push_callback;
9280 } else if (rq->balance_callback == &balance_push_callback) {
9281 rq->balance_callback = NULL;
9282 }
9283 rq_unlock_irqrestore(rq, &rf);
9284 }
9285
9286 /*
9287 * Invoked from a CPUs hotplug control thread after the CPU has been marked
9288 * inactive. All tasks which are not per CPU kernel threads are either
9289 * pushed off this CPU now via balance_push() or placed on a different CPU
9290 * during wakeup. Wait until the CPU is quiescent.
9291 */
balance_hotplug_wait(void)9292 static void balance_hotplug_wait(void)
9293 {
9294 struct rq *rq = this_rq();
9295
9296 rcuwait_wait_event(&rq->hotplug_wait,
9297 rq->nr_running == 1 && !rq_has_pinned_tasks(rq),
9298 TASK_UNINTERRUPTIBLE);
9299 }
9300
9301 #else
9302
balance_push(struct rq * rq)9303 static inline void balance_push(struct rq *rq)
9304 {
9305 }
9306
balance_push_set(int cpu,bool on)9307 static inline void balance_push_set(int cpu, bool on)
9308 {
9309 }
9310
balance_hotplug_wait(void)9311 static inline void balance_hotplug_wait(void)
9312 {
9313 }
9314
9315 #endif /* CONFIG_HOTPLUG_CPU */
9316
set_rq_online(struct rq * rq)9317 void set_rq_online(struct rq *rq)
9318 {
9319 if (!rq->online) {
9320 const struct sched_class *class;
9321
9322 cpumask_set_cpu(rq->cpu, rq->rd->online);
9323 rq->online = 1;
9324
9325 for_each_class(class) {
9326 if (class->rq_online)
9327 class->rq_online(rq);
9328 }
9329 }
9330 }
9331
set_rq_offline(struct rq * rq)9332 void set_rq_offline(struct rq *rq)
9333 {
9334 if (rq->online) {
9335 const struct sched_class *class;
9336
9337 for_each_class(class) {
9338 if (class->rq_offline)
9339 class->rq_offline(rq);
9340 }
9341
9342 cpumask_clear_cpu(rq->cpu, rq->rd->online);
9343 rq->online = 0;
9344 }
9345 }
9346
9347 /*
9348 * used to mark begin/end of suspend/resume:
9349 */
9350 static int num_cpus_frozen;
9351
9352 /*
9353 * Update cpusets according to cpu_active mask. If cpusets are
9354 * disabled, cpuset_update_active_cpus() becomes a simple wrapper
9355 * around partition_sched_domains().
9356 *
9357 * If we come here as part of a suspend/resume, don't touch cpusets because we
9358 * want to restore it back to its original state upon resume anyway.
9359 */
cpuset_cpu_active(void)9360 static void cpuset_cpu_active(void)
9361 {
9362 if (cpuhp_tasks_frozen) {
9363 /*
9364 * num_cpus_frozen tracks how many CPUs are involved in suspend
9365 * resume sequence. As long as this is not the last online
9366 * operation in the resume sequence, just build a single sched
9367 * domain, ignoring cpusets.
9368 */
9369 partition_sched_domains(1, NULL, NULL);
9370 if (--num_cpus_frozen)
9371 return;
9372 /*
9373 * This is the last CPU online operation. So fall through and
9374 * restore the original sched domains by considering the
9375 * cpuset configurations.
9376 */
9377 cpuset_force_rebuild();
9378 }
9379 cpuset_update_active_cpus();
9380 }
9381
cpuset_cpu_inactive(unsigned int cpu)9382 static int cpuset_cpu_inactive(unsigned int cpu)
9383 {
9384 if (!cpuhp_tasks_frozen) {
9385 int ret = dl_cpu_busy(cpu, NULL);
9386
9387 if (ret)
9388 return ret;
9389 cpuset_update_active_cpus();
9390 } else {
9391 num_cpus_frozen++;
9392 partition_sched_domains(1, NULL, NULL);
9393 }
9394 return 0;
9395 }
9396
sched_cpu_activate(unsigned int cpu)9397 int sched_cpu_activate(unsigned int cpu)
9398 {
9399 struct rq *rq = cpu_rq(cpu);
9400 struct rq_flags rf;
9401
9402 /*
9403 * Clear the balance_push callback and prepare to schedule
9404 * regular tasks.
9405 */
9406 balance_push_set(cpu, false);
9407
9408 #ifdef CONFIG_SCHED_SMT
9409 /*
9410 * When going up, increment the number of cores with SMT present.
9411 */
9412 if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
9413 static_branch_inc_cpuslocked(&sched_smt_present);
9414 #endif
9415 set_cpu_active(cpu, true);
9416
9417 if (sched_smp_initialized) {
9418 sched_update_numa(cpu, true);
9419 sched_domains_numa_masks_set(cpu);
9420 cpuset_cpu_active();
9421 }
9422
9423 /*
9424 * Put the rq online, if not already. This happens:
9425 *
9426 * 1) In the early boot process, because we build the real domains
9427 * after all CPUs have been brought up.
9428 *
9429 * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
9430 * domains.
9431 */
9432 rq_lock_irqsave(rq, &rf);
9433 if (rq->rd) {
9434 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
9435 set_rq_online(rq);
9436 }
9437 rq_unlock_irqrestore(rq, &rf);
9438
9439 return 0;
9440 }
9441
sched_cpu_deactivate(unsigned int cpu)9442 int sched_cpu_deactivate(unsigned int cpu)
9443 {
9444 struct rq *rq = cpu_rq(cpu);
9445 struct rq_flags rf;
9446 int ret;
9447
9448 /*
9449 * Remove CPU from nohz.idle_cpus_mask to prevent participating in
9450 * load balancing when not active
9451 */
9452 nohz_balance_exit_idle(rq);
9453
9454 set_cpu_active(cpu, false);
9455
9456 /*
9457 * From this point forward, this CPU will refuse to run any task that
9458 * is not: migrate_disable() or KTHREAD_IS_PER_CPU, and will actively
9459 * push those tasks away until this gets cleared, see
9460 * sched_cpu_dying().
9461 */
9462 balance_push_set(cpu, true);
9463
9464 /*
9465 * We've cleared cpu_active_mask / set balance_push, wait for all
9466 * preempt-disabled and RCU users of this state to go away such that
9467 * all new such users will observe it.
9468 *
9469 * Specifically, we rely on ttwu to no longer target this CPU, see
9470 * ttwu_queue_cond() and is_cpu_allowed().
9471 *
9472 * Do sync before park smpboot threads to take care the rcu boost case.
9473 */
9474 synchronize_rcu();
9475
9476 rq_lock_irqsave(rq, &rf);
9477 if (rq->rd) {
9478 update_rq_clock(rq);
9479 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
9480 set_rq_offline(rq);
9481 }
9482 rq_unlock_irqrestore(rq, &rf);
9483
9484 #ifdef CONFIG_SCHED_SMT
9485 /*
9486 * When going down, decrement the number of cores with SMT present.
9487 */
9488 if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
9489 static_branch_dec_cpuslocked(&sched_smt_present);
9490
9491 sched_core_cpu_deactivate(cpu);
9492 #endif
9493
9494 if (!sched_smp_initialized)
9495 return 0;
9496
9497 sched_update_numa(cpu, false);
9498 ret = cpuset_cpu_inactive(cpu);
9499 if (ret) {
9500 balance_push_set(cpu, false);
9501 set_cpu_active(cpu, true);
9502 sched_update_numa(cpu, true);
9503 return ret;
9504 }
9505 sched_domains_numa_masks_clear(cpu);
9506 return 0;
9507 }
9508
sched_rq_cpu_starting(unsigned int cpu)9509 static void sched_rq_cpu_starting(unsigned int cpu)
9510 {
9511 struct rq *rq = cpu_rq(cpu);
9512
9513 rq->calc_load_update = calc_load_update;
9514 update_max_interval();
9515 }
9516
sched_cpu_starting(unsigned int cpu)9517 int sched_cpu_starting(unsigned int cpu)
9518 {
9519 sched_core_cpu_starting(cpu);
9520 sched_rq_cpu_starting(cpu);
9521 sched_tick_start(cpu);
9522 return 0;
9523 }
9524
9525 #ifdef CONFIG_HOTPLUG_CPU
9526
9527 /*
9528 * Invoked immediately before the stopper thread is invoked to bring the
9529 * CPU down completely. At this point all per CPU kthreads except the
9530 * hotplug thread (current) and the stopper thread (inactive) have been
9531 * either parked or have been unbound from the outgoing CPU. Ensure that
9532 * any of those which might be on the way out are gone.
9533 *
9534 * If after this point a bound task is being woken on this CPU then the
9535 * responsible hotplug callback has failed to do it's job.
9536 * sched_cpu_dying() will catch it with the appropriate fireworks.
9537 */
sched_cpu_wait_empty(unsigned int cpu)9538 int sched_cpu_wait_empty(unsigned int cpu)
9539 {
9540 balance_hotplug_wait();
9541 return 0;
9542 }
9543
9544 /*
9545 * Since this CPU is going 'away' for a while, fold any nr_active delta we
9546 * might have. Called from the CPU stopper task after ensuring that the
9547 * stopper is the last running task on the CPU, so nr_active count is
9548 * stable. We need to take the teardown thread which is calling this into
9549 * account, so we hand in adjust = 1 to the load calculation.
