1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
4 * policies)
5 */
6
7 int sched_rr_timeslice = RR_TIMESLICE;
8 /* More than 4 hours if BW_SHIFT equals 20. */
9 static const u64 max_rt_runtime = MAX_BW;
10
11 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun);
12
13 struct rt_bandwidth def_rt_bandwidth;
14
15 /*
16 * period over which we measure -rt task CPU usage in us.
17 * default: 1s
18 */
19 unsigned int sysctl_sched_rt_period = 1000000;
20
21 /*
22 * part of the period that we allow rt tasks to run in us.
23 * default: 0.95s
24 */
25 int sysctl_sched_rt_runtime = 950000;
26
27 #ifdef CONFIG_SYSCTL
28 static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;
29 static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
30 size_t *lenp, loff_t *ppos);
31 static int sched_rr_handler(struct ctl_table *table, int write, void *buffer,
32 size_t *lenp, loff_t *ppos);
33 static struct ctl_table sched_rt_sysctls[] = {
34 {
35 .procname = "sched_rt_period_us",
36 .data = &sysctl_sched_rt_period,
37 .maxlen = sizeof(unsigned int),
38 .mode = 0644,
39 .proc_handler = sched_rt_handler,
40 },
41 {
42 .procname = "sched_rt_runtime_us",
43 .data = &sysctl_sched_rt_runtime,
44 .maxlen = sizeof(int),
45 .mode = 0644,
46 .proc_handler = sched_rt_handler,
47 },
48 {
49 .procname = "sched_rr_timeslice_ms",
50 .data = &sysctl_sched_rr_timeslice,
51 .maxlen = sizeof(int),
52 .mode = 0644,
53 .proc_handler = sched_rr_handler,
54 },
55 {}
56 };
57
sched_rt_sysctl_init(void)58 static int __init sched_rt_sysctl_init(void)
59 {
60 register_sysctl_init("kernel", sched_rt_sysctls);
61 return 0;
62 }
63 late_initcall(sched_rt_sysctl_init);
64 #endif
65
sched_rt_period_timer(struct hrtimer * timer)66 static enum hrtimer_restart sched_rt_period_timer(struct hrtimer *timer)
67 {
68 struct rt_bandwidth *rt_b =
69 container_of(timer, struct rt_bandwidth, rt_period_timer);
70 int idle = 0;
71 int overrun;
72
73 raw_spin_lock(&rt_b->rt_runtime_lock);
74 for (;;) {
75 overrun = hrtimer_forward_now(timer, rt_b->rt_period);
76 if (!overrun)
77 break;
78
79 raw_spin_unlock(&rt_b->rt_runtime_lock);
80 idle = do_sched_rt_period_timer(rt_b, overrun);
81 raw_spin_lock(&rt_b->rt_runtime_lock);
82 }
83 if (idle)
84 rt_b->rt_period_active = 0;
85 raw_spin_unlock(&rt_b->rt_runtime_lock);
86
87 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
88 }
89
init_rt_bandwidth(struct rt_bandwidth * rt_b,u64 period,u64 runtime)90 void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
91 {
92 rt_b->rt_period = ns_to_ktime(period);
93 rt_b->rt_runtime = runtime;
94
95 raw_spin_lock_init(&rt_b->rt_runtime_lock);
96
97 hrtimer_init(&rt_b->rt_period_timer, CLOCK_MONOTONIC,
98 HRTIMER_MODE_REL_HARD);
99 rt_b->rt_period_timer.function = sched_rt_period_timer;
100 }
101
do_start_rt_bandwidth(struct rt_bandwidth * rt_b)102 static inline void do_start_rt_bandwidth(struct rt_bandwidth *rt_b)
103 {
104 raw_spin_lock(&rt_b->rt_runtime_lock);
105 if (!rt_b->rt_period_active) {
106 rt_b->rt_period_active = 1;
107 /*
108 * SCHED_DEADLINE updates the bandwidth, as a run away
109 * RT task with a DL task could hog a CPU. But DL does
110 * not reset the period. If a deadline task was running
111 * without an RT task running, it can cause RT tasks to
112 * throttle when they start up. Kick the timer right away
113 * to update the period.
114 */
115 hrtimer_forward_now(&rt_b->rt_period_timer, ns_to_ktime(0));
116 hrtimer_start_expires(&rt_b->rt_period_timer,
117 HRTIMER_MODE_ABS_PINNED_HARD);
118 }
119 raw_spin_unlock(&rt_b->rt_runtime_lock);
120 }
121
start_rt_bandwidth(struct rt_bandwidth * rt_b)122 static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
123 {
124 if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
125 return;
126
127 do_start_rt_bandwidth(rt_b);
128 }
129
init_rt_rq(struct rt_rq * rt_rq)130 void init_rt_rq(struct rt_rq *rt_rq)
131 {
132 struct rt_prio_array *array;
133 int i;
134
135 array = &rt_rq->active;
136 for (i = 0; i < MAX_RT_PRIO; i++) {
137 INIT_LIST_HEAD(array->queue + i);
138 __clear_bit(i, array->bitmap);
139 }
140 /* delimiter for bitsearch: */
141 __set_bit(MAX_RT_PRIO, array->bitmap);
142
143 #if defined CONFIG_SMP
144 rt_rq->highest_prio.curr = MAX_RT_PRIO-1;
145 rt_rq->highest_prio.next = MAX_RT_PRIO-1;
146 rt_rq->rt_nr_migratory = 0;
147 rt_rq->overloaded = 0;
148 plist_head_init(&rt_rq->pushable_tasks);
149 #endif /* CONFIG_SMP */
150 /* We start is dequeued state, because no RT tasks are queued */
151 rt_rq->rt_queued = 0;
152
153 rt_rq->rt_time = 0;
154 rt_rq->rt_throttled = 0;
155 rt_rq->rt_runtime = 0;
156 raw_spin_lock_init(&rt_rq->rt_runtime_lock);
157 }
158
159 #ifdef CONFIG_RT_GROUP_SCHED
destroy_rt_bandwidth(struct rt_bandwidth * rt_b)160 static void destroy_rt_bandwidth(struct rt_bandwidth *rt_b)
161 {
162 hrtimer_cancel(&rt_b->rt_period_timer);
163 }
164
165 #define rt_entity_is_task(rt_se) (!(rt_se)->my_q)
166
rt_task_of(struct sched_rt_entity * rt_se)167 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
168 {
169 #ifdef CONFIG_SCHED_DEBUG
170 WARN_ON_ONCE(!rt_entity_is_task(rt_se));
171 #endif
172 return container_of(rt_se, struct task_struct, rt);
173 }
174
rq_of_rt_rq(struct rt_rq * rt_rq)175 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
176 {
177 return rt_rq->rq;
178 }
179
rt_rq_of_se(struct sched_rt_entity * rt_se)180 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
181 {
182 return rt_se->rt_rq;
183 }
184
rq_of_rt_se(struct sched_rt_entity * rt_se)185 static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
186 {
187 struct rt_rq *rt_rq = rt_se->rt_rq;
188
189 return rt_rq->rq;
190 }
191
unregister_rt_sched_group(struct task_group * tg)192 void unregister_rt_sched_group(struct task_group *tg)
193 {
194 if (tg->rt_se)
195 destroy_rt_bandwidth(&tg->rt_bandwidth);
196
197 }
198
free_rt_sched_group(struct task_group * tg)199 void free_rt_sched_group(struct task_group *tg)
200 {
201 int i;
202
203 for_each_possible_cpu(i) {
204 if (tg->rt_rq)
205 kfree(tg->rt_rq[i]);
206 if (tg->rt_se)
207 kfree(tg->rt_se[i]);
208 }
209
210 kfree(tg->rt_rq);
211 kfree(tg->rt_se);
212 }
213
init_tg_rt_entry(struct task_group * tg,struct rt_rq * rt_rq,struct sched_rt_entity * rt_se,int cpu,struct sched_rt_entity * parent)214 void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
215 struct sched_rt_entity *rt_se, int cpu,
216 struct sched_rt_entity *parent)
217 {
218 struct rq *rq = cpu_rq(cpu);
219
220 rt_rq->highest_prio.curr = MAX_RT_PRIO-1;
221 rt_rq->rt_nr_boosted = 0;
222 rt_rq->rq = rq;
223 rt_rq->tg = tg;
224
225 tg->rt_rq[cpu] = rt_rq;
226 tg->rt_se[cpu] = rt_se;
227
228 if (!rt_se)
229 return;
230
231 if (!parent)
232 rt_se->rt_rq = &rq->rt;
233 else
234 rt_se->rt_rq = parent->my_q;
235
236 rt_se->my_q = rt_rq;
237 rt_se->parent = parent;
238 INIT_LIST_HEAD(&rt_se->run_list);
239 }
240
alloc_rt_sched_group(struct task_group * tg,struct task_group * parent)241 int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
242 {
243 struct rt_rq *rt_rq;
244 struct sched_rt_entity *rt_se;
245 int i;
246
247 tg->rt_rq = kcalloc(nr_cpu_ids, sizeof(rt_rq), GFP_KERNEL);
248 if (!tg->rt_rq)
249 goto err;
250 tg->rt_se = kcalloc(nr_cpu_ids, sizeof(rt_se), GFP_KERNEL);
251 if (!tg->rt_se)
252 goto err;
253
254 init_rt_bandwidth(&tg->rt_bandwidth,
255 ktime_to_ns(def_rt_bandwidth.rt_period), 0);
256
257 for_each_possible_cpu(i) {
258 rt_rq = kzalloc_node(sizeof(struct rt_rq),
259 GFP_KERNEL, cpu_to_node(i));
260 if (!rt_rq)
261 goto err;
262
263 rt_se = kzalloc_node(sizeof(struct sched_rt_entity),
264 GFP_KERNEL, cpu_to_node(i));
265 if (!rt_se)
266 goto err_free_rq;
267
268 init_rt_rq(rt_rq);
269 rt_rq->rt_runtime = tg->rt_bandwidth.rt_runtime;
270 init_tg_rt_entry(tg, rt_rq, rt_se, i, parent->rt_se[i]);
271 }
272
273 return 1;
274
275 err_free_rq:
276 kfree(rt_rq);
277 err:
278 return 0;
279 }
280
281 #else /* CONFIG_RT_GROUP_SCHED */
282
283 #define rt_entity_is_task(rt_se) (1)
284
rt_task_of(struct sched_rt_entity * rt_se)285 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
286 {
287 return container_of(rt_se, struct task_struct, rt);
288 }
289
rq_of_rt_rq(struct rt_rq * rt_rq)290 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
291 {
292 return container_of(rt_rq, struct rq, rt);
293 }
294
rq_of_rt_se(struct sched_rt_entity * rt_se)295 static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
296 {
297 struct task_struct *p = rt_task_of(rt_se);
298
299 return task_rq(p);
300 }
301
rt_rq_of_se(struct sched_rt_entity * rt_se)302 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
303 {
304 struct rq *rq = rq_of_rt_se(rt_se);
305
306 return &rq->rt;
307 }
308
unregister_rt_sched_group(struct task_group * tg)309 void unregister_rt_sched_group(struct task_group *tg) { }
310
free_rt_sched_group(struct task_group * tg)311 void free_rt_sched_group(struct task_group *tg) { }
312
alloc_rt_sched_group(struct task_group * tg,struct task_group * parent)313 int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
314 {
315 return 1;
316 }
317 #endif /* CONFIG_RT_GROUP_SCHED */
318
319 #ifdef CONFIG_SMP
320
need_pull_rt_task(struct rq * rq,struct task_struct * prev)321 static inline bool need_pull_rt_task(struct rq *rq, struct task_struct *prev)
322 {
323 /* Try to pull RT tasks here if we lower this rq's prio */
324 return rq->online && rq->rt.highest_prio.curr > prev->prio;
325 }
326
rt_overloaded(struct rq * rq)327 static inline int rt_overloaded(struct rq *rq)
328 {
329 return atomic_read(&rq->rd->rto_count);
330 }
331
rt_set_overload(struct rq * rq)332 static inline void rt_set_overload(struct rq *rq)
333 {
334 if (!rq->online)
335 return;
336
337 cpumask_set_cpu(rq->cpu, rq->rd->rto_mask);
338 /*
339 * Make sure the mask is visible before we set
340 * the overload count. That is checked to determine
341 * if we should look at the mask. It would be a shame
342 * if we looked at the mask, but the mask was not
343 * updated yet.
344 *
345 * Matched by the barrier in pull_rt_task().
