1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * kernel/workqueue.c - generic async execution with shared worker pool
4 *
5 * Copyright (C) 2002 Ingo Molnar
6 *
7 * Derived from the taskqueue/keventd code by:
8 * David Woodhouse <dwmw2@infradead.org>
9 * Andrew Morton
10 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
11 * Theodore Ts'o <tytso@mit.edu>
12 *
13 * Made to use alloc_percpu by Christoph Lameter.
14 *
15 * Copyright (C) 2010 SUSE Linux Products GmbH
16 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
17 *
18 * This is the generic async execution mechanism. Work items as are
19 * executed in process context. The worker pool is shared and
20 * automatically managed. There are two worker pools for each CPU (one for
21 * normal work items and the other for high priority ones) and some extra
22 * pools for workqueues which are not bound to any specific CPU - the
23 * number of these backing pools is dynamic.
24 *
25 * Please read Documentation/core-api/workqueue.rst for details.
26 */
27
28 #include <linux/export.h>
29 #include <linux/kernel.h>
30 #include <linux/sched.h>
31 #include <linux/init.h>
32 #include <linux/signal.h>
33 #include <linux/completion.h>
34 #include <linux/workqueue.h>
35 #include <linux/slab.h>
36 #include <linux/cpu.h>
37 #include <linux/notifier.h>
38 #include <linux/kthread.h>
39 #include <linux/hardirq.h>
40 #include <linux/mempolicy.h>
41 #include <linux/freezer.h>
42 #include <linux/debug_locks.h>
43 #include <linux/lockdep.h>
44 #include <linux/idr.h>
45 #include <linux/jhash.h>
46 #include <linux/hashtable.h>
47 #include <linux/rculist.h>
48 #include <linux/nodemask.h>
49 #include <linux/moduleparam.h>
50 #include <linux/uaccess.h>
51 #include <linux/sched/isolation.h>
52 #include <linux/sched/debug.h>
53 #include <linux/nmi.h>
54 #include <linux/kvm_para.h>
55 #include <linux/delay.h>
56
57 #include "workqueue_internal.h"
58
59 enum {
60 /*
61 * worker_pool flags
62 *
63 * A bound pool is either associated or disassociated with its CPU.
64 * While associated (!DISASSOCIATED), all workers are bound to the
65 * CPU and none has %WORKER_UNBOUND set and concurrency management
66 * is in effect.
67 *
68 * While DISASSOCIATED, the cpu may be offline and all workers have
69 * %WORKER_UNBOUND set and concurrency management disabled, and may
70 * be executing on any CPU. The pool behaves as an unbound one.
71 *
72 * Note that DISASSOCIATED should be flipped only while holding
73 * wq_pool_attach_mutex to avoid changing binding state while
74 * worker_attach_to_pool() is in progress.
75 */
76 POOL_MANAGER_ACTIVE = 1 << 0, /* being managed */
77 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
78
79 /* worker flags */
80 WORKER_DIE = 1 << 1, /* die die die */
81 WORKER_IDLE = 1 << 2, /* is idle */
82 WORKER_PREP = 1 << 3, /* preparing to run works */
83 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
84 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
85 WORKER_REBOUND = 1 << 8, /* worker was rebound */
86
87 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE |
88 WORKER_UNBOUND | WORKER_REBOUND,
89
90 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
91
92 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
93 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
94
95 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
96 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
97
98 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
99 /* call for help after 10ms
100 (min two ticks) */
101 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
102 CREATE_COOLDOWN = HZ, /* time to breath after fail */
103
104 /*
105 * Rescue workers are used only on emergencies and shared by
106 * all cpus. Give MIN_NICE.
107 */
108 RESCUER_NICE_LEVEL = MIN_NICE,
109 HIGHPRI_NICE_LEVEL = MIN_NICE,
110
111 WQ_NAME_LEN = 24,
112 };
113
114 /*
115 * Structure fields follow one of the following exclusion rules.
116 *
117 * I: Modifiable by initialization/destruction paths and read-only for
118 * everyone else.
119 *
120 * P: Preemption protected. Disabling preemption is enough and should
121 * only be modified and accessed from the local cpu.
122 *
123 * L: pool->lock protected. Access with pool->lock held.
124 *
125 * K: Only modified by worker while holding pool->lock. Can be safely read by
126 * self, while holding pool->lock or from IRQ context if %current is the
127 * kworker.
128 *
129 * S: Only modified by worker self.
130 *
131 * A: wq_pool_attach_mutex protected.
132 *
133 * PL: wq_pool_mutex protected.
134 *
135 * PR: wq_pool_mutex protected for writes. RCU protected for reads.
136 *
137 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
138 *
139 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
140 * RCU for reads.
141 *
142 * WQ: wq->mutex protected.
143 *
144 * WR: wq->mutex protected for writes. RCU protected for reads.
145 *
146 * MD: wq_mayday_lock protected.
147 *
148 * WD: Used internally by the watchdog.
149 */
150
151 /* struct worker is defined in workqueue_internal.h */
152
153 struct worker_pool {
154 raw_spinlock_t lock; /* the pool lock */
155 int cpu; /* I: the associated cpu */
156 int node; /* I: the associated node ID */
157 int id; /* I: pool ID */
158 unsigned int flags; /* L: flags */
159
160 unsigned long watchdog_ts; /* L: watchdog timestamp */
161 bool cpu_stall; /* WD: stalled cpu bound pool */
162
163 /*
164 * The counter is incremented in a process context on the associated CPU
165 * w/ preemption disabled, and decremented or reset in the same context
166 * but w/ pool->lock held. The readers grab pool->lock and are
167 * guaranteed to see if the counter reached zero.
168 */
169 int nr_running;
170
171 struct list_head worklist; /* L: list of pending works */
172
173 int nr_workers; /* L: total number of workers */
174 int nr_idle; /* L: currently idle workers */
175
176 struct list_head idle_list; /* L: list of idle workers */
177 struct timer_list idle_timer; /* L: worker idle timeout */
178 struct work_struct idle_cull_work; /* L: worker idle cleanup */
179
180 struct timer_list mayday_timer; /* L: SOS timer for workers */
181
182 /* a workers is either on busy_hash or idle_list, or the manager */
183 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
184 /* L: hash of busy workers */
185
186 struct worker *manager; /* L: purely informational */
187 struct list_head workers; /* A: attached workers */
188 struct list_head dying_workers; /* A: workers about to die */
189 struct completion *detach_completion; /* all workers detached */
190
191 struct ida worker_ida; /* worker IDs for task name */
192
193 struct workqueue_attrs *attrs; /* I: worker attributes */
194 struct hlist_node hash_node; /* PL: unbound_pool_hash node */
195 int refcnt; /* PL: refcnt for unbound pools */
196
197 /*
198 * Destruction of pool is RCU protected to allow dereferences
199 * from get_work_pool().
200 */
201 struct rcu_head rcu;
202 };
203
204 /*
205 * Per-pool_workqueue statistics. These can be monitored using
206 * tools/workqueue/wq_monitor.py.
207 */
208 enum pool_workqueue_stats {
209 PWQ_STAT_STARTED, /* work items started execution */
210 PWQ_STAT_COMPLETED, /* work items completed execution */
211 PWQ_STAT_CPU_TIME, /* total CPU time consumed */
212 PWQ_STAT_CPU_INTENSIVE, /* wq_cpu_intensive_thresh_us violations */
213 PWQ_STAT_CM_WAKEUP, /* concurrency-management worker wakeups */
214 PWQ_STAT_REPATRIATED, /* unbound workers brought back into scope */
215 PWQ_STAT_MAYDAY, /* maydays to rescuer */
216 PWQ_STAT_RESCUED, /* linked work items executed by rescuer */
217
218 PWQ_NR_STATS,
219 };
220
221 /*
222 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
223 * of work_struct->data are used for flags and the remaining high bits
224 * point to the pwq; thus, pwqs need to be aligned at two's power of the
225 * number of flag bits.
226 */
227 struct pool_workqueue {
228 struct worker_pool *pool; /* I: the associated pool */
229 struct workqueue_struct *wq; /* I: the owning workqueue */
230 int work_color; /* L: current color */
231 int flush_color; /* L: flushing color */
232 int refcnt; /* L: reference count */
233 int nr_in_flight[WORK_NR_COLORS];
234 /* L: nr of in_flight works */
235
236 /*
237 * nr_active management and WORK_STRUCT_INACTIVE:
238 *
239 * When pwq->nr_active >= max_active, new work item is queued to
240 * pwq->inactive_works instead of pool->worklist and marked with
241 * WORK_STRUCT_INACTIVE.
242 *
243 * All work items marked with WORK_STRUCT_INACTIVE do not participate
244 * in pwq->nr_active and all work items in pwq->inactive_works are
245 * marked with WORK_STRUCT_INACTIVE. But not all WORK_STRUCT_INACTIVE
246 * work items are in pwq->inactive_works. Some of them are ready to
247 * run in pool->worklist or worker->scheduled. Those work itmes are
248 * only struct wq_barrier which is used for flush_work() and should
249 * not participate in pwq->nr_active. For non-barrier work item, it
250 * is marked with WORK_STRUCT_INACTIVE iff it is in pwq->inactive_works.
251 */
252 int nr_active; /* L: nr of active works */
253 int max_active; /* L: max active works */
254 struct list_head inactive_works; /* L: inactive works */
255 struct list_head pwqs_node; /* WR: node on wq->pwqs */
256 struct list_head mayday_node; /* MD: node on wq->maydays */
257
258 u64 stats[PWQ_NR_STATS];
259
260 /*
261 * Release of unbound pwq is punted to a kthread_worker. See put_pwq()
262 * and pwq_release_workfn() for details. pool_workqueue itself is also
263 * RCU protected so that the first pwq can be determined without
264 * grabbing wq->mutex.
265 */
266 struct kthread_work release_work;
267 struct rcu_head rcu;
268 } __aligned(1 << WORK_STRUCT_FLAG_BITS);
269
270 /*
271 * Structure used to wait for workqueue flush.
272 */
273 struct wq_flusher {
274 struct list_head list; /* WQ: list of flushers */
275 int flush_color; /* WQ: flush color waiting for */
276 struct completion done; /* flush completion */
277 };
278
279 struct wq_device;
280
281 /*
282 * The externally visible workqueue. It relays the issued work items to
283 * the appropriate worker_pool through its pool_workqueues.
284 */
285 struct workqueue_struct {
286 struct list_head pwqs; /* WR: all pwqs of this wq */
287 struct list_head list; /* PR: list of all workqueues */
288
289 struct mutex mutex; /* protects this wq */
290 int work_color; /* WQ: current work color */
291 int flush_color; /* WQ: current flush color */
292 atomic_t nr_pwqs_to_flush; /* flush in progress */
293 struct wq_flusher *first_flusher; /* WQ: first flusher */
294 struct list_head flusher_queue; /* WQ: flush waiters */
295 struct list_head flusher_overflow; /* WQ: flush overflow list */
296
297 struct list_head maydays; /* MD: pwqs requesting rescue */
298 struct worker *rescuer; /* MD: rescue worker */
299
300 int nr_drainers; /* WQ: drain in progress */
301 int saved_max_active; /* WQ: saved pwq max_active */
302
303 struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */
304 struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */
305
306 #ifdef CONFIG_SYSFS
307 struct wq_device *wq_dev; /* I: for sysfs interface */
308 #endif
309 #ifdef CONFIG_LOCKDEP
310 char *lock_name;
311 struct lock_class_key key;
312 struct lockdep_map lockdep_map;
313 #endif
314 char name[WQ_NAME_LEN]; /* I: workqueue name */
315
316 /*
317 * Destruction of workqueue_struct is RCU protected to allow walking
318 * the workqueues list without grabbing wq_pool_mutex.
319 * This is used to dump all workqueues from sysrq.
320 */
321 struct rcu_head rcu;
322
323 /* hot fields used during command issue, aligned to cacheline */
324 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
325 struct pool_workqueue __percpu __rcu **cpu_pwq; /* I: per-cpu pwqs */
326 };
327
328 static struct kmem_cache *pwq_cache;
329
330 /*
331 * Each pod type describes how CPUs should be grouped for unbound workqueues.
332 * See the comment above workqueue_attrs->affn_scope.
333 */
334 struct wq_pod_type {
335 int nr_pods; /* number of pods */
336 cpumask_var_t *pod_cpus; /* pod -> cpus */
337 int *pod_node; /* pod -> node */
338 int *cpu_pod; /* cpu -> pod */
339 };
340
341 static struct wq_pod_type wq_pod_types[WQ_AFFN_NR_TYPES];
342 static enum wq_affn_scope wq_affn_dfl = WQ_AFFN_CACHE;
343
344 static const char *wq_affn_names[WQ_AFFN_NR_TYPES] = {
345 [WQ_AFFN_DFL] = "default",
346 [WQ_AFFN_CPU] = "cpu",
347 [WQ_AFFN_SMT] = "smt",
348 [WQ_AFFN_CACHE] = "cache",
349 [WQ_AFFN_NUMA] = "numa",
350 [WQ_AFFN_SYSTEM] = "system",
351 };
352
353 /*
354 * Per-cpu work items which run for longer than the following threshold are
355 * automatically considered CPU intensive and excluded from concurrency
356 * management to prevent them from noticeably delaying other per-cpu work items.
357 * ULONG_MAX indicates that the user hasn't overridden it with a boot parameter.
358 * The actual value is initialized in wq_cpu_intensive_thresh_init().
359 */
360 static unsigned long wq_cpu_intensive_thresh_us = ULONG_MAX;
361 module_param_named(cpu_intensive_thresh_us, wq_cpu_intensive_thresh_us, ulong, 0644);
362
363 /* see the comment above the definition of WQ_POWER_EFFICIENT */
364 static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
365 module_param_named(power_efficient, wq_power_efficient, bool, 0444);
366
367 static bool wq_online; /* can kworkers be created yet? */
368
369 /* buf for wq_update_unbound_pod_attrs(), protected by CPU hotplug exclusion */
370 static struct workqueue_attrs *wq_update_pod_attrs_buf;
371
372 static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
373 static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
374 static DEFINE_RAW_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
375 /* wait for manager to go away */
376 static struct rcuwait manager_wait = __RCUWAIT_INITIALIZER(manager_wait);
377
378 static LIST_HEAD(workqueues); /* PR: list of all workqueues */
379 static bool workqueue_freezing; /* PL: have wqs started freezing? */
380
381 /* PL&A: allowable cpus for unbound wqs and work items */
382 static cpumask_var_t wq_unbound_cpumask;
383
384 /* for further constrain wq_unbound_cpumask by cmdline parameter*/
385 static struct cpumask wq_cmdline_cpumask __initdata;
386
387 /* CPU where unbound work was last round robin scheduled from this CPU */
388 static DEFINE_PER_CPU(int, wq_rr_cpu_last);
389
390 /*
391 * Local execution of unbound work items is no longer guaranteed. The
392 * following always forces round-robin CPU selection on unbound work items
393 * to uncover usages which depend on it.
394 */
395 #ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
396 static bool wq_debug_force_rr_cpu = true;
397 #else
398 static bool wq_debug_force_rr_cpu = false;
399 #endif
400 module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
401
402 /* the per-cpu worker pools */
403 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
404
405 static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
406
407 /* PL: hash of all unbound pools keyed by pool->attrs */
408 static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
409
410 /* I: attributes used when instantiating standard unbound pools on demand */
411 static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
412
413 /* I: attributes used when instantiating ordered pools on demand */
414 static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
415
416 /*
417 * I: kthread_worker to release pwq's. pwq release needs to be bounced to a
418 * process context while holding a pool lock. Bounce to a dedicated kthread
419 * worker to avoid A-A deadlocks.
420 */
421 static struct kthread_worker *pwq_release_worker;
422
423 struct workqueue_struct *system_wq __read_mostly;
424 EXPORT_SYMBOL(system_wq);
425 struct workqueue_struct *system_highpri_wq __read_mostly;
426 EXPORT_SYMBOL_GPL(system_highpri_wq);
427 struct workqueue_struct *system_long_wq __read_mostly;
428 EXPORT_SYMBOL_GPL(system_long_wq);
429 struct workqueue_struct *system_unbound_wq __read_mostly;
430 EXPORT_SYMBOL_GPL(system_unbound_wq);
431 struct workqueue_struct *system_freezable_wq __read_mostly;
432 EXPORT_SYMBOL_GPL(system_freezable_wq);
433 struct workqueue_struct *system_power_efficient_wq __read_mostly;
434 EXPORT_SYMBOL_GPL(system_power_efficient_wq);
435 struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
436 EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
437
438 static int worker_thread(void *__worker);
439 static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
440 static void show_pwq(struct pool_workqueue *pwq);
441 static void show_one_worker_pool(struct worker_pool *pool);
442
443 #define CREATE_TRACE_POINTS
444 #include <trace/events/workqueue.h>
445
446 #define assert_rcu_or_pool_mutex() \
447 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
448 !lockdep_is_held(&wq_pool_mutex), \
449 "RCU or wq_pool_mutex should be held")
450
451 #define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
452 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
453 !lockdep_is_held(&wq->mutex) && \
454 !lockdep_is_held(&wq_pool_mutex), \
455 "RCU, wq->mutex or wq_pool_mutex should be held")
456
457 #define for_each_cpu_worker_pool(pool, cpu) \
458 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
459 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
460 (pool)++)
461
462 /**
463 * for_each_pool - iterate through all worker_pools in the system
464 * @pool: iteration cursor
465 * @pi: integer used for iteration
466 *
467 * This must be called either with wq_pool_mutex held or RCU read
468 * locked. If the pool needs to be used beyond the locking in effect, the
469 * caller is responsible for guaranteeing that the pool stays online.
470 *
471 * The if/else clause exists only for the lockdep assertion and can be
472 * ignored.
473 */
474 #define for_each_pool(pool, pi) \
475 idr_for_each_entry(&worker_pool_idr, pool, pi) \
476 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
477 else
478
479 /**
480 * for_each_pool_worker - iterate through all workers of a worker_pool
481 * @worker: iteration cursor
482 * @pool: worker_pool to iterate workers of
483 *
484 * This must be called with wq_pool_attach_mutex.
485 *
486 * The if/else clause exists only for the lockdep assertion and can be
487 * ignored.
488 */
489 #define for_each_pool_worker(worker, pool) \
490 list_for_each_entry((worker), &(pool)->workers, node) \
491 if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
492 else
493
494 /**
495 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
496 * @pwq: iteration cursor
497 * @wq: the target workqueue
498 *
499 * This must be called either with wq->mutex held or RCU read locked.
500 * If the pwq needs to be used beyond the locking in effect, the caller is
501 * responsible for guaranteeing that the pwq stays online.
502 *
503 * The if/else clause exists only for the lockdep assertion and can be
504 * ignored.
505 */
506 #define for_each_pwq(pwq, wq) \
507 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node, \
508 lockdep_is_held(&(wq->mutex)))
509
510 #ifdef CONFIG_DEBUG_OBJECTS_WORK
511
512 static const struct debug_obj_descr work_debug_descr;
513
work_debug_hint(void * addr)514 static void *work_debug_hint(void *addr)
515 {
516 return ((struct work_struct *) addr)->func;
517 }
518
work_is_static_object(void * addr)519 static bool work_is_static_object(void *addr)
520 {
521 struct work_struct *work = addr;
522
523 return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
524 }
525
526 /*
527 * fixup_init is called when:
528 * - an active object is initialized
529 */
work_fixup_init(void * addr,enum debug_obj_state state)530 static bool work_fixup_init(void *addr, enum debug_obj_state state)
531 {
532 struct work_struct *work = addr;
533
534 switch (state) {
535 case ODEBUG_STATE_ACTIVE:
536 cancel_work_sync(work);
537 debug_object_init(work, &work_debug_descr);
538 return true;
539 default:
540 return false;
541 }
542 }
543
544 /*
545 * fixup_free is called when:
546 * - an active object is freed
547 */
work_fixup_free(void * addr,enum debug_obj_state state)548 static bool work_fixup_free(void *addr, enum debug_obj_state state)
549 {
550 struct work_struct *work = addr;
551
552 switch (state) {
553 case ODEBUG_STATE_ACTIVE:
554 cancel_work_sync(work);
555 debug_object_free(work, &work_debug_descr);
556 return true;
557 default:
558 return false;
559 }
560 }
561
562 static const struct debug_obj_descr work_debug_descr = {
563 .name = "work_struct",
564 .debug_hint = work_debug_hint,
565 .is_static_object = work_is_static_object,
566 .fixup_init = work_fixup_init,
567 .fixup_free = work_fixup_free,
568 };
569
debug_work_activate(struct work_struct * work)570 static inline void debug_work_activate(struct work_struct *work)
571 {
572 debug_object_activate(work, &work_debug_descr);
573 }
574
debug_work_deactivate(struct work_struct * work)575 static inline void debug_work_deactivate(struct work_struct *work)
576 {
577 debug_object_deactivate(work, &work_debug_descr);
578 }
579
__init_work(struct work_struct * work,int onstack)580 void __init_work(struct work_struct *work, int onstack)
581 {
582 if (onstack)
583 debug_object_init_on_stack(work, &work_debug_descr);
584 else
585 debug_object_init(work, &work_debug_descr);
586 }
587 EXPORT_SYMBOL_GPL(__init_work);
588
destroy_work_on_stack(struct work_struct * work)589 void destroy_work_on_stack(struct work_struct *work)
590 {
591 debug_object_free(work, &work_debug_descr);
592 }
593 EXPORT_SYMBOL_GPL(destroy_work_on_stack);
594
destroy_delayed_work_on_stack(struct delayed_work * work)595 void destroy_delayed_work_on_stack(struct delayed_work *work)
596 {
597 destroy_timer_on_stack(&work->timer);
598 debug_object_free(&work->work, &work_debug_descr);
599 }
600 EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
601
602 #else
debug_work_activate(struct work_struct * work)603 static inline void debug_work_activate(struct work_struct *work) { }
debug_work_deactivate(struct work_struct * work)604 static inline void debug_work_deactivate(struct work_struct *work) { }
605 #endif
606
607 /**
608 * worker_pool_assign_id - allocate ID and assign it to @pool
609 * @pool: the pool pointer of interest
610 *
611 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
612 * successfully, -errno on failure.
613 */
worker_pool_assign_id(struct worker_pool * pool)614 static int worker_pool_assign_id(struct worker_pool *pool)
615 {
616 int ret;
617
618 lockdep_assert_held(&wq_pool_mutex);
619
620 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
621 GFP_KERNEL);
622 if (ret >= 0) {
623 pool->id = ret;
624 return 0;
625 }
626 return ret;
627 }
628
work_color_to_flags(int color)629 static unsigned int work_color_to_flags(int color)
630 {
631 return color << WORK_STRUCT_COLOR_SHIFT;
632 }
633
get_work_color(unsigned long work_data)634 static int get_work_color(unsigned long work_data)
635 {
636 return (work_data >> WORK_STRUCT_COLOR_SHIFT) &
637 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
638 }
639
work_next_color(int color)640 static int work_next_color(int color)
641 {
642 return (color + 1) % WORK_NR_COLORS;
643 }
644
645 /*
646 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
647 * contain the pointer to the queued pwq. Once execution starts, the flag
648 * is cleared and the high bits contain OFFQ flags and pool ID.
649 *
650 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
651 * and clear_work_data() can be used to set the pwq, pool or clear
652 * work->data. These functions should only be called while the work is
653 * owned - ie. while the PENDING bit is set.
654 *
655 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
656 * corresponding to a work. Pool is available once the work has been
657 * queued anywhere after initialization until it is sync canceled. pwq is
658 * available only while the work item is queued.
659 *
660 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
661 * canceled. While being canceled, a work item may have its PENDING set
662 * but stay off timer and worklist for arbitrarily long and nobody should
663 * try to steal the PENDING bit.
664 */
set_work_data(struct work_struct * work,unsigned long data,unsigned long flags)665 static inline void set_work_data(struct work_struct *work, unsigned long data,
666 unsigned long flags)
667 {
668 WARN_ON_ONCE(!work_pending(work));
669 atomic_long_set(&work->data, data | flags | work_static(work));
670 }
671
set_work_pwq(struct work_struct * work,struct pool_workqueue * pwq,unsigned long extra_flags)672 static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
673 unsigned long extra_flags)
674 {
675 set_work_data(work, (unsigned long)pwq,
676 WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
677 }
678
set_work_pool_and_keep_pending(struct work_struct * work,int pool_id)679 static void set_work_pool_and_keep_pending(struct work_struct *work,
680 int pool_id)
681 {
682 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
683 WORK_STRUCT_PENDING);
684 }
685
set_work_pool_and_clear_pending(struct work_struct * work,int pool_id)686 static void set_work_pool_and_clear_pending(struct work_struct *work,
687 int pool_id)
688 {
689 /*
690 * The following wmb is paired with the implied mb in
691 * test_and_set_bit(PENDING) and ensures all updates to @work made
692 * here are visible to and precede any updates by the next PENDING
693 * owner.
694 */
695 smp_wmb();
696 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
697 /*
698 * The following mb guarantees that previous clear of a PENDING bit
699 * will not be reordered with any speculative LOADS or STORES from
700 * work->current_func, which is executed afterwards. This possible
701 * reordering can lead to a missed execution on attempt to queue
702 * the same @work. E.g. consider this case:
703 *
704 * CPU#0 CPU#1
705 * ---------------------------- --------------------------------
706 *
707 * 1 STORE event_indicated
708 * 2 queue_work_on() {
709 * 3 test_and_set_bit(PENDING)
710 * 4 } set_..._and_clear_pending() {
711 * 5 set_work_data() # clear bit
712 * 6 smp_mb()
713 * 7 work->current_func() {
714 * 8 LOAD event_indicated
715 * }
716 *
717 * Without an explicit full barrier speculative LOAD on line 8 can
718 * be executed before CPU#0 does STORE on line 1. If that happens,
719 * CPU#0 observes the PENDING bit is still set and new execution of
720 * a @work is not queued in a hope, that CPU#1 will eventually
721 * finish the queued @work. Meanwhile CPU#1 does not see
722 * event_indicated is set, because speculative LOAD was executed
723 * before actual STORE.
724 */
725 smp_mb();
726 }
727
clear_work_data(struct work_struct * work)728 static void clear_work_data(struct work_struct *work)
729 {
730 smp_wmb(); /* see set_work_pool_and_clear_pending() */
731 set_work_data(work, WORK_STRUCT_NO_POOL, 0);
732 }
733
work_struct_pwq(unsigned long data)734 static inline struct pool_workqueue *work_struct_pwq(unsigned long data)
735 {
736 return (struct pool_workqueue *)(data & WORK_STRUCT_WQ_DATA_MASK);
737 }
738
get_work_pwq(struct work_struct * work)739 static struct pool_workqueue *get_work_pwq(struct work_struct *work)
740 {
741 unsigned long data = atomic_long_read(&work->data);
742
743 if (data & WORK_STRUCT_PWQ)
744 return work_struct_pwq(data);
745 else
746 return NULL;
747 }
748
749 /**
750 * get_work_pool - return the worker_pool a given work was associated with
751 * @work: the work item of interest
752 *
753 * Pools are created and destroyed under wq_pool_mutex, and allows read
754 * access under RCU read lock. As such, this function should be
755 * called under wq_pool_mutex or inside of a rcu_read_lock() region.
756 *
757 * All fields of the returned pool are accessible as long as the above
758 * mentioned locking is in effect. If the returned pool needs to be used
759 * beyond the critical section, the caller is responsible for ensuring the
760 * returned pool is and stays online.
761 *
762 * Return: The worker_pool @work was last associated with. %NULL if none.
763 */
get_work_pool(struct work_struct * work)764 static struct worker_pool *get_work_pool(struct work_struct *work)
765 {
766 unsigned long data = atomic_long_read(&work->data);
767 int pool_id;
768
769 assert_rcu_or_pool_mutex();
770
771 if (data & WORK_STRUCT_PWQ)
772 return work_struct_pwq(data)->pool;
773
774 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
775 if (pool_id == WORK_OFFQ_POOL_NONE)
776 return NULL;
777
778 return idr_find(&worker_pool_idr, pool_id);
779 }
780
781 /**
782 * get_work_pool_id - return the worker pool ID a given work is associated with
783 * @work: the work item of interest
784 *
785 * Return: The worker_pool ID @work was last associated with.
786 * %WORK_OFFQ_POOL_NONE if none.
787 */
get_work_pool_id(struct work_struct * work)788 static int get_work_pool_id(struct work_struct *work)
789 {
790 unsigned long data = atomic_long_read(&work->data);
791
792 if (data & WORK_STRUCT_PWQ)
793 return work_struct_pwq(data)->pool->id;
794
795 return data >> WORK_OFFQ_POOL_SHIFT;
796 }
797
mark_work_canceling(struct work_struct * work)798 static void mark_work_canceling(struct work_struct *work)
799 {
800 unsigned long pool_id = get_work_pool_id(work);
801
802 pool_id <<= WORK_OFFQ_POOL_SHIFT;
803 set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
804 }
805
work_is_canceling(struct work_struct * work)806 static bool work_is_canceling(struct work_struct *work)
807 {
808 unsigned long data = atomic_long_read(&work->data);
809
810 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
811 }
812
813 /*
814 * Policy functions. These define the policies on how the global worker
815 * pools are managed. Unless noted otherwise, these functions assume that
816 * they're being called with pool->lock held.
817 */
818
819 /*
820 * Need to wake up a worker? Called from anything but currently
821 * running workers.
822 *
823 * Note that, because unbound workers never contribute to nr_running, this
824 * function will always return %true for unbound pools as long as the
825 * worklist isn't empty.
826 */
need_more_worker(struct worker_pool * pool)827 static bool need_more_worker(struct worker_pool *pool)
828 {
829 return !list_empty(&pool->worklist) && !pool->nr_running;
830 }
831
832 /* Can I start working? Called from busy but !running workers. */
may_start_working(struct worker_pool * pool)833 static bool may_start_working(struct worker_pool *pool)
834 {
835 return pool->nr_idle;
836 }
837
838 /* Do I need to keep working? Called from currently running workers. */
keep_working(struct worker_pool * pool)839 static bool keep_working(struct worker_pool *pool)
840 {
841 return !list_empty(&pool->worklist) && (pool->nr_running <= 1);
842 }
843
844 /* Do we need a new worker? Called from manager. */
need_to_create_worker(struct worker_pool * pool)845 static bool need_to_create_worker(struct worker_pool *pool)
846 {
847 return need_more_worker(pool) && !may_start_working(pool);
848 }
849
850 /* Do we have too many workers and should some go away? */
too_many_workers(struct worker_pool * pool)851 static bool too_many_workers(struct worker_pool *pool)
852 {
853 bool managing = pool->flags & POOL_MANAGER_ACTIVE;
854 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
855 int nr_busy = pool->nr_workers - nr_idle;
856
857 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
858 }
859
860 /**
861 * worker_set_flags - set worker flags and adjust nr_running accordingly
862 * @worker: self
863 * @flags: flags to set
864 *
865 * Set @flags in @worker->flags and adjust nr_running accordingly.