9550 *
9551 * Also see the comment "Global load-average calculations".
9552 */
calc_load_migrate(struct rq * rq)9553 static void calc_load_migrate(struct rq *rq)
9554 {
9555 long delta = calc_load_fold_active(rq, 1);
9556
9557 if (delta)
9558 atomic_long_add(delta, &calc_load_tasks);
9559 }
9560
dump_rq_tasks(struct rq * rq,const char * loglvl)9561 static void dump_rq_tasks(struct rq *rq, const char *loglvl)
9562 {
9563 struct task_struct *g, *p;
9564 int cpu = cpu_of(rq);
9565
9566 lockdep_assert_rq_held(rq);
9567
9568 printk("%sCPU%d enqueued tasks (%u total):\n", loglvl, cpu, rq->nr_running);
9569 for_each_process_thread(g, p) {
9570 if (task_cpu(p) != cpu)
9571 continue;
9572
9573 if (!task_on_rq_queued(p))
9574 continue;
9575
9576 printk("%s\tpid: %d, name: %s\n", loglvl, p->pid, p->comm);
9577 }
9578 }
9579
sched_cpu_dying(unsigned int cpu)9580 int sched_cpu_dying(unsigned int cpu)
9581 {
9582 struct rq *rq = cpu_rq(cpu);
9583 struct rq_flags rf;
9584
9585 /* Handle pending wakeups and then migrate everything off */
9586 sched_tick_stop(cpu);
9587
9588 rq_lock_irqsave(rq, &rf);
9589 if (rq->nr_running != 1 || rq_has_pinned_tasks(rq)) {
9590 WARN(true, "Dying CPU not properly vacated!");
9591 dump_rq_tasks(rq, KERN_WARNING);
9592 }
9593 rq_unlock_irqrestore(rq, &rf);
9594
9595 calc_load_migrate(rq);
9596 update_max_interval();
9597 hrtick_clear(rq);
9598 sched_core_cpu_dying(cpu);
9599 return 0;
9600 }
9601 #endif
9602
sched_init_smp(void)9603 void __init sched_init_smp(void)
9604 {
9605 sched_init_numa(NUMA_NO_NODE);
9606
9607 /*
9608 * There's no userspace yet to cause hotplug operations; hence all the
9609 * CPU masks are stable and all blatant races in the below code cannot
9610 * happen.
9611 */
9612 mutex_lock(&sched_domains_mutex);
9613 sched_init_domains(cpu_active_mask);
9614 mutex_unlock(&sched_domains_mutex);
9615
9616 /* Move init over to a non-isolated CPU */
9617 if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_TYPE_DOMAIN)) < 0)
9618 BUG();
9619 current->flags &= ~PF_NO_SETAFFINITY;
9620 sched_init_granularity();
9621
9622 init_sched_rt_class();
9623 init_sched_dl_class();
9624
9625 sched_smp_initialized = true;
9626 }
9627
migration_init(void)9628 static int __init migration_init(void)
9629 {
9630 sched_cpu_starting(smp_processor_id());
9631 return 0;
9632 }
9633 early_initcall(migration_init);
9634
9635 #else
sched_init_smp(void)9636 void __init sched_init_smp(void)
9637 {
9638 sched_init_granularity();
9639 }
9640 #endif /* CONFIG_SMP */
9641
in_sched_functions(unsigned long addr)9642 int in_sched_functions(unsigned long addr)
9643 {
9644 return in_lock_functions(addr) ||
9645 (addr >= (unsigned long)__sched_text_start
9646 && addr < (unsigned long)__sched_text_end);
9647 }
9648
9649 #ifdef CONFIG_CGROUP_SCHED
9650 /*
9651 * Default task group.
9652 * Every task in system belongs to this group at bootup.
9653 */
9654 struct task_group root_task_group;
9655 LIST_HEAD(task_groups);
9656
9657 /* Cacheline aligned slab cache for task_group */
9658 static struct kmem_cache *task_group_cache __read_mostly;
9659 #endif
9660
sched_init(void)9661 void __init sched_init(void)
9662 {
9663 unsigned long ptr = 0;
9664 int i;
9665
9666 /* Make sure the linker didn't screw up */
9667 BUG_ON(&idle_sched_class != &fair_sched_class + 1 ||
9668 &fair_sched_class != &rt_sched_class + 1 ||
9669 &rt_sched_class != &dl_sched_class + 1);
9670 #ifdef CONFIG_SMP
9671 BUG_ON(&dl_sched_class != &stop_sched_class + 1);
9672 #endif
9673
9674 wait_bit_init();
9675
9676 #ifdef CONFIG_FAIR_GROUP_SCHED
9677 ptr += 2 * nr_cpu_ids * sizeof(void **);
9678 #endif
9679 #ifdef CONFIG_RT_GROUP_SCHED
9680 ptr += 2 * nr_cpu_ids * sizeof(void **);
9681 #endif
9682 if (ptr) {
9683 ptr = (unsigned long)kzalloc(ptr, GFP_NOWAIT);
9684
9685 #ifdef CONFIG_FAIR_GROUP_SCHED
9686 root_task_group.se = (struct sched_entity **)ptr;
9687 ptr += nr_cpu_ids * sizeof(void **);
9688
9689 root_task_group.cfs_rq = (struct cfs_rq **)ptr;
9690 ptr += nr_cpu_ids * sizeof(void **);
9691
9692 root_task_group.shares = ROOT_TASK_GROUP_LOAD;
9693 init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
9694 #endif /* CONFIG_FAIR_GROUP_SCHED */
9695 #ifdef CONFIG_RT_GROUP_SCHED
9696 root_task_group.rt_se = (struct sched_rt_entity **)ptr;
9697 ptr += nr_cpu_ids * sizeof(void **);
9698
9699 root_task_group.rt_rq = (struct rt_rq **)ptr;
9700 ptr += nr_cpu_ids * sizeof(void **);
9701
9702 #endif /* CONFIG_RT_GROUP_SCHED */
9703 }
9704
9705 init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
9706
9707 #ifdef CONFIG_SMP
9708 init_defrootdomain();
9709 #endif
9710
9711 #ifdef CONFIG_RT_GROUP_SCHED
9712 init_rt_bandwidth(&root_task_group.rt_bandwidth,
9713 global_rt_period(), global_rt_runtime());
9714 #endif /* CONFIG_RT_GROUP_SCHED */
9715
9716 #ifdef CONFIG_CGROUP_SCHED
9717 task_group_cache = KMEM_CACHE(task_group, 0);
9718
9719 list_add(&root_task_group.list, &task_groups);
9720 INIT_LIST_HEAD(&root_task_group.children);
9721 INIT_LIST_HEAD(&root_task_group.siblings);
9722 autogroup_init(&init_task);
9723 #endif /* CONFIG_CGROUP_SCHED */
9724
9725 for_each_possible_cpu(i) {
9726 struct rq *rq;
9727
9728 rq = cpu_rq(i);
9729 raw_spin_lock_init(&rq->__lock);
9730 rq->nr_running = 0;
9731 rq->calc_load_active = 0;
9732 rq->calc_load_update = jiffies + LOAD_FREQ;
9733 init_cfs_rq(&rq->cfs);
9734 init_rt_rq(&rq->rt);
9735 init_dl_rq(&rq->dl);
9736 #ifdef CONFIG_FAIR_GROUP_SCHED
9737 INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
9738 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
9739 /*
9740 * How much CPU bandwidth does root_task_group get?
9741 *
9742 * In case of task-groups formed thr' the cgroup filesystem, it
9743 * gets 100% of the CPU resources in the system. This overall
9744 * system CPU resource is divided among the tasks of
9745 * root_task_group and its child task-groups in a fair manner,
9746 * based on each entity's (task or task-group's) weight
9747 * (se->load.weight).
9748 *
9749 * In other words, if root_task_group has 10 tasks of weight
9750 * 1024) and two child groups A0 and A1 (of weight 1024 each),
9751 * then A0's share of the CPU resource is:
9752 *
9753 * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
9754 *
9755 * We achieve this by letting root_task_group's tasks sit
9756 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
9757 */
9758 init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
9759 #endif /* CONFIG_FAIR_GROUP_SCHED */
9760
9761 rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
9762 #ifdef CONFIG_RT_GROUP_SCHED
9763 init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
9764 #endif
9765 #ifdef CONFIG_SMP
9766 rq->sd = NULL;
9767 rq->rd = NULL;
9768 rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE;
9769 rq->balance_callback = &balance_push_callback;
9770 rq->active_balance = 0;
9771 rq->next_balance = jiffies;
9772 rq->push_cpu = 0;
9773 rq->cpu = i;
9774 rq->online = 0;
9775 rq->idle_stamp = 0;
9776 rq->avg_idle = 2*sysctl_sched_migration_cost;
9777 rq->wake_stamp = jiffies;
9778 rq->wake_avg_idle = rq->avg_idle;
9779 rq->max_idle_balance_cost = sysctl_sched_migration_cost;
9780
9781 INIT_LIST_HEAD(&rq->cfs_tasks);
9782
9783 rq_attach_root(rq, &def_root_domain);
9784 #ifdef CONFIG_NO_HZ_COMMON
9785 rq->last_blocked_load_update_tick = jiffies;
9786 atomic_set(&rq->nohz_flags, 0);
9787
9788 INIT_CSD(&rq->nohz_csd, nohz_csd_func, rq);
9789 #endif
9790 #ifdef CONFIG_HOTPLUG_CPU
9791 rcuwait_init(&rq->hotplug_wait);
9792 #endif
9793 #endif /* CONFIG_SMP */
9794 hrtick_rq_init(rq);
9795 atomic_set(&rq->nr_iowait, 0);
9796
9797 #ifdef CONFIG_SCHED_CORE
9798 rq->core = rq;
9799 rq->core_pick = NULL;
9800 rq->core_enabled = 0;
9801 rq->core_tree = RB_ROOT;
9802 rq->core_forceidle_count = 0;
9803 rq->core_forceidle_occupation = 0;
9804 rq->core_forceidle_start = 0;
9805
9806 rq->core_cookie = 0UL;
9807 #endif
9808 }
9809
9810 set_load_weight(&init_task, false);
9811
9812 /*
9813 * The boot idle thread does lazy MMU switching as well:
9814 */
9815 mmgrab(&init_mm);
9816 enter_lazy_tlb(&init_mm, current);
9817
9818 /*
9819 * The idle task doesn't need the kthread struct to function, but it
9820 * is dressed up as a per-CPU kthread and thus needs to play the part
9821 * if we want to avoid special-casing it in code that deals with per-CPU
9822 * kthreads.
