gma500: Fix backlight crash
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / workqueue.c
blob0400553f0d049807d109e9cc87d7a5dc2c0dcc99
1 /*
2 * kernel/workqueue.c - generic async execution with shared worker pool
4 * Copyright (C) 2002 Ingo Molnar
6 * Derived from the taskqueue/keventd code by:
7 * David Woodhouse <dwmw2@infradead.org>
8 * Andrew Morton
9 * Kai Petzke <wpp@marie.physik.tu-berlin.de>
10 * Theodore Ts'o <tytso@mit.edu>
12 * Made to use alloc_percpu by Christoph Lameter.
14 * Copyright (C) 2010 SUSE Linux Products GmbH
15 * Copyright (C) 2010 Tejun Heo <tj@kernel.org>
17 * This is the generic async execution mechanism. Work items as are
18 * executed in process context. The worker pool is shared and
19 * automatically managed. There 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/module.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"
47 enum {
48 /* global_cwq flags */
49 GCWQ_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
50 GCWQ_MANAGING_WORKERS = 1 << 1, /* managing workers */
51 GCWQ_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
52 GCWQ_FREEZING = 1 << 3, /* freeze in progress */
53 GCWQ_HIGHPRI_PENDING = 1 << 4, /* highpri works on queue */
55 /* worker flags */
56 WORKER_STARTED = 1 << 0, /* started */
57 WORKER_DIE = 1 << 1, /* die die die */
58 WORKER_IDLE = 1 << 2, /* is idle */
59 WORKER_PREP = 1 << 3, /* preparing to run works */
60 WORKER_ROGUE = 1 << 4, /* not bound to any cpu */
61 WORKER_REBIND = 1 << 5, /* mom is home, come back */
62 WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
63 WORKER_UNBOUND = 1 << 7, /* worker is unbound */
65 WORKER_NOT_RUNNING = WORKER_PREP | WORKER_ROGUE | WORKER_REBIND |
66 WORKER_CPU_INTENSIVE | WORKER_UNBOUND,
68 /* gcwq->trustee_state */
69 TRUSTEE_START = 0, /* start */
70 TRUSTEE_IN_CHARGE = 1, /* trustee in charge of gcwq */
71 TRUSTEE_BUTCHER = 2, /* butcher workers */
72 TRUSTEE_RELEASE = 3, /* release workers */
73 TRUSTEE_DONE = 4, /* trustee is done */
75 BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */
76 BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER,
77 BUSY_WORKER_HASH_MASK = BUSY_WORKER_HASH_SIZE - 1,
79 MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */
80 IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */
82 MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2,
83 /* call for help after 10ms
84 (min two ticks) */
85 MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */
86 CREATE_COOLDOWN = HZ, /* time to breath after fail */
87 TRUSTEE_COOLDOWN = HZ / 10, /* for trustee draining */
90 * Rescue workers are used only on emergencies and shared by
91 * all cpus. Give -20.
93 RESCUER_NICE_LEVEL = -20,
97 * Structure fields follow one of the following exclusion rules.
99 * I: Modifiable by initialization/destruction paths and read-only for
100 * everyone else.
102 * P: Preemption protected. Disabling preemption is enough and should
103 * only be modified and accessed from the local cpu.
105 * L: gcwq->lock protected. Access with gcwq->lock held.
107 * X: During normal operation, modification requires gcwq->lock and
108 * should be done only from local cpu. Either disabling preemption
109 * on local cpu or grabbing gcwq->lock is enough for read access.
110 * If GCWQ_DISASSOCIATED is set, it's identical to L.
112 * F: wq->flush_mutex protected.
114 * W: workqueue_lock protected.
117 struct global_cwq;
120 * The poor guys doing the actual heavy lifting. All on-duty workers
121 * are either serving the manager role, on idle list or on busy hash.
123 struct worker {
124 /* on idle list while idle, on busy hash table while busy */
125 union {
126 struct list_head entry; /* L: while idle */
127 struct hlist_node hentry; /* L: while busy */
130 struct work_struct *current_work; /* L: work being processed */
131 struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */
132 struct list_head scheduled; /* L: scheduled works */
133 struct task_struct *task; /* I: worker task */
134 struct global_cwq *gcwq; /* I: the associated gcwq */
135 /* 64 bytes boundary on 64bit, 32 on 32bit */
136 unsigned long last_active; /* L: last active timestamp */
137 unsigned int flags; /* X: flags */
138 int id; /* I: worker id */
139 struct work_struct rebind_work; /* L: rebind worker to cpu */
143 * Global per-cpu workqueue. There's one and only one for each cpu
144 * and all works are queued and processed here regardless of their
145 * target workqueues.
147 struct global_cwq {
148 spinlock_t lock; /* the gcwq lock */
149 struct list_head worklist; /* L: list of pending works */
150 unsigned int cpu; /* I: the associated cpu */
151 unsigned int flags; /* L: GCWQ_* flags */
153 int nr_workers; /* L: total number of workers */
154 int nr_idle; /* L: currently idle ones */
156 /* workers are chained either in the idle_list or busy_hash */
157 struct list_head idle_list; /* X: list of idle workers */
158 struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE];
159 /* L: hash of busy workers */
161 struct timer_list idle_timer; /* L: worker idle timeout */
162 struct timer_list mayday_timer; /* L: SOS timer for dworkers */
164 struct ida worker_ida; /* L: for worker IDs */
166 struct task_struct *trustee; /* L: for gcwq shutdown */
167 unsigned int trustee_state; /* L: trustee state */
168 wait_queue_head_t trustee_wait; /* trustee wait */
169 struct worker *first_idle; /* L: first idle worker */
170 } ____cacheline_aligned_in_smp;
173 * The per-CPU workqueue. The lower WORK_STRUCT_FLAG_BITS of
174 * work_struct->data are used for flags and thus cwqs need to be
175 * aligned at two's power of the number of flag bits.
177 struct cpu_workqueue_struct {
178 struct global_cwq *gcwq; /* I: the associated gcwq */
179 struct workqueue_struct *wq; /* I: the owning workqueue */
180 int work_color; /* L: current color */
181 int flush_color; /* L: flushing color */
182 int nr_in_flight[WORK_NR_COLORS];
183 /* L: nr of in_flight works */
184 int nr_active; /* L: nr of active works */
185 int max_active; /* L: max active works */
186 struct list_head delayed_works; /* L: delayed works */
190 * Structure used to wait for workqueue flush.
192 struct wq_flusher {
193 struct list_head list; /* F: list of flushers */
194 int flush_color; /* F: flush color waiting for */
195 struct completion done; /* flush completion */
199 * All cpumasks are assumed to be always set on UP and thus can't be
200 * used to determine whether there's something to be done.
202 #ifdef CONFIG_SMP
203 typedef cpumask_var_t mayday_mask_t;
204 #define mayday_test_and_set_cpu(cpu, mask) \
205 cpumask_test_and_set_cpu((cpu), (mask))
206 #define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask))
207 #define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask))
208 #define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp))
209 #define free_mayday_mask(mask) free_cpumask_var((mask))
210 #else
211 typedef unsigned long mayday_mask_t;
212 #define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask))
213 #define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask))
214 #define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask))
215 #define alloc_mayday_mask(maskp, gfp) true
216 #define free_mayday_mask(mask) do { } while (0)
217 #endif
220 * The externally visible workqueue abstraction is an array of
221 * per-CPU workqueues:
223 struct workqueue_struct {
224 unsigned int flags; /* I: WQ_* flags */
225 union {
226 struct cpu_workqueue_struct __percpu *pcpu;
227 struct cpu_workqueue_struct *single;
228 unsigned long v;
229 } cpu_wq; /* I: cwq's */
230 struct list_head list; /* W: list of all workqueues */
232 struct mutex flush_mutex; /* protects wq flushing */
233 int work_color; /* F: current work color */
234 int flush_color; /* F: current flush color */
235 atomic_t nr_cwqs_to_flush; /* flush in progress */
236 struct wq_flusher *first_flusher; /* F: first flusher */
237 struct list_head flusher_queue; /* F: flush waiters */
238 struct list_head flusher_overflow; /* F: flush overflow list */
240 mayday_mask_t mayday_mask; /* cpus requesting rescue */
241 struct worker *rescuer; /* I: rescue worker */
243 int saved_max_active; /* W: saved cwq max_active */
244 const char *name; /* I: workqueue name */
245 #ifdef CONFIG_LOCKDEP
246 struct lockdep_map lockdep_map;
247 #endif
250 struct workqueue_struct *system_wq __read_mostly;
251 struct workqueue_struct *system_long_wq __read_mostly;
252 struct workqueue_struct *system_nrt_wq __read_mostly;
253 struct workqueue_struct *system_unbound_wq __read_mostly;
254 struct workqueue_struct *system_freezable_wq __read_mostly;
255 EXPORT_SYMBOL_GPL(system_wq);
256 EXPORT_SYMBOL_GPL(system_long_wq);
257 EXPORT_SYMBOL_GPL(system_nrt_wq);
258 EXPORT_SYMBOL_GPL(system_unbound_wq);
259 EXPORT_SYMBOL_GPL(system_freezable_wq);
261 #define CREATE_TRACE_POINTS
262 #include <trace/events/workqueue.h>
264 #define for_each_busy_worker(worker, i, pos, gcwq) \
265 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \
266 hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry)
268 static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask,
269 unsigned int sw)
271 if (cpu < nr_cpu_ids) {
272 if (sw & 1) {
273 cpu = cpumask_next(cpu, mask);
274 if (cpu < nr_cpu_ids)
275 return cpu;
277 if (sw & 2)
278 return WORK_CPU_UNBOUND;
280 return WORK_CPU_NONE;
283 static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
284 struct workqueue_struct *wq)
286 return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2);
290 * CPU iterators
292 * An extra gcwq is defined for an invalid cpu number
293 * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
294 * specific CPU. The following iterators are similar to
295 * for_each_*_cpu() iterators but also considers the unbound gcwq.
