Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost
[cris-mirror.git] / kernel / workqueue.c
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1 /*
2 * kernel/workqueue.c - generic async execution with shared worker pool
4 * Copyright (C) 2002 Ingo Molnar
6 * Derived from the taskqueue/keventd code by:
7 * David Woodhouse <dwmw2@infradead.org>
8 * Andrew Morton
9 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
10 * Theodore Ts'o <tytso@mit.edu>
12 * Made to use alloc_percpu by Christoph Lameter.
14 * Copyright (C) 2010 SUSE Linux Products GmbH
15 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
17 * This is the generic async execution mechanism. Work items as are
18 * executed in process context. The worker pool is shared and
19 * automatically managed. There are two worker pools for each CPU (one for
20 * normal work items and the other for high priority ones) and some extra
21 * pools for workqueues which are not bound to any specific CPU - the
22 * number of these backing pools is dynamic.
24 * Please read Documentation/core-api/workqueue.rst for details.
27 #include <linux/export.h>
28 #include <linux/kernel.h>
29 #include <linux/sched.h>
30 #include <linux/init.h>
31 #include <linux/signal.h>
32 #include <linux/completion.h>
33 #include <linux/workqueue.h>
34 #include <linux/slab.h>
35 #include <linux/cpu.h>
36 #include <linux/notifier.h>
37 #include <linux/kthread.h>
38 #include <linux/hardirq.h>
39 #include <linux/mempolicy.h>
40 #include <linux/freezer.h>
41 #include <linux/debug_locks.h>
42 #include <linux/lockdep.h>
43 #include <linux/idr.h>
44 #include <linux/jhash.h>
45 #include <linux/hashtable.h>
46 #include <linux/rculist.h>
47 #include <linux/nodemask.h>
48 #include <linux/moduleparam.h>
49 #include <linux/uaccess.h>
50 #include <linux/sched/isolation.h>
51 #include <linux/nmi.h>
53 #include "workqueue_internal.h"
55 enum {
57 * worker_pool flags
59 * A bound pool is either associated or disassociated with its CPU.
60 * While associated (!DISASSOCIATED), all workers are bound to the
61 * CPU and none has %WORKER_UNBOUND set and concurrency management
62 * is in effect.
64 * While DISASSOCIATED, the cpu may be offline and all workers have
65 * %WORKER_UNBOUND set and concurrency management disabled, and may
66 * be executing on any CPU. The pool behaves as an unbound one.
68 * Note that DISASSOCIATED should be flipped only while holding
69 * attach_mutex to avoid changing binding state while
70 * worker_attach_to_pool() is in progress.
72 POOL_MANAGER_ACTIVE = 1 << 0, /* being managed */
73 POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
75 /* worker flags */
76 WORKER_DIE = 1 << 1, /* die die die */
77 WORKER_IDLE = 1 << 2, /* is idle */
78 WORKER_PREP = 1 << 3, /* preparing to run works */
79 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
80 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
81 WORKER_REBOUND = 1 << 8, /* worker was rebound */
83 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_CPU_INTENSIVE |
84 WORKER_UNBOUND | WORKER_REBOUND,
86 NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */
88 UNBOUND_POOL_HASH_ORDER = 6, /* hashed by pool->attrs */
89 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
91 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
92 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
94 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
95 /* call for help after 10ms
96 (min two ticks) */
97 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
98 CREATE_COOLDOWN = HZ, /* time to breath after fail */
101 * Rescue workers are used only on emergencies and shared by
102 * all cpus. Give MIN_NICE.
104 RESCUER_NICE_LEVEL = MIN_NICE,
105 HIGHPRI_NICE_LEVEL = MIN_NICE,
107 WQ_NAME_LEN = 24,
111 * Structure fields follow one of the following exclusion rules.
113 * I: Modifiable by initialization/destruction paths and read-only for
114 * everyone else.
116 * P: Preemption protected. Disabling preemption is enough and should
117 * only be modified and accessed from the local cpu.
119 * L: pool->lock protected. Access with pool->lock held.
121 * X: During normal operation, modification requires pool->lock and should
122 * be done only from local cpu. Either disabling preemption on local
123 * cpu or grabbing pool->lock is enough for read access. If
124 * POOL_DISASSOCIATED is set, it's identical to L.
126 * A: pool->attach_mutex protected.
128 * PL: wq_pool_mutex protected.
130 * PR: wq_pool_mutex protected for writes. Sched-RCU protected for reads.
132 * PW: wq_pool_mutex and wq->mutex protected for writes. Either for reads.
134 * PWR: wq_pool_mutex and wq->mutex protected for writes. Either or
135 * sched-RCU for reads.
137 * WQ: wq->mutex protected.
139 * WR: wq->mutex protected for writes. Sched-RCU protected for reads.
141 * MD: wq_mayday_lock protected.
144 /* struct worker is defined in workqueue_internal.h */
146 struct worker_pool {
147 spinlock_t lock; /* the pool lock */
148 int cpu; /* I: the associated cpu */
149 int node; /* I: the associated node ID */
150 int id; /* I: pool ID */
151 unsigned int flags; /* X: flags */
153 unsigned long watchdog_ts; /* L: watchdog timestamp */
155 struct list_head worklist; /* L: list of pending works */
156 int nr_workers; /* L: total number of workers */
158 /* nr_idle includes the ones off idle_list for rebinding */
159 int nr_idle; /* L: currently idle ones */
161 struct list_head idle_list; /* X: list of idle workers */
162 struct timer_list idle_timer; /* L: worker idle timeout */
163 struct timer_list mayday_timer; /* L: SOS timer for workers */
165 /* a workers is either on busy_hash or idle_list, or the manager */
166 DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
167 /* L: hash of busy workers */
169 /* see manage_workers() for details on the two manager mutexes */
170 struct worker *manager; /* L: purely informational */
171 struct mutex attach_mutex; /* attach/detach exclusion */
172 struct list_head workers; /* A: attached workers */
173 struct completion *detach_completion; /* all workers detached */
175 struct ida worker_ida; /* worker IDs for task name */
177 struct workqueue_attrs *attrs; /* I: worker attributes */
178 struct hlist_node hash_node; /* PL: unbound_pool_hash node */
179 int refcnt; /* PL: refcnt for unbound pools */
182 * The current concurrency level. As it's likely to be accessed
183 * from other CPUs during try_to_wake_up(), put it in a separate
184 * cacheline.
186 atomic_t nr_running ____cacheline_aligned_in_smp;
189 * Destruction of pool is sched-RCU protected to allow dereferences
190 * from get_work_pool().
192 struct rcu_head rcu;
193 } ____cacheline_aligned_in_smp;
196 * The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
197 * of work_struct->data are used for flags and the remaining high bits
198 * point to the pwq; thus, pwqs need to be aligned at two's power of the
199 * number of flag bits.
201 struct pool_workqueue {
202 struct worker_pool *pool; /* I: the associated pool */
203 struct workqueue_struct *wq; /* I: the owning workqueue */
204 int work_color; /* L: current color */
205 int flush_color; /* L: flushing color */
206 int refcnt; /* L: reference count */
207 int nr_in_flight[WORK_NR_COLORS];
208 /* L: nr of in_flight works */
209 int nr_active; /* L: nr of active works */
210 int max_active; /* L: max active works */
211 struct list_head delayed_works; /* L: delayed works */
212 struct list_head pwqs_node; /* WR: node on wq->pwqs */
213 struct list_head mayday_node; /* MD: node on wq->maydays */
216 * Release of unbound pwq is punted to system_wq. See put_pwq()
217 * and pwq_unbound_release_workfn() for details. pool_workqueue
218 * itself is also sched-RCU protected so that the first pwq can be
219 * determined without grabbing wq->mutex.
221 struct work_struct unbound_release_work;
222 struct rcu_head rcu;
223 } __aligned(1 << WORK_STRUCT_FLAG_BITS);
226 * Structure used to wait for workqueue flush.
228 struct wq_flusher {
229 struct list_head list; /* WQ: list of flushers */
230 int flush_color; /* WQ: flush color waiting for */
231 struct completion done; /* flush completion */
234 struct wq_device;
237 * The externally visible workqueue. It relays the issued work items to
238 * the appropriate worker_pool through its pool_workqueues.
240 struct workqueue_struct {
241 struct list_head pwqs; /* WR: all pwqs of this wq */
242 struct list_head list; /* PR: list of all workqueues */
244 struct mutex mutex; /* protects this wq */
245 int work_color; /* WQ: current work color */
246 int flush_color; /* WQ: current flush color */
247 atomic_t nr_pwqs_to_flush; /* flush in progress */
248 struct wq_flusher *first_flusher; /* WQ: first flusher */
249 struct list_head flusher_queue; /* WQ: flush waiters */
250 struct list_head flusher_overflow; /* WQ: flush overflow list */
252 struct list_head maydays; /* MD: pwqs requesting rescue */
253 struct worker *rescuer; /* I: rescue worker */
255 int nr_drainers; /* WQ: drain in progress */
256 int saved_max_active; /* WQ: saved pwq max_active */
258 struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */
259 struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */
261 #ifdef CONFIG_SYSFS
262 struct wq_device *wq_dev; /* I: for sysfs interface */
263 #endif
264 #ifdef CONFIG_LOCKDEP
265 struct lockdep_map lockdep_map;
266 #endif
267 char name[WQ_NAME_LEN]; /* I: workqueue name */
270 * Destruction of workqueue_struct is sched-RCU protected to allow
271 * walking the workqueues list without grabbing wq_pool_mutex.
272 * This is used to dump all workqueues from sysrq.
274 struct rcu_head rcu;
276 /* hot fields used during command issue, aligned to cacheline */
277 unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */
278 struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
279 struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */
282 static struct kmem_cache *pwq_cache;
284 static cpumask_var_t *wq_numa_possible_cpumask;
285 /* possible CPUs of each node */
287 static bool wq_disable_numa;
288 module_param_named(disable_numa, wq_disable_numa, bool, 0444);
290 /* see the comment above the definition of WQ_POWER_EFFICIENT */
291 static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
292 module_param_named(power_efficient, wq_power_efficient, bool, 0444);
294 static bool wq_online; /* can kworkers be created yet? */
296 static bool wq_numa_enabled; /* unbound NUMA affinity enabled */
298 /* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
299 static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
301 static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
302 static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
303 static DECLARE_WAIT_QUEUE_HEAD(wq_manager_wait); /* wait for manager to go away */
305 static LIST_HEAD(workqueues); /* PR: list of all workqueues */
306 static bool workqueue_freezing; /* PL: have wqs started freezing? */
308 /* PL: allowable cpus for unbound wqs and work items */
309 static cpumask_var_t wq_unbound_cpumask;
311 /* CPU where unbound work was last round robin scheduled from this CPU */
312 static DEFINE_PER_CPU(int, wq_rr_cpu_last);
315 * Local execution of unbound work items is no longer guaranteed. The
316 * following always forces round-robin CPU selection on unbound work items
317 * to uncover usages which depend on it.
319 #ifdef CONFIG_DEBUG_WQ_FORCE_RR_CPU
320 static bool wq_debug_force_rr_cpu = true;
321 #else
322 static bool wq_debug_force_rr_cpu = false;
323 #endif
324 module_param_named(debug_force_rr_cpu, wq_debug_force_rr_cpu, bool, 0644);
326 /* the per-cpu worker pools */
327 static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools);
329 static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
331 /* PL: hash of all unbound pools keyed by pool->attrs */
332 static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
334 /* I: attributes used when instantiating standard unbound pools on demand */
335 static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
337 /* I: attributes used when instantiating ordered pools on demand */
338 static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];
340 struct workqueue_struct *system_wq __read_mostly;
341 EXPORT_SYMBOL(system_wq);
342 struct workqueue_struct *system_highpri_wq __read_mostly;
343 EXPORT_SYMBOL_GPL(system_highpri_wq);
344 struct workqueue_struct *system_long_wq __read_mostly;
345 EXPORT_SYMBOL_GPL(system_long_wq);
346 struct workqueue_struct *system_unbound_wq __read_mostly;
347 EXPORT_SYMBOL_GPL(system_unbound_wq);
348 struct workqueue_struct *system_freezable_wq __read_mostly;
349 EXPORT_SYMBOL_GPL(system_freezable_wq);
350 struct workqueue_struct *system_power_efficient_wq __read_mostly;
351 EXPORT_SYMBOL_GPL(system_power_efficient_wq);
352 struct workqueue_struct *system_freezable_power_efficient_wq __read_mostly;
353 EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
355 static int worker_thread(void *__worker);
356 static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
358 #define CREATE_TRACE_POINTS
359 #include <trace/events/workqueue.h>
361 #define assert_rcu_or_pool_mutex() \
362 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
363 !lockdep_is_held(&wq_pool_mutex), \
364 "sched RCU or wq_pool_mutex should be held")
366 #define assert_rcu_or_wq_mutex(wq) \
367 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
368 !lockdep_is_held(&wq->mutex), \
369 "sched RCU or wq->mutex should be held")
371 #define assert_rcu_or_wq_mutex_or_pool_mutex(wq) \
372 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
373 !lockdep_is_held(&wq->mutex) && \
374 !lockdep_is_held(&wq_pool_mutex), \
375 "sched RCU, wq->mutex or wq_pool_mutex should be held")
377 #define for_each_cpu_worker_pool(pool, cpu) \
378 for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
379 (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
380 (pool)++)
383 * for_each_pool - iterate through all worker_pools in the system
384 * @pool: iteration cursor
385 * @pi: integer used for iteration
387 * This must be called either with wq_pool_mutex held or sched RCU read
388 * locked. If the pool needs to be used beyond the locking in effect, the
389 * caller is responsible for guaranteeing that the pool stays online.
391 * The if/else clause exists only for the lockdep assertion and can be
392 * ignored.
394 #define for_each_pool(pool, pi) \
395 idr_for_each_entry(&worker_pool_idr, pool, pi) \
396 if (({ assert_rcu_or_pool_mutex(); false; })) { } \
397 else
400 * for_each_pool_worker - iterate through all workers of a worker_pool
401 * @worker: iteration cursor
402 * @pool: worker_pool to iterate workers of
404 * This must be called with @pool->attach_mutex.
406 * The if/else clause exists only for the lockdep assertion and can be
407 * ignored.
409 #define for_each_pool_worker(worker, pool) \
410 list_for_each_entry((worker), &(pool)->workers, node) \
411 if (({ lockdep_assert_held(&pool->attach_mutex); false; })) { } \
412 else
415 * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
416 * @pwq: iteration cursor
417 * @wq: the target workqueue
419 * This must be called either with wq->mutex held or sched RCU read locked.
420 * If the pwq needs to be used beyond the locking in effect, the caller is
421 * responsible for guaranteeing that the pwq stays online.
423 * The if/else clause exists only for the lockdep assertion and can be
424 * ignored.
426 #define for_each_pwq(pwq, wq) \
427 list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
428 if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \
429 else
431 #ifdef CONFIG_DEBUG_OBJECTS_WORK
433 static struct debug_obj_descr work_debug_descr;
435 static void *work_debug_hint(void *addr)
437 return ((struct work_struct *) addr)->func;
440 static bool work_is_static_object(void *addr)
442 struct work_struct *work = addr;
444 return test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work));
448 * fixup_init is called when:
449 * - an active object is initialized
451 static bool work_fixup_init(void *addr, enum debug_obj_state state)
453 struct work_struct *work = addr;
455 switch (state) {
456 case ODEBUG_STATE_ACTIVE:
457 cancel_work_sync(work);
458 debug_object_init(work, &work_debug_descr);
459 return true;
460 default:
461 return false;
466 * fixup_free is called when:
467 * - an active object is freed
469 static bool work_fixup_free(void *addr, enum debug_obj_state state)
471 struct work_struct *work = addr;
473 switch (state) {
474 case ODEBUG_STATE_ACTIVE:
475 cancel_work_sync(work);
476 debug_object_free(work, &work_debug_descr);
477 return true;
478 default:
479 return false;
483 static struct debug_obj_descr work_debug_descr = {
484 .name = "work_struct",
485 .debug_hint = work_debug_hint,
486 .is_static_object = work_is_static_object,
487 .fixup_init = work_fixup_init,
488 .fixup_free = work_fixup_free,
491 static inline void debug_work_activate(struct work_struct *work)
493 debug_object_activate(work, &work_debug_descr);
496 static inline void debug_work_deactivate(struct work_struct *work)
498 debug_object_deactivate(work, &work_debug_descr);
501 void __init_work(struct work_struct *work, int onstack)
503 if (onstack)
504 debug_object_init_on_stack(work, &work_debug_descr);
505 else
506 debug_object_init(work, &work_debug_descr);
508 EXPORT_SYMBOL_GPL(__init_work);
510 void destroy_work_on_stack(struct work_struct *work)
512 debug_object_free(work, &work_debug_descr);
514 EXPORT_SYMBOL_GPL(destroy_work_on_stack);
516 void destroy_delayed_work_on_stack(struct delayed_work *work)
518 destroy_timer_on_stack(&work->timer);
519 debug_object_free(&work->work, &work_debug_descr);
521 EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack);
523 #else
524 static inline void debug_work_activate(struct work_struct *work) { }
525 static inline void debug_work_deactivate(struct work_struct *work) { }
526 #endif
529 * worker_pool_assign_id - allocate ID and assing it to @pool
530 * @pool: the pool pointer of interest
532 * Returns 0 if ID in [0, WORK_OFFQ_POOL_NONE) is allocated and assigned
533 * successfully, -errno on failure.
535 static int worker_pool_assign_id(struct worker_pool *pool)
537 int ret;
539 lockdep_assert_held(&wq_pool_mutex);
541 ret = idr_alloc(&worker_pool_idr, pool, 0, WORK_OFFQ_POOL_NONE,
542 GFP_KERNEL);
543 if (ret >= 0) {
544 pool->id = ret;
545 return 0;
547 return ret;
551 * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
552 * @wq: the target workqueue
553 * @node: the node ID
555 * This must be called with any of wq_pool_mutex, wq->mutex or sched RCU
556 * read locked.
557 * If the pwq needs to be used beyond the locking in effect, the caller is
558 * responsible for guaranteeing that the pwq stays online.
560 * Return: The unbound pool_workqueue for @node.
562 static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
563 int node)
565 assert_rcu_or_wq_mutex_or_pool_mutex(wq);
568 * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
569 * delayed item is pending. The plan is to keep CPU -> NODE
570 * mapping valid and stable across CPU on/offlines. Once that
571 * happens, this workaround can be removed.
573 if (unlikely(node == NUMA_NO_NODE))
574 return wq->dfl_pwq;
576 return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
579 static unsigned int work_color_to_flags(int color)
581 return color << WORK_STRUCT_COLOR_SHIFT;
584 static int get_work_color(struct work_struct *work)
586 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
587 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
590 static int work_next_color(int color)
592 return (color + 1) % WORK_NR_COLORS;
596 * While queued, %WORK_STRUCT_PWQ is set and non flag bits of a work's data
597 * contain the pointer to the queued pwq. Once execution starts, the flag
598 * is cleared and the high bits contain OFFQ flags and pool ID.
600 * set_work_pwq(), set_work_pool_and_clear_pending(), mark_work_canceling()
601 * and clear_work_data() can be used to set the pwq, pool or clear
602 * work->data. These functions should only be called while the work is
603 * owned - ie. while the PENDING bit is set.
605 * get_work_pool() and get_work_pwq() can be used to obtain the pool or pwq
606 * corresponding to a work. Pool is available once the work has been
607 * queued anywhere after initialization until it is sync canceled. pwq is
608 * available only while the work item is queued.
610 * %WORK_OFFQ_CANCELING is used to mark a work item which is being
611 * canceled. While being canceled, a work item may have its PENDING set
612 * but stay off timer and worklist for arbitrarily long and nobody should
613 * try to steal the PENDING bit.
615 static inline void set_work_data(struct work_struct *work, unsigned long data,
616 unsigned long flags)
618 WARN_ON_ONCE(!work_pending(work));
619 atomic_long_set(&work->data, data | flags | work_static(work));
622 static void set_work_pwq(struct work_struct *work, struct pool_workqueue *pwq,
623 unsigned long extra_flags)
625 set_work_data(work, (unsigned long)pwq,
626 WORK_STRUCT_PENDING | WORK_STRUCT_PWQ | extra_flags);
629 static void set_work_pool_and_keep_pending(struct work_struct *work,
630 int pool_id)
632 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT,
633 WORK_STRUCT_PENDING);
636 static void set_work_pool_and_clear_pending(struct work_struct *work,
637 int pool_id)
640 * The following wmb is paired with the implied mb in
641 * test_and_set_bit(PENDING) and ensures all updates to @work made
642 * here are visible to and precede any updates by the next PENDING
643 * owner.
645 smp_wmb();
646 set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0);
648 * The following mb guarantees that previous clear of a PENDING bit
649 * will not be reordered with any speculative LOADS or STORES from
650 * work->current_func, which is executed afterwards. This possible
651 * reordering can lead to a missed execution on attempt to qeueue
652 * the same @work. E.g. consider this case:
654 * CPU#0 CPU#1
655 * ---------------------------- --------------------------------
657 * 1 STORE event_indicated
658 * 2 queue_work_on() {
659 * 3 test_and_set_bit(PENDING)
660 * 4 } set_..._and_clear_pending() {
661 * 5 set_work_data() # clear bit
662 * 6 smp_mb()
663 * 7 work->current_func() {
664 * 8 LOAD event_indicated
667 * Without an explicit full barrier speculative LOAD on line 8 can
668 * be executed before CPU#0 does STORE on line 1. If that happens,
669 * CPU#0 observes the PENDING bit is still set and new execution of
670 * a @work is not queued in a hope, that CPU#1 will eventually
671 * finish the queued @work. Meanwhile CPU#1 does not see
672 * event_indicated is set, because speculative LOAD was executed
673 * before actual STORE.