866 */
worker_set_flags(struct worker * worker,unsigned int flags)867 static inline void worker_set_flags(struct worker *worker, unsigned int flags)
868 {
869 struct worker_pool *pool = worker->pool;
870
871 lockdep_assert_held(&pool->lock);
872
873 /* If transitioning into NOT_RUNNING, adjust nr_running. */
874 if ((flags & WORKER_NOT_RUNNING) &&
875 !(worker->flags & WORKER_NOT_RUNNING)) {
876 pool->nr_running--;
877 }
878
879 worker->flags |= flags;
880 }
881
882 /**
883 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
884 * @worker: self
885 * @flags: flags to clear
886 *
887 * Clear @flags in @worker->flags and adjust nr_running accordingly.
888 */
worker_clr_flags(struct worker * worker,unsigned int flags)889 static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
890 {
891 struct worker_pool *pool = worker->pool;
892 unsigned int oflags = worker->flags;
893
894 lockdep_assert_held(&pool->lock);
895
896 worker->flags &= ~flags;
897
898 /*
899 * If transitioning out of NOT_RUNNING, increment nr_running. Note
900 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
901 * of multiple flags, not a single flag.
902 */
903 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
904 if (!(worker->flags & WORKER_NOT_RUNNING))
905 pool->nr_running++;
906 }
907
908 /* Return the first idle worker. Called with pool->lock held. */
first_idle_worker(struct worker_pool * pool)909 static struct worker *first_idle_worker(struct worker_pool *pool)
910 {
911 if (unlikely(list_empty(&pool->idle_list)))
912 return NULL;
913
914 return list_first_entry(&pool->idle_list, struct worker, entry);
915 }
916
917 /**
918 * worker_enter_idle - enter idle state
919 * @worker: worker which is entering idle state
920 *
921 * @worker is entering idle state. Update stats and idle timer if
922 * necessary.
923 *
924 * LOCKING:
925 * raw_spin_lock_irq(pool->lock).
926 */
worker_enter_idle(struct worker * worker)927 static void worker_enter_idle(struct worker *worker)
928 {
929 struct worker_pool *pool = worker->pool;
930
931 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
932 WARN_ON_ONCE(!list_empty(&worker->entry) &&
933 (worker->hentry.next || worker->hentry.pprev)))
934 return;
935
936 /* can't use worker_set_flags(), also called from create_worker() */
937 worker->flags |= WORKER_IDLE;
938 pool->nr_idle++;
939 worker->last_active = jiffies;
940
941 /* idle_list is LIFO */
942 list_add(&worker->entry, &pool->idle_list);
943
944 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
945 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
946
947 /* Sanity check nr_running. */
948 WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running);
949 }
950
951 /**
952 * worker_leave_idle - leave idle state
953 * @worker: worker which is leaving idle state
954 *
955 * @worker is leaving idle state. Update stats.
956 *
957 * LOCKING:
958 * raw_spin_lock_irq(pool->lock).
959 */
worker_leave_idle(struct worker * worker)960 static void worker_leave_idle(struct worker *worker)
961 {
962 struct worker_pool *pool = worker->pool;
963
964 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
965 return;
966 worker_clr_flags(worker, WORKER_IDLE);
967 pool->nr_idle--;
968 list_del_init(&worker->entry);
969 }
970
971 /**
972 * find_worker_executing_work - find worker which is executing a work
973 * @pool: pool of interest
974 * @work: work to find worker for
975 *
976 * Find a worker which is executing @work on @pool by searching
977 * @pool->busy_hash which is keyed by the address of @work. For a worker
978 * to match, its current execution should match the address of @work and
979 * its work function. This is to avoid unwanted dependency between
980 * unrelated work executions through a work item being recycled while still
981 * being executed.
982 *
983 * This is a bit tricky. A work item may be freed once its execution
984 * starts and nothing prevents the freed area from being recycled for
985 * another work item. If the same work item address ends up being reused
986 * before the original execution finishes, workqueue will identify the
987 * recycled work item as currently executing and make it wait until the
988 * current execution finishes, introducing an unwanted dependency.
989 *
990 * This function checks the work item address and work function to avoid
991 * false positives. Note that this isn't complete as one may construct a
992 * work function which can introduce dependency onto itself through a
993 * recycled work item. Well, if somebody wants to shoot oneself in the
994 * foot that badly, there's only so much we can do, and if such deadlock
995 * actually occurs, it should be easy to locate the culprit work function.
996 *
997 * CONTEXT:
998 * raw_spin_lock_irq(pool->lock).
999 *
1000 * Return:
1001 * Pointer to worker which is executing @work if found, %NULL
1002 * otherwise.
1003 */
find_worker_executing_work(struct worker_pool * pool,struct work_struct * work)1004 static struct worker *find_worker_executing_work(struct worker_pool *pool,
1005 struct work_struct *work)
1006 {
1007 struct worker *worker;
1008
1009 hash_for_each_possible(pool->busy_hash, worker, hentry,
1010 (unsigned long)work)
1011 if (worker->current_work == work &&
1012 worker->current_func == work->func)
1013 return worker;
1014
1015 return NULL;
1016 }
1017
1018 /**
1019 * move_linked_works - move linked works to a list
1020 * @work: start of series of works to be scheduled
1021 * @head: target list to append @work to
1022 * @nextp: out parameter for nested worklist walking
1023 *
1024 * Schedule linked works starting from @work to @head. Work series to be
1025 * scheduled starts at @work and includes any consecutive work with
1026 * WORK_STRUCT_LINKED set in its predecessor. See assign_work() for details on
1027 * @nextp.
1028 *
1029 * CONTEXT:
1030 * raw_spin_lock_irq(pool->lock).
1031 */
move_linked_works(struct work_struct * work,struct list_head * head,struct work_struct ** nextp)1032 static void move_linked_works(struct work_struct *work, struct list_head *head,
1033 struct work_struct **nextp)
1034 {
1035 struct work_struct *n;
1036
1037 /*
1038 * Linked worklist will always end before the end of the list,
1039 * use NULL for list head.
1040 */
1041 list_for_each_entry_safe_from(work, n, NULL, entry) {
1042 list_move_tail(&work->entry, head);
1043 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1044 break;
1045 }
1046
1047 /*
1048 * If we're already inside safe list traversal and have moved
1049 * multiple works to the scheduled queue, the next position
1050 * needs to be updated.
1051 */
1052 if (nextp)
1053 *nextp = n;
1054 }
1055
1056 /**
1057 * assign_work - assign a work item and its linked work items to a worker
1058 * @work: work to assign
1059 * @worker: worker to assign to
1060 * @nextp: out parameter for nested worklist walking
1061 *
1062 * Assign @work and its linked work items to @worker. If @work is already being
1063 * executed by another worker in the same pool, it'll be punted there.
1064 *
1065 * If @nextp is not NULL, it's updated to point to the next work of the last
1066 * scheduled work. This allows assign_work() to be nested inside
1067 * list_for_each_entry_safe().
1068 *
1069 * Returns %true if @work was successfully assigned to @worker. %false if @work
1070 * was punted to another worker already executing it.
1071 */
assign_work(struct work_struct * work,struct worker * worker,struct work_struct ** nextp)1072 static bool assign_work(struct work_struct *work, struct worker *worker,
1073 struct work_struct **nextp)
1074 {
1075 struct worker_pool *pool = worker->pool;
1076 struct worker *collision;
1077
1078 lockdep_assert_held(&pool->lock);
1079
1080 /*
1081 * A single work shouldn't be executed concurrently by multiple workers.
1082 * __queue_work() ensures that @work doesn't jump to a different pool
1083 * while still running in the previous pool. Here, we should ensure that
1084 * @work is not executed concurrently by multiple workers from the same
1085 * pool. Check whether anyone is already processing the work. If so,
1086 * defer the work to the currently executing one.
1087 */
1088 collision = find_worker_executing_work(pool, work);
1089 if (unlikely(collision)) {
1090 move_linked_works(work, &collision->scheduled, nextp);
1091 return false;
1092 }
1093
1094 move_linked_works(work, &worker->scheduled, nextp);
1095 return true;
1096 }
1097
1098 /**
1099 * kick_pool - wake up an idle worker if necessary
1100 * @pool: pool to kick
1101 *
1102 * @pool may have pending work items. Wake up worker if necessary. Returns
1103 * whether a worker was woken up.
1104 */
kick_pool(struct worker_pool * pool)1105 static bool kick_pool(struct worker_pool *pool)
1106 {
1107 struct worker *worker = first_idle_worker(pool);
1108 struct task_struct *p;
1109
1110 lockdep_assert_held(&pool->lock);
1111
1112 if (!need_more_worker(pool) || !worker)
1113 return false;
1114
1115 p = worker->task;
1116
1117 #ifdef CONFIG_SMP
1118 /*
1119 * Idle @worker is about to execute @work and waking up provides an
1120 * opportunity to migrate @worker at a lower cost by setting the task's
1121 * wake_cpu field. Let's see if we want to move @worker to improve
1122 * execution locality.
1123 *
1124 * We're waking the worker that went idle the latest and there's some
1125 * chance that @worker is marked idle but hasn't gone off CPU yet. If
1126 * so, setting the wake_cpu won't do anything. As this is a best-effort
1127 * optimization and the race window is narrow, let's leave as-is for
1128 * now. If this becomes pronounced, we can skip over workers which are
1129 * still on cpu when picking an idle worker.
1130 *
1131 * If @pool has non-strict affinity, @worker might have ended up outside
1132 * its affinity scope. Repatriate.
1133 */
1134 if (!pool->attrs->affn_strict &&
1135 !cpumask_test_cpu(p->wake_cpu, pool->attrs->__pod_cpumask)) {
1136 struct work_struct *work = list_first_entry(&pool->worklist,
1137 struct work_struct, entry);
1138 p->wake_cpu = cpumask_any_distribute(pool->attrs->__pod_cpumask);
1139 get_work_pwq(work)->stats[PWQ_STAT_REPATRIATED]++;
1140 }
1141 #endif
1142 wake_up_process(p);
1143 return true;
1144 }
1145
1146 #ifdef CONFIG_WQ_CPU_INTENSIVE_REPORT
1147
1148 /*
1149 * Concurrency-managed per-cpu work items that hog CPU for longer than
1150 * wq_cpu_intensive_thresh_us trigger the automatic CPU_INTENSIVE mechanism,
1151 * which prevents them from stalling other concurrency-managed work items. If a
1152 * work function keeps triggering this mechanism, it's likely that the work item
1153 * should be using an unbound workqueue instead.
1154 *
1155 * wq_cpu_intensive_report() tracks work functions which trigger such conditions
1156 * and report them so that they can be examined and converted to use unbound
1157 * workqueues as appropriate. To avoid flooding the console, each violating work
1158 * function is tracked and reported with exponential backoff.
1159 */
1160 #define WCI_MAX_ENTS 128
1161
1162 struct wci_ent {
1163 work_func_t func;
1164 atomic64_t cnt;
1165 struct hlist_node hash_node;
1166 };
1167
1168 static struct wci_ent wci_ents[WCI_MAX_ENTS];
1169 static int wci_nr_ents;
1170 static DEFINE_RAW_SPINLOCK(wci_lock);
1171 static DEFINE_HASHTABLE(wci_hash, ilog2(WCI_MAX_ENTS));
1172
wci_find_ent(work_func_t func)1173 static struct wci_ent *wci_find_ent(work_func_t func)
1174 {
1175 struct wci_ent *ent;
1176
1177 hash_for_each_possible_rcu(wci_hash, ent, hash_node,
1178 (unsigned long)func) {
1179 if (ent->func == func)
1180 return ent;
1181 }
1182 return NULL;
1183 }
1184
wq_cpu_intensive_report(work_func_t func)1185 static void wq_cpu_intensive_report(work_func_t func)
1186 {
1187 struct wci_ent *ent;
1188
1189 restart:
1190 ent = wci_find_ent(func);
1191 if (ent) {
1192 u64 cnt;
1193
1194 /*
1195 * Start reporting from the fourth time and back off
1196 * exponentially.
1197 */
1198 cnt = atomic64_inc_return_relaxed(&ent->cnt);
1199 if (cnt >= 4 && is_power_of_2(cnt))
1200 printk_deferred(KERN_WARNING "workqueue: %ps hogged CPU for >%luus %llu times, consider switching to WQ_UNBOUND\n",
1201 ent->func, wq_cpu_intensive_thresh_us,
1202 atomic64_read(&ent->cnt));
1203 return;
1204 }
1205
1206 /*
1207 * @func is a new violation. Allocate a new entry for it. If wcn_ents[]
1208 * is exhausted, something went really wrong and we probably made enough
1209 * noise already.
1210 */
1211 if (wci_nr_ents >= WCI_MAX_ENTS)
1212 return;
1213
1214 raw_spin_lock(&wci_lock);
1215
1216 if (wci_nr_ents >= WCI_MAX_ENTS) {
1217 raw_spin_unlock(&wci_lock);
1218 return;
1219 }
1220
1221 if (wci_find_ent(func)) {
1222 raw_spin_unlock(&wci_lock);
1223 goto restart;
1224 }
1225
1226 ent = &wci_ents[wci_nr_ents++];
1227 ent->func = func;
1228 atomic64_set(&ent->cnt, 1);
1229 hash_add_rcu(wci_hash, &ent->hash_node, (unsigned long)func);
1230
1231 raw_spin_unlock(&wci_lock);
1232 }
1233
1234 #else /* CONFIG_WQ_CPU_INTENSIVE_REPORT */
wq_cpu_intensive_report(work_func_t func)1235 static void wq_cpu_intensive_report(work_func_t func) {}
1236 #endif /* CONFIG_WQ_CPU_INTENSIVE_REPORT */
1237
1238 /**
1239 * wq_worker_running - a worker is running again
1240 * @task: task waking up
1241 *
1242 * This function is called when a worker returns from schedule()
1243 */
wq_worker_running(struct task_struct * task)1244 void wq_worker_running(struct task_struct *task)
1245 {
1246 struct worker *worker = kthread_data(task);
1247
1248 if (!READ_ONCE(worker->sleeping))
1249 return;
1250
1251 /*
1252 * If preempted by unbind_workers() between the WORKER_NOT_RUNNING check
1253 * and the nr_running increment below, we may ruin the nr_running reset
1254 * and leave with an unexpected pool->nr_running == 1 on the newly unbound
1255 * pool. Protect against such race.
1256 */
1257 preempt_disable();
1258 if (!(worker->flags & WORKER_NOT_RUNNING))
1259 worker->pool->nr_running++;
1260 preempt_enable();
1261
1262 /*
1263 * CPU intensive auto-detection cares about how long a work item hogged
1264 * CPU without sleeping. Reset the starting timestamp on wakeup.
1265 */
1266 worker->current_at = worker->task->se.sum_exec_runtime;
1267
1268 WRITE_ONCE(worker->sleeping, 0);
1269 }
1270
1271 /**
1272 * wq_worker_sleeping - a worker is going to sleep
1273 * @task: task going to sleep
1274 *
1275 * This function is called from schedule() when a busy worker is
1276 * going to sleep.
1277 */
wq_worker_sleeping(struct task_struct * task)1278 void wq_worker_sleeping(struct task_struct *task)
1279 {
1280 struct worker *worker = kthread_data(task);
1281 struct worker_pool *pool;
1282
1283 /*
1284 * Rescuers, which may not have all the fields set up like normal
1285 * workers, also reach here, let's not access anything before
1286 * checking NOT_RUNNING.
1287 */
1288 if (worker->flags & WORKER_NOT_RUNNING)
1289 return;
1290
1291 pool = worker->pool;
1292
1293 /* Return if preempted before wq_worker_running() was reached */
1294 if (READ_ONCE(worker->sleeping))
1295 return;
1296
1297 WRITE_ONCE(worker->sleeping, 1);
1298 raw_spin_lock_irq(&pool->lock);
1299
1300 /*
1301 * Recheck in case unbind_workers() preempted us. We don't
1302 * want to decrement nr_running after the worker is unbound
1303 * and nr_running has been reset.
1304 */
1305 if (worker->flags & WORKER_NOT_RUNNING) {
1306 raw_spin_unlock_irq(&pool->lock);
1307 return;
1308 }
1309
1310 pool->nr_running--;
1311 if (kick_pool(pool))
1312 worker->current_pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1313
1314 raw_spin_unlock_irq(&pool->lock);
1315 }
1316
1317 /**
1318 * wq_worker_tick - a scheduler tick occurred while a kworker is running
1319 * @task: task currently running
1320 *
1321 * Called from scheduler_tick(). We're in the IRQ context and the current
1322 * worker's fields which follow the 'K' locking rule can be accessed safely.
1323 */
wq_worker_tick(struct task_struct * task)1324 void wq_worker_tick(struct task_struct *task)
1325 {
1326 struct worker *worker = kthread_data(task);
1327 struct pool_workqueue *pwq = worker->current_pwq;
1328 struct worker_pool *pool = worker->pool;
1329
1330 if (!pwq)
1331 return;
1332
1333 pwq->stats[PWQ_STAT_CPU_TIME] += TICK_USEC;
1334
1335 if (!wq_cpu_intensive_thresh_us)
1336 return;
1337
1338 /*
1339 * If the current worker is concurrency managed and hogged the CPU for
1340 * longer than wq_cpu_intensive_thresh_us, it's automatically marked
1341 * CPU_INTENSIVE to avoid stalling other concurrency-managed work items.
1342 *
1343 * Set @worker->sleeping means that @worker is in the process of
1344 * switching out voluntarily and won't be contributing to
1345 * @pool->nr_running until it wakes up. As wq_worker_sleeping() also
1346 * decrements ->nr_running, setting CPU_INTENSIVE here can lead to
1347 * double decrements. The task is releasing the CPU anyway. Let's skip.
1348 * We probably want to make this prettier in the future.
1349 */
1350 if ((worker->flags & WORKER_NOT_RUNNING) || READ_ONCE(worker->sleeping) ||
1351 worker->task->se.sum_exec_runtime - worker->current_at <
1352 wq_cpu_intensive_thresh_us * NSEC_PER_USEC)
1353 return;
1354
1355 raw_spin_lock(&pool->lock);
1356
1357 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
1358 wq_cpu_intensive_report(worker->current_func);
1359 pwq->stats[PWQ_STAT_CPU_INTENSIVE]++;
1360
1361 if (kick_pool(pool))
1362 pwq->stats[PWQ_STAT_CM_WAKEUP]++;
1363
1364 raw_spin_unlock(&pool->lock);
1365 }
1366
1367 /**
1368 * wq_worker_last_func - retrieve worker's last work function
1369 * @task: Task to retrieve last work function of.
1370 *
1371 * Determine the last function a worker executed. This is called from
1372 * the scheduler to get a worker's last known identity.
1373 *
1374 * CONTEXT:
1375 * raw_spin_lock_irq(rq->lock)
1376 *
1377 * This function is called during schedule() when a kworker is going
1378 * to sleep. It's used by psi to identify aggregation workers during
1379 * dequeuing, to allow periodic aggregation to shut-off when that
1380 * worker is the last task in the system or cgroup to go to sleep.
1381 *
1382 * As this function doesn't involve any workqueue-related locking, it
1383 * only returns stable values when called from inside the scheduler's
1384 * queuing and dequeuing paths, when @task, which must be a kworker,
1385 * is guaranteed to not be processing any works.
1386 *
1387 * Return:
1388 * The last work function %current executed as a worker, NULL if it
1389 * hasn't executed any work yet.
1390 */
wq_worker_last_func(struct task_struct * task)1391 work_func_t wq_worker_last_func(struct task_struct *task)
1392 {
1393 struct worker *worker = kthread_data(task);
1394
1395 return worker->last_func;
1396 }
1397
1398 /**
1399 * get_pwq - get an extra reference on the specified pool_workqueue
1400 * @pwq: pool_workqueue to get
1401 *
1402 * Obtain an extra reference on @pwq. The caller should guarantee that
1403 * @pwq has positive refcnt and be holding the matching pool->lock.
1404 */
get_pwq(struct pool_workqueue * pwq)1405 static void get_pwq(struct pool_workqueue *pwq)
1406 {
1407 lockdep_assert_held(&pwq->pool->lock);
1408 WARN_ON_ONCE(pwq->refcnt <= 0);
1409 pwq->refcnt++;
1410 }
1411
1412 /**
1413 * put_pwq - put a pool_workqueue reference
1414 * @pwq: pool_workqueue to put
1415 *
1416 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1417 * destruction. The caller should be holding the matching pool->lock.
1418 */
put_pwq(struct pool_workqueue * pwq)1419 static void put_pwq(struct pool_workqueue *pwq)
1420 {
1421 lockdep_assert_held(&pwq->pool->lock);
1422 if (likely(--pwq->refcnt))
1423 return;
1424 /*
1425 * @pwq can't be released under pool->lock, bounce to a dedicated
1426 * kthread_worker to avoid A-A deadlocks.
1427 */
1428 kthread_queue_work(pwq_release_worker, &pwq->release_work);
1429 }
1430
1431 /**
1432 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1433 * @pwq: pool_workqueue to put (can be %NULL)
1434 *
1435 * put_pwq() with locking. This function also allows %NULL @pwq.
1436 */
put_pwq_unlocked(struct pool_workqueue * pwq)1437 static void put_pwq_unlocked(struct pool_workqueue *pwq)
1438 {
1439 if (pwq) {
1440 /*
1441 * As both pwqs and pools are RCU protected, the
1442 * following lock operations are safe.
1443 */
1444 raw_spin_lock_irq(&pwq->pool->lock);
1445 put_pwq(pwq);
1446 raw_spin_unlock_irq(&pwq->pool->lock);
1447 }
1448 }
1449
pwq_activate_inactive_work(struct work_struct * work)1450 static void pwq_activate_inactive_work(struct work_struct *work)
1451 {
1452 struct pool_workqueue *pwq = get_work_pwq(work);
1453
1454 trace_workqueue_activate_work(work);
1455 if (list_empty(&pwq->pool->worklist))
1456 pwq->pool->watchdog_ts = jiffies;
1457 move_linked_works(work, &pwq->pool->worklist, NULL);
1458 __clear_bit(WORK_STRUCT_INACTIVE_BIT, work_data_bits(work));
1459 pwq->nr_active++;
1460 }
1461
pwq_activate_first_inactive(struct pool_workqueue * pwq)1462 static void pwq_activate_first_inactive(struct pool_workqueue *pwq)
1463 {
1464 struct work_struct *work = list_first_entry(&pwq->inactive_works,
1465 struct work_struct, entry);
1466
1467 pwq_activate_inactive_work(work);
1468 }
1469
1470 /**
1471 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1472 * @pwq: pwq of interest
1473 * @work_data: work_data of work which left the queue
1474 *
1475 * A work either has completed or is removed from pending queue,
1476 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1477 *
1478 * CONTEXT:
1479 * raw_spin_lock_irq(pool->lock).
1480 */
pwq_dec_nr_in_flight(struct pool_workqueue * pwq,unsigned long work_data)1481 static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, unsigned long work_data)
1482 {
1483 int color = get_work_color(work_data);
1484
1485 if (!(work_data & WORK_STRUCT_INACTIVE)) {
1486 pwq->nr_active--;
1487 if (!list_empty(&pwq->inactive_works)) {
1488 /* one down, submit an inactive one */
1489 if (pwq->nr_active < pwq->max_active)
1490 pwq_activate_first_inactive(pwq);
1491 }
1492 }
1493
1494 pwq->nr_in_flight[color]--;
1495
1496 /* is flush in progress and are we at the flushing tip? */
1497 if (likely(pwq->flush_color != color))
1498 goto out_put;
1499
1500 /* are there still in-flight works? */
1501 if (pwq->nr_in_flight[color])
1502 goto out_put;
1503
1504 /* this pwq is done, clear flush_color */
1505 pwq->flush_color = -1;
1506
1507 /*
1508 * If this was the last pwq, wake up the first flusher. It
1509 * will handle the rest.
1510 */
1511 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1512 complete(&pwq->wq->first_flusher->done);
1513 out_put:
1514 put_pwq(pwq);
1515 }
1516
1517 /**
1518 * try_to_grab_pending - steal work item from worklist and disable irq
1519 * @work: work item to steal
1520 * @is_dwork: @work is a delayed_work
1521 * @flags: place to store irq state
1522 *
1523 * Try to grab PENDING bit of @work. This function can handle @work in any
1524 * stable state - idle, on timer or on worklist.
1525 *
1526 * Return:
1527 *
1528 * ======== ================================================================
1529 * 1 if @work was pending and we successfully stole PENDING
1530 * 0 if @work was idle and we claimed PENDING
1531 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1532 * -ENOENT if someone else is canceling @work, this state may persist
1533 * for arbitrarily long
1534 * ======== ================================================================
1535 *
1536 * Note:
1537 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1538 * interrupted while holding PENDING and @work off queue, irq must be
1539 * disabled on entry. This, combined with delayed_work->timer being
1540 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1541 *
1542 * On successful return, >= 0, irq is disabled and the caller is
1543 * responsible for releasing it using local_irq_restore(*@flags).
1544 *
1545 * This function is safe to call from any context including IRQ handler.
1546 */
try_to_grab_pending(struct work_struct * work,bool is_dwork,unsigned long * flags)1547 static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1548 unsigned long *flags)
1549 {
1550 struct worker_pool *pool;
1551 struct pool_workqueue *pwq;
1552
1553 local_irq_save(*flags);
1554
1555 /* try to steal the timer if it exists */
1556 if (is_dwork) {
1557 struct delayed_work *dwork = to_delayed_work(work);
1558
1559 /*
1560 * dwork->timer is irqsafe. If del_timer() fails, it's
1561 * guaranteed that the timer is not queued anywhere and not
1562 * running on the local CPU.
1563 */
1564 if (likely(del_timer(&dwork->timer)))
1565 return 1;
1566 }
1567
1568 /* try to claim PENDING the normal way */
1569 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1570 return 0;
1571
1572 rcu_read_lock();
1573 /*
1574 * The queueing is in progress, or it is already queued. Try to
1575 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1576 */
1577 pool = get_work_pool(work);
1578 if (!pool)
1579 goto fail;
1580
1581 raw_spin_lock(&pool->lock);
1582 /*
1583 * work->data is guaranteed to point to pwq only while the work
1584 * item is queued on pwq->wq, and both updating work->data to point
1585 * to pwq on queueing and to pool on dequeueing are done under
1586 * pwq->pool->lock. This in turn guarantees that, if work->data
1587 * points to pwq which is associated with a locked pool, the work
1588 * item is currently queued on that pool.
1589 */
1590 pwq = get_work_pwq(work);
1591 if (pwq && pwq->pool == pool) {
1592 debug_work_deactivate(work);
1593
1594 /*
1595 * A cancelable inactive work item must be in the
1596 * pwq->inactive_works since a queued barrier can't be
1597 * canceled (see the comments in insert_wq_barrier()).
1598 *
1599 * An inactive work item cannot be grabbed directly because
1600 * it might have linked barrier work items which, if left
1601 * on the inactive_works list, will confuse pwq->nr_active
1602 * management later on and cause stall. Make sure the work
1603 * item is activated before grabbing.
1604 */
1605 if (*work_data_bits(work) & WORK_STRUCT_INACTIVE)
1606 pwq_activate_inactive_work(work);
1607
1608 list_del_init(&work->entry);
1609 pwq_dec_nr_in_flight(pwq, *work_data_bits(work));
1610
1611 /* work->data points to pwq iff queued, point to pool */
1612 set_work_pool_and_keep_pending(work, pool->id);
1613
1614 raw_spin_unlock(&pool->lock);
1615 rcu_read_unlock();
1616 return 1;
1617 }
1618 raw_spin_unlock(&pool->lock);
1619 fail:
1620 rcu_read_unlock();
1621 local_irq_restore(*flags);
1622 if (work_is_canceling(work))
1623 return -ENOENT;
1624 cpu_relax();
1625 return -EAGAIN;
1626 }
1627
1628 /**
1629 * insert_work - insert a work into a pool
1630 * @pwq: pwq @work belongs to
1631 * @work: work to insert
1632 * @head: insertion point
1633 * @extra_flags: extra WORK_STRUCT_* flags to set
1634 *
1635 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1636 * work_struct flags.
1637 *
1638 * CONTEXT:
1639 * raw_spin_lock_irq(pool->lock).
1640 */
insert_work(struct pool_workqueue * pwq,struct work_struct * work,struct list_head * head,unsigned int extra_flags)1641 static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1642 struct list_head *head, unsigned int extra_flags)
1643 {
1644 debug_work_activate(work);
1645
1646 /* record the work call stack in order to print it in KASAN reports */
1647 kasan_record_aux_stack_noalloc(work);
1648
1649 /* we own @work, set data and link */
1650 set_work_pwq(work, pwq, extra_flags);
1651 list_add_tail(&work->entry, head);
1652 get_pwq(pwq);
1653 }
1654
1655 /*
1656 * Test whether @work is being queued from another work executing on the
1657 * same workqueue.
1658 */
is_chained_work(struct workqueue_struct * wq)1659 static bool is_chained_work(struct workqueue_struct *wq)
1660 {
1661 struct worker *worker;
1662
1663 worker = current_wq_worker();
1664 /*
1665 * Return %true iff I'm a worker executing a work item on @wq. If
1666 * I'm @worker, it's safe to dereference it without locking.
1667 */
1668 return worker && worker->current_pwq->wq == wq;
1669 }
1670
1671 /*
1672 * When queueing an unbound work item to a wq, prefer local CPU if allowed
1673 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
1674 * avoid perturbing sensitive tasks.
1675 */
wq_select_unbound_cpu(int cpu)1676 static int wq_select_unbound_cpu(int cpu)
1677 {
1678 int new_cpu;
1679
1680 if (likely(!wq_debug_force_rr_cpu)) {
1681 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1682 return cpu;
1683 } else {
1684 pr_warn_once("workqueue: round-robin CPU selection forced, expect performance impact\n");
1685 }
1686
1687 new_cpu = __this_cpu_read(wq_rr_cpu_last);
1688 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1689 if (unlikely(new_cpu >= nr_cpu_ids)) {
1690 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1691 if (unlikely(new_cpu >= nr_cpu_ids))
1692 return cpu;
1693 }
1694 __this_cpu_write(wq_rr_cpu_last, new_cpu);
1695
1696 return new_cpu;
1697 }
1698
__queue_work(int cpu,struct workqueue_struct * wq,struct work_struct * work)1699 static void __queue_work(int cpu, struct workqueue_struct *wq,
1700 struct work_struct *work)
1701 {
1702 struct pool_workqueue *pwq;
1703 struct worker_pool *last_pool, *pool;
1704 unsigned int work_flags;
1705 unsigned int req_cpu = cpu;
1706
1707 /*
1708 * While a work item is PENDING && off queue, a task trying to
1709 * steal the PENDING will busy-loop waiting for it to either get
1710 * queued or lose PENDING. Grabbing PENDING and queueing should
1711 * happen with IRQ disabled.
