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>
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 is one worker pool for each CPU and
20 * one extra for works which are better served by workers which are
21 * not bound to any specific CPU.
23 * Please read Documentation/workqueue.txt for details.
26 #include <linux/export.h>
27 #include <linux/kernel.h>
28 #include <linux/sched.h>
29 #include <linux/init.h>
30 #include <linux/signal.h>
31 #include <linux/completion.h>
32 #include <linux/workqueue.h>
33 #include <linux/slab.h>
34 #include <linux/cpu.h>
35 #include <linux/notifier.h>
36 #include <linux/kthread.h>
37 #include <linux/hardirq.h>
38 #include <linux/mempolicy.h>
39 #include <linux/freezer.h>
40 #include <linux/kallsyms.h>
41 #include <linux/debug_locks.h>
42 #include <linux/lockdep.h>
43 #include <linux/idr.h>
45 #include "workqueue_sched.h"
48 /* global_cwq flags */
49 GCWQ_DISASSOCIATED = 1 << 0, /* cpu can't serve workers */
50 GCWQ_FREEZING = 1 << 1, /* freeze in progress */
53 POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
54 POOL_MANAGING_WORKERS = 1 << 1, /* managing workers */
57 WORKER_STARTED = 1 << 0, /* started */
58 WORKER_DIE = 1 << 1, /* die die die */
59 WORKER_IDLE = 1 << 2, /* is idle */
60 WORKER_PREP = 1 << 3, /* preparing to run works */
61 WORKER_ROGUE = 1 << 4, /* not bound to any cpu */
62 WORKER_REBIND = 1 << 5, /* mom is home, come back */
63 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
64 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
66 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_ROGUE | WORKER_REBIND |
67 WORKER_CPU_INTENSIVE | WORKER_UNBOUND,
69 /* gcwq->trustee_state */
70 TRUSTEE_START = 0, /* start */
71 TRUSTEE_IN_CHARGE = 1, /* trustee in charge of gcwq */
72 TRUSTEE_BUTCHER = 2, /* butcher workers */
73 TRUSTEE_RELEASE = 3, /* release workers */
74 TRUSTEE_DONE = 4, /* trustee is done */
76 NR_WORKER_POOLS = 2, /* # worker pools per gcwq */
78 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
79 BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER,
80 BUSY_WORKER_HASH_MASK = BUSY_WORKER_HASH_SIZE - 1,
82 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
83 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
85 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
86 /* call for help after 10ms
88 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
89 CREATE_COOLDOWN = HZ, /* time to breath after fail */
90 TRUSTEE_COOLDOWN = HZ / 10, /* for trustee draining */
93 * Rescue workers are used only on emergencies and shared by
96 RESCUER_NICE_LEVEL = -20,
97 HIGHPRI_NICE_LEVEL = -20,
101 * Structure fields follow one of the following exclusion rules.
103 * I: Modifiable by initialization/destruction paths and read-only for
106 * P: Preemption protected. Disabling preemption is enough and should
107 * only be modified and accessed from the local cpu.
109 * L: gcwq->lock protected. Access with gcwq->lock held.
111 * X: During normal operation, modification requires gcwq->lock and
112 * should be done only from local cpu. Either disabling preemption
113 * on local cpu or grabbing gcwq->lock is enough for read access.
114 * If GCWQ_DISASSOCIATED is set, it's identical to L.
116 * F: wq->flush_mutex protected.
118 * W: workqueue_lock protected.
125 * The poor guys doing the actual heavy lifting. All on-duty workers
126 * are either serving the manager role, on idle list or on busy hash.
129 /* on idle list while idle, on busy hash table while busy */
131 struct list_head entry; /* L: while idle */
132 struct hlist_node hentry; /* L: while busy */
135 struct work_struct *current_work; /* L: work being processed */
136 struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */
137 struct list_head scheduled; /* L: scheduled works */
138 struct task_struct *task; /* I: worker task */
139 struct worker_pool *pool; /* I: the associated pool */
140 /* 64 bytes boundary on 64bit, 32 on 32bit */
141 unsigned long last_active; /* L: last active timestamp */
142 unsigned int flags; /* X: flags */
143 int id; /* I: worker id */
144 struct work_struct rebind_work; /* L: rebind worker to cpu */
148 struct global_cwq *gcwq; /* I: the owning gcwq */
149 unsigned int flags; /* X: flags */
151 struct list_head worklist; /* L: list of pending works */
152 int nr_workers; /* L: total number of workers */
153 int nr_idle; /* L: currently idle ones */
155 struct list_head idle_list; /* X: list of idle workers */
156 struct timer_list idle_timer; /* L: worker idle timeout */
157 struct timer_list mayday_timer; /* L: SOS timer for workers */
159 struct ida worker_ida; /* L: for worker IDs */
160 struct worker *first_idle; /* L: first idle worker */
164 * Global per-cpu workqueue. There's one and only one for each cpu
165 * and all works are queued and processed here regardless of their
169 spinlock_t lock; /* the gcwq lock */
170 unsigned int cpu; /* I: the associated cpu */
171 unsigned int flags; /* L: GCWQ_* flags */
173 /* workers are chained either in busy_hash or pool idle_list */
174 struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE];
175 /* L: hash of busy workers */
177 struct worker_pool pools[2]; /* normal and highpri pools */
179 struct task_struct *trustee; /* L: for gcwq shutdown */
180 unsigned int trustee_state; /* L: trustee state */
181 wait_queue_head_t trustee_wait; /* trustee wait */
182 } ____cacheline_aligned_in_smp;
185 * The per-CPU workqueue. The lower WORK_STRUCT_FLAG_BITS of
186 * work_struct->data are used for flags and thus cwqs need to be
187 * aligned at two's power of the number of flag bits.
189 struct cpu_workqueue_struct {
190 struct worker_pool *pool; /* I: the associated pool */
191 struct workqueue_struct *wq; /* I: the owning workqueue */
192 int work_color; /* L: current color */
193 int flush_color; /* L: flushing color */
194 int nr_in_flight[WORK_NR_COLORS];
195 /* L: nr of in_flight works */
196 int nr_active; /* L: nr of active works */
197 int max_active; /* L: max active works */
198 struct list_head delayed_works; /* L: delayed works */
202 * Structure used to wait for workqueue flush.
205 struct list_head list; /* F: list of flushers */
206 int flush_color; /* F: flush color waiting for */
207 struct completion done; /* flush completion */
211 * All cpumasks are assumed to be always set on UP and thus can't be
212 * used to determine whether there's something to be done.
215 typedef cpumask_var_t mayday_mask_t;
216 #define mayday_test_and_set_cpu(cpu, mask) \
217 cpumask_test_and_set_cpu((cpu), (mask))
218 #define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask))
219 #define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask))
220 #define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp))
221 #define free_mayday_mask(mask) free_cpumask_var((mask))
223 typedef unsigned long mayday_mask_t;
224 #define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask))
225 #define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask))
226 #define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask))
227 #define alloc_mayday_mask(maskp, gfp) true
228 #define free_mayday_mask(mask) do { } while (0)
232 * The externally visible workqueue abstraction is an array of
233 * per-CPU workqueues:
235 struct workqueue_struct {
236 unsigned int flags; /* W: WQ_* flags */
238 struct cpu_workqueue_struct __percpu *pcpu;
239 struct cpu_workqueue_struct *single;
241 } cpu_wq; /* I: cwq's */
242 struct list_head list; /* W: list of all workqueues */
244 struct mutex flush_mutex; /* protects wq flushing */
245 int work_color; /* F: current work color */
246 int flush_color; /* F: current flush color */
247 atomic_t nr_cwqs_to_flush; /* flush in progress */
248 struct wq_flusher *first_flusher; /* F: first flusher */
249 struct list_head flusher_queue; /* F: flush waiters */
250 struct list_head flusher_overflow; /* F: flush overflow list */
252 mayday_mask_t mayday_mask; /* cpus requesting rescue */
253 struct worker *rescuer; /* I: rescue worker */
255 int nr_drainers; /* W: drain in progress */
256 int saved_max_active; /* W: saved cwq max_active */
257 #ifdef CONFIG_LOCKDEP
258 struct lockdep_map lockdep_map;
260 char name[]; /* I: workqueue name */
263 struct workqueue_struct *system_wq __read_mostly;
264 struct workqueue_struct *system_long_wq __read_mostly;
265 struct workqueue_struct *system_nrt_wq __read_mostly;
266 struct workqueue_struct *system_unbound_wq __read_mostly;
267 struct workqueue_struct *system_freezable_wq __read_mostly;
268 struct workqueue_struct *system_nrt_freezable_wq __read_mostly;
269 EXPORT_SYMBOL_GPL(system_wq);
270 EXPORT_SYMBOL_GPL(system_long_wq);
271 EXPORT_SYMBOL_GPL(system_nrt_wq);
272 EXPORT_SYMBOL_GPL(system_unbound_wq);
273 EXPORT_SYMBOL_GPL(system_freezable_wq);
274 EXPORT_SYMBOL_GPL(system_nrt_freezable_wq);
276 #define CREATE_TRACE_POINTS
277 #include <trace/events/workqueue.h>
279 #define for_each_worker_pool(pool, gcwq) \
280 for ((pool) = &(gcwq)->pools[0]; \
281 (pool) < &(gcwq)->pools[NR_WORKER_POOLS]; (pool)++)
283 #define for_each_busy_worker(worker, i, pos, gcwq) \
284 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \
285 hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)
287 static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask,
290 if (cpu < nr_cpu_ids) {
292 cpu = cpumask_next(cpu, mask);
293 if (cpu < nr_cpu_ids)
297 return WORK_CPU_UNBOUND;
299 return WORK_CPU_NONE;
302 static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
303 struct workqueue_struct *wq)
305 return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2);
311 * An extra gcwq is defined for an invalid cpu number
312 * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
313 * specific CPU. The following iterators are similar to
314 * for_each_*_cpu() iterators but also considers the unbound gcwq.
316 * for_each_gcwq_cpu() : possible CPUs + WORK_CPU_UNBOUND
317 * for_each_online_gcwq_cpu() : online CPUs + WORK_CPU_UNBOUND
318 * for_each_cwq_cpu() : possible CPUs for bound workqueues,
319 * WORK_CPU_UNBOUND for unbound workqueues
321 #define for_each_gcwq_cpu(cpu) \
322 for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3); \
323 (cpu) < WORK_CPU_NONE; \
324 (cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3))
326 #define for_each_online_gcwq_cpu(cpu) \
327 for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3); \
328 (cpu) < WORK_CPU_NONE; \
329 (cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3))
331 #define for_each_cwq_cpu(cpu, wq) \
332 for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq)); \
333 (cpu) < WORK_CPU_NONE; \
334 (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq)))
336 #ifdef CONFIG_DEBUG_OBJECTS_WORK
338 static struct debug_obj_descr work_debug_descr;
340 static void *work_debug_hint(void *addr)
342 return ((struct work_struct *) addr)->func;
346 * fixup_init is called when:
347 * - an active object is initialized
349 static int work_fixup_init(void *addr, enum debug_obj_state state)
351 struct work_struct *work = addr;
354 case ODEBUG_STATE_ACTIVE:
355 cancel_work_sync(work);
356 debug_object_init(work, &work_debug_descr);
364 * fixup_activate is called when:
365 * - an active object is activated
366 * - an unknown object is activated (might be a statically initialized object)
368 static int work_fixup_activate(void *addr, enum debug_obj_state state)
370 struct work_struct *work = addr;
374 case ODEBUG_STATE_NOTAVAILABLE:
376 * This is not really a fixup. The work struct was
377 * statically initialized. We just make sure that it
378 * is tracked in the object tracker.
380 if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
381 debug_object_init(work, &work_debug_descr);
382 debug_object_activate(work, &work_debug_descr);
388 case ODEBUG_STATE_ACTIVE:
397 * fixup_free is called when:
398 * - an active object is freed
400 static int work_fixup_free(void *addr, enum debug_obj_state state)
402 struct work_struct *work = addr;
405 case ODEBUG_STATE_ACTIVE:
406 cancel_work_sync(work);
407 debug_object_free(work, &work_debug_descr);
414 static struct debug_obj_descr work_debug_descr = {
415 .name = "work_struct",
416 .debug_hint = work_debug_hint,
417 .fixup_init = work_fixup_init,
418 .fixup_activate = work_fixup_activate,
419 .fixup_free = work_fixup_free,
422 static inline void debug_work_activate(struct work_struct *work)
424 debug_object_activate(work, &work_debug_descr);
427 static inline void debug_work_deactivate(struct work_struct *work)
429 debug_object_deactivate(work, &work_debug_descr);
432 void __init_work(struct work_struct *work, int onstack)
435 debug_object_init_on_stack(work, &work_debug_descr);
437 debug_object_init(work, &work_debug_descr);
439 EXPORT_SYMBOL_GPL(__init_work);
441 void destroy_work_on_stack(struct work_struct *work)
443 debug_object_free(work, &work_debug_descr);
445 EXPORT_SYMBOL_GPL(destroy_work_on_stack);
448 static inline void debug_work_activate(struct work_struct *work) { }
449 static inline void debug_work_deactivate(struct work_struct *work) { }
452 /* Serializes the accesses to the list of workqueues. */
453 static DEFINE_SPINLOCK(workqueue_lock);
454 static LIST_HEAD(workqueues);
455 static bool workqueue_freezing; /* W: have wqs started freezing? */
458 * The almighty global cpu workqueues. nr_running is the only field
459 * which is expected to be used frequently by other cpus via
460 * try_to_wake_up(). Put it in a separate cacheline.