297 * for_each_gcwq_cpu() : possible CPUs + WORK_CPU_UNBOUND
298 * for_each_online_gcwq_cpu() : online CPUs + WORK_CPU_UNBOUND
299 * for_each_cwq_cpu() : possible CPUs for bound workqueues,
300 * WORK_CPU_UNBOUND for unbound workqueues
302 #define for_each_gcwq_cpu(cpu) \
303 for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3); \
304 (cpu) < WORK_CPU_NONE; \
305 (cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3))
307 #define for_each_online_gcwq_cpu(cpu) \
308 for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3); \
309 (cpu) < WORK_CPU_NONE; \
310 (cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3))
312 #define for_each_cwq_cpu(cpu, wq) \
313 for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq)); \
314 (cpu) < WORK_CPU_NONE; \
315 (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq)))
317 #ifdef CONFIG_DEBUG_OBJECTS_WORK
319 static struct debug_obj_descr work_debug_descr;
321 static void *work_debug_hint(void *addr)
323 return ((struct work_struct *) addr)->func;
327 * fixup_init is called when:
328 * - an active object is initialized
330 static int work_fixup_init(void *addr, enum debug_obj_state state)
332 struct work_struct *work = addr;
334 switch (state) {
335 case ODEBUG_STATE_ACTIVE:
336 cancel_work_sync(work);
337 debug_object_init(work, &work_debug_descr);
338 return 1;
339 default:
340 return 0;
345 * fixup_activate is called when:
346 * - an active object is activated
347 * - an unknown object is activated (might be a statically initialized object)
349 static int work_fixup_activate(void *addr, enum debug_obj_state state)
351 struct work_struct *work = addr;
353 switch (state) {
355 case ODEBUG_STATE_NOTAVAILABLE:
357 * This is not really a fixup. The work struct was
358 * statically initialized. We just make sure that it
359 * is tracked in the object tracker.
361 if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) {
362 debug_object_init(work, &work_debug_descr);
363 debug_object_activate(work, &work_debug_descr);
364 return 0;
366 WARN_ON_ONCE(1);
367 return 0;
369 case ODEBUG_STATE_ACTIVE:
370 WARN_ON(1);
372 default:
373 return 0;
378 * fixup_free is called when:
379 * - an active object is freed
381 static int work_fixup_free(void *addr, enum debug_obj_state state)
383 struct work_struct *work = addr;
385 switch (state) {
386 case ODEBUG_STATE_ACTIVE:
387 cancel_work_sync(work);
388 debug_object_free(work, &work_debug_descr);
389 return 1;
390 default:
391 return 0;
395 static struct debug_obj_descr work_debug_descr = {
396 .name = "work_struct",
397 .debug_hint = work_debug_hint,
398 .fixup_init = work_fixup_init,
399 .fixup_activate = work_fixup_activate,
400 .fixup_free = work_fixup_free,
403 static inline void debug_work_activate(struct work_struct *work)
405 debug_object_activate(work, &work_debug_descr);
408 static inline void debug_work_deactivate(struct work_struct *work)
410 debug_object_deactivate(work, &work_debug_descr);
413 void __init_work(struct work_struct *work, int onstack)
415 if (onstack)
416 debug_object_init_on_stack(work, &work_debug_descr);
417 else
418 debug_object_init(work, &work_debug_descr);
420 EXPORT_SYMBOL_GPL(__init_work);
422 void destroy_work_on_stack(struct work_struct *work)
424 debug_object_free(work, &work_debug_descr);
426 EXPORT_SYMBOL_GPL(destroy_work_on_stack);
428 #else
429 static inline void debug_work_activate(struct work_struct *work) { }
430 static inline void debug_work_deactivate(struct work_struct *work) { }
431 #endif
433 /* Serializes the accesses to the list of workqueues. */
434 static DEFINE_SPINLOCK(workqueue_lock);
435 static LIST_HEAD(workqueues);
436 static bool workqueue_freezing; /* W: have wqs started freezing? */
439 * The almighty global cpu workqueues. nr_running is the only field
440 * which is expected to be used frequently by other cpus via
441 * try_to_wake_up(). Put it in a separate cacheline.
443 static DEFINE_PER_CPU(struct global_cwq, global_cwq);
444 static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, gcwq_nr_running);
447 * Global cpu workqueue and nr_running counter for unbound gcwq. The
448 * gcwq is always online, has GCWQ_DISASSOCIATED set, and all its
449 * workers have WORKER_UNBOUND set.
451 static struct global_cwq unbound_global_cwq;
452 static atomic_t unbound_gcwq_nr_running = ATOMIC_INIT(0); /* always 0 */
454 static int worker_thread(void *__worker);
456 static struct global_cwq *get_gcwq(unsigned int cpu)
458 if (cpu != WORK_CPU_UNBOUND)
459 return &per_cpu(global_cwq, cpu);
460 else
461 return &unbound_global_cwq;
464 static atomic_t *get_gcwq_nr_running(unsigned int cpu)
466 if (cpu != WORK_CPU_UNBOUND)
467 return &per_cpu(gcwq_nr_running, cpu);
468 else
469 return &unbound_gcwq_nr_running;
472 static struct cpu_workqueue_struct *get_cwq(unsigned int cpu,
473 struct workqueue_struct *wq)
475 if (!(wq->flags & WQ_UNBOUND)) {
476 if (likely(cpu < nr_cpu_ids)) {
477 #ifdef CONFIG_SMP
478 return per_cpu_ptr(wq->cpu_wq.pcpu, cpu);
479 #else
480 return wq->cpu_wq.single;
481 #endif
483 } else if (likely(cpu == WORK_CPU_UNBOUND))
484 return wq->cpu_wq.single;
485 return NULL;
488 static unsigned int work_color_to_flags(int color)
490 return color << WORK_STRUCT_COLOR_SHIFT;
493 static int get_work_color(struct work_struct *work)
495 return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) &
496 ((1 << WORK_STRUCT_COLOR_BITS) - 1);
499 static int work_next_color(int color)
501 return (color + 1) % WORK_NR_COLORS;
505 * A work's data points to the cwq with WORK_STRUCT_CWQ set while the
506 * work is on queue. Once execution starts, WORK_STRUCT_CWQ is
507 * cleared and the work data contains the cpu number it was last on.
509 * set_work_{cwq|cpu}() and clear_work_data() can be used to set the
510 * cwq, cpu or clear work->data. These functions should only be
511 * called while the work is owned - ie. while the PENDING bit is set.
513 * get_work_[g]cwq() can be used to obtain the gcwq or cwq
514 * corresponding to a work. gcwq is available once the work has been
515 * queued anywhere after initialization. cwq is available only from
516 * queueing until execution starts.