1712 */
1713 lockdep_assert_irqs_disabled();
1714
1715
1716 /*
1717 * For a draining wq, only works from the same workqueue are
1718 * allowed. The __WQ_DESTROYING helps to spot the issue that
1719 * queues a new work item to a wq after destroy_workqueue(wq).
1720 */
1721 if (unlikely(wq->flags & (__WQ_DESTROYING | __WQ_DRAINING) &&
1722 WARN_ON_ONCE(!is_chained_work(wq))))
1723 return;
1724 rcu_read_lock();
1725 retry:
1726 /* pwq which will be used unless @work is executing elsewhere */
1727 if (req_cpu == WORK_CPU_UNBOUND) {
1728 if (wq->flags & WQ_UNBOUND)
1729 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1730 else
1731 cpu = raw_smp_processor_id();
1732 }
1733
1734 pwq = rcu_dereference(*per_cpu_ptr(wq->cpu_pwq, cpu));
1735 pool = pwq->pool;
1736
1737 /*
1738 * If @work was previously on a different pool, it might still be
1739 * running there, in which case the work needs to be queued on that
1740 * pool to guarantee non-reentrancy.
1741 */
1742 last_pool = get_work_pool(work);
1743 if (last_pool && last_pool != pool) {
1744 struct worker *worker;
1745
1746 raw_spin_lock(&last_pool->lock);
1747
1748 worker = find_worker_executing_work(last_pool, work);
1749
1750 if (worker && worker->current_pwq->wq == wq) {
1751 pwq = worker->current_pwq;
1752 pool = pwq->pool;
1753 WARN_ON_ONCE(pool != last_pool);
1754 } else {
1755 /* meh... not running there, queue here */
1756 raw_spin_unlock(&last_pool->lock);
1757 raw_spin_lock(&pool->lock);
1758 }
1759 } else {
1760 raw_spin_lock(&pool->lock);
1761 }
1762
1763 /*
1764 * pwq is determined and locked. For unbound pools, we could have raced
1765 * with pwq release and it could already be dead. If its refcnt is zero,
1766 * repeat pwq selection. Note that unbound pwqs never die without
1767 * another pwq replacing it in cpu_pwq or while work items are executing
1768 * on it, so the retrying is guaranteed to make forward-progress.
1769 */
1770 if (unlikely(!pwq->refcnt)) {
1771 if (wq->flags & WQ_UNBOUND) {
1772 raw_spin_unlock(&pool->lock);
1773 cpu_relax();
1774 goto retry;
1775 }
1776 /* oops */
1777 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1778 wq->name, cpu);
1779 }
1780
1781 /* pwq determined, queue */
1782 trace_workqueue_queue_work(req_cpu, pwq, work);
1783
1784 if (WARN_ON(!list_empty(&work->entry)))
1785 goto out;
1786
1787 pwq->nr_in_flight[pwq->work_color]++;
1788 work_flags = work_color_to_flags(pwq->work_color);
1789
1790 if (likely(pwq->nr_active < pwq->max_active)) {
1791 if (list_empty(&pool->worklist))
1792 pool->watchdog_ts = jiffies;
1793
1794 trace_workqueue_activate_work(work);
1795 pwq->nr_active++;
1796 insert_work(pwq, work, &pool->worklist, work_flags);
1797 kick_pool(pool);
1798 } else {
1799 work_flags |= WORK_STRUCT_INACTIVE;
1800 insert_work(pwq, work, &pwq->inactive_works, work_flags);
1801 }
1802
1803 out:
1804 raw_spin_unlock(&pool->lock);
1805 rcu_read_unlock();
1806 }
1807
1808 /**
1809 * queue_work_on - queue work on specific cpu
1810 * @cpu: CPU number to execute work on
1811 * @wq: workqueue to use
1812 * @work: work to queue
1813 *
1814 * We queue the work to a specific CPU, the caller must ensure it
1815 * can't go away. Callers that fail to ensure that the specified
1816 * CPU cannot go away will execute on a randomly chosen CPU.
1817 * But note well that callers specifying a CPU that never has been
1818 * online will get a splat.
1819 *
1820 * Return: %false if @work was already on a queue, %true otherwise.
1821 */
queue_work_on(int cpu,struct workqueue_struct * wq,struct work_struct * work)1822 bool queue_work_on(int cpu, struct workqueue_struct *wq,
1823 struct work_struct *work)
1824 {
1825 bool ret = false;
1826 unsigned long flags;
1827
1828 local_irq_save(flags);
1829
1830 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1831 __queue_work(cpu, wq, work);
1832 ret = true;
1833 }
1834
1835 local_irq_restore(flags);
1836 return ret;
1837 }
1838 EXPORT_SYMBOL(queue_work_on);
1839
1840 /**
1841 * select_numa_node_cpu - Select a CPU based on NUMA node
1842 * @node: NUMA node ID that we want to select a CPU from
1843 *
1844 * This function will attempt to find a "random" cpu available on a given
1845 * node. If there are no CPUs available on the given node it will return
1846 * WORK_CPU_UNBOUND indicating that we should just schedule to any
1847 * available CPU if we need to schedule this work.
1848 */
select_numa_node_cpu(int node)1849 static int select_numa_node_cpu(int node)
1850 {
1851 int cpu;
1852
1853 /* Delay binding to CPU if node is not valid or online */
1854 if (node < 0 || node >= MAX_NUMNODES || !node_online(node))
1855 return WORK_CPU_UNBOUND;
1856
1857 /* Use local node/cpu if we are already there */
1858 cpu = raw_smp_processor_id();
1859 if (node == cpu_to_node(cpu))
1860 return cpu;
1861
1862 /* Use "random" otherwise know as "first" online CPU of node */
1863 cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask);
1864
1865 /* If CPU is valid return that, otherwise just defer */
1866 return cpu < nr_cpu_ids ? cpu : WORK_CPU_UNBOUND;
1867 }
1868
1869 /**
1870 * queue_work_node - queue work on a "random" cpu for a given NUMA node
1871 * @node: NUMA node that we are targeting the work for
1872 * @wq: workqueue to use
1873 * @work: work to queue
1874 *
1875 * We queue the work to a "random" CPU within a given NUMA node. The basic
1876 * idea here is to provide a way to somehow associate work with a given
1877 * NUMA node.
1878 *
1879 * This function will only make a best effort attempt at getting this onto
1880 * the right NUMA node. If no node is requested or the requested node is
1881 * offline then we just fall back to standard queue_work behavior.
1882 *
1883 * Currently the "random" CPU ends up being the first available CPU in the
1884 * intersection of cpu_online_mask and the cpumask of the node, unless we
1885 * are running on the node. In that case we just use the current CPU.
1886 *
1887 * Return: %false if @work was already on a queue, %true otherwise.
1888 */
queue_work_node(int node,struct workqueue_struct * wq,struct work_struct * work)1889 bool queue_work_node(int node, struct workqueue_struct *wq,
1890 struct work_struct *work)
1891 {
1892 unsigned long flags;
1893 bool ret = false;
1894
1895 /*
1896 * This current implementation is specific to unbound workqueues.
1897 * Specifically we only return the first available CPU for a given
1898 * node instead of cycling through individual CPUs within the node.
1899 *
1900 * If this is used with a per-cpu workqueue then the logic in
1901 * workqueue_select_cpu_near would need to be updated to allow for
1902 * some round robin type logic.
1903 */
1904 WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND));
1905
1906 local_irq_save(flags);
1907
1908 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1909 int cpu = select_numa_node_cpu(node);
1910
1911 __queue_work(cpu, wq, work);
1912 ret = true;
1913 }
1914
1915 local_irq_restore(flags);
1916 return ret;
1917 }
1918 EXPORT_SYMBOL_GPL(queue_work_node);
1919
delayed_work_timer_fn(struct timer_list * t)1920 void delayed_work_timer_fn(struct timer_list *t)
1921 {
1922 struct delayed_work *dwork = from_timer(dwork, t, timer);
1923
1924 /* should have been called from irqsafe timer with irq already off */
1925 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1926 }
1927 EXPORT_SYMBOL(delayed_work_timer_fn);
1928
__queue_delayed_work(int cpu,struct workqueue_struct * wq,struct delayed_work * dwork,unsigned long delay)1929 static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1930 struct delayed_work *dwork, unsigned long delay)
1931 {
1932 struct timer_list *timer = &dwork->timer;
1933 struct work_struct *work = &dwork->work;
1934
1935 WARN_ON_ONCE(!wq);
1936 WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
1937 WARN_ON_ONCE(timer_pending(timer));
1938 WARN_ON_ONCE(!list_empty(&work->entry));
1939
1940 /*
1941 * If @delay is 0, queue @dwork->work immediately. This is for
1942 * both optimization and correctness. The earliest @timer can
1943 * expire is on the closest next tick and delayed_work users depend
1944 * on that there's no such delay when @delay is 0.
1945 */
1946 if (!delay) {
1947 __queue_work(cpu, wq, &dwork->work);
1948 return;
1949 }
1950
1951 dwork->wq = wq;
1952 dwork->cpu = cpu;
1953 timer->expires = jiffies + delay;
1954
1955 if (unlikely(cpu != WORK_CPU_UNBOUND))
1956 add_timer_on(timer, cpu);
1957 else
1958 add_timer(timer);
1959 }
1960
1961 /**
1962 * queue_delayed_work_on - queue work on specific CPU after delay
1963 * @cpu: CPU number to execute work on
1964 * @wq: workqueue to use
1965 * @dwork: work to queue
1966 * @delay: number of jiffies to wait before queueing
1967 *
1968 * Return: %false if @work was already on a queue, %true otherwise. If
1969 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1970 * execution.
1971 */
queue_delayed_work_on(int cpu,struct workqueue_struct * wq,struct delayed_work * dwork,unsigned long delay)1972 bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1973 struct delayed_work *dwork, unsigned long delay)
1974 {
1975 struct work_struct *work = &dwork->work;
1976 bool ret = false;
1977 unsigned long flags;
1978
1979 /* read the comment in __queue_work() */
1980 local_irq_save(flags);
1981
1982 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1983 __queue_delayed_work(cpu, wq, dwork, delay);
1984 ret = true;
1985 }
1986
1987 local_irq_restore(flags);
1988 return ret;
1989 }
1990 EXPORT_SYMBOL(queue_delayed_work_on);
1991
1992 /**
1993 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1994 * @cpu: CPU number to execute work on
1995 * @wq: workqueue to use
1996 * @dwork: work to queue
1997 * @delay: number of jiffies to wait before queueing
1998 *
1999 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
2000 * modify @dwork's timer so that it expires after @delay. If @delay is
2001 * zero, @work is guaranteed to be scheduled immediately regardless of its
2002 * current state.
2003 *
2004 * Return: %false if @dwork was idle and queued, %true if @dwork was
2005 * pending and its timer was modified.
2006 *
2007 * This function is safe to call from any context including IRQ handler.
2008 * See try_to_grab_pending() for details.
2009 */
mod_delayed_work_on(int cpu,struct workqueue_struct * wq,struct delayed_work * dwork,unsigned long delay)2010 bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
2011 struct delayed_work *dwork, unsigned long delay)
2012 {
2013 unsigned long flags;
2014 int ret;
2015
2016 do {
2017 ret = try_to_grab_pending(&dwork->work, true, &flags);
2018 } while (unlikely(ret == -EAGAIN));
2019
2020 if (likely(ret >= 0)) {
2021 __queue_delayed_work(cpu, wq, dwork, delay);
2022 local_irq_restore(flags);
2023 }
2024
2025 /* -ENOENT from try_to_grab_pending() becomes %true */
2026 return ret;
2027 }
2028 EXPORT_SYMBOL_GPL(mod_delayed_work_on);
2029
rcu_work_rcufn(struct rcu_head * rcu)2030 static void rcu_work_rcufn(struct rcu_head *rcu)
2031 {
2032 struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu);
2033
2034 /* read the comment in __queue_work() */
2035 local_irq_disable();
2036 __queue_work(WORK_CPU_UNBOUND, rwork->wq, &rwork->work);
2037 local_irq_enable();
2038 }
2039
2040 /**
2041 * queue_rcu_work - queue work after a RCU grace period
2042 * @wq: workqueue to use
2043 * @rwork: work to queue
2044 *
2045 * Return: %false if @rwork was already pending, %true otherwise. Note
2046 * that a full RCU grace period is guaranteed only after a %true return.
2047 * While @rwork is guaranteed to be executed after a %false return, the
2048 * execution may happen before a full RCU grace period has passed.
2049 */
queue_rcu_work(struct workqueue_struct * wq,struct rcu_work * rwork)2050 bool queue_rcu_work(struct workqueue_struct *wq, struct rcu_work *rwork)
2051 {
2052 struct work_struct *work = &rwork->work;
2053
2054 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
2055 rwork->wq = wq;
2056 call_rcu_hurry(&rwork->rcu, rcu_work_rcufn);
2057 return true;
2058 }
2059
2060 return false;
2061 }
2062 EXPORT_SYMBOL(queue_rcu_work);
2063
alloc_worker(int node)2064 static struct worker *alloc_worker(int node)
2065 {
2066 struct worker *worker;
2067
2068 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
2069 if (worker) {
2070 INIT_LIST_HEAD(&worker->entry);
2071 INIT_LIST_HEAD(&worker->scheduled);
2072 INIT_LIST_HEAD(&worker->node);
2073 /* on creation a worker is in !idle && prep state */
2074 worker->flags = WORKER_PREP;
2075 }
2076 return worker;
2077 }
2078
pool_allowed_cpus(struct worker_pool * pool)2079 static cpumask_t *pool_allowed_cpus(struct worker_pool *pool)
2080 {
2081 if (pool->cpu < 0 && pool->attrs->affn_strict)
2082 return pool->attrs->__pod_cpumask;
2083 else
2084 return pool->attrs->cpumask;
2085 }
2086
2087 /**
2088 * worker_attach_to_pool() - attach a worker to a pool
2089 * @worker: worker to be attached
2090 * @pool: the target pool
2091 *
2092 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
2093 * cpu-binding of @worker are kept coordinated with the pool across
2094 * cpu-[un]hotplugs.
2095 */
worker_attach_to_pool(struct worker * worker,struct worker_pool * pool)2096 static void worker_attach_to_pool(struct worker *worker,
2097 struct worker_pool *pool)
2098 {
2099 mutex_lock(&wq_pool_attach_mutex);
2100
2101 /*
2102 * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
2103 * stable across this function. See the comments above the flag
2104 * definition for details.
2105 */
2106 if (pool->flags & POOL_DISASSOCIATED)
2107 worker->flags |= WORKER_UNBOUND;
2108 else
2109 kthread_set_per_cpu(worker->task, pool->cpu);
2110
2111 if (worker->rescue_wq)
2112 set_cpus_allowed_ptr(worker->task, pool_allowed_cpus(pool));
2113
2114 list_add_tail(&worker->node, &pool->workers);
2115 worker->pool = pool;
2116
2117 mutex_unlock(&wq_pool_attach_mutex);
2118 }
2119
2120 /**
2121 * worker_detach_from_pool() - detach a worker from its pool
2122 * @worker: worker which is attached to its pool
2123 *
2124 * Undo the attaching which had been done in worker_attach_to_pool(). The
2125 * caller worker shouldn't access to the pool after detached except it has
2126 * other reference to the pool.
2127 */
worker_detach_from_pool(struct worker * worker)2128 static void worker_detach_from_pool(struct worker *worker)
2129 {
2130 struct worker_pool *pool = worker->pool;
2131 struct completion *detach_completion = NULL;
2132
2133 mutex_lock(&wq_pool_attach_mutex);
2134
2135 kthread_set_per_cpu(worker->task, -1);
2136 list_del(&worker->node);
2137 worker->pool = NULL;
2138
2139 if (list_empty(&pool->workers) && list_empty(&pool->dying_workers))
2140 detach_completion = pool->detach_completion;
2141 mutex_unlock(&wq_pool_attach_mutex);
2142
2143 /* clear leftover flags without pool->lock after it is detached */
2144 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
2145
2146 if (detach_completion)
2147 complete(detach_completion);
2148 }
2149
2150 /**
2151 * create_worker - create a new workqueue worker
2152 * @pool: pool the new worker will belong to
2153 *
2154 * Create and start a new worker which is attached to @pool.
2155 *
2156 * CONTEXT:
2157 * Might sleep. Does GFP_KERNEL allocations.
2158 *
2159 * Return:
2160 * Pointer to the newly created worker.
2161 */
create_worker(struct worker_pool * pool)2162 static struct worker *create_worker(struct worker_pool *pool)
2163 {
2164 struct worker *worker;
2165 int id;
2166 char id_buf[23];
2167
2168 /* ID is needed to determine kthread name */
2169 id = ida_alloc(&pool->worker_ida, GFP_KERNEL);
2170 if (id < 0) {
2171 pr_err_once("workqueue: Failed to allocate a worker ID: %pe\n",
2172 ERR_PTR(id));
2173 return NULL;
2174 }
2175
2176 worker = alloc_worker(pool->node);
2177 if (!worker) {
2178 pr_err_once("workqueue: Failed to allocate a worker\n");
2179 goto fail;
2180 }
2181
2182 worker->id = id;
2183
2184 if (pool->cpu >= 0)
2185 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
2186 pool->attrs->nice < 0 ? "H" : "");
2187 else
2188 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
2189
2190 worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
2191 "kworker/%s", id_buf);
2192 if (IS_ERR(worker->task)) {
2193 if (PTR_ERR(worker->task) == -EINTR) {
2194 pr_err("workqueue: Interrupted when creating a worker thread \"kworker/%s\"\n",
2195 id_buf);
2196 } else {
2197 pr_err_once("workqueue: Failed to create a worker thread: %pe",
2198 worker->task);
2199 }
2200 goto fail;
2201 }
2202
2203 set_user_nice(worker->task, pool->attrs->nice);
2204 kthread_bind_mask(worker->task, pool_allowed_cpus(pool));
2205
2206 /* successful, attach the worker to the pool */
2207 worker_attach_to_pool(worker, pool);
2208
2209 /* start the newly created worker */
2210 raw_spin_lock_irq(&pool->lock);
2211
2212 worker->pool->nr_workers++;
2213 worker_enter_idle(worker);
2214 kick_pool(pool);
2215
2216 /*
2217 * @worker is waiting on a completion in kthread() and will trigger hung
2218 * check if not woken up soon. As kick_pool() might not have waken it
2219 * up, wake it up explicitly once more.
2220 */
2221 wake_up_process(worker->task);
2222
2223 raw_spin_unlock_irq(&pool->lock);
2224
2225 return worker;
2226
2227 fail:
2228 ida_free(&pool->worker_ida, id);
2229 kfree(worker);
2230 return NULL;
2231 }
2232
unbind_worker(struct worker * worker)2233 static void unbind_worker(struct worker *worker)
2234 {
2235 lockdep_assert_held(&wq_pool_attach_mutex);
2236
2237 kthread_set_per_cpu(worker->task, -1);
2238 if (cpumask_intersects(wq_unbound_cpumask, cpu_active_mask))
2239 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, wq_unbound_cpumask) < 0);
2240 else
2241 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);
2242 }
2243
wake_dying_workers(struct list_head * cull_list)2244 static void wake_dying_workers(struct list_head *cull_list)
2245 {
2246 struct worker *worker, *tmp;
2247
2248 list_for_each_entry_safe(worker, tmp, cull_list, entry) {
2249 list_del_init(&worker->entry);
2250 unbind_worker(worker);
2251 /*
2252 * If the worker was somehow already running, then it had to be
2253 * in pool->idle_list when set_worker_dying() happened or we
2254 * wouldn't have gotten here.
2255 *
2256 * Thus, the worker must either have observed the WORKER_DIE
2257 * flag, or have set its state to TASK_IDLE. Either way, the
2258 * below will be observed by the worker and is safe to do
2259 * outside of pool->lock.
2260 */
2261 wake_up_process(worker->task);
2262 }
2263 }
2264
2265 /**
2266 * set_worker_dying - Tag a worker for destruction
2267 * @worker: worker to be destroyed
2268 * @list: transfer worker away from its pool->idle_list and into list
2269 *
2270 * Tag @worker for destruction and adjust @pool stats accordingly. The worker
2271 * should be idle.
2272 *
2273 * CONTEXT:
2274 * raw_spin_lock_irq(pool->lock).
2275 */
set_worker_dying(struct worker * worker,struct list_head * list)2276 static void set_worker_dying(struct worker *worker, struct list_head *list)
2277 {
2278 struct worker_pool *pool = worker->pool;
2279
2280 lockdep_assert_held(&pool->lock);
2281 lockdep_assert_held(&wq_pool_attach_mutex);
2282
2283 /* sanity check frenzy */
2284 if (WARN_ON(worker->current_work) ||
2285 WARN_ON(!list_empty(&worker->scheduled)) ||
2286 WARN_ON(!(worker->flags & WORKER_IDLE)))
2287 return;
2288
2289 pool->nr_workers--;
2290 pool->nr_idle--;
2291
2292 worker->flags |= WORKER_DIE;
2293
2294 list_move(&worker->entry, list);
2295 list_move(&worker->node, &pool->dying_workers);
2296 }
2297
2298 /**
2299 * idle_worker_timeout - check if some idle workers can now be deleted.
2300 * @t: The pool's idle_timer that just expired
2301 *
2302 * The timer is armed in worker_enter_idle(). Note that it isn't disarmed in
2303 * worker_leave_idle(), as a worker flicking between idle and active while its
2304 * pool is at the too_many_workers() tipping point would cause too much timer
2305 * housekeeping overhead. Since IDLE_WORKER_TIMEOUT is long enough, we just let
2306 * it expire and re-evaluate things from there.
2307 */
idle_worker_timeout(struct timer_list * t)2308 static void idle_worker_timeout(struct timer_list *t)
2309 {
2310 struct worker_pool *pool = from_timer(pool, t, idle_timer);
2311 bool do_cull = false;
2312
2313 if (work_pending(&pool->idle_cull_work))
2314 return;
2315
2316 raw_spin_lock_irq(&pool->lock);
2317
2318 if (too_many_workers(pool)) {
2319 struct worker *worker;
2320 unsigned long expires;
2321
2322 /* idle_list is kept in LIFO order, check the last one */
2323 worker = list_entry(pool->idle_list.prev, struct worker, entry);
2324 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2325 do_cull = !time_before(jiffies, expires);
2326
2327 if (!do_cull)
2328 mod_timer(&pool->idle_timer, expires);
2329 }
2330 raw_spin_unlock_irq(&pool->lock);
2331
2332 if (do_cull)
2333 queue_work(system_unbound_wq, &pool->idle_cull_work);
2334 }
2335
2336 /**
2337 * idle_cull_fn - cull workers that have been idle for too long.
2338 * @work: the pool's work for handling these idle workers
2339 *
2340 * This goes through a pool's idle workers and gets rid of those that have been
2341 * idle for at least IDLE_WORKER_TIMEOUT seconds.
2342 *
2343 * We don't want to disturb isolated CPUs because of a pcpu kworker being
2344 * culled, so this also resets worker affinity. This requires a sleepable
2345 * context, hence the split between timer callback and work item.
2346 */
idle_cull_fn(struct work_struct * work)2347 static void idle_cull_fn(struct work_struct *work)
2348 {
2349 struct worker_pool *pool = container_of(work, struct worker_pool, idle_cull_work);
2350 LIST_HEAD(cull_list);
2351
2352 /*
2353 * Grabbing wq_pool_attach_mutex here ensures an already-running worker
2354 * cannot proceed beyong worker_detach_from_pool() in its self-destruct
2355 * path. This is required as a previously-preempted worker could run after
2356 * set_worker_dying() has happened but before wake_dying_workers() did.
2357 */
2358 mutex_lock(&wq_pool_attach_mutex);
2359 raw_spin_lock_irq(&pool->lock);
2360
2361 while (too_many_workers(pool)) {
2362 struct worker *worker;
2363 unsigned long expires;
2364
2365 worker = list_entry(pool->idle_list.prev, struct worker, entry);
2366 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
2367
2368 if (time_before(jiffies, expires)) {
2369 mod_timer(&pool->idle_timer, expires);
2370 break;
2371 }
2372
2373 set_worker_dying(worker, &cull_list);
2374 }
2375
2376 raw_spin_unlock_irq(&pool->lock);
2377 wake_dying_workers(&cull_list);
2378 mutex_unlock(&wq_pool_attach_mutex);
2379 }
2380
send_mayday(struct work_struct * work)2381 static void send_mayday(struct work_struct *work)
2382 {
2383 struct pool_workqueue *pwq = get_work_pwq(work);
2384 struct workqueue_struct *wq = pwq->wq;
2385
2386 lockdep_assert_held(&wq_mayday_lock);
2387
2388 if (!wq->rescuer)
2389 return;
2390
2391 /* mayday mayday mayday */
2392 if (list_empty(&pwq->mayday_node)) {
2393 /*
2394 * If @pwq is for an unbound wq, its base ref may be put at
2395 * any time due to an attribute change. Pin @pwq until the
2396 * rescuer is done with it.
2397 */
2398 get_pwq(pwq);
2399 list_add_tail(&pwq->mayday_node, &wq->maydays);
2400 wake_up_process(wq->rescuer->task);
2401 pwq->stats[PWQ_STAT_MAYDAY]++;
2402 }
2403 }
2404
pool_mayday_timeout(struct timer_list * t)2405 static void pool_mayday_timeout(struct timer_list *t)
2406 {
2407 struct worker_pool *pool = from_timer(pool, t, mayday_timer);
2408 struct work_struct *work;
2409
2410 raw_spin_lock_irq(&pool->lock);
2411 raw_spin_lock(&wq_mayday_lock); /* for wq->maydays */
2412
2413 if (need_to_create_worker(pool)) {
2414 /*
2415 * We've been trying to create a new worker but
2416 * haven't been successful. We might be hitting an
2417 * allocation deadlock. Send distress signals to
2418 * rescuers.
2419 */
2420 list_for_each_entry(work, &pool->worklist, entry)
2421 send_mayday(work);
2422 }
2423
2424 raw_spin_unlock(&wq_mayday_lock);
2425 raw_spin_unlock_irq(&pool->lock);
2426
2427 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
2428 }
2429
2430 /**
2431 * maybe_create_worker - create a new worker if necessary
2432 * @pool: pool to create a new worker for
2433 *
2434 * Create a new worker for @pool if necessary. @pool is guaranteed to
2435 * have at least one idle worker on return from this function. If
2436 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
2437 * sent to all rescuers with works scheduled on @pool to resolve
2438 * possible allocation deadlock.
2439 *
2440 * On return, need_to_create_worker() is guaranteed to be %false and
2441 * may_start_working() %true.
2442 *
2443 * LOCKING:
2444 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2445 * multiple times. Does GFP_KERNEL allocations. Called only from
2446 * manager.
2447 */
maybe_create_worker(struct worker_pool * pool)2448 static void maybe_create_worker(struct worker_pool *pool)
2449 __releases(&pool->lock)
2450 __acquires(&pool->lock)
2451 {
2452 restart:
2453 raw_spin_unlock_irq(&pool->lock);
2454
2455 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
2456 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
2457
2458 while (true) {
2459 if (create_worker(pool) || !need_to_create_worker(pool))
2460 break;
2461
2462 schedule_timeout_interruptible(CREATE_COOLDOWN);
2463
2464 if (!need_to_create_worker(pool))
2465 break;
2466 }
2467
2468 del_timer_sync(&pool->mayday_timer);
2469 raw_spin_lock_irq(&pool->lock);
2470 /*
2471 * This is necessary even after a new worker was just successfully
2472 * created as @pool->lock was dropped and the new worker might have
2473 * already become busy.
2474 */
2475 if (need_to_create_worker(pool))
2476 goto restart;
2477 }
2478
2479 /**
2480 * manage_workers - manage worker pool
2481 * @worker: self
2482 *
2483 * Assume the manager role and manage the worker pool @worker belongs
2484 * to. At any given time, there can be only zero or one manager per
2485 * pool. The exclusion is handled automatically by this function.
2486 *
2487 * The caller can safely start processing works on false return. On
2488 * true return, it's guaranteed that need_to_create_worker() is false
2489 * and may_start_working() is true.
2490 *
2491 * CONTEXT:
2492 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2493 * multiple times. Does GFP_KERNEL allocations.
2494 *
2495 * Return:
2496 * %false if the pool doesn't need management and the caller can safely
2497 * start processing works, %true if management function was performed and
2498 * the conditions that the caller verified before calling the function may
2499 * no longer be true.
2500 */
manage_workers(struct worker * worker)2501 static bool manage_workers(struct worker *worker)
2502 {
2503 struct worker_pool *pool = worker->pool;
2504
2505 if (pool->flags & POOL_MANAGER_ACTIVE)
2506 return false;
2507
2508 pool->flags |= POOL_MANAGER_ACTIVE;
2509 pool->manager = worker;
2510
2511 maybe_create_worker(pool);
2512
2513 pool->manager = NULL;
2514 pool->flags &= ~POOL_MANAGER_ACTIVE;
2515 rcuwait_wake_up(&manager_wait);
2516 return true;
2517 }
2518
2519 /**
2520 * process_one_work - process single work
2521 * @worker: self
2522 * @work: work to process
2523 *
2524 * Process @work. This function contains all the logics necessary to
2525 * process a single work including synchronization against and
2526 * interaction with other workers on the same cpu, queueing and
2527 * flushing. As long as context requirement is met, any worker can
2528 * call this function to process a work.
2529 *
2530 * CONTEXT:
2531 * raw_spin_lock_irq(pool->lock) which is released and regrabbed.
2532 */
process_one_work(struct worker * worker,struct work_struct * work)2533 static void process_one_work(struct worker *worker, struct work_struct *work)
2534 __releases(&pool->lock)
2535 __acquires(&pool->lock)
2536 {
2537 struct pool_workqueue *pwq = get_work_pwq(work);
2538 struct worker_pool *pool = worker->pool;
2539 unsigned long work_data;
2540 #ifdef CONFIG_LOCKDEP
2541 /*
2542 * It is permissible to free the struct work_struct from
2543 * inside the function that is called from it, this we need to
2544 * take into account for lockdep too. To avoid bogus "held
2545 * lock freed" warnings as well as problems when looking into
2546 * work->lockdep_map, make a copy and use that here.