462 static DEFINE_PER_CPU(struct global_cwq, global_cwq);
463 static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, pool_nr_running[NR_WORKER_POOLS]);
466 * Global cpu workqueue and nr_running counter for unbound gcwq. The
467 * gcwq is always online, has GCWQ_DISASSOCIATED set, and all its
468 * workers have WORKER_UNBOUND set.
470 static struct global_cwq unbound_global_cwq;
471 static atomic_t unbound_pool_nr_running[NR_WORKER_POOLS] = {
472 [0 ... NR_WORKER_POOLS - 1] = ATOMIC_INIT(0), /* always 0 */
475 static int worker_thread(void *__worker);
477 static int worker_pool_pri(struct worker_pool *pool)
479 return pool - pool->gcwq->pools;
482 static struct global_cwq *get_gcwq(unsigned int cpu)
484 if (cpu != WORK_CPU_UNBOUND)
485 return &per_cpu(global_cwq, cpu);
487 return &unbound_global_cwq;
490 static atomic_t *get_pool_nr_running(struct worker_pool *pool)
492 int cpu = pool->gcwq->cpu;
493 int idx = worker_pool_pri(pool);
495 if (cpu != WORK_CPU_UNBOUND)
496 return &per_cpu(pool_nr_running, cpu)[idx];
498 return &unbound_pool_nr_running[idx];
501 static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
502 struct workqueue_struct *wq)
504 if (!(wq->flags & WQ_UNBOUND)) {
505 if (likely(cpu < nr_cpu_ids))
506 return per_cpu_ptr(wq->cpu_wq.pcpu, cpu);
507 } else if (likely(cpu == WORK_CPU_UNBOUND))
508 return wq->cpu_wq.single;
512 static unsigned int work_color_to_flags(int color)
514 return color << WORK_STRUCT_COLOR_SHIFT;
517 static int get_work_color(struct work_struct *work)
519 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
520 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
523 static int work_next_color(int color)
525 return (color + 1) % WORK_NR_COLORS;
529 * A work's data points to the cwq with WORK_STRUCT_CWQ set while the
530 * work is on queue. Once execution starts, WORK_STRUCT_CWQ is
531 * cleared and the work data contains the cpu number it was last on.
533 * set_work_{cwq|cpu}() and clear_work_data() can be used to set the
534 * cwq, cpu or clear work->data. These functions should only be
535 * called while the work is owned - ie. while the PENDING bit is set.
537 * get_work_[g]cwq() can be used to obtain the gcwq or cwq
538 * corresponding to a work. gcwq is available once the work has been
539 * queued anywhere after initialization. cwq is available only from
540 * queueing until execution starts.
542 static inline void set_work_data(struct work_struct *work, unsigned long data,
545 BUG_ON(!work_pending(work));
546 atomic_long_set(&work->data, data | flags | work_static(work));
549 static void set_work_cwq(struct work_struct *work,
550 struct cpu_workqueue_struct *cwq,
551 unsigned long extra_flags)
553 set_work_data(work, (unsigned long)cwq,
554 WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags);
557 static void set_work_cpu(struct work_struct *work, unsigned int cpu)
559 set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, WORK_STRUCT_PENDING);
562 static void clear_work_data(struct work_struct *work)
564 set_work_data(work, WORK_STRUCT_NO_CPU, 0);
567 static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work)
569 unsigned long data = atomic_long_read(&work->data);
571 if (data & WORK_STRUCT_CWQ)
572 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
577 static struct global_cwq *get_work_gcwq(struct work_struct *work)
579 unsigned long data = atomic_long_read(&work->data);
582 if (data & WORK_STRUCT_CWQ)
583 return ((struct cpu_workqueue_struct *)
584 (data & WORK_STRUCT_WQ_DATA_MASK))->pool->gcwq;
586 cpu = data >> WORK_STRUCT_FLAG_BITS;
587 if (cpu == WORK_CPU_NONE)
590 BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND);
591 return get_gcwq(cpu);
595 * Policy functions. These define the policies on how the global worker
596 * pools are managed. Unless noted otherwise, these functions assume that
597 * they're being called with gcwq->lock held.
600 static bool __need_more_worker(struct worker_pool *pool)
602 return !atomic_read(get_pool_nr_running(pool));
606 * Need to wake up a worker? Called from anything but currently
609 * Note that, because unbound workers never contribute to nr_running, this
610 * function will always return %true for unbound gcwq as long as the
611 * worklist isn't empty.
613 static bool need_more_worker(struct worker_pool *pool)
615 return !list_empty(&pool->worklist) && __need_more_worker(pool);
618 /* Can I start working? Called from busy but !running workers. */
619 static bool may_start_working(struct worker_pool *pool)
621 return pool->nr_idle;
624 /* Do I need to keep working? Called from currently running workers. */
625 static bool keep_working(struct worker_pool *pool)
627 atomic_t *nr_running = get_pool_nr_running(pool);
629 return !list_empty(&pool->worklist) && atomic_read(nr_running) <= 1;
632 /* Do we need a new worker? Called from manager. */
633 static bool need_to_create_worker(struct worker_pool *pool)
635 return need_more_worker(pool) && !may_start_working(pool);
638 /* Do I need to be the manager? */
639 static bool need_to_manage_workers(struct worker_pool *pool)
641 return need_to_create_worker(pool) ||
642 (pool->flags & POOL_MANAGE_WORKERS);
645 /* Do we have too many workers and should some go away? */
646 static bool too_many_workers(struct worker_pool *pool)
648 bool managing = pool->flags & POOL_MANAGING_WORKERS;
649 int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
650 int nr_busy = pool->nr_workers - nr_idle;
652 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
659 /* Return the first worker. Safe with preemption disabled */
660 static struct worker *first_worker(struct worker_pool *pool)
662 if (unlikely(list_empty(&pool->idle_list)))
665 return list_first_entry(&pool->idle_list, struct worker, entry);
669 * wake_up_worker - wake up an idle worker
670 * @pool: worker pool to wake worker from
672 * Wake up the first idle worker of @pool.
675 * spin_lock_irq(gcwq->lock).
677 static void wake_up_worker(struct worker_pool *pool)
679 struct worker *worker = first_worker(pool);
682 wake_up_process(worker->task);
686 * wq_worker_waking_up - a worker is waking up
687 * @task: task waking up
688 * @cpu: CPU @task is waking up to
690 * This function is called during try_to_wake_up() when a worker is
694 * spin_lock_irq(rq->lock)
696 void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
698 struct worker *worker = kthread_data(task);
700 if (!(worker->flags & WORKER_NOT_RUNNING))
701 atomic_inc(get_pool_nr_running(worker->pool));
705 * wq_worker_sleeping - a worker is going to sleep
706 * @task: task going to sleep
707 * @cpu: CPU in question, must be the current CPU number
709 * This function is called during schedule() when a busy worker is
710 * going to sleep. Worker on the same cpu can be woken up by
711 * returning pointer to its task.
714 * spin_lock_irq(rq->lock)
717 * Worker task on @cpu to wake up, %NULL if none.
719 struct task_struct *wq_worker_sleeping(struct task_struct *task,
722 struct worker *worker = kthread_data(task), *to_wakeup = NULL;
723 struct worker_pool *pool = worker->pool;
724 atomic_t *nr_running = get_pool_nr_running(pool);
726 if (worker->flags & WORKER_NOT_RUNNING)
729 /* this can only happen on the local cpu */
730 BUG_ON(cpu != raw_smp_processor_id());
733 * The counterpart of the following dec_and_test, implied mb,
734 * worklist not empty test sequence is in insert_work().
735 * Please read comment there.
737 * NOT_RUNNING is clear. This means that trustee is not in
738 * charge and we're running on the local cpu w/ rq lock held
739 * and preemption disabled, which in turn means that none else
740 * could be manipulating idle_list, so dereferencing idle_list
741 * without gcwq lock is safe.
743 if (atomic_dec_and_test(nr_running) && !list_empty(&pool->worklist))
744 to_wakeup = first_worker(pool);
745 return to_wakeup ? to_wakeup->task : NULL;
749 * worker_set_flags - set worker flags and adjust nr_running accordingly
751 * @flags: flags to set
752 * @wakeup: wakeup an idle worker if necessary
754 * Set @flags in @worker->flags and adjust nr_running accordingly. If
755 * nr_running becomes zero and @wakeup is %true, an idle worker is
759 * spin_lock_irq(gcwq->lock)
761 static inline void worker_set_flags(struct worker *worker, unsigned int flags,
764 struct worker_pool *pool = worker->pool;
766 WARN_ON_ONCE(worker->task != current);
769 * If transitioning into NOT_RUNNING, adjust nr_running and
770 * wake up an idle worker as necessary if requested by
773 if ((flags & WORKER_NOT_RUNNING) &&
774 !(worker->flags & WORKER_NOT_RUNNING)) {
775 atomic_t *nr_running = get_pool_nr_running(pool);
778 if (atomic_dec_and_test(nr_running) &&
779 !list_empty(&pool->worklist))
780 wake_up_worker(pool);
782 atomic_dec(nr_running);
785 worker->flags |= flags;
789 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
791 * @flags: flags to clear
793 * Clear @flags in @worker->flags and adjust nr_running accordingly.
796 * spin_lock_irq(gcwq->lock)
798 static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
800 struct worker_pool *pool = worker->pool;
801 unsigned int oflags = worker->flags;
803 WARN_ON_ONCE(worker->task != current);
805 worker->flags &= ~flags;
808 * If transitioning out of NOT_RUNNING, increment nr_running. Note
809 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
810 * of multiple flags, not a single flag.
812 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
813 if (!(worker->flags & WORKER_NOT_RUNNING))
814 atomic_inc(get_pool_nr_running(pool));
818 * busy_worker_head - return the busy hash head for a work
819 * @gcwq: gcwq of interest
820 * @work: work to be hashed
822 * Return hash head of @gcwq for @work.
825 * spin_lock_irq(gcwq->lock).
828 * Pointer to the hash head.
830 static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
831 struct work_struct *work)
833 const int base_shift = ilog2(sizeof(struct work_struct));
834 unsigned long v = (unsigned long)work;
836 /* simple shift and fold hash, do we need something better? */
838 v += v >> BUSY_WORKER_HASH_ORDER;
839 v &= BUSY_WORKER_HASH_MASK;
841 return &gcwq->busy_hash[v];
845 * __find_worker_executing_work - find worker which is executing a work
846 * @gcwq: gcwq of interest
847 * @bwh: hash head as returned by busy_worker_head()
848 * @work: work to find worker for
850 * Find a worker which is executing @work on @gcwq. @bwh should be
851 * the hash head obtained by calling busy_worker_head() with the same
855 * spin_lock_irq(gcwq->lock).
858 * Pointer to worker which is executing @work if found, NULL
861 static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
862 struct hlist_head *bwh,
863 struct work_struct *work)
865 struct worker *worker;
866 struct hlist_node *tmp;
868 hlist_for_each_entry(worker, tmp, bwh, hentry)
869 if (worker->current_work == work)
875 * find_worker_executing_work - find worker which is executing a work
876 * @gcwq: gcwq of interest
877 * @work: work to find worker for
879 * Find a worker which is executing @work on @gcwq. This function is
880 * identical to __find_worker_executing_work() except that this
881 * function calculates @bwh itself.
884 * spin_lock_irq(gcwq->lock).
887 * Pointer to worker which is executing @work if found, NULL
890 static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
891 struct work_struct *work)
893 return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
898 * insert_work - insert a work into gcwq
899 * @cwq: cwq @work belongs to
900 * @work: work to insert
901 * @head: insertion point
902 * @extra_flags: extra WORK_STRUCT_* flags to set
904 * Insert @work which belongs to @cwq into @gcwq after @head.
905 * @extra_flags is or'd to work_struct flags.
908 * spin_lock_irq(gcwq->lock).
910 static void insert_work(struct cpu_workqueue_struct *cwq,
911 struct work_struct *work, struct list_head *head,
912 unsigned int extra_flags)
914 struct worker_pool *pool = cwq->pool;
916 /* we own @work, set data and link */
917 set_work_cwq(work, cwq, extra_flags);
920 * Ensure that we get the right work->data if we see the
921 * result of list_add() below, see try_to_grab_pending().
925 list_add_tail(&work->entry, head);
928 * Ensure either worker_sched_deactivated() sees the above
929 * list_add_tail() or we see zero nr_running to avoid workers
930 * lying around lazily while there are works to be processed.
934 if (__need_more_worker(pool))
935 wake_up_worker(pool);
939 * Test whether @work is being queued from another work executing on the
940 * same workqueue. This is rather expensive and should only be used from
943 static bool is_chained_work(struct workqueue_struct *wq)
948 for_each_gcwq_cpu(cpu) {
949 struct global_cwq *gcwq = get_gcwq(cpu);
950 struct worker *worker;
951 struct hlist_node *pos;
954 spin_lock_irqsave(&gcwq->lock, flags);
955 for_each_busy_worker(worker, i, pos, gcwq) {
956 if (worker->task != current)
958 spin_unlock_irqrestore(&gcwq->lock, flags);
960 * I'm @worker, no locking necessary. See if @work
961 * is headed to the same workqueue.