518 static inline void set_work_data(struct work_struct *work, unsigned long data,
519 unsigned long flags)
521 BUG_ON(!work_pending(work));
522 atomic_long_set(&work->data, data | flags | work_static(work));
525 static void set_work_cwq(struct work_struct *work,
526 struct cpu_workqueue_struct *cwq,
527 unsigned long extra_flags)
529 set_work_data(work, (unsigned long)cwq,
530 WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags);
533 static void set_work_cpu(struct work_struct *work, unsigned int cpu)
535 set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, WORK_STRUCT_PENDING);
538 static void clear_work_data(struct work_struct *work)
540 set_work_data(work, WORK_STRUCT_NO_CPU, 0);
543 static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work)
545 unsigned long data = atomic_long_read(&work->data);
547 if (data & WORK_STRUCT_CWQ)
548 return (void *)(data & WORK_STRUCT_WQ_DATA_MASK);
549 else
550 return NULL;
553 static struct global_cwq *get_work_gcwq(struct work_struct *work)
555 unsigned long data = atomic_long_read(&work->data);
556 unsigned int cpu;
558 if (data & WORK_STRUCT_CWQ)
559 return ((struct cpu_workqueue_struct *)
560 (data & WORK_STRUCT_WQ_DATA_MASK))->gcwq;
562 cpu = data >> WORK_STRUCT_FLAG_BITS;
563 if (cpu == WORK_CPU_NONE)
564 return NULL;
566 BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND);
567 return get_gcwq(cpu);
571 * Policy functions. These define the policies on how the global
572 * worker pool is managed. Unless noted otherwise, these functions
573 * assume that they're being called with gcwq->lock held.
576 static bool __need_more_worker(struct global_cwq *gcwq)
578 return !atomic_read(get_gcwq_nr_running(gcwq->cpu)) ||
579 gcwq->flags & GCWQ_HIGHPRI_PENDING;
583 * Need to wake up a worker? Called from anything but currently
584 * running workers.
586 static bool need_more_worker(struct global_cwq *gcwq)
588 return !list_empty(&gcwq->worklist) && __need_more_worker(gcwq);
591 /* Can I start working? Called from busy but !running workers. */
592 static bool may_start_working(struct global_cwq *gcwq)
594 return gcwq->nr_idle;
597 /* Do I need to keep working? Called from currently running workers. */
598 static bool keep_working(struct global_cwq *gcwq)
600 atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
602 return !list_empty(&gcwq->worklist) &&
603 (atomic_read(nr_running) <= 1 ||
604 gcwq->flags & GCWQ_HIGHPRI_PENDING);
607 /* Do we need a new worker? Called from manager. */
608 static bool need_to_create_worker(struct global_cwq *gcwq)
610 return need_more_worker(gcwq) && !may_start_working(gcwq);
613 /* Do I need to be the manager? */
614 static bool need_to_manage_workers(struct global_cwq *gcwq)
616 return need_to_create_worker(gcwq) || gcwq->flags & GCWQ_MANAGE_WORKERS;
619 /* Do we have too many workers and should some go away? */
620 static bool too_many_workers(struct global_cwq *gcwq)
622 bool managing = gcwq->flags & GCWQ_MANAGING_WORKERS;
623 int nr_idle = gcwq->nr_idle + managing; /* manager is considered idle */
624 int nr_busy = gcwq->nr_workers - nr_idle;
626 return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy;
630 * Wake up functions.
633 /* Return the first worker. Safe with preemption disabled */
634 static struct worker *first_worker(struct global_cwq *gcwq)
636 if (unlikely(list_empty(&gcwq->idle_list)))
637 return NULL;
639 return list_first_entry(&gcwq->idle_list, struct worker, entry);
643 * wake_up_worker - wake up an idle worker
644 * @gcwq: gcwq to wake worker for
646 * Wake up the first idle worker of @gcwq.
648 * CONTEXT:
649 * spin_lock_irq(gcwq->lock).
651 static void wake_up_worker(struct global_cwq *gcwq)
653 struct worker *worker = first_worker(gcwq);
655 if (likely(worker))
656 wake_up_process(worker->task);
660 * wq_worker_waking_up - a worker is waking up
661 * @task: task waking up
662 * @cpu: CPU @task is waking up to
664 * This function is called during try_to_wake_up() when a worker is
665 * being awoken.
667 * CONTEXT:
668 * spin_lock_irq(rq->lock)
670 void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
672 struct worker *worker = kthread_data(task);
674 if (!(worker->flags & WORKER_NOT_RUNNING))
675 atomic_inc(get_gcwq_nr_running(cpu));
679 * wq_worker_sleeping - a worker is going to sleep
680 * @task: task going to sleep
681 * @cpu: CPU in question, must be the current CPU number
683 * This function is called during schedule() when a busy worker is
684 * going to sleep. Worker on the same cpu can be woken up by
685 * returning pointer to its task.
687 * CONTEXT:
688 * spin_lock_irq(rq->lock)
690 * RETURNS:
691 * Worker task on @cpu to wake up, %NULL if none.
693 struct task_struct *wq_worker_sleeping(struct task_struct *task,
694 unsigned int cpu)
696 struct worker *worker = kthread_data(task), *to_wakeup = NULL;
697 struct global_cwq *gcwq = get_gcwq(cpu);
698 atomic_t *nr_running = get_gcwq_nr_running(cpu);
700 if (worker->flags & WORKER_NOT_RUNNING)
701 return NULL;
703 /* this can only happen on the local cpu */
704 BUG_ON(cpu != raw_smp_processor_id());
707 * The counterpart of the following dec_and_test, implied mb,
708 * worklist not empty test sequence is in insert_work().
709 * Please read comment there.
711 * NOT_RUNNING is clear. This means that trustee is not in
712 * charge and we're running on the local cpu w/ rq lock held
713 * and preemption disabled, which in turn means that none else
714 * could be manipulating idle_list, so dereferencing idle_list
715 * without gcwq lock is safe.
717 if (atomic_dec_and_test(nr_running) && !list_empty(&gcwq->worklist))
718 to_wakeup = first_worker(gcwq);
719 return to_wakeup ? to_wakeup->task : NULL;
723 * worker_set_flags - set worker flags and adjust nr_running accordingly
724 * @worker: self
725 * @flags: flags to set
726 * @wakeup: wakeup an idle worker if necessary
728 * Set @flags in @worker->flags and adjust nr_running accordingly. If
729 * nr_running becomes zero and @wakeup is %true, an idle worker is
730 * woken up.
732 * CONTEXT:
733 * spin_lock_irq(gcwq->lock)
735 static inline void worker_set_flags(struct worker *worker, unsigned int flags,
736 bool wakeup)
738 struct global_cwq *gcwq = worker->gcwq;
740 WARN_ON_ONCE(worker->task != current);
743 * If transitioning into NOT_RUNNING, adjust nr_running and
744 * wake up an idle worker as necessary if requested by
745 * @wakeup.
747 if ((flags & WORKER_NOT_RUNNING) &&
748 !(worker->flags & WORKER_NOT_RUNNING)) {
749 atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu);
751 if (wakeup) {
752 if (atomic_dec_and_test(nr_running) &&
753 !list_empty(&gcwq->worklist))
754 wake_up_worker(gcwq);
755 } else
756 atomic_dec(nr_running);
759 worker->flags |= flags;
763 * worker_clr_flags - clear worker flags and adjust nr_running accordingly
764 * @worker: self
765 * @flags: flags to clear
767 * Clear @flags in @worker->flags and adjust nr_running accordingly.
769 * CONTEXT:
770 * spin_lock_irq(gcwq->lock)
772 static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
774 struct global_cwq *gcwq = worker->gcwq;
775 unsigned int oflags = worker->flags;
777 WARN_ON_ONCE(worker->task != current);
779 worker->flags &= ~flags;
782 * If transitioning out of NOT_RUNNING, increment nr_running. Note
783 * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask
784 * of multiple flags, not a single flag.
786 if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING))
787 if (!(worker->flags & WORKER_NOT_RUNNING))
788 atomic_inc(get_gcwq_nr_running(gcwq->cpu));
792 * busy_worker_head - return the busy hash head for a work
793 * @gcwq: gcwq of interest
794 * @work: work to be hashed
796 * Return hash head of @gcwq for @work.
798 * CONTEXT:
799 * spin_lock_irq(gcwq->lock).
801 * RETURNS:
802 * Pointer to the hash head.