2547 */
2548 struct lockdep_map lockdep_map;
2549
2550 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2551 #endif
2552 /* ensure we're on the correct CPU */
2553 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2554 raw_smp_processor_id() != pool->cpu);
2555
2556 /* claim and dequeue */
2557 debug_work_deactivate(work);
2558 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2559 worker->current_work = work;
2560 worker->current_func = work->func;
2561 worker->current_pwq = pwq;
2562 worker->current_at = worker->task->se.sum_exec_runtime;
2563 work_data = *work_data_bits(work);
2564 worker->current_color = get_work_color(work_data);
2565
2566 /*
2567 * Record wq name for cmdline and debug reporting, may get
2568 * overridden through set_worker_desc().
2569 */
2570 strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
2571
2572 list_del_init(&work->entry);
2573
2574 /*
2575 * CPU intensive works don't participate in concurrency management.
2576 * They're the scheduler's responsibility. This takes @worker out
2577 * of concurrency management and the next code block will chain
2578 * execution of the pending work items.
2579 */
2580 if (unlikely(pwq->wq->flags & WQ_CPU_INTENSIVE))
2581 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2582
2583 /*
2584 * Kick @pool if necessary. It's always noop for per-cpu worker pools
2585 * since nr_running would always be >= 1 at this point. This is used to
2586 * chain execution of the pending work items for WORKER_NOT_RUNNING
2587 * workers such as the UNBOUND and CPU_INTENSIVE ones.
2588 */
2589 kick_pool(pool);
2590
2591 /*
2592 * Record the last pool and clear PENDING which should be the last
2593 * update to @work. Also, do this inside @pool->lock so that
2594 * PENDING and queued state changes happen together while IRQ is
2595 * disabled.
2596 */
2597 set_work_pool_and_clear_pending(work, pool->id);
2598
2599 pwq->stats[PWQ_STAT_STARTED]++;
2600 raw_spin_unlock_irq(&pool->lock);
2601
2602 lock_map_acquire(&pwq->wq->lockdep_map);
2603 lock_map_acquire(&lockdep_map);
2604 /*
2605 * Strictly speaking we should mark the invariant state without holding
2606 * any locks, that is, before these two lock_map_acquire()'s.
2607 *
2608 * However, that would result in:
2609 *
2610 * A(W1)
2611 * WFC(C)
2612 * A(W1)
2613 * C(C)
2614 *
2615 * Which would create W1->C->W1 dependencies, even though there is no
2616 * actual deadlock possible. There are two solutions, using a
2617 * read-recursive acquire on the work(queue) 'locks', but this will then
2618 * hit the lockdep limitation on recursive locks, or simply discard
2619 * these locks.
2620 *
2621 * AFAICT there is no possible deadlock scenario between the
2622 * flush_work() and complete() primitives (except for single-threaded
2623 * workqueues), so hiding them isn't a problem.
2624 */
2625 lockdep_invariant_state(true);
2626 trace_workqueue_execute_start(work);
2627 worker->current_func(work);
2628 /*
2629 * While we must be careful to not use "work" after this, the trace
2630 * point will only record its address.
2631 */
2632 trace_workqueue_execute_end(work, worker->current_func);
2633 pwq->stats[PWQ_STAT_COMPLETED]++;
2634 lock_map_release(&lockdep_map);
2635 lock_map_release(&pwq->wq->lockdep_map);
2636
2637 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2638 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2639 " last function: %ps\n",
2640 current->comm, preempt_count(), task_pid_nr(current),
2641 worker->current_func);
2642 debug_show_held_locks(current);
2643 dump_stack();
2644 }
2645
2646 /*
2647 * The following prevents a kworker from hogging CPU on !PREEMPTION
2648 * kernels, where a requeueing work item waiting for something to
2649 * happen could deadlock with stop_machine as such work item could
2650 * indefinitely requeue itself while all other CPUs are trapped in
2651 * stop_machine. At the same time, report a quiescent RCU state so
2652 * the same condition doesn't freeze RCU.
2653 */
2654 cond_resched();
2655
2656 raw_spin_lock_irq(&pool->lock);
2657
2658 /*
2659 * In addition to %WQ_CPU_INTENSIVE, @worker may also have been marked
2660 * CPU intensive by wq_worker_tick() if @work hogged CPU longer than
2661 * wq_cpu_intensive_thresh_us. Clear it.
2662 */
2663 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2664
2665 /* tag the worker for identification in schedule() */
2666 worker->last_func = worker->current_func;
2667
2668 /* we're done with it, release */
2669 hash_del(&worker->hentry);
2670 worker->current_work = NULL;
2671 worker->current_func = NULL;
2672 worker->current_pwq = NULL;
2673 worker->current_color = INT_MAX;
2674 pwq_dec_nr_in_flight(pwq, work_data);
2675 }
2676
2677 /**
2678 * process_scheduled_works - process scheduled works
2679 * @worker: self
2680 *
2681 * Process all scheduled works. Please note that the scheduled list
2682 * may change while processing a work, so this function repeatedly
2683 * fetches a work from the top and executes it.
2684 *
2685 * CONTEXT:
2686 * raw_spin_lock_irq(pool->lock) which may be released and regrabbed
2687 * multiple times.
2688 */
process_scheduled_works(struct worker * worker)2689 static void process_scheduled_works(struct worker *worker)
2690 {
2691 struct work_struct *work;
2692 bool first = true;
2693
2694 while ((work = list_first_entry_or_null(&worker->scheduled,
2695 struct work_struct, entry))) {
2696 if (first) {
2697 worker->pool->watchdog_ts = jiffies;
2698 first = false;
2699 }
2700 process_one_work(worker, work);
2701 }
2702 }
2703
set_pf_worker(bool val)2704 static void set_pf_worker(bool val)
2705 {
2706 mutex_lock(&wq_pool_attach_mutex);
2707 if (val)
2708 current->flags |= PF_WQ_WORKER;
2709 else
2710 current->flags &= ~PF_WQ_WORKER;
2711 mutex_unlock(&wq_pool_attach_mutex);
2712 }
2713
2714 /**
2715 * worker_thread - the worker thread function
2716 * @__worker: self
2717 *
2718 * The worker thread function. All workers belong to a worker_pool -
2719 * either a per-cpu one or dynamic unbound one. These workers process all
2720 * work items regardless of their specific target workqueue. The only
2721 * exception is work items which belong to workqueues with a rescuer which
2722 * will be explained in rescuer_thread().
2723 *
2724 * Return: 0
2725 */
worker_thread(void * __worker)2726 static int worker_thread(void *__worker)
2727 {
2728 struct worker *worker = __worker;
2729 struct worker_pool *pool = worker->pool;
2730
2731 /* tell the scheduler that this is a workqueue worker */
2732 set_pf_worker(true);
2733 woke_up:
2734 raw_spin_lock_irq(&pool->lock);
2735
2736 /* am I supposed to die? */
2737 if (unlikely(worker->flags & WORKER_DIE)) {
2738 raw_spin_unlock_irq(&pool->lock);
2739 set_pf_worker(false);
2740
2741 set_task_comm(worker->task, "kworker/dying");
2742 ida_free(&pool->worker_ida, worker->id);
2743 worker_detach_from_pool(worker);
2744 WARN_ON_ONCE(!list_empty(&worker->entry));
2745 kfree(worker);
2746 return 0;
2747 }
2748
2749 worker_leave_idle(worker);
2750 recheck:
2751 /* no more worker necessary? */
2752 if (!need_more_worker(pool))
2753 goto sleep;
2754
2755 /* do we need to manage? */
2756 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2757 goto recheck;
2758
2759 /*
2760 * ->scheduled list can only be filled while a worker is
2761 * preparing to process a work or actually processing it.
2762 * Make sure nobody diddled with it while I was sleeping.
2763 */
2764 WARN_ON_ONCE(!list_empty(&worker->scheduled));
2765
2766 /*
2767 * Finish PREP stage. We're guaranteed to have at least one idle
2768 * worker or that someone else has already assumed the manager
2769 * role. This is where @worker starts participating in concurrency
2770 * management if applicable and concurrency management is restored
2771 * after being rebound. See rebind_workers() for details.
2772 */
2773 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2774
2775 do {
2776 struct work_struct *work =
2777 list_first_entry(&pool->worklist,
2778 struct work_struct, entry);
2779
2780 if (assign_work(work, worker, NULL))
2781 process_scheduled_works(worker);
2782 } while (keep_working(pool));
2783
2784 worker_set_flags(worker, WORKER_PREP);
2785 sleep:
2786 /*
2787 * pool->lock is held and there's no work to process and no need to
2788 * manage, sleep. Workers are woken up only while holding
2789 * pool->lock or from local cpu, so setting the current state
2790 * before releasing pool->lock is enough to prevent losing any
2791 * event.
2792 */
2793 worker_enter_idle(worker);
2794 __set_current_state(TASK_IDLE);
2795 raw_spin_unlock_irq(&pool->lock);
2796 schedule();
2797 goto woke_up;
2798 }
2799
2800 /**
2801 * rescuer_thread - the rescuer thread function
2802 * @__rescuer: self
2803 *
2804 * Workqueue rescuer thread function. There's one rescuer for each
2805 * workqueue which has WQ_MEM_RECLAIM set.
2806 *
2807 * Regular work processing on a pool may block trying to create a new
2808 * worker which uses GFP_KERNEL allocation which has slight chance of
2809 * developing into deadlock if some works currently on the same queue
2810 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2811 * the problem rescuer solves.
2812 *
2813 * When such condition is possible, the pool summons rescuers of all
2814 * workqueues which have works queued on the pool and let them process
2815 * those works so that forward progress can be guaranteed.
2816 *
2817 * This should happen rarely.
2818 *
2819 * Return: 0
2820 */
rescuer_thread(void * __rescuer)2821 static int rescuer_thread(void *__rescuer)
2822 {
2823 struct worker *rescuer = __rescuer;
2824 struct workqueue_struct *wq = rescuer->rescue_wq;
2825 bool should_stop;
2826
2827 set_user_nice(current, RESCUER_NICE_LEVEL);
2828
2829 /*
2830 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2831 * doesn't participate in concurrency management.
2832 */
2833 set_pf_worker(true);
2834 repeat:
2835 set_current_state(TASK_IDLE);
2836
2837 /*
2838 * By the time the rescuer is requested to stop, the workqueue
2839 * shouldn't have any work pending, but @wq->maydays may still have
2840 * pwq(s) queued. This can happen by non-rescuer workers consuming
2841 * all the work items before the rescuer got to them. Go through
2842 * @wq->maydays processing before acting on should_stop so that the
2843 * list is always empty on exit.
2844 */
2845 should_stop = kthread_should_stop();
2846
2847 /* see whether any pwq is asking for help */
2848 raw_spin_lock_irq(&wq_mayday_lock);
2849
2850 while (!list_empty(&wq->maydays)) {
2851 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2852 struct pool_workqueue, mayday_node);
2853 struct worker_pool *pool = pwq->pool;
2854 struct work_struct *work, *n;
2855
2856 __set_current_state(TASK_RUNNING);
2857 list_del_init(&pwq->mayday_node);
2858
2859 raw_spin_unlock_irq(&wq_mayday_lock);
2860
2861 worker_attach_to_pool(rescuer, pool);
2862
2863 raw_spin_lock_irq(&pool->lock);
2864
2865 /*
2866 * Slurp in all works issued via this workqueue and
2867 * process'em.
2868 */
2869 WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
2870 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2871 if (get_work_pwq(work) == pwq &&
2872 assign_work(work, rescuer, &n))
2873 pwq->stats[PWQ_STAT_RESCUED]++;
2874 }
2875
2876 if (!list_empty(&rescuer->scheduled)) {
2877 process_scheduled_works(rescuer);
2878
2879 /*
2880 * The above execution of rescued work items could
2881 * have created more to rescue through
2882 * pwq_activate_first_inactive() or chained
2883 * queueing. Let's put @pwq back on mayday list so
2884 * that such back-to-back work items, which may be
2885 * being used to relieve memory pressure, don't
2886 * incur MAYDAY_INTERVAL delay inbetween.
2887 */
2888 if (pwq->nr_active && need_to_create_worker(pool)) {
2889 raw_spin_lock(&wq_mayday_lock);
2890 /*
2891 * Queue iff we aren't racing destruction
2892 * and somebody else hasn't queued it already.
2893 */
2894 if (wq->rescuer && list_empty(&pwq->mayday_node)) {
2895 get_pwq(pwq);
2896 list_add_tail(&pwq->mayday_node, &wq->maydays);
2897 }
2898 raw_spin_unlock(&wq_mayday_lock);
2899 }
2900 }
2901
2902 /*
2903 * Put the reference grabbed by send_mayday(). @pool won't
2904 * go away while we're still attached to it.
2905 */
2906 put_pwq(pwq);
2907
2908 /*
2909 * Leave this pool. Notify regular workers; otherwise, we end up
2910 * with 0 concurrency and stalling the execution.
2911 */
2912 kick_pool(pool);
2913
2914 raw_spin_unlock_irq(&pool->lock);
2915
2916 worker_detach_from_pool(rescuer);
2917
2918 raw_spin_lock_irq(&wq_mayday_lock);
2919 }
2920
2921 raw_spin_unlock_irq(&wq_mayday_lock);
2922
2923 if (should_stop) {
2924 __set_current_state(TASK_RUNNING);
2925 set_pf_worker(false);
2926 return 0;
2927 }
2928
2929 /* rescuers should never participate in concurrency management */
2930 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2931 schedule();
2932 goto repeat;
2933 }
2934
2935 /**
2936 * check_flush_dependency - check for flush dependency sanity
2937 * @target_wq: workqueue being flushed
2938 * @target_work: work item being flushed (NULL for workqueue flushes)
2939 *
2940 * %current is trying to flush the whole @target_wq or @target_work on it.
2941 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2942 * reclaiming memory or running on a workqueue which doesn't have
2943 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2944 * a deadlock.
2945 */
check_flush_dependency(struct workqueue_struct * target_wq,struct work_struct * target_work)2946 static void check_flush_dependency(struct workqueue_struct *target_wq,
2947 struct work_struct *target_work)
2948 {
2949 work_func_t target_func = target_work ? target_work->func : NULL;
2950 struct worker *worker;
2951
2952 if (target_wq->flags & WQ_MEM_RECLAIM)
2953 return;
2954
2955 worker = current_wq_worker();
2956
2957 WARN_ONCE(current->flags & PF_MEMALLOC,
2958 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%ps",
2959 current->pid, current->comm, target_wq->name, target_func);
2960 WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2961 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2962 "workqueue: WQ_MEM_RECLAIM %s:%ps is flushing !WQ_MEM_RECLAIM %s:%ps",
2963 worker->current_pwq->wq->name, worker->current_func,
2964 target_wq->name, target_func);
2965 }
2966
2967 struct wq_barrier {
2968 struct work_struct work;
2969 struct completion done;
2970 struct task_struct *task; /* purely informational */
2971 };
2972
wq_barrier_func(struct work_struct * work)2973 static void wq_barrier_func(struct work_struct *work)
2974 {
2975 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2976 complete(&barr->done);
2977 }
2978
2979 /**
2980 * insert_wq_barrier - insert a barrier work
2981 * @pwq: pwq to insert barrier into
2982 * @barr: wq_barrier to insert
2983 * @target: target work to attach @barr to
2984 * @worker: worker currently executing @target, NULL if @target is not executing
2985 *
2986 * @barr is linked to @target such that @barr is completed only after
2987 * @target finishes execution. Please note that the ordering
2988 * guarantee is observed only with respect to @target and on the local
2989 * cpu.
2990 *
2991 * Currently, a queued barrier can't be canceled. This is because
2992 * try_to_grab_pending() can't determine whether the work to be
2993 * grabbed is at the head of the queue and thus can't clear LINKED
2994 * flag of the previous work while there must be a valid next work
2995 * after a work with LINKED flag set.
2996 *
2997 * Note that when @worker is non-NULL, @target may be modified
2998 * underneath us, so we can't reliably determine pwq from @target.
2999 *
3000 * CONTEXT:
3001 * raw_spin_lock_irq(pool->lock).
3002 */
insert_wq_barrier(struct pool_workqueue * pwq,struct wq_barrier * barr,struct work_struct * target,struct worker * worker)3003 static void insert_wq_barrier(struct pool_workqueue *pwq,
3004 struct wq_barrier *barr,
3005 struct work_struct *target, struct worker *worker)
3006 {
3007 unsigned int work_flags = 0;
3008 unsigned int work_color;
3009 struct list_head *head;
3010
3011 /*
3012 * debugobject calls are safe here even with pool->lock locked
3013 * as we know for sure that this will not trigger any of the
3014 * checks and call back into the fixup functions where we
3015 * might deadlock.
3016 */
3017 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
3018 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
3019
3020 init_completion_map(&barr->done, &target->lockdep_map);
3021
3022 barr->task = current;
3023
3024 /* The barrier work item does not participate in pwq->nr_active. */
3025 work_flags |= WORK_STRUCT_INACTIVE;
3026
3027 /*
3028 * If @target is currently being executed, schedule the
3029 * barrier to the worker; otherwise, put it after @target.
3030 */
3031 if (worker) {
3032 head = worker->scheduled.next;
3033 work_color = worker->current_color;
3034 } else {
3035 unsigned long *bits = work_data_bits(target);
3036
3037 head = target->entry.next;
3038 /* there can already be other linked works, inherit and set */
3039 work_flags |= *bits & WORK_STRUCT_LINKED;
3040 work_color = get_work_color(*bits);
3041 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
3042 }
3043
3044 pwq->nr_in_flight[work_color]++;
3045 work_flags |= work_color_to_flags(work_color);
3046
3047 insert_work(pwq, &barr->work, head, work_flags);
3048 }
3049
3050 /**
3051 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
3052 * @wq: workqueue being flushed
3053 * @flush_color: new flush color, < 0 for no-op
3054 * @work_color: new work color, < 0 for no-op
3055 *
3056 * Prepare pwqs for workqueue flushing.
3057 *
3058 * If @flush_color is non-negative, flush_color on all pwqs should be
3059 * -1. If no pwq has in-flight commands at the specified color, all
3060 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
3061 * has in flight commands, its pwq->flush_color is set to
3062 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
3063 * wakeup logic is armed and %true is returned.
3064 *
3065 * The caller should have initialized @wq->first_flusher prior to
3066 * calling this function with non-negative @flush_color. If
3067 * @flush_color is negative, no flush color update is done and %false
3068 * is returned.
3069 *
3070 * If @work_color is non-negative, all pwqs should have the same
3071 * work_color which is previous to @work_color and all will be
3072 * advanced to @work_color.
3073 *
3074 * CONTEXT:
3075 * mutex_lock(wq->mutex).
3076 *
3077 * Return:
3078 * %true if @flush_color >= 0 and there's something to flush. %false
3079 * otherwise.
3080 */
flush_workqueue_prep_pwqs(struct workqueue_struct * wq,int flush_color,int work_color)3081 static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
3082 int flush_color, int work_color)
3083 {
3084 bool wait = false;
3085 struct pool_workqueue *pwq;
3086
3087 if (flush_color >= 0) {
3088 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
3089 atomic_set(&wq->nr_pwqs_to_flush, 1);
3090 }
3091
3092 for_each_pwq(pwq, wq) {
3093 struct worker_pool *pool = pwq->pool;
3094
3095 raw_spin_lock_irq(&pool->lock);
3096
3097 if (flush_color >= 0) {
3098 WARN_ON_ONCE(pwq->flush_color != -1);
3099
3100 if (pwq->nr_in_flight[flush_color]) {
3101 pwq->flush_color = flush_color;
3102 atomic_inc(&wq->nr_pwqs_to_flush);
3103 wait = true;
3104 }
3105 }
3106
3107 if (work_color >= 0) {
3108 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
3109 pwq->work_color = work_color;
3110 }
3111
3112 raw_spin_unlock_irq(&pool->lock);
3113 }
3114
3115 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
3116 complete(&wq->first_flusher->done);
3117
3118 return wait;
3119 }
3120
3121 /**
3122 * __flush_workqueue - ensure that any scheduled work has run to completion.
3123 * @wq: workqueue to flush
3124 *
3125 * This function sleeps until all work items which were queued on entry
3126 * have finished execution, but it is not livelocked by new incoming ones.
3127 */
__flush_workqueue(struct workqueue_struct * wq)3128 void __flush_workqueue(struct workqueue_struct *wq)
3129 {
3130 struct wq_flusher this_flusher = {
3131 .list = LIST_HEAD_INIT(this_flusher.list),
3132 .flush_color = -1,
3133 .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
3134 };
3135 int next_color;
3136
3137 if (WARN_ON(!wq_online))
3138 return;
3139
3140 lock_map_acquire(&wq->lockdep_map);
3141 lock_map_release(&wq->lockdep_map);
3142
3143 mutex_lock(&wq->mutex);
3144
3145 /*
3146 * Start-to-wait phase
3147 */
3148 next_color = work_next_color(wq->work_color);
3149
3150 if (next_color != wq->flush_color) {
3151 /*
3152 * Color space is not full. The current work_color
3153 * becomes our flush_color and work_color is advanced
3154 * by one.
3155 */
3156 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
3157 this_flusher.flush_color = wq->work_color;
3158 wq->work_color = next_color;
3159
3160 if (!wq->first_flusher) {
3161 /* no flush in progress, become the first flusher */
3162 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
3163
3164 wq->first_flusher = &this_flusher;
3165
3166 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
3167 wq->work_color)) {
3168 /* nothing to flush, done */
3169 wq->flush_color = next_color;
3170 wq->first_flusher = NULL;
3171 goto out_unlock;
3172 }
3173 } else {
3174 /* wait in queue */
3175 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
3176 list_add_tail(&this_flusher.list, &wq->flusher_queue);
3177 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
3178 }
3179 } else {
3180 /*
3181 * Oops, color space is full, wait on overflow queue.
3182 * The next flush completion will assign us
3183 * flush_color and transfer to flusher_queue.
3184 */
3185 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
3186 }
3187
3188 check_flush_dependency(wq, NULL);
3189
3190 mutex_unlock(&wq->mutex);
3191
3192 wait_for_completion(&this_flusher.done);
3193
3194 /*
3195 * Wake-up-and-cascade phase
3196 *
3197 * First flushers are responsible for cascading flushes and
3198 * handling overflow. Non-first flushers can simply return.
3199 */
3200 if (READ_ONCE(wq->first_flusher) != &this_flusher)
3201 return;
3202
3203 mutex_lock(&wq->mutex);
3204
3205 /* we might have raced, check again with mutex held */
3206 if (wq->first_flusher != &this_flusher)
3207 goto out_unlock;
3208
3209 WRITE_ONCE(wq->first_flusher, NULL);
3210
3211 WARN_ON_ONCE(!list_empty(&this_flusher.list));
3212 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
3213
3214 while (true) {
3215 struct wq_flusher *next, *tmp;
3216
3217 /* complete all the flushers sharing the current flush color */
3218 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
3219 if (next->flush_color != wq->flush_color)
3220 break;
3221 list_del_init(&next->list);
3222 complete(&next->done);
3223 }
3224
3225 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
3226 wq->flush_color != work_next_color(wq->work_color));
3227
3228 /* this flush_color is finished, advance by one */
3229 wq->flush_color = work_next_color(wq->flush_color);
3230
3231 /* one color has been freed, handle overflow queue */
3232 if (!list_empty(&wq->flusher_overflow)) {
3233 /*
3234 * Assign the same color to all overflowed
3235 * flushers, advance work_color and append to
3236 * flusher_queue. This is the start-to-wait
3237 * phase for these overflowed flushers.
3238 */
3239 list_for_each_entry(tmp, &wq->flusher_overflow, list)
3240 tmp->flush_color = wq->work_color;
3241
3242 wq->work_color = work_next_color(wq->work_color);
3243
3244 list_splice_tail_init(&wq->flusher_overflow,
3245 &wq->flusher_queue);
3246 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
3247 }
3248
3249 if (list_empty(&wq->flusher_queue)) {
3250 WARN_ON_ONCE(wq->flush_color != wq->work_color);
3251 break;
3252 }
3253
3254 /*
3255 * Need to flush more colors. Make the next flusher
3256 * the new first flusher and arm pwqs.
3257 */
3258 WARN_ON_ONCE(wq->flush_color == wq->work_color);
3259 WARN_ON_ONCE(wq->flush_color != next->flush_color);
3260
3261 list_del_init(&next->list);
3262 wq->first_flusher = next;
3263
3264 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
3265 break;
3266
3267 /*
3268 * Meh... this color is already done, clear first
3269 * flusher and repeat cascading.
3270 */
3271 wq->first_flusher = NULL;
3272 }
3273
3274 out_unlock:
3275 mutex_unlock(&wq->mutex);
3276 }
3277 EXPORT_SYMBOL(__flush_workqueue);
3278
3279 /**
3280 * drain_workqueue - drain a workqueue
3281 * @wq: workqueue to drain
3282 *
3283 * Wait until the workqueue becomes empty. While draining is in progress,
3284 * only chain queueing is allowed. IOW, only currently pending or running
3285 * work items on @wq can queue further work items on it. @wq is flushed
3286 * repeatedly until it becomes empty. The number of flushing is determined
3287 * by the depth of chaining and should be relatively short. Whine if it
3288 * takes too long.
3289 */
drain_workqueue(struct workqueue_struct * wq)3290 void drain_workqueue(struct workqueue_struct *wq)
3291 {
3292 unsigned int flush_cnt = 0;
3293 struct pool_workqueue *pwq;
3294
3295 /*
3296 * __queue_work() needs to test whether there are drainers, is much
3297 * hotter than drain_workqueue() and already looks at @wq->flags.
3298 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
3299 */
3300 mutex_lock(&wq->mutex);
3301 if (!wq->nr_drainers++)
3302 wq->flags |= __WQ_DRAINING;
3303 mutex_unlock(&wq->mutex);
3304 reflush:
3305 __flush_workqueue(wq);
3306
3307 mutex_lock(&wq->mutex);
3308
3309 for_each_pwq(pwq, wq) {
3310 bool drained;
3311
3312 raw_spin_lock_irq(&pwq->pool->lock);
3313 drained = !pwq->nr_active && list_empty(&pwq->inactive_works);
3314 raw_spin_unlock_irq(&pwq->pool->lock);
3315
3316 if (drained)
3317 continue;
3318
3319 if (++flush_cnt == 10 ||
3320 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
3321 pr_warn("workqueue %s: %s() isn't complete after %u tries\n",
3322 wq->name, __func__, flush_cnt);
3323
3324 mutex_unlock(&wq->mutex);
3325 goto reflush;
3326 }
3327
3328 if (!--wq->nr_drainers)
3329 wq->flags &= ~__WQ_DRAINING;
3330 mutex_unlock(&wq->mutex);
3331 }
3332 EXPORT_SYMBOL_GPL(drain_workqueue);
3333
start_flush_work(struct work_struct * work,struct wq_barrier * barr,bool from_cancel)3334 static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
3335 bool from_cancel)
3336 {
3337 struct worker *worker = NULL;
3338 struct worker_pool *pool;
3339 struct pool_workqueue *pwq;
3340
3341 might_sleep();
3342
3343 rcu_read_lock();
3344 pool = get_work_pool(work);
3345 if (!pool) {
3346 rcu_read_unlock();
3347 return false;
3348 }
3349
3350 raw_spin_lock_irq(&pool->lock);
3351 /* see the comment in try_to_grab_pending() with the same code */
3352 pwq = get_work_pwq(work);
3353 if (pwq) {
3354 if (unlikely(pwq->pool != pool))
3355 goto already_gone;
3356 } else {
3357 worker = find_worker_executing_work(pool, work);
3358 if (!worker)
3359 goto already_gone;
3360 pwq = worker->current_pwq;
3361 }
3362
3363 check_flush_dependency(pwq->wq, work);
3364
3365 insert_wq_barrier(pwq, barr, work, worker);
3366 raw_spin_unlock_irq(&pool->lock);
3367
3368 /*
3369 * Force a lock recursion deadlock when using flush_work() inside a
3370 * single-threaded or rescuer equipped workqueue.
3371 *
3372 * For single threaded workqueues the deadlock happens when the work
3373 * is after the work issuing the flush_work(). For rescuer equipped
3374 * workqueues the deadlock happens when the rescuer stalls, blocking
3375 * forward progress.
3376 */
3377 if (!from_cancel &&
3378 (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer)) {
3379 lock_map_acquire(&pwq->wq->lockdep_map);
3380 lock_map_release(&pwq->wq->lockdep_map);
3381 }
3382 rcu_read_unlock();
3383 return true;
3384 already_gone:
3385 raw_spin_unlock_irq(&pool->lock);
3386 rcu_read_unlock();
3387 return false;
3388 }
3389
__flush_work(struct work_struct * work,bool from_cancel)3390 static bool __flush_work(struct work_struct *work, bool from_cancel)
3391 {
3392 struct wq_barrier barr;
3393
3394 if (WARN_ON(!wq_online))
3395 return false;
3396
3397 if (WARN_ON(!work->func))
3398 return false;
3399
3400 lock_map_acquire(&work->lockdep_map);
3401 lock_map_release(&work->lockdep_map);
3402
3403 if (start_flush_work(work, &barr, from_cancel)) {
3404 wait_for_completion(&barr.done);
3405 destroy_work_on_stack(&barr.work);
3406 return true;
3407 } else {
3408 return false;
3409 }
3410 }
3411
3412 /**
3413 * flush_work - wait for a work to finish executing the last queueing instance
3414 * @work: the work to flush
3415 *
3416 * Wait until @work has finished execution. @work is guaranteed to be idle
3417 * on return if it hasn't been requeued since flush started.
3418 *
3419 * Return:
3420 * %true if flush_work() waited for the work to finish execution,
3421 * %false if it was already idle.
3422 */
flush_work(struct work_struct * work)3423 bool flush_work(struct work_struct *work)
3424 {
3425 return __flush_work(work, false);
3426 }
3427 EXPORT_SYMBOL_GPL(flush_work);
3428
3429 struct cwt_wait {
3430 wait_queue_entry_t wait;
3431 struct work_struct *work;
3432 };
3433
cwt_wakefn(wait_queue_entry_t * wait,unsigned mode,int sync,void * key)3434 static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
3435 {
3436 struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
3437
3438 if (cwait->work != key)
3439 return 0;
3440 return autoremove_wake_function(wait, mode, sync, key);
3441 }
3442
__cancel_work_timer(struct work_struct * work,bool is_dwork)3443 static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
3444 {
3445 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
3446 unsigned long flags;
3447 int ret;
3448
3449 do {
3450 ret = try_to_grab_pending(work, is_dwork, &flags);
3451 /*
3452 * If someone else is already canceling, wait for it to
3453 * finish. flush_work() doesn't work for PREEMPT_NONE
3454 * because we may get scheduled between @work's completion
3455 * and the other canceling task resuming and clearing
3456 * CANCELING - flush_work() will return false immediately
3457 * as @work is no longer busy, try_to_grab_pending() will
3458 * return -ENOENT as @work is still being canceled and the
3459 * other canceling task won't be able to clear CANCELING as
3460 * we're hogging the CPU.