675 smp_mb();
678 static void clear_work_data(struct work_struct *work)
680 smp_wmb(); /* see set_work_pool_and_clear_pending() */
681 set_work_data(work, WORK_STRUCT_NO_POOL, 0);
684 static struct pool_workqueue *get_work_pwq(struct work_struct *work)
686 unsigned long data = atomic_long_read(&work->data);
688 if (data & WORK_STRUCT_PWQ)
689 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
690 else
691 return NULL;
695 * get_work_pool - return the worker_pool a given work was associated with
696 * @work: the work item of interest
698 * Pools are created and destroyed under wq_pool_mutex, and allows read
699 * access under sched-RCU read lock. As such, this function should be
700 * called under wq_pool_mutex or with preemption disabled.
702 * All fields of the returned pool are accessible as long as the above
703 * mentioned locking is in effect. If the returned pool needs to be used
704 * beyond the critical section, the caller is responsible for ensuring the
705 * returned pool is and stays online.
707 * Return: The worker_pool @work was last associated with. %NULL if none.
709 static struct worker_pool *get_work_pool(struct work_struct *work)
711 unsigned long data = atomic_long_read(&work->data);
712 int pool_id;
714 assert_rcu_or_pool_mutex();
716 if (data & WORK_STRUCT_PWQ)
717 return ((struct pool_workqueue *)
718 (data & WORK_STRUCT_WQ_DATA_MASK))->pool;
720 pool_id = data >> WORK_OFFQ_POOL_SHIFT;
721 if (pool_id == WORK_OFFQ_POOL_NONE)
722 return NULL;
724 return idr_find(&worker_pool_idr, pool_id);
728 * get_work_pool_id - return the worker pool ID a given work is associated with
729 * @work: the work item of interest
731 * Return: The worker_pool ID @work was last associated with.
732 * %WORK_OFFQ_POOL_NONE if none.
734 static int get_work_pool_id(struct work_struct *work)
736 unsigned long data = atomic_long_read(&work->data);
738 if (data & WORK_STRUCT_PWQ)
739 return ((struct pool_workqueue *)
740 (data & WORK_STRUCT_WQ_DATA_MASK))->pool->id;
742 return data >> WORK_OFFQ_POOL_SHIFT;
745 static void mark_work_canceling(struct work_struct *work)
747 unsigned long pool_id = get_work_pool_id(work);
749 pool_id <<= WORK_OFFQ_POOL_SHIFT;
750 set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING);
753 static bool work_is_canceling(struct work_struct *work)
755 unsigned long data = atomic_long_read(&work->data);
757 return !(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_CANCELING);
761 * Policy functions. These define the policies on how the global worker
762 * pools are managed. Unless noted otherwise, these functions assume that
763 * they're being called with pool->lock held.
766 static bool __need_more_worker(struct worker_pool *pool)
768 return !atomic_read(&pool->nr_running);
772 * Need to wake up a worker? Called from anything but currently
773 * running workers.
775 * Note that, because unbound workers never contribute to nr_running, this
776 * function will always return %true for unbound pools as long as the
777 * worklist isn't empty.
779 static bool need_more_worker(struct worker_pool *pool)
781 return !list_empty(&pool->worklist) && __need_more_worker(pool);
784 /* Can I start working? Called from busy but !running workers. */
785 static bool may_start_working(struct worker_pool *pool)
787 return pool->nr_idle;
790 /* Do I need to keep working? Called from currently running workers. */
791 static bool keep_working(struct worker_pool *pool)
793 return !list_empty(&pool->worklist) &&
794 atomic_read(&pool->nr_running) <= 1;
797 /* Do we need a new worker? Called from manager. */
798 static bool need_to_create_worker(struct worker_pool *pool)
800 return need_more_worker(pool) && !may_start_working(pool);
803 /* Do we have too many workers and should some go away? */
804 static bool too_many_workers(struct worker_pool *pool)
806 bool managing = pool->flags & POOL_MANAGER_ACTIVE;
807 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
808 int nr_busy = pool->nr_workers - nr_idle;
810 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
814 * Wake up functions.
817 /* Return the first idle worker. Safe with preemption disabled */
818 static struct worker *first_idle_worker(struct worker_pool *pool)
820 if (unlikely(list_empty(&pool->idle_list)))
821 return NULL;
823 return list_first_entry(&pool->idle_list, struct worker, entry);
827 * wake_up_worker - wake up an idle worker
828 * @pool: worker pool to wake worker from
830 * Wake up the first idle worker of @pool.
832 * CONTEXT:
833 * spin_lock_irq(pool->lock).
835 static void wake_up_worker(struct worker_pool *pool)
837 struct worker *worker = first_idle_worker(pool);
839 if (likely(worker))
840 wake_up_process(worker->task);
844 * wq_worker_waking_up - a worker is waking up
845 * @task: task waking up
846 * @cpu: CPU @task is waking up to
848 * This function is called during try_to_wake_up() when a worker is
849 * being awoken.
851 * CONTEXT:
852 * spin_lock_irq(rq->lock)
854 void wq_worker_waking_up(struct task_struct *task, int cpu)
856 struct worker *worker = kthread_data(task);
858 if (!(worker->flags & WORKER_NOT_RUNNING)) {
859 WARN_ON_ONCE(worker->pool->cpu != cpu);
860 atomic_inc(&worker->pool->nr_running);
865 * wq_worker_sleeping - a worker is going to sleep
866 * @task: task going to sleep
868 * This function is called during schedule() when a busy worker is
869 * going to sleep. Worker on the same cpu can be woken up by
870 * returning pointer to its task.
872 * CONTEXT:
873 * spin_lock_irq(rq->lock)
875 * Return:
876 * Worker task on @cpu to wake up, %NULL if none.
878 struct task_struct *wq_worker_sleeping(struct task_struct *task)
880 struct worker *worker = kthread_data(task), *to_wakeup = NULL;
881 struct worker_pool *pool;
884 * Rescuers, which may not have all the fields set up like normal
885 * workers, also reach here, let's not access anything before
886 * checking NOT_RUNNING.
888 if (worker->flags & WORKER_NOT_RUNNING)
889 return NULL;
891 pool = worker->pool;
893 /* this can only happen on the local cpu */
894 if (WARN_ON_ONCE(pool->cpu != raw_smp_processor_id()))
895 return NULL;
898 * The counterpart of the following dec_and_test, implied mb,
899 * worklist not empty test sequence is in insert_work().
900 * Please read comment there.
902 * NOT_RUNNING is clear. This means that we're bound to and
903 * running on the local cpu w/ rq lock held and preemption
904 * disabled, which in turn means that none else could be
905 * manipulating idle_list, so dereferencing idle_list without pool
906 * lock is safe.
908 if (atomic_dec_and_test(&pool->nr_running) &&
909 !list_empty(&pool->worklist))
910 to_wakeup = first_idle_worker(pool);
911 return to_wakeup ? to_wakeup->task : NULL;
915 * worker_set_flags - set worker flags and adjust nr_running accordingly
916 * @worker: self
917 * @flags: flags to set
919 * Set @flags in @worker->flags and adjust nr_running accordingly.
921 * CONTEXT:
922 * spin_lock_irq(pool->lock)
924 static inline void worker_set_flags(struct worker *worker, unsigned int flags)
926 struct worker_pool *pool = worker->pool;
928 WARN_ON_ONCE(worker->task != current);
930 /* If transitioning into NOT_RUNNING, adjust nr_running. */
931 if ((flags & WORKER_NOT_RUNNING) &&
932 !(worker->flags & WORKER_NOT_RUNNING)) {
933 atomic_dec(&pool->nr_running);
936 worker->flags |= flags;
940 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
941 * @worker: self
942 * @flags: flags to clear
944 * Clear @flags in @worker->flags and adjust nr_running accordingly.
946 * CONTEXT:
947 * spin_lock_irq(pool->lock)
949 static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
951 struct worker_pool *pool = worker->pool;
952 unsigned int oflags = worker->flags;
954 WARN_ON_ONCE(worker->task != current);
956 worker->flags &= ~flags;
959 * If transitioning out of NOT_RUNNING, increment nr_running. Note
960 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
961 * of multiple flags, not a single flag.
963 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
964 if (!(worker->flags & WORKER_NOT_RUNNING))
965 atomic_inc(&pool->nr_running);
969 * find_worker_executing_work - find worker which is executing a work
970 * @pool: pool of interest
971 * @work: work to find worker for
973 * Find a worker which is executing @work on @pool by searching
974 * @pool->busy_hash which is keyed by the address of @work. For a worker
975 * to match, its current execution should match the address of @work and
976 * its work function. This is to avoid unwanted dependency between
977 * unrelated work executions through a work item being recycled while still
978 * being executed.
980 * This is a bit tricky. A work item may be freed once its execution
981 * starts and nothing prevents the freed area from being recycled for
982 * another work item. If the same work item address ends up being reused
983 * before the original execution finishes, workqueue will identify the
984 * recycled work item as currently executing and make it wait until the
985 * current execution finishes, introducing an unwanted dependency.
987 * This function checks the work item address and work function to avoid
988 * false positives. Note that this isn't complete as one may construct a
989 * work function which can introduce dependency onto itself through a
990 * recycled work item. Well, if somebody wants to shoot oneself in the
991 * foot that badly, there's only so much we can do, and if such deadlock
992 * actually occurs, it should be easy to locate the culprit work function.
994 * CONTEXT:
995 * spin_lock_irq(pool->lock).
997 * Return:
998 * Pointer to worker which is executing @work if found, %NULL
999 * otherwise.
1001 static struct worker *find_worker_executing_work(struct worker_pool *pool,
1002 struct work_struct *work)
1004 struct worker *worker;
1006 hash_for_each_possible(pool->busy_hash, worker, hentry,
1007 (unsigned long)work)
1008 if (worker->current_work == work &&
1009 worker->current_func == work->func)
1010 return worker;
1012 return NULL;
1016 * move_linked_works - move linked works to a list
1017 * @work: start of series of works to be scheduled
1018 * @head: target list to append @work to
1019 * @nextp: out parameter for nested worklist walking
1021 * Schedule linked works starting from @work to @head. Work series to
1022 * be scheduled starts at @work and includes any consecutive work with
1023 * WORK_STRUCT_LINKED set in its predecessor.
1025 * If @nextp is not NULL, it's updated to point to the next work of
1026 * the last scheduled work. This allows move_linked_works() to be
1027 * nested inside outer list_for_each_entry_safe().
1029 * CONTEXT:
1030 * spin_lock_irq(pool->lock).
1032 static void move_linked_works(struct work_struct *work, struct list_head *head,
1033 struct work_struct **nextp)
1035 struct work_struct *n;
1038 * Linked worklist will always end before the end of the list,
1039 * use NULL for list head.
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;
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.
1052 if (nextp)
1053 *nextp = n;
1057 * get_pwq - get an extra reference on the specified pool_workqueue
1058 * @pwq: pool_workqueue to get
1060 * Obtain an extra reference on @pwq. The caller should guarantee that
1061 * @pwq has positive refcnt and be holding the matching pool->lock.
1063 static void get_pwq(struct pool_workqueue *pwq)
1065 lockdep_assert_held(&pwq->pool->lock);
1066 WARN_ON_ONCE(pwq->refcnt <= 0);
1067 pwq->refcnt++;
1071 * put_pwq - put a pool_workqueue reference
1072 * @pwq: pool_workqueue to put
1074 * Drop a reference of @pwq. If its refcnt reaches zero, schedule its
1075 * destruction. The caller should be holding the matching pool->lock.
1077 static void put_pwq(struct pool_workqueue *pwq)
1079 lockdep_assert_held(&pwq->pool->lock);
1080 if (likely(--pwq->refcnt))
1081 return;
1082 if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
1083 return;
1085 * @pwq can't be released under pool->lock, bounce to
1086 * pwq_unbound_release_workfn(). This never recurses on the same
1087 * pool->lock as this path is taken only for unbound workqueues and
1088 * the release work item is scheduled on a per-cpu workqueue. To
1089 * avoid lockdep warning, unbound pool->locks are given lockdep
1090 * subclass of 1 in get_unbound_pool().
1092 schedule_work(&pwq->unbound_release_work);
1096 * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
1097 * @pwq: pool_workqueue to put (can be %NULL)
1099 * put_pwq() with locking. This function also allows %NULL @pwq.
1101 static void put_pwq_unlocked(struct pool_workqueue *pwq)
1103 if (pwq) {
1105 * As both pwqs and pools are sched-RCU protected, the
1106 * following lock operations are safe.
1108 spin_lock_irq(&pwq->pool->lock);
1109 put_pwq(pwq);
1110 spin_unlock_irq(&pwq->pool->lock);
1114 static void pwq_activate_delayed_work(struct work_struct *work)
1116 struct pool_workqueue *pwq = get_work_pwq(work);
1118 trace_workqueue_activate_work(work);
1119 if (list_empty(&pwq->pool->worklist))
1120 pwq->pool->watchdog_ts = jiffies;
1121 move_linked_works(work, &pwq->pool->worklist, NULL);
1122 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1123 pwq->nr_active++;
1126 static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
1128 struct work_struct *work = list_first_entry(&pwq->delayed_works,
1129 struct work_struct, entry);
1131 pwq_activate_delayed_work(work);
1135 * pwq_dec_nr_in_flight - decrement pwq's nr_in_flight
1136 * @pwq: pwq of interest
1137 * @color: color of work which left the queue
1139 * A work either has completed or is removed from pending queue,
1140 * decrement nr_in_flight of its pwq and handle workqueue flushing.
1142 * CONTEXT:
1143 * spin_lock_irq(pool->lock).
1145 static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
1147 /* uncolored work items don't participate in flushing or nr_active */
1148 if (color == WORK_NO_COLOR)
1149 goto out_put;
1151 pwq->nr_in_flight[color]--;
1153 pwq->nr_active--;
1154 if (!list_empty(&pwq->delayed_works)) {
1155 /* one down, submit a delayed one */
1156 if (pwq->nr_active < pwq->max_active)
1157 pwq_activate_first_delayed(pwq);
1160 /* is flush in progress and are we at the flushing tip? */
1161 if (likely(pwq->flush_color != color))
1162 goto out_put;
1164 /* are there still in-flight works? */
1165 if (pwq->nr_in_flight[color])
1166 goto out_put;
1168 /* this pwq is done, clear flush_color */
1169 pwq->flush_color = -1;
1172 * If this was the last pwq, wake up the first flusher. It
1173 * will handle the rest.
1175 if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
1176 complete(&pwq->wq->first_flusher->done);
1177 out_put:
1178 put_pwq(pwq);
1182 * try_to_grab_pending - steal work item from worklist and disable irq
1183 * @work: work item to steal
1184 * @is_dwork: @work is a delayed_work
1185 * @flags: place to store irq state
1187 * Try to grab PENDING bit of @work. This function can handle @work in any
1188 * stable state - idle, on timer or on worklist.
1190 * Return:
1191 * 1 if @work was pending and we successfully stole PENDING
1192 * 0 if @work was idle and we claimed PENDING
1193 * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry
1194 * -ENOENT if someone else is canceling @work, this state may persist
1195 * for arbitrarily long
1197 * Note:
1198 * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting
1199 * interrupted while holding PENDING and @work off queue, irq must be
1200 * disabled on entry. This, combined with delayed_work->timer being
1201 * irqsafe, ensures that we return -EAGAIN for finite short period of time.
1203 * On successful return, >= 0, irq is disabled and the caller is
1204 * responsible for releasing it using local_irq_restore(*@flags).
1206 * This function is safe to call from any context including IRQ handler.
1208 static int try_to_grab_pending(struct work_struct *work, bool is_dwork,
1209 unsigned long *flags)
1211 struct worker_pool *pool;
1212 struct pool_workqueue *pwq;
1214 local_irq_save(*flags);
1216 /* try to steal the timer if it exists */
1217 if (is_dwork) {
1218 struct delayed_work *dwork = to_delayed_work(work);
1221 * dwork->timer is irqsafe. If del_timer() fails, it's
1222 * guaranteed that the timer is not queued anywhere and not
1223 * running on the local CPU.
1225 if (likely(del_timer(&dwork->timer)))
1226 return 1;
1229 /* try to claim PENDING the normal way */
1230 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
1231 return 0;
1234 * The queueing is in progress, or it is already queued. Try to
1235 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
1237 pool = get_work_pool(work);
1238 if (!pool)
1239 goto fail;
1241 spin_lock(&pool->lock);
1243 * work->data is guaranteed to point to pwq only while the work
1244 * item is queued on pwq->wq, and both updating work->data to point
1245 * to pwq on queueing and to pool on dequeueing are done under
1246 * pwq->pool->lock. This in turn guarantees that, if work->data
1247 * points to pwq which is associated with a locked pool, the work
1248 * item is currently queued on that pool.
1250 pwq = get_work_pwq(work);
1251 if (pwq && pwq->pool == pool) {
1252 debug_work_deactivate(work);
1255 * A delayed work item cannot be grabbed directly because
1256 * it might have linked NO_COLOR work items which, if left
1257 * on the delayed_list, will confuse pwq->nr_active
1258 * management later on and cause stall. Make sure the work
1259 * item is activated before grabbing.
1261 if (*work_data_bits(work) & WORK_STRUCT_DELAYED)
1262 pwq_activate_delayed_work(work);
1264 list_del_init(&work->entry);
1265 pwq_dec_nr_in_flight(pwq, get_work_color(work));
1267 /* work->data points to pwq iff queued, point to pool */
1268 set_work_pool_and_keep_pending(work, pool->id);
1270 spin_unlock(&pool->lock);
1271 return 1;
1273 spin_unlock(&pool->lock);
1274 fail:
1275 local_irq_restore(*flags);
1276 if (work_is_canceling(work))
1277 return -ENOENT;
1278 cpu_relax();
1279 return -EAGAIN;
1283 * insert_work - insert a work into a pool
1284 * @pwq: pwq @work belongs to
1285 * @work: work to insert
1286 * @head: insertion point
1287 * @extra_flags: extra WORK_STRUCT_* flags to set
1289 * Insert @work which belongs to @pwq after @head. @extra_flags is or'd to
1290 * work_struct flags.
1292 * CONTEXT:
1293 * spin_lock_irq(pool->lock).
1295 static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
1296 struct list_head *head, unsigned int extra_flags)
1298 struct worker_pool *pool = pwq->pool;
1300 /* we own @work, set data and link */
1301 set_work_pwq(work, pwq, extra_flags);
1302 list_add_tail(&work->entry, head);
1303 get_pwq(pwq);
1306 * Ensure either wq_worker_sleeping() sees the above
1307 * list_add_tail() or we see zero nr_running to avoid workers lying
1308 * around lazily while there are works to be processed.
1310 smp_mb();
1312 if (__need_more_worker(pool))
1313 wake_up_worker(pool);
1317 * Test whether @work is being queued from another work executing on the
1318 * same workqueue.
1320 static bool is_chained_work(struct workqueue_struct *wq)
1322 struct worker *worker;
1324 worker = current_wq_worker();
1326 * Return %true iff I'm a worker execuing a work item on @wq. If
1327 * I'm @worker, it's safe to dereference it without locking.
1329 return worker && worker->current_pwq->wq == wq;
1333 * When queueing an unbound work item to a wq, prefer local CPU if allowed
1334 * by wq_unbound_cpumask. Otherwise, round robin among the allowed ones to
1335 * avoid perturbing sensitive tasks.
1337 static int wq_select_unbound_cpu(int cpu)
1339 static bool printed_dbg_warning;
1340 int new_cpu;
1342 if (likely(!wq_debug_force_rr_cpu)) {
1343 if (cpumask_test_cpu(cpu, wq_unbound_cpumask))
1344 return cpu;
1345 } else if (!printed_dbg_warning) {
1346 pr_warn("workqueue: round-robin CPU selection forced, expect performance impact\n");
1347 printed_dbg_warning = true;
1350 if (cpumask_empty(wq_unbound_cpumask))
1351 return cpu;
1353 new_cpu = __this_cpu_read(wq_rr_cpu_last);
1354 new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
1355 if (unlikely(new_cpu >= nr_cpu_ids)) {
1356 new_cpu = cpumask_first_and(wq_unbound_cpumask, cpu_online_mask);
1357 if (unlikely(new_cpu >= nr_cpu_ids))
1358 return cpu;
1360 __this_cpu_write(wq_rr_cpu_last, new_cpu);
1362 return new_cpu;
1365 static void __queue_work(int cpu, struct workqueue_struct *wq,
1366 struct work_struct *work)
1368 struct pool_workqueue *pwq;
1369 struct worker_pool *last_pool;
1370 struct list_head *worklist;
1371 unsigned int work_flags;
1372 unsigned int req_cpu = cpu;
1375 * While a work item is PENDING && off queue, a task trying to
1376 * steal the PENDING will busy-loop waiting for it to either get
1377 * queued or lose PENDING. Grabbing PENDING and queueing should
1378 * happen with IRQ disabled.
1380 lockdep_assert_irqs_disabled();
1382 debug_work_activate(work);
1384 /* if draining, only works from the same workqueue are allowed */
1385 if (unlikely(wq->flags & __WQ_DRAINING) &&
1386 WARN_ON_ONCE(!is_chained_work(wq)))
1387 return;
1388 retry:
1389 if (req_cpu == WORK_CPU_UNBOUND)
1390 cpu = wq_select_unbound_cpu(raw_smp_processor_id());
1392 /* pwq which will be used unless @work is executing elsewhere */
1393 if (!(wq->flags & WQ_UNBOUND))
1394 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
1395 else
1396 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
1399 * If @work was previously on a different pool, it might still be
1400 * running there, in which case the work needs to be queued on that
1401 * pool to guarantee non-reentrancy.
1403 last_pool = get_work_pool(work);
1404 if (last_pool && last_pool != pwq->pool) {
1405 struct worker *worker;
1407 spin_lock(&last_pool->lock);
1409 worker = find_worker_executing_work(last_pool, work);
1411 if (worker && worker->current_pwq->wq == wq) {
1412 pwq = worker->current_pwq;
1413 } else {
1414 /* meh... not running there, queue here */
1415 spin_unlock(&last_pool->lock);
1416 spin_lock(&pwq->pool->lock);
1418 } else {
1419 spin_lock(&pwq->pool->lock);
1423 * pwq is determined and locked. For unbound pools, we could have
1424 * raced with pwq release and it could already be dead. If its
1425 * refcnt is zero, repeat pwq selection. Note that pwqs never die
1426 * without another pwq replacing it in the numa_pwq_tbl or while
1427 * work items are executing on it, so the retrying is guaranteed to
1428 * make forward-progress.