804 static struct hlist_head *busy_worker_head(struct global_cwq *gcwq,
805 struct work_struct *work)
807 const int base_shift = ilog2(sizeof(struct work_struct));
808 unsigned long v = (unsigned long)work;
810 /* simple shift and fold hash, do we need something better? */
811 v >>= base_shift;
812 v += v >> BUSY_WORKER_HASH_ORDER;
813 v &= BUSY_WORKER_HASH_MASK;
815 return &gcwq->busy_hash[v];
819 * __find_worker_executing_work - find worker which is executing a work
820 * @gcwq: gcwq of interest
821 * @bwh: hash head as returned by busy_worker_head()
822 * @work: work to find worker for
824 * Find a worker which is executing @work on @gcwq. @bwh should be
825 * the hash head obtained by calling busy_worker_head() with the same
826 * work.
828 * CONTEXT:
829 * spin_lock_irq(gcwq->lock).
831 * RETURNS:
832 * Pointer to worker which is executing @work if found, NULL
833 * otherwise.
835 static struct worker *__find_worker_executing_work(struct global_cwq *gcwq,
836 struct hlist_head *bwh,
837 struct work_struct *work)
839 struct worker *worker;
840 struct hlist_node *tmp;
842 hlist_for_each_entry(worker, tmp, bwh, hentry)
843 if (worker->current_work == work)
844 return worker;
845 return NULL;
849 * find_worker_executing_work - find worker which is executing a work
850 * @gcwq: gcwq of interest
851 * @work: work to find worker for
853 * Find a worker which is executing @work on @gcwq. This function is
854 * identical to __find_worker_executing_work() except that this
855 * function calculates @bwh itself.
857 * CONTEXT:
858 * spin_lock_irq(gcwq->lock).
860 * RETURNS:
861 * Pointer to worker which is executing @work if found, NULL
862 * otherwise.
864 static struct worker *find_worker_executing_work(struct global_cwq *gcwq,
865 struct work_struct *work)
867 return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work),
868 work);
872 * gcwq_determine_ins_pos - find insertion position
873 * @gcwq: gcwq of interest
874 * @cwq: cwq a work is being queued for
876 * A work for @cwq is about to be queued on @gcwq, determine insertion
877 * position for the work. If @cwq is for HIGHPRI wq, the work is
878 * queued at the head of the queue but in FIFO order with respect to
879 * other HIGHPRI works; otherwise, at the end of the queue. This
880 * function also sets GCWQ_HIGHPRI_PENDING flag to hint @gcwq that
881 * there are HIGHPRI works pending.
883 * CONTEXT:
884 * spin_lock_irq(gcwq->lock).
886 * RETURNS:
887 * Pointer to inserstion position.
889 static inline struct list_head *gcwq_determine_ins_pos(struct global_cwq *gcwq,
890 struct cpu_workqueue_struct *cwq)
892 struct work_struct *twork;
894 if (likely(!(cwq->wq->flags & WQ_HIGHPRI)))
895 return &gcwq->worklist;
897 list_for_each_entry(twork, &gcwq->worklist, entry) {
898 struct cpu_workqueue_struct *tcwq = get_work_cwq(twork);
900 if (!(tcwq->wq->flags & WQ_HIGHPRI))
901 break;
904 gcwq->flags |= GCWQ_HIGHPRI_PENDING;
905 return &twork->entry;
909 * insert_work - insert a work into gcwq
910 * @cwq: cwq @work belongs to
911 * @work: work to insert
912 * @head: insertion point
913 * @extra_flags: extra WORK_STRUCT_* flags to set
915 * Insert @work which belongs to @cwq into @gcwq after @head.
916 * @extra_flags is or'd to work_struct flags.
918 * CONTEXT:
919 * spin_lock_irq(gcwq->lock).
921 static void insert_work(struct cpu_workqueue_struct *cwq,
922 struct work_struct *work, struct list_head *head,
923 unsigned int extra_flags)
925 struct global_cwq *gcwq = cwq->gcwq;
927 /* we own @work, set data and link */
928 set_work_cwq(work, cwq, extra_flags);
931 * Ensure that we get the right work->data if we see the
932 * result of list_add() below, see try_to_grab_pending().
934 smp_wmb();
936 list_add_tail(&work->entry, head);
939 * Ensure either worker_sched_deactivated() sees the above
940 * list_add_tail() or we see zero nr_running to avoid workers
941 * lying around lazily while there are works to be processed.
943 smp_mb();
945 if (__need_more_worker(gcwq))
946 wake_up_worker(gcwq);
950 * Test whether @work is being queued from another work executing on the
951 * same workqueue. This is rather expensive and should only be used from
952 * cold paths.
954 static bool is_chained_work(struct workqueue_struct *wq)
956 unsigned long flags;
957 unsigned int cpu;
959 for_each_gcwq_cpu(cpu) {
960 struct global_cwq *gcwq = get_gcwq(cpu);
961 struct worker *worker;
962 struct hlist_node *pos;
963 int i;
965 spin_lock_irqsave(&gcwq->lock, flags);
966 for_each_busy_worker(worker, i, pos, gcwq) {
967 if (worker->task != current)
968 continue;
969 spin_unlock_irqrestore(&gcwq->lock, flags);
971 * I'm @worker, no locking necessary. See if @work
972 * is headed to the same workqueue.
974 return worker->current_cwq->wq == wq;
976 spin_unlock_irqrestore(&gcwq->lock, flags);
978 return false;
981 static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
982 struct work_struct *work)
984 struct global_cwq *gcwq;
985 struct cpu_workqueue_struct *cwq;
986 struct list_head *worklist;
987 unsigned int work_flags;
988 unsigned long flags;
990 debug_work_activate(work);
992 /* if dying, only works from the same workqueue are allowed */
993 if (unlikely(wq->flags & WQ_DYING) &&
994 WARN_ON_ONCE(!is_chained_work(wq)))
995 return;
997 /* determine gcwq to use */
998 if (!(wq->flags & WQ_UNBOUND)) {
999 struct global_cwq *last_gcwq;
1001 if (unlikely(cpu == WORK_CPU_UNBOUND))
1002 cpu = raw_smp_processor_id();
1005 * It's multi cpu. If @wq is non-reentrant and @work
1006 * was previously on a different cpu, it might still
1007 * be running there, in which case the work needs to
1008 * be queued on that cpu to guarantee non-reentrance.
1010 gcwq = get_gcwq(cpu);
1011 if (wq->flags & WQ_NON_REENTRANT &&
1012 (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {
1013 struct worker *worker;
1015 spin_lock_irqsave(&last_gcwq->lock, flags);
1017 worker = find_worker_executing_work(last_gcwq, work);
1019 if (worker && worker->current_cwq->wq == wq)
1020 gcwq = last_gcwq;
1021 else {
1022 /* meh... not running there, queue here */
1023 spin_unlock_irqrestore(&last_gcwq->lock, flags);
1024 spin_lock_irqsave(&gcwq->lock, flags);
1026 } else
1027 spin_lock_irqsave(&gcwq->lock, flags);
1028 } else {
1029 gcwq = get_gcwq(WORK_CPU_UNBOUND);
1030 spin_lock_irqsave(&gcwq->lock, flags);
1033 /* gcwq determined, get cwq and queue */
1034 cwq = get_cwq(gcwq->cpu, wq);
1035 trace_workqueue_queue_work(cpu, cwq, work);
1037 BUG_ON(!list_empty(&work->entry));
1039 cwq->nr_in_flight[cwq->work_color]++;
1040 work_flags = work_color_to_flags(cwq->work_color);
1042 if (likely(cwq->nr_active < cwq->max_active)) {
1043 trace_workqueue_activate_work(work);
1044 cwq->nr_active++;
1045 worklist = gcwq_determine_ins_pos(gcwq, cwq);
1046 } else {
1047 work_flags |= WORK_STRUCT_DELAYED;
1048 worklist = &cwq->delayed_works;
1051 insert_work(cwq, work, worklist, work_flags);
1053 spin_unlock_irqrestore(&gcwq->lock, flags);
1057 * queue_work - queue work on a workqueue
1058 * @wq: workqueue to use
1059 * @work: work to queue
1061 * Returns 0 if @work was already on a queue, non-zero otherwise.
1063 * We queue the work to the CPU on which it was submitted, but if the CPU dies
1064 * it can be processed by another CPU.