9823 */
9824 WARN_ON(!set_kthread_struct(current));
9825
9826 /*
9827 * Make us the idle thread. Technically, schedule() should not be
9828 * called from this thread, however somewhere below it might be,
9829 * but because we are the idle thread, we just pick up running again
9830 * when this runqueue becomes "idle".
9831 */
9832 init_idle(current, smp_processor_id());
9833
9834 calc_load_update = jiffies + LOAD_FREQ;
9835
9836 #ifdef CONFIG_SMP
9837 idle_thread_set_boot_cpu();
9838 balance_push_set(smp_processor_id(), false);
9839 #endif
9840 init_sched_fair_class();
9841
9842 psi_init();
9843
9844 init_uclamp();
9845
9846 preempt_dynamic_init();
9847
9848 scheduler_running = 1;
9849 }
9850
9851 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
9852
__might_sleep(const char * file,int line)9853 void __might_sleep(const char *file, int line)
9854 {
9855 unsigned int state = get_current_state();
9856 /*
9857 * Blocking primitives will set (and therefore destroy) current->state,
9858 * since we will exit with TASK_RUNNING make sure we enter with it,
9859 * otherwise we will destroy state.
9860 */
9861 WARN_ONCE(state != TASK_RUNNING && current->task_state_change,
9862 "do not call blocking ops when !TASK_RUNNING; "
9863 "state=%x set at [<%p>] %pS\n", state,
9864 (void *)current->task_state_change,
9865 (void *)current->task_state_change);
9866
9867 __might_resched(file, line, 0);
9868 }
9869 EXPORT_SYMBOL(__might_sleep);
9870
print_preempt_disable_ip(int preempt_offset,unsigned long ip)9871 static void print_preempt_disable_ip(int preempt_offset, unsigned long ip)
9872 {
9873 if (!IS_ENABLED(CONFIG_DEBUG_PREEMPT))
9874 return;
9875
9876 if (preempt_count() == preempt_offset)
9877 return;
9878
9879 pr_err("Preemption disabled at:");
9880 print_ip_sym(KERN_ERR, ip);
9881 }
9882
resched_offsets_ok(unsigned int offsets)9883 static inline bool resched_offsets_ok(unsigned int offsets)
9884 {
9885 unsigned int nested = preempt_count();
9886
9887 nested += rcu_preempt_depth() << MIGHT_RESCHED_RCU_SHIFT;
9888
9889 return nested == offsets;
9890 }
9891
__might_resched(const char * file,int line,unsigned int offsets)9892 void __might_resched(const char *file, int line, unsigned int offsets)
9893 {
9894 /* Ratelimiting timestamp: */
9895 static unsigned long prev_jiffy;
9896
9897 unsigned long preempt_disable_ip;
9898
9899 /* WARN_ON_ONCE() by default, no rate limit required: */
9900 rcu_sleep_check();
9901
9902 if ((resched_offsets_ok(offsets) && !irqs_disabled() &&
9903 !is_idle_task(current) && !current->non_block_count) ||
9904 system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
9905 oops_in_progress)
9906 return;
9907
9908 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
9909 return;
9910 prev_jiffy = jiffies;
9911
9912 /* Save this before calling printk(), since that will clobber it: */
9913 preempt_disable_ip = get_preempt_disable_ip(current);
9914
9915 pr_err("BUG: sleeping function called from invalid context at %s:%d\n",
9916 file, line);
9917 pr_err("in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n",
9918 in_atomic(), irqs_disabled(), current->non_block_count,
9919 current->pid, current->comm);
9920 pr_err("preempt_count: %x, expected: %x\n", preempt_count(),
9921 offsets & MIGHT_RESCHED_PREEMPT_MASK);
9922
9923 if (IS_ENABLED(CONFIG_PREEMPT_RCU)) {
9924 pr_err("RCU nest depth: %d, expected: %u\n",
9925 rcu_preempt_depth(), offsets >> MIGHT_RESCHED_RCU_SHIFT);
9926 }
9927
9928 if (task_stack_end_corrupted(current))
9929 pr_emerg("Thread overran stack, or stack corrupted\n");
9930
9931 debug_show_held_locks(current);
9932 if (irqs_disabled())
9933 print_irqtrace_events(current);
9934
9935 print_preempt_disable_ip(offsets & MIGHT_RESCHED_PREEMPT_MASK,
9936 preempt_disable_ip);
9937
9938 dump_stack();
9939 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
9940 }
9941 EXPORT_SYMBOL(__might_resched);
9942
__cant_sleep(const char * file,int line,int preempt_offset)9943 void __cant_sleep(const char *file, int line, int preempt_offset)
9944 {
9945 static unsigned long prev_jiffy;
9946
9947 if (irqs_disabled())
9948 return;
9949
9950 if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
9951 return;
9952
9953 if (preempt_count() > preempt_offset)
9954 return;
9955
9956 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
9957 return;
9958 prev_jiffy = jiffies;
9959
9960 printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line);
9961 printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
9962 in_atomic(), irqs_disabled(),
9963 current->pid, current->comm);
9964
9965 debug_show_held_locks(current);
9966 dump_stack();
9967 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
9968 }
9969 EXPORT_SYMBOL_GPL(__cant_sleep);
9970
9971 #ifdef CONFIG_SMP
__cant_migrate(const char * file,int line)9972 void __cant_migrate(const char *file, int line)
9973 {
9974 static unsigned long prev_jiffy;
9975
9976 if (irqs_disabled())
9977 return;
9978
9979 if (is_migration_disabled(current))
9980 return;
9981
9982 if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
9983 return;
9984
9985 if (preempt_count() > 0)
9986 return;
9987
9988 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
9989 return;
9990 prev_jiffy = jiffies;
9991
9992 pr_err("BUG: assuming non migratable context at %s:%d\n", file, line);
9993 pr_err("in_atomic(): %d, irqs_disabled(): %d, migration_disabled() %u pid: %d, name: %s\n",
9994 in_atomic(), irqs_disabled(), is_migration_disabled(current),
9995 current->pid, current->comm);
9996
9997 debug_show_held_locks(current);
9998 dump_stack();
9999 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
10000 }
10001 EXPORT_SYMBOL_GPL(__cant_migrate);
10002 #endif
10003 #endif
10004
10005 #ifdef CONFIG_MAGIC_SYSRQ
normalize_rt_tasks(void)10006 void normalize_rt_tasks(void)
10007 {
10008 struct task_struct *g, *p;
10009 struct sched_attr attr = {
10010 .sched_policy = SCHED_NORMAL,
10011 };
10012
10013 read_lock(&tasklist_lock);
10014 for_each_process_thread(g, p) {
10015 /*
10016 * Only normalize user tasks:
10017 */
10018 if (p->flags & PF_KTHREAD)
10019 continue;
10020
10021 p->se.exec_start = 0;
10022 schedstat_set(p->stats.wait_start, 0);
10023 schedstat_set(p->stats.sleep_start, 0);
10024 schedstat_set(p->stats.block_start, 0);
10025
10026 if (!dl_task(p) && !rt_task(p)) {
10027 /*
10028 * Renice negative nice level userspace
10029 * tasks back to 0:
10030 */
10031 if (task_nice(p) < 0)
10032 set_user_nice(p, 0);
10033 continue;
10034 }
10035
10036 __sched_setscheduler(p, &attr, false, false);
10037 }
10038 read_unlock(&tasklist_lock);
10039 }
10040
10041 #endif /* CONFIG_MAGIC_SYSRQ */
10042
10043 #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
10044 /*
10045 * These functions are only useful for the IA64 MCA handling, or kdb.
10046 *
10047 * They can only be called when the whole system has been
10048 * stopped - every CPU needs to be quiescent, and no scheduling
10049 * activity can take place. Using them for anything else would
10050 * be a serious bug, and as a result, they aren't even visible
10051 * under any other configuration.
10052 */
10053
10054 /**
10055 * curr_task - return the current task for a given CPU.
10056 * @cpu: the processor in question.
10057 *
10058 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
10059 *
10060 * Return: The current task for @cpu.