3461 *
3462 * Let's wait for completion using a waitqueue. As this
3463 * may lead to the thundering herd problem, use a custom
3464 * wake function which matches @work along with exclusive
3465 * wait and wakeup.
3466 */
3467 if (unlikely(ret == -ENOENT)) {
3468 struct cwt_wait cwait;
3469
3470 init_wait(&cwait.wait);
3471 cwait.wait.func = cwt_wakefn;
3472 cwait.work = work;
3473
3474 prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
3475 TASK_UNINTERRUPTIBLE);
3476 if (work_is_canceling(work))
3477 schedule();
3478 finish_wait(&cancel_waitq, &cwait.wait);
3479 }
3480 } while (unlikely(ret < 0));
3481
3482 /* tell other tasks trying to grab @work to back off */
3483 mark_work_canceling(work);
3484 local_irq_restore(flags);
3485
3486 /*
3487 * This allows canceling during early boot. We know that @work
3488 * isn't executing.
3489 */
3490 if (wq_online)
3491 __flush_work(work, true);
3492
3493 clear_work_data(work);
3494
3495 /*
3496 * Paired with prepare_to_wait() above so that either
3497 * waitqueue_active() is visible here or !work_is_canceling() is
3498 * visible there.
3499 */
3500 smp_mb();
3501 if (waitqueue_active(&cancel_waitq))
3502 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
3503
3504 return ret;
3505 }
3506
3507 /**
3508 * cancel_work_sync - cancel a work and wait for it to finish
3509 * @work: the work to cancel
3510 *
3511 * Cancel @work and wait for its execution to finish. This function
3512 * can be used even if the work re-queues itself or migrates to
3513 * another workqueue. On return from this function, @work is
3514 * guaranteed to be not pending or executing on any CPU.
3515 *
3516 * cancel_work_sync(&delayed_work->work) must not be used for
3517 * delayed_work's. Use cancel_delayed_work_sync() instead.
3518 *
3519 * The caller must ensure that the workqueue on which @work was last
3520 * queued can't be destroyed before this function returns.
3521 *
3522 * Return:
3523 * %true if @work was pending, %false otherwise.
3524 */
cancel_work_sync(struct work_struct * work)3525 bool cancel_work_sync(struct work_struct *work)
3526 {
3527 return __cancel_work_timer(work, false);
3528 }
3529 EXPORT_SYMBOL_GPL(cancel_work_sync);
3530
3531 /**
3532 * flush_delayed_work - wait for a dwork to finish executing the last queueing
3533 * @dwork: the delayed work to flush
3534 *
3535 * Delayed timer is cancelled and the pending work is queued for
3536 * immediate execution. Like flush_work(), this function only
3537 * considers the last queueing instance of @dwork.
3538 *
3539 * Return:
3540 * %true if flush_work() waited for the work to finish execution,
3541 * %false if it was already idle.
3542 */
flush_delayed_work(struct delayed_work * dwork)3543 bool flush_delayed_work(struct delayed_work *dwork)
3544 {
3545 local_irq_disable();
3546 if (del_timer_sync(&dwork->timer))
3547 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
3548 local_irq_enable();
3549 return flush_work(&dwork->work);
3550 }
3551 EXPORT_SYMBOL(flush_delayed_work);
3552
3553 /**
3554 * flush_rcu_work - wait for a rwork to finish executing the last queueing
3555 * @rwork: the rcu work to flush
3556 *
3557 * Return:
3558 * %true if flush_rcu_work() waited for the work to finish execution,
3559 * %false if it was already idle.
3560 */
flush_rcu_work(struct rcu_work * rwork)3561 bool flush_rcu_work(struct rcu_work *rwork)
3562 {
3563 if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) {
3564 rcu_barrier();
3565 flush_work(&rwork->work);
3566 return true;
3567 } else {
3568 return flush_work(&rwork->work);
3569 }
3570 }
3571 EXPORT_SYMBOL(flush_rcu_work);
3572
__cancel_work(struct work_struct * work,bool is_dwork)3573 static bool __cancel_work(struct work_struct *work, bool is_dwork)
3574 {
3575 unsigned long flags;
3576 int ret;
3577
3578 do {
3579 ret = try_to_grab_pending(work, is_dwork, &flags);
3580 } while (unlikely(ret == -EAGAIN));
3581
3582 if (unlikely(ret < 0))
3583 return false;
3584
3585 set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3586 local_irq_restore(flags);
3587 return ret;
3588 }
3589
3590 /*
3591 * See cancel_delayed_work()
3592 */
cancel_work(struct work_struct * work)3593 bool cancel_work(struct work_struct *work)
3594 {
3595 return __cancel_work(work, false);
3596 }
3597 EXPORT_SYMBOL(cancel_work);
3598
3599 /**
3600 * cancel_delayed_work - cancel a delayed work
3601 * @dwork: delayed_work to cancel
3602 *
3603 * Kill off a pending delayed_work.
3604 *
3605 * Return: %true if @dwork was pending and canceled; %false if it wasn't
3606 * pending.
3607 *
3608 * Note:
3609 * The work callback function may still be running on return, unless
3610 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
3611 * use cancel_delayed_work_sync() to wait on it.
3612 *
3613 * This function is safe to call from any context including IRQ handler.
3614 */
cancel_delayed_work(struct delayed_work * dwork)3615 bool cancel_delayed_work(struct delayed_work *dwork)
3616 {
3617 return __cancel_work(&dwork->work, true);
3618 }
3619 EXPORT_SYMBOL(cancel_delayed_work);
3620
3621 /**
3622 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3623 * @dwork: the delayed work cancel
3624 *
3625 * This is cancel_work_sync() for delayed works.
3626 *
3627 * Return:
3628 * %true if @dwork was pending, %false otherwise.
3629 */
cancel_delayed_work_sync(struct delayed_work * dwork)3630 bool cancel_delayed_work_sync(struct delayed_work *dwork)
3631 {
3632 return __cancel_work_timer(&dwork->work, true);
3633 }
3634 EXPORT_SYMBOL(cancel_delayed_work_sync);
3635
3636 /**
3637 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3638 * @func: the function to call
3639 *
3640 * schedule_on_each_cpu() executes @func on each online CPU using the
3641 * system workqueue and blocks until all CPUs have completed.
3642 * schedule_on_each_cpu() is very slow.
3643 *
3644 * Return:
3645 * 0 on success, -errno on failure.
3646 */
schedule_on_each_cpu(work_func_t func)3647 int schedule_on_each_cpu(work_func_t func)
3648 {
3649 int cpu;
3650 struct work_struct __percpu *works;
3651
3652 works = alloc_percpu(struct work_struct);
3653 if (!works)
3654 return -ENOMEM;
3655
3656 cpus_read_lock();
3657
3658 for_each_online_cpu(cpu) {
3659 struct work_struct *work = per_cpu_ptr(works, cpu);
3660
3661 INIT_WORK(work, func);
3662 schedule_work_on(cpu, work);
3663 }
3664
3665 for_each_online_cpu(cpu)
3666 flush_work(per_cpu_ptr(works, cpu));
3667
3668 cpus_read_unlock();
3669 free_percpu(works);
3670 return 0;
3671 }
3672
3673 /**
3674 * execute_in_process_context - reliably execute the routine with user context
3675 * @fn: the function to execute
3676 * @ew: guaranteed storage for the execute work structure (must
3677 * be available when the work executes)
3678 *
3679 * Executes the function immediately if process context is available,
3680 * otherwise schedules the function for delayed execution.
3681 *
3682 * Return: 0 - function was executed
3683 * 1 - function was scheduled for execution
3684 */
execute_in_process_context(work_func_t fn,struct execute_work * ew)3685 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3686 {
3687 if (!in_interrupt()) {
3688 fn(&ew->work);
3689 return 0;
3690 }
3691
3692 INIT_WORK(&ew->work, fn);
3693 schedule_work(&ew->work);
3694
3695 return 1;
3696 }
3697 EXPORT_SYMBOL_GPL(execute_in_process_context);
3698
3699 /**
3700 * free_workqueue_attrs - free a workqueue_attrs
3701 * @attrs: workqueue_attrs to free
3702 *
3703 * Undo alloc_workqueue_attrs().
3704 */
free_workqueue_attrs(struct workqueue_attrs * attrs)3705 void free_workqueue_attrs(struct workqueue_attrs *attrs)
3706 {
3707 if (attrs) {
3708 free_cpumask_var(attrs->cpumask);
3709 free_cpumask_var(attrs->__pod_cpumask);
3710 kfree(attrs);
3711 }
3712 }
3713
3714 /**
3715 * alloc_workqueue_attrs - allocate a workqueue_attrs
3716 *
3717 * Allocate a new workqueue_attrs, initialize with default settings and
3718 * return it.
3719 *
3720 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3721 */
alloc_workqueue_attrs(void)3722 struct workqueue_attrs *alloc_workqueue_attrs(void)
3723 {
3724 struct workqueue_attrs *attrs;
3725
3726 attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
3727 if (!attrs)
3728 goto fail;
3729 if (!alloc_cpumask_var(&attrs->cpumask, GFP_KERNEL))
3730 goto fail;
3731 if (!alloc_cpumask_var(&attrs->__pod_cpumask, GFP_KERNEL))
3732 goto fail;
3733
3734 cpumask_copy(attrs->cpumask, cpu_possible_mask);
3735 attrs->affn_scope = WQ_AFFN_DFL;
3736 return attrs;
3737 fail:
3738 free_workqueue_attrs(attrs);
3739 return NULL;
3740 }
3741
copy_workqueue_attrs(struct workqueue_attrs * to,const struct workqueue_attrs * from)3742 static void copy_workqueue_attrs(struct workqueue_attrs *to,
3743 const struct workqueue_attrs *from)
3744 {
3745 to->nice = from->nice;
3746 cpumask_copy(to->cpumask, from->cpumask);
3747 cpumask_copy(to->__pod_cpumask, from->__pod_cpumask);
3748 to->affn_strict = from->affn_strict;
3749
3750 /*
3751 * Unlike hash and equality test, copying shouldn't ignore wq-only
3752 * fields as copying is used for both pool and wq attrs. Instead,
3753 * get_unbound_pool() explicitly clears the fields.
3754 */
3755 to->affn_scope = from->affn_scope;
3756 to->ordered = from->ordered;
3757 }
3758
3759 /*
3760 * Some attrs fields are workqueue-only. Clear them for worker_pool's. See the
3761 * comments in 'struct workqueue_attrs' definition.
3762 */
wqattrs_clear_for_pool(struct workqueue_attrs * attrs)3763 static void wqattrs_clear_for_pool(struct workqueue_attrs *attrs)
3764 {
3765 attrs->affn_scope = WQ_AFFN_NR_TYPES;
3766 attrs->ordered = false;
3767 }
3768
3769 /* hash value of the content of @attr */
wqattrs_hash(const struct workqueue_attrs * attrs)3770 static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3771 {
3772 u32 hash = 0;
3773
3774 hash = jhash_1word(attrs->nice, hash);
3775 hash = jhash(cpumask_bits(attrs->cpumask),
3776 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3777 hash = jhash(cpumask_bits(attrs->__pod_cpumask),
3778 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3779 hash = jhash_1word(attrs->affn_strict, hash);
3780 return hash;
3781 }
3782
3783 /* content equality test */
wqattrs_equal(const struct workqueue_attrs * a,const struct workqueue_attrs * b)3784 static bool wqattrs_equal(const struct workqueue_attrs *a,
3785 const struct workqueue_attrs *b)
3786 {
3787 if (a->nice != b->nice)
3788 return false;
3789 if (!cpumask_equal(a->cpumask, b->cpumask))
3790 return false;
3791 if (!cpumask_equal(a->__pod_cpumask, b->__pod_cpumask))
3792 return false;
3793 if (a->affn_strict != b->affn_strict)
3794 return false;
3795 return true;
3796 }
3797
3798 /* Update @attrs with actually available CPUs */
wqattrs_actualize_cpumask(struct workqueue_attrs * attrs,const cpumask_t * unbound_cpumask)3799 static void wqattrs_actualize_cpumask(struct workqueue_attrs *attrs,
3800 const cpumask_t *unbound_cpumask)
3801 {
3802 /*
3803 * Calculate the effective CPU mask of @attrs given @unbound_cpumask. If
3804 * @attrs->cpumask doesn't overlap with @unbound_cpumask, we fallback to
3805 * @unbound_cpumask.
3806 */
3807 cpumask_and(attrs->cpumask, attrs->cpumask, unbound_cpumask);
3808 if (unlikely(cpumask_empty(attrs->cpumask)))
3809 cpumask_copy(attrs->cpumask, unbound_cpumask);
3810 }
3811
3812 /* find wq_pod_type to use for @attrs */
3813 static const struct wq_pod_type *
wqattrs_pod_type(const struct workqueue_attrs * attrs)3814 wqattrs_pod_type(const struct workqueue_attrs *attrs)
3815 {
3816 enum wq_affn_scope scope;
3817 struct wq_pod_type *pt;
3818
3819 /* to synchronize access to wq_affn_dfl */
3820 lockdep_assert_held(&wq_pool_mutex);
3821
3822 if (attrs->affn_scope == WQ_AFFN_DFL)
3823 scope = wq_affn_dfl;
3824 else
3825 scope = attrs->affn_scope;
3826
3827 pt = &wq_pod_types[scope];
3828
3829 if (!WARN_ON_ONCE(attrs->affn_scope == WQ_AFFN_NR_TYPES) &&
3830 likely(pt->nr_pods))
3831 return pt;
3832
3833 /*
3834 * Before workqueue_init_topology(), only SYSTEM is available which is
3835 * initialized in workqueue_init_early().
3836 */
3837 pt = &wq_pod_types[WQ_AFFN_SYSTEM];
3838 BUG_ON(!pt->nr_pods);
3839 return pt;
3840 }
3841
3842 /**
3843 * init_worker_pool - initialize a newly zalloc'd worker_pool
3844 * @pool: worker_pool to initialize
3845 *
3846 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
3847 *
3848 * Return: 0 on success, -errno on failure. Even on failure, all fields
3849 * inside @pool proper are initialized and put_unbound_pool() can be called
3850 * on @pool safely to release it.
3851 */
init_worker_pool(struct worker_pool * pool)3852 static int init_worker_pool(struct worker_pool *pool)
3853 {
3854 raw_spin_lock_init(&pool->lock);
3855 pool->id = -1;
3856 pool->cpu = -1;
3857 pool->node = NUMA_NO_NODE;
3858 pool->flags |= POOL_DISASSOCIATED;
3859 pool->watchdog_ts = jiffies;
3860 INIT_LIST_HEAD(&pool->worklist);
3861 INIT_LIST_HEAD(&pool->idle_list);
3862 hash_init(pool->busy_hash);
3863
3864 timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
3865 INIT_WORK(&pool->idle_cull_work, idle_cull_fn);
3866
3867 timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
3868
3869 INIT_LIST_HEAD(&pool->workers);
3870 INIT_LIST_HEAD(&pool->dying_workers);
3871
3872 ida_init(&pool->worker_ida);
3873 INIT_HLIST_NODE(&pool->hash_node);
3874 pool->refcnt = 1;
3875
3876 /* shouldn't fail above this point */
3877 pool->attrs = alloc_workqueue_attrs();
3878 if (!pool->attrs)
3879 return -ENOMEM;
3880
3881 wqattrs_clear_for_pool(pool->attrs);
3882
3883 return 0;
3884 }
3885
3886 #ifdef CONFIG_LOCKDEP
wq_init_lockdep(struct workqueue_struct * wq)3887 static void wq_init_lockdep(struct workqueue_struct *wq)
3888 {
3889 char *lock_name;
3890
3891 lockdep_register_key(&wq->key);
3892 lock_name = kasprintf(GFP_KERNEL, "%s%s", "(wq_completion)", wq->name);
3893 if (!lock_name)
3894 lock_name = wq->name;
3895
3896 wq->lock_name = lock_name;
3897 lockdep_init_map(&wq->lockdep_map, lock_name, &wq->key, 0);
3898 }
3899
wq_unregister_lockdep(struct workqueue_struct * wq)3900 static void wq_unregister_lockdep(struct workqueue_struct *wq)
3901 {
3902 lockdep_unregister_key(&wq->key);
3903 }
3904
wq_free_lockdep(struct workqueue_struct * wq)3905 static void wq_free_lockdep(struct workqueue_struct *wq)
3906 {
3907 if (wq->lock_name != wq->name)
3908 kfree(wq->lock_name);
3909 }
3910 #else
wq_init_lockdep(struct workqueue_struct * wq)3911 static void wq_init_lockdep(struct workqueue_struct *wq)
3912 {
3913 }
3914
wq_unregister_lockdep(struct workqueue_struct * wq)3915 static void wq_unregister_lockdep(struct workqueue_struct *wq)
3916 {
3917 }
3918
wq_free_lockdep(struct workqueue_struct * wq)3919 static void wq_free_lockdep(struct workqueue_struct *wq)
3920 {
3921 }
3922 #endif
3923
rcu_free_wq(struct rcu_head * rcu)3924 static void rcu_free_wq(struct rcu_head *rcu)
3925 {
3926 struct workqueue_struct *wq =
3927 container_of(rcu, struct workqueue_struct, rcu);
3928
3929 wq_free_lockdep(wq);
3930 free_percpu(wq->cpu_pwq);
3931 free_workqueue_attrs(wq->unbound_attrs);
3932 kfree(wq);
3933 }
3934
rcu_free_pool(struct rcu_head * rcu)3935 static void rcu_free_pool(struct rcu_head *rcu)
3936 {
3937 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3938
3939 ida_destroy(&pool->worker_ida);
3940 free_workqueue_attrs(pool->attrs);
3941 kfree(pool);
3942 }
3943
3944 /**
3945 * put_unbound_pool - put a worker_pool
3946 * @pool: worker_pool to put
3947 *
3948 * Put @pool. If its refcnt reaches zero, it gets destroyed in RCU
3949 * safe manner. get_unbound_pool() calls this function on its failure path
3950 * and this function should be able to release pools which went through,
3951 * successfully or not, init_worker_pool().
3952 *
3953 * Should be called with wq_pool_mutex held.
3954 */
put_unbound_pool(struct worker_pool * pool)3955 static void put_unbound_pool(struct worker_pool *pool)
3956 {
3957 DECLARE_COMPLETION_ONSTACK(detach_completion);
3958 struct worker *worker;
3959 LIST_HEAD(cull_list);
3960
3961 lockdep_assert_held(&wq_pool_mutex);
3962
3963 if (--pool->refcnt)
3964 return;
3965
3966 /* sanity checks */
3967 if (WARN_ON(!(pool->cpu < 0)) ||
3968 WARN_ON(!list_empty(&pool->worklist)))
3969 return;
3970
3971 /* release id and unhash */
3972 if (pool->id >= 0)
3973 idr_remove(&worker_pool_idr, pool->id);
3974 hash_del(&pool->hash_node);
3975
3976 /*
3977 * Become the manager and destroy all workers. This prevents
3978 * @pool's workers from blocking on attach_mutex. We're the last
3979 * manager and @pool gets freed with the flag set.
3980 *
3981 * Having a concurrent manager is quite unlikely to happen as we can
3982 * only get here with
3983 * pwq->refcnt == pool->refcnt == 0
3984 * which implies no work queued to the pool, which implies no worker can
3985 * become the manager. However a worker could have taken the role of
3986 * manager before the refcnts dropped to 0, since maybe_create_worker()
3987 * drops pool->lock
3988 */
3989 while (true) {
3990 rcuwait_wait_event(&manager_wait,
3991 !(pool->flags & POOL_MANAGER_ACTIVE),
3992 TASK_UNINTERRUPTIBLE);
3993
3994 mutex_lock(&wq_pool_attach_mutex);
3995 raw_spin_lock_irq(&pool->lock);
3996 if (!(pool->flags & POOL_MANAGER_ACTIVE)) {
3997 pool->flags |= POOL_MANAGER_ACTIVE;
3998 break;
3999 }
4000 raw_spin_unlock_irq(&pool->lock);
4001 mutex_unlock(&wq_pool_attach_mutex);
4002 }
4003
4004 while ((worker = first_idle_worker(pool)))
4005 set_worker_dying(worker, &cull_list);
4006 WARN_ON(pool->nr_workers || pool->nr_idle);
4007 raw_spin_unlock_irq(&pool->lock);
4008
4009 wake_dying_workers(&cull_list);
4010
4011 if (!list_empty(&pool->workers) || !list_empty(&pool->dying_workers))
4012 pool->detach_completion = &detach_completion;
4013 mutex_unlock(&wq_pool_attach_mutex);
4014
4015 if (pool->detach_completion)
4016 wait_for_completion(pool->detach_completion);
4017
4018 /* shut down the timers */
4019 del_timer_sync(&pool->idle_timer);
4020 cancel_work_sync(&pool->idle_cull_work);
4021 del_timer_sync(&pool->mayday_timer);
4022
4023 /* RCU protected to allow dereferences from get_work_pool() */
4024 call_rcu(&pool->rcu, rcu_free_pool);
4025 }
4026
4027 /**
4028 * get_unbound_pool - get a worker_pool with the specified attributes
4029 * @attrs: the attributes of the worker_pool to get
4030 *
4031 * Obtain a worker_pool which has the same attributes as @attrs, bump the
4032 * reference count and return it. If there already is a matching
4033 * worker_pool, it will be used; otherwise, this function attempts to
4034 * create a new one.
4035 *
4036 * Should be called with wq_pool_mutex held.
4037 *
4038 * Return: On success, a worker_pool with the same attributes as @attrs.
4039 * On failure, %NULL.
4040 */
get_unbound_pool(const struct workqueue_attrs * attrs)4041 static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
4042 {
4043 struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_NUMA];
4044 u32 hash = wqattrs_hash(attrs);
4045 struct worker_pool *pool;
4046 int pod, node = NUMA_NO_NODE;
4047
4048 lockdep_assert_held(&wq_pool_mutex);
4049
4050 /* do we already have a matching pool? */
4051 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
4052 if (wqattrs_equal(pool->attrs, attrs)) {
4053 pool->refcnt++;
4054 return pool;
4055 }
4056 }
4057
4058 /* If __pod_cpumask is contained inside a NUMA pod, that's our node */
4059 for (pod = 0; pod < pt->nr_pods; pod++) {
4060 if (cpumask_subset(attrs->__pod_cpumask, pt->pod_cpus[pod])) {
4061 node = pt->pod_node[pod];
4062 break;
4063 }
4064 }
4065
4066 /* nope, create a new one */
4067 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, node);
4068 if (!pool || init_worker_pool(pool) < 0)
4069 goto fail;
4070
4071 pool->node = node;
4072 copy_workqueue_attrs(pool->attrs, attrs);
4073 wqattrs_clear_for_pool(pool->attrs);
4074
4075 if (worker_pool_assign_id(pool) < 0)
4076 goto fail;
4077
4078 /* create and start the initial worker */
4079 if (wq_online && !create_worker(pool))
4080 goto fail;
4081
4082 /* install */
4083 hash_add(unbound_pool_hash, &pool->hash_node, hash);
4084
4085 return pool;
4086 fail:
4087 if (pool)
4088 put_unbound_pool(pool);
4089 return NULL;
4090 }
4091
rcu_free_pwq(struct rcu_head * rcu)4092 static void rcu_free_pwq(struct rcu_head *rcu)
4093 {
4094 kmem_cache_free(pwq_cache,
4095 container_of(rcu, struct pool_workqueue, rcu));
4096 }
4097
4098 /*
4099 * Scheduled on pwq_release_worker by put_pwq() when an unbound pwq hits zero
4100 * refcnt and needs to be destroyed.
4101 */
pwq_release_workfn(struct kthread_work * work)4102 static void pwq_release_workfn(struct kthread_work *work)
4103 {
4104 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
4105 release_work);
4106 struct workqueue_struct *wq = pwq->wq;
4107 struct worker_pool *pool = pwq->pool;
4108 bool is_last = false;
4109
4110 /*
4111 * When @pwq is not linked, it doesn't hold any reference to the
4112 * @wq, and @wq is invalid to access.
4113 */
4114 if (!list_empty(&pwq->pwqs_node)) {
4115 mutex_lock(&wq->mutex);
4116 list_del_rcu(&pwq->pwqs_node);
4117 is_last = list_empty(&wq->pwqs);
4118 mutex_unlock(&wq->mutex);
4119 }
4120
4121 if (wq->flags & WQ_UNBOUND) {
4122 mutex_lock(&wq_pool_mutex);
4123 put_unbound_pool(pool);
4124 mutex_unlock(&wq_pool_mutex);
4125 }
4126
4127 call_rcu(&pwq->rcu, rcu_free_pwq);
4128
4129 /*
4130 * If we're the last pwq going away, @wq is already dead and no one
4131 * is gonna access it anymore. Schedule RCU free.
4132 */
4133 if (is_last) {
4134 wq_unregister_lockdep(wq);
4135 call_rcu(&wq->rcu, rcu_free_wq);
4136 }
4137 }
4138
4139 /**
4140 * pwq_adjust_max_active - update a pwq's max_active to the current setting
4141 * @pwq: target pool_workqueue
4142 *
4143 * If @pwq isn't freezing, set @pwq->max_active to the associated
4144 * workqueue's saved_max_active and activate inactive work items
4145 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
4146 */
pwq_adjust_max_active(struct pool_workqueue * pwq)4147 static void pwq_adjust_max_active(struct pool_workqueue *pwq)
4148 {
4149 struct workqueue_struct *wq = pwq->wq;
4150 bool freezable = wq->flags & WQ_FREEZABLE;
4151 unsigned long flags;
4152
4153 /* for @wq->saved_max_active */
4154 lockdep_assert_held(&wq->mutex);
4155
4156 /* fast exit for non-freezable wqs */
4157 if (!freezable && pwq->max_active == wq->saved_max_active)
4158 return;
4159
4160 /* this function can be called during early boot w/ irq disabled */
4161 raw_spin_lock_irqsave(&pwq->pool->lock, flags);
4162
4163 /*
4164 * During [un]freezing, the caller is responsible for ensuring that
4165 * this function is called at least once after @workqueue_freezing
4166 * is updated and visible.
4167 */
4168 if (!freezable || !workqueue_freezing) {
4169 pwq->max_active = wq->saved_max_active;
4170
4171 while (!list_empty(&pwq->inactive_works) &&
4172 pwq->nr_active < pwq->max_active)
4173 pwq_activate_first_inactive(pwq);
4174
4175 kick_pool(pwq->pool);
4176 } else {
4177 pwq->max_active = 0;
4178 }
4179
4180 raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
4181 }
4182
4183 /* initialize newly allocated @pwq which is associated with @wq and @pool */
init_pwq(struct pool_workqueue * pwq,struct workqueue_struct * wq,struct worker_pool * pool)4184 static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
4185 struct worker_pool *pool)
4186 {
4187 BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
4188
4189 memset(pwq, 0, sizeof(*pwq));
4190
4191 pwq->pool = pool;
4192 pwq->wq = wq;
4193 pwq->flush_color = -1;
4194 pwq->refcnt = 1;
4195 INIT_LIST_HEAD(&pwq->inactive_works);
4196 INIT_LIST_HEAD(&pwq->pwqs_node);
4197 INIT_LIST_HEAD(&pwq->mayday_node);
4198 kthread_init_work(&pwq->release_work, pwq_release_workfn);
4199 }
4200
4201 /* sync @pwq with the current state of its associated wq and link it */
link_pwq(struct pool_workqueue * pwq)4202 static void link_pwq(struct pool_workqueue *pwq)
4203 {
4204 struct workqueue_struct *wq = pwq->wq;
4205
4206 lockdep_assert_held(&wq->mutex);
4207
4208 /* may be called multiple times, ignore if already linked */
4209 if (!list_empty(&pwq->pwqs_node))
4210 return;
4211
4212 /* set the matching work_color */
4213 pwq->work_color = wq->work_color;
4214
4215 /* sync max_active to the current setting */
4216 pwq_adjust_max_active(pwq);
4217
4218 /* link in @pwq */
4219 list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
4220 }
4221
4222 /* obtain a pool matching @attr and create a pwq associating the pool and @wq */
alloc_unbound_pwq(struct workqueue_struct * wq,const struct workqueue_attrs * attrs)4223 static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
4224 const struct workqueue_attrs *attrs)
4225 {
4226 struct worker_pool *pool;
4227 struct pool_workqueue *pwq;
4228
4229 lockdep_assert_held(&wq_pool_mutex);
4230
4231 pool = get_unbound_pool(attrs);
4232 if (!pool)
4233 return NULL;
4234
4235 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
4236 if (!pwq) {
4237 put_unbound_pool(pool);
4238 return NULL;
4239 }
4240
4241 init_pwq(pwq, wq, pool);
4242 return pwq;
4243 }
4244
4245 /**
4246 * wq_calc_pod_cpumask - calculate a wq_attrs' cpumask for a pod
4247 * @attrs: the wq_attrs of the default pwq of the target workqueue
4248 * @cpu: the target CPU
4249 * @cpu_going_down: if >= 0, the CPU to consider as offline
4250 *
4251 * Calculate the cpumask a workqueue with @attrs should use on @pod. If
4252 * @cpu_going_down is >= 0, that cpu is considered offline during calculation.
4253 * The result is stored in @attrs->__pod_cpumask.
4254 *
4255 * If pod affinity is not enabled, @attrs->cpumask is always used. If enabled
4256 * and @pod has online CPUs requested by @attrs, the returned cpumask is the
4257 * intersection of the possible CPUs of @pod and @attrs->cpumask.
4258 *
4259 * The caller is responsible for ensuring that the cpumask of @pod stays stable.