1430 if (unlikely(!pwq->refcnt)) {
1431 if (wq->flags & WQ_UNBOUND) {
1432 spin_unlock(&pwq->pool->lock);
1433 cpu_relax();
1434 goto retry;
1436 /* oops */
1437 WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
1438 wq->name, cpu);
1441 /* pwq determined, queue */
1442 trace_workqueue_queue_work(req_cpu, pwq, work);
1444 if (WARN_ON(!list_empty(&work->entry))) {
1445 spin_unlock(&pwq->pool->lock);
1446 return;
1449 pwq->nr_in_flight[pwq->work_color]++;
1450 work_flags = work_color_to_flags(pwq->work_color);
1452 if (likely(pwq->nr_active < pwq->max_active)) {
1453 trace_workqueue_activate_work(work);
1454 pwq->nr_active++;
1455 worklist = &pwq->pool->worklist;
1456 if (list_empty(worklist))
1457 pwq->pool->watchdog_ts = jiffies;
1458 } else {
1459 work_flags |= WORK_STRUCT_DELAYED;
1460 worklist = &pwq->delayed_works;
1463 insert_work(pwq, work, worklist, work_flags);
1465 spin_unlock(&pwq->pool->lock);
1469 * queue_work_on - queue work on specific cpu
1470 * @cpu: CPU number to execute work on
1471 * @wq: workqueue to use
1472 * @work: work to queue
1474 * We queue the work to a specific CPU, the caller must ensure it
1475 * can't go away.
1477 * Return: %false if @work was already on a queue, %true otherwise.
1479 bool queue_work_on(int cpu, struct workqueue_struct *wq,
1480 struct work_struct *work)
1482 bool ret = false;
1483 unsigned long flags;
1485 local_irq_save(flags);
1487 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1488 __queue_work(cpu, wq, work);
1489 ret = true;
1492 local_irq_restore(flags);
1493 return ret;
1495 EXPORT_SYMBOL(queue_work_on);
1497 void delayed_work_timer_fn(struct timer_list *t)
1499 struct delayed_work *dwork = from_timer(dwork, t, timer);
1501 /* should have been called from irqsafe timer with irq already off */
1502 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
1504 EXPORT_SYMBOL(delayed_work_timer_fn);
1506 static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
1507 struct delayed_work *dwork, unsigned long delay)
1509 struct timer_list *timer = &dwork->timer;
1510 struct work_struct *work = &dwork->work;
1512 WARN_ON_ONCE(!wq);
1513 WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
1514 WARN_ON_ONCE(timer_pending(timer));
1515 WARN_ON_ONCE(!list_empty(&work->entry));
1518 * If @delay is 0, queue @dwork->work immediately. This is for
1519 * both optimization and correctness. The earliest @timer can
1520 * expire is on the closest next tick and delayed_work users depend
1521 * on that there's no such delay when @delay is 0.
1523 if (!delay) {
1524 __queue_work(cpu, wq, &dwork->work);
1525 return;
1528 dwork->wq = wq;
1529 dwork->cpu = cpu;
1530 timer->expires = jiffies + delay;
1532 if (unlikely(cpu != WORK_CPU_UNBOUND))
1533 add_timer_on(timer, cpu);
1534 else
1535 add_timer(timer);
1539 * queue_delayed_work_on - queue work on specific CPU after delay
1540 * @cpu: CPU number to execute work on
1541 * @wq: workqueue to use
1542 * @dwork: work to queue
1543 * @delay: number of jiffies to wait before queueing
1545 * Return: %false if @work was already on a queue, %true otherwise. If
1546 * @delay is zero and @dwork is idle, it will be scheduled for immediate
1547 * execution.
1549 bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1550 struct delayed_work *dwork, unsigned long delay)
1552 struct work_struct *work = &dwork->work;
1553 bool ret = false;
1554 unsigned long flags;
1556 /* read the comment in __queue_work() */
1557 local_irq_save(flags);
1559 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1560 __queue_delayed_work(cpu, wq, dwork, delay);
1561 ret = true;
1564 local_irq_restore(flags);
1565 return ret;
1567 EXPORT_SYMBOL(queue_delayed_work_on);
1570 * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
1571 * @cpu: CPU number to execute work on
1572 * @wq: workqueue to use
1573 * @dwork: work to queue
1574 * @delay: number of jiffies to wait before queueing
1576 * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
1577 * modify @dwork's timer so that it expires after @delay. If @delay is
1578 * zero, @work is guaranteed to be scheduled immediately regardless of its
1579 * current state.
1581 * Return: %false if @dwork was idle and queued, %true if @dwork was
1582 * pending and its timer was modified.
1584 * This function is safe to call from any context including IRQ handler.
1585 * See try_to_grab_pending() for details.
1587 bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
1588 struct delayed_work *dwork, unsigned long delay)
1590 unsigned long flags;
1591 int ret;
1593 do {
1594 ret = try_to_grab_pending(&dwork->work, true, &flags);
1595 } while (unlikely(ret == -EAGAIN));
1597 if (likely(ret >= 0)) {
1598 __queue_delayed_work(cpu, wq, dwork, delay);
1599 local_irq_restore(flags);
1602 /* -ENOENT from try_to_grab_pending() becomes %true */
1603 return ret;
1605 EXPORT_SYMBOL_GPL(mod_delayed_work_on);
1608 * worker_enter_idle - enter idle state
1609 * @worker: worker which is entering idle state
1611 * @worker is entering idle state. Update stats and idle timer if
1612 * necessary.
1614 * LOCKING:
1615 * spin_lock_irq(pool->lock).
1617 static void worker_enter_idle(struct worker *worker)
1619 struct worker_pool *pool = worker->pool;
1621 if (WARN_ON_ONCE(worker->flags & WORKER_IDLE) ||
1622 WARN_ON_ONCE(!list_empty(&worker->entry) &&
1623 (worker->hentry.next || worker->hentry.pprev)))
1624 return;
1626 /* can't use worker_set_flags(), also called from create_worker() */
1627 worker->flags |= WORKER_IDLE;
1628 pool->nr_idle++;
1629 worker->last_active = jiffies;
1631 /* idle_list is LIFO */
1632 list_add(&worker->entry, &pool->idle_list);
1634 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1635 mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT);
1638 * Sanity check nr_running. Because unbind_workers() releases
1639 * pool->lock between setting %WORKER_UNBOUND and zapping
1640 * nr_running, the warning may trigger spuriously. Check iff
1641 * unbind is not in progress.
1643 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
1644 pool->nr_workers == pool->nr_idle &&
1645 atomic_read(&pool->nr_running));
1649 * worker_leave_idle - leave idle state
1650 * @worker: worker which is leaving idle state
1652 * @worker is leaving idle state. Update stats.
1654 * LOCKING:
1655 * spin_lock_irq(pool->lock).
1657 static void worker_leave_idle(struct worker *worker)
1659 struct worker_pool *pool = worker->pool;
1661 if (WARN_ON_ONCE(!(worker->flags & WORKER_IDLE)))
1662 return;
1663 worker_clr_flags(worker, WORKER_IDLE);
1664 pool->nr_idle--;
1665 list_del_init(&worker->entry);
1668 static struct worker *alloc_worker(int node)
1670 struct worker *worker;
1672 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node);
1673 if (worker) {
1674 INIT_LIST_HEAD(&worker->entry);
1675 INIT_LIST_HEAD(&worker->scheduled);
1676 INIT_LIST_HEAD(&worker->node);
1677 /* on creation a worker is in !idle && prep state */
1678 worker->flags = WORKER_PREP;
1680 return worker;
1684 * worker_attach_to_pool() - attach a worker to a pool
1685 * @worker: worker to be attached
1686 * @pool: the target pool
1688 * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and
1689 * cpu-binding of @worker are kept coordinated with the pool across
1690 * cpu-[un]hotplugs.
1692 static void worker_attach_to_pool(struct worker *worker,
1693 struct worker_pool *pool)
1695 mutex_lock(&pool->attach_mutex);
1698 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
1699 * online CPUs. It'll be re-applied when any of the CPUs come up.
1701 set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
1704 * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains
1705 * stable across this function. See the comments above the
1706 * flag definition for details.
1708 if (pool->flags & POOL_DISASSOCIATED)
1709 worker->flags |= WORKER_UNBOUND;
1711 list_add_tail(&worker->node, &pool->workers);
1713 mutex_unlock(&pool->attach_mutex);
1717 * worker_detach_from_pool() - detach a worker from its pool
1718 * @worker: worker which is attached to its pool
1719 * @pool: the pool @worker is attached to
1721 * Undo the attaching which had been done in worker_attach_to_pool(). The
1722 * caller worker shouldn't access to the pool after detached except it has
1723 * other reference to the pool.
1725 static void worker_detach_from_pool(struct worker *worker,
1726 struct worker_pool *pool)
1728 struct completion *detach_completion = NULL;
1730 mutex_lock(&pool->attach_mutex);
1731 list_del(&worker->node);
1732 if (list_empty(&pool->workers))
1733 detach_completion = pool->detach_completion;
1734 mutex_unlock(&pool->attach_mutex);
1736 /* clear leftover flags without pool->lock after it is detached */
1737 worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
1739 if (detach_completion)
1740 complete(detach_completion);
1744 * create_worker - create a new workqueue worker
1745 * @pool: pool the new worker will belong to
1747 * Create and start a new worker which is attached to @pool.
1749 * CONTEXT:
1750 * Might sleep. Does GFP_KERNEL allocations.
1752 * Return:
1753 * Pointer to the newly created worker.
1755 static struct worker *create_worker(struct worker_pool *pool)
1757 struct worker *worker = NULL;
1758 int id = -1;
1759 char id_buf[16];
1761 /* ID is needed to determine kthread name */
1762 id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL);
1763 if (id < 0)
1764 goto fail;
1766 worker = alloc_worker(pool->node);
1767 if (!worker)
1768 goto fail;
1770 worker->pool = pool;
1771 worker->id = id;
1773 if (pool->cpu >= 0)
1774 snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id,
1775 pool->attrs->nice < 0 ? "H" : "");
1776 else
1777 snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id);
1779 worker->task = kthread_create_on_node(worker_thread, worker, pool->node,
1780 "kworker/%s", id_buf);
1781 if (IS_ERR(worker->task))
1782 goto fail;
1784 set_user_nice(worker->task, pool->attrs->nice);
1785 kthread_bind_mask(worker->task, pool->attrs->cpumask);
1787 /* successful, attach the worker to the pool */
1788 worker_attach_to_pool(worker, pool);
1790 /* start the newly created worker */
1791 spin_lock_irq(&pool->lock);
1792 worker->pool->nr_workers++;
1793 worker_enter_idle(worker);
1794 wake_up_process(worker->task);
1795 spin_unlock_irq(&pool->lock);
1797 return worker;
1799 fail:
1800 if (id >= 0)
1801 ida_simple_remove(&pool->worker_ida, id);
1802 kfree(worker);
1803 return NULL;
1807 * destroy_worker - destroy a workqueue worker
1808 * @worker: worker to be destroyed
1810 * Destroy @worker and adjust @pool stats accordingly. The worker should
1811 * be idle.
1813 * CONTEXT:
1814 * spin_lock_irq(pool->lock).
1816 static void destroy_worker(struct worker *worker)
1818 struct worker_pool *pool = worker->pool;
1820 lockdep_assert_held(&pool->lock);
1822 /* sanity check frenzy */
1823 if (WARN_ON(worker->current_work) ||
1824 WARN_ON(!list_empty(&worker->scheduled)) ||
1825 WARN_ON(!(worker->flags & WORKER_IDLE)))
1826 return;
1828 pool->nr_workers--;
1829 pool->nr_idle--;
1831 list_del_init(&worker->entry);
1832 worker->flags |= WORKER_DIE;
1833 wake_up_process(worker->task);
1836 static void idle_worker_timeout(struct timer_list *t)
1838 struct worker_pool *pool = from_timer(pool, t, idle_timer);
1840 spin_lock_irq(&pool->lock);
1842 while (too_many_workers(pool)) {
1843 struct worker *worker;
1844 unsigned long expires;
1846 /* idle_list is kept in LIFO order, check the last one */
1847 worker = list_entry(pool->idle_list.prev, struct worker, entry);
1848 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1850 if (time_before(jiffies, expires)) {
1851 mod_timer(&pool->idle_timer, expires);
1852 break;
1855 destroy_worker(worker);
1858 spin_unlock_irq(&pool->lock);
1861 static void send_mayday(struct work_struct *work)
1863 struct pool_workqueue *pwq = get_work_pwq(work);
1864 struct workqueue_struct *wq = pwq->wq;
1866 lockdep_assert_held(&wq_mayday_lock);
1868 if (!wq->rescuer)
1869 return;
1871 /* mayday mayday mayday */
1872 if (list_empty(&pwq->mayday_node)) {
1874 * If @pwq is for an unbound wq, its base ref may be put at
1875 * any time due to an attribute change. Pin @pwq until the
1876 * rescuer is done with it.
1878 get_pwq(pwq);
1879 list_add_tail(&pwq->mayday_node, &wq->maydays);
1880 wake_up_process(wq->rescuer->task);
1884 static void pool_mayday_timeout(struct timer_list *t)
1886 struct worker_pool *pool = from_timer(pool, t, mayday_timer);
1887 struct work_struct *work;
1889 spin_lock_irq(&pool->lock);
1890 spin_lock(&wq_mayday_lock); /* for wq->maydays */
1892 if (need_to_create_worker(pool)) {
1894 * We've been trying to create a new worker but
1895 * haven't been successful. We might be hitting an
1896 * allocation deadlock. Send distress signals to
1897 * rescuers.
1899 list_for_each_entry(work, &pool->worklist, entry)
1900 send_mayday(work);
1903 spin_unlock(&wq_mayday_lock);
1904 spin_unlock_irq(&pool->lock);
1906 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
1910 * maybe_create_worker - create a new worker if necessary
1911 * @pool: pool to create a new worker for
1913 * Create a new worker for @pool if necessary. @pool is guaranteed to
1914 * have at least one idle worker on return from this function. If
1915 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1916 * sent to all rescuers with works scheduled on @pool to resolve
1917 * possible allocation deadlock.
1919 * On return, need_to_create_worker() is guaranteed to be %false and
1920 * may_start_working() %true.
1922 * LOCKING:
1923 * spin_lock_irq(pool->lock) which may be released and regrabbed
1924 * multiple times. Does GFP_KERNEL allocations. Called only from
1925 * manager.
1927 static void maybe_create_worker(struct worker_pool *pool)
1928 __releases(&pool->lock)
1929 __acquires(&pool->lock)
1931 restart:
1932 spin_unlock_irq(&pool->lock);
1934 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1935 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1937 while (true) {
1938 if (create_worker(pool) || !need_to_create_worker(pool))
1939 break;
1941 schedule_timeout_interruptible(CREATE_COOLDOWN);
1943 if (!need_to_create_worker(pool))
1944 break;
1947 del_timer_sync(&pool->mayday_timer);
1948 spin_lock_irq(&pool->lock);
1950 * This is necessary even after a new worker was just successfully
1951 * created as @pool->lock was dropped and the new worker might have
1952 * already become busy.
1954 if (need_to_create_worker(pool))
1955 goto restart;
1959 * manage_workers - manage worker pool
1960 * @worker: self
1962 * Assume the manager role and manage the worker pool @worker belongs
1963 * to. At any given time, there can be only zero or one manager per
1964 * pool. The exclusion is handled automatically by this function.
1966 * The caller can safely start processing works on false return. On
1967 * true return, it's guaranteed that need_to_create_worker() is false
1968 * and may_start_working() is true.
1970 * CONTEXT:
1971 * spin_lock_irq(pool->lock) which may be released and regrabbed
1972 * multiple times. Does GFP_KERNEL allocations.
1974 * Return:
1975 * %false if the pool doesn't need management and the caller can safely
1976 * start processing works, %true if management function was performed and
1977 * the conditions that the caller verified before calling the function may
1978 * no longer be true.
1980 static bool manage_workers(struct worker *worker)
1982 struct worker_pool *pool = worker->pool;
1984 if (pool->flags & POOL_MANAGER_ACTIVE)
1985 return false;
1987 pool->flags |= POOL_MANAGER_ACTIVE;
1988 pool->manager = worker;
1990 maybe_create_worker(pool);
1992 pool->manager = NULL;
1993 pool->flags &= ~POOL_MANAGER_ACTIVE;
1994 wake_up(&wq_manager_wait);
1995 return true;
1999 * process_one_work - process single work
2000 * @worker: self
2001 * @work: work to process
2003 * Process @work. This function contains all the logics necessary to
2004 * process a single work including synchronization against and
2005 * interaction with other workers on the same cpu, queueing and
2006 * flushing. As long as context requirement is met, any worker can
2007 * call this function to process a work.
2009 * CONTEXT:
2010 * spin_lock_irq(pool->lock) which is released and regrabbed.
2012 static void process_one_work(struct worker *worker, struct work_struct *work)
2013 __releases(&pool->lock)
2014 __acquires(&pool->lock)
2016 struct pool_workqueue *pwq = get_work_pwq(work);
2017 struct worker_pool *pool = worker->pool;
2018 bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
2019 int work_color;
2020 struct worker *collision;
2021 #ifdef CONFIG_LOCKDEP
2023 * It is permissible to free the struct work_struct from
2024 * inside the function that is called from it, this we need to
2025 * take into account for lockdep too. To avoid bogus "held
2026 * lock freed" warnings as well as problems when looking into
2027 * work->lockdep_map, make a copy and use that here.
2029 struct lockdep_map lockdep_map;
2031 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
2032 #endif
2033 /* ensure we're on the correct CPU */
2034 WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
2035 raw_smp_processor_id() != pool->cpu);
2038 * A single work shouldn't be executed concurrently by
2039 * multiple workers on a single cpu. Check whether anyone is
2040 * already processing the work. If so, defer the work to the
2041 * currently executing one.
2043 collision = find_worker_executing_work(pool, work);
2044 if (unlikely(collision)) {
2045 move_linked_works(work, &collision->scheduled, NULL);
2046 return;
2049 /* claim and dequeue */
2050 debug_work_deactivate(work);
2051 hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work);
2052 worker->current_work = work;
2053 worker->current_func = work->func;
2054 worker->current_pwq = pwq;
2055 work_color = get_work_color(work);
2057 list_del_init(&work->entry);
2060 * CPU intensive works don't participate in concurrency management.
2061 * They're the scheduler's responsibility. This takes @worker out
2062 * of concurrency management and the next code block will chain
2063 * execution of the pending work items.
2065 if (unlikely(cpu_intensive))
2066 worker_set_flags(worker, WORKER_CPU_INTENSIVE);
2069 * Wake up another worker if necessary. The condition is always
2070 * false for normal per-cpu workers since nr_running would always
2071 * be >= 1 at this point. This is used to chain execution of the
2072 * pending work items for WORKER_NOT_RUNNING workers such as the
2073 * UNBOUND and CPU_INTENSIVE ones.
2075 if (need_more_worker(pool))
2076 wake_up_worker(pool);
2079 * Record the last pool and clear PENDING which should be the last
2080 * update to @work. Also, do this inside @pool->lock so that
2081 * PENDING and queued state changes happen together while IRQ is
2082 * disabled.
2084 set_work_pool_and_clear_pending(work, pool->id);
2086 spin_unlock_irq(&pool->lock);
2088 lock_map_acquire(&pwq->wq->lockdep_map);
2089 lock_map_acquire(&lockdep_map);
2091 * Strictly speaking we should mark the invariant state without holding
2092 * any locks, that is, before these two lock_map_acquire()'s.
2094 * However, that would result in:
2096 * A(W1)
2097 * WFC(C)
2098 * A(W1)
2099 * C(C)
2101 * Which would create W1->C->W1 dependencies, even though there is no
2102 * actual deadlock possible. There are two solutions, using a
2103 * read-recursive acquire on the work(queue) 'locks', but this will then
2104 * hit the lockdep limitation on recursive locks, or simply discard
2105 * these locks.
2107 * AFAICT there is no possible deadlock scenario between the
2108 * flush_work() and complete() primitives (except for single-threaded
2109 * workqueues), so hiding them isn't a problem.
2111 lockdep_invariant_state(true);
2112 trace_workqueue_execute_start(work);
2113 worker->current_func(work);
2115 * While we must be careful to not use "work" after this, the trace
2116 * point will only record its address.
2118 trace_workqueue_execute_end(work);
2119 lock_map_release(&lockdep_map);
2120 lock_map_release(&pwq->wq->lockdep_map);
2122 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
2123 pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n"
2124 " last function: %pf\n",
2125 current->comm, preempt_count(), task_pid_nr(current),
2126 worker->current_func);
2127 debug_show_held_locks(current);
2128 dump_stack();
2132 * The following prevents a kworker from hogging CPU on !PREEMPT
2133 * kernels, where a requeueing work item waiting for something to
2134 * happen could deadlock with stop_machine as such work item could
2135 * indefinitely requeue itself while all other CPUs are trapped in
2136 * stop_machine. At the same time, report a quiescent RCU state so
2137 * the same condition doesn't freeze RCU.
2139 cond_resched();
2141 spin_lock_irq(&pool->lock);
2143 /* clear cpu intensive status */
2144 if (unlikely(cpu_intensive))
2145 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
2147 /* we're done with it, release */
2148 hash_del(&worker->hentry);
2149 worker->current_work = NULL;
2150 worker->current_func = NULL;
2151 worker->current_pwq = NULL;
2152 worker->desc_valid = false;
2153 pwq_dec_nr_in_flight(pwq, work_color);
2157 * process_scheduled_works - process scheduled works
2158 * @worker: self
2160 * Process all scheduled works. Please note that the scheduled list
2161 * may change while processing a work, so this function repeatedly
2162 * fetches a work from the top and executes it.
2164 * CONTEXT:
2165 * spin_lock_irq(pool->lock) which may be released and regrabbed
2166 * multiple times.