10061 */
curr_task(int cpu)10062 struct task_struct *curr_task(int cpu)
10063 {
10064 return cpu_curr(cpu);
10065 }
10066
10067 #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
10068
10069 #ifdef CONFIG_IA64
10070 /**
10071 * ia64_set_curr_task - set the current task for a given CPU.
10072 * @cpu: the processor in question.
10073 * @p: the task pointer to set.
10074 *
10075 * Description: This function must only be used when non-maskable interrupts
10076 * are serviced on a separate stack. It allows the architecture to switch the
10077 * notion of the current task on a CPU in a non-blocking manner. This function
10078 * must be called with all CPU's synchronized, and interrupts disabled, the
10079 * and caller must save the original value of the current task (see
10080 * curr_task() above) and restore that value before reenabling interrupts and
10081 * re-starting the system.
10082 *
10083 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
10084 */
ia64_set_curr_task(int cpu,struct task_struct * p)10085 void ia64_set_curr_task(int cpu, struct task_struct *p)
10086 {
10087 cpu_curr(cpu) = p;
10088 }
10089
10090 #endif
10091
10092 #ifdef CONFIG_CGROUP_SCHED
10093 /* task_group_lock serializes the addition/removal of task groups */
10094 static DEFINE_SPINLOCK(task_group_lock);
10095
alloc_uclamp_sched_group(struct task_group * tg,struct task_group * parent)10096 static inline void alloc_uclamp_sched_group(struct task_group *tg,
10097 struct task_group *parent)
10098 {
10099 #ifdef CONFIG_UCLAMP_TASK_GROUP
10100 enum uclamp_id clamp_id;
10101
10102 for_each_clamp_id(clamp_id) {
10103 uclamp_se_set(&tg->uclamp_req[clamp_id],
10104 uclamp_none(clamp_id), false);
10105 tg->uclamp[clamp_id] = parent->uclamp[clamp_id];
10106 }
10107 #endif
10108 }
10109
sched_free_group(struct task_group * tg)10110 static void sched_free_group(struct task_group *tg)
10111 {
10112 free_fair_sched_group(tg);
10113 free_rt_sched_group(tg);
10114 autogroup_free(tg);
10115 kmem_cache_free(task_group_cache, tg);
10116 }
10117
sched_free_group_rcu(struct rcu_head * rcu)10118 static void sched_free_group_rcu(struct rcu_head *rcu)
10119 {
10120 sched_free_group(container_of(rcu, struct task_group, rcu));
10121 }
10122
sched_unregister_group(struct task_group * tg)10123 static void sched_unregister_group(struct task_group *tg)
10124 {
10125 unregister_fair_sched_group(tg);
10126 unregister_rt_sched_group(tg);
10127 /*
10128 * We have to wait for yet another RCU grace period to expire, as
10129 * print_cfs_stats() might run concurrently.
10130 */
10131 call_rcu(&tg->rcu, sched_free_group_rcu);
10132 }
10133
10134 /* allocate runqueue etc for a new task group */
sched_create_group(struct task_group * parent)10135 struct task_group *sched_create_group(struct task_group *parent)
10136 {
10137 struct task_group *tg;
10138
10139 tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
10140 if (!tg)
10141 return ERR_PTR(-ENOMEM);
10142
10143 if (!alloc_fair_sched_group(tg, parent))
10144 goto err;
10145
10146 if (!alloc_rt_sched_group(tg, parent))
10147 goto err;
10148
10149 alloc_uclamp_sched_group(tg, parent);
10150
10151 return tg;
10152
10153 err:
10154 sched_free_group(tg);
10155 return ERR_PTR(-ENOMEM);
10156 }
10157
sched_online_group(struct task_group * tg,struct task_group * parent)10158 void sched_online_group(struct task_group *tg, struct task_group *parent)
10159 {
10160 unsigned long flags;
10161
10162 spin_lock_irqsave(&task_group_lock, flags);
10163 list_add_rcu(&tg->list, &task_groups);
10164
10165 /* Root should already exist: */
10166 WARN_ON(!parent);
10167
10168 tg->parent = parent;
10169 INIT_LIST_HEAD(&tg->children);
10170 list_add_rcu(&tg->siblings, &parent->children);
10171 spin_unlock_irqrestore(&task_group_lock, flags);
10172
10173 online_fair_sched_group(tg);
10174 }
10175
10176 /* rcu callback to free various structures associated with a task group */
sched_unregister_group_rcu(struct rcu_head * rhp)10177 static void sched_unregister_group_rcu(struct rcu_head *rhp)
10178 {
10179 /* Now it should be safe to free those cfs_rqs: */
10180 sched_unregister_group(container_of(rhp, struct task_group, rcu));
10181 }
10182
sched_destroy_group(struct task_group * tg)10183 void sched_destroy_group(struct task_group *tg)
10184 {
10185 /* Wait for possible concurrent references to cfs_rqs complete: */
10186 call_rcu(&tg->rcu, sched_unregister_group_rcu);
10187 }
10188
sched_release_group(struct task_group * tg)10189 void sched_release_group(struct task_group *tg)
10190 {
10191 unsigned long flags;
10192
10193 /*
10194 * Unlink first, to avoid walk_tg_tree_from() from finding us (via
10195 * sched_cfs_period_timer()).
10196 *
10197 * For this to be effective, we have to wait for all pending users of
10198 * this task group to leave their RCU critical section to ensure no new
10199 * user will see our dying task group any more. Specifically ensure
10200 * that tg_unthrottle_up() won't add decayed cfs_rq's to it.
10201 *
10202 * We therefore defer calling unregister_fair_sched_group() to
10203 * sched_unregister_group() which is guarantied to get called only after the
10204 * current RCU grace period has expired.
10205 */
10206 spin_lock_irqsave(&task_group_lock, flags);
10207 list_del_rcu(&tg->list);
10208 list_del_rcu(&tg->siblings);
10209 spin_unlock_irqrestore(&task_group_lock, flags);
10210 }
10211
sched_change_group(struct task_struct * tsk)10212 static void sched_change_group(struct task_struct *tsk)
10213 {
10214 struct task_group *tg;
10215
10216 /*
10217 * All callers are synchronized by task_rq_lock(); we do not use RCU
10218 * which is pointless here. Thus, we pass "true" to task_css_check()
10219 * to prevent lockdep warnings.
10220 */
10221 tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
10222 struct task_group, css);
10223 tg = autogroup_task_group(tsk, tg);
10224 tsk->sched_task_group = tg;
10225
10226 #ifdef CONFIG_FAIR_GROUP_SCHED
10227 if (tsk->sched_class->task_change_group)
10228 tsk->sched_class->task_change_group(tsk);
10229 else
10230 #endif
10231 set_task_rq(tsk, task_cpu(tsk));
10232 }
10233
10234 /*
10235 * Change task's runqueue when it moves between groups.
10236 *
10237 * The caller of this function should have put the task in its new group by
10238 * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
10239 * its new group.
10240 */
sched_move_task(struct task_struct * tsk)10241 void sched_move_task(struct task_struct *tsk)
10242 {
10243 int queued, running, queue_flags =
10244 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
10245 struct rq_flags rf;
10246 struct rq *rq;
10247
10248 rq = task_rq_lock(tsk, &rf);
10249 update_rq_clock(rq);
10250
10251 running = task_current(rq, tsk);
10252 queued = task_on_rq_queued(tsk);
10253
10254 if (queued)
10255 dequeue_task(rq, tsk, queue_flags);
10256 if (running)
10257 put_prev_task(rq, tsk);
10258
10259 sched_change_group(tsk);
10260
10261 if (queued)
10262 enqueue_task(rq, tsk, queue_flags);
10263 if (running) {
10264 set_next_task(rq, tsk);
10265 /*
10266 * After changing group, the running task may have joined a
10267 * throttled one but it's still the running task. Trigger a
10268 * resched to make sure that task can still run.
10269 */
10270 resched_curr(rq);
10271 }
10272
10273 task_rq_unlock(rq, tsk, &rf);
10274 }
10275
css_tg(struct cgroup_subsys_state * css)10276 static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
10277 {
10278 return css ? container_of(css, struct task_group, css) : NULL;
10279 }
10280
10281 static struct cgroup_subsys_state *
cpu_cgroup_css_alloc(struct cgroup_subsys_state * parent_css)10282 cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
10283 {
10284 struct task_group *parent = css_tg(parent_css);
10285 struct task_group *tg;
10286
10287 if (!parent) {
10288 /* This is early initialization for the top cgroup */
10289 return &root_task_group.css;
10290 }
10291
10292 tg = sched_create_group(parent);
10293 if (IS_ERR(tg))
10294 return ERR_PTR(-ENOMEM);
10295
10296 return &tg->css;
10297 }
10298
10299 /* Expose task group only after completing cgroup initialization */
cpu_cgroup_css_online(struct cgroup_subsys_state * css)10300 static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
10301 {
10302 struct task_group *tg = css_tg(css);
10303 struct task_group *parent = css_tg(css->parent);
10304
10305 if (parent)
10306 sched_online_group(tg, parent);
10307
10308 #ifdef CONFIG_UCLAMP_TASK_GROUP
10309 /* Propagate the effective uclamp value for the new group */
10310 mutex_lock(&uclamp_mutex);
10311 rcu_read_lock();
10312 cpu_util_update_eff(css);
10313 rcu_read_unlock();
10314 mutex_unlock(&uclamp_mutex);
10315 #endif
10316
10317 return 0;
10318 }
10319
cpu_cgroup_css_released(struct cgroup_subsys_state * css)10320 static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
10321 {
10322 struct task_group *tg = css_tg(css);
10323
10324 sched_release_group(tg);
10325 }
10326
cpu_cgroup_css_free(struct cgroup_subsys_state * css)10327 static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
10328 {
10329 struct task_group *tg = css_tg(css);
10330
10331 /*
10332 * Relies on the RCU grace period between css_released() and this.