346 */
347 smp_wmb();
348 atomic_inc(&rq->rd->rto_count);
349 }
350
rt_clear_overload(struct rq * rq)351 static inline void rt_clear_overload(struct rq *rq)
352 {
353 if (!rq->online)
354 return;
355
356 /* the order here really doesn't matter */
357 atomic_dec(&rq->rd->rto_count);
358 cpumask_clear_cpu(rq->cpu, rq->rd->rto_mask);
359 }
360
update_rt_migration(struct rt_rq * rt_rq)361 static void update_rt_migration(struct rt_rq *rt_rq)
362 {
363 if (rt_rq->rt_nr_migratory && rt_rq->rt_nr_total > 1) {
364 if (!rt_rq->overloaded) {
365 rt_set_overload(rq_of_rt_rq(rt_rq));
366 rt_rq->overloaded = 1;
367 }
368 } else if (rt_rq->overloaded) {
369 rt_clear_overload(rq_of_rt_rq(rt_rq));
370 rt_rq->overloaded = 0;
371 }
372 }
373
inc_rt_migration(struct sched_rt_entity * rt_se,struct rt_rq * rt_rq)374 static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
375 {
376 struct task_struct *p;
377
378 if (!rt_entity_is_task(rt_se))
379 return;
380
381 p = rt_task_of(rt_se);
382 rt_rq = &rq_of_rt_rq(rt_rq)->rt;
383
384 rt_rq->rt_nr_total++;
385 if (p->nr_cpus_allowed > 1)
386 rt_rq->rt_nr_migratory++;
387
388 update_rt_migration(rt_rq);
389 }
390
dec_rt_migration(struct sched_rt_entity * rt_se,struct rt_rq * rt_rq)391 static void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
392 {
393 struct task_struct *p;
394
395 if (!rt_entity_is_task(rt_se))
396 return;
397
398 p = rt_task_of(rt_se);
399 rt_rq = &rq_of_rt_rq(rt_rq)->rt;
400
401 rt_rq->rt_nr_total--;
402 if (p->nr_cpus_allowed > 1)
403 rt_rq->rt_nr_migratory--;
404
405 update_rt_migration(rt_rq);
406 }
407
has_pushable_tasks(struct rq * rq)408 static inline int has_pushable_tasks(struct rq *rq)
409 {
410 return !plist_head_empty(&rq->rt.pushable_tasks);
411 }
412
413 static DEFINE_PER_CPU(struct balance_callback, rt_push_head);
414 static DEFINE_PER_CPU(struct balance_callback, rt_pull_head);
415
416 static void push_rt_tasks(struct rq *);
417 static void pull_rt_task(struct rq *);
418
rt_queue_push_tasks(struct rq * rq)419 static inline void rt_queue_push_tasks(struct rq *rq)
420 {
421 if (!has_pushable_tasks(rq))
422 return;
423
424 queue_balance_callback(rq, &per_cpu(rt_push_head, rq->cpu), push_rt_tasks);
425 }
426
rt_queue_pull_task(struct rq * rq)427 static inline void rt_queue_pull_task(struct rq *rq)
428 {
429 queue_balance_callback(rq, &per_cpu(rt_pull_head, rq->cpu), pull_rt_task);
430 }
431
enqueue_pushable_task(struct rq * rq,struct task_struct * p)432 static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
433 {
434 plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
435 plist_node_init(&p->pushable_tasks, p->prio);
436 plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
437
438 /* Update the highest prio pushable task */
439 if (p->prio < rq->rt.highest_prio.next)
440 rq->rt.highest_prio.next = p->prio;
441 }
442
dequeue_pushable_task(struct rq * rq,struct task_struct * p)443 static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
444 {
445 plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
446
447 /* Update the new highest prio pushable task */
448 if (has_pushable_tasks(rq)) {
449 p = plist_first_entry(&rq->rt.pushable_tasks,
450 struct task_struct, pushable_tasks);
451 rq->rt.highest_prio.next = p->prio;
452 } else {
453 rq->rt.highest_prio.next = MAX_RT_PRIO-1;
454 }
455 }
456
457 #else
458
enqueue_pushable_task(struct rq * rq,struct task_struct * p)459 static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
460 {
461 }
462
dequeue_pushable_task(struct rq * rq,struct task_struct * p)463 static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
464 {
465 }
466
467 static inline
inc_rt_migration(struct sched_rt_entity * rt_se,struct rt_rq * rt_rq)468 void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
469 {
470 }
471
472 static inline
dec_rt_migration(struct sched_rt_entity * rt_se,struct rt_rq * rt_rq)473 void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
474 {
475 }
476
rt_queue_push_tasks(struct rq * rq)477 static inline void rt_queue_push_tasks(struct rq *rq)
478 {
479 }
480 #endif /* CONFIG_SMP */
481
482 static void enqueue_top_rt_rq(struct rt_rq *rt_rq);
483 static void dequeue_top_rt_rq(struct rt_rq *rt_rq, unsigned int count);
484
on_rt_rq(struct sched_rt_entity * rt_se)485 static inline int on_rt_rq(struct sched_rt_entity *rt_se)
486 {
487 return rt_se->on_rq;
488 }
489
490 #ifdef CONFIG_UCLAMP_TASK
491 /*
492 * Verify the fitness of task @p to run on @cpu taking into account the uclamp
493 * settings.
494 *
495 * This check is only important for heterogeneous systems where uclamp_min value
496 * is higher than the capacity of a @cpu. For non-heterogeneous system this
497 * function will always return true.
498 *
499 * The function will return true if the capacity of the @cpu is >= the
500 * uclamp_min and false otherwise.
501 *
502 * Note that uclamp_min will be clamped to uclamp_max if uclamp_min
503 * > uclamp_max.
504 */
rt_task_fits_capacity(struct task_struct * p,int cpu)505 static inline bool rt_task_fits_capacity(struct task_struct *p, int cpu)
506 {
507 unsigned int min_cap;
508 unsigned int max_cap;
509 unsigned int cpu_cap;
510
511 /* Only heterogeneous systems can benefit from this check */
512 if (!sched_asym_cpucap_active())
513 return true;
514
515 min_cap = uclamp_eff_value(p, UCLAMP_MIN);
516 max_cap = uclamp_eff_value(p, UCLAMP_MAX);
517
518 cpu_cap = capacity_orig_of(cpu);
519
520 return cpu_cap >= min(min_cap, max_cap);
521 }
522 #else
rt_task_fits_capacity(struct task_struct * p,int cpu)523 static inline bool rt_task_fits_capacity(struct task_struct *p, int cpu)
524 {
525 return true;
526 }
527 #endif
528
529 #ifdef CONFIG_RT_GROUP_SCHED
530
sched_rt_runtime(struct rt_rq * rt_rq)531 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
532 {
533 if (!rt_rq->tg)
534 return RUNTIME_INF;
535
536 return rt_rq->rt_runtime;
537 }
538
sched_rt_period(struct rt_rq * rt_rq)539 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
540 {
541 return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
542 }
543
544 typedef struct task_group *rt_rq_iter_t;
545
next_task_group(struct task_group * tg)546 static inline struct task_group *next_task_group(struct task_group *tg)
547 {
548 do {
549 tg = list_entry_rcu(tg->list.next,
550 typeof(struct task_group), list);
551 } while (&tg->list != &task_groups && task_group_is_autogroup(tg));
552
553 if (&tg->list == &task_groups)
554 tg = NULL;
555
556 return tg;
557 }
558
559 #define for_each_rt_rq(rt_rq, iter, rq) \
560 for (iter = container_of(&task_groups, typeof(*iter), list); \
561 (iter = next_task_group(iter)) && \
562 (rt_rq = iter->rt_rq[cpu_of(rq)]);)
563
564 #define for_each_sched_rt_entity(rt_se) \
565 for (; rt_se; rt_se = rt_se->parent)
566
group_rt_rq(struct sched_rt_entity * rt_se)567 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
568 {
569 return rt_se->my_q;
570 }
571
572 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags);
573 static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags);
574
sched_rt_rq_enqueue(struct rt_rq * rt_rq)575 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
576 {
577 struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
578 struct rq *rq = rq_of_rt_rq(rt_rq);
579 struct sched_rt_entity *rt_se;
580
581 int cpu = cpu_of(rq);
582
583 rt_se = rt_rq->tg->rt_se[cpu];
584
585 if (rt_rq->rt_nr_running) {
586 if (!rt_se)
587 enqueue_top_rt_rq(rt_rq);
588 else if (!on_rt_rq(rt_se))
589 enqueue_rt_entity(rt_se, 0);
590
591 if (rt_rq->highest_prio.curr < curr->prio)
592 resched_curr(rq);
593 }
594 }
595
sched_rt_rq_dequeue(struct rt_rq * rt_rq)596 static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
597 {
598 struct sched_rt_entity *rt_se;
599 int cpu = cpu_of(rq_of_rt_rq(rt_rq));
600
601 rt_se = rt_rq->tg->rt_se[cpu];
602
603 if (!rt_se) {
604 dequeue_top_rt_rq(rt_rq, rt_rq->rt_nr_running);
605 /* Kick cpufreq (see the comment in kernel/sched/sched.h). */
606 cpufreq_update_util(rq_of_rt_rq(rt_rq), 0);
607 }
608 else if (on_rt_rq(rt_se))
609 dequeue_rt_entity(rt_se, 0);
610 }
611
rt_rq_throttled(struct rt_rq * rt_rq)612 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
613 {
614 return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
615 }
616
rt_se_boosted(struct sched_rt_entity * rt_se)617 static int rt_se_boosted(struct sched_rt_entity *rt_se)
618 {
619 struct rt_rq *rt_rq = group_rt_rq(rt_se);
620 struct task_struct *p;
621
622 if (rt_rq)
623 return !!rt_rq->rt_nr_boosted;
624
625 p = rt_task_of(rt_se);
626 return p->prio != p->normal_prio;
627 }
628
629 #ifdef CONFIG_SMP
sched_rt_period_mask(void)630 static inline const struct cpumask *sched_rt_period_mask(void)
631 {
632 return this_rq()->rd->span;
633 }
634 #else
sched_rt_period_mask(void)635 static inline const struct cpumask *sched_rt_period_mask(void)
636 {
637 return cpu_online_mask;
638 }
639 #endif
640
641 static inline
sched_rt_period_rt_rq(struct rt_bandwidth * rt_b,int cpu)642 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
643 {
644 return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
645 }
646
sched_rt_bandwidth(struct rt_rq * rt_rq)647 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
648 {
649 return &rt_rq->tg->rt_bandwidth;
650 }
651
652 #else /* !CONFIG_RT_GROUP_SCHED */
653
sched_rt_runtime(struct rt_rq * rt_rq)654 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
655 {
656 return rt_rq->rt_runtime;
657 }
658
sched_rt_period(struct rt_rq * rt_rq)659 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
660 {
661 return ktime_to_ns(def_rt_bandwidth.rt_period);
662 }
663
664 typedef struct rt_rq *rt_rq_iter_t;
665
666 #define for_each_rt_rq(rt_rq, iter, rq) \
667 for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
668
669 #define for_each_sched_rt_entity(rt_se) \
670 for (; rt_se; rt_se = NULL)
671
group_rt_rq(struct sched_rt_entity * rt_se)672 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
673 {
674 return NULL;
675 }
676
sched_rt_rq_enqueue(struct rt_rq * rt_rq)677 static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
678 {
679 struct rq *rq = rq_of_rt_rq(rt_rq);
680
681 if (!rt_rq->rt_nr_running)
682 return;
683
684 enqueue_top_rt_rq(rt_rq);
685 resched_curr(rq);
686 }
687
sched_rt_rq_dequeue(struct rt_rq * rt_rq)688 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
689 {
690 dequeue_top_rt_rq(rt_rq, rt_rq->rt_nr_running);
691 }
692
rt_rq_throttled(struct rt_rq * rt_rq)693 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
694 {
695 return rt_rq->rt_throttled;
696 }
697
sched_rt_period_mask(void)698 static inline const struct cpumask *sched_rt_period_mask(void)
699 {
700 return cpu_online_mask;
701 }
702
703 static inline
sched_rt_period_rt_rq(struct rt_bandwidth * rt_b,int cpu)704 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
705 {
706 return &cpu_rq(cpu)->rt;
707 }
708
sched_rt_bandwidth(struct rt_rq * rt_rq)709 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
710 {
711 return &def_rt_bandwidth;
712 }
713
714 #endif /* CONFIG_RT_GROUP_SCHED */
715
sched_rt_bandwidth_account(struct rt_rq * rt_rq)716 bool sched_rt_bandwidth_account(struct rt_rq *rt_rq)
717 {
718 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
719
720 return (hrtimer_active(&rt_b->rt_period_timer) ||
721 rt_rq->rt_time < rt_b->rt_runtime);
722 }
723
724 #ifdef CONFIG_SMP
725 /*
726 * We ran out of runtime, see if we can borrow some from our neighbours.
727 */
do_balance_runtime(struct rt_rq * rt_rq)728 static void do_balance_runtime(struct rt_rq *rt_rq)
729 {
730 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
731 struct root_domain *rd = rq_of_rt_rq(rt_rq)->rd;
732 int i, weight;
733 u64 rt_period;
734
735 weight = cpumask_weight(rd->span);
736
737 raw_spin_lock(&rt_b->rt_runtime_lock);
738 rt_period = ktime_to_ns(rt_b->rt_period);
739 for_each_cpu(i, rd->span) {
740 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
741 s64 diff;
742
743 if (iter == rt_rq)
744 continue;
745
746 raw_spin_lock(&iter->rt_runtime_lock);
747 /*
748 * Either all rqs have inf runtime and there's nothing to steal
749 * or __disable_runtime() below sets a specific rq to inf to
750 * indicate its been disabled and disallow stealing.
751 */
752 if (iter->rt_runtime == RUNTIME_INF)
753 goto next;
754
755 /*
756 * From runqueues with spare time, take 1/n part of their
757 * spare time, but no more than our period.
758 */
759 diff = iter->rt_runtime - iter->rt_time;
760 if (diff > 0) {
761 diff = div_u64((u64)diff, weight);
762 if (rt_rq->rt_runtime + diff > rt_period)
763 diff = rt_period - rt_rq->rt_runtime;
764 iter->rt_runtime -= diff;
765 rt_rq->rt_runtime += diff;
766 if (rt_rq->rt_runtime == rt_period) {
767 raw_spin_unlock(&iter->rt_runtime_lock);
768 break;
769 }
770 }
771 next:
772 raw_spin_unlock(&iter->rt_runtime_lock);
773 }
774 raw_spin_unlock(&rt_b->rt_runtime_lock);
775 }
776
777 /*
778 * Ensure this RQ takes back all the runtime it lend to its neighbours.