2168 static void process_scheduled_works(struct worker *worker)
2170 while (!list_empty(&worker->scheduled)) {
2171 struct work_struct *work = list_first_entry(&worker->scheduled,
2172 struct work_struct, entry);
2173 process_one_work(worker, work);
2178 * worker_thread - the worker thread function
2179 * @__worker: self
2181 * The worker thread function. All workers belong to a worker_pool -
2182 * either a per-cpu one or dynamic unbound one. These workers process all
2183 * work items regardless of their specific target workqueue. The only
2184 * exception is work items which belong to workqueues with a rescuer which
2185 * will be explained in rescuer_thread().
2187 * Return: 0
2189 static int worker_thread(void *__worker)
2191 struct worker *worker = __worker;
2192 struct worker_pool *pool = worker->pool;
2194 /* tell the scheduler that this is a workqueue worker */
2195 worker->task->flags |= PF_WQ_WORKER;
2196 woke_up:
2197 spin_lock_irq(&pool->lock);
2199 /* am I supposed to die? */
2200 if (unlikely(worker->flags & WORKER_DIE)) {
2201 spin_unlock_irq(&pool->lock);
2202 WARN_ON_ONCE(!list_empty(&worker->entry));
2203 worker->task->flags &= ~PF_WQ_WORKER;
2205 set_task_comm(worker->task, "kworker/dying");
2206 ida_simple_remove(&pool->worker_ida, worker->id);
2207 worker_detach_from_pool(worker, pool);
2208 kfree(worker);
2209 return 0;
2212 worker_leave_idle(worker);
2213 recheck:
2214 /* no more worker necessary? */
2215 if (!need_more_worker(pool))
2216 goto sleep;
2218 /* do we need to manage? */
2219 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
2220 goto recheck;
2223 * ->scheduled list can only be filled while a worker is
2224 * preparing to process a work or actually processing it.
2225 * Make sure nobody diddled with it while I was sleeping.
2227 WARN_ON_ONCE(!list_empty(&worker->scheduled));
2230 * Finish PREP stage. We're guaranteed to have at least one idle
2231 * worker or that someone else has already assumed the manager
2232 * role. This is where @worker starts participating in concurrency
2233 * management if applicable and concurrency management is restored
2234 * after being rebound. See rebind_workers() for details.
2236 worker_clr_flags(worker, WORKER_PREP | WORKER_REBOUND);
2238 do {
2239 struct work_struct *work =
2240 list_first_entry(&pool->worklist,
2241 struct work_struct, entry);
2243 pool->watchdog_ts = jiffies;
2245 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
2246 /* optimization path, not strictly necessary */
2247 process_one_work(worker, work);
2248 if (unlikely(!list_empty(&worker->scheduled)))
2249 process_scheduled_works(worker);
2250 } else {
2251 move_linked_works(work, &worker->scheduled, NULL);
2252 process_scheduled_works(worker);
2254 } while (keep_working(pool));
2256 worker_set_flags(worker, WORKER_PREP);
2257 sleep:
2259 * pool->lock is held and there's no work to process and no need to
2260 * manage, sleep. Workers are woken up only while holding
2261 * pool->lock or from local cpu, so setting the current state
2262 * before releasing pool->lock is enough to prevent losing any
2263 * event.
2265 worker_enter_idle(worker);
2266 __set_current_state(TASK_IDLE);
2267 spin_unlock_irq(&pool->lock);
2268 schedule();
2269 goto woke_up;
2273 * rescuer_thread - the rescuer thread function
2274 * @__rescuer: self
2276 * Workqueue rescuer thread function. There's one rescuer for each
2277 * workqueue which has WQ_MEM_RECLAIM set.
2279 * Regular work processing on a pool may block trying to create a new
2280 * worker which uses GFP_KERNEL allocation which has slight chance of
2281 * developing into deadlock if some works currently on the same queue
2282 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2283 * the problem rescuer solves.
2285 * When such condition is possible, the pool summons rescuers of all
2286 * workqueues which have works queued on the pool and let them process
2287 * those works so that forward progress can be guaranteed.
2289 * This should happen rarely.
2291 * Return: 0
2293 static int rescuer_thread(void *__rescuer)
2295 struct worker *rescuer = __rescuer;
2296 struct workqueue_struct *wq = rescuer->rescue_wq;
2297 struct list_head *scheduled = &rescuer->scheduled;
2298 bool should_stop;
2300 set_user_nice(current, RESCUER_NICE_LEVEL);
2303 * Mark rescuer as worker too. As WORKER_PREP is never cleared, it
2304 * doesn't participate in concurrency management.
2306 rescuer->task->flags |= PF_WQ_WORKER;
2307 repeat:
2308 set_current_state(TASK_IDLE);
2311 * By the time the rescuer is requested to stop, the workqueue
2312 * shouldn't have any work pending, but @wq->maydays may still have
2313 * pwq(s) queued. This can happen by non-rescuer workers consuming
2314 * all the work items before the rescuer got to them. Go through
2315 * @wq->maydays processing before acting on should_stop so that the
2316 * list is always empty on exit.
2318 should_stop = kthread_should_stop();
2320 /* see whether any pwq is asking for help */
2321 spin_lock_irq(&wq_mayday_lock);
2323 while (!list_empty(&wq->maydays)) {
2324 struct pool_workqueue *pwq = list_first_entry(&wq->maydays,
2325 struct pool_workqueue, mayday_node);
2326 struct worker_pool *pool = pwq->pool;
2327 struct work_struct *work, *n;
2328 bool first = true;
2330 __set_current_state(TASK_RUNNING);
2331 list_del_init(&pwq->mayday_node);
2333 spin_unlock_irq(&wq_mayday_lock);
2335 worker_attach_to_pool(rescuer, pool);
2337 spin_lock_irq(&pool->lock);
2338 rescuer->pool = pool;
2341 * Slurp in all works issued via this workqueue and
2342 * process'em.
2344 WARN_ON_ONCE(!list_empty(scheduled));
2345 list_for_each_entry_safe(work, n, &pool->worklist, entry) {
2346 if (get_work_pwq(work) == pwq) {
2347 if (first)
2348 pool->watchdog_ts = jiffies;
2349 move_linked_works(work, scheduled, &n);
2351 first = false;
2354 if (!list_empty(scheduled)) {
2355 process_scheduled_works(rescuer);
2358 * The above execution of rescued work items could
2359 * have created more to rescue through
2360 * pwq_activate_first_delayed() or chained
2361 * queueing. Let's put @pwq back on mayday list so
2362 * that such back-to-back work items, which may be
2363 * being used to relieve memory pressure, don't
2364 * incur MAYDAY_INTERVAL delay inbetween.
2366 if (need_to_create_worker(pool)) {
2367 spin_lock(&wq_mayday_lock);
2368 get_pwq(pwq);
2369 list_move_tail(&pwq->mayday_node, &wq->maydays);
2370 spin_unlock(&wq_mayday_lock);
2375 * Put the reference grabbed by send_mayday(). @pool won't
2376 * go away while we're still attached to it.
2378 put_pwq(pwq);
2381 * Leave this pool. If need_more_worker() is %true, notify a
2382 * regular worker; otherwise, we end up with 0 concurrency
2383 * and stalling the execution.
2385 if (need_more_worker(pool))
2386 wake_up_worker(pool);
2388 rescuer->pool = NULL;
2389 spin_unlock_irq(&pool->lock);
2391 worker_detach_from_pool(rescuer, pool);
2393 spin_lock_irq(&wq_mayday_lock);
2396 spin_unlock_irq(&wq_mayday_lock);
2398 if (should_stop) {
2399 __set_current_state(TASK_RUNNING);
2400 rescuer->task->flags &= ~PF_WQ_WORKER;
2401 return 0;
2404 /* rescuers should never participate in concurrency management */
2405 WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING));
2406 schedule();
2407 goto repeat;
2411 * check_flush_dependency - check for flush dependency sanity
2412 * @target_wq: workqueue being flushed
2413 * @target_work: work item being flushed (NULL for workqueue flushes)
2415 * %current is trying to flush the whole @target_wq or @target_work on it.
2416 * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
2417 * reclaiming memory or running on a workqueue which doesn't have
2418 * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
2419 * a deadlock.
2421 static void check_flush_dependency(struct workqueue_struct *target_wq,
2422 struct work_struct *target_work)
2424 work_func_t target_func = target_work ? target_work->func : NULL;
2425 struct worker *worker;
2427 if (target_wq->flags & WQ_MEM_RECLAIM)
2428 return;
2430 worker = current_wq_worker();
2432 WARN_ONCE(current->flags & PF_MEMALLOC,
2433 "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%pf",
2434 current->pid, current->comm, target_wq->name, target_func);
2435 WARN_ONCE(worker && ((worker->current_pwq->wq->flags &
2436 (WQ_MEM_RECLAIM | __WQ_LEGACY)) == WQ_MEM_RECLAIM),
2437 "workqueue: WQ_MEM_RECLAIM %s:%pf is flushing !WQ_MEM_RECLAIM %s:%pf",
2438 worker->current_pwq->wq->name, worker->current_func,
2439 target_wq->name, target_func);
2442 struct wq_barrier {
2443 struct work_struct work;
2444 struct completion done;
2445 struct task_struct *task; /* purely informational */
2448 static void wq_barrier_func(struct work_struct *work)
2450 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2451 complete(&barr->done);
2455 * insert_wq_barrier - insert a barrier work
2456 * @pwq: pwq to insert barrier into
2457 * @barr: wq_barrier to insert
2458 * @target: target work to attach @barr to
2459 * @worker: worker currently executing @target, NULL if @target is not executing
2461 * @barr is linked to @target such that @barr is completed only after
2462 * @target finishes execution. Please note that the ordering
2463 * guarantee is observed only with respect to @target and on the local
2464 * cpu.
2466 * Currently, a queued barrier can't be canceled. This is because
2467 * try_to_grab_pending() can't determine whether the work to be
2468 * grabbed is at the head of the queue and thus can't clear LINKED
2469 * flag of the previous work while there must be a valid next work
2470 * after a work with LINKED flag set.
2472 * Note that when @worker is non-NULL, @target may be modified
2473 * underneath us, so we can't reliably determine pwq from @target.
2475 * CONTEXT:
2476 * spin_lock_irq(pool->lock).
2478 static void insert_wq_barrier(struct pool_workqueue *pwq,
2479 struct wq_barrier *barr,
2480 struct work_struct *target, struct worker *worker)
2482 struct list_head *head;
2483 unsigned int linked = 0;
2486 * debugobject calls are safe here even with pool->lock locked
2487 * as we know for sure that this will not trigger any of the
2488 * checks and call back into the fixup functions where we
2489 * might deadlock.
2491 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2492 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2494 init_completion_map(&barr->done, &target->lockdep_map);
2496 barr->task = current;
2499 * If @target is currently being executed, schedule the
2500 * barrier to the worker; otherwise, put it after @target.
2502 if (worker)
2503 head = worker->scheduled.next;
2504 else {
2505 unsigned long *bits = work_data_bits(target);
2507 head = target->entry.next;
2508 /* there can already be other linked works, inherit and set */
2509 linked = *bits & WORK_STRUCT_LINKED;
2510 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2513 debug_work_activate(&barr->work);
2514 insert_work(pwq, &barr->work, head,
2515 work_color_to_flags(WORK_NO_COLOR) | linked);
2519 * flush_workqueue_prep_pwqs - prepare pwqs for workqueue flushing
2520 * @wq: workqueue being flushed
2521 * @flush_color: new flush color, < 0 for no-op
2522 * @work_color: new work color, < 0 for no-op
2524 * Prepare pwqs for workqueue flushing.
2526 * If @flush_color is non-negative, flush_color on all pwqs should be
2527 * -1. If no pwq has in-flight commands at the specified color, all
2528 * pwq->flush_color's stay at -1 and %false is returned. If any pwq
2529 * has in flight commands, its pwq->flush_color is set to
2530 * @flush_color, @wq->nr_pwqs_to_flush is updated accordingly, pwq
2531 * wakeup logic is armed and %true is returned.
2533 * The caller should have initialized @wq->first_flusher prior to
2534 * calling this function with non-negative @flush_color. If
2535 * @flush_color is negative, no flush color update is done and %false
2536 * is returned.
2538 * If @work_color is non-negative, all pwqs should have the same
2539 * work_color which is previous to @work_color and all will be
2540 * advanced to @work_color.
2542 * CONTEXT:
2543 * mutex_lock(wq->mutex).
2545 * Return:
2546 * %true if @flush_color >= 0 and there's something to flush. %false
2547 * otherwise.
2549 static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq,
2550 int flush_color, int work_color)
2552 bool wait = false;
2553 struct pool_workqueue *pwq;
2555 if (flush_color >= 0) {
2556 WARN_ON_ONCE(atomic_read(&wq->nr_pwqs_to_flush));
2557 atomic_set(&wq->nr_pwqs_to_flush, 1);
2560 for_each_pwq(pwq, wq) {
2561 struct worker_pool *pool = pwq->pool;
2563 spin_lock_irq(&pool->lock);
2565 if (flush_color >= 0) {
2566 WARN_ON_ONCE(pwq->flush_color != -1);
2568 if (pwq->nr_in_flight[flush_color]) {
2569 pwq->flush_color = flush_color;
2570 atomic_inc(&wq->nr_pwqs_to_flush);
2571 wait = true;
2575 if (work_color >= 0) {
2576 WARN_ON_ONCE(work_color != work_next_color(pwq->work_color));
2577 pwq->work_color = work_color;
2580 spin_unlock_irq(&pool->lock);
2583 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_pwqs_to_flush))
2584 complete(&wq->first_flusher->done);
2586 return wait;
2590 * flush_workqueue - ensure that any scheduled work has run to completion.
2591 * @wq: workqueue to flush
2593 * This function sleeps until all work items which were queued on entry
2594 * have finished execution, but it is not livelocked by new incoming ones.
2596 void flush_workqueue(struct workqueue_struct *wq)
2598 struct wq_flusher this_flusher = {
2599 .list = LIST_HEAD_INIT(this_flusher.list),
2600 .flush_color = -1,
2601 .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
2603 int next_color;
2605 if (WARN_ON(!wq_online))
2606 return;
2608 mutex_lock(&wq->mutex);
2611 * Start-to-wait phase
2613 next_color = work_next_color(wq->work_color);
2615 if (next_color != wq->flush_color) {
2617 * Color space is not full. The current work_color
2618 * becomes our flush_color and work_color is advanced
2619 * by one.
2621 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow));
2622 this_flusher.flush_color = wq->work_color;
2623 wq->work_color = next_color;
2625 if (!wq->first_flusher) {
2626 /* no flush in progress, become the first flusher */
2627 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2629 wq->first_flusher = &this_flusher;
2631 if (!flush_workqueue_prep_pwqs(wq, wq->flush_color,
2632 wq->work_color)) {
2633 /* nothing to flush, done */
2634 wq->flush_color = next_color;
2635 wq->first_flusher = NULL;
2636 goto out_unlock;
2638 } else {
2639 /* wait in queue */
2640 WARN_ON_ONCE(wq->flush_color == this_flusher.flush_color);
2641 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2642 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2644 } else {
2646 * Oops, color space is full, wait on overflow queue.
2647 * The next flush completion will assign us
2648 * flush_color and transfer to flusher_queue.
2650 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2653 check_flush_dependency(wq, NULL);
2655 mutex_unlock(&wq->mutex);
2657 wait_for_completion(&this_flusher.done);
2660 * Wake-up-and-cascade phase
2662 * First flushers are responsible for cascading flushes and
2663 * handling overflow. Non-first flushers can simply return.
2665 if (wq->first_flusher != &this_flusher)
2666 return;
2668 mutex_lock(&wq->mutex);
2670 /* we might have raced, check again with mutex held */
2671 if (wq->first_flusher != &this_flusher)
2672 goto out_unlock;
2674 wq->first_flusher = NULL;
2676 WARN_ON_ONCE(!list_empty(&this_flusher.list));
2677 WARN_ON_ONCE(wq->flush_color != this_flusher.flush_color);
2679 while (true) {
2680 struct wq_flusher *next, *tmp;
2682 /* complete all the flushers sharing the current flush color */
2683 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2684 if (next->flush_color != wq->flush_color)
2685 break;
2686 list_del_init(&next->list);
2687 complete(&next->done);
2690 WARN_ON_ONCE(!list_empty(&wq->flusher_overflow) &&
2691 wq->flush_color != work_next_color(wq->work_color));
2693 /* this flush_color is finished, advance by one */
2694 wq->flush_color = work_next_color(wq->flush_color);
2696 /* one color has been freed, handle overflow queue */
2697 if (!list_empty(&wq->flusher_overflow)) {
2699 * Assign the same color to all overflowed
2700 * flushers, advance work_color and append to
2701 * flusher_queue. This is the start-to-wait
2702 * phase for these overflowed flushers.
2704 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2705 tmp->flush_color = wq->work_color;
2707 wq->work_color = work_next_color(wq->work_color);
2709 list_splice_tail_init(&wq->flusher_overflow,
2710 &wq->flusher_queue);
2711 flush_workqueue_prep_pwqs(wq, -1, wq->work_color);
2714 if (list_empty(&wq->flusher_queue)) {
2715 WARN_ON_ONCE(wq->flush_color != wq->work_color);
2716 break;
2720 * Need to flush more colors. Make the next flusher
2721 * the new first flusher and arm pwqs.
2723 WARN_ON_ONCE(wq->flush_color == wq->work_color);
2724 WARN_ON_ONCE(wq->flush_color != next->flush_color);
2726 list_del_init(&next->list);
2727 wq->first_flusher = next;
2729 if (flush_workqueue_prep_pwqs(wq, wq->flush_color, -1))
2730 break;
2733 * Meh... this color is already done, clear first
2734 * flusher and repeat cascading.
2736 wq->first_flusher = NULL;
2739 out_unlock:
2740 mutex_unlock(&wq->mutex);
2742 EXPORT_SYMBOL(flush_workqueue);
2745 * drain_workqueue - drain a workqueue
2746 * @wq: workqueue to drain
2748 * Wait until the workqueue becomes empty. While draining is in progress,
2749 * only chain queueing is allowed. IOW, only currently pending or running
2750 * work items on @wq can queue further work items on it. @wq is flushed
2751 * repeatedly until it becomes empty. The number of flushing is determined
2752 * by the depth of chaining and should be relatively short. Whine if it
2753 * takes too long.
2755 void drain_workqueue(struct workqueue_struct *wq)
2757 unsigned int flush_cnt = 0;
2758 struct pool_workqueue *pwq;
2761 * __queue_work() needs to test whether there are drainers, is much
2762 * hotter than drain_workqueue() and already looks at @wq->flags.
2763 * Use __WQ_DRAINING so that queue doesn't have to check nr_drainers.
2765 mutex_lock(&wq->mutex);
2766 if (!wq->nr_drainers++)
2767 wq->flags |= __WQ_DRAINING;
2768 mutex_unlock(&wq->mutex);
2769 reflush:
2770 flush_workqueue(wq);
2772 mutex_lock(&wq->mutex);
2774 for_each_pwq(pwq, wq) {
2775 bool drained;
2777 spin_lock_irq(&pwq->pool->lock);
2778 drained = !pwq->nr_active && list_empty(&pwq->delayed_works);
2779 spin_unlock_irq(&pwq->pool->lock);
2781 if (drained)
2782 continue;
2784 if (++flush_cnt == 10 ||
2785 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2786 pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n",
2787 wq->name, flush_cnt);
2789 mutex_unlock(&wq->mutex);
2790 goto reflush;
2793 if (!--wq->nr_drainers)
2794 wq->flags &= ~__WQ_DRAINING;
2795 mutex_unlock(&wq->mutex);
2797 EXPORT_SYMBOL_GPL(drain_workqueue);
2799 static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr)
2801 struct worker *worker = NULL;
2802 struct worker_pool *pool;
2803 struct pool_workqueue *pwq;
2805 might_sleep();
2807 local_irq_disable();
2808 pool = get_work_pool(work);
2809 if (!pool) {
2810 local_irq_enable();
2811 return false;
2814 spin_lock(&pool->lock);
2815 /* see the comment in try_to_grab_pending() with the same code */
2816 pwq = get_work_pwq(work);
2817 if (pwq) {
2818 if (unlikely(pwq->pool != pool))
2819 goto already_gone;
2820 } else {
2821 worker = find_worker_executing_work(pool, work);
2822 if (!worker)
2823 goto already_gone;
2824 pwq = worker->current_pwq;
2827 check_flush_dependency(pwq->wq, work);
2829 insert_wq_barrier(pwq, barr, work, worker);
2830 spin_unlock_irq(&pool->lock);
2833 * Force a lock recursion deadlock when using flush_work() inside a
2834 * single-threaded or rescuer equipped workqueue.
2836 * For single threaded workqueues the deadlock happens when the work
2837 * is after the work issuing the flush_work(). For rescuer equipped
2838 * workqueues the deadlock happens when the rescuer stalls, blocking
2839 * forward progress.
2841 if (pwq->wq->saved_max_active == 1 || pwq->wq->rescuer) {
2842 lock_map_acquire(&pwq->wq->lockdep_map);
2843 lock_map_release(&pwq->wq->lockdep_map);
2846 return true;
2847 already_gone:
2848 spin_unlock_irq(&pool->lock);
2849 return false;
2853 * flush_work - wait for a work to finish executing the last queueing instance
2854 * @work: the work to flush
2856 * Wait until @work has finished execution. @work is guaranteed to be idle
2857 * on return if it hasn't been requeued since flush started.
2859 * Return:
2860 * %true if flush_work() waited for the work to finish execution,
2861 * %false if it was already idle.