963 return worker->current_cwq->wq == wq;
965 spin_unlock_irqrestore(&gcwq->lock, flags);
970 static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
971 struct work_struct *work)
973 struct global_cwq *gcwq;
974 struct cpu_workqueue_struct *cwq;
975 struct list_head *worklist;
976 unsigned int work_flags;
979 debug_work_activate(work);
981 /* if dying, only works from the same workqueue are allowed */
982 if (unlikely(wq->flags & WQ_DRAINING) &&
983 WARN_ON_ONCE(!is_chained_work(wq)))
986 /* determine gcwq to use */
987 if (!(wq->flags & WQ_UNBOUND)) {
988 struct global_cwq *last_gcwq;
990 if (unlikely(cpu == WORK_CPU_UNBOUND))
991 cpu = raw_smp_processor_id();
994 * It's multi cpu. If @wq is non-reentrant and @work
995 * was previously on a different cpu, it might still
996 * be running there, in which case the work needs to
997 * be queued on that cpu to guarantee non-reentrance.
999 gcwq = get_gcwq(cpu);
1000 if (wq->flags & WQ_NON_REENTRANT &&
1001 (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {
1002 struct worker *worker;
1004 spin_lock_irqsave(&last_gcwq->lock, flags);
1006 worker = find_worker_executing_work(last_gcwq, work);
1008 if (worker && worker->current_cwq->wq == wq)
1011 /* meh... not running there, queue here */
1012 spin_unlock_irqrestore(&last_gcwq->lock, flags);
1013 spin_lock_irqsave(&gcwq->lock, flags);
1016 spin_lock_irqsave(&gcwq->lock, flags);
1018 gcwq = get_gcwq(WORK_CPU_UNBOUND);
1019 spin_lock_irqsave(&gcwq->lock, flags);
1022 /* gcwq determined, get cwq and queue */
1023 cwq = get_cwq(gcwq->cpu, wq);
1024 trace_workqueue_queue_work(cpu, cwq, work);
1026 if (WARN_ON(!list_empty(&work->entry))) {
1027 spin_unlock_irqrestore(&gcwq->lock, flags);
1031 cwq->nr_in_flight[cwq->work_color]++;
1032 work_flags = work_color_to_flags(cwq->work_color);
1034 if (likely(cwq->nr_active < cwq->max_active)) {
1035 trace_workqueue_activate_work(work);
1037 worklist = &cwq->pool->worklist;
1039 work_flags |= WORK_STRUCT_DELAYED;
1040 worklist = &cwq->delayed_works;
1043 insert_work(cwq, work, worklist, work_flags);
1045 spin_unlock_irqrestore(&gcwq->lock, flags);
1049 * queue_work - queue work on a workqueue
1050 * @wq: workqueue to use
1051 * @work: work to queue
1053 * Returns 0 if @work was already on a queue, non-zero otherwise.
1055 * We queue the work to the CPU on which it was submitted, but if the CPU dies
1056 * it can be processed by another CPU.
1058 int queue_work(struct workqueue_struct *wq, struct work_struct *work)
1062 ret = queue_work_on(get_cpu(), wq, work);
1067 EXPORT_SYMBOL_GPL(queue_work);
1070 * queue_work_on - queue work on specific cpu
1071 * @cpu: CPU number to execute work on
1072 * @wq: workqueue to use
1073 * @work: work to queue
1075 * Returns 0 if @work was already on a queue, non-zero otherwise.
1077 * We queue the work to a specific CPU, the caller must ensure it
1081 queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
1085 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1086 __queue_work(cpu, wq, work);
1091 EXPORT_SYMBOL_GPL(queue_work_on);
1093 static void delayed_work_timer_fn(unsigned long __data)
1095 struct delayed_work *dwork = (struct delayed_work *)__data;
1096 struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
1098 __queue_work(smp_processor_id(), cwq->wq, &dwork->work);
1102 * queue_delayed_work - queue work on a workqueue after delay
1103 * @wq: workqueue to use
1104 * @dwork: delayable work to queue
1105 * @delay: number of jiffies to wait before queueing
1107 * Returns 0 if @work was already on a queue, non-zero otherwise.
1109 int queue_delayed_work(struct workqueue_struct *wq,
1110 struct delayed_work *dwork, unsigned long delay)
1113 return queue_work(wq, &dwork->work);
1115 return queue_delayed_work_on(-1, wq, dwork, delay);
1117 EXPORT_SYMBOL_GPL(queue_delayed_work);
1120 * queue_delayed_work_on - queue work on specific CPU after delay
1121 * @cpu: CPU number to execute work on
1122 * @wq: workqueue to use
1123 * @dwork: work to queue
1124 * @delay: number of jiffies to wait before queueing
1126 * Returns 0 if @work was already on a queue, non-zero otherwise.
1128 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1129 struct delayed_work *dwork, unsigned long delay)
1132 struct timer_list *timer = &dwork->timer;
1133 struct work_struct *work = &dwork->work;
1135 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1138 BUG_ON(timer_pending(timer));
1139 BUG_ON(!list_empty(&work->entry));
1141 timer_stats_timer_set_start_info(&dwork->timer);
1144 * This stores cwq for the moment, for the timer_fn.
1145 * Note that the work's gcwq is preserved to allow
1146 * reentrance detection for delayed works.
1148 if (!(wq->flags & WQ_UNBOUND)) {
1149 struct global_cwq *gcwq = get_work_gcwq(work);
1151 if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND)
1154 lcpu = raw_smp_processor_id();
1156 lcpu = WORK_CPU_UNBOUND;
1158 set_work_cwq(work, get_cwq(lcpu, wq), 0);
1160 timer->expires = jiffies + delay;
1161 timer->data = (unsigned long)dwork;
1162 timer->function = delayed_work_timer_fn;
1164 if (unlikely(cpu >= 0))
1165 add_timer_on(timer, cpu);
1172 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
1175 * worker_enter_idle - enter idle state
1176 * @worker: worker which is entering idle state
1178 * @worker is entering idle state. Update stats and idle timer if
1182 * spin_lock_irq(gcwq->lock).
1184 static void worker_enter_idle(struct worker *worker)
1186 struct worker_pool *pool = worker->pool;
1187 struct global_cwq *gcwq = pool->gcwq;
1189 BUG_ON(worker->flags & WORKER_IDLE);
1190 BUG_ON(!list_empty(&worker->entry) &&
1191 (worker->hentry.next || worker->hentry.pprev));
1193 /* can't use worker_set_flags(), also called from start_worker() */
1194 worker->flags |= WORKER_IDLE;
1196 worker->last_active = jiffies;
1198 /* idle_list is LIFO */
1199 list_add(&worker->entry, &pool->idle_list);
1201 if (likely(!(worker->flags & WORKER_ROGUE))) {
1202 if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
1203 mod_timer(&pool->idle_timer,
1204 jiffies + IDLE_WORKER_TIMEOUT);
1206 wake_up_all(&gcwq->trustee_wait);
1209 * Sanity check nr_running. Because trustee releases gcwq->lock
1210 * between setting %WORKER_ROGUE and zapping nr_running, the
1211 * warning may trigger spuriously. Check iff trustee is idle.
1213 WARN_ON_ONCE(gcwq->trustee_state == TRUSTEE_DONE &&
1214 pool->nr_workers == pool->nr_idle &&
1215 atomic_read(get_pool_nr_running(pool)));
1219 * worker_leave_idle - leave idle state
1220 * @worker: worker which is leaving idle state
1222 * @worker is leaving idle state. Update stats.
1225 * spin_lock_irq(gcwq->lock).
1227 static void worker_leave_idle(struct worker *worker)
1229 struct worker_pool *pool = worker->pool;
1231 BUG_ON(!(worker->flags & WORKER_IDLE));
1232 worker_clr_flags(worker, WORKER_IDLE);
1234 list_del_init(&worker->entry);
1238 * worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq
1241 * Works which are scheduled while the cpu is online must at least be
1242 * scheduled to a worker which is bound to the cpu so that if they are
1243 * flushed from cpu callbacks while cpu is going down, they are
1244 * guaranteed to execute on the cpu.
1246 * This function is to be used by rogue workers and rescuers to bind
1247 * themselves to the target cpu and may race with cpu going down or
1248 * coming online. kthread_bind() can't be used because it may put the
1249 * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
1250 * verbatim as it's best effort and blocking and gcwq may be
1251 * [dis]associated in the meantime.
1253 * This function tries set_cpus_allowed() and locks gcwq and verifies
1254 * the binding against GCWQ_DISASSOCIATED which is set during
1255 * CPU_DYING and cleared during CPU_ONLINE, so if the worker enters
1256 * idle state or fetches works without dropping lock, it can guarantee
1257 * the scheduling requirement described in the first paragraph.
1260 * Might sleep. Called without any lock but returns with gcwq->lock
1264 * %true if the associated gcwq is online (@worker is successfully
1265 * bound), %false if offline.
1267 static bool worker_maybe_bind_and_lock(struct worker *worker)
1268 __acquires(&gcwq->lock)
1270 struct global_cwq *gcwq = worker->pool->gcwq;
1271 struct task_struct *task = worker->task;
1275 * The following call may fail, succeed or succeed
1276 * without actually migrating the task to the cpu if
1277 * it races with cpu hotunplug operation. Verify
1278 * against GCWQ_DISASSOCIATED.
1280 if (!(gcwq->flags & GCWQ_DISASSOCIATED))
1281 set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu));
1283 spin_lock_irq(&gcwq->lock);
1284 if (gcwq->flags & GCWQ_DISASSOCIATED)
1286 if (task_cpu(task) == gcwq->cpu &&
1287 cpumask_equal(¤t->cpus_allowed,
1288 get_cpu_mask(gcwq->cpu)))
1290 spin_unlock_irq(&gcwq->lock);
1293 * We've raced with CPU hot[un]plug. Give it a breather
1294 * and retry migration. cond_resched() is required here;
1295 * otherwise, we might deadlock against cpu_stop trying to
1296 * bring down the CPU on non-preemptive kernel.
1304 * Function for worker->rebind_work used to rebind rogue busy workers
1305 * to the associated cpu which is coming back online. This is
1306 * scheduled by cpu up but can race with other cpu hotplug operations
1307 * and may be executed twice without intervening cpu down.
1309 static void worker_rebind_fn(struct work_struct *work)
1311 struct worker *worker = container_of(work, struct worker, rebind_work);
1312 struct global_cwq *gcwq = worker->pool->gcwq;
1314 if (worker_maybe_bind_and_lock(worker))
1315 worker_clr_flags(worker, WORKER_REBIND);
1317 spin_unlock_irq(&gcwq->lock);
1320 static struct worker *alloc_worker(void)
1322 struct worker *worker;
1324 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
1326 INIT_LIST_HEAD(&worker->entry);
1327 INIT_LIST_HEAD(&worker->scheduled);
1328 INIT_WORK(&worker->rebind_work, worker_rebind_fn);
1329 /* on creation a worker is in !idle && prep state */
1330 worker->flags = WORKER_PREP;
1336 * create_worker - create a new workqueue worker
1337 * @pool: pool the new worker will belong to
1338 * @bind: whether to set affinity to @cpu or not
1340 * Create a new worker which is bound to @pool. The returned worker
1341 * can be started by calling start_worker() or destroyed using
1345 * Might sleep. Does GFP_KERNEL allocations.
1348 * Pointer to the newly created worker.
1350 static struct worker *create_worker(struct worker_pool *pool, bool bind)
1352 struct global_cwq *gcwq = pool->gcwq;
1353 bool on_unbound_cpu = gcwq->cpu == WORK_CPU_UNBOUND;
1354 const char *pri = worker_pool_pri(pool) ? "H" : "";
1355 struct worker *worker = NULL;
1358 spin_lock_irq(&gcwq->lock);
1359 while (ida_get_new(&pool->worker_ida, &id)) {
1360 spin_unlock_irq(&gcwq->lock);
1361 if (!ida_pre_get(&pool->worker_ida, GFP_KERNEL))
1363 spin_lock_irq(&gcwq->lock);
1365 spin_unlock_irq(&gcwq->lock);
1367 worker = alloc_worker();
1371 worker->pool = pool;
1374 if (!on_unbound_cpu)
1375 worker->task = kthread_create_on_node(worker_thread,
1376 worker, cpu_to_node(gcwq->cpu),
1377 "kworker/%u:%d%s", gcwq->cpu, id, pri);
1379 worker->task = kthread_create(worker_thread, worker,
1380 "kworker/u:%d%s", id, pri);
1381 if (IS_ERR(worker->task))
1384 if (worker_pool_pri(pool))
1385 set_user_nice(worker->task, HIGHPRI_NICE_LEVEL);
1388 * A rogue worker will become a regular one if CPU comes
1389 * online later on. Make sure every worker has
1390 * PF_THREAD_BOUND set.
1392 if (bind && !on_unbound_cpu)
1393 kthread_bind(worker->task, gcwq->cpu);
1395 worker->task->flags |= PF_THREAD_BOUND;
1397 worker->flags |= WORKER_UNBOUND;
1403 spin_lock_irq(&gcwq->lock);
1404 ida_remove(&pool->worker_ida, id);
1405 spin_unlock_irq(&gcwq->lock);
1412 * start_worker - start a newly created worker
1413 * @worker: worker to start
1415 * Make the gcwq aware of @worker and start it.
1418 * spin_lock_irq(gcwq->lock).
1420 static void start_worker(struct worker *worker)
1422 worker->flags |= WORKER_STARTED;
1423 worker->pool->nr_workers++;
1424 worker_enter_idle(worker);
1425 wake_up_process(worker->task);
1429 * destroy_worker - destroy a workqueue worker
1430 * @worker: worker to be destroyed
1432 * Destroy @worker and adjust @gcwq stats accordingly.