779 */
__disable_runtime(struct rq * rq)780 static void __disable_runtime(struct rq *rq)
781 {
782 struct root_domain *rd = rq->rd;
783 rt_rq_iter_t iter;
784 struct rt_rq *rt_rq;
785
786 if (unlikely(!scheduler_running))
787 return;
788
789 for_each_rt_rq(rt_rq, iter, rq) {
790 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
791 s64 want;
792 int i;
793
794 raw_spin_lock(&rt_b->rt_runtime_lock);
795 raw_spin_lock(&rt_rq->rt_runtime_lock);
796 /*
797 * Either we're all inf and nobody needs to borrow, or we're
798 * already disabled and thus have nothing to do, or we have
799 * exactly the right amount of runtime to take out.
800 */
801 if (rt_rq->rt_runtime == RUNTIME_INF ||
802 rt_rq->rt_runtime == rt_b->rt_runtime)
803 goto balanced;
804 raw_spin_unlock(&rt_rq->rt_runtime_lock);
805
806 /*
807 * Calculate the difference between what we started out with
808 * and what we current have, that's the amount of runtime
809 * we lend and now have to reclaim.
810 */
811 want = rt_b->rt_runtime - rt_rq->rt_runtime;
812
813 /*
814 * Greedy reclaim, take back as much as we can.
815 */
816 for_each_cpu(i, rd->span) {
817 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
818 s64 diff;
819
820 /*
821 * Can't reclaim from ourselves or disabled runqueues.
822 */
823 if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
824 continue;
825
826 raw_spin_lock(&iter->rt_runtime_lock);
827 if (want > 0) {
828 diff = min_t(s64, iter->rt_runtime, want);
829 iter->rt_runtime -= diff;
830 want -= diff;
831 } else {
832 iter->rt_runtime -= want;
833 want -= want;
834 }
835 raw_spin_unlock(&iter->rt_runtime_lock);
836
837 if (!want)
838 break;
839 }
840
841 raw_spin_lock(&rt_rq->rt_runtime_lock);
842 /*
843 * We cannot be left wanting - that would mean some runtime
844 * leaked out of the system.
845 */
846 WARN_ON_ONCE(want);
847 balanced:
848 /*
849 * Disable all the borrow logic by pretending we have inf
850 * runtime - in which case borrowing doesn't make sense.
851 */
852 rt_rq->rt_runtime = RUNTIME_INF;
853 rt_rq->rt_throttled = 0;
854 raw_spin_unlock(&rt_rq->rt_runtime_lock);
855 raw_spin_unlock(&rt_b->rt_runtime_lock);
856
857 /* Make rt_rq available for pick_next_task() */
858 sched_rt_rq_enqueue(rt_rq);
859 }
860 }
861
__enable_runtime(struct rq * rq)862 static void __enable_runtime(struct rq *rq)
863 {
864 rt_rq_iter_t iter;
865 struct rt_rq *rt_rq;
866
867 if (unlikely(!scheduler_running))
868 return;
869
870 /*
871 * Reset each runqueue's bandwidth settings
872 */
873 for_each_rt_rq(rt_rq, iter, rq) {
874 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
875
876 raw_spin_lock(&rt_b->rt_runtime_lock);
877 raw_spin_lock(&rt_rq->rt_runtime_lock);
878 rt_rq->rt_runtime = rt_b->rt_runtime;
879 rt_rq->rt_time = 0;
880 rt_rq->rt_throttled = 0;
881 raw_spin_unlock(&rt_rq->rt_runtime_lock);
882 raw_spin_unlock(&rt_b->rt_runtime_lock);
883 }
884 }
885
balance_runtime(struct rt_rq * rt_rq)886 static void balance_runtime(struct rt_rq *rt_rq)
887 {
888 if (!sched_feat(RT_RUNTIME_SHARE))
889 return;
890
891 if (rt_rq->rt_time > rt_rq->rt_runtime) {
892 raw_spin_unlock(&rt_rq->rt_runtime_lock);
893 do_balance_runtime(rt_rq);
894 raw_spin_lock(&rt_rq->rt_runtime_lock);
895 }
896 }
897 #else /* !CONFIG_SMP */
balance_runtime(struct rt_rq * rt_rq)898 static inline void balance_runtime(struct rt_rq *rt_rq) {}
899 #endif /* CONFIG_SMP */
900
do_sched_rt_period_timer(struct rt_bandwidth * rt_b,int overrun)901 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
902 {
903 int i, idle = 1, throttled = 0;
904 const struct cpumask *span;
905
906 span = sched_rt_period_mask();
907 #ifdef CONFIG_RT_GROUP_SCHED
908 /*
909 * FIXME: isolated CPUs should really leave the root task group,
910 * whether they are isolcpus or were isolated via cpusets, lest
911 * the timer run on a CPU which does not service all runqueues,
912 * potentially leaving other CPUs indefinitely throttled. If
913 * isolation is really required, the user will turn the throttle
914 * off to kill the perturbations it causes anyway. Meanwhile,
915 * this maintains functionality for boot and/or troubleshooting.
916 */
917 if (rt_b == &root_task_group.rt_bandwidth)
918 span = cpu_online_mask;
919 #endif
920 for_each_cpu(i, span) {
921 int enqueue = 0;
922 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
923 struct rq *rq = rq_of_rt_rq(rt_rq);
924 struct rq_flags rf;
925 int skip;
926
927 /*
928 * When span == cpu_online_mask, taking each rq->lock
929 * can be time-consuming. Try to avoid it when possible.
930 */
931 raw_spin_lock(&rt_rq->rt_runtime_lock);
932 if (!sched_feat(RT_RUNTIME_SHARE) && rt_rq->rt_runtime != RUNTIME_INF)
933 rt_rq->rt_runtime = rt_b->rt_runtime;
934 skip = !rt_rq->rt_time && !rt_rq->rt_nr_running;
935 raw_spin_unlock(&rt_rq->rt_runtime_lock);
936 if (skip)
937 continue;
938
939 rq_lock(rq, &rf);
940 update_rq_clock(rq);
941
942 if (rt_rq->rt_time) {
943 u64 runtime;
944
945 raw_spin_lock(&rt_rq->rt_runtime_lock);
946 if (rt_rq->rt_throttled)
947 balance_runtime(rt_rq);
948 runtime = rt_rq->rt_runtime;
949 rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
950 if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
951 rt_rq->rt_throttled = 0;
952 enqueue = 1;
953
954 /*
955 * When we're idle and a woken (rt) task is
956 * throttled check_preempt_curr() will set
957 * skip_update and the time between the wakeup
958 * and this unthrottle will get accounted as
959 * 'runtime'.
960 */
961 if (rt_rq->rt_nr_running && rq->curr == rq->idle)
962 rq_clock_cancel_skipupdate(rq);
963 }
964 if (rt_rq->rt_time || rt_rq->rt_nr_running)
965 idle = 0;
966 raw_spin_unlock(&rt_rq->rt_runtime_lock);
967 } else if (rt_rq->rt_nr_running) {
968 idle = 0;
969 if (!rt_rq_throttled(rt_rq))
970 enqueue = 1;
971 }
972 if (rt_rq->rt_throttled)
973 throttled = 1;
974
975 if (enqueue)
976 sched_rt_rq_enqueue(rt_rq);
977 rq_unlock(rq, &rf);
978 }
979
980 if (!throttled && (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF))
981 return 1;
982
983 return idle;
984 }
985
rt_se_prio(struct sched_rt_entity * rt_se)986 static inline int rt_se_prio(struct sched_rt_entity *rt_se)
987 {
988 #ifdef CONFIG_RT_GROUP_SCHED
989 struct rt_rq *rt_rq = group_rt_rq(rt_se);
990
991 if (rt_rq)
992 return rt_rq->highest_prio.curr;
993 #endif
994
995 return rt_task_of(rt_se)->prio;
996 }
997
sched_rt_runtime_exceeded(struct rt_rq * rt_rq)998 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
999 {
1000 u64 runtime = sched_rt_runtime(rt_rq);
1001
1002 if (rt_rq->rt_throttled)
1003 return rt_rq_throttled(rt_rq);
1004
1005 if (runtime >= sched_rt_period(rt_rq))
1006 return 0;
1007
1008 balance_runtime(rt_rq);
1009 runtime = sched_rt_runtime(rt_rq);
1010 if (runtime == RUNTIME_INF)
1011 return 0;
1012
1013 if (rt_rq->rt_time > runtime) {
1014 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
1015
1016 /*
1017 * Don't actually throttle groups that have no runtime assigned
1018 * but accrue some time due to boosting.
1019 */
1020 if (likely(rt_b->rt_runtime)) {
1021 rt_rq->rt_throttled = 1;
1022 printk_deferred_once("sched: RT throttling activated\n");
1023 } else {
1024 /*
1025 * In case we did anyway, make it go away,
1026 * replenishment is a joke, since it will replenish us
1027 * with exactly 0 ns.
1028 */
1029 rt_rq->rt_time = 0;
1030 }
1031
1032 if (rt_rq_throttled(rt_rq)) {
1033 sched_rt_rq_dequeue(rt_rq);
1034 return 1;
1035 }
1036 }
1037
1038 return 0;
1039 }
1040
1041 /*
1042 * Update the current task's runtime statistics. Skip current tasks that
1043 * are not in our scheduling class.
1044 */
update_curr_rt(struct rq * rq)1045 static void update_curr_rt(struct rq *rq)
1046 {
1047 struct task_struct *curr = rq->curr;
1048 struct sched_rt_entity *rt_se = &curr->rt;
1049 u64 delta_exec;
1050 u64 now;
1051
1052 if (curr->sched_class != &rt_sched_class)
1053 return;
1054
1055 now = rq_clock_task(rq);
1056 delta_exec = now - curr->se.exec_start;
1057 if (unlikely((s64)delta_exec <= 0))
1058 return;
1059
1060 schedstat_set(curr->stats.exec_max,
1061 max(curr->stats.exec_max, delta_exec));
1062
1063 trace_sched_stat_runtime(curr, delta_exec, 0);
1064
1065 update_current_exec_runtime(curr, now, delta_exec);
1066
1067 if (!rt_bandwidth_enabled())
1068 return;
1069
1070 for_each_sched_rt_entity(rt_se) {
1071 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1072 int exceeded;
1073
1074 if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
1075 raw_spin_lock(&rt_rq->rt_runtime_lock);
1076 rt_rq->rt_time += delta_exec;
1077 exceeded = sched_rt_runtime_exceeded(rt_rq);
1078 if (exceeded)
1079 resched_curr(rq);
1080 raw_spin_unlock(&rt_rq->rt_runtime_lock);
1081 if (exceeded)
1082 do_start_rt_bandwidth(sched_rt_bandwidth(rt_rq));
1083 }
1084 }
1085 }
1086
1087 static void
dequeue_top_rt_rq(struct rt_rq * rt_rq,unsigned int count)1088 dequeue_top_rt_rq(struct rt_rq *rt_rq, unsigned int count)
1089 {
1090 struct rq *rq = rq_of_rt_rq(rt_rq);
1091
1092 BUG_ON(&rq->rt != rt_rq);
1093
1094 if (!rt_rq->rt_queued)
1095 return;
1096
1097 BUG_ON(!rq->nr_running);
1098
1099 sub_nr_running(rq, count);
1100 rt_rq->rt_queued = 0;
1101
1102 }
1103
1104 static void
enqueue_top_rt_rq(struct rt_rq * rt_rq)1105 enqueue_top_rt_rq(struct rt_rq *rt_rq)
1106 {
1107 struct rq *rq = rq_of_rt_rq(rt_rq);
1108
1109 BUG_ON(&rq->rt != rt_rq);
1110
1111 if (rt_rq->rt_queued)
1112 return;
1113
1114 if (rt_rq_throttled(rt_rq))
1115 return;
1116
1117 if (rt_rq->rt_nr_running) {
1118 add_nr_running(rq, rt_rq->rt_nr_running);
1119 rt_rq->rt_queued = 1;
1120 }
1121
1122 /* Kick cpufreq (see the comment in kernel/sched/sched.h). */
1123 cpufreq_update_util(rq, 0);
1124 }
1125
1126 #if defined CONFIG_SMP
1127
1128 static void
inc_rt_prio_smp(struct rt_rq * rt_rq,int prio,int prev_prio)1129 inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
1130 {
1131 struct rq *rq = rq_of_rt_rq(rt_rq);
1132
1133 #ifdef CONFIG_RT_GROUP_SCHED
1134 /*
1135 * Change rq's cpupri only if rt_rq is the top queue.
1136 */
1137 if (&rq->rt != rt_rq)
1138 return;
1139 #endif
1140 if (rq->online && prio < prev_prio)
1141 cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
1142 }
1143
1144 static void
dec_rt_prio_smp(struct rt_rq * rt_rq,int prio,int prev_prio)1145 dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
1146 {
1147 struct rq *rq = rq_of_rt_rq(rt_rq);
1148
1149 #ifdef CONFIG_RT_GROUP_SCHED
1150 /*
1151 * Change rq's cpupri only if rt_rq is the top queue.