2863 bool flush_work(struct work_struct *work)
2865 struct wq_barrier barr;
2867 if (WARN_ON(!wq_online))
2868 return false;
2870 if (start_flush_work(work, &barr)) {
2871 wait_for_completion(&barr.done);
2872 destroy_work_on_stack(&barr.work);
2873 return true;
2874 } else {
2875 return false;
2878 EXPORT_SYMBOL_GPL(flush_work);
2880 struct cwt_wait {
2881 wait_queue_entry_t wait;
2882 struct work_struct *work;
2885 static int cwt_wakefn(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
2887 struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
2889 if (cwait->work != key)
2890 return 0;
2891 return autoremove_wake_function(wait, mode, sync, key);
2894 static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
2896 static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
2897 unsigned long flags;
2898 int ret;
2900 do {
2901 ret = try_to_grab_pending(work, is_dwork, &flags);
2903 * If someone else is already canceling, wait for it to
2904 * finish. flush_work() doesn't work for PREEMPT_NONE
2905 * because we may get scheduled between @work's completion
2906 * and the other canceling task resuming and clearing
2907 * CANCELING - flush_work() will return false immediately
2908 * as @work is no longer busy, try_to_grab_pending() will
2909 * return -ENOENT as @work is still being canceled and the
2910 * other canceling task won't be able to clear CANCELING as
2911 * we're hogging the CPU.
2913 * Let's wait for completion using a waitqueue. As this
2914 * may lead to the thundering herd problem, use a custom
2915 * wake function which matches @work along with exclusive
2916 * wait and wakeup.
2918 if (unlikely(ret == -ENOENT)) {
2919 struct cwt_wait cwait;
2921 init_wait(&cwait.wait);
2922 cwait.wait.func = cwt_wakefn;
2923 cwait.work = work;
2925 prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
2926 TASK_UNINTERRUPTIBLE);
2927 if (work_is_canceling(work))
2928 schedule();
2929 finish_wait(&cancel_waitq, &cwait.wait);
2931 } while (unlikely(ret < 0));
2933 /* tell other tasks trying to grab @work to back off */
2934 mark_work_canceling(work);
2935 local_irq_restore(flags);
2938 * This allows canceling during early boot. We know that @work
2939 * isn't executing.
2941 if (wq_online)
2942 flush_work(work);
2944 clear_work_data(work);
2947 * Paired with prepare_to_wait() above so that either
2948 * waitqueue_active() is visible here or !work_is_canceling() is
2949 * visible there.
2951 smp_mb();
2952 if (waitqueue_active(&cancel_waitq))
2953 __wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
2955 return ret;
2959 * cancel_work_sync - cancel a work and wait for it to finish
2960 * @work: the work to cancel
2962 * Cancel @work and wait for its execution to finish. This function
2963 * can be used even if the work re-queues itself or migrates to
2964 * another workqueue. On return from this function, @work is
2965 * guaranteed to be not pending or executing on any CPU.
2967 * cancel_work_sync(&delayed_work->work) must not be used for
2968 * delayed_work's. Use cancel_delayed_work_sync() instead.
2970 * The caller must ensure that the workqueue on which @work was last
2971 * queued can't be destroyed before this function returns.
2973 * Return:
2974 * %true if @work was pending, %false otherwise.
2976 bool cancel_work_sync(struct work_struct *work)
2978 return __cancel_work_timer(work, false);
2980 EXPORT_SYMBOL_GPL(cancel_work_sync);
2983 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2984 * @dwork: the delayed work to flush
2986 * Delayed timer is cancelled and the pending work is queued for
2987 * immediate execution. Like flush_work(), this function only
2988 * considers the last queueing instance of @dwork.
2990 * Return:
2991 * %true if flush_work() waited for the work to finish execution,
2992 * %false if it was already idle.
2994 bool flush_delayed_work(struct delayed_work *dwork)
2996 local_irq_disable();
2997 if (del_timer_sync(&dwork->timer))
2998 __queue_work(dwork->cpu, dwork->wq, &dwork->work);
2999 local_irq_enable();
3000 return flush_work(&dwork->work);
3002 EXPORT_SYMBOL(flush_delayed_work);
3004 static bool __cancel_work(struct work_struct *work, bool is_dwork)
3006 unsigned long flags;
3007 int ret;
3009 do {
3010 ret = try_to_grab_pending(work, is_dwork, &flags);
3011 } while (unlikely(ret == -EAGAIN));
3013 if (unlikely(ret < 0))
3014 return false;
3016 set_work_pool_and_clear_pending(work, get_work_pool_id(work));
3017 local_irq_restore(flags);
3018 return ret;
3022 * See cancel_delayed_work()
3024 bool cancel_work(struct work_struct *work)
3026 return __cancel_work(work, false);
3030 * cancel_delayed_work - cancel a delayed work
3031 * @dwork: delayed_work to cancel
3033 * Kill off a pending delayed_work.
3035 * Return: %true if @dwork was pending and canceled; %false if it wasn't
3036 * pending.
3038 * Note:
3039 * The work callback function may still be running on return, unless
3040 * it returns %true and the work doesn't re-arm itself. Explicitly flush or
3041 * use cancel_delayed_work_sync() to wait on it.
3043 * This function is safe to call from any context including IRQ handler.
3045 bool cancel_delayed_work(struct delayed_work *dwork)
3047 return __cancel_work(&dwork->work, true);
3049 EXPORT_SYMBOL(cancel_delayed_work);
3052 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
3053 * @dwork: the delayed work cancel
3055 * This is cancel_work_sync() for delayed works.
3057 * Return:
3058 * %true if @dwork was pending, %false otherwise.
3060 bool cancel_delayed_work_sync(struct delayed_work *dwork)
3062 return __cancel_work_timer(&dwork->work, true);
3064 EXPORT_SYMBOL(cancel_delayed_work_sync);
3067 * schedule_on_each_cpu - execute a function synchronously on each online CPU
3068 * @func: the function to call
3070 * schedule_on_each_cpu() executes @func on each online CPU using the
3071 * system workqueue and blocks until all CPUs have completed.
3072 * schedule_on_each_cpu() is very slow.
3074 * Return:
3075 * 0 on success, -errno on failure.
3077 int schedule_on_each_cpu(work_func_t func)
3079 int cpu;
3080 struct work_struct __percpu *works;
3082 works = alloc_percpu(struct work_struct);
3083 if (!works)
3084 return -ENOMEM;
3086 get_online_cpus();
3088 for_each_online_cpu(cpu) {
3089 struct work_struct *work = per_cpu_ptr(works, cpu);
3091 INIT_WORK(work, func);
3092 schedule_work_on(cpu, work);
3095 for_each_online_cpu(cpu)
3096 flush_work(per_cpu_ptr(works, cpu));
3098 put_online_cpus();
3099 free_percpu(works);
3100 return 0;
3104 * execute_in_process_context - reliably execute the routine with user context
3105 * @fn: the function to execute
3106 * @ew: guaranteed storage for the execute work structure (must
3107 * be available when the work executes)
3109 * Executes the function immediately if process context is available,
3110 * otherwise schedules the function for delayed execution.
3112 * Return: 0 - function was executed
3113 * 1 - function was scheduled for execution
3115 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
3117 if (!in_interrupt()) {
3118 fn(&ew->work);
3119 return 0;
3122 INIT_WORK(&ew->work, fn);
3123 schedule_work(&ew->work);
3125 return 1;
3127 EXPORT_SYMBOL_GPL(execute_in_process_context);
3130 * free_workqueue_attrs - free a workqueue_attrs
3131 * @attrs: workqueue_attrs to free
3133 * Undo alloc_workqueue_attrs().
3135 void free_workqueue_attrs(struct workqueue_attrs *attrs)
3137 if (attrs) {
3138 free_cpumask_var(attrs->cpumask);
3139 kfree(attrs);
3144 * alloc_workqueue_attrs - allocate a workqueue_attrs
3145 * @gfp_mask: allocation mask to use
3147 * Allocate a new workqueue_attrs, initialize with default settings and
3148 * return it.
3150 * Return: The allocated new workqueue_attr on success. %NULL on failure.
3152 struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask)
3154 struct workqueue_attrs *attrs;
3156 attrs = kzalloc(sizeof(*attrs), gfp_mask);
3157 if (!attrs)
3158 goto fail;
3159 if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask))
3160 goto fail;
3162 cpumask_copy(attrs->cpumask, cpu_possible_mask);
3163 return attrs;
3164 fail:
3165 free_workqueue_attrs(attrs);
3166 return NULL;
3169 static void copy_workqueue_attrs(struct workqueue_attrs *to,
3170 const struct workqueue_attrs *from)
3172 to->nice = from->nice;
3173 cpumask_copy(to->cpumask, from->cpumask);
3175 * Unlike hash and equality test, this function doesn't ignore
3176 * ->no_numa as it is used for both pool and wq attrs. Instead,
3177 * get_unbound_pool() explicitly clears ->no_numa after copying.
3179 to->no_numa = from->no_numa;
3182 /* hash value of the content of @attr */
3183 static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
3185 u32 hash = 0;
3187 hash = jhash_1word(attrs->nice, hash);
3188 hash = jhash(cpumask_bits(attrs->cpumask),
3189 BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
3190 return hash;
3193 /* content equality test */
3194 static bool wqattrs_equal(const struct workqueue_attrs *a,
3195 const struct workqueue_attrs *b)
3197 if (a->nice != b->nice)
3198 return false;
3199 if (!cpumask_equal(a->cpumask, b->cpumask))
3200 return false;
3201 return true;
3205 * init_worker_pool - initialize a newly zalloc'd worker_pool
3206 * @pool: worker_pool to initialize
3208 * Initialize a newly zalloc'd @pool. It also allocates @pool->attrs.
3210 * Return: 0 on success, -errno on failure. Even on failure, all fields
3211 * inside @pool proper are initialized and put_unbound_pool() can be called
3212 * on @pool safely to release it.
3214 static int init_worker_pool(struct worker_pool *pool)
3216 spin_lock_init(&pool->lock);
3217 pool->id = -1;
3218 pool->cpu = -1;
3219 pool->node = NUMA_NO_NODE;
3220 pool->flags |= POOL_DISASSOCIATED;
3221 pool->watchdog_ts = jiffies;
3222 INIT_LIST_HEAD(&pool->worklist);
3223 INIT_LIST_HEAD(&pool->idle_list);
3224 hash_init(pool->busy_hash);
3226 timer_setup(&pool->idle_timer, idle_worker_timeout, TIMER_DEFERRABLE);
3228 timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
3230 mutex_init(&pool->attach_mutex);
3231 INIT_LIST_HEAD(&pool->workers);
3233 ida_init(&pool->worker_ida);
3234 INIT_HLIST_NODE(&pool->hash_node);
3235 pool->refcnt = 1;
3237 /* shouldn't fail above this point */
3238 pool->attrs = alloc_workqueue_attrs(GFP_KERNEL);
3239 if (!pool->attrs)
3240 return -ENOMEM;
3241 return 0;
3244 static void rcu_free_wq(struct rcu_head *rcu)
3246 struct workqueue_struct *wq =
3247 container_of(rcu, struct workqueue_struct, rcu);
3249 if (!(wq->flags & WQ_UNBOUND))
3250 free_percpu(wq->cpu_pwqs);
3251 else
3252 free_workqueue_attrs(wq->unbound_attrs);
3254 kfree(wq->rescuer);
3255 kfree(wq);
3258 static void rcu_free_pool(struct rcu_head *rcu)
3260 struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu);
3262 ida_destroy(&pool->worker_ida);
3263 free_workqueue_attrs(pool->attrs);
3264 kfree(pool);
3268 * put_unbound_pool - put a worker_pool
3269 * @pool: worker_pool to put
3271 * Put @pool. If its refcnt reaches zero, it gets destroyed in sched-RCU
3272 * safe manner. get_unbound_pool() calls this function on its failure path
3273 * and this function should be able to release pools which went through,
3274 * successfully or not, init_worker_pool().
3276 * Should be called with wq_pool_mutex held.
3278 static void put_unbound_pool(struct worker_pool *pool)
3280 DECLARE_COMPLETION_ONSTACK(detach_completion);
3281 struct worker *worker;
3283 lockdep_assert_held(&wq_pool_mutex);
3285 if (--pool->refcnt)
3286 return;
3288 /* sanity checks */
3289 if (WARN_ON(!(pool->cpu < 0)) ||
3290 WARN_ON(!list_empty(&pool->worklist)))
3291 return;
3293 /* release id and unhash */
3294 if (pool->id >= 0)
3295 idr_remove(&worker_pool_idr, pool->id);
3296 hash_del(&pool->hash_node);
3299 * Become the manager and destroy all workers. This prevents
3300 * @pool's workers from blocking on attach_mutex. We're the last
3301 * manager and @pool gets freed with the flag set.
3303 spin_lock_irq(&pool->lock);
3304 wait_event_lock_irq(wq_manager_wait,
3305 !(pool->flags & POOL_MANAGER_ACTIVE), pool->lock);
3306 pool->flags |= POOL_MANAGER_ACTIVE;
3308 while ((worker = first_idle_worker(pool)))
3309 destroy_worker(worker);
3310 WARN_ON(pool->nr_workers || pool->nr_idle);
3311 spin_unlock_irq(&pool->lock);
3313 mutex_lock(&pool->attach_mutex);
3314 if (!list_empty(&pool->workers))
3315 pool->detach_completion = &detach_completion;
3316 mutex_unlock(&pool->attach_mutex);
3318 if (pool->detach_completion)
3319 wait_for_completion(pool->detach_completion);
3321 /* shut down the timers */
3322 del_timer_sync(&pool->idle_timer);
3323 del_timer_sync(&pool->mayday_timer);
3325 /* sched-RCU protected to allow dereferences from get_work_pool() */
3326 call_rcu_sched(&pool->rcu, rcu_free_pool);
3330 * get_unbound_pool - get a worker_pool with the specified attributes
3331 * @attrs: the attributes of the worker_pool to get
3333 * Obtain a worker_pool which has the same attributes as @attrs, bump the
3334 * reference count and return it. If there already is a matching
3335 * worker_pool, it will be used; otherwise, this function attempts to
3336 * create a new one.
3338 * Should be called with wq_pool_mutex held.
3340 * Return: On success, a worker_pool with the same attributes as @attrs.
3341 * On failure, %NULL.
3343 static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
3345 u32 hash = wqattrs_hash(attrs);
3346 struct worker_pool *pool;
3347 int node;
3348 int target_node = NUMA_NO_NODE;
3350 lockdep_assert_held(&wq_pool_mutex);
3352 /* do we already have a matching pool? */
3353 hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
3354 if (wqattrs_equal(pool->attrs, attrs)) {
3355 pool->refcnt++;
3356 return pool;
3360 /* if cpumask is contained inside a NUMA node, we belong to that node */
3361 if (wq_numa_enabled) {
3362 for_each_node(node) {
3363 if (cpumask_subset(attrs->cpumask,
3364 wq_numa_possible_cpumask[node])) {
3365 target_node = node;
3366 break;
3371 /* nope, create a new one */
3372 pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, target_node);
3373 if (!pool || init_worker_pool(pool) < 0)
3374 goto fail;
3376 lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */
3377 copy_workqueue_attrs(pool->attrs, attrs);
3378 pool->node = target_node;
3381 * no_numa isn't a worker_pool attribute, always clear it. See
3382 * 'struct workqueue_attrs' comments for detail.
3384 pool->attrs->no_numa = false;
3386 if (worker_pool_assign_id(pool) < 0)
3387 goto fail;
3389 /* create and start the initial worker */
3390 if (wq_online && !create_worker(pool))
3391 goto fail;
3393 /* install */
3394 hash_add(unbound_pool_hash, &pool->hash_node, hash);
3396 return pool;
3397 fail:
3398 if (pool)
3399 put_unbound_pool(pool);
3400 return NULL;
3403 static void rcu_free_pwq(struct rcu_head *rcu)
3405 kmem_cache_free(pwq_cache,
3406 container_of(rcu, struct pool_workqueue, rcu));
3410 * Scheduled on system_wq by put_pwq() when an unbound pwq hits zero refcnt
3411 * and needs to be destroyed.
3413 static void pwq_unbound_release_workfn(struct work_struct *work)
3415 struct pool_workqueue *pwq = container_of(work, struct pool_workqueue,
3416 unbound_release_work);
3417 struct workqueue_struct *wq = pwq->wq;
3418 struct worker_pool *pool = pwq->pool;
3419 bool is_last;
3421 if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND)))
3422 return;
3424 mutex_lock(&wq->mutex);
3425 list_del_rcu(&pwq->pwqs_node);
3426 is_last = list_empty(&wq->pwqs);
3427 mutex_unlock(&wq->mutex);
3429 mutex_lock(&wq_pool_mutex);
3430 put_unbound_pool(pool);
3431 mutex_unlock(&wq_pool_mutex);
3433 call_rcu_sched(&pwq->rcu, rcu_free_pwq);
3436 * If we're the last pwq going away, @wq is already dead and no one
3437 * is gonna access it anymore. Schedule RCU free.
3439 if (is_last)
3440 call_rcu_sched(&wq->rcu, rcu_free_wq);
3444 * pwq_adjust_max_active - update a pwq's max_active to the current setting
3445 * @pwq: target pool_workqueue
3447 * If @pwq isn't freezing, set @pwq->max_active to the associated
3448 * workqueue's saved_max_active and activate delayed work items
3449 * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
3451 static void pwq_adjust_max_active(struct pool_workqueue *pwq)
3453 struct workqueue_struct *wq = pwq->wq;
3454 bool freezable = wq->flags & WQ_FREEZABLE;
3455 unsigned long flags;
3457 /* for @wq->saved_max_active */
3458 lockdep_assert_held(&wq->mutex);
3460 /* fast exit for non-freezable wqs */
3461 if (!freezable && pwq->max_active == wq->saved_max_active)
3462 return;
3464 /* this function can be called during early boot w/ irq disabled */
3465 spin_lock_irqsave(&pwq->pool->lock, flags);
3468 * During [un]freezing, the caller is responsible for ensuring that
3469 * this function is called at least once after @workqueue_freezing
3470 * is updated and visible.
3472 if (!freezable || !workqueue_freezing) {
3473 pwq->max_active = wq->saved_max_active;
3475 while (!list_empty(&pwq->delayed_works) &&
3476 pwq->nr_active < pwq->max_active)
3477 pwq_activate_first_delayed(pwq);
3480 * Need to kick a worker after thawed or an unbound wq's
3481 * max_active is bumped. It's a slow path. Do it always.
3483 wake_up_worker(pwq->pool);
3484 } else {
3485 pwq->max_active = 0;
3488 spin_unlock_irqrestore(&pwq->pool->lock, flags);
3491 /* initialize newly alloced @pwq which is associated with @wq and @pool */
3492 static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
3493 struct worker_pool *pool)
3495 BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
3497 memset(pwq, 0, sizeof(*pwq));
3499 pwq->pool = pool;
3500 pwq->wq = wq;
3501 pwq->flush_color = -1;
3502 pwq->refcnt = 1;
3503 INIT_LIST_HEAD(&pwq->delayed_works);
3504 INIT_LIST_HEAD(&pwq->pwqs_node);
3505 INIT_LIST_HEAD(&pwq->mayday_node);
3506 INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
3509 /* sync @pwq with the current state of its associated wq and link it */
3510 static void link_pwq(struct pool_workqueue *pwq)
3512 struct workqueue_struct *wq = pwq->wq;
3514 lockdep_assert_held(&wq->mutex);
3516 /* may be called multiple times, ignore if already linked */
3517 if (!list_empty(&pwq->pwqs_node))
3518 return;
3520 /* set the matching work_color */
3521 pwq->work_color = wq->work_color;
3523 /* sync max_active to the current setting */
3524 pwq_adjust_max_active(pwq);
3526 /* link in @pwq */
3527 list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
3530 /* obtain a pool matching @attr and create a pwq associating the pool and @wq */
3531 static struct pool_workqueue *alloc_unbound_pwq(struct workqueue_struct *wq,
3532 const struct workqueue_attrs *attrs)
3534 struct worker_pool *pool;
3535 struct pool_workqueue *pwq;
3537 lockdep_assert_held(&wq_pool_mutex);
3539 pool = get_unbound_pool(attrs);
3540 if (!pool)
3541 return NULL;
3543 pwq = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, pool->node);
3544 if (!pwq) {
3545 put_unbound_pool(pool);
3546 return NULL;
3549 init_pwq(pwq, wq, pool);
3550 return pwq;
3554 * wq_calc_node_cpumask - calculate a wq_attrs' cpumask for the specified node
3555 * @attrs: the wq_attrs of the default pwq of the target workqueue
3556 * @node: the target NUMA node
3557 * @cpu_going_down: if >= 0, the CPU to consider as offline
3558 * @cpumask: outarg, the resulting cpumask
3560 * Calculate the cpumask a workqueue with @attrs should use on @node. If
3561 * @cpu_going_down is >= 0, that cpu is considered offline during
3562 * calculation. The result is stored in @cpumask.
3564 * If NUMA affinity is not enabled, @attrs->cpumask is always used. If
3565 * enabled and @node has online CPUs requested by @attrs, the returned
3566 * cpumask is the intersection of the possible CPUs of @node and
3567 * @attrs->cpumask.
3569 * The caller is responsible for ensuring that the cpumask of @node stays
3570 * stable.
3572 * Return: %true if the resulting @cpumask is different from @attrs->cpumask,
3573 * %false if equal.