1066 int queue_work(struct workqueue_struct *wq, struct work_struct *work)
1068 int ret;
1070 ret = queue_work_on(get_cpu(), wq, work);
1071 put_cpu();
1073 return ret;
1075 EXPORT_SYMBOL_GPL(queue_work);
1078 * queue_work_on - queue work on specific cpu
1079 * @cpu: CPU number to execute work on
1080 * @wq: workqueue to use
1081 * @work: work to queue
1083 * Returns 0 if @work was already on a queue, non-zero otherwise.
1085 * We queue the work to a specific CPU, the caller must ensure it
1086 * can't go away.
1089 queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
1091 int ret = 0;
1093 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1094 __queue_work(cpu, wq, work);
1095 ret = 1;
1097 return ret;
1099 EXPORT_SYMBOL_GPL(queue_work_on);
1101 static void delayed_work_timer_fn(unsigned long __data)
1103 struct delayed_work *dwork = (struct delayed_work *)__data;
1104 struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work);
1106 __queue_work(smp_processor_id(), cwq->wq, &dwork->work);
1110 * queue_delayed_work - queue work on a workqueue after delay
1111 * @wq: workqueue to use
1112 * @dwork: delayable work to queue
1113 * @delay: number of jiffies to wait before queueing
1115 * Returns 0 if @work was already on a queue, non-zero otherwise.
1117 int queue_delayed_work(struct workqueue_struct *wq,
1118 struct delayed_work *dwork, unsigned long delay)
1120 if (delay == 0)
1121 return queue_work(wq, &dwork->work);
1123 return queue_delayed_work_on(-1, wq, dwork, delay);
1125 EXPORT_SYMBOL_GPL(queue_delayed_work);
1128 * queue_delayed_work_on - queue work on specific CPU after delay
1129 * @cpu: CPU number to execute work on
1130 * @wq: workqueue to use
1131 * @dwork: work to queue
1132 * @delay: number of jiffies to wait before queueing
1134 * Returns 0 if @work was already on a queue, non-zero otherwise.
1136 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
1137 struct delayed_work *dwork, unsigned long delay)
1139 int ret = 0;
1140 struct timer_list *timer = &dwork->timer;
1141 struct work_struct *work = &dwork->work;
1143 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) {
1144 unsigned int lcpu;
1146 BUG_ON(timer_pending(timer));
1147 BUG_ON(!list_empty(&work->entry));
1149 timer_stats_timer_set_start_info(&dwork->timer);
1152 * This stores cwq for the moment, for the timer_fn.
1153 * Note that the work's gcwq is preserved to allow
1154 * reentrance detection for delayed works.
1156 if (!(wq->flags & WQ_UNBOUND)) {
1157 struct global_cwq *gcwq = get_work_gcwq(work);
1159 if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND)
1160 lcpu = gcwq->cpu;
1161 else
1162 lcpu = raw_smp_processor_id();
1163 } else
1164 lcpu = WORK_CPU_UNBOUND;
1166 set_work_cwq(work, get_cwq(lcpu, wq), 0);
1168 timer->expires = jiffies + delay;
1169 timer->data = (unsigned long)dwork;
1170 timer->function = delayed_work_timer_fn;
1172 if (unlikely(cpu >= 0))
1173 add_timer_on(timer, cpu);
1174 else
1175 add_timer(timer);
1176 ret = 1;
1178 return ret;
1180 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
1183 * worker_enter_idle - enter idle state
1184 * @worker: worker which is entering idle state
1186 * @worker is entering idle state. Update stats and idle timer if
1187 * necessary.
1189 * LOCKING:
1190 * spin_lock_irq(gcwq->lock).
1192 static void worker_enter_idle(struct worker *worker)
1194 struct global_cwq *gcwq = worker->gcwq;
1196 BUG_ON(worker->flags & WORKER_IDLE);
1197 BUG_ON(!list_empty(&worker->entry) &&
1198 (worker->hentry.next || worker->hentry.pprev));
1200 /* can't use worker_set_flags(), also called from start_worker() */
1201 worker->flags |= WORKER_IDLE;
1202 gcwq->nr_idle++;
1203 worker->last_active = jiffies;
1205 /* idle_list is LIFO */
1206 list_add(&worker->entry, &gcwq->idle_list);
1208 if (likely(!(worker->flags & WORKER_ROGUE))) {
1209 if (too_many_workers(gcwq) && !timer_pending(&gcwq->idle_timer))
1210 mod_timer(&gcwq->idle_timer,
1211 jiffies + IDLE_WORKER_TIMEOUT);
1212 } else
1213 wake_up_all(&gcwq->trustee_wait);
1215 /* sanity check nr_running */
1216 WARN_ON_ONCE(gcwq->nr_workers == gcwq->nr_idle &&
1217 atomic_read(get_gcwq_nr_running(gcwq->cpu)));
1221 * worker_leave_idle - leave idle state
1222 * @worker: worker which is leaving idle state
1224 * @worker is leaving idle state. Update stats.
1226 * LOCKING:
1227 * spin_lock_irq(gcwq->lock).
1229 static void worker_leave_idle(struct worker *worker)
1231 struct global_cwq *gcwq = worker->gcwq;
1233 BUG_ON(!(worker->flags & WORKER_IDLE));
1234 worker_clr_flags(worker, WORKER_IDLE);
1235 gcwq->nr_idle--;
1236 list_del_init(&worker->entry);
1240 * worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq
1241 * @worker: self
1243 * Works which are scheduled while the cpu is online must at least be
1244 * scheduled to a worker which is bound to the cpu so that if they are
1245 * flushed from cpu callbacks while cpu is going down, they are
1246 * guaranteed to execute on the cpu.
1248 * This function is to be used by rogue workers and rescuers to bind
1249 * themselves to the target cpu and may race with cpu going down or
1250 * coming online. kthread_bind() can't be used because it may put the
1251 * worker to already dead cpu and set_cpus_allowed_ptr() can't be used
1252 * verbatim as it's best effort and blocking and gcwq may be
1253 * [dis]associated in the meantime.
1255 * This function tries set_cpus_allowed() and locks gcwq and verifies
1256 * the binding against GCWQ_DISASSOCIATED which is set during
1257 * CPU_DYING and cleared during CPU_ONLINE, so if the worker enters
1258 * idle state or fetches works without dropping lock, it can guarantee
1259 * the scheduling requirement described in the first paragraph.
1261 * CONTEXT:
1262 * Might sleep. Called without any lock but returns with gcwq->lock
1263 * held.
1265 * RETURNS:
1266 * %true if the associated gcwq is online (@worker is successfully
1267 * bound), %false if offline.
1269 static bool worker_maybe_bind_and_lock(struct worker *worker)
1270 __acquires(&gcwq->lock)
1272 struct global_cwq *gcwq = worker->gcwq;
1273 struct task_struct *task = worker->task;
1275 while (true) {
1277 * The following call may fail, succeed or succeed
1278 * without actually migrating the task to the cpu if
1279 * it races with cpu hotunplug operation. Verify
1280 * against GCWQ_DISASSOCIATED.
1282 if (!(gcwq->flags & GCWQ_DISASSOCIATED))
1283 set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu));
1285 spin_lock_irq(&gcwq->lock);
1286 if (gcwq->flags & GCWQ_DISASSOCIATED)
1287 return false;
1288 if (task_cpu(task) == gcwq->cpu &&
1289 cpumask_equal(&current->cpus_allowed,
1290 get_cpu_mask(gcwq->cpu)))
1291 return true;
1292 spin_unlock_irq(&gcwq->lock);
1295 * We've raced with CPU hot[un]plug. Give it a breather
1296 * and retry migration. cond_resched() is required here;
1297 * otherwise, we might deadlock against cpu_stop trying to
1298 * bring down the CPU on non-preemptive kernel.
1300 cpu_relax();
1301 cond_resched();
1306 * Function for worker->rebind_work used to rebind rogue busy workers
1307 * to the associated cpu which is coming back online. This is
1308 * scheduled by cpu up but can race with other cpu hotplug operations
1309 * and may be executed twice without intervening cpu down.