1152 */
1153 if (&rq->rt != rt_rq)
1154 return;
1155 #endif
1156 if (rq->online && rt_rq->highest_prio.curr != prev_prio)
1157 cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
1158 }
1159
1160 #else /* CONFIG_SMP */
1161
1162 static inline
inc_rt_prio_smp(struct rt_rq * rt_rq,int prio,int prev_prio)1163 void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
1164 static inline
dec_rt_prio_smp(struct rt_rq * rt_rq,int prio,int prev_prio)1165 void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
1166
1167 #endif /* CONFIG_SMP */
1168
1169 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
1170 static void
inc_rt_prio(struct rt_rq * rt_rq,int prio)1171 inc_rt_prio(struct rt_rq *rt_rq, int prio)
1172 {
1173 int prev_prio = rt_rq->highest_prio.curr;
1174
1175 if (prio < prev_prio)
1176 rt_rq->highest_prio.curr = prio;
1177
1178 inc_rt_prio_smp(rt_rq, prio, prev_prio);
1179 }
1180
1181 static void
dec_rt_prio(struct rt_rq * rt_rq,int prio)1182 dec_rt_prio(struct rt_rq *rt_rq, int prio)
1183 {
1184 int prev_prio = rt_rq->highest_prio.curr;
1185
1186 if (rt_rq->rt_nr_running) {
1187
1188 WARN_ON(prio < prev_prio);
1189
1190 /*
1191 * This may have been our highest task, and therefore
1192 * we may have some recomputation to do
1193 */
1194 if (prio == prev_prio) {
1195 struct rt_prio_array *array = &rt_rq->active;
1196
1197 rt_rq->highest_prio.curr =
1198 sched_find_first_bit(array->bitmap);
1199 }
1200
1201 } else {
1202 rt_rq->highest_prio.curr = MAX_RT_PRIO-1;
1203 }
1204
1205 dec_rt_prio_smp(rt_rq, prio, prev_prio);
1206 }
1207
1208 #else
1209
inc_rt_prio(struct rt_rq * rt_rq,int prio)1210 static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
dec_rt_prio(struct rt_rq * rt_rq,int prio)1211 static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}
1212
1213 #endif /* CONFIG_SMP || CONFIG_RT_GROUP_SCHED */
1214
1215 #ifdef CONFIG_RT_GROUP_SCHED
1216
1217 static void
inc_rt_group(struct sched_rt_entity * rt_se,struct rt_rq * rt_rq)1218 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1219 {
1220 if (rt_se_boosted(rt_se))
1221 rt_rq->rt_nr_boosted++;
1222
1223 if (rt_rq->tg)
1224 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
1225 }
1226
1227 static void
dec_rt_group(struct sched_rt_entity * rt_se,struct rt_rq * rt_rq)1228 dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1229 {
1230 if (rt_se_boosted(rt_se))
1231 rt_rq->rt_nr_boosted--;
1232
1233 WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
1234 }
1235
1236 #else /* CONFIG_RT_GROUP_SCHED */
1237
1238 static void
inc_rt_group(struct sched_rt_entity * rt_se,struct rt_rq * rt_rq)1239 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1240 {
1241 start_rt_bandwidth(&def_rt_bandwidth);
1242 }
1243
1244 static inline
dec_rt_group(struct sched_rt_entity * rt_se,struct rt_rq * rt_rq)1245 void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}
1246
1247 #endif /* CONFIG_RT_GROUP_SCHED */
1248
1249 static inline
rt_se_nr_running(struct sched_rt_entity * rt_se)1250 unsigned int rt_se_nr_running(struct sched_rt_entity *rt_se)
1251 {
1252 struct rt_rq *group_rq = group_rt_rq(rt_se);
1253
1254 if (group_rq)
1255 return group_rq->rt_nr_running;
1256 else
1257 return 1;
1258 }
1259
1260 static inline
rt_se_rr_nr_running(struct sched_rt_entity * rt_se)1261 unsigned int rt_se_rr_nr_running(struct sched_rt_entity *rt_se)
1262 {
1263 struct rt_rq *group_rq = group_rt_rq(rt_se);
1264 struct task_struct *tsk;
1265
1266 if (group_rq)
1267 return group_rq->rr_nr_running;
1268
1269 tsk = rt_task_of(rt_se);
1270
1271 return (tsk->policy == SCHED_RR) ? 1 : 0;
1272 }
1273
1274 static inline
inc_rt_tasks(struct sched_rt_entity * rt_se,struct rt_rq * rt_rq)1275 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1276 {
1277 int prio = rt_se_prio(rt_se);
1278
1279 WARN_ON(!rt_prio(prio));
1280 rt_rq->rt_nr_running += rt_se_nr_running(rt_se);
1281 rt_rq->rr_nr_running += rt_se_rr_nr_running(rt_se);
1282
1283 inc_rt_prio(rt_rq, prio);
1284 inc_rt_migration(rt_se, rt_rq);
1285 inc_rt_group(rt_se, rt_rq);
1286 }
1287
1288 static inline
dec_rt_tasks(struct sched_rt_entity * rt_se,struct rt_rq * rt_rq)1289 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
1290 {
1291 WARN_ON(!rt_prio(rt_se_prio(rt_se)));
1292 WARN_ON(!rt_rq->rt_nr_running);
1293 rt_rq->rt_nr_running -= rt_se_nr_running(rt_se);
1294 rt_rq->rr_nr_running -= rt_se_rr_nr_running(rt_se);
1295
1296 dec_rt_prio(rt_rq, rt_se_prio(rt_se));
1297 dec_rt_migration(rt_se, rt_rq);
1298 dec_rt_group(rt_se, rt_rq);
1299 }
1300
1301 /*
1302 * Change rt_se->run_list location unless SAVE && !MOVE
1303 *
1304 * assumes ENQUEUE/DEQUEUE flags match
1305 */
move_entity(unsigned int flags)1306 static inline bool move_entity(unsigned int flags)
1307 {
1308 if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
1309 return false;
1310
1311 return true;
1312 }
1313
__delist_rt_entity(struct sched_rt_entity * rt_se,struct rt_prio_array * array)1314 static void __delist_rt_entity(struct sched_rt_entity *rt_se, struct rt_prio_array *array)
1315 {
1316 list_del_init(&rt_se->run_list);
1317
1318 if (list_empty(array->queue + rt_se_prio(rt_se)))
1319 __clear_bit(rt_se_prio(rt_se), array->bitmap);
1320
1321 rt_se->on_list = 0;
1322 }
1323
1324 static inline struct sched_statistics *
__schedstats_from_rt_se(struct sched_rt_entity * rt_se)1325 __schedstats_from_rt_se(struct sched_rt_entity *rt_se)
1326 {
1327 #ifdef CONFIG_RT_GROUP_SCHED
1328 /* schedstats is not supported for rt group. */
1329 if (!rt_entity_is_task(rt_se))
1330 return NULL;
1331 #endif
1332
1333 return &rt_task_of(rt_se)->stats;
1334 }
1335
1336 static inline void
update_stats_wait_start_rt(struct rt_rq * rt_rq,struct sched_rt_entity * rt_se)1337 update_stats_wait_start_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
1338 {
1339 struct sched_statistics *stats;
1340 struct task_struct *p = NULL;
1341
1342 if (!schedstat_enabled())
1343 return;
1344
1345 if (rt_entity_is_task(rt_se))
1346 p = rt_task_of(rt_se);
1347
1348 stats = __schedstats_from_rt_se(rt_se);
1349 if (!stats)
1350 return;
1351
1352 __update_stats_wait_start(rq_of_rt_rq(rt_rq), p, stats);
1353 }
1354
1355 static inline void
update_stats_enqueue_sleeper_rt(struct rt_rq * rt_rq,struct sched_rt_entity * rt_se)1356 update_stats_enqueue_sleeper_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
1357 {
1358 struct sched_statistics *stats;
1359 struct task_struct *p = NULL;
1360
1361 if (!schedstat_enabled())
1362 return;
1363
1364 if (rt_entity_is_task(rt_se))
1365 p = rt_task_of(rt_se);
1366
1367 stats = __schedstats_from_rt_se(rt_se);
1368 if (!stats)
1369 return;
1370
1371 __update_stats_enqueue_sleeper(rq_of_rt_rq(rt_rq), p, stats);
1372 }
1373
1374 static inline void
update_stats_enqueue_rt(struct rt_rq * rt_rq,struct sched_rt_entity * rt_se,int flags)1375 update_stats_enqueue_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se,
1376 int flags)
1377 {
1378 if (!schedstat_enabled())
1379 return;
1380
1381 if (flags & ENQUEUE_WAKEUP)
1382 update_stats_enqueue_sleeper_rt(rt_rq, rt_se);
1383 }
1384
1385 static inline void
update_stats_wait_end_rt(struct rt_rq * rt_rq,struct sched_rt_entity * rt_se)1386 update_stats_wait_end_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
1387 {
1388 struct sched_statistics *stats;
1389 struct task_struct *p = NULL;
1390
1391 if (!schedstat_enabled())
1392 return;
1393
1394 if (rt_entity_is_task(rt_se))
1395 p = rt_task_of(rt_se);
1396
1397 stats = __schedstats_from_rt_se(rt_se);
1398 if (!stats)
1399 return;
1400
1401 __update_stats_wait_end(rq_of_rt_rq(rt_rq), p, stats);
1402 }
1403
1404 static inline void
update_stats_dequeue_rt(struct rt_rq * rt_rq,struct sched_rt_entity * rt_se,int flags)1405 update_stats_dequeue_rt(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se,
1406 int flags)
1407 {
1408 struct task_struct *p = NULL;
1409
1410 if (!schedstat_enabled())
1411 return;
1412
1413 if (rt_entity_is_task(rt_se))
1414 p = rt_task_of(rt_se);
1415
1416 if ((flags & DEQUEUE_SLEEP) && p) {
1417 unsigned int state;
1418
1419 state = READ_ONCE(p->__state);
1420 if (state & TASK_INTERRUPTIBLE)
1421 __schedstat_set(p->stats.sleep_start,
1422 rq_clock(rq_of_rt_rq(rt_rq)));
1423
1424 if (state & TASK_UNINTERRUPTIBLE)
1425 __schedstat_set(p->stats.block_start,
1426 rq_clock(rq_of_rt_rq(rt_rq)));
1427 }
1428 }
1429
__enqueue_rt_entity(struct sched_rt_entity * rt_se,unsigned int flags)1430 static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1431 {
1432 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1433 struct rt_prio_array *array = &rt_rq->active;
1434 struct rt_rq *group_rq = group_rt_rq(rt_se);
1435 struct list_head *queue = array->queue + rt_se_prio(rt_se);
1436
1437 /*
1438 * Don't enqueue the group if its throttled, or when empty.
1439 * The latter is a consequence of the former when a child group
1440 * get throttled and the current group doesn't have any other
1441 * active members.
1442 */
1443 if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running)) {
1444 if (rt_se->on_list)
1445 __delist_rt_entity(rt_se, array);
1446 return;
1447 }
1448
1449 if (move_entity(flags)) {
1450 WARN_ON_ONCE(rt_se->on_list);
1451 if (flags & ENQUEUE_HEAD)
1452 list_add(&rt_se->run_list, queue);
1453 else
1454 list_add_tail(&rt_se->run_list, queue);
1455
1456 __set_bit(rt_se_prio(rt_se), array->bitmap);
1457 rt_se->on_list = 1;
1458 }
1459 rt_se->on_rq = 1;
1460
1461 inc_rt_tasks(rt_se, rt_rq);
1462 }
1463
__dequeue_rt_entity(struct sched_rt_entity * rt_se,unsigned int flags)1464 static void __dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1465 {
1466 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
1467 struct rt_prio_array *array = &rt_rq->active;
1468
1469 if (move_entity(flags)) {
1470 WARN_ON_ONCE(!rt_se->on_list);
1471 __delist_rt_entity(rt_se, array);
1472 }
1473 rt_se->on_rq = 0;
1474
1475 dec_rt_tasks(rt_se, rt_rq);
1476 }
1477
1478 /*
1479 * Because the prio of an upper entry depends on the lower
1480 * entries, we must remove entries top - down.