3575 static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node,
3576 int cpu_going_down, cpumask_t *cpumask)
3578 if (!wq_numa_enabled || attrs->no_numa)
3579 goto use_dfl;
3581 /* does @node have any online CPUs @attrs wants? */
3582 cpumask_and(cpumask, cpumask_of_node(node), attrs->cpumask);
3583 if (cpu_going_down >= 0)
3584 cpumask_clear_cpu(cpu_going_down, cpumask);
3586 if (cpumask_empty(cpumask))
3587 goto use_dfl;
3589 /* yeap, return possible CPUs in @node that @attrs wants */
3590 cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);
3592 if (cpumask_empty(cpumask)) {
3593 pr_warn_once("WARNING: workqueue cpumask: online intersect > "
3594 "possible intersect\n");
3595 return false;
3598 return !cpumask_equal(cpumask, attrs->cpumask);
3600 use_dfl:
3601 cpumask_copy(cpumask, attrs->cpumask);
3602 return false;
3605 /* install @pwq into @wq's numa_pwq_tbl[] for @node and return the old pwq */
3606 static struct pool_workqueue *numa_pwq_tbl_install(struct workqueue_struct *wq,
3607 int node,
3608 struct pool_workqueue *pwq)
3610 struct pool_workqueue *old_pwq;
3612 lockdep_assert_held(&wq_pool_mutex);
3613 lockdep_assert_held(&wq->mutex);
3615 /* link_pwq() can handle duplicate calls */
3616 link_pwq(pwq);
3618 old_pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
3619 rcu_assign_pointer(wq->numa_pwq_tbl[node], pwq);
3620 return old_pwq;
3623 /* context to store the prepared attrs & pwqs before applying */
3624 struct apply_wqattrs_ctx {
3625 struct workqueue_struct *wq; /* target workqueue */
3626 struct workqueue_attrs *attrs; /* attrs to apply */
3627 struct list_head list; /* queued for batching commit */
3628 struct pool_workqueue *dfl_pwq;
3629 struct pool_workqueue *pwq_tbl[];
3632 /* free the resources after success or abort */
3633 static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx)
3635 if (ctx) {
3636 int node;
3638 for_each_node(node)
3639 put_pwq_unlocked(ctx->pwq_tbl[node]);
3640 put_pwq_unlocked(ctx->dfl_pwq);
3642 free_workqueue_attrs(ctx->attrs);
3644 kfree(ctx);
3648 /* allocate the attrs and pwqs for later installation */
3649 static struct apply_wqattrs_ctx *
3650 apply_wqattrs_prepare(struct workqueue_struct *wq,
3651 const struct workqueue_attrs *attrs)
3653 struct apply_wqattrs_ctx *ctx;
3654 struct workqueue_attrs *new_attrs, *tmp_attrs;
3655 int node;
3657 lockdep_assert_held(&wq_pool_mutex);
3659 ctx = kzalloc(sizeof(*ctx) + nr_node_ids * sizeof(ctx->pwq_tbl[0]),
3660 GFP_KERNEL);
3662 new_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3663 tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL);
3664 if (!ctx || !new_attrs || !tmp_attrs)
3665 goto out_free;
3668 * Calculate the attrs of the default pwq.
3669 * If the user configured cpumask doesn't overlap with the
3670 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.
3672 copy_workqueue_attrs(new_attrs, attrs);
3673 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);
3674 if (unlikely(cpumask_empty(new_attrs->cpumask)))
3675 cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);
3678 * We may create multiple pwqs with differing cpumasks. Make a
3679 * copy of @new_attrs which will be modified and used to obtain
3680 * pools.
3682 copy_workqueue_attrs(tmp_attrs, new_attrs);
3685 * If something goes wrong during CPU up/down, we'll fall back to
3686 * the default pwq covering whole @attrs->cpumask. Always create
3687 * it even if we don't use it immediately.
3689 ctx->dfl_pwq = alloc_unbound_pwq(wq, new_attrs);
3690 if (!ctx->dfl_pwq)
3691 goto out_free;
3693 for_each_node(node) {
3694 if (wq_calc_node_cpumask(new_attrs, node, -1, tmp_attrs->cpumask)) {
3695 ctx->pwq_tbl[node] = alloc_unbound_pwq(wq, tmp_attrs);
3696 if (!ctx->pwq_tbl[node])
3697 goto out_free;
3698 } else {
3699 ctx->dfl_pwq->refcnt++;
3700 ctx->pwq_tbl[node] = ctx->dfl_pwq;
3704 /* save the user configured attrs and sanitize it. */
3705 copy_workqueue_attrs(new_attrs, attrs);
3706 cpumask_and(new_attrs->cpumask, new_attrs->cpumask, cpu_possible_mask);
3707 ctx->attrs = new_attrs;
3709 ctx->wq = wq;
3710 free_workqueue_attrs(tmp_attrs);
3711 return ctx;
3713 out_free:
3714 free_workqueue_attrs(tmp_attrs);
3715 free_workqueue_attrs(new_attrs);
3716 apply_wqattrs_cleanup(ctx);
3717 return NULL;
3720 /* set attrs and install prepared pwqs, @ctx points to old pwqs on return */
3721 static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
3723 int node;
3725 /* all pwqs have been created successfully, let's install'em */
3726 mutex_lock(&ctx->wq->mutex);
3728 copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
3730 /* save the previous pwq and install the new one */
3731 for_each_node(node)
3732 ctx->pwq_tbl[node] = numa_pwq_tbl_install(ctx->wq, node,
3733 ctx->pwq_tbl[node]);
3735 /* @dfl_pwq might not have been used, ensure it's linked */
3736 link_pwq(ctx->dfl_pwq);
3737 swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
3739 mutex_unlock(&ctx->wq->mutex);
3742 static void apply_wqattrs_lock(void)
3744 /* CPUs should stay stable across pwq creations and installations */
3745 get_online_cpus();
3746 mutex_lock(&wq_pool_mutex);
3749 static void apply_wqattrs_unlock(void)
3751 mutex_unlock(&wq_pool_mutex);
3752 put_online_cpus();
3755 static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
3756 const struct workqueue_attrs *attrs)
3758 struct apply_wqattrs_ctx *ctx;
3760 /* only unbound workqueues can change attributes */
3761 if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
3762 return -EINVAL;
3764 /* creating multiple pwqs breaks ordering guarantee */
3765 if (!list_empty(&wq->pwqs)) {
3766 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
3767 return -EINVAL;
3769 wq->flags &= ~__WQ_ORDERED;
3772 ctx = apply_wqattrs_prepare(wq, attrs);
3773 if (!ctx)
3774 return -ENOMEM;
3776 /* the ctx has been prepared successfully, let's commit it */
3777 apply_wqattrs_commit(ctx);
3778 apply_wqattrs_cleanup(ctx);
3780 return 0;
3784 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
3785 * @wq: the target workqueue
3786 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()
3788 * Apply @attrs to an unbound workqueue @wq. Unless disabled, on NUMA
3789 * machines, this function maps a separate pwq to each NUMA node with
3790 * possibles CPUs in @attrs->cpumask so that work items are affine to the
3791 * NUMA node it was issued on. Older pwqs are released as in-flight work
3792 * items finish. Note that a work item which repeatedly requeues itself
3793 * back-to-back will stay on its current pwq.
3795 * Performs GFP_KERNEL allocations.
3797 * Return: 0 on success and -errno on failure.
3799 int apply_workqueue_attrs(struct workqueue_struct *wq,
3800 const struct workqueue_attrs *attrs)
3802 int ret;
3804 apply_wqattrs_lock();
3805 ret = apply_workqueue_attrs_locked(wq, attrs);
3806 apply_wqattrs_unlock();
3808 return ret;
3810 EXPORT_SYMBOL_GPL(apply_workqueue_attrs);
3813 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug
3814 * @wq: the target workqueue
3815 * @cpu: the CPU coming up or going down
3816 * @online: whether @cpu is coming up or going down
3818 * This function is to be called from %CPU_DOWN_PREPARE, %CPU_ONLINE and
3819 * %CPU_DOWN_FAILED. @cpu is being hot[un]plugged, update NUMA affinity of
3820 * @wq accordingly.
3822 * If NUMA affinity can't be adjusted due to memory allocation failure, it
3823 * falls back to @wq->dfl_pwq which may not be optimal but is always
3824 * correct.
3826 * Note that when the last allowed CPU of a NUMA node goes offline for a
3827 * workqueue with a cpumask spanning multiple nodes, the workers which were
3828 * already executing the work items for the workqueue will lose their CPU
3829 * affinity and may execute on any CPU. This is similar to how per-cpu
3830 * workqueues behave on CPU_DOWN. If a workqueue user wants strict
3831 * affinity, it's the user's responsibility to flush the work item from
3832 * CPU_DOWN_PREPARE.
3834 static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu,
3835 bool online)
3837 int node = cpu_to_node(cpu);
3838 int cpu_off = online ? -1 : cpu;
3839 struct pool_workqueue *old_pwq = NULL, *pwq;
3840 struct workqueue_attrs *target_attrs;
3841 cpumask_t *cpumask;
3843 lockdep_assert_held(&wq_pool_mutex);
3845 if (!wq_numa_enabled || !(wq->flags & WQ_UNBOUND) ||
3846 wq->unbound_attrs->no_numa)
3847 return;
3850 * We don't wanna alloc/free wq_attrs for each wq for each CPU.
3851 * Let's use a preallocated one. The following buf is protected by
3852 * CPU hotplug exclusion.
3854 target_attrs = wq_update_unbound_numa_attrs_buf;
3855 cpumask = target_attrs->cpumask;
3857 copy_workqueue_attrs(target_attrs, wq->unbound_attrs);
3858 pwq = unbound_pwq_by_node(wq, node);
3861 * Let's determine what needs to be done. If the target cpumask is
3862 * different from the default pwq's, we need to compare it to @pwq's
3863 * and create a new one if they don't match. If the target cpumask
3864 * equals the default pwq's, the default pwq should be used.
3866 if (wq_calc_node_cpumask(wq->dfl_pwq->pool->attrs, node, cpu_off, cpumask)) {
3867 if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask))
3868 return;
3869 } else {
3870 goto use_dfl_pwq;
3873 /* create a new pwq */
3874 pwq = alloc_unbound_pwq(wq, target_attrs);
3875 if (!pwq) {
3876 pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n",
3877 wq->name);
3878 goto use_dfl_pwq;
3881 /* Install the new pwq. */
3882 mutex_lock(&wq->mutex);
3883 old_pwq = numa_pwq_tbl_install(wq, node, pwq);
3884 goto out_unlock;
3886 use_dfl_pwq:
3887 mutex_lock(&wq->mutex);
3888 spin_lock_irq(&wq->dfl_pwq->pool->lock);
3889 get_pwq(wq->dfl_pwq);
3890 spin_unlock_irq(&wq->dfl_pwq->pool->lock);
3891 old_pwq = numa_pwq_tbl_install(wq, node, wq->dfl_pwq);
3892 out_unlock:
3893 mutex_unlock(&wq->mutex);
3894 put_pwq_unlocked(old_pwq);
3897 static int alloc_and_link_pwqs(struct workqueue_struct *wq)
3899 bool highpri = wq->flags & WQ_HIGHPRI;
3900 int cpu, ret;
3902 if (!(wq->flags & WQ_UNBOUND)) {
3903 wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
3904 if (!wq->cpu_pwqs)
3905 return -ENOMEM;
3907 for_each_possible_cpu(cpu) {
3908 struct pool_workqueue *pwq =
3909 per_cpu_ptr(wq->cpu_pwqs, cpu);
3910 struct worker_pool *cpu_pools =
3911 per_cpu(cpu_worker_pools, cpu);
3913 init_pwq(pwq, wq, &cpu_pools[highpri]);
3915 mutex_lock(&wq->mutex);
3916 link_pwq(pwq);
3917 mutex_unlock(&wq->mutex);
3919 return 0;
3920 } else if (wq->flags & __WQ_ORDERED) {
3921 ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
3922 /* there should only be single pwq for ordering guarantee */
3923 WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||
3924 wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),
3925 "ordering guarantee broken for workqueue %s\n", wq->name);
3926 return ret;
3927 } else {
3928 return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
3932 static int wq_clamp_max_active(int max_active, unsigned int flags,
3933 const char *name)
3935 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
3937 if (max_active < 1 || max_active > lim)
3938 pr_warn("workqueue: max_active %d requested for %s is out of range, clamping between %d and %d\n",
3939 max_active, name, 1, lim);
3941 return clamp_val(max_active, 1, lim);
3945 * Workqueues which may be used during memory reclaim should have a rescuer
3946 * to guarantee forward progress.
3948 static int init_rescuer(struct workqueue_struct *wq)
3950 struct worker *rescuer;
3951 int ret;
3953 if (!(wq->flags & WQ_MEM_RECLAIM))
3954 return 0;
3956 rescuer = alloc_worker(NUMA_NO_NODE);
3957 if (!rescuer)
3958 return -ENOMEM;
3960 rescuer->rescue_wq = wq;
3961 rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", wq->name);
3962 ret = PTR_ERR_OR_ZERO(rescuer->task);
3963 if (ret) {
3964 kfree(rescuer);
3965 return ret;
3968 wq->rescuer = rescuer;
3969 kthread_bind_mask(rescuer->task, cpu_possible_mask);
3970 wake_up_process(rescuer->task);
3972 return 0;
3975 struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
3976 unsigned int flags,
3977 int max_active,
3978 struct lock_class_key *key,
3979 const char *lock_name, ...)
3981 size_t tbl_size = 0;
3982 va_list args;
3983 struct workqueue_struct *wq;
3984 struct pool_workqueue *pwq;
3987 * Unbound && max_active == 1 used to imply ordered, which is no
3988 * longer the case on NUMA machines due to per-node pools. While
3989 * alloc_ordered_workqueue() is the right way to create an ordered
3990 * workqueue, keep the previous behavior to avoid subtle breakages
3991 * on NUMA.
3993 if ((flags & WQ_UNBOUND) && max_active == 1)
3994 flags |= __WQ_ORDERED;
3996 /* see the comment above the definition of WQ_POWER_EFFICIENT */
3997 if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)
3998 flags |= WQ_UNBOUND;
4000 /* allocate wq and format name */
4001 if (flags & WQ_UNBOUND)
4002 tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]);
4004 wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL);
4005 if (!wq)
4006 return NULL;
4008 if (flags & WQ_UNBOUND) {
4009 wq->unbound_attrs = alloc_workqueue_attrs(GFP_KERNEL);
4010 if (!wq->unbound_attrs)
4011 goto err_free_wq;
4014 va_start(args, lock_name);
4015 vsnprintf(wq->name, sizeof(wq->name), fmt, args);
4016 va_end(args);
4018 max_active = max_active ?: WQ_DFL_ACTIVE;
4019 max_active = wq_clamp_max_active(max_active, flags, wq->name);
4021 /* init wq */
4022 wq->flags = flags;
4023 wq->saved_max_active = max_active;
4024 mutex_init(&wq->mutex);
4025 atomic_set(&wq->nr_pwqs_to_flush, 0);
4026 INIT_LIST_HEAD(&wq->pwqs);
4027 INIT_LIST_HEAD(&wq->flusher_queue);
4028 INIT_LIST_HEAD(&wq->flusher_overflow);
4029 INIT_LIST_HEAD(&wq->maydays);
4031 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
4032 INIT_LIST_HEAD(&wq->list);
4034 if (alloc_and_link_pwqs(wq) < 0)
4035 goto err_free_wq;
4037 if (wq_online && init_rescuer(wq) < 0)
4038 goto err_destroy;
4040 if ((wq->flags & WQ_SYSFS) && workqueue_sysfs_register(wq))
4041 goto err_destroy;
4044 * wq_pool_mutex protects global freeze state and workqueues list.
4045 * Grab it, adjust max_active and add the new @wq to workqueues
4046 * list.
4048 mutex_lock(&wq_pool_mutex);
4050 mutex_lock(&wq->mutex);
4051 for_each_pwq(pwq, wq)
4052 pwq_adjust_max_active(pwq);
4053 mutex_unlock(&wq->mutex);
4055 list_add_tail_rcu(&wq->list, &workqueues);
4057 mutex_unlock(&wq_pool_mutex);
4059 return wq;
4061 err_free_wq:
4062 free_workqueue_attrs(wq->unbound_attrs);
4063 kfree(wq);
4064 return NULL;
4065 err_destroy:
4066 destroy_workqueue(wq);
4067 return NULL;
4069 EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
4072 * destroy_workqueue - safely terminate a workqueue
4073 * @wq: target workqueue
4075 * Safely destroy a workqueue. All work currently pending will be done first.
4077 void destroy_workqueue(struct workqueue_struct *wq)
4079 struct pool_workqueue *pwq;
4080 int node;
4082 /* drain it before proceeding with destruction */
4083 drain_workqueue(wq);
4085 /* sanity checks */
4086 mutex_lock(&wq->mutex);
4087 for_each_pwq(pwq, wq) {
4088 int i;
4090 for (i = 0; i < WORK_NR_COLORS; i++) {
4091 if (WARN_ON(pwq->nr_in_flight[i])) {
4092 mutex_unlock(&wq->mutex);
4093 show_workqueue_state();
4094 return;
4098 if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) ||
4099 WARN_ON(pwq->nr_active) ||
4100 WARN_ON(!list_empty(&pwq->delayed_works))) {
4101 mutex_unlock(&wq->mutex);
4102 show_workqueue_state();
4103 return;
4106 mutex_unlock(&wq->mutex);
4109 * wq list is used to freeze wq, remove from list after
4110 * flushing is complete in case freeze races us.
4112 mutex_lock(&wq_pool_mutex);
4113 list_del_rcu(&wq->list);
4114 mutex_unlock(&wq_pool_mutex);
4116 workqueue_sysfs_unregister(wq);
4118 if (wq->rescuer)
4119 kthread_stop(wq->rescuer->task);
4121 if (!(wq->flags & WQ_UNBOUND)) {
4123 * The base ref is never dropped on per-cpu pwqs. Directly
4124 * schedule RCU free.
4126 call_rcu_sched(&wq->rcu, rcu_free_wq);
4127 } else {
4129 * We're the sole accessor of @wq at this point. Directly
4130 * access numa_pwq_tbl[] and dfl_pwq to put the base refs.
4131 * @wq will be freed when the last pwq is released.
4133 for_each_node(node) {
4134 pwq = rcu_access_pointer(wq->numa_pwq_tbl[node]);
4135 RCU_INIT_POINTER(wq->numa_pwq_tbl[node], NULL);
4136 put_pwq_unlocked(pwq);
4140 * Put dfl_pwq. @wq may be freed any time after dfl_pwq is
4141 * put. Don't access it afterwards.
4143 pwq = wq->dfl_pwq;
4144 wq->dfl_pwq = NULL;
4145 put_pwq_unlocked(pwq);
4148 EXPORT_SYMBOL_GPL(destroy_workqueue);
4151 * workqueue_set_max_active - adjust max_active of a workqueue
4152 * @wq: target workqueue
4153 * @max_active: new max_active value.
4155 * Set max_active of @wq to @max_active.
4157 * CONTEXT:
4158 * Don't call from IRQ context.
4160 void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
4162 struct pool_workqueue *pwq;
4164 /* disallow meddling with max_active for ordered workqueues */
4165 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
4166 return;
4168 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
4170 mutex_lock(&wq->mutex);
4172 wq->flags &= ~__WQ_ORDERED;
4173 wq->saved_max_active = max_active;
4175 for_each_pwq(pwq, wq)
4176 pwq_adjust_max_active(pwq);
4178 mutex_unlock(&wq->mutex);
4180 EXPORT_SYMBOL_GPL(workqueue_set_max_active);
4183 * current_work - retrieve %current task's work struct
4185 * Determine if %current task is a workqueue worker and what it's working on.
4186 * Useful to find out the context that the %current task is running in.
4188 * Return: work struct if %current task is a workqueue worker, %NULL otherwise.
4190 struct work_struct *current_work(void)
4192 struct worker *worker = current_wq_worker();
4194 return worker ? worker->current_work : NULL;
4196 EXPORT_SYMBOL(current_work);
4199 * current_is_workqueue_rescuer - is %current workqueue rescuer?
4201 * Determine whether %current is a workqueue rescuer. Can be used from
4202 * work functions to determine whether it's being run off the rescuer task.
4204 * Return: %true if %current is a workqueue rescuer. %false otherwise.
4206 bool current_is_workqueue_rescuer(void)
4208 struct worker *worker = current_wq_worker();
4210 return worker && worker->rescue_wq;
4214 * workqueue_congested - test whether a workqueue is congested
4215 * @cpu: CPU in question
4216 * @wq: target workqueue
4218 * Test whether @wq's cpu workqueue for @cpu is congested. There is
4219 * no synchronization around this function and the test result is
4220 * unreliable and only useful as advisory hints or for debugging.
4222 * If @cpu is WORK_CPU_UNBOUND, the test is performed on the local CPU.
4223 * Note that both per-cpu and unbound workqueues may be associated with
4224 * multiple pool_workqueues which have separate congested states. A
4225 * workqueue being congested on one CPU doesn't mean the workqueue is also
4226 * contested on other CPUs / NUMA nodes.
4228 * Return:
4229 * %true if congested, %false otherwise.
4231 bool workqueue_congested(int cpu, struct workqueue_struct *wq)
4233 struct pool_workqueue *pwq;
4234 bool ret;
4236 rcu_read_lock_sched();
4238 if (cpu == WORK_CPU_UNBOUND)
4239 cpu = smp_processor_id();
4241 if (!(wq->flags & WQ_UNBOUND))
4242 pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
4243 else
4244 pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
4246 ret = !list_empty(&pwq->delayed_works);
4247 rcu_read_unlock_sched();
4249 return ret;
4251 EXPORT_SYMBOL_GPL(workqueue_congested);
4254 * work_busy - test whether a work is currently pending or running
4255 * @work: the work to be tested
4257 * Test whether @work is currently pending or running. There is no
4258 * synchronization around this function and the test result is
4259 * unreliable and only useful as advisory hints or for debugging.
4261 * Return:
4262 * OR'd bitmask of WORK_BUSY_* bits.
4264 unsigned int work_busy(struct work_struct *work)
4266 struct worker_pool *pool;
4267 unsigned long flags;
4268 unsigned int ret = 0;
4270 if (work_pending(work))
4271 ret |= WORK_BUSY_PENDING;
4273 local_irq_save(flags);
4274 pool = get_work_pool(work);
4275 if (pool) {
4276 spin_lock(&pool->lock);
4277 if (find_worker_executing_work(pool, work))
4278 ret |= WORK_BUSY_RUNNING;
4279 spin_unlock(&pool->lock);
4281 local_irq_restore(flags);
4283 return ret;
4285 EXPORT_SYMBOL_GPL(work_busy);
4288 * set_worker_desc - set description for the current work item
4289 * @fmt: printf-style format string
4290 * @...: arguments for the format string
4292 * This function can be called by a running work function to describe what
4293 * the work item is about. If the worker task gets dumped, this
4294 * information will be printed out together to help debugging. The
4295 * description can be at most WORKER_DESC_LEN including the trailing '\0'.