4260 */
wq_calc_pod_cpumask(struct workqueue_attrs * attrs,int cpu,int cpu_going_down)4261 static void wq_calc_pod_cpumask(struct workqueue_attrs *attrs, int cpu,
4262 int cpu_going_down)
4263 {
4264 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
4265 int pod = pt->cpu_pod[cpu];
4266
4267 /* does @pod have any online CPUs @attrs wants? */
4268 cpumask_and(attrs->__pod_cpumask, pt->pod_cpus[pod], attrs->cpumask);
4269 cpumask_and(attrs->__pod_cpumask, attrs->__pod_cpumask, cpu_online_mask);
4270 if (cpu_going_down >= 0)
4271 cpumask_clear_cpu(cpu_going_down, attrs->__pod_cpumask);
4272
4273 if (cpumask_empty(attrs->__pod_cpumask)) {
4274 cpumask_copy(attrs->__pod_cpumask, attrs->cpumask);
4275 return;
4276 }
4277
4278 /* yeap, return possible CPUs in @pod that @attrs wants */
4279 cpumask_and(attrs->__pod_cpumask, attrs->cpumask, pt->pod_cpus[pod]);
4280
4281 if (cpumask_empty(attrs->__pod_cpumask))
4282 pr_warn_once("WARNING: workqueue cpumask: online intersect > "
4283 "possible intersect\n");
4284 }
4285
4286 /* install @pwq into @wq's cpu_pwq and return the old pwq */
install_unbound_pwq(struct workqueue_struct * wq,int cpu,struct pool_workqueue * pwq)4287 static struct pool_workqueue *install_unbound_pwq(struct workqueue_struct *wq,
4288 int cpu, struct pool_workqueue *pwq)
4289 {
4290 struct pool_workqueue *old_pwq;
4291
4292 lockdep_assert_held(&wq_pool_mutex);
4293 lockdep_assert_held(&wq->mutex);
4294
4295 /* link_pwq() can handle duplicate calls */
4296 link_pwq(pwq);
4297
4298 old_pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
4299 rcu_assign_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu), pwq);
4300 return old_pwq;
4301 }
4302
4303 /* context to store the prepared attrs & pwqs before applying */
4304 struct apply_wqattrs_ctx {
4305 struct workqueue_struct *wq; /* target workqueue */
4306 struct workqueue_attrs *attrs; /* attrs to apply */
4307 struct list_head list; /* queued for batching commit */
4308 struct pool_workqueue *dfl_pwq;
4309 struct pool_workqueue *pwq_tbl[];
4310 };
4311
4312 /* free the resources after success or abort */
apply_wqattrs_cleanup(struct apply_wqattrs_ctx * ctx)4313 static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
4314 {
4315 if (ctx) {
4316 int cpu;
4317
4318 for_each_possible_cpu(cpu)
4319 put_pwq_unlocked(ctx->pwq_tbl[cpu]);
4320 put_pwq_unlocked(ctx->dfl_pwq);
4321
4322 free_workqueue_attrs(ctx->attrs);
4323
4324 kfree(ctx);
4325 }
4326 }
4327
4328 /* allocate the attrs and pwqs for later installation */
4329 static struct apply_wqattrs_ctx *
apply_wqattrs_prepare(struct workqueue_struct * wq,const struct workqueue_attrs * attrs,const cpumask_var_t unbound_cpumask)4330 apply_wqattrs_prepare(struct workqueue_struct *wq,
4331 const struct workqueue_attrs *attrs,
4332 const cpumask_var_t unbound_cpumask)
4333 {
4334 struct apply_wqattrs_ctx *ctx;
4335 struct workqueue_attrs *new_attrs;
4336 int cpu;
4337
4338 lockdep_assert_held(&wq_pool_mutex);
4339
4340 if (WARN_ON(attrs->affn_scope < 0 ||
4341 attrs->affn_scope >= WQ_AFFN_NR_TYPES))
4342 return ERR_PTR(-EINVAL);
4343
4344 ctx = kzalloc(struct_size(ctx, pwq_tbl, nr_cpu_ids), GFP_KERNEL);
4345
4346 new_attrs = alloc_workqueue_attrs();
4347 if (!ctx || !new_attrs)
4348 goto out_free;
4349
4350 /*
4351 * If something goes wrong during CPU up/down, we'll fall back to
4352 * the default pwq covering whole @attrs->cpumask. Always create
4353 * it even if we don't use it immediately.
4354 */
4355 copy_workqueue_attrs(new_attrs, attrs);
4356 wqattrs_actualize_cpumask(new_attrs, unbound_cpumask);
4357 cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
4358 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
4359 if (!ctx->dfl_pwq)
4360 goto out_free;
4361
4362 for_each_possible_cpu(cpu) {
4363 if (new_attrs->ordered) {
4364 ctx->dfl_pwq->refcnt++;
4365 ctx->pwq_tbl[cpu] = ctx->dfl_pwq;
4366 } else {
4367 wq_calc_pod_cpumask(new_attrs, cpu, -1);
4368 ctx->pwq_tbl[cpu] = alloc_unbound_pwq(wq, new_attrs);
4369 if (!ctx->pwq_tbl[cpu])
4370 goto out_free;
4371 }
4372 }
4373
4374 /* save the user configured attrs and sanitize it. */
4375 copy_workqueue_attrs(new_attrs, attrs);
4376 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
4377 cpumask_copy(new_attrs->__pod_cpumask, new_attrs->cpumask);
4378 ctx->attrs = new_attrs;
4379
4380 ctx->wq = wq;
4381 return ctx;
4382
4383 out_free:
4384 free_workqueue_attrs(new_attrs);
4385 apply_wqattrs_cleanup(ctx);
4386 return ERR_PTR(-ENOMEM);
4387 }
4388
4389 /* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
apply_wqattrs_commit(struct apply_wqattrs_ctx * ctx)4390 static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
4391 {
4392 int cpu;
4393
4394 /* all pwqs have been created successfully, let's install'em */
4395 mutex_lock(&ctx->wq->mutex);
4396
4397 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
4398
4399 /* save the previous pwq and install the new one */
4400 for_each_possible_cpu(cpu)
4401 ctx->pwq_tbl[cpu] = install_unbound_pwq(ctx->wq, cpu,
4402 ctx->pwq_tbl[cpu]);
4403
4404 /* @dfl_pwq might not have been used, ensure it's linked */
4405 link_pwq(ctx->dfl_pwq);
4406 swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
4407
4408 mutex_unlock(&ctx->wq->mutex);
4409 }
4410
apply_wqattrs_lock(void)4411 static void apply_wqattrs_lock(void)
4412 {
4413 /* CPUs should stay stable across pwq creations and installations */
4414 cpus_read_lock();
4415 mutex_lock(&wq_pool_mutex);
4416 }
4417
apply_wqattrs_unlock(void)4418 static void apply_wqattrs_unlock(void)
4419 {
4420 mutex_unlock(&wq_pool_mutex);
4421 cpus_read_unlock();
4422 }
4423
apply_workqueue_attrs_locked(struct workqueue_struct * wq,const struct workqueue_attrs * attrs)4424 static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
4425 const struct workqueue_attrs *attrs)
4426 {
4427 struct apply_wqattrs_ctx *ctx;
4428
4429 /* only unbound workqueues can change attributes */
4430 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
4431 return -EINVAL;
4432
4433 /* creating multiple pwqs breaks ordering guarantee */
4434 if (!list_empty(&wq->pwqs)) {
4435 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4436 return -EINVAL;
4437
4438 wq->flags &= ~__WQ_ORDERED;
4439 }
4440
4441 ctx = apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask);
4442 if (IS_ERR(ctx))
4443 return PTR_ERR(ctx);
4444
4445 /* the ctx has been prepared successfully, let's commit it */
4446 apply_wqattrs_commit(ctx);
4447 apply_wqattrs_cleanup(ctx);
4448
4449 return 0;
4450 }
4451
4452 /**
4453 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
4454 * @wq: the target workqueue
4455 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
4456 *
4457 * Apply @attrs to an unbound workqueue @wq. Unless disabled, this function maps
4458 * a separate pwq to each CPU pod with possibles CPUs in @attrs->cpumask so that
4459 * work items are affine to the pod it was issued on. Older pwqs are released as
4460 * in-flight work items finish. Note that a work item which repeatedly requeues
4461 * itself back-to-back will stay on its current pwq.
4462 *
4463 * Performs GFP_KERNEL allocations.
4464 *
4465 * Assumes caller has CPU hotplug read exclusion, i.e. cpus_read_lock().
4466 *
4467 * Return: 0 on success and -errno on failure.
4468 */
apply_workqueue_attrs(struct workqueue_struct * wq,const struct workqueue_attrs * attrs)4469 int apply_workqueue_attrs(struct workqueue_struct *wq,
4470 const struct workqueue_attrs *attrs)
4471 {
4472 int ret;
4473
4474 lockdep_assert_cpus_held();
4475
4476 mutex_lock(&wq_pool_mutex);
4477 ret = apply_workqueue_attrs_locked(wq, attrs);
4478 mutex_unlock(&wq_pool_mutex);
4479
4480 return ret;
4481 }
4482
4483 /**
4484 * wq_update_pod - update pod affinity of a wq for CPU hot[un]plug
4485 * @wq: the target workqueue
4486 * @cpu: the CPU to update pool association for
4487 * @hotplug_cpu: the CPU coming up or going down
4488 * @online: whether @cpu is coming up or going down
4489 *
4490 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
4491 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update pod affinity of
4492 * @wq accordingly.
4493 *
4494 *
4495 * If pod affinity can't be adjusted due to memory allocation failure, it falls
4496 * back to @wq->dfl_pwq which may not be optimal but is always correct.
4497 *
4498 * Note that when the last allowed CPU of a pod goes offline for a workqueue
4499 * with a cpumask spanning multiple pods, the workers which were already
4500 * executing the work items for the workqueue will lose their CPU affinity and
4501 * may execute on any CPU. This is similar to how per-cpu workqueues behave on
4502 * CPU_DOWN. If a workqueue user wants strict affinity, it's the user's
4503 * responsibility to flush the work item from CPU_DOWN_PREPARE.
4504 */
wq_update_pod(struct workqueue_struct * wq,int cpu,int hotplug_cpu,bool online)4505 static void wq_update_pod(struct workqueue_struct *wq, int cpu,
4506 int hotplug_cpu, bool online)
4507 {
4508 int off_cpu = online ? -1 : hotplug_cpu;
4509 struct pool_workqueue *old_pwq = NULL, *pwq;
4510 struct workqueue_attrs *target_attrs;
4511
4512 lockdep_assert_held(&wq_pool_mutex);
4513
4514 if (!(wq->flags & WQ_UNBOUND) || wq->unbound_attrs->ordered)
4515 return;
4516
4517 /*
4518 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
4519 * Let's use a preallocated one. The following buf is protected by
4520 * CPU hotplug exclusion.
4521 */
4522 target_attrs = wq_update_pod_attrs_buf;
4523
4524 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
4525 wqattrs_actualize_cpumask(target_attrs, wq_unbound_cpumask);
4526
4527 /* nothing to do if the target cpumask matches the current pwq */
4528 wq_calc_pod_cpumask(target_attrs, cpu, off_cpu);
4529 pwq = rcu_dereference_protected(*per_cpu_ptr(wq->cpu_pwq, cpu),
4530 lockdep_is_held(&wq_pool_mutex));
4531 if (wqattrs_equal(target_attrs, pwq->pool->attrs))
4532 return;
4533
4534 /* create a new pwq */
4535 pwq = alloc_unbound_pwq(wq, target_attrs);
4536 if (!pwq) {
4537 pr_warn("workqueue: allocation failed while updating CPU pod affinity of \"%s\"\n",
4538 wq->name);
4539 goto use_dfl_pwq;
4540 }
4541
4542 /* Install the new pwq. */
4543 mutex_lock(&wq->mutex);
4544 old_pwq = install_unbound_pwq(wq, cpu, pwq);
4545 goto out_unlock;
4546
4547 use_dfl_pwq:
4548 mutex_lock(&wq->mutex);
4549 raw_spin_lock_irq(&wq->dfl_pwq->pool->lock);
4550 get_pwq(wq->dfl_pwq);
4551 raw_spin_unlock_irq(&wq->dfl_pwq->pool->lock);
4552 old_pwq = install_unbound_pwq(wq, cpu, wq->dfl_pwq);
4553 out_unlock:
4554 mutex_unlock(&wq->mutex);
4555 put_pwq_unlocked(old_pwq);
4556 }
4557
alloc_and_link_pwqs(struct workqueue_struct * wq)4558 static int alloc_and_link_pwqs(struct workqueue_struct *wq)
4559 {
4560 bool highpri = wq->flags & WQ_HIGHPRI;
4561 int cpu, ret;
4562
4563 wq->cpu_pwq = alloc_percpu(struct pool_workqueue *);
4564 if (!wq->cpu_pwq)
4565 goto enomem;
4566
4567 if (!(wq->flags & WQ_UNBOUND)) {
4568 for_each_possible_cpu(cpu) {
4569 struct pool_workqueue **pwq_p =
4570 per_cpu_ptr(wq->cpu_pwq, cpu);
4571 struct worker_pool *pool =
4572 &(per_cpu_ptr(cpu_worker_pools, cpu)[highpri]);
4573
4574 *pwq_p = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL,
4575 pool->node);
4576 if (!*pwq_p)
4577 goto enomem;
4578
4579 init_pwq(*pwq_p, wq, pool);
4580
4581 mutex_lock(&wq->mutex);
4582 link_pwq(*pwq_p);
4583 mutex_unlock(&wq->mutex);
4584 }
4585 return 0;
4586 }
4587
4588 cpus_read_lock();
4589 if (wq->flags & __WQ_ORDERED) {
4590 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
4591 /* there should only be single pwq for ordering guarantee */
4592 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
4593 wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
4594 "ordering guarantee broken for workqueue %s\n", wq->name);
4595 } else {
4596 ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
4597 }
4598 cpus_read_unlock();
4599
4600 /* for unbound pwq, flush the pwq_release_worker ensures that the
4601 * pwq_release_workfn() completes before calling kfree(wq).
4602 */
4603 if (ret)
4604 kthread_flush_worker(pwq_release_worker);
4605
4606 return ret;
4607
4608 enomem:
4609 if (wq->cpu_pwq) {
4610 for_each_possible_cpu(cpu) {
4611 struct pool_workqueue *pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
4612
4613 if (pwq)
4614 kmem_cache_free(pwq_cache, pwq);
4615 }
4616 free_percpu(wq->cpu_pwq);
4617 wq->cpu_pwq = NULL;
4618 }
4619 return -ENOMEM;
4620 }
4621
wq_clamp_max_active(int max_active,unsigned int flags,const char * name)4622 static int wq_clamp_max_active(int max_active, unsigned int flags,
4623 const char *name)
4624 {
4625 if (max_active < 1 || max_active > WQ_MAX_ACTIVE)
4626 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
4627 max_active, name, 1, WQ_MAX_ACTIVE);
4628
4629 return clamp_val(max_active, 1, WQ_MAX_ACTIVE);
4630 }
4631
4632 /*
4633 * Workqueues which may be used during memory reclaim should have a rescuer
4634 * to guarantee forward progress.
4635 */
init_rescuer(struct workqueue_struct * wq)4636 static int init_rescuer(struct workqueue_struct *wq)
4637 {
4638 struct worker *rescuer;
4639 int ret;
4640
4641 if (!(wq->flags & WQ_MEM_RECLAIM))
4642 return 0;
4643
4644 rescuer = alloc_worker(NUMA_NO_NODE);
4645 if (!rescuer) {
4646 pr_err("workqueue: Failed to allocate a rescuer for wq \"%s\"\n",
4647 wq->name);
4648 return -ENOMEM;
4649 }
4650
4651 rescuer->rescue_wq = wq;
4652 rescuer->task = kthread_create(rescuer_thread, rescuer, "kworker/R-%s", wq->name);
4653 if (IS_ERR(rescuer->task)) {
4654 ret = PTR_ERR(rescuer->task);
4655 pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %pe",
4656 wq->name, ERR_PTR(ret));
4657 kfree(rescuer);
4658 return ret;
4659 }
4660
4661 wq->rescuer = rescuer;
4662 kthread_bind_mask(rescuer->task, cpu_possible_mask);
4663 wake_up_process(rescuer->task);
4664
4665 return 0;
4666 }
4667
4668 __printf(1, 4)
alloc_workqueue(const char * fmt,unsigned int flags,int max_active,...)4669 struct workqueue_struct *alloc_workqueue(const char *fmt,
4670 unsigned int flags,
4671 int max_active, ...)
4672 {
4673 va_list args;
4674 struct workqueue_struct *wq;
4675 struct pool_workqueue *pwq;
4676
4677 /*
4678 * Unbound && max_active == 1 used to imply ordered, which is no longer
4679 * the case on many machines due to per-pod pools. While
4680 * alloc_ordered_workqueue() is the right way to create an ordered
4681 * workqueue, keep the previous behavior to avoid subtle breakages.
4682 */
4683 if ((flags & WQ_UNBOUND) && max_active == 1)
4684 flags |= __WQ_ORDERED;
4685
4686 /* see the comment above the definition of WQ_POWER_EFFICIENT */
4687 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
4688 flags |= WQ_UNBOUND;
4689
4690 /* allocate wq and format name */
4691 wq = kzalloc(sizeof(*wq), GFP_KERNEL);
4692 if (!wq)
4693 return NULL;
4694
4695 if (flags & WQ_UNBOUND) {
4696 wq->unbound_attrs = alloc_workqueue_attrs();
4697 if (!wq->unbound_attrs)
4698 goto err_free_wq;
4699 }
4700
4701 va_start(args, max_active);
4702 vsnprintf(wq->name, sizeof(wq->name), fmt, args);
4703 va_end(args);
4704
4705 max_active = max_active ?: WQ_DFL_ACTIVE;
4706 max_active = wq_clamp_max_active(max_active, flags, wq->name);
4707
4708 /* init wq */
4709 wq->flags = flags;
4710 wq->saved_max_active = max_active;
4711 mutex_init(&wq->mutex);
4712 atomic_set(&wq->nr_pwqs_to_flush, 0);
4713 INIT_LIST_HEAD(&wq->pwqs);
4714 INIT_LIST_HEAD(&wq->flusher_queue);
4715 INIT_LIST_HEAD(&wq->flusher_overflow);
4716 INIT_LIST_HEAD(&wq->maydays);
4717
4718 wq_init_lockdep(wq);
4719 INIT_LIST_HEAD(&wq->list);
4720
4721 if (alloc_and_link_pwqs(wq) < 0)
4722 goto err_unreg_lockdep;
4723
4724 if (wq_online && init_rescuer(wq) < 0)
4725 goto err_destroy;
4726
4727 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4728 goto err_destroy;
4729
4730 /*
4731 * wq_pool_mutex protects global freeze state and workqueues list.
4732 * Grab it, adjust max_active and add the new @wq to workqueues
4733 * list.
4734 */
4735 mutex_lock(&wq_pool_mutex);
4736
4737 mutex_lock(&wq->mutex);
4738 for_each_pwq(pwq, wq)
4739 pwq_adjust_max_active(pwq);
4740 mutex_unlock(&wq->mutex);
4741
4742 list_add_tail_rcu(&wq->list, &workqueues);
4743
4744 mutex_unlock(&wq_pool_mutex);
4745
4746 return wq;
4747
4748 err_unreg_lockdep:
4749 wq_unregister_lockdep(wq);
4750 wq_free_lockdep(wq);
4751 err_free_wq:
4752 free_workqueue_attrs(wq->unbound_attrs);
4753 kfree(wq);
4754 return NULL;
4755 err_destroy:
4756 destroy_workqueue(wq);
4757 return NULL;
4758 }
4759 EXPORT_SYMBOL_GPL(alloc_workqueue);
4760
pwq_busy(struct pool_workqueue * pwq)4761 static bool pwq_busy(struct pool_workqueue *pwq)
4762 {
4763 int i;
4764
4765 for (i = 0; i < WORK_NR_COLORS; i++)
4766 if (pwq->nr_in_flight[i])
4767 return true;
4768
4769 if ((pwq != pwq->wq->dfl_pwq) && (pwq->refcnt > 1))
4770 return true;
4771 if (pwq->nr_active || !list_empty(&pwq->inactive_works))
4772 return true;
4773
4774 return false;
4775 }
4776
4777 /**
4778 * destroy_workqueue - safely terminate a workqueue
4779 * @wq: target workqueue
4780 *
4781 * Safely destroy a workqueue. All work currently pending will be done first.
4782 */
destroy_workqueue(struct workqueue_struct * wq)4783 void destroy_workqueue(struct workqueue_struct *wq)
4784 {
4785 struct pool_workqueue *pwq;
4786 int cpu;
4787
4788 /*
4789 * Remove it from sysfs first so that sanity check failure doesn't
4790 * lead to sysfs name conflicts.
4791 */
4792 workqueue_sysfs_unregister(wq);
4793
4794 /* mark the workqueue destruction is in progress */
4795 mutex_lock(&wq->mutex);
4796 wq->flags |= __WQ_DESTROYING;
4797 mutex_unlock(&wq->mutex);
4798
4799 /* drain it before proceeding with destruction */
4800 drain_workqueue(wq);
4801
4802 /* kill rescuer, if sanity checks fail, leave it w/o rescuer */
4803 if (wq->rescuer) {
4804 struct worker *rescuer = wq->rescuer;
4805
4806 /* this prevents new queueing */
4807 raw_spin_lock_irq(&wq_mayday_lock);
4808 wq->rescuer = NULL;
4809 raw_spin_unlock_irq(&wq_mayday_lock);
4810
4811 /* rescuer will empty maydays list before exiting */
4812 kthread_stop(rescuer->task);
4813 kfree(rescuer);
4814 }
4815
4816 /*
4817 * Sanity checks - grab all the locks so that we wait for all
4818 * in-flight operations which may do put_pwq().
4819 */
4820 mutex_lock(&wq_pool_mutex);
4821 mutex_lock(&wq->mutex);
4822 for_each_pwq(pwq, wq) {
4823 raw_spin_lock_irq(&pwq->pool->lock);
4824 if (WARN_ON(pwq_busy(pwq))) {
4825 pr_warn("%s: %s has the following busy pwq\n",
4826 __func__, wq->name);
4827 show_pwq(pwq);
4828 raw_spin_unlock_irq(&pwq->pool->lock);
4829 mutex_unlock(&wq->mutex);
4830 mutex_unlock(&wq_pool_mutex);
4831 show_one_workqueue(wq);
4832 return;
4833 }
4834 raw_spin_unlock_irq(&pwq->pool->lock);
4835 }
4836 mutex_unlock(&wq->mutex);
4837
4838 /*
4839 * wq list is used to freeze wq, remove from list after
4840 * flushing is complete in case freeze races us.
4841 */
4842 list_del_rcu(&wq->list);
4843 mutex_unlock(&wq_pool_mutex);
4844
4845 /*
4846 * We're the sole accessor of @wq. Directly access cpu_pwq and dfl_pwq
4847 * to put the base refs. @wq will be auto-destroyed from the last
4848 * pwq_put. RCU read lock prevents @wq from going away from under us.
4849 */
4850 rcu_read_lock();
4851
4852 for_each_possible_cpu(cpu) {
4853 pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
4854 RCU_INIT_POINTER(*per_cpu_ptr(wq->cpu_pwq, cpu), NULL);
4855 put_pwq_unlocked(pwq);
4856 }
4857
4858 put_pwq_unlocked(wq->dfl_pwq);
4859 wq->dfl_pwq = NULL;
4860
4861 rcu_read_unlock();
4862 }
4863 EXPORT_SYMBOL_GPL(destroy_workqueue);
4864
4865 /**
4866 * workqueue_set_max_active - adjust max_active of a workqueue
4867 * @wq: target workqueue
4868 * @max_active: new max_active value.
4869 *
4870 * Set max_active of @wq to @max_active.
4871 *
4872 * CONTEXT:
4873 * Don't call from IRQ context.
4874 */
workqueue_set_max_active(struct workqueue_struct * wq,int max_active)4875 void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4876 {
4877 struct pool_workqueue *pwq;
4878
4879 /* disallow meddling with max_active for ordered workqueues */
4880 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4881 return;
4882
4883 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4884
4885 mutex_lock(&wq->mutex);
4886
4887 wq->flags &= ~__WQ_ORDERED;
4888 wq->saved_max_active = max_active;
4889
4890 for_each_pwq(pwq, wq)
4891 pwq_adjust_max_active(pwq);
4892
4893 mutex_unlock(&wq->mutex);
4894 }
4895 EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4896
4897 /**
4898 * current_work - retrieve %current task's work struct
4899 *
4900 * Determine if %current task is a workqueue worker and what it's working on.
4901 * Useful to find out the context that the %current task is running in.
4902 *
4903 * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
4904 */
current_work(void)4905 struct work_struct *current_work(void)
4906 {
4907 struct worker *worker = current_wq_worker();
4908
4909 return worker ? worker->current_work : NULL;
4910 }
4911 EXPORT_SYMBOL(current_work);
4912
4913 /**
4914 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4915 *
4916 * Determine whether %current is a workqueue rescuer. Can be used from
4917 * work functions to determine whether it's being run off the rescuer task.
4918 *
4919 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4920 */
current_is_workqueue_rescuer(void)4921 bool current_is_workqueue_rescuer(void)
4922 {
4923 struct worker *worker = current_wq_worker();
4924
4925 return worker && worker->rescue_wq;
4926 }
4927
4928 /**
4929 * workqueue_congested - test whether a workqueue is congested
4930 * @cpu: CPU in question
4931 * @wq: target workqueue
4932 *
4933 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4934 * no synchronization around this function and the test result is
4935 * unreliable and only useful as advisory hints or for debugging.
4936 *
4937 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4938 *
4939 * With the exception of ordered workqueues, all workqueues have per-cpu
4940 * pool_workqueues, each with its own congested state. A workqueue being
4941 * congested on one CPU doesn't mean that the workqueue is contested on any
4942 * other CPUs.
4943 *
4944 * Return:
4945 * %true if congested, %false otherwise.
4946 */
workqueue_congested(int cpu,struct workqueue_struct * wq)4947 bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4948 {
4949 struct pool_workqueue *pwq;
4950 bool ret;
4951
4952 rcu_read_lock();
4953 preempt_disable();
4954
4955 if (cpu == WORK_CPU_UNBOUND)
4956 cpu = smp_processor_id();
4957
4958 pwq = *per_cpu_ptr(wq->cpu_pwq, cpu);
4959 ret = !list_empty(&pwq->inactive_works);
4960
4961 preempt_enable();
4962 rcu_read_unlock();
4963
4964 return ret;
4965 }
4966 EXPORT_SYMBOL_GPL(workqueue_congested);
4967
4968 /**
4969 * work_busy - test whether a work is currently pending or running
4970 * @work: the work to be tested
4971 *
4972 * Test whether @work is currently pending or running. There is no
4973 * synchronization around this function and the test result is
4974 * unreliable and only useful as advisory hints or for debugging.
4975 *
4976 * Return:
4977 * OR'd bitmask of WORK_BUSY_* bits.
4978 */
work_busy(struct work_struct * work)4979 unsigned int work_busy(struct work_struct *work)
4980 {
4981 struct worker_pool *pool;
4982 unsigned long flags;
4983 unsigned int ret = 0;
4984
4985 if (work_pending(work))
4986 ret |= WORK_BUSY_PENDING;
4987
4988 rcu_read_lock();
4989 pool = get_work_pool(work);
4990 if (pool) {
4991 raw_spin_lock_irqsave(&pool->lock, flags);
4992 if (find_worker_executing_work(pool, work))
4993 ret |= WORK_BUSY_RUNNING;
4994 raw_spin_unlock_irqrestore(&pool->lock, flags);
4995 }
4996 rcu_read_unlock();
4997
4998 return ret;
4999 }
5000 EXPORT_SYMBOL_GPL(work_busy);
5001
5002 /**
5003 * set_worker_desc - set description for the current work item
5004 * @fmt: printf-style format string
5005 * @...: arguments for the format string
5006 *
5007 * This function can be called by a running work function to describe what
5008 * the work item is about. If the worker task gets dumped, this
5009 * information will be printed out together to help debugging. The
5010 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
5011 */
set_worker_desc(const char * fmt,...)5012 void set_worker_desc(const char *fmt, ...)
5013 {
5014 struct worker *worker = current_wq_worker();
5015 va_list args;
5016
5017 if (worker) {
5018 va_start(args, fmt);
5019 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
5020 va_end(args);
5021 }
5022 }
5023 EXPORT_SYMBOL_GPL(set_worker_desc);
5024
5025 /**
5026 * print_worker_info - print out worker information and description
5027 * @log_lvl: the log level to use when printing
5028 * @task: target task
5029 *
5030 * If @task is a worker and currently executing a work item, print out the
5031 * name of the workqueue being serviced and worker description set with
5032 * set_worker_desc() by the currently executing work item.
5033 *
5034 * This function can be safely called on any task as long as the
5035 * task_struct itself is accessible. While safe, this function isn't
5036 * synchronized and may print out mixups or garbages of limited length.
5037 */
print_worker_info(const char * log_lvl,struct task_struct * task)5038 void print_worker_info(const char *log_lvl, struct task_struct *task)
5039 {
5040 work_func_t *fn = NULL;
5041 char name[WQ_NAME_LEN] = { };
5042 char desc[WORKER_DESC_LEN] = { };
5043 struct pool_workqueue *pwq = NULL;
5044 struct workqueue_struct *wq = NULL;
5045 struct worker *worker;
5046
5047 if (!(task->flags & PF_WQ_WORKER))
5048 return;
5049
5050 /*
5051 * This function is called without any synchronization and @task
5052 * could be in any state. Be careful with dereferences.
5053 */
5054 worker = kthread_probe_data(task);
5055
5056 /*
5057 * Carefully copy the associated workqueue's workfn, name and desc.
5058 * Keep the original last '\0' in case the original is garbage.