1435 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1437 static void destroy_worker(struct worker *worker)
1439 struct worker_pool *pool = worker->pool;
1440 struct global_cwq *gcwq = pool->gcwq;
1441 int id = worker->id;
1443 /* sanity check frenzy */
1444 BUG_ON(worker->current_work);
1445 BUG_ON(!list_empty(&worker->scheduled));
1447 if (worker->flags & WORKER_STARTED)
1449 if (worker->flags & WORKER_IDLE)
1452 list_del_init(&worker->entry);
1453 worker->flags |= WORKER_DIE;
1455 spin_unlock_irq(&gcwq->lock);
1457 kthread_stop(worker->task);
1460 spin_lock_irq(&gcwq->lock);
1461 ida_remove(&pool->worker_ida, id);
1464 static void idle_worker_timeout(unsigned long __pool)
1466 struct worker_pool *pool = (void *)__pool;
1467 struct global_cwq *gcwq = pool->gcwq;
1469 spin_lock_irq(&gcwq->lock);
1471 if (too_many_workers(pool)) {
1472 struct worker *worker;
1473 unsigned long expires;
1475 /* idle_list is kept in LIFO order, check the last one */
1476 worker = list_entry(pool->idle_list.prev, struct worker, entry);
1477 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1479 if (time_before(jiffies, expires))
1480 mod_timer(&pool->idle_timer, expires);
1482 /* it's been idle for too long, wake up manager */
1483 pool->flags |= POOL_MANAGE_WORKERS;
1484 wake_up_worker(pool);
1488 spin_unlock_irq(&gcwq->lock);
1491 static bool send_mayday(struct work_struct *work)
1493 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1494 struct workqueue_struct *wq = cwq->wq;
1497 if (!(wq->flags & WQ_RESCUER))
1500 /* mayday mayday mayday */
1501 cpu = cwq->pool->gcwq->cpu;
1502 /* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
1503 if (cpu == WORK_CPU_UNBOUND)
1505 if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask))
1506 wake_up_process(wq->rescuer->task);
1510 static void gcwq_mayday_timeout(unsigned long __pool)
1512 struct worker_pool *pool = (void *)__pool;
1513 struct global_cwq *gcwq = pool->gcwq;
1514 struct work_struct *work;
1516 spin_lock_irq(&gcwq->lock);
1518 if (need_to_create_worker(pool)) {
1520 * We've been trying to create a new worker but
1521 * haven't been successful. We might be hitting an
1522 * allocation deadlock. Send distress signals to
1525 list_for_each_entry(work, &pool->worklist, entry)
1529 spin_unlock_irq(&gcwq->lock);
1531 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL);
1535 * maybe_create_worker - create a new worker if necessary
1536 * @pool: pool to create a new worker for
1538 * Create a new worker for @pool if necessary. @pool is guaranteed to
1539 * have at least one idle worker on return from this function. If
1540 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1541 * sent to all rescuers with works scheduled on @pool to resolve
1542 * possible allocation deadlock.
1544 * On return, need_to_create_worker() is guaranteed to be false and
1545 * may_start_working() true.
1548 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1549 * multiple times. Does GFP_KERNEL allocations. Called only from
1553 * false if no action was taken and gcwq->lock stayed locked, true
1556 static bool maybe_create_worker(struct worker_pool *pool)
1557 __releases(&gcwq->lock)
1558 __acquires(&gcwq->lock)
1560 struct global_cwq *gcwq = pool->gcwq;
1562 if (!need_to_create_worker(pool))
1565 spin_unlock_irq(&gcwq->lock);
1567 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1568 mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1571 struct worker *worker;
1573 worker = create_worker(pool, true);
1575 del_timer_sync(&pool->mayday_timer);
1576 spin_lock_irq(&gcwq->lock);
1577 start_worker(worker);
1578 BUG_ON(need_to_create_worker(pool));
1582 if (!need_to_create_worker(pool))
1585 __set_current_state(TASK_INTERRUPTIBLE);
1586 schedule_timeout(CREATE_COOLDOWN);
1588 if (!need_to_create_worker(pool))
1592 del_timer_sync(&pool->mayday_timer);
1593 spin_lock_irq(&gcwq->lock);
1594 if (need_to_create_worker(pool))
1600 * maybe_destroy_worker - destroy workers which have been idle for a while
1601 * @pool: pool to destroy workers for
1603 * Destroy @pool workers which have been idle for longer than
1604 * IDLE_WORKER_TIMEOUT.
1607 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1608 * multiple times. Called only from manager.
1611 * false if no action was taken and gcwq->lock stayed locked, true
1614 static bool maybe_destroy_workers(struct worker_pool *pool)
1618 while (too_many_workers(pool)) {
1619 struct worker *worker;
1620 unsigned long expires;
1622 worker = list_entry(pool->idle_list.prev, struct worker, entry);
1623 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1625 if (time_before(jiffies, expires)) {
1626 mod_timer(&pool->idle_timer, expires);
1630 destroy_worker(worker);
1638 * manage_workers - manage worker pool
1641 * Assume the manager role and manage gcwq worker pool @worker belongs
1642 * to. At any given time, there can be only zero or one manager per
1643 * gcwq. The exclusion is handled automatically by this function.
1645 * The caller can safely start processing works on false return. On
1646 * true return, it's guaranteed that need_to_create_worker() is false
1647 * and may_start_working() is true.
1650 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1651 * multiple times. Does GFP_KERNEL allocations.
1654 * false if no action was taken and gcwq->lock stayed locked, true if
1655 * some action was taken.
1657 static bool manage_workers(struct worker *worker)
1659 struct worker_pool *pool = worker->pool;
1660 struct global_cwq *gcwq = pool->gcwq;
1663 if (pool->flags & POOL_MANAGING_WORKERS)
1666 pool->flags &= ~POOL_MANAGE_WORKERS;
1667 pool->flags |= POOL_MANAGING_WORKERS;
1670 * Destroy and then create so that may_start_working() is true
1673 ret |= maybe_destroy_workers(pool);
1674 ret |= maybe_create_worker(pool);
1676 pool->flags &= ~POOL_MANAGING_WORKERS;
1679 * The trustee might be waiting to take over the manager
1680 * position, tell it we're done.
1682 if (unlikely(gcwq->trustee))
1683 wake_up_all(&gcwq->trustee_wait);
1689 * move_linked_works - move linked works to a list
1690 * @work: start of series of works to be scheduled
1691 * @head: target list to append @work to
1692 * @nextp: out paramter for nested worklist walking
1694 * Schedule linked works starting from @work to @head. Work series to
1695 * be scheduled starts at @work and includes any consecutive work with
1696 * WORK_STRUCT_LINKED set in its predecessor.
1698 * If @nextp is not NULL, it's updated to point to the next work of
1699 * the last scheduled work. This allows move_linked_works() to be
1700 * nested inside outer list_for_each_entry_safe().
1703 * spin_lock_irq(gcwq->lock).
1705 static void move_linked_works(struct work_struct *work, struct list_head *head,
1706 struct work_struct **nextp)
1708 struct work_struct *n;
1711 * Linked worklist will always end before the end of the list,
1712 * use NULL for list head.
1714 list_for_each_entry_safe_from(work, n, NULL, entry) {
1715 list_move_tail(&work->entry, head);
1716 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1721 * If we're already inside safe list traversal and have moved
1722 * multiple works to the scheduled queue, the next position
1723 * needs to be updated.
1729 static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq)
1731 struct work_struct *work = list_first_entry(&cwq->delayed_works,
1732 struct work_struct, entry);
1734 trace_workqueue_activate_work(work);
1735 move_linked_works(work, &cwq->pool->worklist, NULL);
1736 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1741 * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight
1742 * @cwq: cwq of interest
1743 * @color: color of work which left the queue
1744 * @delayed: for a delayed work
1746 * A work either has completed or is removed from pending queue,
1747 * decrement nr_in_flight of its cwq and handle workqueue flushing.
1750 * spin_lock_irq(gcwq->lock).
1752 static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color,
1755 /* ignore uncolored works */
1756 if (color == WORK_NO_COLOR)
1759 cwq->nr_in_flight[color]--;
1763 if (!list_empty(&cwq->delayed_works)) {
1764 /* one down, submit a delayed one */
1765 if (cwq->nr_active < cwq->max_active)
1766 cwq_activate_first_delayed(cwq);
1770 /* is flush in progress and are we at the flushing tip? */
1771 if (likely(cwq->flush_color != color))
1774 /* are there still in-flight works? */
1775 if (cwq->nr_in_flight[color])
1778 /* this cwq is done, clear flush_color */
1779 cwq->flush_color = -1;
1782 * If this was the last cwq, wake up the first flusher. It
1783 * will handle the rest.
1785 if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush))
1786 complete(&cwq->wq->first_flusher->done);
1790 * process_one_work - process single work
1792 * @work: work to process
1794 * Process @work. This function contains all the logics necessary to
1795 * process a single work including synchronization against and
1796 * interaction with other workers on the same cpu, queueing and
1797 * flushing. As long as context requirement is met, any worker can
1798 * call this function to process a work.
1801 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1803 static void process_one_work(struct worker *worker, struct work_struct *work)
1804 __releases(&gcwq->lock)
1805 __acquires(&gcwq->lock)
1807 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1808 struct worker_pool *pool = worker->pool;
1809 struct global_cwq *gcwq = pool->gcwq;
1810 struct hlist_head *bwh = busy_worker_head(gcwq, work);
1811 bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE;
1812 work_func_t f = work->func;
1814 struct worker *collision;
1815 #ifdef CONFIG_LOCKDEP
1817 * It is permissible to free the struct work_struct from
1818 * inside the function that is called from it, this we need to
1819 * take into account for lockdep too. To avoid bogus "held
1820 * lock freed" warnings as well as problems when looking into
1821 * work->lockdep_map, make a copy and use that here.
1823 struct lockdep_map lockdep_map;
1825 lockdep_copy_map(&lockdep_map, &work->lockdep_map);
1828 * A single work shouldn't be executed concurrently by
1829 * multiple workers on a single cpu. Check whether anyone is
1830 * already processing the work. If so, defer the work to the
1831 * currently executing one.
1833 collision = __find_worker_executing_work(gcwq, bwh, work);
1834 if (unlikely(collision)) {
1835 move_linked_works(work, &collision->scheduled, NULL);
1839 /* claim and process */
1840 debug_work_deactivate(work);
1841 hlist_add_head(&worker->hentry, bwh);
1842 worker->current_work = work;
1843 worker->current_cwq = cwq;
1844 work_color = get_work_color(work);
1846 /* record the current cpu number in the work data and dequeue */
1847 set_work_cpu(work, gcwq->cpu);
1848 list_del_init(&work->entry);
1851 * CPU intensive works don't participate in concurrency
1852 * management. They're the scheduler's responsibility.
1854 if (unlikely(cpu_intensive))
1855 worker_set_flags(worker, WORKER_CPU_INTENSIVE, true);
1858 * Unbound gcwq isn't concurrency managed and work items should be
1859 * executed ASAP. Wake up another worker if necessary.
1861 if ((worker->flags & WORKER_UNBOUND) && need_more_worker(pool))
1862 wake_up_worker(pool);
1864 spin_unlock_irq(&gcwq->lock);
1866 work_clear_pending(work);
1867 lock_map_acquire_read(&cwq->wq->lockdep_map);
1868 lock_map_acquire(&lockdep_map);
1869 trace_workqueue_execute_start(work);
1872 * While we must be careful to not use "work" after this, the trace
1873 * point will only record its address.
1875 trace_workqueue_execute_end(work);
1876 lock_map_release(&lockdep_map);
1877 lock_map_release(&cwq->wq->lockdep_map);
1879 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
1880 printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
1882 current->comm, preempt_count(), task_pid_nr(current));
1883 printk(KERN_ERR " last function: ");
1884 print_symbol("%s\n", (unsigned long)f);
1885 debug_show_held_locks(current);
1889 spin_lock_irq(&gcwq->lock);
1891 /* clear cpu intensive status */
1892 if (unlikely(cpu_intensive))
1893 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
1895 /* we're done with it, release */
1896 hlist_del_init(&worker->hentry);
1897 worker->current_work = NULL;
1898 worker->current_cwq = NULL;
1899 cwq_dec_nr_in_flight(cwq, work_color, false);
1903 * process_scheduled_works - process scheduled works
1906 * Process all scheduled works. Please note that the scheduled list
1907 * may change while processing a work, so this function repeatedly
1908 * fetches a work from the top and executes it.
1911 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1914 static void process_scheduled_works(struct worker *worker)
1916 while (!list_empty(&worker->scheduled)) {
1917 struct work_struct *work = list_first_entry(&worker->scheduled,
1918 struct work_struct, entry);
1919 process_one_work(worker, work);
1924 * worker_thread - the worker thread function
1927 * The gcwq worker thread function. There's a single dynamic pool of
1928 * these per each cpu. These workers process all works regardless of
1929 * their specific target workqueue. The only exception is works which
1930 * belong to workqueues with a rescuer which will be explained in
1933 static int worker_thread(void *__worker)
1935 struct worker *worker = __worker;
1936 struct worker_pool *pool = worker->pool;
1937 struct global_cwq *gcwq = pool->gcwq;
1939 /* tell the scheduler that this is a workqueue worker */
1940 worker->task->flags |= PF_WQ_WORKER;
1942 spin_lock_irq(&gcwq->lock);
1944 /* DIE can be set only while we're idle, checking here is enough */
1945 if (worker->flags & WORKER_DIE) {
1946 spin_unlock_irq(&gcwq->lock);
1947 worker->task->flags &= ~PF_WQ_WORKER;
1951 worker_leave_idle(worker);
1953 /* no more worker necessary? */
1954 if (!need_more_worker(pool))
1957 /* do we need to manage? */
1958 if (unlikely(!may_start_working(pool)) && manage_workers(worker))
1962 * ->scheduled list can only be filled while a worker is
1963 * preparing to process a work or actually processing it.