10333 */
10334 sched_unregister_group(tg);
10335 }
10336
10337 #ifdef CONFIG_RT_GROUP_SCHED
cpu_cgroup_can_attach(struct cgroup_taskset * tset)10338 static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
10339 {
10340 struct task_struct *task;
10341 struct cgroup_subsys_state *css;
10342
10343 cgroup_taskset_for_each(task, css, tset) {
10344 if (!sched_rt_can_attach(css_tg(css), task))
10345 return -EINVAL;
10346 }
10347 return 0;
10348 }
10349 #endif
10350
cpu_cgroup_attach(struct cgroup_taskset * tset)10351 static void cpu_cgroup_attach(struct cgroup_taskset *tset)
10352 {
10353 struct task_struct *task;
10354 struct cgroup_subsys_state *css;
10355
10356 cgroup_taskset_for_each(task, css, tset)
10357 sched_move_task(task);
10358 }
10359
10360 #ifdef CONFIG_UCLAMP_TASK_GROUP
cpu_util_update_eff(struct cgroup_subsys_state * css)10361 static void cpu_util_update_eff(struct cgroup_subsys_state *css)
10362 {
10363 struct cgroup_subsys_state *top_css = css;
10364 struct uclamp_se *uc_parent = NULL;
10365 struct uclamp_se *uc_se = NULL;
10366 unsigned int eff[UCLAMP_CNT];
10367 enum uclamp_id clamp_id;
10368 unsigned int clamps;
10369
10370 lockdep_assert_held(&uclamp_mutex);
10371 SCHED_WARN_ON(!rcu_read_lock_held());
10372
10373 css_for_each_descendant_pre(css, top_css) {
10374 uc_parent = css_tg(css)->parent
10375 ? css_tg(css)->parent->uclamp : NULL;
10376
10377 for_each_clamp_id(clamp_id) {
10378 /* Assume effective clamps matches requested clamps */
10379 eff[clamp_id] = css_tg(css)->uclamp_req[clamp_id].value;
10380 /* Cap effective clamps with parent's effective clamps */
10381 if (uc_parent &&
10382 eff[clamp_id] > uc_parent[clamp_id].value) {
10383 eff[clamp_id] = uc_parent[clamp_id].value;
10384 }
10385 }
10386 /* Ensure protection is always capped by limit */
10387 eff[UCLAMP_MIN] = min(eff[UCLAMP_MIN], eff[UCLAMP_MAX]);
10388
10389 /* Propagate most restrictive effective clamps */
10390 clamps = 0x0;
10391 uc_se = css_tg(css)->uclamp;
10392 for_each_clamp_id(clamp_id) {
10393 if (eff[clamp_id] == uc_se[clamp_id].value)
10394 continue;
10395 uc_se[clamp_id].value = eff[clamp_id];
10396 uc_se[clamp_id].bucket_id = uclamp_bucket_id(eff[clamp_id]);
10397 clamps |= (0x1 << clamp_id);
10398 }
10399 if (!clamps) {
10400 css = css_rightmost_descendant(css);
10401 continue;
10402 }
10403
10404 /* Immediately update descendants RUNNABLE tasks */
10405 uclamp_update_active_tasks(css);
10406 }
10407 }
10408
10409 /*
10410 * Integer 10^N with a given N exponent by casting to integer the literal "1eN"
10411 * C expression. Since there is no way to convert a macro argument (N) into a
10412 * character constant, use two levels of macros.
10413 */
10414 #define _POW10(exp) ((unsigned int)1e##exp)
10415 #define POW10(exp) _POW10(exp)
10416
10417 struct uclamp_request {
10418 #define UCLAMP_PERCENT_SHIFT 2
10419 #define UCLAMP_PERCENT_SCALE (100 * POW10(UCLAMP_PERCENT_SHIFT))
10420 s64 percent;
10421 u64 util;
10422 int ret;
10423 };
10424
10425 static inline struct uclamp_request
capacity_from_percent(char * buf)10426 capacity_from_percent(char *buf)
10427 {
10428 struct uclamp_request req = {
10429 .percent = UCLAMP_PERCENT_SCALE,
10430 .util = SCHED_CAPACITY_SCALE,
10431 .ret = 0,
10432 };
10433
10434 buf = strim(buf);
10435 if (strcmp(buf, "max")) {
10436 req.ret = cgroup_parse_float(buf, UCLAMP_PERCENT_SHIFT,
10437 &req.percent);
10438 if (req.ret)
10439 return req;
10440 if ((u64)req.percent > UCLAMP_PERCENT_SCALE) {
10441 req.ret = -ERANGE;
10442 return req;
10443 }
10444
10445 req.util = req.percent << SCHED_CAPACITY_SHIFT;
10446 req.util = DIV_ROUND_CLOSEST_ULL(req.util, UCLAMP_PERCENT_SCALE);
10447 }
10448
10449 return req;
10450 }
10451
cpu_uclamp_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off,enum uclamp_id clamp_id)10452 static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf,
10453 size_t nbytes, loff_t off,
10454 enum uclamp_id clamp_id)
10455 {
10456 struct uclamp_request req;
10457 struct task_group *tg;
10458
10459 req = capacity_from_percent(buf);
10460 if (req.ret)
10461 return req.ret;
10462
10463 static_branch_enable(&sched_uclamp_used);
10464
10465 mutex_lock(&uclamp_mutex);
10466 rcu_read_lock();
10467
10468 tg = css_tg(of_css(of));
10469 if (tg->uclamp_req[clamp_id].value != req.util)
10470 uclamp_se_set(&tg->uclamp_req[clamp_id], req.util, false);
10471
10472 /*
10473 * Because of not recoverable conversion rounding we keep track of the
10474 * exact requested value
10475 */
10476 tg->uclamp_pct[clamp_id] = req.percent;
10477
10478 /* Update effective clamps to track the most restrictive value */
10479 cpu_util_update_eff(of_css(of));
10480
10481 rcu_read_unlock();
10482 mutex_unlock(&uclamp_mutex);
10483
10484 return nbytes;
10485 }
10486
cpu_uclamp_min_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)10487 static ssize_t cpu_uclamp_min_write(struct kernfs_open_file *of,
10488 char *buf, size_t nbytes,
10489 loff_t off)
10490 {
10491 return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MIN);
10492 }
10493
cpu_uclamp_max_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)10494 static ssize_t cpu_uclamp_max_write(struct kernfs_open_file *of,
10495 char *buf, size_t nbytes,
10496 loff_t off)
10497 {
10498 return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MAX);
10499 }
10500
cpu_uclamp_print(struct seq_file * sf,enum uclamp_id clamp_id)10501 static inline void cpu_uclamp_print(struct seq_file *sf,
10502 enum uclamp_id clamp_id)
10503 {
10504 struct task_group *tg;
10505 u64 util_clamp;
10506 u64 percent;
10507 u32 rem;
10508
10509 rcu_read_lock();
10510 tg = css_tg(seq_css(sf));
10511 util_clamp = tg->uclamp_req[clamp_id].value;
10512 rcu_read_unlock();
10513
10514 if (util_clamp == SCHED_CAPACITY_SCALE) {
10515 seq_puts(sf, "max\n");
10516 return;
10517 }
10518
10519 percent = tg->uclamp_pct[clamp_id];
10520 percent = div_u64_rem(percent, POW10(UCLAMP_PERCENT_SHIFT), &rem);
10521 seq_printf(sf, "%llu.%0*u\n", percent, UCLAMP_PERCENT_SHIFT, rem);
10522 }
10523
cpu_uclamp_min_show(struct seq_file * sf,void * v)10524 static int cpu_uclamp_min_show(struct seq_file *sf, void *v)
10525 {
10526 cpu_uclamp_print(sf, UCLAMP_MIN);
10527 return 0;
10528 }
10529
cpu_uclamp_max_show(struct seq_file * sf,void * v)10530 static int cpu_uclamp_max_show(struct seq_file *sf, void *v)
10531 {
10532 cpu_uclamp_print(sf, UCLAMP_MAX);
10533 return 0;
10534 }
10535 #endif /* CONFIG_UCLAMP_TASK_GROUP */
10536
10537 #ifdef CONFIG_FAIR_GROUP_SCHED
cpu_shares_write_u64(struct cgroup_subsys_state * css,struct cftype * cftype,u64 shareval)10538 static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
10539 struct cftype *cftype, u64 shareval)
10540 {
10541 if (shareval > scale_load_down(ULONG_MAX))
10542 shareval = MAX_SHARES;
10543 return sched_group_set_shares(css_tg(css), scale_load(shareval));
10544 }
10545
cpu_shares_read_u64(struct cgroup_subsys_state * css,struct cftype * cft)10546 static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
10547 struct cftype *cft)
10548 {
10549 struct task_group *tg = css_tg(css);
10550
10551 return (u64) scale_load_down(tg->shares);
10552 }
10553
10554 #ifdef CONFIG_CFS_BANDWIDTH
10555 static DEFINE_MUTEX(cfs_constraints_mutex);
10556
10557 const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
10558 static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
10559 /* More than 203 days if BW_SHIFT equals 20. */
10560 static const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
10561
10562 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
10563
tg_set_cfs_bandwidth(struct task_group * tg,u64 period,u64 quota,u64 burst)10564 static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
10565 u64 burst)
10566 {
10567 int i, ret = 0, runtime_enabled, runtime_was_enabled;
10568 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
10569
10570 if (tg == &root_task_group)
10571 return -EINVAL;
10572
10573 /*
10574 * Ensure we have at some amount of bandwidth every period. This is
10575 * to prevent reaching a state of large arrears when throttled via
10576 * entity_tick() resulting in prolonged exit starvation.