5059 */
5060 copy_from_kernel_nofault(&fn, &worker->current_func, sizeof(fn));
5061 copy_from_kernel_nofault(&pwq, &worker->current_pwq, sizeof(pwq));
5062 copy_from_kernel_nofault(&wq, &pwq->wq, sizeof(wq));
5063 copy_from_kernel_nofault(name, wq->name, sizeof(name) - 1);
5064 copy_from_kernel_nofault(desc, worker->desc, sizeof(desc) - 1);
5065
5066 if (fn || name[0] || desc[0]) {
5067 printk("%sWorkqueue: %s %ps", log_lvl, name, fn);
5068 if (strcmp(name, desc))
5069 pr_cont(" (%s)", desc);
5070 pr_cont("\n");
5071 }
5072 }
5073
pr_cont_pool_info(struct worker_pool * pool)5074 static void pr_cont_pool_info(struct worker_pool *pool)
5075 {
5076 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
5077 if (pool->node != NUMA_NO_NODE)
5078 pr_cont(" node=%d", pool->node);
5079 pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
5080 }
5081
5082 struct pr_cont_work_struct {
5083 bool comma;
5084 work_func_t func;
5085 long ctr;
5086 };
5087
pr_cont_work_flush(bool comma,work_func_t func,struct pr_cont_work_struct * pcwsp)5088 static void pr_cont_work_flush(bool comma, work_func_t func, struct pr_cont_work_struct *pcwsp)
5089 {
5090 if (!pcwsp->ctr)
5091 goto out_record;
5092 if (func == pcwsp->func) {
5093 pcwsp->ctr++;
5094 return;
5095 }
5096 if (pcwsp->ctr == 1)
5097 pr_cont("%s %ps", pcwsp->comma ? "," : "", pcwsp->func);
5098 else
5099 pr_cont("%s %ld*%ps", pcwsp->comma ? "," : "", pcwsp->ctr, pcwsp->func);
5100 pcwsp->ctr = 0;
5101 out_record:
5102 if ((long)func == -1L)
5103 return;
5104 pcwsp->comma = comma;
5105 pcwsp->func = func;
5106 pcwsp->ctr = 1;
5107 }
5108
pr_cont_work(bool comma,struct work_struct * work,struct pr_cont_work_struct * pcwsp)5109 static void pr_cont_work(bool comma, struct work_struct *work, struct pr_cont_work_struct *pcwsp)
5110 {
5111 if (work->func == wq_barrier_func) {
5112 struct wq_barrier *barr;
5113
5114 barr = container_of(work, struct wq_barrier, work);
5115
5116 pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
5117 pr_cont("%s BAR(%d)", comma ? "," : "",
5118 task_pid_nr(barr->task));
5119 } else {
5120 if (!comma)
5121 pr_cont_work_flush(comma, (work_func_t)-1, pcwsp);
5122 pr_cont_work_flush(comma, work->func, pcwsp);
5123 }
5124 }
5125
show_pwq(struct pool_workqueue * pwq)5126 static void show_pwq(struct pool_workqueue *pwq)
5127 {
5128 struct pr_cont_work_struct pcws = { .ctr = 0, };
5129 struct worker_pool *pool = pwq->pool;
5130 struct work_struct *work;
5131 struct worker *worker;
5132 bool has_in_flight = false, has_pending = false;
5133 int bkt;
5134
5135 pr_info(" pwq %d:", pool->id);
5136 pr_cont_pool_info(pool);
5137
5138 pr_cont(" active=%d/%d refcnt=%d%s\n",
5139 pwq->nr_active, pwq->max_active, pwq->refcnt,
5140 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
5141
5142 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
5143 if (worker->current_pwq == pwq) {
5144 has_in_flight = true;
5145 break;
5146 }
5147 }
5148 if (has_in_flight) {
5149 bool comma = false;
5150
5151 pr_info(" in-flight:");
5152 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
5153 if (worker->current_pwq != pwq)
5154 continue;
5155
5156 pr_cont("%s %d%s:%ps", comma ? "," : "",
5157 task_pid_nr(worker->task),
5158 worker->rescue_wq ? "(RESCUER)" : "",
5159 worker->current_func);
5160 list_for_each_entry(work, &worker->scheduled, entry)
5161 pr_cont_work(false, work, &pcws);
5162 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5163 comma = true;
5164 }
5165 pr_cont("\n");
5166 }
5167
5168 list_for_each_entry(work, &pool->worklist, entry) {
5169 if (get_work_pwq(work) == pwq) {
5170 has_pending = true;
5171 break;
5172 }
5173 }
5174 if (has_pending) {
5175 bool comma = false;
5176
5177 pr_info(" pending:");
5178 list_for_each_entry(work, &pool->worklist, entry) {
5179 if (get_work_pwq(work) != pwq)
5180 continue;
5181
5182 pr_cont_work(comma, work, &pcws);
5183 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
5184 }
5185 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5186 pr_cont("\n");
5187 }
5188
5189 if (!list_empty(&pwq->inactive_works)) {
5190 bool comma = false;
5191
5192 pr_info(" inactive:");
5193 list_for_each_entry(work, &pwq->inactive_works, entry) {
5194 pr_cont_work(comma, work, &pcws);
5195 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
5196 }
5197 pr_cont_work_flush(comma, (work_func_t)-1L, &pcws);
5198 pr_cont("\n");
5199 }
5200 }
5201
5202 /**
5203 * show_one_workqueue - dump state of specified workqueue
5204 * @wq: workqueue whose state will be printed
5205 */
show_one_workqueue(struct workqueue_struct * wq)5206 void show_one_workqueue(struct workqueue_struct *wq)
5207 {
5208 struct pool_workqueue *pwq;
5209 bool idle = true;
5210 unsigned long flags;
5211
5212 for_each_pwq(pwq, wq) {
5213 if (pwq->nr_active || !list_empty(&pwq->inactive_works)) {
5214 idle = false;
5215 break;
5216 }
5217 }
5218 if (idle) /* Nothing to print for idle workqueue */
5219 return;
5220
5221 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
5222
5223 for_each_pwq(pwq, wq) {
5224 raw_spin_lock_irqsave(&pwq->pool->lock, flags);
5225 if (pwq->nr_active || !list_empty(&pwq->inactive_works)) {
5226 /*
5227 * Defer printing to avoid deadlocks in console
5228 * drivers that queue work while holding locks
5229 * also taken in their write paths.
5230 */
5231 printk_deferred_enter();
5232 show_pwq(pwq);
5233 printk_deferred_exit();
5234 }
5235 raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
5236 /*
5237 * We could be printing a lot from atomic context, e.g.
5238 * sysrq-t -> show_all_workqueues(). Avoid triggering
5239 * hard lockup.
5240 */
5241 touch_nmi_watchdog();
5242 }
5243
5244 }
5245
5246 /**
5247 * show_one_worker_pool - dump state of specified worker pool
5248 * @pool: worker pool whose state will be printed
5249 */
show_one_worker_pool(struct worker_pool * pool)5250 static void show_one_worker_pool(struct worker_pool *pool)
5251 {
5252 struct worker *worker;
5253 bool first = true;
5254 unsigned long flags;
5255 unsigned long hung = 0;
5256
5257 raw_spin_lock_irqsave(&pool->lock, flags);
5258 if (pool->nr_workers == pool->nr_idle)
5259 goto next_pool;
5260
5261 /* How long the first pending work is waiting for a worker. */
5262 if (!list_empty(&pool->worklist))
5263 hung = jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000;
5264
5265 /*
5266 * Defer printing to avoid deadlocks in console drivers that
5267 * queue work while holding locks also taken in their write
5268 * paths.
5269 */
5270 printk_deferred_enter();
5271 pr_info("pool %d:", pool->id);
5272 pr_cont_pool_info(pool);
5273 pr_cont(" hung=%lus workers=%d", hung, pool->nr_workers);
5274 if (pool->manager)
5275 pr_cont(" manager: %d",
5276 task_pid_nr(pool->manager->task));
5277 list_for_each_entry(worker, &pool->idle_list, entry) {
5278 pr_cont(" %s%d", first ? "idle: " : "",
5279 task_pid_nr(worker->task));
5280 first = false;
5281 }
5282 pr_cont("\n");
5283 printk_deferred_exit();
5284 next_pool:
5285 raw_spin_unlock_irqrestore(&pool->lock, flags);
5286 /*
5287 * We could be printing a lot from atomic context, e.g.
5288 * sysrq-t -> show_all_workqueues(). Avoid triggering
5289 * hard lockup.
5290 */
5291 touch_nmi_watchdog();
5292
5293 }
5294
5295 /**
5296 * show_all_workqueues - dump workqueue state
5297 *
5298 * Called from a sysrq handler and prints out all busy workqueues and pools.
5299 */
show_all_workqueues(void)5300 void show_all_workqueues(void)
5301 {
5302 struct workqueue_struct *wq;
5303 struct worker_pool *pool;
5304 int pi;
5305
5306 rcu_read_lock();
5307
5308 pr_info("Showing busy workqueues and worker pools:\n");
5309
5310 list_for_each_entry_rcu(wq, &workqueues, list)
5311 show_one_workqueue(wq);
5312
5313 for_each_pool(pool, pi)
5314 show_one_worker_pool(pool);
5315
5316 rcu_read_unlock();
5317 }
5318
5319 /**
5320 * show_freezable_workqueues - dump freezable workqueue state
5321 *
5322 * Called from try_to_freeze_tasks() and prints out all freezable workqueues
5323 * still busy.
5324 */
show_freezable_workqueues(void)5325 void show_freezable_workqueues(void)
5326 {
5327 struct workqueue_struct *wq;
5328
5329 rcu_read_lock();
5330
5331 pr_info("Showing freezable workqueues that are still busy:\n");
5332
5333 list_for_each_entry_rcu(wq, &workqueues, list) {
5334 if (!(wq->flags & WQ_FREEZABLE))
5335 continue;
5336 show_one_workqueue(wq);
5337 }
5338
5339 rcu_read_unlock();
5340 }
5341
5342 /* used to show worker information through /proc/PID/{comm,stat,status} */
wq_worker_comm(char * buf,size_t size,struct task_struct * task)5343 void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
5344 {
5345 int off;
5346
5347 /* always show the actual comm */
5348 off = strscpy(buf, task->comm, size);
5349 if (off < 0)
5350 return;
5351
5352 /* stabilize PF_WQ_WORKER and worker pool association */
5353 mutex_lock(&wq_pool_attach_mutex);
5354
5355 if (task->flags & PF_WQ_WORKER) {
5356 struct worker *worker = kthread_data(task);
5357 struct worker_pool *pool = worker->pool;
5358
5359 if (pool) {
5360 raw_spin_lock_irq(&pool->lock);
5361 /*
5362 * ->desc tracks information (wq name or
5363 * set_worker_desc()) for the latest execution. If
5364 * current, prepend '+', otherwise '-'.
5365 */
5366 if (worker->desc[0] != '\0') {
5367 if (worker->current_work)
5368 scnprintf(buf + off, size - off, "+%s",
5369 worker->desc);
5370 else
5371 scnprintf(buf + off, size - off, "-%s",
5372 worker->desc);
5373 }
5374 raw_spin_unlock_irq(&pool->lock);
5375 }
5376 }
5377
5378 mutex_unlock(&wq_pool_attach_mutex);
5379 }
5380
5381 #ifdef CONFIG_SMP
5382
5383 /*
5384 * CPU hotplug.
5385 *
5386 * There are two challenges in supporting CPU hotplug. Firstly, there
5387 * are a lot of assumptions on strong associations among work, pwq and
5388 * pool which make migrating pending and scheduled works very
5389 * difficult to implement without impacting hot paths. Secondly,
5390 * worker pools serve mix of short, long and very long running works making
5391 * blocked draining impractical.
5392 *
5393 * This is solved by allowing the pools to be disassociated from the CPU
5394 * running as an unbound one and allowing it to be reattached later if the
5395 * cpu comes back online.
5396 */
5397
unbind_workers(int cpu)5398 static void unbind_workers(int cpu)
5399 {
5400 struct worker_pool *pool;
5401 struct worker *worker;
5402
5403 for_each_cpu_worker_pool(pool, cpu) {
5404 mutex_lock(&wq_pool_attach_mutex);
5405 raw_spin_lock_irq(&pool->lock);
5406
5407 /*
5408 * We've blocked all attach/detach operations. Make all workers
5409 * unbound and set DISASSOCIATED. Before this, all workers
5410 * must be on the cpu. After this, they may become diasporas.
5411 * And the preemption disabled section in their sched callbacks
5412 * are guaranteed to see WORKER_UNBOUND since the code here
5413 * is on the same cpu.
5414 */
5415 for_each_pool_worker(worker, pool)
5416 worker->flags |= WORKER_UNBOUND;
5417
5418 pool->flags |= POOL_DISASSOCIATED;
5419
5420 /*
5421 * The handling of nr_running in sched callbacks are disabled
5422 * now. Zap nr_running. After this, nr_running stays zero and
5423 * need_more_worker() and keep_working() are always true as
5424 * long as the worklist is not empty. This pool now behaves as
5425 * an unbound (in terms of concurrency management) pool which
5426 * are served by workers tied to the pool.
5427 */
5428 pool->nr_running = 0;
5429
5430 /*
5431 * With concurrency management just turned off, a busy
5432 * worker blocking could lead to lengthy stalls. Kick off
5433 * unbound chain execution of currently pending work items.
5434 */
5435 kick_pool(pool);
5436
5437 raw_spin_unlock_irq(&pool->lock);
5438
5439 for_each_pool_worker(worker, pool)
5440 unbind_worker(worker);
5441
5442 mutex_unlock(&wq_pool_attach_mutex);
5443 }
5444 }
5445
5446 /**
5447 * rebind_workers - rebind all workers of a pool to the associated CPU
5448 * @pool: pool of interest
5449 *
5450 * @pool->cpu is coming online. Rebind all workers to the CPU.
5451 */
rebind_workers(struct worker_pool * pool)5452 static void rebind_workers(struct worker_pool *pool)
5453 {
5454 struct worker *worker;
5455
5456 lockdep_assert_held(&wq_pool_attach_mutex);
5457
5458 /*
5459 * Restore CPU affinity of all workers. As all idle workers should
5460 * be on the run-queue of the associated CPU before any local
5461 * wake-ups for concurrency management happen, restore CPU affinity
5462 * of all workers first and then clear UNBOUND. As we're called
5463 * from CPU_ONLINE, the following shouldn't fail.
5464 */
5465 for_each_pool_worker(worker, pool) {
5466 kthread_set_per_cpu(worker->task, pool->cpu);
5467 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
5468 pool_allowed_cpus(pool)) < 0);
5469 }
5470
5471 raw_spin_lock_irq(&pool->lock);
5472
5473 pool->flags &= ~POOL_DISASSOCIATED;
5474
5475 for_each_pool_worker(worker, pool) {
5476 unsigned int worker_flags = worker->flags;
5477
5478 /*
5479 * We want to clear UNBOUND but can't directly call
5480 * worker_clr_flags() or adjust nr_running. Atomically
5481 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
5482 * @worker will clear REBOUND using worker_clr_flags() when
5483 * it initiates the next execution cycle thus restoring
5484 * concurrency management. Note that when or whether
5485 * @worker clears REBOUND doesn't affect correctness.
5486 *
5487 * WRITE_ONCE() is necessary because @worker->flags may be
5488 * tested without holding any lock in
5489 * wq_worker_running(). Without it, NOT_RUNNING test may
5490 * fail incorrectly leading to premature concurrency
5491 * management operations.
5492 */
5493 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
5494 worker_flags |= WORKER_REBOUND;
5495 worker_flags &= ~WORKER_UNBOUND;
5496 WRITE_ONCE(worker->flags, worker_flags);
5497 }
5498
5499 raw_spin_unlock_irq(&pool->lock);
5500 }
5501
5502 /**
5503 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
5504 * @pool: unbound pool of interest
5505 * @cpu: the CPU which is coming up
5506 *
5507 * An unbound pool may end up with a cpumask which doesn't have any online
5508 * CPUs. When a worker of such pool get scheduled, the scheduler resets
5509 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
5510 * online CPU before, cpus_allowed of all its workers should be restored.
5511 */
restore_unbound_workers_cpumask(struct worker_pool * pool,int cpu)5512 static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
5513 {
5514 static cpumask_t cpumask;
5515 struct worker *worker;
5516
5517 lockdep_assert_held(&wq_pool_attach_mutex);
5518
5519 /* is @cpu allowed for @pool? */
5520 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
5521 return;
5522
5523 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
5524
5525 /* as we're called from CPU_ONLINE, the following shouldn't fail */
5526 for_each_pool_worker(worker, pool)
5527 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
5528 }
5529
workqueue_prepare_cpu(unsigned int cpu)5530 int workqueue_prepare_cpu(unsigned int cpu)
5531 {
5532 struct worker_pool *pool;
5533
5534 for_each_cpu_worker_pool(pool, cpu) {
5535 if (pool->nr_workers)
5536 continue;
5537 if (!create_worker(pool))
5538 return -ENOMEM;
5539 }
5540 return 0;
5541 }
5542
workqueue_online_cpu(unsigned int cpu)5543 int workqueue_online_cpu(unsigned int cpu)
5544 {
5545 struct worker_pool *pool;
5546 struct workqueue_struct *wq;
5547 int pi;
5548
5549 mutex_lock(&wq_pool_mutex);
5550
5551 for_each_pool(pool, pi) {
5552 mutex_lock(&wq_pool_attach_mutex);
5553
5554 if (pool->cpu == cpu)
5555 rebind_workers(pool);
5556 else if (pool->cpu < 0)
5557 restore_unbound_workers_cpumask(pool, cpu);
5558
5559 mutex_unlock(&wq_pool_attach_mutex);
5560 }
5561
5562 /* update pod affinity of unbound workqueues */
5563 list_for_each_entry(wq, &workqueues, list) {
5564 struct workqueue_attrs *attrs = wq->unbound_attrs;
5565
5566 if (attrs) {
5567 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
5568 int tcpu;
5569
5570 for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
5571 wq_update_pod(wq, tcpu, cpu, true);
5572 }
5573 }
5574
5575 mutex_unlock(&wq_pool_mutex);
5576 return 0;
5577 }
5578
workqueue_offline_cpu(unsigned int cpu)5579 int workqueue_offline_cpu(unsigned int cpu)
5580 {
5581 struct workqueue_struct *wq;
5582
5583 /* unbinding per-cpu workers should happen on the local CPU */
5584 if (WARN_ON(cpu != smp_processor_id()))
5585 return -1;
5586
5587 unbind_workers(cpu);
5588
5589 /* update pod affinity of unbound workqueues */
5590 mutex_lock(&wq_pool_mutex);
5591 list_for_each_entry(wq, &workqueues, list) {
5592 struct workqueue_attrs *attrs = wq->unbound_attrs;
5593
5594 if (attrs) {
5595 const struct wq_pod_type *pt = wqattrs_pod_type(attrs);
5596 int tcpu;
5597
5598 for_each_cpu(tcpu, pt->pod_cpus[pt->cpu_pod[cpu]])
5599 wq_update_pod(wq, tcpu, cpu, false);
5600 }
5601 }
5602 mutex_unlock(&wq_pool_mutex);
5603
5604 return 0;
5605 }
5606
5607 struct work_for_cpu {
5608 struct work_struct work;
5609 long (*fn)(void *);
5610 void *arg;
5611 long ret;
5612 };
5613
work_for_cpu_fn(struct work_struct * work)5614 static void work_for_cpu_fn(struct work_struct *work)
5615 {
5616 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
5617
5618 wfc->ret = wfc->fn(wfc->arg);
5619 }
5620
5621 /**
5622 * work_on_cpu_key - run a function in thread context on a particular cpu
5623 * @cpu: the cpu to run on
5624 * @fn: the function to run
5625 * @arg: the function arg
5626 * @key: The lock class key for lock debugging purposes
5627 *
5628 * It is up to the caller to ensure that the cpu doesn't go offline.
5629 * The caller must not hold any locks which would prevent @fn from completing.
5630 *
5631 * Return: The value @fn returns.
5632 */
work_on_cpu_key(int cpu,long (* fn)(void *),void * arg,struct lock_class_key * key)5633 long work_on_cpu_key(int cpu, long (*fn)(void *),
5634 void *arg, struct lock_class_key *key)
5635 {
5636 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
5637
5638 INIT_WORK_ONSTACK_KEY(&wfc.work, work_for_cpu_fn, key);
5639 schedule_work_on(cpu, &wfc.work);
5640 flush_work(&wfc.work);
5641 destroy_work_on_stack(&wfc.work);
5642 return wfc.ret;
5643 }
5644 EXPORT_SYMBOL_GPL(work_on_cpu_key);
5645
5646 /**
5647 * work_on_cpu_safe_key - run a function in thread context on a particular cpu
5648 * @cpu: the cpu to run on
5649 * @fn: the function to run
5650 * @arg: the function argument
5651 * @key: The lock class key for lock debugging purposes
5652 *
5653 * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
5654 * any locks which would prevent @fn from completing.
5655 *
5656 * Return: The value @fn returns.
5657 */
work_on_cpu_safe_key(int cpu,long (* fn)(void *),void * arg,struct lock_class_key * key)5658 long work_on_cpu_safe_key(int cpu, long (*fn)(void *),
5659 void *arg, struct lock_class_key *key)
5660 {
5661 long ret = -ENODEV;
5662
5663 cpus_read_lock();
5664 if (cpu_online(cpu))
5665 ret = work_on_cpu_key(cpu, fn, arg, key);
5666 cpus_read_unlock();
5667 return ret;
5668 }
5669 EXPORT_SYMBOL_GPL(work_on_cpu_safe_key);
5670 #endif /* CONFIG_SMP */
5671
5672 #ifdef CONFIG_FREEZER
5673
5674 /**
5675 * freeze_workqueues_begin - begin freezing workqueues
5676 *
5677 * Start freezing workqueues. After this function returns, all freezable
5678 * workqueues will queue new works to their inactive_works list instead of
5679 * pool->worklist.
5680 *
5681 * CONTEXT:
5682 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5683 */
freeze_workqueues_begin(void)5684 void freeze_workqueues_begin(void)
5685 {
5686 struct workqueue_struct *wq;
5687 struct pool_workqueue *pwq;
5688
5689 mutex_lock(&wq_pool_mutex);
5690
5691 WARN_ON_ONCE(workqueue_freezing);
5692 workqueue_freezing = true;
5693
5694 list_for_each_entry(wq, &workqueues, list) {
5695 mutex_lock(&wq->mutex);
5696 for_each_pwq(pwq, wq)
5697 pwq_adjust_max_active(pwq);
5698 mutex_unlock(&wq->mutex);
5699 }
5700
5701 mutex_unlock(&wq_pool_mutex);
5702 }
5703
5704 /**
5705 * freeze_workqueues_busy - are freezable workqueues still busy?
5706 *
5707 * Check whether freezing is complete. This function must be called
5708 * between freeze_workqueues_begin() and thaw_workqueues().
5709 *
5710 * CONTEXT:
5711 * Grabs and releases wq_pool_mutex.
5712 *
5713 * Return:
5714 * %true if some freezable workqueues are still busy. %false if freezing
5715 * is complete.
5716 */
freeze_workqueues_busy(void)5717 bool freeze_workqueues_busy(void)
5718 {
5719 bool busy = false;
5720 struct workqueue_struct *wq;
5721 struct pool_workqueue *pwq;
5722
5723 mutex_lock(&wq_pool_mutex);
5724
5725 WARN_ON_ONCE(!workqueue_freezing);
5726
5727 list_for_each_entry(wq, &workqueues, list) {
5728 if (!(wq->flags & WQ_FREEZABLE))
5729 continue;
5730 /*
5731 * nr_active is monotonically decreasing. It's safe
5732 * to peek without lock.
5733 */
5734 rcu_read_lock();
5735 for_each_pwq(pwq, wq) {
5736 WARN_ON_ONCE(pwq->nr_active < 0);
5737 if (pwq->nr_active) {
5738 busy = true;
5739 rcu_read_unlock();
5740 goto out_unlock;
5741 }
5742 }
5743 rcu_read_unlock();
5744 }
5745 out_unlock:
5746 mutex_unlock(&wq_pool_mutex);
5747 return busy;
5748 }
5749
5750 /**
5751 * thaw_workqueues - thaw workqueues
5752 *
5753 * Thaw workqueues. Normal queueing is restored and all collected
5754 * frozen works are transferred to their respective pool worklists.
5755 *
5756 * CONTEXT:
5757 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
5758 */
thaw_workqueues(void)5759 void thaw_workqueues(void)
5760 {
5761 struct workqueue_struct *wq;
5762 struct pool_workqueue *pwq;
5763
5764 mutex_lock(&wq_pool_mutex);
5765
5766 if (!workqueue_freezing)
5767 goto out_unlock;
5768
5769 workqueue_freezing = false;
5770
5771 /* restore max_active and repopulate worklist */
5772 list_for_each_entry(wq, &workqueues, list) {
5773 mutex_lock(&wq->mutex);
5774 for_each_pwq(pwq, wq)
5775 pwq_adjust_max_active(pwq);
5776 mutex_unlock(&wq->mutex);
5777 }
5778
5779 out_unlock:
5780 mutex_unlock(&wq_pool_mutex);
5781 }
5782 #endif /* CONFIG_FREEZER */
5783
workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)5784 static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)
5785 {
5786 LIST_HEAD(ctxs);
5787 int ret = 0;
5788 struct workqueue_struct *wq;
5789 struct apply_wqattrs_ctx *ctx, *n;
5790
5791 lockdep_assert_held(&wq_pool_mutex);
5792
5793 list_for_each_entry(wq, &workqueues, list) {
5794 if (!(wq->flags & WQ_UNBOUND))
5795 continue;
5796 /* creating multiple pwqs breaks ordering guarantee */
5797 if (wq->flags & __WQ_ORDERED)
5798 continue;
5799
5800 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs, unbound_cpumask);
5801 if (IS_ERR(ctx)) {
5802 ret = PTR_ERR(ctx);
5803 break;
5804 }
5805
5806 list_add_tail(&ctx->list, &ctxs);
5807 }
5808
5809 list_for_each_entry_safe(ctx, n, &ctxs, list) {
5810 if (!ret)
5811 apply_wqattrs_commit(ctx);
5812 apply_wqattrs_cleanup(ctx);
5813 }
5814
5815 if (!ret) {
5816 mutex_lock(&wq_pool_attach_mutex);
5817 cpumask_copy(wq_unbound_cpumask, unbound_cpumask);
5818 mutex_unlock(&wq_pool_attach_mutex);
5819 }
5820 return ret;
5821 }
5822
5823 /**
5824 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
5825 * @cpumask: the cpumask to set
5826 *
5827 * The low-level workqueues cpumask is a global cpumask that limits
5828 * the affinity of all unbound workqueues. This function check the @cpumask
5829 * and apply it to all unbound workqueues and updates all pwqs of them.
5830 *
5831 * Return: 0 - Success
5832 * -EINVAL - Invalid @cpumask
5833 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
5834 */
workqueue_set_unbound_cpumask(cpumask_var_t cpumask)5835 int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
5836 {
5837 int ret = -EINVAL;
5838
5839 /*
5840 * Not excluding isolated cpus on purpose.
5841 * If the user wishes to include them, we allow that.
5842 */
5843 cpumask_and(cpumask, cpumask, cpu_possible_mask);
5844 if (!cpumask_empty(cpumask)) {
5845 apply_wqattrs_lock();
5846 if (cpumask_equal(cpumask, wq_unbound_cpumask)) {
5847 ret = 0;
5848 goto out_unlock;
5849 }
5850
5851 ret = workqueue_apply_unbound_cpumask(cpumask);
5852
5853 out_unlock:
5854 apply_wqattrs_unlock();
5855 }
5856
5857 return ret;
5858 }
5859
parse_affn_scope(const char * val)5860 static int parse_affn_scope(const char *val)
5861 {
5862 int i;
5863
5864 for (i = 0; i < ARRAY_SIZE(wq_affn_names); i++) {
5865 if (!strncasecmp(val, wq_affn_names[i], strlen(wq_affn_names[i])))
5866 return i;
5867 }
5868 return -EINVAL;
5869 }
5870
wq_affn_dfl_set(const char * val,const struct kernel_param * kp)5871 static int wq_affn_dfl_set(const char *val, const struct kernel_param *kp)
5872 {
5873 struct workqueue_struct *wq;
5874 int affn, cpu;
5875
5876 affn = parse_affn_scope(val);
5877 if (affn < 0)
5878 return affn;
5879 if (affn == WQ_AFFN_DFL)
5880 return -EINVAL;
5881
5882 cpus_read_lock();
5883 mutex_lock(&wq_pool_mutex);
5884
5885 wq_affn_dfl = affn;
5886
5887 list_for_each_entry(wq, &workqueues, list) {
5888 for_each_online_cpu(cpu) {
5889 wq_update_pod(wq, cpu, cpu, true);
5890 }
5891 }
5892
5893 mutex_unlock(&wq_pool_mutex);
5894 cpus_read_unlock();
5895
5896 return 0;
5897 }
5898
wq_affn_dfl_get(char * buffer,const struct kernel_param * kp)5899 static int wq_affn_dfl_get(char *buffer, const struct kernel_param *kp)
5900 {
5901 return scnprintf(buffer, PAGE_SIZE, "%s\n", wq_affn_names[wq_affn_dfl]);
5902 }
5903
5904 static const struct kernel_param_ops wq_affn_dfl_ops = {
5905 .set = wq_affn_dfl_set,
5906 .get = wq_affn_dfl_get,
5907 };
5908
5909 module_param_cb(default_affinity_scope, &wq_affn_dfl_ops, NULL, 0644);
5910
5911 #ifdef CONFIG_SYSFS
5912 /*
5913 * Workqueues with WQ_SYSFS flag set is visible to userland via
5914 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
5915 * following attributes.
5916 *
5917 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
5918 * max_active RW int : maximum number of in-flight work items
5919 *
5920 * Unbound workqueues have the following extra attributes.