4297 void set_worker_desc(const char *fmt, ...)
4299 struct worker *worker = current_wq_worker();
4300 va_list args;
4302 if (worker) {
4303 va_start(args, fmt);
4304 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
4305 va_end(args);
4306 worker->desc_valid = true;
4311 * print_worker_info - print out worker information and description
4312 * @log_lvl: the log level to use when printing
4313 * @task: target task
4315 * If @task is a worker and currently executing a work item, print out the
4316 * name of the workqueue being serviced and worker description set with
4317 * set_worker_desc() by the currently executing work item.
4319 * This function can be safely called on any task as long as the
4320 * task_struct itself is accessible. While safe, this function isn't
4321 * synchronized and may print out mixups or garbages of limited length.
4323 void print_worker_info(const char *log_lvl, struct task_struct *task)
4325 work_func_t *fn = NULL;
4326 char name[WQ_NAME_LEN] = { };
4327 char desc[WORKER_DESC_LEN] = { };
4328 struct pool_workqueue *pwq = NULL;
4329 struct workqueue_struct *wq = NULL;
4330 bool desc_valid = false;
4331 struct worker *worker;
4333 if (!(task->flags & PF_WQ_WORKER))
4334 return;
4337 * This function is called without any synchronization and @task
4338 * could be in any state. Be careful with dereferences.
4340 worker = kthread_probe_data(task);
4343 * Carefully copy the associated workqueue's workfn and name. Keep
4344 * the original last '\0' in case the original contains garbage.
4346 probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
4347 probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
4348 probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
4349 probe_kernel_read(name, wq->name, sizeof(name) - 1);
4351 /* copy worker description */
4352 probe_kernel_read(&desc_valid, &worker->desc_valid, sizeof(desc_valid));
4353 if (desc_valid)
4354 probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
4356 if (fn || name[0] || desc[0]) {
4357 printk("%sWorkqueue: %s %pf", log_lvl, name, fn);
4358 if (desc[0])
4359 pr_cont(" (%s)", desc);
4360 pr_cont("\n");
4364 static void pr_cont_pool_info(struct worker_pool *pool)
4366 pr_cont(" cpus=%*pbl", nr_cpumask_bits, pool->attrs->cpumask);
4367 if (pool->node != NUMA_NO_NODE)
4368 pr_cont(" node=%d", pool->node);
4369 pr_cont(" flags=0x%x nice=%d", pool->flags, pool->attrs->nice);
4372 static void pr_cont_work(bool comma, struct work_struct *work)
4374 if (work->func == wq_barrier_func) {
4375 struct wq_barrier *barr;
4377 barr = container_of(work, struct wq_barrier, work);
4379 pr_cont("%s BAR(%d)", comma ? "," : "",
4380 task_pid_nr(barr->task));
4381 } else {
4382 pr_cont("%s %pf", comma ? "," : "", work->func);
4386 static void show_pwq(struct pool_workqueue *pwq)
4388 struct worker_pool *pool = pwq->pool;
4389 struct work_struct *work;
4390 struct worker *worker;
4391 bool has_in_flight = false, has_pending = false;
4392 int bkt;
4394 pr_info(" pwq %d:", pool->id);
4395 pr_cont_pool_info(pool);
4397 pr_cont(" active=%d/%d%s\n", pwq->nr_active, pwq->max_active,
4398 !list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
4400 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4401 if (worker->current_pwq == pwq) {
4402 has_in_flight = true;
4403 break;
4406 if (has_in_flight) {
4407 bool comma = false;
4409 pr_info(" in-flight:");
4410 hash_for_each(pool->busy_hash, bkt, worker, hentry) {
4411 if (worker->current_pwq != pwq)
4412 continue;
4414 pr_cont("%s %d%s:%pf", comma ? "," : "",
4415 task_pid_nr(worker->task),
4416 worker == pwq->wq->rescuer ? "(RESCUER)" : "",
4417 worker->current_func);
4418 list_for_each_entry(work, &worker->scheduled, entry)
4419 pr_cont_work(false, work);
4420 comma = true;
4422 pr_cont("\n");
4425 list_for_each_entry(work, &pool->worklist, entry) {
4426 if (get_work_pwq(work) == pwq) {
4427 has_pending = true;
4428 break;
4431 if (has_pending) {
4432 bool comma = false;
4434 pr_info(" pending:");
4435 list_for_each_entry(work, &pool->worklist, entry) {
4436 if (get_work_pwq(work) != pwq)
4437 continue;
4439 pr_cont_work(comma, work);
4440 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4442 pr_cont("\n");
4445 if (!list_empty(&pwq->delayed_works)) {
4446 bool comma = false;
4448 pr_info(" delayed:");
4449 list_for_each_entry(work, &pwq->delayed_works, entry) {
4450 pr_cont_work(comma, work);
4451 comma = !(*work_data_bits(work) & WORK_STRUCT_LINKED);
4453 pr_cont("\n");
4458 * show_workqueue_state - dump workqueue state
4460 * Called from a sysrq handler or try_to_freeze_tasks() and prints out
4461 * all busy workqueues and pools.
4463 void show_workqueue_state(void)
4465 struct workqueue_struct *wq;
4466 struct worker_pool *pool;
4467 unsigned long flags;
4468 int pi;
4470 rcu_read_lock_sched();
4472 pr_info("Showing busy workqueues and worker pools:\n");
4474 list_for_each_entry_rcu(wq, &workqueues, list) {
4475 struct pool_workqueue *pwq;
4476 bool idle = true;
4478 for_each_pwq(pwq, wq) {
4479 if (pwq->nr_active || !list_empty(&pwq->delayed_works)) {
4480 idle = false;
4481 break;
4484 if (idle)
4485 continue;
4487 pr_info("workqueue %s: flags=0x%x\n", wq->name, wq->flags);
4489 for_each_pwq(pwq, wq) {
4490 spin_lock_irqsave(&pwq->pool->lock, flags);
4491 if (pwq->nr_active || !list_empty(&pwq->delayed_works))
4492 show_pwq(pwq);
4493 spin_unlock_irqrestore(&pwq->pool->lock, flags);
4495 * We could be printing a lot from atomic context, e.g.
4496 * sysrq-t -> show_workqueue_state(). Avoid triggering
4497 * hard lockup.
4499 touch_nmi_watchdog();
4503 for_each_pool(pool, pi) {
4504 struct worker *worker;
4505 bool first = true;
4507 spin_lock_irqsave(&pool->lock, flags);
4508 if (pool->nr_workers == pool->nr_idle)
4509 goto next_pool;
4511 pr_info("pool %d:", pool->id);
4512 pr_cont_pool_info(pool);
4513 pr_cont(" hung=%us workers=%d",
4514 jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000,
4515 pool->nr_workers);
4516 if (pool->manager)
4517 pr_cont(" manager: %d",
4518 task_pid_nr(pool->manager->task));
4519 list_for_each_entry(worker, &pool->idle_list, entry) {
4520 pr_cont(" %s%d", first ? "idle: " : "",
4521 task_pid_nr(worker->task));
4522 first = false;
4524 pr_cont("\n");
4525 next_pool:
4526 spin_unlock_irqrestore(&pool->lock, flags);
4528 * We could be printing a lot from atomic context, e.g.
4529 * sysrq-t -> show_workqueue_state(). Avoid triggering
4530 * hard lockup.
4532 touch_nmi_watchdog();
4535 rcu_read_unlock_sched();
4539 * CPU hotplug.
4541 * There are two challenges in supporting CPU hotplug. Firstly, there
4542 * are a lot of assumptions on strong associations among work, pwq and
4543 * pool which make migrating pending and scheduled works very
4544 * difficult to implement without impacting hot paths. Secondly,
4545 * worker pools serve mix of short, long and very long running works making
4546 * blocked draining impractical.
4548 * This is solved by allowing the pools to be disassociated from the CPU
4549 * running as an unbound one and allowing it to be reattached later if the
4550 * cpu comes back online.
4553 static void unbind_workers(int cpu)
4555 struct worker_pool *pool;
4556 struct worker *worker;
4558 for_each_cpu_worker_pool(pool, cpu) {
4559 mutex_lock(&pool->attach_mutex);
4560 spin_lock_irq(&pool->lock);
4563 * We've blocked all attach/detach operations. Make all workers
4564 * unbound and set DISASSOCIATED. Before this, all workers
4565 * except for the ones which are still executing works from
4566 * before the last CPU down must be on the cpu. After
4567 * this, they may become diasporas.
4569 for_each_pool_worker(worker, pool)
4570 worker->flags |= WORKER_UNBOUND;
4572 pool->flags |= POOL_DISASSOCIATED;
4574 spin_unlock_irq(&pool->lock);
4575 mutex_unlock(&pool->attach_mutex);
4578 * Call schedule() so that we cross rq->lock and thus can
4579 * guarantee sched callbacks see the %WORKER_UNBOUND flag.
4580 * This is necessary as scheduler callbacks may be invoked
4581 * from other cpus.
4583 schedule();
4586 * Sched callbacks are disabled now. Zap nr_running.
4587 * After this, nr_running stays zero and need_more_worker()
4588 * and keep_working() are always true as long as the
4589 * worklist is not empty. This pool now behaves as an
4590 * unbound (in terms of concurrency management) pool which
4591 * are served by workers tied to the pool.
4593 atomic_set(&pool->nr_running, 0);
4596 * With concurrency management just turned off, a busy
4597 * worker blocking could lead to lengthy stalls. Kick off
4598 * unbound chain execution of currently pending work items.
4600 spin_lock_irq(&pool->lock);
4601 wake_up_worker(pool);
4602 spin_unlock_irq(&pool->lock);
4607 * rebind_workers - rebind all workers of a pool to the associated CPU
4608 * @pool: pool of interest
4610 * @pool->cpu is coming online. Rebind all workers to the CPU.
4612 static void rebind_workers(struct worker_pool *pool)
4614 struct worker *worker;
4616 lockdep_assert_held(&pool->attach_mutex);
4619 * Restore CPU affinity of all workers. As all idle workers should
4620 * be on the run-queue of the associated CPU before any local
4621 * wake-ups for concurrency management happen, restore CPU affinity
4622 * of all workers first and then clear UNBOUND. As we're called
4623 * from CPU_ONLINE, the following shouldn't fail.
4625 for_each_pool_worker(worker, pool)
4626 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
4627 pool->attrs->cpumask) < 0);
4629 spin_lock_irq(&pool->lock);
4631 pool->flags &= ~POOL_DISASSOCIATED;
4633 for_each_pool_worker(worker, pool) {
4634 unsigned int worker_flags = worker->flags;
4637 * A bound idle worker should actually be on the runqueue
4638 * of the associated CPU for local wake-ups targeting it to
4639 * work. Kick all idle workers so that they migrate to the
4640 * associated CPU. Doing this in the same loop as
4641 * replacing UNBOUND with REBOUND is safe as no worker will
4642 * be bound before @pool->lock is released.
4644 if (worker_flags & WORKER_IDLE)
4645 wake_up_process(worker->task);
4648 * We want to clear UNBOUND but can't directly call
4649 * worker_clr_flags() or adjust nr_running. Atomically
4650 * replace UNBOUND with another NOT_RUNNING flag REBOUND.
4651 * @worker will clear REBOUND using worker_clr_flags() when
4652 * it initiates the next execution cycle thus restoring
4653 * concurrency management. Note that when or whether
4654 * @worker clears REBOUND doesn't affect correctness.
4656 * WRITE_ONCE() is necessary because @worker->flags may be
4657 * tested without holding any lock in
4658 * wq_worker_waking_up(). Without it, NOT_RUNNING test may
4659 * fail incorrectly leading to premature concurrency
4660 * management operations.
4662 WARN_ON_ONCE(!(worker_flags & WORKER_UNBOUND));
4663 worker_flags |= WORKER_REBOUND;
4664 worker_flags &= ~WORKER_UNBOUND;
4665 WRITE_ONCE(worker->flags, worker_flags);
4668 spin_unlock_irq(&pool->lock);
4672 * restore_unbound_workers_cpumask - restore cpumask of unbound workers
4673 * @pool: unbound pool of interest
4674 * @cpu: the CPU which is coming up
4676 * An unbound pool may end up with a cpumask which doesn't have any online
4677 * CPUs. When a worker of such pool get scheduled, the scheduler resets
4678 * its cpus_allowed. If @cpu is in @pool's cpumask which didn't have any
4679 * online CPU before, cpus_allowed of all its workers should be restored.
4681 static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
4683 static cpumask_t cpumask;
4684 struct worker *worker;
4686 lockdep_assert_held(&pool->attach_mutex);
4688 /* is @cpu allowed for @pool? */
4689 if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
4690 return;
4692 cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
4694 /* as we're called from CPU_ONLINE, the following shouldn't fail */
4695 for_each_pool_worker(worker, pool)
4696 WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
4699 int workqueue_prepare_cpu(unsigned int cpu)
4701 struct worker_pool *pool;
4703 for_each_cpu_worker_pool(pool, cpu) {
4704 if (pool->nr_workers)
4705 continue;
4706 if (!create_worker(pool))
4707 return -ENOMEM;
4709 return 0;
4712 int workqueue_online_cpu(unsigned int cpu)
4714 struct worker_pool *pool;
4715 struct workqueue_struct *wq;
4716 int pi;
4718 mutex_lock(&wq_pool_mutex);
4720 for_each_pool(pool, pi) {
4721 mutex_lock(&pool->attach_mutex);
4723 if (pool->cpu == cpu)
4724 rebind_workers(pool);
4725 else if (pool->cpu < 0)
4726 restore_unbound_workers_cpumask(pool, cpu);
4728 mutex_unlock(&pool->attach_mutex);
4731 /* update NUMA affinity of unbound workqueues */
4732 list_for_each_entry(wq, &workqueues, list)
4733 wq_update_unbound_numa(wq, cpu, true);
4735 mutex_unlock(&wq_pool_mutex);
4736 return 0;
4739 int workqueue_offline_cpu(unsigned int cpu)
4741 struct workqueue_struct *wq;
4743 /* unbinding per-cpu workers should happen on the local CPU */
4744 if (WARN_ON(cpu != smp_processor_id()))
4745 return -1;
4747 unbind_workers(cpu);
4749 /* update NUMA affinity of unbound workqueues */
4750 mutex_lock(&wq_pool_mutex);
4751 list_for_each_entry(wq, &workqueues, list)
4752 wq_update_unbound_numa(wq, cpu, false);
4753 mutex_unlock(&wq_pool_mutex);
4755 return 0;
4758 #ifdef CONFIG_SMP
4760 struct work_for_cpu {
4761 struct work_struct work;
4762 long (*fn)(void *);
4763 void *arg;
4764 long ret;
4767 static void work_for_cpu_fn(struct work_struct *work)
4769 struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work);
4771 wfc->ret = wfc->fn(wfc->arg);
4775 * work_on_cpu - run a function in thread context on a particular cpu
4776 * @cpu: the cpu to run on
4777 * @fn: the function to run
4778 * @arg: the function arg
4780 * It is up to the caller to ensure that the cpu doesn't go offline.
4781 * The caller must not hold any locks which would prevent @fn from completing.
4783 * Return: The value @fn returns.
4785 long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
4787 struct work_for_cpu wfc = { .fn = fn, .arg = arg };
4789 INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn);
4790 schedule_work_on(cpu, &wfc.work);
4791 flush_work(&wfc.work);
4792 destroy_work_on_stack(&wfc.work);
4793 return wfc.ret;
4795 EXPORT_SYMBOL_GPL(work_on_cpu);
4798 * work_on_cpu_safe - run a function in thread context on a particular cpu
4799 * @cpu: the cpu to run on
4800 * @fn: the function to run
4801 * @arg: the function argument
4803 * Disables CPU hotplug and calls work_on_cpu(). The caller must not hold
4804 * any locks which would prevent @fn from completing.
4806 * Return: The value @fn returns.
4808 long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg)
4810 long ret = -ENODEV;
4812 get_online_cpus();
4813 if (cpu_online(cpu))
4814 ret = work_on_cpu(cpu, fn, arg);
4815 put_online_cpus();
4816 return ret;
4818 EXPORT_SYMBOL_GPL(work_on_cpu_safe);
4819 #endif /* CONFIG_SMP */
4821 #ifdef CONFIG_FREEZER
4824 * freeze_workqueues_begin - begin freezing workqueues
4826 * Start freezing workqueues. After this function returns, all freezable
4827 * workqueues will queue new works to their delayed_works list instead of
4828 * pool->worklist.
4830 * CONTEXT:
4831 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4833 void freeze_workqueues_begin(void)
4835 struct workqueue_struct *wq;
4836 struct pool_workqueue *pwq;
4838 mutex_lock(&wq_pool_mutex);
4840 WARN_ON_ONCE(workqueue_freezing);
4841 workqueue_freezing = true;
4843 list_for_each_entry(wq, &workqueues, list) {
4844 mutex_lock(&wq->mutex);
4845 for_each_pwq(pwq, wq)
4846 pwq_adjust_max_active(pwq);
4847 mutex_unlock(&wq->mutex);
4850 mutex_unlock(&wq_pool_mutex);
4854 * freeze_workqueues_busy - are freezable workqueues still busy?
4856 * Check whether freezing is complete. This function must be called
4857 * between freeze_workqueues_begin() and thaw_workqueues().
4859 * CONTEXT:
4860 * Grabs and releases wq_pool_mutex.
4862 * Return:
4863 * %true if some freezable workqueues are still busy. %false if freezing
4864 * is complete.
4866 bool freeze_workqueues_busy(void)
4868 bool busy = false;
4869 struct workqueue_struct *wq;
4870 struct pool_workqueue *pwq;
4872 mutex_lock(&wq_pool_mutex);
4874 WARN_ON_ONCE(!workqueue_freezing);
4876 list_for_each_entry(wq, &workqueues, list) {
4877 if (!(wq->flags & WQ_FREEZABLE))
4878 continue;
4880 * nr_active is monotonically decreasing. It's safe
4881 * to peek without lock.
4883 rcu_read_lock_sched();
4884 for_each_pwq(pwq, wq) {
4885 WARN_ON_ONCE(pwq->nr_active < 0);
4886 if (pwq->nr_active) {
4887 busy = true;
4888 rcu_read_unlock_sched();
4889 goto out_unlock;
4892 rcu_read_unlock_sched();
4894 out_unlock:
4895 mutex_unlock(&wq_pool_mutex);
4896 return busy;
4900 * thaw_workqueues - thaw workqueues
4902 * Thaw workqueues. Normal queueing is restored and all collected
4903 * frozen works are transferred to their respective pool worklists.
4905 * CONTEXT:
4906 * Grabs and releases wq_pool_mutex, wq->mutex and pool->lock's.
4908 void thaw_workqueues(void)
4910 struct workqueue_struct *wq;
4911 struct pool_workqueue *pwq;
4913 mutex_lock(&wq_pool_mutex);
4915 if (!workqueue_freezing)
4916 goto out_unlock;
4918 workqueue_freezing = false;
4920 /* restore max_active and repopulate worklist */
4921 list_for_each_entry(wq, &workqueues, list) {
4922 mutex_lock(&wq->mutex);
4923 for_each_pwq(pwq, wq)
4924 pwq_adjust_max_active(pwq);
4925 mutex_unlock(&wq->mutex);
4928 out_unlock:
4929 mutex_unlock(&wq_pool_mutex);
4931 #endif /* CONFIG_FREEZER */
4933 static int workqueue_apply_unbound_cpumask(void)
4935 LIST_HEAD(ctxs);
4936 int ret = 0;
4937 struct workqueue_struct *wq;
4938 struct apply_wqattrs_ctx *ctx, *n;
4940 lockdep_assert_held(&wq_pool_mutex);
4942 list_for_each_entry(wq, &workqueues, list) {
4943 if (!(wq->flags & WQ_UNBOUND))
4944 continue;
4945 /* creating multiple pwqs breaks ordering guarantee */
4946 if (wq->flags & __WQ_ORDERED)
4947 continue;
4949 ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);
4950 if (!ctx) {
4951 ret = -ENOMEM;
4952 break;
4955 list_add_tail(&ctx->list, &ctxs);
4958 list_for_each_entry_safe(ctx, n, &ctxs, list) {
4959 if (!ret)
4960 apply_wqattrs_commit(ctx);
4961 apply_wqattrs_cleanup(ctx);
4964 return ret;
4968 * workqueue_set_unbound_cpumask - Set the low-level unbound cpumask
4969 * @cpumask: the cpumask to set
4971 * The low-level workqueues cpumask is a global cpumask that limits
4972 * the affinity of all unbound workqueues. This function check the @cpumask
4973 * and apply it to all unbound workqueues and updates all pwqs of them.
4975 * Retun: 0 - Success
4976 * -EINVAL - Invalid @cpumask
4977 * -ENOMEM - Failed to allocate memory for attrs or pwqs.
4979 int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)
4981 int ret = -EINVAL;
4982 cpumask_var_t saved_cpumask;
4984 if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL))
4985 return -ENOMEM;
4988 * Not excluding isolated cpus on purpose.
4989 * If the user wishes to include them, we allow that.
4991 cpumask_and(cpumask, cpumask, cpu_possible_mask);
4992 if (!cpumask_empty(cpumask)) {
4993 apply_wqattrs_lock();
4995 /* save the old wq_unbound_cpumask. */
4996 cpumask_copy(saved_cpumask, wq_unbound_cpumask);
4998 /* update wq_unbound_cpumask at first and apply it to wqs. */
4999 cpumask_copy(wq_unbound_cpumask, cpumask);
5000 ret = workqueue_apply_unbound_cpumask();
5002 /* restore the wq_unbound_cpumask when failed. */
5003 if (ret < 0)
5004 cpumask_copy(wq_unbound_cpumask, saved_cpumask);
5006 apply_wqattrs_unlock();
5009 free_cpumask_var(saved_cpumask);
5010 return ret;
5013 #ifdef CONFIG_SYSFS
5015 * Workqueues with WQ_SYSFS flag set is visible to userland via
5016 * /sys/bus/workqueue/devices/WQ_NAME. All visible workqueues have the
5017 * following attributes.