1964 * Make sure nobody diddled with it while I was sleeping.
1966 BUG_ON(!list_empty(&worker->scheduled));
1969 * When control reaches this point, we're guaranteed to have
1970 * at least one idle worker or that someone else has already
1971 * assumed the manager role.
1973 worker_clr_flags(worker, WORKER_PREP);
1976 struct work_struct *work =
1977 list_first_entry(&pool->worklist,
1978 struct work_struct, entry);
1980 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
1981 /* optimization path, not strictly necessary */
1982 process_one_work(worker, work);
1983 if (unlikely(!list_empty(&worker->scheduled)))
1984 process_scheduled_works(worker);
1986 move_linked_works(work, &worker->scheduled, NULL);
1987 process_scheduled_works(worker);
1989 } while (keep_working(pool));
1991 worker_set_flags(worker, WORKER_PREP, false);
1993 if (unlikely(need_to_manage_workers(pool)) && manage_workers(worker))
1997 * gcwq->lock is held and there's no work to process and no
1998 * need to manage, sleep. Workers are woken up only while
1999 * holding gcwq->lock or from local cpu, so setting the
2000 * current state before releasing gcwq->lock is enough to
2001 * prevent losing any event.
2003 worker_enter_idle(worker);
2004 __set_current_state(TASK_INTERRUPTIBLE);
2005 spin_unlock_irq(&gcwq->lock);
2011 * rescuer_thread - the rescuer thread function
2012 * @__wq: the associated workqueue
2014 * Workqueue rescuer thread function. There's one rescuer for each
2015 * workqueue which has WQ_RESCUER set.
2017 * Regular work processing on a gcwq may block trying to create a new
2018 * worker which uses GFP_KERNEL allocation which has slight chance of
2019 * developing into deadlock if some works currently on the same queue
2020 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2021 * the problem rescuer solves.
2023 * When such condition is possible, the gcwq summons rescuers of all
2024 * workqueues which have works queued on the gcwq and let them process
2025 * those works so that forward progress can be guaranteed.
2027 * This should happen rarely.
2029 static int rescuer_thread(void *__wq)
2031 struct workqueue_struct *wq = __wq;
2032 struct worker *rescuer = wq->rescuer;
2033 struct list_head *scheduled = &rescuer->scheduled;
2034 bool is_unbound = wq->flags & WQ_UNBOUND;
2037 set_user_nice(current, RESCUER_NICE_LEVEL);
2039 set_current_state(TASK_INTERRUPTIBLE);
2041 if (kthread_should_stop())
2045 * See whether any cpu is asking for help. Unbounded
2046 * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
2048 for_each_mayday_cpu(cpu, wq->mayday_mask) {
2049 unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu;
2050 struct cpu_workqueue_struct *cwq = get_cwq(tcpu, wq);
2051 struct worker_pool *pool = cwq->pool;
2052 struct global_cwq *gcwq = pool->gcwq;
2053 struct work_struct *work, *n;
2055 __set_current_state(TASK_RUNNING);
2056 mayday_clear_cpu(cpu, wq->mayday_mask);
2058 /* migrate to the target cpu if possible */
2059 rescuer->pool = pool;
2060 worker_maybe_bind_and_lock(rescuer);
2063 * Slurp in all works issued via this workqueue and
2066 BUG_ON(!list_empty(&rescuer->scheduled));
2067 list_for_each_entry_safe(work, n, &pool->worklist, entry)
2068 if (get_work_cwq(work) == cwq)
2069 move_linked_works(work, scheduled, &n);
2071 process_scheduled_works(rescuer);
2074 * Leave this gcwq. If keep_working() is %true, notify a
2075 * regular worker; otherwise, we end up with 0 concurrency
2076 * and stalling the execution.
2078 if (keep_working(pool))
2079 wake_up_worker(pool);
2081 spin_unlock_irq(&gcwq->lock);
2089 struct work_struct work;
2090 struct completion done;
2093 static void wq_barrier_func(struct work_struct *work)
2095 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2096 complete(&barr->done);
2100 * insert_wq_barrier - insert a barrier work
2101 * @cwq: cwq to insert barrier into
2102 * @barr: wq_barrier to insert
2103 * @target: target work to attach @barr to
2104 * @worker: worker currently executing @target, NULL if @target is not executing
2106 * @barr is linked to @target such that @barr is completed only after
2107 * @target finishes execution. Please note that the ordering
2108 * guarantee is observed only with respect to @target and on the local
2111 * Currently, a queued barrier can't be canceled. This is because
2112 * try_to_grab_pending() can't determine whether the work to be
2113 * grabbed is at the head of the queue and thus can't clear LINKED
2114 * flag of the previous work while there must be a valid next work
2115 * after a work with LINKED flag set.
2117 * Note that when @worker is non-NULL, @target may be modified
2118 * underneath us, so we can't reliably determine cwq from @target.
2121 * spin_lock_irq(gcwq->lock).
2123 static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
2124 struct wq_barrier *barr,
2125 struct work_struct *target, struct worker *worker)
2127 struct list_head *head;
2128 unsigned int linked = 0;
2131 * debugobject calls are safe here even with gcwq->lock locked
2132 * as we know for sure that this will not trigger any of the
2133 * checks and call back into the fixup functions where we
2136 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2137 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2138 init_completion(&barr->done);
2141 * If @target is currently being executed, schedule the
2142 * barrier to the worker; otherwise, put it after @target.
2145 head = worker->scheduled.next;
2147 unsigned long *bits = work_data_bits(target);
2149 head = target->entry.next;
2150 /* there can already be other linked works, inherit and set */
2151 linked = *bits & WORK_STRUCT_LINKED;
2152 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2155 debug_work_activate(&barr->work);
2156 insert_work(cwq, &barr->work, head,
2157 work_color_to_flags(WORK_NO_COLOR) | linked);
2161 * flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing
2162 * @wq: workqueue being flushed
2163 * @flush_color: new flush color, < 0 for no-op
2164 * @work_color: new work color, < 0 for no-op
2166 * Prepare cwqs for workqueue flushing.
2168 * If @flush_color is non-negative, flush_color on all cwqs should be
2169 * -1. If no cwq has in-flight commands at the specified color, all
2170 * cwq->flush_color's stay at -1 and %false is returned. If any cwq
2171 * has in flight commands, its cwq->flush_color is set to
2172 * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq
2173 * wakeup logic is armed and %true is returned.
2175 * The caller should have initialized @wq->first_flusher prior to
2176 * calling this function with non-negative @flush_color. If
2177 * @flush_color is negative, no flush color update is done and %false
2180 * If @work_color is non-negative, all cwqs should have the same
2181 * work_color which is previous to @work_color and all will be
2182 * advanced to @work_color.
2185 * mutex_lock(wq->flush_mutex).
2188 * %true if @flush_color >= 0 and there's something to flush. %false
2191 static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq,
2192 int flush_color, int work_color)
2197 if (flush_color >= 0) {
2198 BUG_ON(atomic_read(&wq->nr_cwqs_to_flush));
2199 atomic_set(&wq->nr_cwqs_to_flush, 1);
2202 for_each_cwq_cpu(cpu, wq) {
2203 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2204 struct global_cwq *gcwq = cwq->pool->gcwq;
2206 spin_lock_irq(&gcwq->lock);
2208 if (flush_color >= 0) {
2209 BUG_ON(cwq->flush_color != -1);
2211 if (cwq->nr_in_flight[flush_color]) {
2212 cwq->flush_color = flush_color;
2213 atomic_inc(&wq->nr_cwqs_to_flush);
2218 if (work_color >= 0) {
2219 BUG_ON(work_color != work_next_color(cwq->work_color));
2220 cwq->work_color = work_color;
2223 spin_unlock_irq(&gcwq->lock);
2226 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_to_flush))
2227 complete(&wq->first_flusher->done);
2233 * flush_workqueue - ensure that any scheduled work has run to completion.
2234 * @wq: workqueue to flush
2236 * Forces execution of the workqueue and blocks until its completion.
2237 * This is typically used in driver shutdown handlers.
2239 * We sleep until all works which were queued on entry have been handled,
2240 * but we are not livelocked by new incoming ones.
2242 void flush_workqueue(struct workqueue_struct *wq)
2244 struct wq_flusher this_flusher = {
2245 .list = LIST_HEAD_INIT(this_flusher.list),
2247 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2251 lock_map_acquire(&wq->lockdep_map);
2252 lock_map_release(&wq->lockdep_map);
2254 mutex_lock(&wq->flush_mutex);
2257 * Start-to-wait phase
2259 next_color = work_next_color(wq->work_color);
2261 if (next_color != wq->flush_color) {
2263 * Color space is not full. The current work_color
2264 * becomes our flush_color and work_color is advanced
2267 BUG_ON(!list_empty(&wq->flusher_overflow));
2268 this_flusher.flush_color = wq->work_color;
2269 wq->work_color = next_color;
2271 if (!wq->first_flusher) {
2272 /* no flush in progress, become the first flusher */
2273 BUG_ON(wq->flush_color != this_flusher.flush_color);
2275 wq->first_flusher = &this_flusher;
2277 if (!flush_workqueue_prep_cwqs(wq, wq->flush_color,
2279 /* nothing to flush, done */
2280 wq->flush_color = next_color;
2281 wq->first_flusher = NULL;
2286 BUG_ON(wq->flush_color == this_flusher.flush_color);
2287 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2288 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2292 * Oops, color space is full, wait on overflow queue.
2293 * The next flush completion will assign us
2294 * flush_color and transfer to flusher_queue.
2296 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2299 mutex_unlock(&wq->flush_mutex);
2301 wait_for_completion(&this_flusher.done);
2304 * Wake-up-and-cascade phase
2306 * First flushers are responsible for cascading flushes and
2307 * handling overflow. Non-first flushers can simply return.
2309 if (wq->first_flusher != &this_flusher)
2312 mutex_lock(&wq->flush_mutex);
2314 /* we might have raced, check again with mutex held */
2315 if (wq->first_flusher != &this_flusher)
2318 wq->first_flusher = NULL;
2320 BUG_ON(!list_empty(&this_flusher.list));
2321 BUG_ON(wq->flush_color != this_flusher.flush_color);
2324 struct wq_flusher *next, *tmp;
2326 /* complete all the flushers sharing the current flush color */
2327 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2328 if (next->flush_color != wq->flush_color)
2330 list_del_init(&next->list);
2331 complete(&next->done);
2334 BUG_ON(!list_empty(&wq->flusher_overflow) &&
2335 wq->flush_color != work_next_color(wq->work_color));
2337 /* this flush_color is finished, advance by one */
2338 wq->flush_color = work_next_color(wq->flush_color);
2340 /* one color has been freed, handle overflow queue */
2341 if (!list_empty(&wq->flusher_overflow)) {
2343 * Assign the same color to all overflowed
2344 * flushers, advance work_color and append to
2345 * flusher_queue. This is the start-to-wait
2346 * phase for these overflowed flushers.
2348 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2349 tmp->flush_color = wq->work_color;
2351 wq->work_color = work_next_color(wq->work_color);
2353 list_splice_tail_init(&wq->flusher_overflow,
2354 &wq->flusher_queue);
2355 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2358 if (list_empty(&wq->flusher_queue)) {
2359 BUG_ON(wq->flush_color != wq->work_color);
2364 * Need to flush more colors. Make the next flusher
2365 * the new first flusher and arm cwqs.
2367 BUG_ON(wq->flush_color == wq->work_color);
2368 BUG_ON(wq->flush_color != next->flush_color);
2370 list_del_init(&next->list);
2371 wq->first_flusher = next;
2373 if (flush_workqueue_prep_cwqs(wq, wq->flush_color, -1))
2377 * Meh... this color is already done, clear first
2378 * flusher and repeat cascading.
2380 wq->first_flusher = NULL;
2384 mutex_unlock(&wq->flush_mutex);
2386 EXPORT_SYMBOL_GPL(flush_workqueue);
2389 * drain_workqueue - drain a workqueue
2390 * @wq: workqueue to drain
2392 * Wait until the workqueue becomes empty. While draining is in progress,
2393 * only chain queueing is allowed. IOW, only currently pending or running
2394 * work items on @wq can queue further work items on it. @wq is flushed
2395 * repeatedly until it becomes empty. The number of flushing is detemined
2396 * by the depth of chaining and should be relatively short. Whine if it
2399 void drain_workqueue(struct workqueue_struct *wq)
2401 unsigned int flush_cnt = 0;
2405 * __queue_work() needs to test whether there are drainers, is much
2406 * hotter than drain_workqueue() and already looks at @wq->flags.
2407 * Use WQ_DRAINING so that queue doesn't have to check nr_drainers.
2409 spin_lock(&workqueue_lock);
2410 if (!wq->nr_drainers++)
2411 wq->flags |= WQ_DRAINING;
2412 spin_unlock(&workqueue_lock);
2414 flush_workqueue(wq);
2416 for_each_cwq_cpu(cpu, wq) {
2417 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2420 spin_lock_irq(&cwq->pool->gcwq->lock);
2421 drained = !cwq->nr_active && list_empty(&cwq->delayed_works);
2422 spin_unlock_irq(&cwq->pool->gcwq->lock);
2427 if (++flush_cnt == 10 ||
2428 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
2429 pr_warning("workqueue %s: flush on destruction isn't complete after %u tries\n",
2430 wq->name, flush_cnt);
2434 spin_lock(&workqueue_lock);
2435 if (!--wq->nr_drainers)
2436 wq->flags &= ~WQ_DRAINING;
2437 spin_unlock(&workqueue_lock);
2439 EXPORT_SYMBOL_GPL(drain_workqueue);
2441 static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
2442 bool wait_executing)
2444 struct worker *worker = NULL;
2445 struct global_cwq *gcwq;
2446 struct cpu_workqueue_struct *cwq;
2449 gcwq = get_work_gcwq(work);
2453 spin_lock_irq(&gcwq->lock);
2454 if (!list_empty(&work->entry)) {
2456 * See the comment near try_to_grab_pending()->smp_rmb().