10577 */
10578 if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
10579 return -EINVAL;
10580
10581 /*
10582 * Likewise, bound things on the other side by preventing insane quota
10583 * periods. This also allows us to normalize in computing quota
10584 * feasibility.
10585 */
10586 if (period > max_cfs_quota_period)
10587 return -EINVAL;
10588
10589 /*
10590 * Bound quota to defend quota against overflow during bandwidth shift.
10591 */
10592 if (quota != RUNTIME_INF && quota > max_cfs_runtime)
10593 return -EINVAL;
10594
10595 if (quota != RUNTIME_INF && (burst > quota ||
10596 burst + quota > max_cfs_runtime))
10597 return -EINVAL;
10598
10599 /*
10600 * Prevent race between setting of cfs_rq->runtime_enabled and
10601 * unthrottle_offline_cfs_rqs().
10602 */
10603 cpus_read_lock();
10604 mutex_lock(&cfs_constraints_mutex);
10605 ret = __cfs_schedulable(tg, period, quota);
10606 if (ret)
10607 goto out_unlock;
10608
10609 runtime_enabled = quota != RUNTIME_INF;
10610 runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
10611 /*
10612 * If we need to toggle cfs_bandwidth_used, off->on must occur
10613 * before making related changes, and on->off must occur afterwards
10614 */
10615 if (runtime_enabled && !runtime_was_enabled)
10616 cfs_bandwidth_usage_inc();
10617 raw_spin_lock_irq(&cfs_b->lock);
10618 cfs_b->period = ns_to_ktime(period);
10619 cfs_b->quota = quota;
10620 cfs_b->burst = burst;
10621
10622 __refill_cfs_bandwidth_runtime(cfs_b);
10623
10624 /* Restart the period timer (if active) to handle new period expiry: */
10625 if (runtime_enabled)
10626 start_cfs_bandwidth(cfs_b);
10627
10628 raw_spin_unlock_irq(&cfs_b->lock);
10629
10630 for_each_online_cpu(i) {
10631 struct cfs_rq *cfs_rq = tg->cfs_rq[i];
10632 struct rq *rq = cfs_rq->rq;
10633 struct rq_flags rf;
10634
10635 rq_lock_irq(rq, &rf);
10636 cfs_rq->runtime_enabled = runtime_enabled;
10637 cfs_rq->runtime_remaining = 0;
10638
10639 if (cfs_rq->throttled)
10640 unthrottle_cfs_rq(cfs_rq);
10641 rq_unlock_irq(rq, &rf);
10642 }
10643 if (runtime_was_enabled && !runtime_enabled)
10644 cfs_bandwidth_usage_dec();
10645 out_unlock:
10646 mutex_unlock(&cfs_constraints_mutex);
10647 cpus_read_unlock();
10648
10649 return ret;
10650 }
10651
tg_set_cfs_quota(struct task_group * tg,long cfs_quota_us)10652 static int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
10653 {
10654 u64 quota, period, burst;
10655
10656 period = ktime_to_ns(tg->cfs_bandwidth.period);
10657 burst = tg->cfs_bandwidth.burst;
10658 if (cfs_quota_us < 0)
10659 quota = RUNTIME_INF;
10660 else if ((u64)cfs_quota_us <= U64_MAX / NSEC_PER_USEC)
10661 quota = (u64)cfs_quota_us * NSEC_PER_USEC;
10662 else
10663 return -EINVAL;
10664
10665 return tg_set_cfs_bandwidth(tg, period, quota, burst);
10666 }
10667
tg_get_cfs_quota(struct task_group * tg)10668 static long tg_get_cfs_quota(struct task_group *tg)
10669 {
10670 u64 quota_us;
10671
10672 if (tg->cfs_bandwidth.quota == RUNTIME_INF)
10673 return -1;
10674
10675 quota_us = tg->cfs_bandwidth.quota;
10676 do_div(quota_us, NSEC_PER_USEC);
10677
10678 return quota_us;
10679 }
10680
tg_set_cfs_period(struct task_group * tg,long cfs_period_us)10681 static int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
10682 {
10683 u64 quota, period, burst;
10684
10685 if ((u64)cfs_period_us > U64_MAX / NSEC_PER_USEC)
10686 return -EINVAL;
10687
10688 period = (u64)cfs_period_us * NSEC_PER_USEC;
10689 quota = tg->cfs_bandwidth.quota;
10690 burst = tg->cfs_bandwidth.burst;
10691
10692 return tg_set_cfs_bandwidth(tg, period, quota, burst);
10693 }
10694
tg_get_cfs_period(struct task_group * tg)10695 static long tg_get_cfs_period(struct task_group *tg)
10696 {
10697 u64 cfs_period_us;
10698
10699 cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period);
10700 do_div(cfs_period_us, NSEC_PER_USEC);
10701
10702 return cfs_period_us;
10703 }
10704
tg_set_cfs_burst(struct task_group * tg,long cfs_burst_us)10705 static int tg_set_cfs_burst(struct task_group *tg, long cfs_burst_us)
10706 {
10707 u64 quota, period, burst;
10708
10709 if ((u64)cfs_burst_us > U64_MAX / NSEC_PER_USEC)
10710 return -EINVAL;
10711
10712 burst = (u64)cfs_burst_us * NSEC_PER_USEC;
10713 period = ktime_to_ns(tg->cfs_bandwidth.period);
10714 quota = tg->cfs_bandwidth.quota;
10715
10716 return tg_set_cfs_bandwidth(tg, period, quota, burst);
10717 }
10718
tg_get_cfs_burst(struct task_group * tg)10719 static long tg_get_cfs_burst(struct task_group *tg)
10720 {
10721 u64 burst_us;
10722
10723 burst_us = tg->cfs_bandwidth.burst;
10724 do_div(burst_us, NSEC_PER_USEC);
10725
10726 return burst_us;
10727 }
10728
cpu_cfs_quota_read_s64(struct cgroup_subsys_state * css,struct cftype * cft)10729 static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css,
10730 struct cftype *cft)
10731 {
10732 return tg_get_cfs_quota(css_tg(css));
10733 }
10734
cpu_cfs_quota_write_s64(struct cgroup_subsys_state * css,struct cftype * cftype,s64 cfs_quota_us)10735 static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css,
10736 struct cftype *cftype, s64 cfs_quota_us)
10737 {
10738 return tg_set_cfs_quota(css_tg(css), cfs_quota_us);
10739 }
10740
cpu_cfs_period_read_u64(struct cgroup_subsys_state * css,struct cftype * cft)10741 static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css,
10742 struct cftype *cft)
10743 {
10744 return tg_get_cfs_period(css_tg(css));
10745 }
10746
cpu_cfs_period_write_u64(struct cgroup_subsys_state * css,struct cftype * cftype,u64 cfs_period_us)10747 static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css,
10748 struct cftype *cftype, u64 cfs_period_us)
10749 {
10750 return tg_set_cfs_period(css_tg(css), cfs_period_us);
10751 }
10752
cpu_cfs_burst_read_u64(struct cgroup_subsys_state * css,struct cftype * cft)10753 static u64 cpu_cfs_burst_read_u64(struct cgroup_subsys_state *css,
10754 struct cftype *cft)
10755 {
10756 return tg_get_cfs_burst(css_tg(css));
10757 }
10758
cpu_cfs_burst_write_u64(struct cgroup_subsys_state * css,struct cftype * cftype,u64 cfs_burst_us)10759 static int cpu_cfs_burst_write_u64(struct cgroup_subsys_state *css,
10760 struct cftype *cftype, u64 cfs_burst_us)
10761 {
10762 return tg_set_cfs_burst(css_tg(css), cfs_burst_us);
10763 }
10764
10765 struct cfs_schedulable_data {
10766 struct task_group *tg;
10767 u64 period, quota;
10768 };
10769
10770 /*
10771 * normalize group quota/period to be quota/max_period
10772 * note: units are usecs
10773 */
normalize_cfs_quota(struct task_group * tg,struct cfs_schedulable_data * d)10774 static u64 normalize_cfs_quota(struct task_group *tg,
10775 struct cfs_schedulable_data *d)
10776 {
10777 u64 quota, period;
10778
10779 if (tg == d->tg) {
10780 period = d->period;
10781 quota = d->quota;
10782 } else {
10783 period = tg_get_cfs_period(tg);
10784 quota = tg_get_cfs_quota(tg);
10785 }
10786
10787 /* note: these should typically be equivalent */
10788 if (quota == RUNTIME_INF || quota == -1)
10789 return RUNTIME_INF;
10790
10791 return to_ratio(period, quota);
10792 }
10793
tg_cfs_schedulable_down(struct task_group * tg,void * data)10794 static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
10795 {
10796 struct cfs_schedulable_data *d = data;
10797 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
10798 s64 quota = 0, parent_quota = -1;
10799