5019 * per_cpu RO bool : whether the workqueue is per-cpu or unbound
5020 * max_active RW int : maximum number of in-flight work items
5022 * Unbound workqueues have the following extra attributes.
5024 * pool_ids RO int : the associated pool IDs for each node
5025 * nice RW int : nice value of the workers
5026 * cpumask RW mask : bitmask of allowed CPUs for the workers
5027 * numa RW bool : whether enable NUMA affinity
5029 struct wq_device {
5030 struct workqueue_struct *wq;
5031 struct device dev;
5034 static struct workqueue_struct *dev_to_wq(struct device *dev)
5036 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5038 return wq_dev->wq;
5041 static ssize_t per_cpu_show(struct device *dev, struct device_attribute *attr,
5042 char *buf)
5044 struct workqueue_struct *wq = dev_to_wq(dev);
5046 return scnprintf(buf, PAGE_SIZE, "%d\n", (bool)!(wq->flags & WQ_UNBOUND));
5048 static DEVICE_ATTR_RO(per_cpu);
5050 static ssize_t max_active_show(struct device *dev,
5051 struct device_attribute *attr, char *buf)
5053 struct workqueue_struct *wq = dev_to_wq(dev);
5055 return scnprintf(buf, PAGE_SIZE, "%d\n", wq->saved_max_active);
5058 static ssize_t max_active_store(struct device *dev,
5059 struct device_attribute *attr, const char *buf,
5060 size_t count)
5062 struct workqueue_struct *wq = dev_to_wq(dev);
5063 int val;
5065 if (sscanf(buf, "%d", &val) != 1 || val <= 0)
5066 return -EINVAL;
5068 workqueue_set_max_active(wq, val);
5069 return count;
5071 static DEVICE_ATTR_RW(max_active);
5073 static struct attribute *wq_sysfs_attrs[] = {
5074 &dev_attr_per_cpu.attr,
5075 &dev_attr_max_active.attr,
5076 NULL,
5078 ATTRIBUTE_GROUPS(wq_sysfs);
5080 static ssize_t wq_pool_ids_show(struct device *dev,
5081 struct device_attribute *attr, char *buf)
5083 struct workqueue_struct *wq = dev_to_wq(dev);
5084 const char *delim = "";
5085 int node, written = 0;
5087 rcu_read_lock_sched();
5088 for_each_node(node) {
5089 written += scnprintf(buf + written, PAGE_SIZE - written,
5090 "%s%d:%d", delim, node,
5091 unbound_pwq_by_node(wq, node)->pool->id);
5092 delim = " ";
5094 written += scnprintf(buf + written, PAGE_SIZE - written, "\n");
5095 rcu_read_unlock_sched();
5097 return written;
5100 static ssize_t wq_nice_show(struct device *dev, struct device_attribute *attr,
5101 char *buf)
5103 struct workqueue_struct *wq = dev_to_wq(dev);
5104 int written;
5106 mutex_lock(&wq->mutex);
5107 written = scnprintf(buf, PAGE_SIZE, "%d\n", wq->unbound_attrs->nice);
5108 mutex_unlock(&wq->mutex);
5110 return written;
5113 /* prepare workqueue_attrs for sysfs store operations */
5114 static struct workqueue_attrs *wq_sysfs_prep_attrs(struct workqueue_struct *wq)
5116 struct workqueue_attrs *attrs;
5118 lockdep_assert_held(&wq_pool_mutex);
5120 attrs = alloc_workqueue_attrs(GFP_KERNEL);
5121 if (!attrs)
5122 return NULL;
5124 copy_workqueue_attrs(attrs, wq->unbound_attrs);
5125 return attrs;
5128 static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr,
5129 const char *buf, size_t count)
5131 struct workqueue_struct *wq = dev_to_wq(dev);
5132 struct workqueue_attrs *attrs;
5133 int ret = -ENOMEM;
5135 apply_wqattrs_lock();
5137 attrs = wq_sysfs_prep_attrs(wq);
5138 if (!attrs)
5139 goto out_unlock;
5141 if (sscanf(buf, "%d", &attrs->nice) == 1 &&
5142 attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE)
5143 ret = apply_workqueue_attrs_locked(wq, attrs);
5144 else
5145 ret = -EINVAL;
5147 out_unlock:
5148 apply_wqattrs_unlock();
5149 free_workqueue_attrs(attrs);
5150 return ret ?: count;
5153 static ssize_t wq_cpumask_show(struct device *dev,
5154 struct device_attribute *attr, char *buf)
5156 struct workqueue_struct *wq = dev_to_wq(dev);
5157 int written;
5159 mutex_lock(&wq->mutex);
5160 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5161 cpumask_pr_args(wq->unbound_attrs->cpumask));
5162 mutex_unlock(&wq->mutex);
5163 return written;
5166 static ssize_t wq_cpumask_store(struct device *dev,
5167 struct device_attribute *attr,
5168 const char *buf, size_t count)
5170 struct workqueue_struct *wq = dev_to_wq(dev);
5171 struct workqueue_attrs *attrs;
5172 int ret = -ENOMEM;
5174 apply_wqattrs_lock();
5176 attrs = wq_sysfs_prep_attrs(wq);
5177 if (!attrs)
5178 goto out_unlock;
5180 ret = cpumask_parse(buf, attrs->cpumask);
5181 if (!ret)
5182 ret = apply_workqueue_attrs_locked(wq, attrs);
5184 out_unlock:
5185 apply_wqattrs_unlock();
5186 free_workqueue_attrs(attrs);
5187 return ret ?: count;
5190 static ssize_t wq_numa_show(struct device *dev, struct device_attribute *attr,
5191 char *buf)
5193 struct workqueue_struct *wq = dev_to_wq(dev);
5194 int written;
5196 mutex_lock(&wq->mutex);
5197 written = scnprintf(buf, PAGE_SIZE, "%d\n",
5198 !wq->unbound_attrs->no_numa);
5199 mutex_unlock(&wq->mutex);
5201 return written;
5204 static ssize_t wq_numa_store(struct device *dev, struct device_attribute *attr,
5205 const char *buf, size_t count)
5207 struct workqueue_struct *wq = dev_to_wq(dev);
5208 struct workqueue_attrs *attrs;
5209 int v, ret = -ENOMEM;
5211 apply_wqattrs_lock();
5213 attrs = wq_sysfs_prep_attrs(wq);
5214 if (!attrs)
5215 goto out_unlock;
5217 ret = -EINVAL;
5218 if (sscanf(buf, "%d", &v) == 1) {
5219 attrs->no_numa = !v;
5220 ret = apply_workqueue_attrs_locked(wq, attrs);
5223 out_unlock:
5224 apply_wqattrs_unlock();
5225 free_workqueue_attrs(attrs);
5226 return ret ?: count;
5229 static struct device_attribute wq_sysfs_unbound_attrs[] = {
5230 __ATTR(pool_ids, 0444, wq_pool_ids_show, NULL),
5231 __ATTR(nice, 0644, wq_nice_show, wq_nice_store),
5232 __ATTR(cpumask, 0644, wq_cpumask_show, wq_cpumask_store),
5233 __ATTR(numa, 0644, wq_numa_show, wq_numa_store),
5234 __ATTR_NULL,
5237 static struct bus_type wq_subsys = {
5238 .name = "workqueue",
5239 .dev_groups = wq_sysfs_groups,
5242 static ssize_t wq_unbound_cpumask_show(struct device *dev,
5243 struct device_attribute *attr, char *buf)
5245 int written;
5247 mutex_lock(&wq_pool_mutex);
5248 written = scnprintf(buf, PAGE_SIZE, "%*pb\n",
5249 cpumask_pr_args(wq_unbound_cpumask));
5250 mutex_unlock(&wq_pool_mutex);
5252 return written;
5255 static ssize_t wq_unbound_cpumask_store(struct device *dev,
5256 struct device_attribute *attr, const char *buf, size_t count)
5258 cpumask_var_t cpumask;
5259 int ret;
5261 if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
5262 return -ENOMEM;
5264 ret = cpumask_parse(buf, cpumask);
5265 if (!ret)
5266 ret = workqueue_set_unbound_cpumask(cpumask);
5268 free_cpumask_var(cpumask);
5269 return ret ? ret : count;
5272 static struct device_attribute wq_sysfs_cpumask_attr =
5273 __ATTR(cpumask, 0644, wq_unbound_cpumask_show,
5274 wq_unbound_cpumask_store);
5276 static int __init wq_sysfs_init(void)
5278 int err;
5280 err = subsys_virtual_register(&wq_subsys, NULL);
5281 if (err)
5282 return err;
5284 return device_create_file(wq_subsys.dev_root, &wq_sysfs_cpumask_attr);
5286 core_initcall(wq_sysfs_init);
5288 static void wq_device_release(struct device *dev)
5290 struct wq_device *wq_dev = container_of(dev, struct wq_device, dev);
5292 kfree(wq_dev);
5296 * workqueue_sysfs_register - make a workqueue visible in sysfs
5297 * @wq: the workqueue to register
5299 * Expose @wq in sysfs under /sys/bus/workqueue/devices.
5300 * alloc_workqueue*() automatically calls this function if WQ_SYSFS is set
5301 * which is the preferred method.
5303 * Workqueue user should use this function directly iff it wants to apply
5304 * workqueue_attrs before making the workqueue visible in sysfs; otherwise,
5305 * apply_workqueue_attrs() may race against userland updating the
5306 * attributes.
5308 * Return: 0 on success, -errno on failure.
5310 int workqueue_sysfs_register(struct workqueue_struct *wq)
5312 struct wq_device *wq_dev;
5313 int ret;
5316 * Adjusting max_active or creating new pwqs by applying
5317 * attributes breaks ordering guarantee. Disallow exposing ordered
5318 * workqueues.
5320 if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))
5321 return -EINVAL;
5323 wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);
5324 if (!wq_dev)
5325 return -ENOMEM;
5327 wq_dev->wq = wq;
5328 wq_dev->dev.bus = &wq_subsys;
5329 wq_dev->dev.release = wq_device_release;
5330 dev_set_name(&wq_dev->dev, "%s", wq->name);
5333 * unbound_attrs are created separately. Suppress uevent until
5334 * everything is ready.
5336 dev_set_uevent_suppress(&wq_dev->dev, true);
5338 ret = device_register(&wq_dev->dev);
5339 if (ret) {
5340 kfree(wq_dev);
5341 wq->wq_dev = NULL;
5342 return ret;
5345 if (wq->flags & WQ_UNBOUND) {
5346 struct device_attribute *attr;
5348 for (attr = wq_sysfs_unbound_attrs; attr->attr.name; attr++) {
5349 ret = device_create_file(&wq_dev->dev, attr);
5350 if (ret) {
5351 device_unregister(&wq_dev->dev);
5352 wq->wq_dev = NULL;
5353 return ret;
5358 dev_set_uevent_suppress(&wq_dev->dev, false);
5359 kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD);
5360 return 0;
5364 * workqueue_sysfs_unregister - undo workqueue_sysfs_register()
5365 * @wq: the workqueue to unregister
5367 * If @wq is registered to sysfs by workqueue_sysfs_register(), unregister.
5369 static void workqueue_sysfs_unregister(struct workqueue_struct *wq)
5371 struct wq_device *wq_dev = wq->wq_dev;
5373 if (!wq->wq_dev)
5374 return;
5376 wq->wq_dev = NULL;
5377 device_unregister(&wq_dev->dev);
5379 #else /* CONFIG_SYSFS */
5380 static void workqueue_sysfs_unregister(struct workqueue_struct *wq) { }
5381 #endif /* CONFIG_SYSFS */
5384 * Workqueue watchdog.
5386 * Stall may be caused by various bugs - missing WQ_MEM_RECLAIM, illegal
5387 * flush dependency, a concurrency managed work item which stays RUNNING
5388 * indefinitely. Workqueue stalls can be very difficult to debug as the
5389 * usual warning mechanisms don't trigger and internal workqueue state is
5390 * largely opaque.
5392 * Workqueue watchdog monitors all worker pools periodically and dumps
5393 * state if some pools failed to make forward progress for a while where
5394 * forward progress is defined as the first item on ->worklist changing.
5396 * This mechanism is controlled through the kernel parameter
5397 * "workqueue.watchdog_thresh" which can be updated at runtime through the
5398 * corresponding sysfs parameter file.
5400 #ifdef CONFIG_WQ_WATCHDOG
5402 static unsigned long wq_watchdog_thresh = 30;
5403 static struct timer_list wq_watchdog_timer;
5405 static unsigned long wq_watchdog_touched = INITIAL_JIFFIES;
5406 static DEFINE_PER_CPU(unsigned long, wq_watchdog_touched_cpu) = INITIAL_JIFFIES;
5408 static void wq_watchdog_reset_touched(void)
5410 int cpu;
5412 wq_watchdog_touched = jiffies;
5413 for_each_possible_cpu(cpu)
5414 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5417 static void wq_watchdog_timer_fn(struct timer_list *unused)
5419 unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ;
5420 bool lockup_detected = false;
5421 struct worker_pool *pool;
5422 int pi;
5424 if (!thresh)
5425 return;
5427 rcu_read_lock();
5429 for_each_pool(pool, pi) {
5430 unsigned long pool_ts, touched, ts;
5432 if (list_empty(&pool->worklist))
5433 continue;
5435 /* get the latest of pool and touched timestamps */
5436 pool_ts = READ_ONCE(pool->watchdog_ts);
5437 touched = READ_ONCE(wq_watchdog_touched);
5439 if (time_after(pool_ts, touched))
5440 ts = pool_ts;
5441 else
5442 ts = touched;
5444 if (pool->cpu >= 0) {
5445 unsigned long cpu_touched =
5446 READ_ONCE(per_cpu(wq_watchdog_touched_cpu,
5447 pool->cpu));
5448 if (time_after(cpu_touched, ts))
5449 ts = cpu_touched;
5452 /* did we stall? */
5453 if (time_after(jiffies, ts + thresh)) {
5454 lockup_detected = true;
5455 pr_emerg("BUG: workqueue lockup - pool");
5456 pr_cont_pool_info(pool);
5457 pr_cont(" stuck for %us!\n",
5458 jiffies_to_msecs(jiffies - pool_ts) / 1000);
5462 rcu_read_unlock();
5464 if (lockup_detected)
5465 show_workqueue_state();
5467 wq_watchdog_reset_touched();
5468 mod_timer(&wq_watchdog_timer, jiffies + thresh);
5471 void wq_watchdog_touch(int cpu)
5473 if (cpu >= 0)
5474 per_cpu(wq_watchdog_touched_cpu, cpu) = jiffies;
5475 else
5476 wq_watchdog_touched = jiffies;
5479 static void wq_watchdog_set_thresh(unsigned long thresh)
5481 wq_watchdog_thresh = 0;
5482 del_timer_sync(&wq_watchdog_timer);
5484 if (thresh) {
5485 wq_watchdog_thresh = thresh;
5486 wq_watchdog_reset_touched();
5487 mod_timer(&wq_watchdog_timer, jiffies + thresh * HZ);
5491 static int wq_watchdog_param_set_thresh(const char *val,
5492 const struct kernel_param *kp)
5494 unsigned long thresh;
5495 int ret;
5497 ret = kstrtoul(val, 0, &thresh);
5498 if (ret)
5499 return ret;
5501 if (system_wq)
5502 wq_watchdog_set_thresh(thresh);
5503 else
5504 wq_watchdog_thresh = thresh;
5506 return 0;
5509 static const struct kernel_param_ops wq_watchdog_thresh_ops = {
5510 .set = wq_watchdog_param_set_thresh,
5511 .get = param_get_ulong,
5514 module_param_cb(watchdog_thresh, &wq_watchdog_thresh_ops, &wq_watchdog_thresh,
5515 0644);
5517 static void wq_watchdog_init(void)
5519 timer_setup(&wq_watchdog_timer, wq_watchdog_timer_fn, TIMER_DEFERRABLE);
5520 wq_watchdog_set_thresh(wq_watchdog_thresh);
5523 #else /* CONFIG_WQ_WATCHDOG */
5525 static inline void wq_watchdog_init(void) { }
5527 #endif /* CONFIG_WQ_WATCHDOG */
5529 static void __init wq_numa_init(void)
5531 cpumask_var_t *tbl;
5532 int node, cpu;
5534 if (num_possible_nodes() <= 1)
5535 return;
5537 if (wq_disable_numa) {
5538 pr_info("workqueue: NUMA affinity support disabled\n");
5539 return;
5542 wq_update_unbound_numa_attrs_buf = alloc_workqueue_attrs(GFP_KERNEL);
5543 BUG_ON(!wq_update_unbound_numa_attrs_buf);
5546 * We want masks of possible CPUs of each node which isn't readily
5547 * available. Build one from cpu_to_node() which should have been
5548 * fully initialized by now.
5550 tbl = kzalloc(nr_node_ids * sizeof(tbl[0]), GFP_KERNEL);
5551 BUG_ON(!tbl);
5553 for_each_node(node)
5554 BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL,
5555 node_online(node) ? node : NUMA_NO_NODE));
5557 for_each_possible_cpu(cpu) {
5558 node = cpu_to_node(cpu);
5559 if (WARN_ON(node == NUMA_NO_NODE)) {
5560 pr_warn("workqueue: NUMA node mapping not available for cpu%d, disabling NUMA support\n", cpu);
5561 /* happens iff arch is bonkers, let's just proceed */
5562 return;
5564 cpumask_set_cpu(cpu, tbl[node]);
5567 wq_numa_possible_cpumask = tbl;
5568 wq_numa_enabled = true;
5572 * workqueue_init_early - early init for workqueue subsystem
5574 * This is the first half of two-staged workqueue subsystem initialization
5575 * and invoked as soon as the bare basics - memory allocation, cpumasks and
5576 * idr are up. It sets up all the data structures and system workqueues
5577 * and allows early boot code to create workqueues and queue/cancel work
5578 * items. Actual work item execution starts only after kthreads can be
5579 * created and scheduled right before early initcalls.
5581 int __init workqueue_init_early(void)
5583 int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
5584 int i, cpu;
5586 WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
5588 BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
5589 cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(HK_FLAG_DOMAIN));
5591 pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
5593 /* initialize CPU pools */
5594 for_each_possible_cpu(cpu) {
5595 struct worker_pool *pool;
5597 i = 0;
5598 for_each_cpu_worker_pool(pool, cpu) {
5599 BUG_ON(init_worker_pool(pool));
5600 pool->cpu = cpu;
5601 cpumask_copy(pool->attrs->cpumask, cpumask_of(cpu));
5602 pool->attrs->nice = std_nice[i++];
5603 pool->node = cpu_to_node(cpu);
5605 /* alloc pool ID */
5606 mutex_lock(&wq_pool_mutex);
5607 BUG_ON(worker_pool_assign_id(pool));
5608 mutex_unlock(&wq_pool_mutex);
5612 /* create default unbound and ordered wq attrs */
5613 for (i = 0; i < NR_STD_WORKER_POOLS; i++) {
5614 struct workqueue_attrs *attrs;
5616 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5617 attrs->nice = std_nice[i];
5618 unbound_std_wq_attrs[i] = attrs;
5621 * An ordered wq should have only one pwq as ordering is
5622 * guaranteed by max_active which is enforced by pwqs.
5623 * Turn off NUMA so that dfl_pwq is used for all nodes.
5625 BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));
5626 attrs->nice = std_nice[i];
5627 attrs->no_numa = true;
5628 ordered_wq_attrs[i] = attrs;
5631 system_wq = alloc_workqueue("events", 0, 0);
5632 system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0);
5633 system_long_wq = alloc_workqueue("events_long", 0, 0);
5634 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
5635 WQ_UNBOUND_MAX_ACTIVE);
5636 system_freezable_wq = alloc_workqueue("events_freezable",
5637 WQ_FREEZABLE, 0);
5638 system_power_efficient_wq = alloc_workqueue("events_power_efficient",
5639 WQ_POWER_EFFICIENT, 0);
5640 system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_power_efficient",
5641 WQ_FREEZABLE | WQ_POWER_EFFICIENT,
5643 BUG_ON(!system_wq || !system_highpri_wq || !system_long_wq ||
5644 !system_unbound_wq || !system_freezable_wq ||
5645 !system_power_efficient_wq ||
5646 !system_freezable_power_efficient_wq);
5648 return 0;
5652 * workqueue_init - bring workqueue subsystem fully online
5654 * This is the latter half of two-staged workqueue subsystem initialization
5655 * and invoked as soon as kthreads can be created and scheduled.
5656 * Workqueues have been created and work items queued on them, but there
5657 * are no kworkers executing the work items yet. Populate the worker pools
5658 * with the initial workers and enable future kworker creations.
5660 int __init workqueue_init(void)
5662 struct workqueue_struct *wq;
5663 struct worker_pool *pool;
5664 int cpu, bkt;
5667 * It'd be simpler to initialize NUMA in workqueue_init_early() but
5668 * CPU to node mapping may not be available that early on some
5669 * archs such as power and arm64. As per-cpu pools created
5670 * previously could be missing node hint and unbound pools NUMA
5671 * affinity, fix them up.
5673 * Also, while iterating workqueues, create rescuers if requested.
5675 wq_numa_init();
5677 mutex_lock(&wq_pool_mutex);
5679 for_each_possible_cpu(cpu) {
5680 for_each_cpu_worker_pool(pool, cpu) {
5681 pool->node = cpu_to_node(cpu);
5685 list_for_each_entry(wq, &workqueues, list) {
5686 wq_update_unbound_numa(wq, smp_processor_id(), true);
5687 WARN(init_rescuer(wq),
5688 "workqueue: failed to create early rescuer for %s",
5689 wq->name);
5692 mutex_unlock(&wq_pool_mutex);
5694 /* create the initial workers */
5695 for_each_online_cpu(cpu) {
5696 for_each_cpu_worker_pool(pool, cpu) {
5697 pool->flags &= ~POOL_DISASSOCIATED;
5698 BUG_ON(!create_worker(pool));
5702 hash_for_each(unbound_pool_hash, bkt, pool, hash_node)
5703 BUG_ON(!create_worker(pool));
5705 wq_online = true;
5706 wq_watchdog_init();
5708 return 0;