1481 */
dequeue_rt_stack(struct sched_rt_entity * rt_se,unsigned int flags)1482 static void dequeue_rt_stack(struct sched_rt_entity *rt_se, unsigned int flags)
1483 {
1484 struct sched_rt_entity *back = NULL;
1485 unsigned int rt_nr_running;
1486
1487 for_each_sched_rt_entity(rt_se) {
1488 rt_se->back = back;
1489 back = rt_se;
1490 }
1491
1492 rt_nr_running = rt_rq_of_se(back)->rt_nr_running;
1493
1494 for (rt_se = back; rt_se; rt_se = rt_se->back) {
1495 if (on_rt_rq(rt_se))
1496 __dequeue_rt_entity(rt_se, flags);
1497 }
1498
1499 dequeue_top_rt_rq(rt_rq_of_se(back), rt_nr_running);
1500 }
1501
enqueue_rt_entity(struct sched_rt_entity * rt_se,unsigned int flags)1502 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1503 {
1504 struct rq *rq = rq_of_rt_se(rt_se);
1505
1506 update_stats_enqueue_rt(rt_rq_of_se(rt_se), rt_se, flags);
1507
1508 dequeue_rt_stack(rt_se, flags);
1509 for_each_sched_rt_entity(rt_se)
1510 __enqueue_rt_entity(rt_se, flags);
1511 enqueue_top_rt_rq(&rq->rt);
1512 }
1513
dequeue_rt_entity(struct sched_rt_entity * rt_se,unsigned int flags)1514 static void dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
1515 {
1516 struct rq *rq = rq_of_rt_se(rt_se);
1517
1518 update_stats_dequeue_rt(rt_rq_of_se(rt_se), rt_se, flags);
1519
1520 dequeue_rt_stack(rt_se, flags);
1521
1522 for_each_sched_rt_entity(rt_se) {
1523 struct rt_rq *rt_rq = group_rt_rq(rt_se);
1524
1525 if (rt_rq && rt_rq->rt_nr_running)
1526 __enqueue_rt_entity(rt_se, flags);
1527 }
1528 enqueue_top_rt_rq(&rq->rt);
1529 }
1530
1531 /*
1532 * Adding/removing a task to/from a priority array:
1533 */
1534 static void
enqueue_task_rt(struct rq * rq,struct task_struct * p,int flags)1535 enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
1536 {
1537 struct sched_rt_entity *rt_se = &p->rt;
1538
1539 if (flags & ENQUEUE_WAKEUP)
1540 rt_se->timeout = 0;
1541
1542 check_schedstat_required();
1543 update_stats_wait_start_rt(rt_rq_of_se(rt_se), rt_se);
1544
1545 enqueue_rt_entity(rt_se, flags);
1546
1547 if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
1548 enqueue_pushable_task(rq, p);
1549 }
1550
dequeue_task_rt(struct rq * rq,struct task_struct * p,int flags)1551 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
1552 {
1553 struct sched_rt_entity *rt_se = &p->rt;
1554
1555 update_curr_rt(rq);
1556 dequeue_rt_entity(rt_se, flags);
1557
1558 dequeue_pushable_task(rq, p);
1559 }
1560
1561 /*
1562 * Put task to the head or the end of the run list without the overhead of
1563 * dequeue followed by enqueue.
1564 */
1565 static void
requeue_rt_entity(struct rt_rq * rt_rq,struct sched_rt_entity * rt_se,int head)1566 requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
1567 {
1568 if (on_rt_rq(rt_se)) {
1569 struct rt_prio_array *array = &rt_rq->active;
1570 struct list_head *queue = array->queue + rt_se_prio(rt_se);
1571
1572 if (head)
1573 list_move(&rt_se->run_list, queue);
1574 else
1575 list_move_tail(&rt_se->run_list, queue);
1576 }
1577 }
1578
requeue_task_rt(struct rq * rq,struct task_struct * p,int head)1579 static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
1580 {
1581 struct sched_rt_entity *rt_se = &p->rt;
1582 struct rt_rq *rt_rq;
1583
1584 for_each_sched_rt_entity(rt_se) {
1585 rt_rq = rt_rq_of_se(rt_se);
1586 requeue_rt_entity(rt_rq, rt_se, head);
1587 }
1588 }
1589
yield_task_rt(struct rq * rq)1590 static void yield_task_rt(struct rq *rq)
1591 {
1592 requeue_task_rt(rq, rq->curr, 0);
1593 }
1594
1595 #ifdef CONFIG_SMP
1596 static int find_lowest_rq(struct task_struct *task);
1597
1598 static int
select_task_rq_rt(struct task_struct * p,int cpu,int flags)1599 select_task_rq_rt(struct task_struct *p, int cpu, int flags)
1600 {
1601 struct task_struct *curr;
1602 struct rq *rq;
1603 bool test;
1604
1605 /* For anything but wake ups, just return the task_cpu */
1606 if (!(flags & (WF_TTWU | WF_FORK)))
1607 goto out;
1608
1609 rq = cpu_rq(cpu);
1610
1611 rcu_read_lock();
1612 curr = READ_ONCE(rq->curr); /* unlocked access */
1613
1614 /*
1615 * If the current task on @p's runqueue is an RT task, then
1616 * try to see if we can wake this RT task up on another
1617 * runqueue. Otherwise simply start this RT task
1618 * on its current runqueue.
1619 *
1620 * We want to avoid overloading runqueues. If the woken
1621 * task is a higher priority, then it will stay on this CPU
1622 * and the lower prio task should be moved to another CPU.
1623 * Even though this will probably make the lower prio task
1624 * lose its cache, we do not want to bounce a higher task
1625 * around just because it gave up its CPU, perhaps for a
1626 * lock?
1627 *
1628 * For equal prio tasks, we just let the scheduler sort it out.
1629 *
1630 * Otherwise, just let it ride on the affined RQ and the
1631 * post-schedule router will push the preempted task away
1632 *
1633 * This test is optimistic, if we get it wrong the load-balancer
1634 * will have to sort it out.
1635 *
1636 * We take into account the capacity of the CPU to ensure it fits the
1637 * requirement of the task - which is only important on heterogeneous
1638 * systems like big.LITTLE.
1639 */
1640 test = curr &&
1641 unlikely(rt_task(curr)) &&
1642 (curr->nr_cpus_allowed < 2 || curr->prio <= p->prio);
1643
1644 if (test || !rt_task_fits_capacity(p, cpu)) {
1645 int target = find_lowest_rq(p);
1646
1647 /*
1648 * Bail out if we were forcing a migration to find a better
1649 * fitting CPU but our search failed.
1650 */
1651 if (!test && target != -1 && !rt_task_fits_capacity(p, target))
1652 goto out_unlock;
1653
1654 /*
1655 * Don't bother moving it if the destination CPU is
1656 * not running a lower priority task.
1657 */
1658 if (target != -1 &&
1659 p->prio < cpu_rq(target)->rt.highest_prio.curr)
1660 cpu = target;
1661 }
1662
1663 out_unlock:
1664 rcu_read_unlock();
1665
1666 out:
1667 return cpu;
1668 }
1669
check_preempt_equal_prio(struct rq * rq,struct task_struct * p)1670 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
1671 {
1672 /*
1673 * Current can't be migrated, useless to reschedule,
1674 * let's hope p can move out.
1675 */
1676 if (rq->curr->nr_cpus_allowed == 1 ||
1677 !cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
1678 return;
1679
1680 /*
1681 * p is migratable, so let's not schedule it and
1682 * see if it is pushed or pulled somewhere else.
1683 */
1684 if (p->nr_cpus_allowed != 1 &&
1685 cpupri_find(&rq->rd->cpupri, p, NULL))
1686 return;
1687
1688 /*
1689 * There appear to be other CPUs that can accept
1690 * the current task but none can run 'p', so lets reschedule
1691 * to try and push the current task away:
1692 */
1693 requeue_task_rt(rq, p, 1);
1694 resched_curr(rq);
1695 }
1696
balance_rt(struct rq * rq,struct task_struct * p,struct rq_flags * rf)1697 static int balance_rt(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
1698 {
1699 if (!on_rt_rq(&p->rt) && need_pull_rt_task(rq, p)) {
1700 /*
1701 * This is OK, because current is on_cpu, which avoids it being
1702 * picked for load-balance and preemption/IRQs are still
1703 * disabled avoiding further scheduler activity on it and we've
1704 * not yet started the picking loop.
1705 */
1706 rq_unpin_lock(rq, rf);
1707 pull_rt_task(rq);
1708 rq_repin_lock(rq, rf);
1709 }
1710
1711 return sched_stop_runnable(rq) || sched_dl_runnable(rq) || sched_rt_runnable(rq);
1712 }
1713 #endif /* CONFIG_SMP */
1714
1715 /*
1716 * Preempt the current task with a newly woken task if needed:
1717 */
check_preempt_curr_rt(struct rq * rq,struct task_struct * p,int flags)1718 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
1719 {
1720 if (p->prio < rq->curr->prio) {
1721 resched_curr(rq);
1722 return;
1723 }
1724
1725 #ifdef CONFIG_SMP
1726 /*
1727 * If:
1728 *
1729 * - the newly woken task is of equal priority to the current task
1730 * - the newly woken task is non-migratable while current is migratable
1731 * - current will be preempted on the next reschedule
1732 *
1733 * we should check to see if current can readily move to a different
1734 * cpu. If so, we will reschedule to allow the push logic to try
1735 * to move current somewhere else, making room for our non-migratable
1736 * task.
1737 */
1738 if (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr))
1739 check_preempt_equal_prio(rq, p);
1740 #endif
1741 }
1742
set_next_task_rt(struct rq * rq,struct task_struct * p,bool first)1743 static inline void set_next_task_rt(struct rq *rq, struct task_struct *p, bool first)
1744 {
1745 struct sched_rt_entity *rt_se = &p->rt;
1746 struct rt_rq *rt_rq = &rq->rt;
1747
1748 p->se.exec_start = rq_clock_task(rq);
1749 if (on_rt_rq(&p->rt))
1750 update_stats_wait_end_rt(rt_rq, rt_se);
1751
1752 /* The running task is never eligible for pushing */
1753 dequeue_pushable_task(rq, p);
1754
1755 if (!first)
1756 return;
1757
1758 /*
1759 * If prev task was rt, put_prev_task() has already updated the
1760 * utilization. We only care of the case where we start to schedule a
1761 * rt task
1762 */
1763 if (rq->curr->sched_class != &rt_sched_class)
1764 update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);
1765
1766 rt_queue_push_tasks(rq);
1767 }
1768
pick_next_rt_entity(struct rt_rq * rt_rq)1769 static struct sched_rt_entity *pick_next_rt_entity(struct rt_rq *rt_rq)
1770 {
1771 struct rt_prio_array *array = &rt_rq->active;
1772 struct sched_rt_entity *next = NULL;
1773 struct list_head *queue;
1774 int idx;
1775
1776 idx = sched_find_first_bit(array->bitmap);
1777 BUG_ON(idx >= MAX_RT_PRIO);
1778
1779 queue = array->queue + idx;
1780 next = list_entry(queue->next, struct sched_rt_entity, run_list);
1781
1782 return next;
1783 }
1784
_pick_next_task_rt(struct rq * rq)1785 static struct task_struct *_pick_next_task_rt(struct rq *rq)
1786 {
1787 struct sched_rt_entity *rt_se;
1788 struct rt_rq *rt_rq = &rq->rt;
1789
1790 do {
1791 rt_se = pick_next_rt_entity(rt_rq);
1792 BUG_ON(!rt_se);
1793 rt_rq = group_rt_rq(rt_se);
1794 } while (rt_rq);
1795
1796 return rt_task_of(rt_se);
1797 }
1798
pick_task_rt(struct rq * rq)1799 static struct task_struct *pick_task_rt(struct rq *rq)
1800 {
1801 struct task_struct *p;
1802
1803 if (!sched_rt_runnable(rq))
1804 return NULL;
1805
1806 p = _pick_next_task_rt(rq);
1807
1808 return p;
1809 }
1810
pick_next_task_rt(struct rq * rq)1811 static struct task_struct *pick_next_task_rt(struct rq *rq)
1812 {
1813 struct task_struct *p = pick_task_rt(rq);
1814
1815 if (p)
1816 set_next_task_rt(rq, p, true);
1817
1818 return p;
1819 }
1820
put_prev_task_rt(struct rq * rq,struct task_struct * p)1821 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
1822 {
1823 struct sched_rt_entity *rt_se = &p->rt;
1824 struct rt_rq *rt_rq = &rq->rt;
1825
1826 if (on_rt_rq(&p->rt))
1827 update_stats_wait_start_rt(rt_rq, rt_se);
1828
1829 update_curr_rt(rq);
1830
1831 update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 1);
1832
1833 /*
1834 * The previous task needs to be made eligible for pushing
1835 * if it is still active
1836 */
1837 if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1)
1838 enqueue_pushable_task(rq, p);
1839 }
1840
1841 #ifdef CONFIG_SMP
1842
1843 /* Only try algorithms three times */
1844 #define RT_MAX_TRIES 3
1845
pick_rt_task(struct rq * rq,struct task_struct * p,int cpu)1846 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
1847 {
1848 if (!task_on_cpu(rq, p) &&
1849 cpumask_test_cpu(cpu, &p->cpus_mask))
1850 return 1;
1851
1852 return 0;
1853 }
1854
1855 /*
1856 * Return the highest pushable rq's task, which is suitable to be executed
1857 * on the CPU, NULL otherwise
1858 */
pick_highest_pushable_task(struct rq * rq,int cpu)1859 static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)
1860 {
1861 struct plist_head *head = &rq->rt.pushable_tasks;
1862 struct task_struct *p;
1863
1864 if (!has_pushable_tasks(rq))
1865 return NULL;
1866
1867 plist_for_each_entry(p, head, pushable_tasks) {
1868 if (pick_rt_task(rq, p, cpu))
1869 return p;
1870 }
1871
1872 return NULL;
1873 }
1874
1875 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
1876
find_lowest_rq(struct task_struct * task)1877 static int find_lowest_rq(struct task_struct *task)
1878 {
1879 struct sched_domain *sd;
1880 struct cpumask *lowest_mask = this_cpu_cpumask_var_ptr(local_cpu_mask);
1881 int this_cpu = smp_processor_id();
1882 int cpu = task_cpu(task);
1883 int ret;
1884
1885 /* Make sure the mask is initialized first */
1886 if (unlikely(!lowest_mask))
1887 return -1;
1888
1889 if (task->nr_cpus_allowed == 1)
1890 return -1; /* No other targets possible */
1891
1892 /*
1893 * If we're on asym system ensure we consider the different capacities
1894 * of the CPUs when searching for the lowest_mask.