2457 * If it was re-queued to a different gcwq under us, we
2458 * are not going to wait.
2461 cwq = get_work_cwq(work);
2462 if (unlikely(!cwq || gcwq != cwq->pool->gcwq))
2464 } else if (wait_executing) {
2465 worker = find_worker_executing_work(gcwq, work);
2468 cwq = worker->current_cwq;
2472 insert_wq_barrier(cwq, barr, work, worker);
2473 spin_unlock_irq(&gcwq->lock);
2476 * If @max_active is 1 or rescuer is in use, flushing another work
2477 * item on the same workqueue may lead to deadlock. Make sure the
2478 * flusher is not running on the same workqueue by verifying write
2481 if (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER)
2482 lock_map_acquire(&cwq->wq->lockdep_map);
2484 lock_map_acquire_read(&cwq->wq->lockdep_map);
2485 lock_map_release(&cwq->wq->lockdep_map);
2489 spin_unlock_irq(&gcwq->lock);
2494 * flush_work - wait for a work to finish executing the last queueing instance
2495 * @work: the work to flush
2497 * Wait until @work has finished execution. This function considers
2498 * only the last queueing instance of @work. If @work has been
2499 * enqueued across different CPUs on a non-reentrant workqueue or on
2500 * multiple workqueues, @work might still be executing on return on
2501 * some of the CPUs from earlier queueing.
2503 * If @work was queued only on a non-reentrant, ordered or unbound
2504 * workqueue, @work is guaranteed to be idle on return if it hasn't
2505 * been requeued since flush started.
2508 * %true if flush_work() waited for the work to finish execution,
2509 * %false if it was already idle.
2511 bool flush_work(struct work_struct *work)
2513 struct wq_barrier barr;
2515 lock_map_acquire(&work->lockdep_map);
2516 lock_map_release(&work->lockdep_map);
2518 if (start_flush_work(work, &barr, true)) {
2519 wait_for_completion(&barr.done);
2520 destroy_work_on_stack(&barr.work);
2525 EXPORT_SYMBOL_GPL(flush_work);
2527 static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)
2529 struct wq_barrier barr;
2530 struct worker *worker;
2532 spin_lock_irq(&gcwq->lock);
2534 worker = find_worker_executing_work(gcwq, work);
2535 if (unlikely(worker))
2536 insert_wq_barrier(worker->current_cwq, &barr, work, worker);
2538 spin_unlock_irq(&gcwq->lock);
2540 if (unlikely(worker)) {
2541 wait_for_completion(&barr.done);
2542 destroy_work_on_stack(&barr.work);
2548 static bool wait_on_work(struct work_struct *work)
2555 lock_map_acquire(&work->lockdep_map);
2556 lock_map_release(&work->lockdep_map);
2558 for_each_gcwq_cpu(cpu)
2559 ret |= wait_on_cpu_work(get_gcwq(cpu), work);
2564 * flush_work_sync - wait until a work has finished execution
2565 * @work: the work to flush
2567 * Wait until @work has finished execution. On return, it's
2568 * guaranteed that all queueing instances of @work which happened
2569 * before this function is called are finished. In other words, if
2570 * @work hasn't been requeued since this function was called, @work is
2571 * guaranteed to be idle on return.
2574 * %true if flush_work_sync() waited for the work to finish execution,
2575 * %false if it was already idle.
2577 bool flush_work_sync(struct work_struct *work)
2579 struct wq_barrier barr;
2580 bool pending, waited;
2582 /* we'll wait for executions separately, queue barr only if pending */
2583 pending = start_flush_work(work, &barr, false);
2585 /* wait for executions to finish */
2586 waited = wait_on_work(work);
2588 /* wait for the pending one */
2590 wait_for_completion(&barr.done);
2591 destroy_work_on_stack(&barr.work);
2594 return pending || waited;
2596 EXPORT_SYMBOL_GPL(flush_work_sync);
2599 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
2600 * so this work can't be re-armed in any way.
2602 static int try_to_grab_pending(struct work_struct *work)
2604 struct global_cwq *gcwq;
2607 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
2611 * The queueing is in progress, or it is already queued. Try to
2612 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
2614 gcwq = get_work_gcwq(work);
2618 spin_lock_irq(&gcwq->lock);
2619 if (!list_empty(&work->entry)) {
2621 * This work is queued, but perhaps we locked the wrong gcwq.
2622 * In that case we must see the new value after rmb(), see
2623 * insert_work()->wmb().
2626 if (gcwq == get_work_gcwq(work)) {
2627 debug_work_deactivate(work);
2628 list_del_init(&work->entry);
2629 cwq_dec_nr_in_flight(get_work_cwq(work),
2630 get_work_color(work),
2631 *work_data_bits(work) & WORK_STRUCT_DELAYED);
2635 spin_unlock_irq(&gcwq->lock);
2640 static bool __cancel_work_timer(struct work_struct *work,
2641 struct timer_list* timer)
2646 ret = (timer && likely(del_timer(timer)));
2648 ret = try_to_grab_pending(work);
2650 } while (unlikely(ret < 0));
2652 clear_work_data(work);
2657 * cancel_work_sync - cancel a work and wait for it to finish
2658 * @work: the work to cancel
2660 * Cancel @work and wait for its execution to finish. This function
2661 * can be used even if the work re-queues itself or migrates to
2662 * another workqueue. On return from this function, @work is
2663 * guaranteed to be not pending or executing on any CPU.
2665 * cancel_work_sync(&delayed_work->work) must not be used for
2666 * delayed_work's. Use cancel_delayed_work_sync() instead.
2668 * The caller must ensure that the workqueue on which @work was last
2669 * queued can't be destroyed before this function returns.
2672 * %true if @work was pending, %false otherwise.
2674 bool cancel_work_sync(struct work_struct *work)
2676 return __cancel_work_timer(work, NULL);
2678 EXPORT_SYMBOL_GPL(cancel_work_sync);
2681 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2682 * @dwork: the delayed work to flush
2684 * Delayed timer is cancelled and the pending work is queued for
2685 * immediate execution. Like flush_work(), this function only
2686 * considers the last queueing instance of @dwork.
2689 * %true if flush_work() waited for the work to finish execution,
2690 * %false if it was already idle.
2692 bool flush_delayed_work(struct delayed_work *dwork)
2694 if (del_timer_sync(&dwork->timer))
2695 __queue_work(raw_smp_processor_id(),
2696 get_work_cwq(&dwork->work)->wq, &dwork->work);
2697 return flush_work(&dwork->work);
2699 EXPORT_SYMBOL(flush_delayed_work);
2702 * flush_delayed_work_sync - wait for a dwork to finish
2703 * @dwork: the delayed work to flush
2705 * Delayed timer is cancelled and the pending work is queued for
2706 * execution immediately. Other than timer handling, its behavior
2707 * is identical to flush_work_sync().
2710 * %true if flush_work_sync() waited for the work to finish execution,
2711 * %false if it was already idle.
2713 bool flush_delayed_work_sync(struct delayed_work *dwork)
2715 if (del_timer_sync(&dwork->timer))
2716 __queue_work(raw_smp_processor_id(),
2717 get_work_cwq(&dwork->work)->wq, &dwork->work);
2718 return flush_work_sync(&dwork->work);
2720 EXPORT_SYMBOL(flush_delayed_work_sync);
2723 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
2724 * @dwork: the delayed work cancel
2726 * This is cancel_work_sync() for delayed works.
2729 * %true if @dwork was pending, %false otherwise.
2731 bool cancel_delayed_work_sync(struct delayed_work *dwork)
2733 return __cancel_work_timer(&dwork->work, &dwork->timer);
2735 EXPORT_SYMBOL(cancel_delayed_work_sync);
2738 * schedule_work - put work task in global workqueue
2739 * @work: job to be done
2741 * Returns zero if @work was already on the kernel-global workqueue and
2742 * non-zero otherwise.
2744 * This puts a job in the kernel-global workqueue if it was not already
2745 * queued and leaves it in the same position on the kernel-global
2746 * workqueue otherwise.
2748 int schedule_work(struct work_struct *work)
2750 return queue_work(system_wq, work);
2752 EXPORT_SYMBOL(schedule_work);
2755 * schedule_work_on - put work task on a specific cpu
2756 * @cpu: cpu to put the work task on
2757 * @work: job to be done
2759 * This puts a job on a specific cpu
2761 int schedule_work_on(int cpu, struct work_struct *work)
2763 return queue_work_on(cpu, system_wq, work);
2765 EXPORT_SYMBOL(schedule_work_on);
2768 * schedule_delayed_work - put work task in global workqueue after delay
2769 * @dwork: job to be done
2770 * @delay: number of jiffies to wait or 0 for immediate execution
2772 * After waiting for a given time this puts a job in the kernel-global
2775 int schedule_delayed_work(struct delayed_work *dwork,
2776 unsigned long delay)
2778 return queue_delayed_work(system_wq, dwork, delay);
2780 EXPORT_SYMBOL(schedule_delayed_work);
2783 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
2785 * @dwork: job to be done
2786 * @delay: number of jiffies to wait
2788 * After waiting for a given time this puts a job in the kernel-global
2789 * workqueue on the specified CPU.
2791 int schedule_delayed_work_on(int cpu,
2792 struct delayed_work *dwork, unsigned long delay)
2794 return queue_delayed_work_on(cpu, system_wq, dwork, delay);
2796 EXPORT_SYMBOL(schedule_delayed_work_on);
2799 * schedule_on_each_cpu - execute a function synchronously on each online CPU
2800 * @func: the function to call
2802 * schedule_on_each_cpu() executes @func on each online CPU using the
2803 * system workqueue and blocks until all CPUs have completed.
2804 * schedule_on_each_cpu() is very slow.
2807 * 0 on success, -errno on failure.
2809 int schedule_on_each_cpu(work_func_t func)
2812 struct work_struct __percpu *works;
2814 works = alloc_percpu(struct work_struct);
2820 for_each_online_cpu(cpu) {
2821 struct work_struct *work = per_cpu_ptr(works, cpu);
2823 INIT_WORK(work, func);
2824 schedule_work_on(cpu, work);
2827 for_each_online_cpu(cpu)
2828 flush_work(per_cpu_ptr(works, cpu));
2836 * flush_scheduled_work - ensure that any scheduled work has run to completion.
2838 * Forces execution of the kernel-global workqueue and blocks until its
2841 * Think twice before calling this function! It's very easy to get into
2842 * trouble if you don't take great care. Either of the following situations
2843 * will lead to deadlock:
2845 * One of the work items currently on the workqueue needs to acquire
2846 * a lock held by your code or its caller.
2848 * Your code is running in the context of a work routine.
2850 * They will be detected by lockdep when they occur, but the first might not
2851 * occur very often. It depends on what work items are on the workqueue and
2852 * what locks they need, which you have no control over.
2854 * In most situations flushing the entire workqueue is overkill; you merely
2855 * need to know that a particular work item isn't queued and isn't running.
2856 * In such cases you should use cancel_delayed_work_sync() or
2857 * cancel_work_sync() instead.
2859 void flush_scheduled_work(void)
2861 flush_workqueue(system_wq);
2863 EXPORT_SYMBOL(flush_scheduled_work);
2866 * execute_in_process_context - reliably execute the routine with user context
2867 * @fn: the function to execute
2868 * @ew: guaranteed storage for the execute work structure (must
2869 * be available when the work executes)
2871 * Executes the function immediately if process context is available,
2872 * otherwise schedules the function for delayed execution.
2874 * Returns: 0 - function was executed
2875 * 1 - function was scheduled for execution
2877 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
2879 if (!in_interrupt()) {
2884 INIT_WORK(&ew->work, fn);
2885 schedule_work(&ew->work);
2889 EXPORT_SYMBOL_GPL(execute_in_process_context);
2891 int keventd_up(void)
2893 return system_wq != NULL;
2896 static int alloc_cwqs(struct workqueue_struct *wq)
2899 * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS.
2900 * Make sure that the alignment isn't lower than that of
2901 * unsigned long long.
2903 const size_t size = sizeof(struct cpu_workqueue_struct);
2904 const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS,
2905 __alignof__(unsigned long long));
2907 if (!(wq->flags & WQ_UNBOUND))
2908 wq->cpu_wq.pcpu = __alloc_percpu(size, align);
2913 * Allocate enough room to align cwq and put an extra
2914 * pointer at the end pointing back to the originally
2915 * allocated pointer which will be used for free.
2917 ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL);
2919 wq->cpu_wq.single = PTR_ALIGN(ptr, align);
2920 *(void **)(wq->cpu_wq.single + 1) = ptr;
2924 /* just in case, make sure it's actually aligned */
2925 BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align));
2926 return wq->cpu_wq.v ? 0 : -ENOMEM;
2929 static void free_cwqs(struct workqueue_struct *wq)
2931 if (!(wq->flags & WQ_UNBOUND))
2932 free_percpu(wq->cpu_wq.pcpu);
2933 else if (wq->cpu_wq.single) {
2934 /* the pointer to free is stored right after the cwq */
2935 kfree(*(void **)(wq->cpu_wq.single + 1));
2939 static int wq_clamp_max_active(int max_active, unsigned int flags,
2942 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
2944 if (max_active < 1 || max_active > lim)
2945 printk(KERN_WARNING "workqueue: max_active %d requested for %s "
2946 "is out of range, clamping between %d and %d\n",
2947 max_active, name, 1, lim);
2949 return clamp_val(max_active, 1, lim);
2952 struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
2955 struct lock_class_key *key,
2956 const char *lock_name, ...)