1311 static void worker_rebind_fn(struct work_struct *work)
1313 struct worker *worker = container_of(work, struct worker, rebind_work);
1314 struct global_cwq *gcwq = worker->gcwq;
1316 if (worker_maybe_bind_and_lock(worker))
1317 worker_clr_flags(worker, WORKER_REBIND);
1319 spin_unlock_irq(&gcwq->lock);
1322 static struct worker *alloc_worker(void)
1324 struct worker *worker;
1326 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
1327 if (worker) {
1328 INIT_LIST_HEAD(&worker->entry);
1329 INIT_LIST_HEAD(&worker->scheduled);
1330 INIT_WORK(&worker->rebind_work, worker_rebind_fn);
1331 /* on creation a worker is in !idle && prep state */
1332 worker->flags = WORKER_PREP;
1334 return worker;
1338 * create_worker - create a new workqueue worker
1339 * @gcwq: gcwq the new worker will belong to
1340 * @bind: whether to set affinity to @cpu or not
1342 * Create a new worker which is bound to @gcwq. The returned worker
1343 * can be started by calling start_worker() or destroyed using
1344 * destroy_worker().
1346 * CONTEXT:
1347 * Might sleep. Does GFP_KERNEL allocations.
1349 * RETURNS:
1350 * Pointer to the newly created worker.
1352 static struct worker *create_worker(struct global_cwq *gcwq, bool bind)
1354 bool on_unbound_cpu = gcwq->cpu == WORK_CPU_UNBOUND;
1355 struct worker *worker = NULL;
1356 int id = -1;
1358 spin_lock_irq(&gcwq->lock);
1359 while (ida_get_new(&gcwq->worker_ida, &id)) {
1360 spin_unlock_irq(&gcwq->lock);
1361 if (!ida_pre_get(&gcwq->worker_ida, GFP_KERNEL))
1362 goto fail;
1363 spin_lock_irq(&gcwq->lock);
1365 spin_unlock_irq(&gcwq->lock);
1367 worker = alloc_worker();
1368 if (!worker)
1369 goto fail;
1371 worker->gcwq = gcwq;
1372 worker->id = id;
1374 if (!on_unbound_cpu)
1375 worker->task = kthread_create_on_node(worker_thread,
1376 worker,
1377 cpu_to_node(gcwq->cpu),
1378 "kworker/%u:%d", gcwq->cpu, id);
1379 else
1380 worker->task = kthread_create(worker_thread, worker,
1381 "kworker/u:%d", id);
1382 if (IS_ERR(worker->task))
1383 goto fail;
1386 * A rogue worker will become a regular one if CPU comes
1387 * online later on. Make sure every worker has
1388 * PF_THREAD_BOUND set.
1390 if (bind && !on_unbound_cpu)
1391 kthread_bind(worker->task, gcwq->cpu);
1392 else {
1393 worker->task->flags |= PF_THREAD_BOUND;
1394 if (on_unbound_cpu)
1395 worker->flags |= WORKER_UNBOUND;
1398 return worker;
1399 fail:
1400 if (id >= 0) {
1401 spin_lock_irq(&gcwq->lock);
1402 ida_remove(&gcwq->worker_ida, id);
1403 spin_unlock_irq(&gcwq->lock);
1405 kfree(worker);
1406 return NULL;
1410 * start_worker - start a newly created worker
1411 * @worker: worker to start
1413 * Make the gcwq aware of @worker and start it.
1415 * CONTEXT:
1416 * spin_lock_irq(gcwq->lock).
1418 static void start_worker(struct worker *worker)
1420 worker->flags |= WORKER_STARTED;
1421 worker->gcwq->nr_workers++;
1422 worker_enter_idle(worker);
1423 wake_up_process(worker->task);
1427 * destroy_worker - destroy a workqueue worker
1428 * @worker: worker to be destroyed
1430 * Destroy @worker and adjust @gcwq stats accordingly.
1432 * CONTEXT:
1433 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1435 static void destroy_worker(struct worker *worker)
1437 struct global_cwq *gcwq = worker->gcwq;
1438 int id = worker->id;
1440 /* sanity check frenzy */
1441 BUG_ON(worker->current_work);
1442 BUG_ON(!list_empty(&worker->scheduled));
1444 if (worker->flags & WORKER_STARTED)
1445 gcwq->nr_workers--;
1446 if (worker->flags & WORKER_IDLE)
1447 gcwq->nr_idle--;
1449 list_del_init(&worker->entry);
1450 worker->flags |= WORKER_DIE;
1452 spin_unlock_irq(&gcwq->lock);
1454 kthread_stop(worker->task);
1455 kfree(worker);
1457 spin_lock_irq(&gcwq->lock);
1458 ida_remove(&gcwq->worker_ida, id);
1461 static void idle_worker_timeout(unsigned long __gcwq)
1463 struct global_cwq *gcwq = (void *)__gcwq;
1465 spin_lock_irq(&gcwq->lock);
1467 if (too_many_workers(gcwq)) {
1468 struct worker *worker;
1469 unsigned long expires;
1471 /* idle_list is kept in LIFO order, check the last one */
1472 worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1473 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1475 if (time_before(jiffies, expires))
1476 mod_timer(&gcwq->idle_timer, expires);
1477 else {
1478 /* it's been idle for too long, wake up manager */
1479 gcwq->flags |= GCWQ_MANAGE_WORKERS;
1480 wake_up_worker(gcwq);
1484 spin_unlock_irq(&gcwq->lock);
1487 static bool send_mayday(struct work_struct *work)
1489 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1490 struct workqueue_struct *wq = cwq->wq;
1491 unsigned int cpu;
1493 if (!(wq->flags & WQ_RESCUER))
1494 return false;
1496 /* mayday mayday mayday */
1497 cpu = cwq->gcwq->cpu;
1498 /* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */
1499 if (cpu == WORK_CPU_UNBOUND)
1500 cpu = 0;
1501 if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask))
1502 wake_up_process(wq->rescuer->task);
1503 return true;
1506 static void gcwq_mayday_timeout(unsigned long __gcwq)
1508 struct global_cwq *gcwq = (void *)__gcwq;
1509 struct work_struct *work;
1511 spin_lock_irq(&gcwq->lock);
1513 if (need_to_create_worker(gcwq)) {
1515 * We've been trying to create a new worker but
1516 * haven't been successful. We might be hitting an
1517 * allocation deadlock. Send distress signals to
1518 * rescuers.
1520 list_for_each_entry(work, &gcwq->worklist, entry)
1521 send_mayday(work);
1524 spin_unlock_irq(&gcwq->lock);
1526 mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INTERVAL);
1530 * maybe_create_worker - create a new worker if necessary
1531 * @gcwq: gcwq to create a new worker for
1533 * Create a new worker for @gcwq if necessary. @gcwq is guaranteed to
1534 * have at least one idle worker on return from this function. If
1535 * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is
1536 * sent to all rescuers with works scheduled on @gcwq to resolve
1537 * possible allocation deadlock.
1539 * On return, need_to_create_worker() is guaranteed to be false and
1540 * may_start_working() true.
1542 * LOCKING:
1543 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1544 * multiple times. Does GFP_KERNEL allocations. Called only from
1545 * manager.
1547 * RETURNS:
1548 * false if no action was taken and gcwq->lock stayed locked, true
1549 * otherwise.
1551 static bool maybe_create_worker(struct global_cwq *gcwq)
1552 __releases(&gcwq->lock)
1553 __acquires(&gcwq->lock)
1555 if (!need_to_create_worker(gcwq))
1556 return false;
1557 restart:
1558 spin_unlock_irq(&gcwq->lock);
1560 /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */
1561 mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT);
1563 while (true) {
1564 struct worker *worker;
1566 worker = create_worker(gcwq, true);
1567 if (worker) {
1568 del_timer_sync(&gcwq->mayday_timer);
1569 spin_lock_irq(&gcwq->lock);
1570 start_worker(worker);
1571 BUG_ON(need_to_create_worker(gcwq));
1572 return true;
1575 if (!need_to_create_worker(gcwq))
1576 break;
1578 __set_current_state(TASK_INTERRUPTIBLE);
1579 schedule_timeout(CREATE_COOLDOWN);
1581 if (!need_to_create_worker(gcwq))
1582 break;
1585 del_timer_sync(&gcwq->mayday_timer);
1586 spin_lock_irq(&gcwq->lock);
1587 if (need_to_create_worker(gcwq))
1588 goto restart;
1589 return true;
1593 * maybe_destroy_worker - destroy workers which have been idle for a while
1594 * @gcwq: gcwq to destroy workers for
1596 * Destroy @gcwq workers which have been idle for longer than
1597 * IDLE_WORKER_TIMEOUT.