1895 */
1896 if (sched_asym_cpucap_active()) {
1897
1898 ret = cpupri_find_fitness(&task_rq(task)->rd->cpupri,
1899 task, lowest_mask,
1900 rt_task_fits_capacity);
1901 } else {
1902
1903 ret = cpupri_find(&task_rq(task)->rd->cpupri,
1904 task, lowest_mask);
1905 }
1906
1907 if (!ret)
1908 return -1; /* No targets found */
1909
1910 /*
1911 * At this point we have built a mask of CPUs representing the
1912 * lowest priority tasks in the system. Now we want to elect
1913 * the best one based on our affinity and topology.
1914 *
1915 * We prioritize the last CPU that the task executed on since
1916 * it is most likely cache-hot in that location.
1917 */
1918 if (cpumask_test_cpu(cpu, lowest_mask))
1919 return cpu;
1920
1921 /*
1922 * Otherwise, we consult the sched_domains span maps to figure
1923 * out which CPU is logically closest to our hot cache data.
1924 */
1925 if (!cpumask_test_cpu(this_cpu, lowest_mask))
1926 this_cpu = -1; /* Skip this_cpu opt if not among lowest */
1927
1928 rcu_read_lock();
1929 for_each_domain(cpu, sd) {
1930 if (sd->flags & SD_WAKE_AFFINE) {
1931 int best_cpu;
1932
1933 /*
1934 * "this_cpu" is cheaper to preempt than a
1935 * remote processor.
1936 */
1937 if (this_cpu != -1 &&
1938 cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
1939 rcu_read_unlock();
1940 return this_cpu;
1941 }
1942
1943 best_cpu = cpumask_any_and_distribute(lowest_mask,
1944 sched_domain_span(sd));
1945 if (best_cpu < nr_cpu_ids) {
1946 rcu_read_unlock();
1947 return best_cpu;
1948 }
1949 }
1950 }
1951 rcu_read_unlock();
1952
1953 /*
1954 * And finally, if there were no matches within the domains
1955 * just give the caller *something* to work with from the compatible
1956 * locations.
1957 */
1958 if (this_cpu != -1)
1959 return this_cpu;
1960
1961 cpu = cpumask_any_distribute(lowest_mask);
1962 if (cpu < nr_cpu_ids)
1963 return cpu;
1964
1965 return -1;
1966 }
1967
1968 /* Will lock the rq it finds */
find_lock_lowest_rq(struct task_struct * task,struct rq * rq)1969 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1970 {
1971 struct rq *lowest_rq = NULL;
1972 int tries;
1973 int cpu;
1974
1975 for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1976 cpu = find_lowest_rq(task);
1977
1978 if ((cpu == -1) || (cpu == rq->cpu))
1979 break;
1980
1981 lowest_rq = cpu_rq(cpu);
1982
1983 if (lowest_rq->rt.highest_prio.curr <= task->prio) {
1984 /*
1985 * Target rq has tasks of equal or higher priority,
1986 * retrying does not release any lock and is unlikely
1987 * to yield a different result.
1988 */
1989 lowest_rq = NULL;
1990 break;
1991 }
1992
1993 /* if the prio of this runqueue changed, try again */
1994 if (double_lock_balance(rq, lowest_rq)) {
1995 /*
1996 * We had to unlock the run queue. In
1997 * the mean time, task could have
1998 * migrated already or had its affinity changed.
1999 * Also make sure that it wasn't scheduled on its rq.
2000 */
2001 if (unlikely(task_rq(task) != rq ||
2002 !cpumask_test_cpu(lowest_rq->cpu, &task->cpus_mask) ||
2003 task_on_cpu(rq, task) ||
2004 !rt_task(task) ||
2005 !task_on_rq_queued(task))) {
2006
2007 double_unlock_balance(rq, lowest_rq);
2008 lowest_rq = NULL;
2009 break;
2010 }
2011 }
2012
2013 /* If this rq is still suitable use it. */
2014 if (lowest_rq->rt.highest_prio.curr > task->prio)
2015 break;
2016
2017 /* try again */
2018 double_unlock_balance(rq, lowest_rq);
2019 lowest_rq = NULL;
2020 }
2021
2022 return lowest_rq;
2023 }
2024
pick_next_pushable_task(struct rq * rq)2025 static struct task_struct *pick_next_pushable_task(struct rq *rq)
2026 {
2027 struct task_struct *p;
2028
2029 if (!has_pushable_tasks(rq))
2030 return NULL;
2031
2032 p = plist_first_entry(&rq->rt.pushable_tasks,
2033 struct task_struct, pushable_tasks);
2034
2035 BUG_ON(rq->cpu != task_cpu(p));
2036 BUG_ON(task_current(rq, p));
2037 BUG_ON(p->nr_cpus_allowed <= 1);
2038
2039 BUG_ON(!task_on_rq_queued(p));
2040 BUG_ON(!rt_task(p));
2041
2042 return p;
2043 }
2044
2045 /*
2046 * If the current CPU has more than one RT task, see if the non
2047 * running task can migrate over to a CPU that is running a task
2048 * of lesser priority.
2049 */
push_rt_task(struct rq * rq,bool pull)2050 static int push_rt_task(struct rq *rq, bool pull)
2051 {
2052 struct task_struct *next_task;
2053 struct rq *lowest_rq;
2054 int ret = 0;
2055
2056 if (!rq->rt.overloaded)
2057 return 0;
2058
2059 next_task = pick_next_pushable_task(rq);
2060 if (!next_task)
2061 return 0;
2062
2063 retry:
2064 /*
2065 * It's possible that the next_task slipped in of
2066 * higher priority than current. If that's the case
2067 * just reschedule current.
2068 */
2069 if (unlikely(next_task->prio < rq->curr->prio)) {
2070 resched_curr(rq);
2071 return 0;
2072 }
2073
2074 if (is_migration_disabled(next_task)) {
2075 struct task_struct *push_task = NULL;
2076 int cpu;
2077
2078 if (!pull || rq->push_busy)
2079 return 0;
2080
2081 /*
2082 * Invoking find_lowest_rq() on anything but an RT task doesn't
2083 * make sense. Per the above priority check, curr has to
2084 * be of higher priority than next_task, so no need to
2085 * reschedule when bailing out.
2086 *
2087 * Note that the stoppers are masqueraded as SCHED_FIFO
2088 * (cf. sched_set_stop_task()), so we can't rely on rt_task().
2089 */
2090 if (rq->curr->sched_class != &rt_sched_class)
2091 return 0;
2092
2093 cpu = find_lowest_rq(rq->curr);
2094 if (cpu == -1 || cpu == rq->cpu)
2095 return 0;
2096
2097 /*
2098 * Given we found a CPU with lower priority than @next_task,
2099 * therefore it should be running. However we cannot migrate it
2100 * to this other CPU, instead attempt to push the current
2101 * running task on this CPU away.
2102 */
2103 push_task = get_push_task(rq);
2104 if (push_task) {
2105 raw_spin_rq_unlock(rq);
2106 stop_one_cpu_nowait(rq->cpu, push_cpu_stop,
2107 push_task, &rq->push_work);
2108 raw_spin_rq_lock(rq);
2109 }
2110
2111 return 0;
2112 }
2113
2114 if (WARN_ON(next_task == rq->curr))
2115 return 0;
2116
2117 /* We might release rq lock */
2118 get_task_struct(next_task);
2119
2120 /* find_lock_lowest_rq locks the rq if found */
2121 lowest_rq = find_lock_lowest_rq(next_task, rq);
2122 if (!lowest_rq) {
2123 struct task_struct *task;
2124 /*
2125 * find_lock_lowest_rq releases rq->lock
2126 * so it is possible that next_task has migrated.
2127 *
2128 * We need to make sure that the task is still on the same
2129 * run-queue and is also still the next task eligible for
2130 * pushing.
2131 */
2132 task = pick_next_pushable_task(rq);
2133 if (task == next_task) {
2134 /*
2135 * The task hasn't migrated, and is still the next
2136 * eligible task, but we failed to find a run-queue
2137 * to push it to. Do not retry in this case, since
2138 * other CPUs will pull from us when ready.
2139 */
2140 goto out;
2141 }
2142
2143 if (!task)
2144 /* No more tasks, just exit */
2145 goto out;
2146
2147 /*
2148 * Something has shifted, try again.
2149 */
2150 put_task_struct(next_task);
2151 next_task = task;
2152 goto retry;
2153 }
2154
2155 deactivate_task(rq, next_task, 0);
2156 set_task_cpu(next_task, lowest_rq->cpu);
2157 activate_task(lowest_rq, next_task, 0);
2158 resched_curr(lowest_rq);
2159 ret = 1;
2160
2161 double_unlock_balance(rq, lowest_rq);
2162 out:
2163 put_task_struct(next_task);
2164
2165 return ret;
2166 }
2167
push_rt_tasks(struct rq * rq)2168 static void push_rt_tasks(struct rq *rq)
2169 {
2170 /* push_rt_task will return true if it moved an RT */
2171 while (push_rt_task(rq, false))
2172 ;
2173 }
2174
2175 #ifdef HAVE_RT_PUSH_IPI
2176
2177 /*
2178 * When a high priority task schedules out from a CPU and a lower priority
2179 * task is scheduled in, a check is made to see if there's any RT tasks
2180 * on other CPUs that are waiting to run because a higher priority RT task
2181 * is currently running on its CPU. In this case, the CPU with multiple RT
2182 * tasks queued on it (overloaded) needs to be notified that a CPU has opened
2183 * up that may be able to run one of its non-running queued RT tasks.
2184 *
2185 * All CPUs with overloaded RT tasks need to be notified as there is currently
2186 * no way to know which of these CPUs have the highest priority task waiting
2187 * to run. Instead of trying to take a spinlock on each of these CPUs,
2188 * which has shown to cause large latency when done on machines with many
2189 * CPUs, sending an IPI to the CPUs to have them push off the overloaded
2190 * RT tasks waiting to run.
2191 *
2192 * Just sending an IPI to each of the CPUs is also an issue, as on large
2193 * count CPU machines, this can cause an IPI storm on a CPU, especially
2194 * if its the only CPU with multiple RT tasks queued, and a large number
2195 * of CPUs scheduling a lower priority task at the same time.
2196 *
2197 * Each root domain has its own irq work function that can iterate over
2198 * all CPUs with RT overloaded tasks. Since all CPUs with overloaded RT
2199 * task must be checked if there's one or many CPUs that are lowering
2200 * their priority, there's a single irq work iterator that will try to
2201 * push off RT tasks that are waiting to run.
2202 *
2203 * When a CPU schedules a lower priority task, it will kick off the
2204 * irq work iterator that will jump to each CPU with overloaded RT tasks.
2205 * As it only takes the first CPU that schedules a lower priority task
2206 * to start the process, the rto_start variable is incremented and if
2207 * the atomic result is one, then that CPU will try to take the rto_lock.
2208 * This prevents high contention on the lock as the process handles all
2209 * CPUs scheduling lower priority tasks.
2210 *
2211 * All CPUs that are scheduling a lower priority task will increment the
2212 * rt_loop_next variable. This will make sure that the irq work iterator
2213 * checks all RT overloaded CPUs whenever a CPU schedules a new lower
2214 * priority task, even if the iterator is in the middle of a scan. Incrementing
2215 * the rt_loop_next will cause the iterator to perform another scan.
2216 *
2217 */
rto_next_cpu(struct root_domain * rd)2218 static int rto_next_cpu(struct root_domain *rd)
2219 {
2220 int next;
2221 int cpu;
2222
2223 /*
2224 * When starting the IPI RT pushing, the rto_cpu is set to -1,
2225 * rt_next_cpu() will simply return the first CPU found in
2226 * the rto_mask.
2227 *
2228 * If rto_next_cpu() is called with rto_cpu is a valid CPU, it
2229 * will return the next CPU found in the rto_mask.
2230 *
2231 * If there are no more CPUs left in the rto_mask, then a check is made
2232 * against rto_loop and rto_loop_next. rto_loop is only updated with
2233 * the rto_lock held, but any CPU may increment the rto_loop_next
2234 * without any locking.
2235 */
2236 for (;;) {
2237
2238 /* When rto_cpu is -1 this acts like cpumask_first() */
2239 cpu = cpumask_next(rd->rto_cpu, rd->rto_mask);
2240
2241 rd->rto_cpu = cpu;
2242
2243 if (cpu < nr_cpu_ids)
2244 return cpu;
2245
2246 rd->rto_cpu = -1;
2247
2248 /*
2249 * ACQUIRE ensures we see the @rto_mask changes
2250 * made prior to the @next value observed.
2251 *
2252 * Matches WMB in rt_set_overload().
2253 */
2254 next = atomic_read_acquire(&rd->rto_loop_next);
2255
2256 if (rd->rto_loop == next)
2257 break;
2258
2259 rd->rto_loop = next;
2260 }
2261
2262 return -1;
2263 }
2264
rto_start_trylock(atomic_t * v)2265 static inline bool rto_start_trylock(atomic_t *v)
2266 {
2267 return !atomic_cmpxchg_acquire(v, 0, 1);
2268 }
2269
rto_start_unlock(atomic_t * v)2270 static inline void rto_start_unlock(atomic_t *v)
2271 {
2272 atomic_set_release(v, 0);
2273 }
2274
tell_cpu_to_push(struct rq * rq)2275 static void tell_cpu_to_push(struct rq *rq)
2276 {
2277 int cpu = -1;
2278
2279 /* Keep the loop going if the IPI is currently active */
2280 atomic_inc(&rq->rd->rto_loop_next);
2281
2282 /* Only one CPU can initiate a loop at a time */
2283 if (!rto_start_trylock(&rq->rd->rto_loop_start))
2284 return;
2285
2286 raw_spin_lock(&rq->rd->rto_lock);
2287
2288 /*
2289 * The rto_cpu is updated under the lock, if it has a valid CPU
2290 * then the IPI is still running and will continue due to the
2291 * update to loop_next, and nothing needs to be done here.