2958 va_list args, args1;
2959 struct workqueue_struct *wq;
2963 /* determine namelen, allocate wq and format name */
2964 va_start(args, lock_name);
2965 va_copy(args1, args);
2966 namelen = vsnprintf(NULL, 0, fmt, args) + 1;
2968 wq = kzalloc(sizeof(*wq) + namelen, GFP_KERNEL);
2972 vsnprintf(wq->name, namelen, fmt, args1);
2977 * Workqueues which may be used during memory reclaim should
2978 * have a rescuer to guarantee forward progress.
2980 if (flags & WQ_MEM_RECLAIM)
2981 flags |= WQ_RESCUER;
2983 max_active = max_active ?: WQ_DFL_ACTIVE;
2984 max_active = wq_clamp_max_active(max_active, flags, wq->name);
2988 wq->saved_max_active = max_active;
2989 mutex_init(&wq->flush_mutex);
2990 atomic_set(&wq->nr_cwqs_to_flush, 0);
2991 INIT_LIST_HEAD(&wq->flusher_queue);
2992 INIT_LIST_HEAD(&wq->flusher_overflow);
2994 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
2995 INIT_LIST_HEAD(&wq->list);
2997 if (alloc_cwqs(wq) < 0)
3000 for_each_cwq_cpu(cpu, wq) {
3001 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3002 struct global_cwq *gcwq = get_gcwq(cpu);
3003 int pool_idx = (bool)(flags & WQ_HIGHPRI);
3005 BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK);
3006 cwq->pool = &gcwq->pools[pool_idx];
3008 cwq->flush_color = -1;
3009 cwq->max_active = max_active;
3010 INIT_LIST_HEAD(&cwq->delayed_works);
3013 if (flags & WQ_RESCUER) {
3014 struct worker *rescuer;
3016 if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL))
3019 wq->rescuer = rescuer = alloc_worker();
3023 rescuer->task = kthread_create(rescuer_thread, wq, "%s",
3025 if (IS_ERR(rescuer->task))
3028 rescuer->task->flags |= PF_THREAD_BOUND;
3029 wake_up_process(rescuer->task);
3033 * workqueue_lock protects global freeze state and workqueues
3034 * list. Grab it, set max_active accordingly and add the new
3035 * workqueue to workqueues list.
3037 spin_lock(&workqueue_lock);
3039 if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
3040 for_each_cwq_cpu(cpu, wq)
3041 get_cwq(cpu, wq)->max_active = 0;
3043 list_add(&wq->list, &workqueues);
3045 spin_unlock(&workqueue_lock);
3051 free_mayday_mask(wq->mayday_mask);
3057 EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
3060 * destroy_workqueue - safely terminate a workqueue
3061 * @wq: target workqueue
3063 * Safely destroy a workqueue. All work currently pending will be done first.
3065 void destroy_workqueue(struct workqueue_struct *wq)
3069 /* drain it before proceeding with destruction */
3070 drain_workqueue(wq);
3073 * wq list is used to freeze wq, remove from list after
3074 * flushing is complete in case freeze races us.
3076 spin_lock(&workqueue_lock);
3077 list_del(&wq->list);
3078 spin_unlock(&workqueue_lock);
3081 for_each_cwq_cpu(cpu, wq) {
3082 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3085 for (i = 0; i < WORK_NR_COLORS; i++)
3086 BUG_ON(cwq->nr_in_flight[i]);
3087 BUG_ON(cwq->nr_active);
3088 BUG_ON(!list_empty(&cwq->delayed_works));
3091 if (wq->flags & WQ_RESCUER) {
3092 kthread_stop(wq->rescuer->task);
3093 free_mayday_mask(wq->mayday_mask);
3100 EXPORT_SYMBOL_GPL(destroy_workqueue);
3103 * workqueue_set_max_active - adjust max_active of a workqueue
3104 * @wq: target workqueue
3105 * @max_active: new max_active value.
3107 * Set max_active of @wq to @max_active.
3110 * Don't call from IRQ context.
3112 void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
3116 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
3118 spin_lock(&workqueue_lock);
3120 wq->saved_max_active = max_active;
3122 for_each_cwq_cpu(cpu, wq) {
3123 struct global_cwq *gcwq = get_gcwq(cpu);
3125 spin_lock_irq(&gcwq->lock);
3127 if (!(wq->flags & WQ_FREEZABLE) ||
3128 !(gcwq->flags & GCWQ_FREEZING))
3129 get_cwq(gcwq->cpu, wq)->max_active = max_active;
3131 spin_unlock_irq(&gcwq->lock);
3134 spin_unlock(&workqueue_lock);
3136 EXPORT_SYMBOL_GPL(workqueue_set_max_active);
3139 * workqueue_congested - test whether a workqueue is congested
3140 * @cpu: CPU in question
3141 * @wq: target workqueue
3143 * Test whether @wq's cpu workqueue for @cpu is congested. There is
3144 * no synchronization around this function and the test result is
3145 * unreliable and only useful as advisory hints or for debugging.
3148 * %true if congested, %false otherwise.
3150 bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq)
3152 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3154 return !list_empty(&cwq->delayed_works);
3156 EXPORT_SYMBOL_GPL(workqueue_congested);
3159 * work_cpu - return the last known associated cpu for @work
3160 * @work: the work of interest
3163 * CPU number if @work was ever queued. WORK_CPU_NONE otherwise.
3165 unsigned int work_cpu(struct work_struct *work)
3167 struct global_cwq *gcwq = get_work_gcwq(work);
3169 return gcwq ? gcwq->cpu : WORK_CPU_NONE;
3171 EXPORT_SYMBOL_GPL(work_cpu);
3174 * work_busy - test whether a work is currently pending or running
3175 * @work: the work to be tested
3177 * Test whether @work is currently pending or running. There is no
3178 * synchronization around this function and the test result is
3179 * unreliable and only useful as advisory hints or for debugging.
3180 * Especially for reentrant wqs, the pending state might hide the
3184 * OR'd bitmask of WORK_BUSY_* bits.
3186 unsigned int work_busy(struct work_struct *work)
3188 struct global_cwq *gcwq = get_work_gcwq(work);
3189 unsigned long flags;
3190 unsigned int ret = 0;
3195 spin_lock_irqsave(&gcwq->lock, flags);
3197 if (work_pending(work))
3198 ret |= WORK_BUSY_PENDING;
3199 if (find_worker_executing_work(gcwq, work))
3200 ret |= WORK_BUSY_RUNNING;
3202 spin_unlock_irqrestore(&gcwq->lock, flags);
3206 EXPORT_SYMBOL_GPL(work_busy);
3211 * There are two challenges in supporting CPU hotplug. Firstly, there
3212 * are a lot of assumptions on strong associations among work, cwq and
3213 * gcwq which make migrating pending and scheduled works very
3214 * difficult to implement without impacting hot paths. Secondly,
3215 * gcwqs serve mix of short, long and very long running works making
3216 * blocked draining impractical.
3218 * This is solved by allowing a gcwq to be detached from CPU, running
3219 * it with unbound (rogue) workers and allowing it to be reattached
3220 * later if the cpu comes back online. A separate thread is created
3221 * to govern a gcwq in such state and is called the trustee of the
3224 * Trustee states and their descriptions.
3226 * START Command state used on startup. On CPU_DOWN_PREPARE, a
3227 * new trustee is started with this state.
3229 * IN_CHARGE Once started, trustee will enter this state after
3230 * assuming the manager role and making all existing
3231 * workers rogue. DOWN_PREPARE waits for trustee to
3232 * enter this state. After reaching IN_CHARGE, trustee
3233 * tries to execute the pending worklist until it's empty
3234 * and the state is set to BUTCHER, or the state is set
3237 * BUTCHER Command state which is set by the cpu callback after
3238 * the cpu has went down. Once this state is set trustee
3239 * knows that there will be no new works on the worklist
3240 * and once the worklist is empty it can proceed to
3241 * killing idle workers.
3243 * RELEASE Command state which is set by the cpu callback if the
3244 * cpu down has been canceled or it has come online
3245 * again. After recognizing this state, trustee stops
3246 * trying to drain or butcher and clears ROGUE, rebinds
3247 * all remaining workers back to the cpu and releases
3250 * DONE Trustee will enter this state after BUTCHER or RELEASE
3253 * trustee CPU draining
3254 * took over down complete
3255 * START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE
3257 * | CPU is back online v return workers |
3258 * ----------------> RELEASE --------------
3262 * trustee_wait_event_timeout - timed event wait for trustee
3263 * @cond: condition to wait for
3264 * @timeout: timeout in jiffies
3266 * wait_event_timeout() for trustee to use. Handles locking and
3267 * checks for RELEASE request.
3270 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3271 * multiple times. To be used by trustee.
3274 * Positive indicating left time if @cond is satisfied, 0 if timed
3275 * out, -1 if canceled.
3277 #define trustee_wait_event_timeout(cond, timeout) ({ \
3278 long __ret = (timeout); \
3279 while (!((cond) || (gcwq->trustee_state == TRUSTEE_RELEASE)) && \
3281 spin_unlock_irq(&gcwq->lock); \
3282 __wait_event_timeout(gcwq->trustee_wait, (cond) || \
3283 (gcwq->trustee_state == TRUSTEE_RELEASE), \
3285 spin_lock_irq(&gcwq->lock); \
3287 gcwq->trustee_state == TRUSTEE_RELEASE ? -1 : (__ret); \
3291 * trustee_wait_event - event wait for trustee
3292 * @cond: condition to wait for
3294 * wait_event() for trustee to use. Automatically handles locking and
3295 * checks for CANCEL request.
3298 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3299 * multiple times. To be used by trustee.
3302 * 0 if @cond is satisfied, -1 if canceled.
3304 #define trustee_wait_event(cond) ({ \
3306 __ret1 = trustee_wait_event_timeout(cond, MAX_SCHEDULE_TIMEOUT);\
3307 __ret1 < 0 ? -1 : 0; \
3310 static bool gcwq_is_managing_workers(struct global_cwq *gcwq)
3312 struct worker_pool *pool;
3314 for_each_worker_pool(pool, gcwq)
3315 if (pool->flags & POOL_MANAGING_WORKERS)
3320 static bool gcwq_has_idle_workers(struct global_cwq *gcwq)
3322 struct worker_pool *pool;
3324 for_each_worker_pool(pool, gcwq)
3325 if (!list_empty(&pool->idle_list))
3330 static int __cpuinit trustee_thread(void *__gcwq)
3332 struct global_cwq *gcwq = __gcwq;
3333 struct worker_pool *pool;
3334 struct worker *worker;
3335 struct work_struct *work;
3336 struct hlist_node *pos;
3340 BUG_ON(gcwq->cpu != smp_processor_id());
3342 spin_lock_irq(&gcwq->lock);
3344 * Claim the manager position and make all workers rogue.
3345 * Trustee must be bound to the target cpu and can't be
3348 BUG_ON(gcwq->cpu != smp_processor_id());
3349 rc = trustee_wait_event(!gcwq_is_managing_workers(gcwq));
3352 for_each_worker_pool(pool, gcwq) {
3353 pool->flags |= POOL_MANAGING_WORKERS;
3355 list_for_each_entry(worker, &pool->idle_list, entry)
3356 worker->flags |= WORKER_ROGUE;
3359 for_each_busy_worker(worker, i, pos, gcwq)
3360 worker->flags |= WORKER_ROGUE;
3363 * Call schedule() so that we cross rq->lock and thus can
3364 * guarantee sched callbacks see the rogue flag. This is
3365 * necessary as scheduler callbacks may be invoked from other
3368 spin_unlock_irq(&gcwq->lock);
3370 spin_lock_irq(&gcwq->lock);
3373 * Sched callbacks are disabled now. Zap nr_running. After
3374 * this, nr_running stays zero and need_more_worker() and
3375 * keep_working() are always true as long as the worklist is
3378 for_each_worker_pool(pool, gcwq)
3379 atomic_set(get_pool_nr_running(pool), 0);
3381 spin_unlock_irq(&gcwq->lock);
3382 for_each_worker_pool(pool, gcwq)
3383 del_timer_sync(&pool->idle_timer);
3384 spin_lock_irq(&gcwq->lock);
3387 * We're now in charge. Notify and proceed to drain. We need
3388 * to keep the gcwq running during the whole CPU down
3389 * procedure as other cpu hotunplug callbacks may need to
3390 * flush currently running tasks.
3392 gcwq->trustee_state = TRUSTEE_IN_CHARGE;
3393 wake_up_all(&gcwq->trustee_wait);
3396 * The original cpu is in the process of dying and may go away
3397 * anytime now. When that happens, we and all workers would
3398 * be migrated to other cpus. Try draining any left work. We
3399 * want to get it over with ASAP - spam rescuers, wake up as
3400 * many idlers as necessary and create new ones till the
3401 * worklist is empty. Note that if the gcwq is frozen, there
3402 * may be frozen works in freezable cwqs. Don't declare
3403 * completion while frozen.