10800 if (!tg->parent) {
10801 quota = RUNTIME_INF;
10802 } else {
10803 struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth;
10804
10805 quota = normalize_cfs_quota(tg, d);
10806 parent_quota = parent_b->hierarchical_quota;
10807
10808 /*
10809 * Ensure max(child_quota) <= parent_quota. On cgroup2,
10810 * always take the min. On cgroup1, only inherit when no
10811 * limit is set:
10812 */
10813 if (cgroup_subsys_on_dfl(cpu_cgrp_subsys)) {
10814 quota = min(quota, parent_quota);
10815 } else {
10816 if (quota == RUNTIME_INF)
10817 quota = parent_quota;
10818 else if (parent_quota != RUNTIME_INF && quota > parent_quota)
10819 return -EINVAL;
10820 }
10821 }
10822 cfs_b->hierarchical_quota = quota;
10823
10824 return 0;
10825 }
10826
__cfs_schedulable(struct task_group * tg,u64 period,u64 quota)10827 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
10828 {
10829 int ret;
10830 struct cfs_schedulable_data data = {
10831 .tg = tg,
10832 .period = period,
10833 .quota = quota,
10834 };
10835
10836 if (quota != RUNTIME_INF) {
10837 do_div(data.period, NSEC_PER_USEC);
10838 do_div(data.quota, NSEC_PER_USEC);
10839 }
10840
10841 rcu_read_lock();
10842 ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
10843 rcu_read_unlock();
10844
10845 return ret;
10846 }
10847
cpu_cfs_stat_show(struct seq_file * sf,void * v)10848 static int cpu_cfs_stat_show(struct seq_file *sf, void *v)
10849 {
10850 struct task_group *tg = css_tg(seq_css(sf));
10851 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
10852
10853 seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods);
10854 seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled);
10855 seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time);
10856
10857 if (schedstat_enabled() && tg != &root_task_group) {
10858 struct sched_statistics *stats;
10859 u64 ws = 0;
10860 int i;
10861
10862 for_each_possible_cpu(i) {
10863 stats = __schedstats_from_se(tg->se[i]);
10864 ws += schedstat_val(stats->wait_sum);
10865 }
10866
10867 seq_printf(sf, "wait_sum %llu\n", ws);
10868 }
10869
10870 seq_printf(sf, "nr_bursts %d\n", cfs_b->nr_burst);
10871 seq_printf(sf, "burst_time %llu\n", cfs_b->burst_time);
10872
10873 return 0;
10874 }
10875 #endif /* CONFIG_CFS_BANDWIDTH */
10876 #endif /* CONFIG_FAIR_GROUP_SCHED */
10877
10878 #ifdef CONFIG_RT_GROUP_SCHED
cpu_rt_runtime_write(struct cgroup_subsys_state * css,struct cftype * cft,s64 val)10879 static int cpu_rt_runtime_write(struct cgroup_subsys_state *css,
10880 struct cftype *cft, s64 val)
10881 {
10882 return sched_group_set_rt_runtime(css_tg(css), val);
10883 }
10884
cpu_rt_runtime_read(struct cgroup_subsys_state * css,struct cftype * cft)10885 static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css,
10886 struct cftype *cft)
10887 {
10888 return sched_group_rt_runtime(css_tg(css));
10889 }
10890
cpu_rt_period_write_uint(struct cgroup_subsys_state * css,struct cftype * cftype,u64 rt_period_us)10891 static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css,
10892 struct cftype *cftype, u64 rt_period_us)
10893 {
10894 return sched_group_set_rt_period(css_tg(css), rt_period_us);
10895 }
10896
cpu_rt_period_read_uint(struct cgroup_subsys_state * css,struct cftype * cft)10897 static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
10898 struct cftype *cft)
10899 {
10900 return sched_group_rt_period(css_tg(css));
10901 }
10902 #endif /* CONFIG_RT_GROUP_SCHED */
10903
10904 #ifdef CONFIG_FAIR_GROUP_SCHED
cpu_idle_read_s64(struct cgroup_subsys_state * css,struct cftype * cft)10905 static s64 cpu_idle_read_s64(struct cgroup_subsys_state *css,
10906 struct cftype *cft)
10907 {
10908 return css_tg(css)->idle;
10909 }
10910
cpu_idle_write_s64(struct cgroup_subsys_state * css,struct cftype * cft,s64 idle)10911 static int cpu_idle_write_s64(struct cgroup_subsys_state *css,
10912 struct cftype *cft, s64 idle)
10913 {
10914 return sched_group_set_idle(css_tg(css), idle);
10915 }
10916 #endif
10917
10918 static struct cftype cpu_legacy_files[] = {
10919 #ifdef CONFIG_FAIR_GROUP_SCHED
10920 {
10921 .name = "shares",
10922 .read_u64 = cpu_shares_read_u64,
10923 .write_u64 = cpu_shares_write_u64,
10924 },
10925 {
10926 .name = "idle",
10927 .read_s64 = cpu_idle_read_s64,
10928 .write_s64 = cpu_idle_write_s64,
10929 },
10930 #endif
10931 #ifdef CONFIG_CFS_BANDWIDTH
10932 {
10933 .name = "cfs_quota_us",
10934 .read_s64 = cpu_cfs_quota_read_s64,
10935 .write_s64 = cpu_cfs_quota_write_s64,
10936 },
10937 {
10938 .name = "cfs_period_us",
10939 .read_u64 = cpu_cfs_period_read_u64,
10940 .write_u64 = cpu_cfs_period_write_u64,
10941 },
10942 {
10943 .name = "cfs_burst_us",
10944 .read_u64 = cpu_cfs_burst_read_u64,
10945 .write_u64 = cpu_cfs_burst_write_u64,
10946 },
10947 {
10948 .name = "stat",
10949 .seq_show = cpu_cfs_stat_show,
10950 },
10951 #endif
10952 #ifdef CONFIG_RT_GROUP_SCHED
10953 {
10954 .name = "rt_runtime_us",
10955 .read_s64 = cpu_rt_runtime_read,
10956 .write_s64 = cpu_rt_runtime_write,
10957 },
10958 {
10959 .name = "rt_period_us",
10960 .read_u64 = cpu_rt_period_read_uint,
10961 .write_u64 = cpu_rt_period_write_uint,
10962 },
10963 #endif
10964 #ifdef CONFIG_UCLAMP_TASK_GROUP
10965 {
10966 .name = "uclamp.min",
10967 .flags = CFTYPE_NOT_ON_ROOT,
10968 .seq_show = cpu_uclamp_min_show,
10969 .write = cpu_uclamp_min_write,
10970 },
10971 {
10972 .name = "uclamp.max",
10973 .flags = CFTYPE_NOT_ON_ROOT,
10974 .seq_show = cpu_uclamp_max_show,
10975 .write = cpu_uclamp_max_write,
10976 },
10977 #endif
10978 { } /* Terminate */
10979 };
10980
cpu_extra_stat_show(struct seq_file * sf,struct cgroup_subsys_state * css)10981 static int cpu_extra_stat_show(struct seq_file *sf,
10982 struct cgroup_subsys_state *css)
10983 {
10984 #ifdef CONFIG_CFS_BANDWIDTH
10985 {
10986 struct task_group *tg = css_tg(css);
10987 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
10988 u64 throttled_usec, burst_usec;
10989
10990 throttled_usec = cfs_b->throttled_time;
10991 do_div(throttled_usec, NSEC_PER_USEC);
10992 burst_usec = cfs_b->burst_time;
10993 do_div(burst_usec, NSEC_PER_USEC);
10994
10995 seq_printf(sf, "nr_periods %d\n"
10996 "nr_throttled %d\n"
10997 "throttled_usec %llu\n"
10998 "nr_bursts %d\n"
10999 "burst_usec %llu\n",
11000 cfs_b->nr_periods, cfs_b->nr_throttled,
11001 throttled_usec, cfs_b->nr_burst, burst_usec);
11002 }
11003 #endif
11004 return 0;
11005 }
11006
11007 #ifdef CONFIG_FAIR_GROUP_SCHED
cpu_weight_read_u64(struct cgroup_subsys_state * css,struct cftype * cft)11008 static u64 cpu_weight_read_u64(struct cgroup_subsys_state *css,
11009 struct cftype *cft)
11010 {
11011 struct task_group *tg = css_tg(css);
11012 u64 weight = scale_load_down(tg->shares);
11013
11014 return DIV_ROUND_CLOSEST_ULL(weight * CGROUP_WEIGHT_DFL, 1024);
11015 }
11016
cpu_weight_write_u64(struct cgroup_subsys_state * css,struct cftype * cft,u64 weight)11017 static int cpu_weight_write_u64(struct cgroup_subsys_state *css,
11018 struct cftype *cft, u64 weight)
11019 {
11020 /*
11021 * cgroup weight knobs should use the common MIN, DFL and MAX
11022 * values which are 1, 100 and 10000 respectively. While it loses
11023 * a bit of range on both ends, it maps pretty well onto the shares
11024 * value used by scheduler and the round-trip conversions preserve
11025 * the original value over the entire range.