5921 *
5922 * nice RW int : nice value of the workers
5923 * cpumask RW mask : bitmask of allowed CPUs for the workers
5924 * affinity_scope RW str : worker CPU affinity scope (cache, numa, none)
5925 * affinity_strict RW bool : worker CPU affinity is strict
5926 */
5927 struct wq_device {
5928 struct workqueue_struct *wq;
5929 struct device dev;
5930 };
5931
dev_to_wq(struct device * dev)5932 static struct workqueue_struct *dev_to_wq(struct device *dev)
5933 {
5934 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5935
5936 return wq_dev->wq;
5937 }
5938
per_cpu_show(struct device * dev,struct device_attribute * attr,char * buf)5939 static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
5940 char *buf)
5941 {
5942 struct workqueue_struct *wq = dev_to_wq(dev);
5943
5944 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
5945 }
5946 static DEVICE_ATTR_RO(per_cpu);
5947
max_active_show(struct device * dev,struct device_attribute * attr,char * buf)5948 static ssize_t max_active_show(struct device *dev,
5949 struct device_attribute *attr, char *buf)
5950 {
5951 struct workqueue_struct *wq = dev_to_wq(dev);
5952
5953 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
5954 }
5955
max_active_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)5956 static ssize_t max_active_store(struct device *dev,
5957 struct device_attribute *attr, const char *buf,
5958 size_t count)
5959 {
5960 struct workqueue_struct *wq = dev_to_wq(dev);
5961 int val;
5962
5963 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
5964 return -EINVAL;
5965
5966 workqueue_set_max_active(wq, val);
5967 return count;
5968 }
5969 static DEVICE_ATTR_RW(max_active);
5970
5971 static struct attribute *wq_sysfs_attrs[] = {
5972 &dev_attr_per_cpu.attr,
5973 &dev_attr_max_active.attr,
5974 NULL,
5975 };
5976 ATTRIBUTE_GROUPS(wq_sysfs);
5977
wq_nice_show(struct device * dev,struct device_attribute * attr,char * buf)5978 static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5979 char *buf)
5980 {
5981 struct workqueue_struct *wq = dev_to_wq(dev);
5982 int written;
5983
5984 mutex_lock(&wq->mutex);
5985 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5986 mutex_unlock(&wq->mutex);
5987
5988 return written;
5989 }
5990
5991 /* prepare workqueue_attrs for sysfs store operations */
wq_sysfs_prep_attrs(struct workqueue_struct * wq)5992 static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
5993 {
5994 struct workqueue_attrs *attrs;
5995
5996 lockdep_assert_held(&wq_pool_mutex);
5997
5998 attrs = alloc_workqueue_attrs();
5999 if (!attrs)
6000 return NULL;
6001
6002 copy_workqueue_attrs(attrs, wq->unbound_attrs);
6003 return attrs;
6004 }
6005
wq_nice_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)6006 static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
6007 const char *buf, size_t count)
6008 {
6009 struct workqueue_struct *wq = dev_to_wq(dev);
6010 struct workqueue_attrs *attrs;
6011 int ret = -ENOMEM;
6012
6013 apply_wqattrs_lock();
6014
6015 attrs = wq_sysfs_prep_attrs(wq);
6016 if (!attrs)
6017 goto out_unlock;
6018
6019 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
6020 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
6021 ret = apply_workqueue_attrs_locked(wq, attrs);
6022 else
6023 ret = -EINVAL;
6024
6025 out_unlock:
6026 apply_wqattrs_unlock();
6027 free_workqueue_attrs(attrs);
6028 return ret ?: count;
6029 }
6030
wq_cpumask_show(struct device * dev,struct device_attribute * attr,char * buf)6031 static ssize_t wq_cpumask_show(struct device *dev,
6032 struct device_attribute *attr, char *buf)
6033 {
6034 struct workqueue_struct *wq = dev_to_wq(dev);
6035 int written;
6036
6037 mutex_lock(&wq->mutex);
6038 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
6039 cpumask_pr_args(wq->unbound_attrs->cpumask));
6040 mutex_unlock(&wq->mutex);
6041 return written;
6042 }
6043
wq_cpumask_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)6044 static ssize_t wq_cpumask_store(struct device *dev,
6045 struct device_attribute *attr,
6046 const char *buf, size_t count)
6047 {
6048 struct workqueue_struct *wq = dev_to_wq(dev);
6049 struct workqueue_attrs *attrs;
6050 int ret = -ENOMEM;
6051
6052 apply_wqattrs_lock();
6053
6054 attrs = wq_sysfs_prep_attrs(wq);
6055 if (!attrs)
6056 goto out_unlock;
6057
6058 ret = cpumask_parse(buf, attrs->cpumask);
6059 if (!ret)
6060 ret = apply_workqueue_attrs_locked(wq, attrs);
6061
6062 out_unlock:
6063 apply_wqattrs_unlock();
6064 free_workqueue_attrs(attrs);
6065 return ret ?: count;
6066 }
6067
wq_affn_scope_show(struct device * dev,struct device_attribute * attr,char * buf)6068 static ssize_t wq_affn_scope_show(struct device *dev,
6069 struct device_attribute *attr, char *buf)
6070 {
6071 struct workqueue_struct *wq = dev_to_wq(dev);
6072 int written;
6073
6074 mutex_lock(&wq->mutex);
6075 if (wq->unbound_attrs->affn_scope == WQ_AFFN_DFL)
6076 written = scnprintf(buf, PAGE_SIZE, "%s (%s)\n",
6077 wq_affn_names[WQ_AFFN_DFL],
6078 wq_affn_names[wq_affn_dfl]);
6079 else
6080 written = scnprintf(buf, PAGE_SIZE, "%s\n",
6081 wq_affn_names[wq->unbound_attrs->affn_scope]);
6082 mutex_unlock(&wq->mutex);
6083
6084 return written;
6085 }
6086
wq_affn_scope_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)6087 static ssize_t wq_affn_scope_store(struct device *dev,
6088 struct device_attribute *attr,
6089 const char *buf, size_t count)
6090 {
6091 struct workqueue_struct *wq = dev_to_wq(dev);
6092 struct workqueue_attrs *attrs;
6093 int affn, ret = -ENOMEM;
6094
6095 affn = parse_affn_scope(buf);
6096 if (affn < 0)
6097 return affn;
6098
6099 apply_wqattrs_lock();
6100 attrs = wq_sysfs_prep_attrs(wq);
6101 if (attrs) {
6102 attrs->affn_scope = affn;
6103 ret = apply_workqueue_attrs_locked(wq, attrs);
6104 }
6105 apply_wqattrs_unlock();
6106 free_workqueue_attrs(attrs);
6107 return ret ?: count;
6108 }
6109
wq_affinity_strict_show(struct device * dev,struct device_attribute * attr,char * buf)6110 static ssize_t wq_affinity_strict_show(struct device *dev,
6111 struct device_attribute *attr, char *buf)
6112 {
6113 struct workqueue_struct *wq = dev_to_wq(dev);
6114
6115 return scnprintf(buf, PAGE_SIZE, "%d\n",
6116 wq->unbound_attrs->affn_strict);
6117 }
6118
wq_affinity_strict_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)6119 static ssize_t wq_affinity_strict_store(struct device *dev,
6120 struct device_attribute *attr,
6121 const char *buf, size_t count)
6122 {
6123 struct workqueue_struct *wq = dev_to_wq(dev);
6124 struct workqueue_attrs *attrs;
6125 int v, ret = -ENOMEM;
6126
6127 if (sscanf(buf, "%d", &v) != 1)
6128 return -EINVAL;
6129
6130 apply_wqattrs_lock();
6131 attrs = wq_sysfs_prep_attrs(wq);
6132 if (attrs) {
6133 attrs->affn_strict = (bool)v;
6134 ret = apply_workqueue_attrs_locked(wq, attrs);
6135 }
6136 apply_wqattrs_unlock();
6137 free_workqueue_attrs(attrs);
6138 return ret ?: count;
6139 }
6140
6141 static struct device_attribute wq_sysfs_unbound_attrs[] = {
6142 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
6143 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
6144 __ATTR(affinity_scope, 0644, wq_affn_scope_show, wq_affn_scope_store),
6145 __ATTR(affinity_strict, 0644, wq_affinity_strict_show, wq_affinity_strict_store),
6146 __ATTR_NULL,
6147 };
6148
6149 static struct bus_type wq_subsys = {
6150 .name = "workqueue",
6151 .dev_groups = wq_sysfs_groups,
6152 };
6153
wq_unbound_cpumask_show(struct device * dev,struct device_attribute * attr,char * buf)6154 static ssize_t wq_unbound_cpumask_show(struct device *dev,
6155 struct device_attribute *attr, char *buf)
6156 {
6157 int written;
6158
6159 mutex_lock(&wq_pool_mutex);
6160 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
6161 cpumask_pr_args(wq_unbound_cpumask));
6162 mutex_unlock(&wq_pool_mutex);
6163
6164 return written;
6165 }
6166
wq_unbound_cpumask_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)6167 static ssize_t wq_unbound_cpumask_store(struct device *dev,
6168 struct device_attribute *attr, const char *buf, size_t count)
6169 {
6170 cpumask_var_t cpumask;
6171 int ret;
6172
6173 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
6174 return -ENOMEM;
6175
6176 ret = cpumask_parse(buf, cpumask);
6177 if (!ret)
6178 ret = workqueue_set_unbound_cpumask(cpumask);
6179
6180 free_cpumask_var(cpumask);
6181 return ret ? ret : count;
6182 }
6183
6184 static struct device_attribute wq_sysfs_cpumask_attr =
6185 __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
6186 wq_unbound_cpumask_store);
6187
wq_sysfs_init(void)6188 static int __init wq_sysfs_init(void)
6189 {
6190 struct device *dev_root;
6191 int err;
6192
6193 err = subsys_virtual_register(&wq_subsys, NULL);
6194 if (err)
6195 return err;
6196
6197 dev_root = bus_get_dev_root(&wq_subsys);
6198 if (dev_root) {
6199 err = device_create_file(dev_root, &wq_sysfs_cpumask_attr);
6200 put_device(dev_root);
6201 }
6202 return err;
6203 }
6204 core_initcall(wq_sysfs_init);
6205
wq_device_release(struct device * dev)6206 static void wq_device_release(struct device *dev)
6207 {
6208 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
6209
6210 kfree(wq_dev);
6211 }
6212
6213 /**
6214 * workqueue_sysfs_register - make a workqueue visible in sysfs
6215 * @wq: the workqueue to register
6216 *
6217 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
6218 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
6219 * which is the preferred method.
6220 *
6221 * Workqueue user should use this function directly iff it wants to apply
6222 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
6223 * apply_workqueue_attrs() may race against userland updating the
6224 * attributes.
6225 *
6226 * Return: 0 on success, -errno on failure.
6227 */
workqueue_sysfs_register(struct workqueue_struct * wq)6228 int workqueue_sysfs_register(struct workqueue_struct *wq)
6229 {
6230 struct wq_device *wq_dev;
6231 int ret;
6232
6233 /*
6234 * Adjusting max_active or creating new pwqs by applying
6235 * attributes breaks ordering guarantee. Disallow exposing ordered
6236 * workqueues.
6237 */
6238 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
6239 return -EINVAL;
6240
6241 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
6242 if (!wq_dev)
6243 return -ENOMEM;
6244
6245 wq_dev->wq = wq;
6246 wq_dev->dev.bus = &wq_subsys;
6247 wq_dev->dev.release = wq_device_release;
6248 dev_set_name(&wq_dev->dev, "%s", wq->name);
6249
6250 /*
6251 * unbound_attrs are created separately. Suppress uevent until
6252 * everything is ready.
6253 */
6254 dev_set_uevent_suppress(&wq_dev->dev, true);
6255
6256 ret = device_register(&wq_dev->dev);
6257 if (ret) {
6258 put_device(&wq_dev->dev);
6259 wq->wq_dev = NULL;
6260 return ret;
6261 }
6262
6263 if (wq->flags & WQ_UNBOUND) {
6264 struct device_attribute *attr;
6265
6266 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
6267 ret = device_create_file(&wq_dev->dev, attr);
6268 if (ret) {
6269 device_unregister(&wq_dev->dev);
6270 wq->wq_dev = NULL;
6271 return ret;
6272 }
6273 }
6274 }
6275
6276 dev_set_uevent_suppress(&wq_dev->dev, false);
6277 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
6278 return 0;
6279 }
6280
6281 /**
6282 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
6283 * @wq: the workqueue to unregister
6284 *
6285 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
6286 */
workqueue_sysfs_unregister(struct workqueue_struct * wq)6287 static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
6288 {
6289 struct wq_device *wq_dev = wq->wq_dev;
6290
6291 if (!wq->wq_dev)
6292 return;
6293
6294 wq->wq_dev = NULL;
6295 device_unregister(&wq_dev->dev);
6296 }
6297 #else /* CONFIG_SYSFS */
workqueue_sysfs_unregister(struct workqueue_struct * wq)6298 static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
6299 #endif /* CONFIG_SYSFS */
6300
6301 /*
6302 * Workqueue watchdog.
6303 *
6304 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
6305 * flush dependency, a concurrency managed work item which stays RUNNING
6306 * indefinitely. Workqueue stalls can be very difficult to debug as the
6307 * usual warning mechanisms don't trigger and internal workqueue state is
6308 * largely opaque.
6309 *
6310 * Workqueue watchdog monitors all worker pools periodically and dumps
6311 * state if some pools failed to make forward progress for a while where
6312 * forward progress is defined as the first item on ->worklist changing.
6313 *
6314 * This mechanism is controlled through the kernel parameter
6315 * "workqueue.watchdog_thresh" which can be updated at runtime through the
6316 * corresponding sysfs parameter file.
6317 */
6318 #ifdef CONFIG_WQ_WATCHDOG
6319
6320 static unsigned long wq_watchdog_thresh = 30;
6321 static struct timer_list wq_watchdog_timer;
6322
6323 static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
6324 static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
6325
6326 /*
6327 * Show workers that might prevent the processing of pending work items.
6328 * The only candidates are CPU-bound workers in the running state.
6329 * Pending work items should be handled by another idle worker
6330 * in all other situations.
6331 */
show_cpu_pool_hog(struct worker_pool * pool)6332 static void show_cpu_pool_hog(struct worker_pool *pool)
6333 {
6334 struct worker *worker;
6335 unsigned long flags;
6336 int bkt;
6337
6338 raw_spin_lock_irqsave(&pool->lock, flags);
6339
6340 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
6341 if (task_is_running(worker->task)) {
6342 /*
6343 * Defer printing to avoid deadlocks in console
6344 * drivers that queue work while holding locks
6345 * also taken in their write paths.
6346 */
6347 printk_deferred_enter();
6348
6349 pr_info("pool %d:\n", pool->id);
6350 sched_show_task(worker->task);
6351
6352 printk_deferred_exit();
6353 }
6354 }
6355
6356 raw_spin_unlock_irqrestore(&pool->lock, flags);
6357 }
6358
show_cpu_pools_hogs(void)6359 static void show_cpu_pools_hogs(void)
6360 {
6361 struct worker_pool *pool;
6362 int pi;
6363
6364 pr_info("Showing backtraces of running workers in stalled CPU-bound worker pools:\n");
6365
6366 rcu_read_lock();
6367
6368 for_each_pool(pool, pi) {
6369 if (pool->cpu_stall)
6370 show_cpu_pool_hog(pool);
6371
6372 }
6373
6374 rcu_read_unlock();
6375 }
6376
wq_watchdog_reset_touched(void)6377 static void wq_watchdog_reset_touched(void)
6378 {
6379 int cpu;
6380
6381 wq_watchdog_touched = jiffies;
6382 for_each_possible_cpu(cpu)
6383 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
6384 }
6385
wq_watchdog_timer_fn(struct timer_list * unused)6386 static void wq_watchdog_timer_fn(struct timer_list *unused)
6387 {
6388 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
6389 bool lockup_detected = false;
6390 bool cpu_pool_stall = false;
6391 unsigned long now = jiffies;
6392 struct worker_pool *pool;
6393 int pi;
6394
6395 if (!thresh)
6396 return;
6397
6398 rcu_read_lock();
6399
6400 for_each_pool(pool, pi) {
6401 unsigned long pool_ts, touched, ts;
6402
6403 pool->cpu_stall = false;
6404 if (list_empty(&pool->worklist))
6405 continue;
6406
6407 /*
6408 * If a virtual machine is stopped by the host it can look to
6409 * the watchdog like a stall.
6410 */
6411 kvm_check_and_clear_guest_paused();
6412
6413 /* get the latest of pool and touched timestamps */
6414 if (pool->cpu >= 0)
6415 touched = READ_ONCE(per_cpu(wq_watchdog_touched_cpu, pool->cpu));
6416 else
6417 touched = READ_ONCE(wq_watchdog_touched);
6418 pool_ts = READ_ONCE(pool->watchdog_ts);
6419
6420 if (time_after(pool_ts, touched))
6421 ts = pool_ts;
6422 else
6423 ts = touched;
6424
6425 /* did we stall? */
6426 if (time_after(now, ts + thresh)) {
6427 lockup_detected = true;
6428 if (pool->cpu >= 0) {
6429 pool->cpu_stall = true;
6430 cpu_pool_stall = true;
6431 }
6432 pr_emerg("BUG: workqueue lockup - pool");
6433 pr_cont_pool_info(pool);
6434 pr_cont(" stuck for %us!\n",
6435 jiffies_to_msecs(now - pool_ts) / 1000);
6436 }
6437
6438
6439 }
6440
6441 rcu_read_unlock();
6442
6443 if (lockup_detected)
6444 show_all_workqueues();
6445
6446 if (cpu_pool_stall)
6447 show_cpu_pools_hogs();
6448
6449 wq_watchdog_reset_touched();
6450 mod_timer(&wq_watchdog_timer, jiffies + thresh);
6451 }
6452
wq_watchdog_touch(int cpu)6453 notrace void wq_watchdog_touch(int cpu)
6454 {
6455 if (cpu >= 0)
6456 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
6457
6458 wq_watchdog_touched = jiffies;
6459 }
6460
wq_watchdog_set_thresh(unsigned long thresh)6461 static void wq_watchdog_set_thresh(unsigned long thresh)
6462 {
6463 wq_watchdog_thresh = 0;
6464 del_timer_sync(&wq_watchdog_timer);
6465
6466 if (thresh) {
6467 wq_watchdog_thresh = thresh;
6468 wq_watchdog_reset_touched();
6469 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
6470 }
6471 }
6472
wq_watchdog_param_set_thresh(const char * val,const struct kernel_param * kp)6473 static int wq_watchdog_param_set_thresh(const char *val,
6474 const struct kernel_param *kp)
6475 {
6476 unsigned long thresh;
6477 int ret;
6478
6479 ret = kstrtoul(val, 0, &thresh);
6480 if (ret)
6481 return ret;
6482
6483 if (system_wq)
6484 wq_watchdog_set_thresh(thresh);
6485 else
6486 wq_watchdog_thresh = thresh;
6487
6488 return 0;
6489 }
6490
6491 static const struct kernel_param_ops wq_watchdog_thresh_ops = {
6492 .set = wq_watchdog_param_set_thresh,
6493 .get = param_get_ulong,
6494 };
6495
6496 module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
6497 0644);
6498
wq_watchdog_init(void)6499 static void wq_watchdog_init(void)
6500 {
6501 timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
6502 wq_watchdog_set_thresh(wq_watchdog_thresh);
6503 }
6504
6505 #else /* CONFIG_WQ_WATCHDOG */
6506
wq_watchdog_init(void)6507 static inline void wq_watchdog_init(void) { }
6508
6509 #endif /* CONFIG_WQ_WATCHDOG */
6510
restrict_unbound_cpumask(const char * name,const struct cpumask * mask)6511 static void __init restrict_unbound_cpumask(const char *name, const struct cpumask *mask)
6512 {
6513 if (!cpumask_intersects(wq_unbound_cpumask, mask)) {
6514 pr_warn("workqueue: Restricting unbound_cpumask (%*pb) with %s (%*pb) leaves no CPU, ignoring\n",
6515 cpumask_pr_args(wq_unbound_cpumask), name, cpumask_pr_args(mask));
6516 return;
6517 }
6518
6519 cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, mask);
6520 }
6521
6522 /**
6523 * workqueue_init_early - early init for workqueue subsystem
6524 *
6525 * This is the first step of three-staged workqueue subsystem initialization and
6526 * invoked as soon as the bare basics - memory allocation, cpumasks and idr are
6527 * up. It sets up all the data structures and system workqueues and allows early
6528 * boot code to create workqueues and queue/cancel work items. Actual work item
6529 * execution starts only after kthreads can be created and scheduled right
6530 * before early initcalls.
6531 */
workqueue_init_early(void)6532 void __init workqueue_init_early(void)
6533 {
6534 struct wq_pod_type *pt = &wq_pod_types[WQ_AFFN_SYSTEM];
6535 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
6536 int i, cpu;
6537
6538 BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
6539
6540 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
6541 cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
6542 restrict_unbound_cpumask("HK_TYPE_WQ", housekeeping_cpumask(HK_TYPE_WQ));
6543 restrict_unbound_cpumask("HK_TYPE_DOMAIN", housekeeping_cpumask(HK_TYPE_DOMAIN));
6544 if (!cpumask_empty(&wq_cmdline_cpumask))
6545 restrict_unbound_cpumask("workqueue.unbound_cpus", &wq_cmdline_cpumask);
6546
6547 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
6548
6549 wq_update_pod_attrs_buf = alloc_workqueue_attrs();
6550 BUG_ON(!wq_update_pod_attrs_buf);
6551
6552 /* initialize WQ_AFFN_SYSTEM pods */
6553 pt->pod_cpus = kcalloc(1, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
6554 pt->pod_node = kcalloc(1, sizeof(pt->pod_node[0]), GFP_KERNEL);
6555 pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
6556 BUG_ON(!pt->pod_cpus || !pt->pod_node || !pt->cpu_pod);
6557
6558 BUG_ON(!zalloc_cpumask_var_node(&pt->pod_cpus[0], GFP_KERNEL, NUMA_NO_NODE));
6559
6560 pt->nr_pods = 1;
6561 cpumask_copy(pt->pod_cpus[0], cpu_possible_mask);
6562 pt->pod_node[0] = NUMA_NO_NODE;
6563 pt->cpu_pod[0] = 0;
6564
6565 /* initialize CPU pools */
6566 for_each_possible_cpu(cpu) {
6567 struct worker_pool *pool;
6568
6569 i = 0;
6570 for_each_cpu_worker_pool(pool, cpu) {
6571 BUG_ON(init_worker_pool(pool));
6572 pool->cpu = cpu;
6573 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
6574 cpumask_copy(pool->attrs->__pod_cpumask, cpumask_of(cpu));
6575 pool->attrs->nice = std_nice[i++];
6576 pool->attrs->affn_strict = true;
6577 pool->node = cpu_to_node(cpu);
6578
6579 /* alloc pool ID */
6580 mutex_lock(&wq_pool_mutex);
6581 BUG_ON(worker_pool_assign_id(pool));
6582 mutex_unlock(&wq_pool_mutex);
6583 }
6584 }
6585
6586 /* create default unbound and ordered wq attrs */
6587 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
6588 struct workqueue_attrs *attrs;
6589
6590 BUG_ON(!(attrs = alloc_workqueue_attrs()));
6591 attrs->nice = std_nice[i];
6592 unbound_std_wq_attrs[i] = attrs;
6593
6594 /*
6595 * An ordered wq should have only one pwq as ordering is
6596 * guaranteed by max_active which is enforced by pwqs.
6597 */
6598 BUG_ON(!(attrs = alloc_workqueue_attrs()));
6599 attrs->nice = std_nice[i];
6600 attrs->ordered = true;
6601 ordered_wq_attrs[i] = attrs;
6602 }
6603
6604 system_wq = alloc_workqueue("events", 0, 0);
6605 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
6606 system_long_wq = alloc_workqueue("events_long", 0, 0);
6607 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
6608 WQ_MAX_ACTIVE);
6609 system_freezable_wq = alloc_workqueue("events_freezable",
6610 WQ_FREEZABLE, 0);
6611 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
6612 WQ_POWER_EFFICIENT, 0);
6613 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
6614 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
6615 0);
6616 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
6617 !system_unbound_wq || !system_freezable_wq ||
6618 !system_power_efficient_wq ||
6619 !system_freezable_power_efficient_wq);
6620 }
6621
wq_cpu_intensive_thresh_init(void)6622 static void __init wq_cpu_intensive_thresh_init(void)
6623 {
6624 unsigned long thresh;
6625 unsigned long bogo;
6626
6627 pwq_release_worker = kthread_create_worker(0, "pool_workqueue_release");
6628 BUG_ON(IS_ERR(pwq_release_worker));
6629
6630 /* if the user set it to a specific value, keep it */
6631 if (wq_cpu_intensive_thresh_us != ULONG_MAX)
6632 return;
6633
6634 /*
6635 * The default of 10ms is derived from the fact that most modern (as of
6636 * 2023) processors can do a lot in 10ms and that it's just below what
6637 * most consider human-perceivable. However, the kernel also runs on a
6638 * lot slower CPUs including microcontrollers where the threshold is way
6639 * too low.
6640 *
6641 * Let's scale up the threshold upto 1 second if BogoMips is below 4000.
6642 * This is by no means accurate but it doesn't have to be. The mechanism
6643 * is still useful even when the threshold is fully scaled up. Also, as
6644 * the reports would usually be applicable to everyone, some machines
6645 * operating on longer thresholds won't significantly diminish their
6646 * usefulness.
6647 */
6648 thresh = 10 * USEC_PER_MSEC;
6649
6650 /* see init/calibrate.c for lpj -> BogoMIPS calculation */
6651 bogo = max_t(unsigned long, loops_per_jiffy / 500000 * HZ, 1);
6652 if (bogo < 4000)
6653 thresh = min_t(unsigned long, thresh * 4000 / bogo, USEC_PER_SEC);
6654
6655 pr_debug("wq_cpu_intensive_thresh: lpj=%lu BogoMIPS=%lu thresh_us=%lu\n",
6656 loops_per_jiffy, bogo, thresh);
6657
6658 wq_cpu_intensive_thresh_us = thresh;
6659 }
6660
6661 /**
6662 * workqueue_init - bring workqueue subsystem fully online
6663 *
6664 * This is the second step of three-staged workqueue subsystem initialization
6665 * and invoked as soon as kthreads can be created and scheduled. Workqueues have
6666 * been created and work items queued on them, but there are no kworkers
6667 * executing the work items yet. Populate the worker pools with the initial
6668 * workers and enable future kworker creations.
6669 */
workqueue_init(void)6670 void __init workqueue_init(void)
6671 {
6672 struct workqueue_struct *wq;
6673 struct worker_pool *pool;
6674 int cpu, bkt;
6675
6676 wq_cpu_intensive_thresh_init();
6677
6678 mutex_lock(&wq_pool_mutex);
6679
6680 /*
6681 * Per-cpu pools created earlier could be missing node hint. Fix them
6682 * up. Also, create a rescuer for workqueues that requested it.
6683 */
6684 for_each_possible_cpu(cpu) {
6685 for_each_cpu_worker_pool(pool, cpu) {
6686 pool->node = cpu_to_node(cpu);
6687 }
6688 }
6689
6690 list_for_each_entry(wq, &workqueues, list) {
6691 WARN(init_rescuer(wq),
6692 "workqueue: failed to create early rescuer for %s",
6693 wq->name);
6694 }
6695
6696 mutex_unlock(&wq_pool_mutex);
6697
6698 /* create the initial workers */
6699 for_each_online_cpu(cpu) {
6700 for_each_cpu_worker_pool(pool, cpu) {
6701 pool->flags &= ~POOL_DISASSOCIATED;
6702 BUG_ON(!create_worker(pool));
6703 }
6704 }
6705
6706 hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
6707 BUG_ON(!create_worker(pool));
6708
6709 wq_online = true;
6710 wq_watchdog_init();
6711 }
6712
6713 /*
6714 * Initialize @pt by first initializing @pt->cpu_pod[] with pod IDs according to
6715 * @cpu_shares_pod(). Each subset of CPUs that share a pod is assigned a unique
6716 * and consecutive pod ID. The rest of @pt is initialized accordingly.
6717 */
init_pod_type(struct wq_pod_type * pt,bool (* cpus_share_pod)(int,int))6718 static void __init init_pod_type(struct wq_pod_type *pt,
6719 bool (*cpus_share_pod)(int, int))
6720 {
6721 int cur, pre, cpu, pod;
6722
6723 pt->nr_pods = 0;
6724
6725 /* init @pt->cpu_pod[] according to @cpus_share_pod() */
6726 pt->cpu_pod = kcalloc(nr_cpu_ids, sizeof(pt->cpu_pod[0]), GFP_KERNEL);
6727 BUG_ON(!pt->cpu_pod);
6728
6729 for_each_possible_cpu(cur) {
6730 for_each_possible_cpu(pre) {
6731 if (pre >= cur) {
6732 pt->cpu_pod[cur] = pt->nr_pods++;
6733 break;
6734 }
6735 if (cpus_share_pod(cur, pre)) {
6736 pt->cpu_pod[cur] = pt->cpu_pod[pre];
6737 break;
6738 }
6739 }
6740 }
6741
6742 /* init the rest to match @pt->cpu_pod[] */
6743 pt->pod_cpus = kcalloc(pt->nr_pods, sizeof(pt->pod_cpus[0]), GFP_KERNEL);
6744 pt->pod_node = kcalloc(pt->nr_pods, sizeof(pt->pod_node[0]), GFP_KERNEL);
6745 BUG_ON(!pt->pod_cpus || !pt->pod_node);
6746
6747 for (pod = 0; pod < pt->nr_pods; pod++)
6748 BUG_ON(!zalloc_cpumask_var(&pt->pod_cpus[pod], GFP_KERNEL));
6749
6750 for_each_possible_cpu(cpu) {
6751 cpumask_set_cpu(cpu, pt->pod_cpus[pt->cpu_pod[cpu]]);
6752 pt->pod_node[pt->cpu_pod[cpu]] = cpu_to_node(cpu);
6753 }
6754 }
6755
cpus_dont_share(int cpu0,int cpu1)6756 static bool __init cpus_dont_share(int cpu0, int cpu1)
6757 {
6758 return false;
6759 }
6760
cpus_share_smt(int cpu0,int cpu1)6761 static bool __init cpus_share_smt(int cpu0, int cpu1)
6762 {
6763 #ifdef CONFIG_SCHED_SMT
6764 return cpumask_test_cpu(cpu0, cpu_smt_mask(cpu1));
6765 #else
6766 return false;
6767 #endif
6768 }
6769
cpus_share_numa(int cpu0,int cpu1)6770 static bool __init cpus_share_numa(int cpu0, int cpu1)
6771 {
6772 return cpu_to_node(cpu0) == cpu_to_node(cpu1);
6773 }
6774
6775 /**
6776 * workqueue_init_topology - initialize CPU pods for unbound workqueues
6777 *
6778 * This is the third step of there-staged workqueue subsystem initialization and
6779 * invoked after SMP and topology information are fully initialized. It
6780 * initializes the unbound CPU pods accordingly.
6781 */
workqueue_init_topology(void)6782 void __init workqueue_init_topology(void)
6783 {
6784 struct workqueue_struct *wq;
6785 int cpu;
6786
6787 init_pod_type(&wq_pod_types[WQ_AFFN_CPU], cpus_dont_share);
6788 init_pod_type(&wq_pod_types[WQ_AFFN_SMT], cpus_share_smt);
6789 init_pod_type(&wq_pod_types[WQ_AFFN_CACHE], cpus_share_cache);
6790 init_pod_type(&wq_pod_types[WQ_AFFN_NUMA], cpus_share_numa);
6791
6792 mutex_lock(&wq_pool_mutex);
6793
6794 /*
6795 * Workqueues allocated earlier would have all CPUs sharing the default
6796 * worker pool. Explicitly call wq_update_pod() on all workqueue and CPU
6797 * combinations to apply per-pod sharing.
6798 */
6799 list_for_each_entry(wq, &workqueues, list) {
6800 for_each_online_cpu(cpu) {
6801 wq_update_pod(wq, cpu, cpu, true);
6802 }
6803 }
6804
6805 mutex_unlock(&wq_pool_mutex);
6806 }
6807
__warn_flushing_systemwide_wq(void)6808 void __warn_flushing_systemwide_wq(void)
6809 {
6810 pr_warn("WARNING: Flushing system-wide workqueues will be prohibited in near future.\n");
6811 dump_stack();
6812 }
6813 EXPORT_SYMBOL(__warn_flushing_systemwide_wq);
6814
workqueue_unbound_cpus_setup(char * str)6815 static int __init workqueue_unbound_cpus_setup(char *str)
6816 {
6817 if (cpulist_parse(str, &wq_cmdline_cpumask) < 0) {
6818 cpumask_clear(&wq_cmdline_cpumask);
6819 pr_warn("workqueue.unbound_cpus: incorrect CPU range, using default\n");
6820 }
6821
6822 return 1;
6823 }
6824 __setup("workqueue.unbound_cpus=", workqueue_unbound_cpus_setup);
6825