3408 for_each_worker_pool(pool, gcwq)
3409 busy |= pool->nr_workers != pool->nr_idle;
3411 if (!busy && !(gcwq->flags & GCWQ_FREEZING) &&
3412 gcwq->trustee_state != TRUSTEE_IN_CHARGE)
3415 for_each_worker_pool(pool, gcwq) {
3418 list_for_each_entry(work, &pool->worklist, entry) {
3423 list_for_each_entry(worker, &pool->idle_list, entry) {
3426 wake_up_process(worker->task);
3429 if (need_to_create_worker(pool)) {
3430 spin_unlock_irq(&gcwq->lock);
3431 worker = create_worker(pool, false);
3432 spin_lock_irq(&gcwq->lock);
3434 worker->flags |= WORKER_ROGUE;
3435 start_worker(worker);
3440 /* give a breather */
3441 if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0)
3446 * Either all works have been scheduled and cpu is down, or
3447 * cpu down has already been canceled. Wait for and butcher
3448 * all workers till we're canceled.
3451 rc = trustee_wait_event(gcwq_has_idle_workers(gcwq));
3454 for_each_worker_pool(pool, gcwq) {
3455 while (!list_empty(&pool->idle_list)) {
3456 worker = list_first_entry(&pool->idle_list,
3457 struct worker, entry);
3458 destroy_worker(worker);
3460 i |= pool->nr_workers;
3462 } while (i && rc >= 0);
3465 * At this point, either draining has completed and no worker
3466 * is left, or cpu down has been canceled or the cpu is being
3467 * brought back up. There shouldn't be any idle one left.
3468 * Tell the remaining busy ones to rebind once it finishes the
3469 * currently scheduled works by scheduling the rebind_work.
3471 for_each_worker_pool(pool, gcwq)
3472 WARN_ON(!list_empty(&pool->idle_list));
3474 for_each_busy_worker(worker, i, pos, gcwq) {
3475 struct work_struct *rebind_work = &worker->rebind_work;
3478 * Rebind_work may race with future cpu hotplug
3479 * operations. Use a separate flag to mark that
3480 * rebinding is scheduled.
3482 worker->flags |= WORKER_REBIND;
3483 worker->flags &= ~WORKER_ROGUE;
3485 /* queue rebind_work, wq doesn't matter, use the default one */
3486 if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
3487 work_data_bits(rebind_work)))
3490 debug_work_activate(rebind_work);
3491 insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work,
3492 worker->scheduled.next,
3493 work_color_to_flags(WORK_NO_COLOR));
3496 /* relinquish manager role */
3497 for_each_worker_pool(pool, gcwq)
3498 pool->flags &= ~POOL_MANAGING_WORKERS;
3500 /* notify completion */
3501 gcwq->trustee = NULL;
3502 gcwq->trustee_state = TRUSTEE_DONE;
3503 wake_up_all(&gcwq->trustee_wait);
3504 spin_unlock_irq(&gcwq->lock);
3509 * wait_trustee_state - wait for trustee to enter the specified state
3510 * @gcwq: gcwq the trustee of interest belongs to
3511 * @state: target state to wait for
3513 * Wait for the trustee to reach @state. DONE is already matched.
3516 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3517 * multiple times. To be used by cpu_callback.
3519 static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state)
3520 __releases(&gcwq->lock)
3521 __acquires(&gcwq->lock)
3523 if (!(gcwq->trustee_state == state ||
3524 gcwq->trustee_state == TRUSTEE_DONE)) {
3525 spin_unlock_irq(&gcwq->lock);
3526 __wait_event(gcwq->trustee_wait,
3527 gcwq->trustee_state == state ||
3528 gcwq->trustee_state == TRUSTEE_DONE);
3529 spin_lock_irq(&gcwq->lock);
3533 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
3534 unsigned long action,
3537 unsigned int cpu = (unsigned long)hcpu;
3538 struct global_cwq *gcwq = get_gcwq(cpu);
3539 struct task_struct *new_trustee = NULL;
3540 struct worker *new_workers[NR_WORKER_POOLS] = { };
3541 struct worker_pool *pool;
3542 unsigned long flags;
3545 action &= ~CPU_TASKS_FROZEN;
3548 case CPU_DOWN_PREPARE:
3549 new_trustee = kthread_create(trustee_thread, gcwq,
3550 "workqueue_trustee/%d\n", cpu);
3551 if (IS_ERR(new_trustee))
3552 return notifier_from_errno(PTR_ERR(new_trustee));
3553 kthread_bind(new_trustee, cpu);
3555 case CPU_UP_PREPARE:
3557 for_each_worker_pool(pool, gcwq) {
3558 BUG_ON(pool->first_idle);
3559 new_workers[i] = create_worker(pool, false);
3560 if (!new_workers[i++])
3565 /* some are called w/ irq disabled, don't disturb irq status */
3566 spin_lock_irqsave(&gcwq->lock, flags);
3569 case CPU_DOWN_PREPARE:
3570 /* initialize trustee and tell it to acquire the gcwq */
3571 BUG_ON(gcwq->trustee || gcwq->trustee_state != TRUSTEE_DONE);
3572 gcwq->trustee = new_trustee;
3573 gcwq->trustee_state = TRUSTEE_START;
3574 wake_up_process(gcwq->trustee);
3575 wait_trustee_state(gcwq, TRUSTEE_IN_CHARGE);
3577 case CPU_UP_PREPARE:
3579 for_each_worker_pool(pool, gcwq) {
3580 BUG_ON(pool->first_idle);
3581 pool->first_idle = new_workers[i++];
3587 * Before this, the trustee and all workers except for
3588 * the ones which are still executing works from
3589 * before the last CPU down must be on the cpu. After
3590 * this, they'll all be diasporas.
3592 gcwq->flags |= GCWQ_DISASSOCIATED;
3596 gcwq->trustee_state = TRUSTEE_BUTCHER;
3598 case CPU_UP_CANCELED:
3599 for_each_worker_pool(pool, gcwq) {
3600 destroy_worker(pool->first_idle);
3601 pool->first_idle = NULL;
3605 case CPU_DOWN_FAILED:
3607 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3608 if (gcwq->trustee_state != TRUSTEE_DONE) {
3609 gcwq->trustee_state = TRUSTEE_RELEASE;
3610 wake_up_process(gcwq->trustee);
3611 wait_trustee_state(gcwq, TRUSTEE_DONE);
3615 * Trustee is done and there might be no worker left.
3616 * Put the first_idle in and request a real manager to
3619 for_each_worker_pool(pool, gcwq) {
3620 spin_unlock_irq(&gcwq->lock);
3621 kthread_bind(pool->first_idle->task, cpu);
3622 spin_lock_irq(&gcwq->lock);
3623 pool->flags |= POOL_MANAGE_WORKERS;
3624 start_worker(pool->first_idle);
3625 pool->first_idle = NULL;
3630 spin_unlock_irqrestore(&gcwq->lock, flags);
3632 return notifier_from_errno(0);
3636 kthread_stop(new_trustee);
3638 spin_lock_irqsave(&gcwq->lock, flags);
3639 for (i = 0; i < NR_WORKER_POOLS; i++)
3641 destroy_worker(new_workers[i]);
3642 spin_unlock_irqrestore(&gcwq->lock, flags);
3649 struct work_for_cpu {
3650 struct completion completion;
3656 static int do_work_for_cpu(void *_wfc)
3658 struct work_for_cpu *wfc = _wfc;
3659 wfc->ret = wfc->fn(wfc->arg);
3660 complete(&wfc->completion);
3665 * work_on_cpu - run a function in user context on a particular cpu
3666 * @cpu: the cpu to run on
3667 * @fn: the function to run
3668 * @arg: the function arg
3670 * This will return the value @fn returns.
3671 * It is up to the caller to ensure that the cpu doesn't go offline.
3672 * The caller must not hold any locks which would prevent @fn from completing.
3674 long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
3676 struct task_struct *sub_thread;
3677 struct work_for_cpu wfc = {
3678 .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
3683 sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
3684 if (IS_ERR(sub_thread))
3685 return PTR_ERR(sub_thread);
3686 kthread_bind(sub_thread, cpu);
3687 wake_up_process(sub_thread);
3688 wait_for_completion(&wfc.completion);
3691 EXPORT_SYMBOL_GPL(work_on_cpu);
3692 #endif /* CONFIG_SMP */
3694 #ifdef CONFIG_FREEZER
3697 * freeze_workqueues_begin - begin freezing workqueues
3699 * Start freezing workqueues. After this function returns, all freezable
3700 * workqueues will queue new works to their frozen_works list instead of
3704 * Grabs and releases workqueue_lock and gcwq->lock's.
3706 void freeze_workqueues_begin(void)
3710 spin_lock(&workqueue_lock);
3712 BUG_ON(workqueue_freezing);
3713 workqueue_freezing = true;
3715 for_each_gcwq_cpu(cpu) {
3716 struct global_cwq *gcwq = get_gcwq(cpu);
3717 struct workqueue_struct *wq;
3719 spin_lock_irq(&gcwq->lock);
3721 BUG_ON(gcwq->flags & GCWQ_FREEZING);
3722 gcwq->flags |= GCWQ_FREEZING;
3724 list_for_each_entry(wq, &workqueues, list) {
3725 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3727 if (cwq && wq->flags & WQ_FREEZABLE)
3728 cwq->max_active = 0;
3731 spin_unlock_irq(&gcwq->lock);
3734 spin_unlock(&workqueue_lock);
3738 * freeze_workqueues_busy - are freezable workqueues still busy?
3740 * Check whether freezing is complete. This function must be called
3741 * between freeze_workqueues_begin() and thaw_workqueues().
3744 * Grabs and releases workqueue_lock.
3747 * %true if some freezable workqueues are still busy. %false if freezing
3750 bool freeze_workqueues_busy(void)
3755 spin_lock(&workqueue_lock);
3757 BUG_ON(!workqueue_freezing);
3759 for_each_gcwq_cpu(cpu) {
3760 struct workqueue_struct *wq;
3762 * nr_active is monotonically decreasing. It's safe
3763 * to peek without lock.
3765 list_for_each_entry(wq, &workqueues, list) {
3766 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3768 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3771 BUG_ON(cwq->nr_active < 0);
3772 if (cwq->nr_active) {
3779 spin_unlock(&workqueue_lock);
3784 * thaw_workqueues - thaw workqueues
3786 * Thaw workqueues. Normal queueing is restored and all collected
3787 * frozen works are transferred to their respective gcwq worklists.
3790 * Grabs and releases workqueue_lock and gcwq->lock's.
3792 void thaw_workqueues(void)
3796 spin_lock(&workqueue_lock);
3798 if (!workqueue_freezing)
3801 for_each_gcwq_cpu(cpu) {
3802 struct global_cwq *gcwq = get_gcwq(cpu);
3803 struct worker_pool *pool;
3804 struct workqueue_struct *wq;
3806 spin_lock_irq(&gcwq->lock);
3808 BUG_ON(!(gcwq->flags & GCWQ_FREEZING));
3809 gcwq->flags &= ~GCWQ_FREEZING;
3811 list_for_each_entry(wq, &workqueues, list) {
3812 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3814 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3817 /* restore max_active and repopulate worklist */
3818 cwq->max_active = wq->saved_max_active;
3820 while (!list_empty(&cwq->delayed_works) &&
3821 cwq->nr_active < cwq->max_active)
3822 cwq_activate_first_delayed(cwq);
3825 for_each_worker_pool(pool, gcwq)
3826 wake_up_worker(pool);
3828 spin_unlock_irq(&gcwq->lock);
3831 workqueue_freezing = false;
3833 spin_unlock(&workqueue_lock);
3835 #endif /* CONFIG_FREEZER */
3837 static int __init init_workqueues(void)
3842 cpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE);
3844 /* initialize gcwqs */
3845 for_each_gcwq_cpu(cpu) {
3846 struct global_cwq *gcwq = get_gcwq(cpu);
3847 struct worker_pool *pool;
3849 spin_lock_init(&gcwq->lock);
3851 gcwq->flags |= GCWQ_DISASSOCIATED;
3853 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
3854 INIT_HLIST_HEAD(&gcwq->busy_hash[i]);
3856 for_each_worker_pool(pool, gcwq) {
3858 INIT_LIST_HEAD(&pool->worklist);
3859 INIT_LIST_HEAD(&pool->idle_list);
3861 init_timer_deferrable(&pool->idle_timer);
3862 pool->idle_timer.function = idle_worker_timeout;
3863 pool->idle_timer.data = (unsigned long)pool;
3865 setup_timer(&pool->mayday_timer, gcwq_mayday_timeout,
3866 (unsigned long)pool);
3868 ida_init(&pool->worker_ida);
3871 gcwq->trustee_state = TRUSTEE_DONE;
3872 init_waitqueue_head(&gcwq->trustee_wait);
3875 /* create the initial worker */
3876 for_each_online_gcwq_cpu(cpu) {
3877 struct global_cwq *gcwq = get_gcwq(cpu);
3878 struct worker_pool *pool;
3880 if (cpu != WORK_CPU_UNBOUND)
3881 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3883 for_each_worker_pool(pool, gcwq) {
3884 struct worker *worker;
3886 worker = create_worker(pool, true);
3888 spin_lock_irq(&gcwq->lock);
3889 start_worker(worker);
3890 spin_unlock_irq(&gcwq->lock);
3894 system_wq = alloc_workqueue("events", 0, 0);
3895 system_long_wq = alloc_workqueue("events_long", 0, 0);
3896 system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0);
3897 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
3898 WQ_UNBOUND_MAX_ACTIVE);
3899 system_freezable_wq = alloc_workqueue("events_freezable",
3901 system_nrt_freezable_wq = alloc_workqueue("events_nrt_freezable",
3902 WQ_NON_REENTRANT | WQ_FREEZABLE, 0);
3903 BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
3904 !system_unbound_wq || !system_freezable_wq ||
3905 !system_nrt_freezable_wq);
3908 early_initcall(init_workqueues);