1599 * LOCKING:
1600 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1601 * multiple times. Called only from manager.
1603 * RETURNS:
1604 * false if no action was taken and gcwq->lock stayed locked, true
1605 * otherwise.
1607 static bool maybe_destroy_workers(struct global_cwq *gcwq)
1609 bool ret = false;
1611 while (too_many_workers(gcwq)) {
1612 struct worker *worker;
1613 unsigned long expires;
1615 worker = list_entry(gcwq->idle_list.prev, struct worker, entry);
1616 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
1618 if (time_before(jiffies, expires)) {
1619 mod_timer(&gcwq->idle_timer, expires);
1620 break;
1623 destroy_worker(worker);
1624 ret = true;
1627 return ret;
1631 * manage_workers - manage worker pool
1632 * @worker: self
1634 * Assume the manager role and manage gcwq worker pool @worker belongs
1635 * to. At any given time, there can be only zero or one manager per
1636 * gcwq. The exclusion is handled automatically by this function.
1638 * The caller can safely start processing works on false return. On
1639 * true return, it's guaranteed that need_to_create_worker() is false
1640 * and may_start_working() is true.
1642 * CONTEXT:
1643 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1644 * multiple times. Does GFP_KERNEL allocations.
1646 * RETURNS:
1647 * false if no action was taken and gcwq->lock stayed locked, true if
1648 * some action was taken.
1650 static bool manage_workers(struct worker *worker)
1652 struct global_cwq *gcwq = worker->gcwq;
1653 bool ret = false;
1655 if (gcwq->flags & GCWQ_MANAGING_WORKERS)
1656 return ret;
1658 gcwq->flags &= ~GCWQ_MANAGE_WORKERS;
1659 gcwq->flags |= GCWQ_MANAGING_WORKERS;
1662 * Destroy and then create so that may_start_working() is true
1663 * on return.
1665 ret |= maybe_destroy_workers(gcwq);
1666 ret |= maybe_create_worker(gcwq);
1668 gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
1671 * The trustee might be waiting to take over the manager
1672 * position, tell it we're done.
1674 if (unlikely(gcwq->trustee))
1675 wake_up_all(&gcwq->trustee_wait);
1677 return ret;
1681 * move_linked_works - move linked works to a list
1682 * @work: start of series of works to be scheduled
1683 * @head: target list to append @work to
1684 * @nextp: out paramter for nested worklist walking
1686 * Schedule linked works starting from @work to @head. Work series to
1687 * be scheduled starts at @work and includes any consecutive work with
1688 * WORK_STRUCT_LINKED set in its predecessor.
1690 * If @nextp is not NULL, it's updated to point to the next work of
1691 * the last scheduled work. This allows move_linked_works() to be
1692 * nested inside outer list_for_each_entry_safe().
1694 * CONTEXT:
1695 * spin_lock_irq(gcwq->lock).
1697 static void move_linked_works(struct work_struct *work, struct list_head *head,
1698 struct work_struct **nextp)
1700 struct work_struct *n;
1703 * Linked worklist will always end before the end of the list,
1704 * use NULL for list head.
1706 list_for_each_entry_safe_from(work, n, NULL, entry) {
1707 list_move_tail(&work->entry, head);
1708 if (!(*work_data_bits(work) & WORK_STRUCT_LINKED))
1709 break;
1713 * If we're already inside safe list traversal and have moved
1714 * multiple works to the scheduled queue, the next position
1715 * needs to be updated.
1717 if (nextp)
1718 *nextp = n;
1721 static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq)
1723 struct work_struct *work = list_first_entry(&cwq->delayed_works,
1724 struct work_struct, entry);
1725 struct list_head *pos = gcwq_determine_ins_pos(cwq->gcwq, cwq);
1727 trace_workqueue_activate_work(work);
1728 move_linked_works(work, pos, NULL);
1729 __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work));
1730 cwq->nr_active++;
1734 * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight
1735 * @cwq: cwq of interest
1736 * @color: color of work which left the queue
1737 * @delayed: for a delayed work
1739 * A work either has completed or is removed from pending queue,
1740 * decrement nr_in_flight of its cwq and handle workqueue flushing.
1742 * CONTEXT:
1743 * spin_lock_irq(gcwq->lock).
1745 static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color,
1746 bool delayed)
1748 /* ignore uncolored works */
1749 if (color == WORK_NO_COLOR)
1750 return;
1752 cwq->nr_in_flight[color]--;
1754 if (!delayed) {
1755 cwq->nr_active--;
1756 if (!list_empty(&cwq->delayed_works)) {
1757 /* one down, submit a delayed one */
1758 if (cwq->nr_active < cwq->max_active)
1759 cwq_activate_first_delayed(cwq);
1763 /* is flush in progress and are we at the flushing tip? */
1764 if (likely(cwq->flush_color != color))
1765 return;
1767 /* are there still in-flight works? */
1768 if (cwq->nr_in_flight[color])
1769 return;
1771 /* this cwq is done, clear flush_color */
1772 cwq->flush_color = -1;
1775 * If this was the last cwq, wake up the first flusher. It
1776 * will handle the rest.
1778 if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush))
1779 complete(&cwq->wq->first_flusher->done);
1783 * process_one_work - process single work
1784 * @worker: self
1785 * @work: work to process
1787 * Process @work. This function contains all the logics necessary to
1788 * process a single work including synchronization against and
1789 * interaction with other workers on the same cpu, queueing and
1790 * flushing. As long as context requirement is met, any worker can
1791 * call this function to process a work.
1793 * CONTEXT:
1794 * spin_lock_irq(gcwq->lock) which is released and regrabbed.
1796 static void process_one_work(struct worker *worker, struct work_struct *work)
1797 __releases(&gcwq->lock)
1798 __acquires(&gcwq->lock)
1800 struct cpu_workqueue_struct *cwq = get_work_cwq(work);
1801 struct global_cwq *gcwq = cwq->gcwq;
1802 struct hlist_head *bwh = busy_worker_head(gcwq, work);
1803 bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE;
1804 work_func_t f = work->func;
1805 int work_color;
1806 struct worker *collision;
1807 #ifdef CONFIG_LOCKDEP
1809 * It is permissible to free the struct work_struct from
1810 * inside the function that is called from it, this we need to
1811 * take into account for lockdep too. To avoid bogus "held
1812 * lock freed" warnings as well as problems when looking into
1813 * work->lockdep_map, make a copy and use that here.
1815 struct lockdep_map lockdep_map = work->lockdep_map;
1816 #endif
1818 * A single work shouldn't be executed concurrently by
1819 * multiple workers on a single cpu. Check whether anyone is
1820 * already processing the work. If so, defer the work to the
1821 * currently executing one.
1823 collision = __find_worker_executing_work(gcwq, bwh, work);
1824 if (unlikely(collision)) {
1825 move_linked_works(work, &collision->scheduled, NULL);
1826 return;
1829 /* claim and process */
1830 debug_work_deactivate(work);
1831 hlist_add_head(&worker->hentry, bwh);
1832 worker->current_work = work;
1833 worker->current_cwq = cwq;
1834 work_color = get_work_color(work);
1836 /* record the current cpu number in the work data and dequeue */
1837 set_work_cpu(work, gcwq->cpu);
1838 list_del_init(&work->entry);
1841 * If HIGHPRI_PENDING, check the next work, and, if HIGHPRI,
1842 * wake up another worker; otherwise, clear HIGHPRI_PENDING.
1844 if (unlikely(gcwq->flags & GCWQ_HIGHPRI_PENDING)) {
1845 struct work_struct *nwork = list_first_entry(&gcwq->worklist,
1846 struct work_struct, entry);
1848 if (!list_empty(&gcwq->worklist) &&
1849 get_work_cwq(nwork)->wq->flags & WQ_HIGHPRI)
1850 wake_up_worker(gcwq);
1851 else
1852 gcwq->flags &= ~GCWQ_HIGHPRI_PENDING;
1856 * CPU intensive works don't participate in concurrency
1857 * management. They're the scheduler's responsibility.
1859 if (unlikely(cpu_intensive))
1860 worker_set_flags(worker, WORKER_CPU_INTENSIVE, true);
1862 spin_unlock_irq(&gcwq->lock);
1864 work_clear_pending(work);
1865 lock_map_acquire_read(&cwq->wq->lockdep_map);
1866 lock_map_acquire(&lockdep_map);
1867 trace_workqueue_execute_start(work);
1868 f(work);
1870 * While we must be careful to not use "work" after this, the trace
1871 * point will only record its address.