2292 * Otherwise it is finishing up and an ipi needs to be sent.
2293 */
2294 if (rq->rd->rto_cpu < 0)
2295 cpu = rto_next_cpu(rq->rd);
2296
2297 raw_spin_unlock(&rq->rd->rto_lock);
2298
2299 rto_start_unlock(&rq->rd->rto_loop_start);
2300
2301 if (cpu >= 0) {
2302 /* Make sure the rd does not get freed while pushing */
2303 sched_get_rd(rq->rd);
2304 irq_work_queue_on(&rq->rd->rto_push_work, cpu);
2305 }
2306 }
2307
2308 /* Called from hardirq context */
rto_push_irq_work_func(struct irq_work * work)2309 void rto_push_irq_work_func(struct irq_work *work)
2310 {
2311 struct root_domain *rd =
2312 container_of(work, struct root_domain, rto_push_work);
2313 struct rq *rq;
2314 int cpu;
2315
2316 rq = this_rq();
2317
2318 /*
2319 * We do not need to grab the lock to check for has_pushable_tasks.
2320 * When it gets updated, a check is made if a push is possible.
2321 */
2322 if (has_pushable_tasks(rq)) {
2323 raw_spin_rq_lock(rq);
2324 while (push_rt_task(rq, true))
2325 ;
2326 raw_spin_rq_unlock(rq);
2327 }
2328
2329 raw_spin_lock(&rd->rto_lock);
2330
2331 /* Pass the IPI to the next rt overloaded queue */
2332 cpu = rto_next_cpu(rd);
2333
2334 raw_spin_unlock(&rd->rto_lock);
2335
2336 if (cpu < 0) {
2337 sched_put_rd(rd);
2338 return;
2339 }
2340
2341 /* Try the next RT overloaded CPU */
2342 irq_work_queue_on(&rd->rto_push_work, cpu);
2343 }
2344 #endif /* HAVE_RT_PUSH_IPI */
2345
pull_rt_task(struct rq * this_rq)2346 static void pull_rt_task(struct rq *this_rq)
2347 {
2348 int this_cpu = this_rq->cpu, cpu;
2349 bool resched = false;
2350 struct task_struct *p, *push_task;
2351 struct rq *src_rq;
2352 int rt_overload_count = rt_overloaded(this_rq);
2353
2354 if (likely(!rt_overload_count))
2355 return;
2356
2357 /*
2358 * Match the barrier from rt_set_overloaded; this guarantees that if we
2359 * see overloaded we must also see the rto_mask bit.
2360 */
2361 smp_rmb();
2362
2363 /* If we are the only overloaded CPU do nothing */
2364 if (rt_overload_count == 1 &&
2365 cpumask_test_cpu(this_rq->cpu, this_rq->rd->rto_mask))
2366 return;
2367
2368 #ifdef HAVE_RT_PUSH_IPI
2369 if (sched_feat(RT_PUSH_IPI)) {
2370 tell_cpu_to_push(this_rq);
2371 return;
2372 }
2373 #endif
2374
2375 for_each_cpu(cpu, this_rq->rd->rto_mask) {
2376 if (this_cpu == cpu)
2377 continue;
2378
2379 src_rq = cpu_rq(cpu);
2380
2381 /*
2382 * Don't bother taking the src_rq->lock if the next highest
2383 * task is known to be lower-priority than our current task.
2384 * This may look racy, but if this value is about to go
2385 * logically higher, the src_rq will push this task away.
2386 * And if its going logically lower, we do not care
2387 */
2388 if (src_rq->rt.highest_prio.next >=
2389 this_rq->rt.highest_prio.curr)
2390 continue;
2391
2392 /*
2393 * We can potentially drop this_rq's lock in
2394 * double_lock_balance, and another CPU could
2395 * alter this_rq
2396 */
2397 push_task = NULL;
2398 double_lock_balance(this_rq, src_rq);
2399
2400 /*
2401 * We can pull only a task, which is pushable
2402 * on its rq, and no others.
2403 */
2404 p = pick_highest_pushable_task(src_rq, this_cpu);
2405
2406 /*
2407 * Do we have an RT task that preempts
2408 * the to-be-scheduled task?
2409 */
2410 if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
2411 WARN_ON(p == src_rq->curr);
2412 WARN_ON(!task_on_rq_queued(p));
2413
2414 /*
2415 * There's a chance that p is higher in priority
2416 * than what's currently running on its CPU.
2417 * This is just that p is waking up and hasn't
2418 * had a chance to schedule. We only pull
2419 * p if it is lower in priority than the
2420 * current task on the run queue
2421 */
2422 if (p->prio < src_rq->curr->prio)
2423 goto skip;
2424
2425 if (is_migration_disabled(p)) {
2426 push_task = get_push_task(src_rq);
2427 } else {
2428 deactivate_task(src_rq, p, 0);
2429 set_task_cpu(p, this_cpu);
2430 activate_task(this_rq, p, 0);
2431 resched = true;
2432 }
2433 /*
2434 * We continue with the search, just in
2435 * case there's an even higher prio task
2436 * in another runqueue. (low likelihood
2437 * but possible)
2438 */
2439 }
2440 skip:
2441 double_unlock_balance(this_rq, src_rq);
2442
2443 if (push_task) {
2444 raw_spin_rq_unlock(this_rq);
2445 stop_one_cpu_nowait(src_rq->cpu, push_cpu_stop,
2446 push_task, &src_rq->push_work);
2447 raw_spin_rq_lock(this_rq);
2448 }
2449 }
2450
2451 if (resched)
2452 resched_curr(this_rq);
2453 }
2454
2455 /*
2456 * If we are not running and we are not going to reschedule soon, we should
2457 * try to push tasks away now
2458 */
task_woken_rt(struct rq * rq,struct task_struct * p)2459 static void task_woken_rt(struct rq *rq, struct task_struct *p)
2460 {
2461 bool need_to_push = !task_on_cpu(rq, p) &&
2462 !test_tsk_need_resched(rq->curr) &&
2463 p->nr_cpus_allowed > 1 &&
2464 (dl_task(rq->curr) || rt_task(rq->curr)) &&
2465 (rq->curr->nr_cpus_allowed < 2 ||
2466 rq->curr->prio <= p->prio);
2467
2468 if (need_to_push)
2469 push_rt_tasks(rq);
2470 }
2471
2472 /* Assumes rq->lock is held */
rq_online_rt(struct rq * rq)2473 static void rq_online_rt(struct rq *rq)
2474 {
2475 if (rq->rt.overloaded)
2476 rt_set_overload(rq);
2477
2478 __enable_runtime(rq);
2479
2480 cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
2481 }
2482
2483 /* Assumes rq->lock is held */
rq_offline_rt(struct rq * rq)2484 static void rq_offline_rt(struct rq *rq)
2485 {
2486 if (rq->rt.overloaded)
2487 rt_clear_overload(rq);
2488
2489 __disable_runtime(rq);
2490
2491 cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
2492 }
2493
2494 /*
2495 * When switch from the rt queue, we bring ourselves to a position
2496 * that we might want to pull RT tasks from other runqueues.
2497 */
switched_from_rt(struct rq * rq,struct task_struct * p)2498 static void switched_from_rt(struct rq *rq, struct task_struct *p)
2499 {
2500 /*
2501 * If there are other RT tasks then we will reschedule
2502 * and the scheduling of the other RT tasks will handle
2503 * the balancing. But if we are the last RT task
2504 * we may need to handle the pulling of RT tasks
2505 * now.
2506 */
2507 if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
2508 return;
2509
2510 rt_queue_pull_task(rq);
2511 }
2512
init_sched_rt_class(void)2513 void __init init_sched_rt_class(void)
2514 {
2515 unsigned int i;
2516
2517 for_each_possible_cpu(i) {
2518 zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
2519 GFP_KERNEL, cpu_to_node(i));
2520 }
2521 }
2522 #endif /* CONFIG_SMP */
2523
2524 /*
2525 * When switching a task to RT, we may overload the runqueue
2526 * with RT tasks. In this case we try to push them off to
2527 * other runqueues.
2528 */
switched_to_rt(struct rq * rq,struct task_struct * p)2529 static void switched_to_rt(struct rq *rq, struct task_struct *p)
2530 {
2531 /*
2532 * If we are running, update the avg_rt tracking, as the running time
2533 * will now on be accounted into the latter.
2534 */
2535 if (task_current(rq, p)) {
2536 update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);
2537 return;
2538 }
2539
2540 /*
2541 * If we are not running we may need to preempt the current
2542 * running task. If that current running task is also an RT task
2543 * then see if we can move to another run queue.
2544 */
2545 if (task_on_rq_queued(p)) {
2546 #ifdef CONFIG_SMP
2547 if (p->nr_cpus_allowed > 1 && rq->rt.overloaded)
2548 rt_queue_push_tasks(rq);
2549 #endif /* CONFIG_SMP */
2550 if (p->prio < rq->curr->prio && cpu_online(cpu_of(rq)))
2551 resched_curr(rq);
2552 }
2553 }
2554
2555 /*
2556 * Priority of the task has changed. This may cause
2557 * us to initiate a push or pull.
2558 */
2559 static void
prio_changed_rt(struct rq * rq,struct task_struct * p,int oldprio)2560 prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
2561 {
2562 if (!task_on_rq_queued(p))
2563 return;
2564
2565 if (task_current(rq, p)) {
2566 #ifdef CONFIG_SMP
2567 /*
2568 * If our priority decreases while running, we
2569 * may need to pull tasks to this runqueue.
2570 */
2571 if (oldprio < p->prio)
2572 rt_queue_pull_task(rq);
2573
2574 /*
2575 * If there's a higher priority task waiting to run
2576 * then reschedule.
2577 */
2578 if (p->prio > rq->rt.highest_prio.curr)
2579 resched_curr(rq);
2580 #else
2581 /* For UP simply resched on drop of prio */
2582 if (oldprio < p->prio)
2583 resched_curr(rq);
2584 #endif /* CONFIG_SMP */
2585 } else {
2586 /*
2587 * This task is not running, but if it is
2588 * greater than the current running task
2589 * then reschedule.
2590 */
2591 if (p->prio < rq->curr->prio)
2592 resched_curr(rq);
2593 }
2594 }
2595
2596 #ifdef CONFIG_POSIX_TIMERS
watchdog(struct rq * rq,struct task_struct * p)2597 static void watchdog(struct rq *rq, struct task_struct *p)
2598 {
2599 unsigned long soft, hard;
2600
2601 /* max may change after cur was read, this will be fixed next tick */
2602 soft = task_rlimit(p, RLIMIT_RTTIME);
2603 hard = task_rlimit_max(p, RLIMIT_RTTIME);
2604
2605 if (soft != RLIM_INFINITY) {
2606 unsigned long next;
2607
2608 if (p->rt.watchdog_stamp != jiffies) {
2609 p->rt.timeout++;
2610 p->rt.watchdog_stamp = jiffies;
2611 }
2612
2613 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
2614 if (p->rt.timeout > next) {
2615 posix_cputimers_rt_watchdog(&p->posix_cputimers,
2616 p->se.sum_exec_runtime);
2617 }
2618 }
2619 }
2620 #else
watchdog(struct rq * rq,struct task_struct * p)2621 static inline void watchdog(struct rq *rq, struct task_struct *p) { }
2622 #endif
2623
2624 /*
2625 * scheduler tick hitting a task of our scheduling class.
2626 *
2627 * NOTE: This function can be called remotely by the tick offload that
2628 * goes along full dynticks. Therefore no local assumption can be made
2629 * and everything must be accessed through the @rq and @curr passed in
2630 * parameters.
2631 */
task_tick_rt(struct rq * rq,struct task_struct * p,int queued)2632 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
2633 {
2634 struct sched_rt_entity *rt_se = &p->rt;
2635
2636 update_curr_rt(rq);
2637 update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 1);
2638
2639 watchdog(rq, p);
2640
2641 /*
2642 * RR tasks need a special form of timeslice management.
2643 * FIFO tasks have no timeslices.