11026 */
11027 if (weight < CGROUP_WEIGHT_MIN || weight > CGROUP_WEIGHT_MAX)
11028 return -ERANGE;
11029
11030 weight = DIV_ROUND_CLOSEST_ULL(weight * 1024, CGROUP_WEIGHT_DFL);
11031
11032 return sched_group_set_shares(css_tg(css), scale_load(weight));
11033 }
11034
cpu_weight_nice_read_s64(struct cgroup_subsys_state * css,struct cftype * cft)11035 static s64 cpu_weight_nice_read_s64(struct cgroup_subsys_state *css,
11036 struct cftype *cft)
11037 {
11038 unsigned long weight = scale_load_down(css_tg(css)->shares);
11039 int last_delta = INT_MAX;
11040 int prio, delta;
11041
11042 /* find the closest nice value to the current weight */
11043 for (prio = 0; prio < ARRAY_SIZE(sched_prio_to_weight); prio++) {
11044 delta = abs(sched_prio_to_weight[prio] - weight);
11045 if (delta >= last_delta)
11046 break;
11047 last_delta = delta;
11048 }
11049
11050 return PRIO_TO_NICE(prio - 1 + MAX_RT_PRIO);
11051 }
11052
cpu_weight_nice_write_s64(struct cgroup_subsys_state * css,struct cftype * cft,s64 nice)11053 static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css,
11054 struct cftype *cft, s64 nice)
11055 {
11056 unsigned long weight;
11057 int idx;
11058
11059 if (nice < MIN_NICE || nice > MAX_NICE)
11060 return -ERANGE;
11061
11062 idx = NICE_TO_PRIO(nice) - MAX_RT_PRIO;
11063 idx = array_index_nospec(idx, 40);
11064 weight = sched_prio_to_weight[idx];
11065
11066 return sched_group_set_shares(css_tg(css), scale_load(weight));
11067 }
11068 #endif
11069
cpu_period_quota_print(struct seq_file * sf,long period,long quota)11070 static void __maybe_unused cpu_period_quota_print(struct seq_file *sf,
11071 long period, long quota)
11072 {
11073 if (quota < 0)
11074 seq_puts(sf, "max");
11075 else
11076 seq_printf(sf, "%ld", quota);
11077
11078 seq_printf(sf, " %ld\n", period);
11079 }
11080
11081 /* caller should put the current value in *@periodp before calling */
cpu_period_quota_parse(char * buf,u64 * periodp,u64 * quotap)11082 static int __maybe_unused cpu_period_quota_parse(char *buf,
11083 u64 *periodp, u64 *quotap)
11084 {
11085 char tok[21]; /* U64_MAX */
11086
11087 if (sscanf(buf, "%20s %llu", tok, periodp) < 1)
11088 return -EINVAL;
11089
11090 *periodp *= NSEC_PER_USEC;
11091
11092 if (sscanf(tok, "%llu", quotap))
11093 *quotap *= NSEC_PER_USEC;
11094 else if (!strcmp(tok, "max"))
11095 *quotap = RUNTIME_INF;
11096 else
11097 return -EINVAL;
11098
11099 return 0;
11100 }
11101
11102 #ifdef CONFIG_CFS_BANDWIDTH
cpu_max_show(struct seq_file * sf,void * v)11103 static int cpu_max_show(struct seq_file *sf, void *v)
11104 {
11105 struct task_group *tg = css_tg(seq_css(sf));
11106
11107 cpu_period_quota_print(sf, tg_get_cfs_period(tg), tg_get_cfs_quota(tg));
11108 return 0;
11109 }
11110
cpu_max_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)11111 static ssize_t cpu_max_write(struct kernfs_open_file *of,
11112 char *buf, size_t nbytes, loff_t off)
11113 {
11114 struct task_group *tg = css_tg(of_css(of));
11115 u64 period = tg_get_cfs_period(tg);
11116 u64 burst = tg_get_cfs_burst(tg);
11117 u64 quota;
11118 int ret;
11119
11120 ret = cpu_period_quota_parse(buf, &period, "a);
11121 if (!ret)
11122 ret = tg_set_cfs_bandwidth(tg, period, quota, burst);
11123 return ret ?: nbytes;
11124 }
11125 #endif
11126
11127 static struct cftype cpu_files[] = {
11128 #ifdef CONFIG_FAIR_GROUP_SCHED
11129 {
11130 .name = "weight",
11131 .flags = CFTYPE_NOT_ON_ROOT,
11132 .read_u64 = cpu_weight_read_u64,
11133 .write_u64 = cpu_weight_write_u64,
11134 },
11135 {
11136 .name = "weight.nice",
11137 .flags = CFTYPE_NOT_ON_ROOT,
11138 .read_s64 = cpu_weight_nice_read_s64,
11139 .write_s64 = cpu_weight_nice_write_s64,
11140 },
11141 {
11142 .name = "idle",
11143 .flags = CFTYPE_NOT_ON_ROOT,
11144 .read_s64 = cpu_idle_read_s64,
11145 .write_s64 = cpu_idle_write_s64,
11146 },
11147 #endif
11148 #ifdef CONFIG_CFS_BANDWIDTH
11149 {
11150 .name = "max",
11151 .flags = CFTYPE_NOT_ON_ROOT,
11152 .seq_show = cpu_max_show,
11153 .write = cpu_max_write,
11154 },
11155 {
11156 .name = "max.burst",
11157 .flags = CFTYPE_NOT_ON_ROOT,
11158 .read_u64 = cpu_cfs_burst_read_u64,
11159 .write_u64 = cpu_cfs_burst_write_u64,
11160 },
11161 #endif
11162 #ifdef CONFIG_UCLAMP_TASK_GROUP
11163 {
11164 .name = "uclamp.min",
11165 .flags = CFTYPE_NOT_ON_ROOT,
11166 .seq_show = cpu_uclamp_min_show,
11167 .write = cpu_uclamp_min_write,
11168 },
11169 {
11170 .name = "uclamp.max",
11171 .flags = CFTYPE_NOT_ON_ROOT,
11172 .seq_show = cpu_uclamp_max_show,
11173 .write = cpu_uclamp_max_write,
11174 },
11175 #endif
11176 { } /* terminate */
11177 };
11178
11179 struct cgroup_subsys cpu_cgrp_subsys = {
11180 .css_alloc = cpu_cgroup_css_alloc,
11181 .css_online = cpu_cgroup_css_online,
11182 .css_released = cpu_cgroup_css_released,
11183 .css_free = cpu_cgroup_css_free,
11184 .css_extra_stat_show = cpu_extra_stat_show,
11185 #ifdef CONFIG_RT_GROUP_SCHED
11186 .can_attach = cpu_cgroup_can_attach,
11187 #endif
11188 .attach = cpu_cgroup_attach,
11189 .legacy_cftypes = cpu_legacy_files,
11190 .dfl_cftypes = cpu_files,
11191 .early_init = true,
11192 .threaded = true,
11193 };
11194
11195 #endif /* CONFIG_CGROUP_SCHED */
11196
dump_cpu_task(int cpu)11197 void dump_cpu_task(int cpu)
11198 {
11199 if (cpu == smp_processor_id() && in_hardirq()) {
11200 struct pt_regs *regs;
11201
11202 regs = get_irq_regs();
11203 if (regs) {
11204 show_regs(regs);
11205 return;
11206 }
11207 }
11208
11209 if (trigger_single_cpu_backtrace(cpu))
11210 return;
11211
11212 pr_info("Task dump for CPU %d:\n", cpu);
11213 sched_show_task(cpu_curr(cpu));
11214 }
11215
11216 /*
11217 * Nice levels are multiplicative, with a gentle 10% change for every
11218 * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
11219 * nice 1, it will get ~10% less CPU time than another CPU-bound task
11220 * that remained on nice 0.
11221 *
11222 * The "10% effect" is relative and cumulative: from _any_ nice level,
11223 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
11224 * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
11225 * If a task goes up by ~10% and another task goes down by ~10% then
11226 * the relative distance between them is ~25%.)
11227 */
11228 const int sched_prio_to_weight[40] = {
11229 /* -20 */ 88761, 71755, 56483, 46273, 36291,
11230 /* -15 */ 29154, 23254, 18705, 14949, 11916,
11231 /* -10 */ 9548, 7620, 6100, 4904, 3906,
11232 /* -5 */ 3121, 2501, 1991, 1586, 1277,
11233 /* 0 */ 1024, 820, 655, 526, 423,
11234 /* 5 */ 335, 272, 215, 172, 137,
11235 /* 10 */ 110, 87, 70, 56, 45,
11236 /* 15 */ 36, 29, 23, 18, 15,
11237 };
11238
11239 /*
11240 * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
11241 *
11242 * In cases where the weight does not change often, we can use the
11243 * precalculated inverse to speed up arithmetics by turning divisions
11244 * into multiplications:
11245 */
11246 const u32 sched_prio_to_wmult[40] = {
11247 /* -20 */ 48388, 59856, 76040, 92818, 118348,
11248 /* -15 */ 147320, 184698, 229616, 287308, 360437,
11249 /* -10 */ 449829, 563644, 704093, 875809, 1099582,
11250 /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
11251 /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
11252 /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
11253 /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
11254 /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
11255 };
11256
call_trace_sched_update_nr_running(struct rq * rq,int count)11257 void call_trace_sched_update_nr_running(struct rq *rq, int count)
11258 {
11259 trace_sched_update_nr_running_tp(rq, count);
11260 }
11261