2644 */
2645 if (p->policy != SCHED_RR)
2646 return;
2647
2648 if (--p->rt.time_slice)
2649 return;
2650
2651 p->rt.time_slice = sched_rr_timeslice;
2652
2653 /*
2654 * Requeue to the end of queue if we (and all of our ancestors) are not
2655 * the only element on the queue
2656 */
2657 for_each_sched_rt_entity(rt_se) {
2658 if (rt_se->run_list.prev != rt_se->run_list.next) {
2659 requeue_task_rt(rq, p, 0);
2660 resched_curr(rq);
2661 return;
2662 }
2663 }
2664 }
2665
get_rr_interval_rt(struct rq * rq,struct task_struct * task)2666 static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
2667 {
2668 /*
2669 * Time slice is 0 for SCHED_FIFO tasks
2670 */
2671 if (task->policy == SCHED_RR)
2672 return sched_rr_timeslice;
2673 else
2674 return 0;
2675 }
2676
2677 DEFINE_SCHED_CLASS(rt) = {
2678
2679 .enqueue_task = enqueue_task_rt,
2680 .dequeue_task = dequeue_task_rt,
2681 .yield_task = yield_task_rt,
2682
2683 .check_preempt_curr = check_preempt_curr_rt,
2684
2685 .pick_next_task = pick_next_task_rt,
2686 .put_prev_task = put_prev_task_rt,
2687 .set_next_task = set_next_task_rt,
2688
2689 #ifdef CONFIG_SMP
2690 .balance = balance_rt,
2691 .pick_task = pick_task_rt,
2692 .select_task_rq = select_task_rq_rt,
2693 .set_cpus_allowed = set_cpus_allowed_common,
2694 .rq_online = rq_online_rt,
2695 .rq_offline = rq_offline_rt,
2696 .task_woken = task_woken_rt,
2697 .switched_from = switched_from_rt,
2698 .find_lock_rq = find_lock_lowest_rq,
2699 #endif
2700
2701 .task_tick = task_tick_rt,
2702
2703 .get_rr_interval = get_rr_interval_rt,
2704
2705 .prio_changed = prio_changed_rt,
2706 .switched_to = switched_to_rt,
2707
2708 .update_curr = update_curr_rt,
2709
2710 #ifdef CONFIG_UCLAMP_TASK
2711 .uclamp_enabled = 1,
2712 #endif
2713 };
2714
2715 #ifdef CONFIG_RT_GROUP_SCHED
2716 /*
2717 * Ensure that the real time constraints are schedulable.
2718 */
2719 static DEFINE_MUTEX(rt_constraints_mutex);
2720
tg_has_rt_tasks(struct task_group * tg)2721 static inline int tg_has_rt_tasks(struct task_group *tg)
2722 {
2723 struct task_struct *task;
2724 struct css_task_iter it;
2725 int ret = 0;
2726
2727 /*
2728 * Autogroups do not have RT tasks; see autogroup_create().
2729 */
2730 if (task_group_is_autogroup(tg))
2731 return 0;
2732
2733 css_task_iter_start(&tg->css, 0, &it);
2734 while (!ret && (task = css_task_iter_next(&it)))
2735 ret |= rt_task(task);
2736 css_task_iter_end(&it);
2737
2738 return ret;
2739 }
2740
2741 struct rt_schedulable_data {
2742 struct task_group *tg;
2743 u64 rt_period;
2744 u64 rt_runtime;
2745 };
2746
tg_rt_schedulable(struct task_group * tg,void * data)2747 static int tg_rt_schedulable(struct task_group *tg, void *data)
2748 {
2749 struct rt_schedulable_data *d = data;
2750 struct task_group *child;
2751 unsigned long total, sum = 0;
2752 u64 period, runtime;
2753
2754 period = ktime_to_ns(tg->rt_bandwidth.rt_period);
2755 runtime = tg->rt_bandwidth.rt_runtime;
2756
2757 if (tg == d->tg) {
2758 period = d->rt_period;
2759 runtime = d->rt_runtime;
2760 }
2761
2762 /*
2763 * Cannot have more runtime than the period.
2764 */
2765 if (runtime > period && runtime != RUNTIME_INF)
2766 return -EINVAL;
2767
2768 /*
2769 * Ensure we don't starve existing RT tasks if runtime turns zero.
2770 */
2771 if (rt_bandwidth_enabled() && !runtime &&
2772 tg->rt_bandwidth.rt_runtime && tg_has_rt_tasks(tg))
2773 return -EBUSY;
2774
2775 total = to_ratio(period, runtime);
2776
2777 /*
2778 * Nobody can have more than the global setting allows.
2779 */
2780 if (total > to_ratio(global_rt_period(), global_rt_runtime()))
2781 return -EINVAL;
2782
2783 /*
2784 * The sum of our children's runtime should not exceed our own.
2785 */
2786 list_for_each_entry_rcu(child, &tg->children, siblings) {
2787 period = ktime_to_ns(child->rt_bandwidth.rt_period);
2788 runtime = child->rt_bandwidth.rt_runtime;
2789
2790 if (child == d->tg) {
2791 period = d->rt_period;
2792 runtime = d->rt_runtime;
2793 }
2794
2795 sum += to_ratio(period, runtime);
2796 }
2797
2798 if (sum > total)
2799 return -EINVAL;
2800
2801 return 0;
2802 }
2803
__rt_schedulable(struct task_group * tg,u64 period,u64 runtime)2804 static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
2805 {
2806 int ret;
2807
2808 struct rt_schedulable_data data = {
2809 .tg = tg,
2810 .rt_period = period,
2811 .rt_runtime = runtime,
2812 };
2813
2814 rcu_read_lock();
2815 ret = walk_tg_tree(tg_rt_schedulable, tg_nop, &data);
2816 rcu_read_unlock();
2817
2818 return ret;
2819 }
2820
tg_set_rt_bandwidth(struct task_group * tg,u64 rt_period,u64 rt_runtime)2821 static int tg_set_rt_bandwidth(struct task_group *tg,
2822 u64 rt_period, u64 rt_runtime)
2823 {
2824 int i, err = 0;
2825
2826 /*
2827 * Disallowing the root group RT runtime is BAD, it would disallow the
2828 * kernel creating (and or operating) RT threads.
2829 */
2830 if (tg == &root_task_group && rt_runtime == 0)
2831 return -EINVAL;
2832
2833 /* No period doesn't make any sense. */
2834 if (rt_period == 0)
2835 return -EINVAL;
2836
2837 /*
2838 * Bound quota to defend quota against overflow during bandwidth shift.
2839 */
2840 if (rt_runtime != RUNTIME_INF && rt_runtime > max_rt_runtime)
2841 return -EINVAL;
2842
2843 mutex_lock(&rt_constraints_mutex);
2844 err = __rt_schedulable(tg, rt_period, rt_runtime);
2845 if (err)
2846 goto unlock;
2847
2848 raw_spin_lock_irq(&tg->rt_bandwidth.rt_runtime_lock);
2849 tg->rt_bandwidth.rt_period = ns_to_ktime(rt_period);
2850 tg->rt_bandwidth.rt_runtime = rt_runtime;
2851
2852 for_each_possible_cpu(i) {
2853 struct rt_rq *rt_rq = tg->rt_rq[i];
2854
2855 raw_spin_lock(&rt_rq->rt_runtime_lock);
2856 rt_rq->rt_runtime = rt_runtime;
2857 raw_spin_unlock(&rt_rq->rt_runtime_lock);
2858 }
2859 raw_spin_unlock_irq(&tg->rt_bandwidth.rt_runtime_lock);
2860 unlock:
2861 mutex_unlock(&rt_constraints_mutex);
2862
2863 return err;
2864 }
2865
sched_group_set_rt_runtime(struct task_group * tg,long rt_runtime_us)2866 int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
2867 {
2868 u64 rt_runtime, rt_period;
2869
2870 rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period);
2871 rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
2872 if (rt_runtime_us < 0)
2873 rt_runtime = RUNTIME_INF;
2874 else if ((u64)rt_runtime_us > U64_MAX / NSEC_PER_USEC)
2875 return -EINVAL;
2876
2877 return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
2878 }
2879
sched_group_rt_runtime(struct task_group * tg)2880 long sched_group_rt_runtime(struct task_group *tg)
2881 {
2882 u64 rt_runtime_us;
2883
2884 if (tg->rt_bandwidth.rt_runtime == RUNTIME_INF)
2885 return -1;
2886
2887 rt_runtime_us = tg->rt_bandwidth.rt_runtime;
2888 do_div(rt_runtime_us, NSEC_PER_USEC);
2889 return rt_runtime_us;
2890 }
2891
sched_group_set_rt_period(struct task_group * tg,u64 rt_period_us)2892 int sched_group_set_rt_period(struct task_group *tg, u64 rt_period_us)
2893 {
2894 u64 rt_runtime, rt_period;
2895
2896 if (rt_period_us > U64_MAX / NSEC_PER_USEC)
2897 return -EINVAL;
2898
2899 rt_period = rt_period_us * NSEC_PER_USEC;
2900 rt_runtime = tg->rt_bandwidth.rt_runtime;
2901
2902 return tg_set_rt_bandwidth(tg, rt_period, rt_runtime);
2903 }
2904
sched_group_rt_period(struct task_group * tg)2905 long sched_group_rt_period(struct task_group *tg)
2906 {
2907 u64 rt_period_us;
2908
2909 rt_period_us = ktime_to_ns(tg->rt_bandwidth.rt_period);
2910 do_div(rt_period_us, NSEC_PER_USEC);
2911 return rt_period_us;
2912 }
2913
2914 #ifdef CONFIG_SYSCTL
sched_rt_global_constraints(void)2915 static int sched_rt_global_constraints(void)
2916 {
2917 int ret = 0;
2918
2919 mutex_lock(&rt_constraints_mutex);
2920 ret = __rt_schedulable(NULL, 0, 0);
2921 mutex_unlock(&rt_constraints_mutex);
2922
2923 return ret;
2924 }
2925 #endif /* CONFIG_SYSCTL */
2926
sched_rt_can_attach(struct task_group * tg,struct task_struct * tsk)2927 int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
2928 {
2929 /* Don't accept realtime tasks when there is no way for them to run */
2930 if (rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0)
2931 return 0;
2932
2933 return 1;
2934 }
2935
2936 #else /* !CONFIG_RT_GROUP_SCHED */
2937
2938 #ifdef CONFIG_SYSCTL
sched_rt_global_constraints(void)2939 static int sched_rt_global_constraints(void)
2940 {
2941 unsigned long flags;
2942 int i;
2943
2944 raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
2945 for_each_possible_cpu(i) {
2946 struct rt_rq *rt_rq = &cpu_rq(i)->rt;
2947
2948 raw_spin_lock(&rt_rq->rt_runtime_lock);
2949 rt_rq->rt_runtime = global_rt_runtime();
2950 raw_spin_unlock(&rt_rq->rt_runtime_lock);
2951 }
2952 raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
2953
2954 return 0;
2955 }
2956 #endif /* CONFIG_SYSCTL */
2957 #endif /* CONFIG_RT_GROUP_SCHED */
2958
2959 #ifdef CONFIG_SYSCTL
sched_rt_global_validate(void)2960 static int sched_rt_global_validate(void)
2961 {
2962 if (sysctl_sched_rt_period <= 0)
2963 return -EINVAL;
2964
2965 if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
2966 ((sysctl_sched_rt_runtime > sysctl_sched_rt_period) ||
2967 ((u64)sysctl_sched_rt_runtime *
2968 NSEC_PER_USEC > max_rt_runtime)))
2969 return -EINVAL;
2970
2971 return 0;
2972 }
2973
sched_rt_do_global(void)2974 static void sched_rt_do_global(void)
2975 {
2976 unsigned long flags;
2977
2978 raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
2979 def_rt_bandwidth.rt_runtime = global_rt_runtime();
2980 def_rt_bandwidth.rt_period = ns_to_ktime(global_rt_period());
2981 raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
2982 }
2983
sched_rt_handler(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)2984 static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
2985 size_t *lenp, loff_t *ppos)
2986 {
2987 int old_period, old_runtime;
2988 static DEFINE_MUTEX(mutex);
2989 int ret;
2990
2991 mutex_lock(&mutex);
2992 old_period = sysctl_sched_rt_period;
2993 old_runtime = sysctl_sched_rt_runtime;
2994
2995 ret = proc_dointvec(table, write, buffer, lenp, ppos);
2996
2997 if (!ret && write) {
2998 ret = sched_rt_global_validate();
2999 if (ret)
3000 goto undo;
3001
3002 ret = sched_dl_global_validate();
3003 if (ret)
3004 goto undo;
3005
3006 ret = sched_rt_global_constraints();
3007 if (ret)
3008 goto undo;
3009
3010 sched_rt_do_global();
3011 sched_dl_do_global();
3012 }
3013 if (0) {
3014 undo:
3015 sysctl_sched_rt_period = old_period;
3016 sysctl_sched_rt_runtime = old_runtime;
3017 }
3018 mutex_unlock(&mutex);
3019
3020 return ret;
3021 }
3022
sched_rr_handler(struct ctl_table * table,int write,void * buffer,size_t * lenp,loff_t * ppos)3023 static int sched_rr_handler(struct ctl_table *table, int write, void *buffer,
3024 size_t *lenp, loff_t *ppos)
3025 {
3026 int ret;
3027 static DEFINE_MUTEX(mutex);
3028
3029 mutex_lock(&mutex);
3030 ret = proc_dointvec(table, write, buffer, lenp, ppos);
3031 /*
3032 * Make sure that internally we keep jiffies.
3033 * Also, writing zero resets the timeslice to default:
3034 */
3035 if (!ret && write) {
3036 sched_rr_timeslice =
3037 sysctl_sched_rr_timeslice <= 0 ? RR_TIMESLICE :
3038 msecs_to_jiffies(sysctl_sched_rr_timeslice);
3039 }
3040 mutex_unlock(&mutex);
3041
3042 return ret;
3043 }
3044 #endif /* CONFIG_SYSCTL */
3045
3046 #ifdef CONFIG_SCHED_DEBUG
print_rt_stats(struct seq_file * m,int cpu)3047 void print_rt_stats(struct seq_file *m, int cpu)
3048 {
3049 rt_rq_iter_t iter;
3050 struct rt_rq *rt_rq;
3051
3052 rcu_read_lock();
3053 for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
3054 print_rt_rq(m, cpu, rt_rq);
3055 rcu_read_unlock();
3056 }
3057 #endif /* CONFIG_SCHED_DEBUG */
3058