1873 trace_workqueue_execute_end(work);
1874 lock_map_release(&lockdep_map);
1875 lock_map_release(&cwq->wq->lockdep_map);
1877 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
1878 printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
1879 "%s/0x%08x/%d\n",
1880 current->comm, preempt_count(), task_pid_nr(current));
1881 printk(KERN_ERR " last function: ");
1882 print_symbol("%s\n", (unsigned long)f);
1883 debug_show_held_locks(current);
1884 dump_stack();
1887 spin_lock_irq(&gcwq->lock);
1889 /* clear cpu intensive status */
1890 if (unlikely(cpu_intensive))
1891 worker_clr_flags(worker, WORKER_CPU_INTENSIVE);
1893 /* we're done with it, release */
1894 hlist_del_init(&worker->hentry);
1895 worker->current_work = NULL;
1896 worker->current_cwq = NULL;
1897 cwq_dec_nr_in_flight(cwq, work_color, false);
1901 * process_scheduled_works - process scheduled works
1902 * @worker: self
1904 * Process all scheduled works. Please note that the scheduled list
1905 * may change while processing a work, so this function repeatedly
1906 * fetches a work from the top and executes it.
1908 * CONTEXT:
1909 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
1910 * multiple times.
1912 static void process_scheduled_works(struct worker *worker)
1914 while (!list_empty(&worker->scheduled)) {
1915 struct work_struct *work = list_first_entry(&worker->scheduled,
1916 struct work_struct, entry);
1917 process_one_work(worker, work);
1922 * worker_thread - the worker thread function
1923 * @__worker: self
1925 * The gcwq worker thread function. There's a single dynamic pool of
1926 * these per each cpu. These workers process all works regardless of
1927 * their specific target workqueue. The only exception is works which
1928 * belong to workqueues with a rescuer which will be explained in
1929 * rescuer_thread().
1931 static int worker_thread(void *__worker)
1933 struct worker *worker = __worker;
1934 struct global_cwq *gcwq = worker->gcwq;
1936 /* tell the scheduler that this is a workqueue worker */
1937 worker->task->flags |= PF_WQ_WORKER;
1938 woke_up:
1939 spin_lock_irq(&gcwq->lock);
1941 /* DIE can be set only while we're idle, checking here is enough */
1942 if (worker->flags & WORKER_DIE) {
1943 spin_unlock_irq(&gcwq->lock);
1944 worker->task->flags &= ~PF_WQ_WORKER;
1945 return 0;
1948 worker_leave_idle(worker);
1949 recheck:
1950 /* no more worker necessary? */
1951 if (!need_more_worker(gcwq))
1952 goto sleep;
1954 /* do we need to manage? */
1955 if (unlikely(!may_start_working(gcwq)) && manage_workers(worker))
1956 goto recheck;
1959 * ->scheduled list can only be filled while a worker is
1960 * preparing to process a work or actually processing it.
1961 * Make sure nobody diddled with it while I was sleeping.
1963 BUG_ON(!list_empty(&worker->scheduled));
1966 * When control reaches this point, we're guaranteed to have
1967 * at least one idle worker or that someone else has already
1968 * assumed the manager role.
1970 worker_clr_flags(worker, WORKER_PREP);
1972 do {
1973 struct work_struct *work =
1974 list_first_entry(&gcwq->worklist,
1975 struct work_struct, entry);
1977 if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) {
1978 /* optimization path, not strictly necessary */
1979 process_one_work(worker, work);
1980 if (unlikely(!list_empty(&worker->scheduled)))
1981 process_scheduled_works(worker);
1982 } else {
1983 move_linked_works(work, &worker->scheduled, NULL);
1984 process_scheduled_works(worker);
1986 } while (keep_working(gcwq));
1988 worker_set_flags(worker, WORKER_PREP, false);
1989 sleep:
1990 if (unlikely(need_to_manage_workers(gcwq)) && manage_workers(worker))
1991 goto recheck;
1994 * gcwq->lock is held and there's no work to process and no
1995 * need to manage, sleep. Workers are woken up only while
1996 * holding gcwq->lock or from local cpu, so setting the
1997 * current state before releasing gcwq->lock is enough to
1998 * prevent losing any event.
2000 worker_enter_idle(worker);
2001 __set_current_state(TASK_INTERRUPTIBLE);
2002 spin_unlock_irq(&gcwq->lock);
2003 schedule();
2004 goto woke_up;
2008 * rescuer_thread - the rescuer thread function
2009 * @__wq: the associated workqueue
2011 * Workqueue rescuer thread function. There's one rescuer for each
2012 * workqueue which has WQ_RESCUER set.
2014 * Regular work processing on a gcwq may block trying to create a new
2015 * worker which uses GFP_KERNEL allocation which has slight chance of
2016 * developing into deadlock if some works currently on the same queue
2017 * need to be processed to satisfy the GFP_KERNEL allocation. This is
2018 * the problem rescuer solves.
2020 * When such condition is possible, the gcwq summons rescuers of all
2021 * workqueues which have works queued on the gcwq and let them process
2022 * those works so that forward progress can be guaranteed.
2024 * This should happen rarely.
2026 static int rescuer_thread(void *__wq)
2028 struct workqueue_struct *wq = __wq;
2029 struct worker *rescuer = wq->rescuer;
2030 struct list_head *scheduled = &rescuer->scheduled;
2031 bool is_unbound = wq->flags & WQ_UNBOUND;
2032 unsigned int cpu;
2034 set_user_nice(current, RESCUER_NICE_LEVEL);
2035 repeat:
2036 set_current_state(TASK_INTERRUPTIBLE);
2038 if (kthread_should_stop())
2039 return 0;
2042 * See whether any cpu is asking for help. Unbounded
2043 * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND.
2045 for_each_mayday_cpu(cpu, wq->mayday_mask) {
2046 unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu;
2047 struct cpu_workqueue_struct *cwq = get_cwq(tcpu, wq);
2048 struct global_cwq *gcwq = cwq->gcwq;
2049 struct work_struct *work, *n;
2051 __set_current_state(TASK_RUNNING);
2052 mayday_clear_cpu(cpu, wq->mayday_mask);
2054 /* migrate to the target cpu if possible */
2055 rescuer->gcwq = gcwq;
2056 worker_maybe_bind_and_lock(rescuer);
2059 * Slurp in all works issued via this workqueue and
2060 * process'em.
2062 BUG_ON(!list_empty(&rescuer->scheduled));
2063 list_for_each_entry_safe(work, n, &gcwq->worklist, entry)
2064 if (get_work_cwq(work) == cwq)
2065 move_linked_works(work, scheduled, &n);
2067 process_scheduled_works(rescuer);
2070 * Leave this gcwq. If keep_working() is %true, notify a
2071 * regular worker; otherwise, we end up with 0 concurrency
2072 * and stalling the execution.
2074 if (keep_working(gcwq))
2075 wake_up_worker(gcwq);
2077 spin_unlock_irq(&gcwq->lock);
2080 schedule();
2081 goto repeat;
2084 struct wq_barrier {
2085 struct work_struct work;
2086 struct completion done;
2089 static void wq_barrier_func(struct work_struct *work)
2091 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
2092 complete(&barr->done);
2096 * insert_wq_barrier - insert a barrier work
2097 * @cwq: cwq to insert barrier into
2098 * @barr: wq_barrier to insert
2099 * @target: target work to attach @barr to
2100 * @worker: worker currently executing @target, NULL if @target is not executing
2102 * @barr is linked to @target such that @barr is completed only after
2103 * @target finishes execution. Please note that the ordering
2104 * guarantee is observed only with respect to @target and on the local
2105 * cpu.
2107 * Currently, a queued barrier can't be canceled. This is because
2108 * try_to_grab_pending() can't determine whether the work to be
2109 * grabbed is at the head of the queue and thus can't clear LINKED
2110 * flag of the previous work while there must be a valid next work
2111 * after a work with LINKED flag set.
2113 * Note that when @worker is non-NULL, @target may be modified
2114 * underneath us, so we can't reliably determine cwq from @target.
2116 * CONTEXT:
2117 * spin_lock_irq(gcwq->lock).
2119 static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
2120 struct wq_barrier *barr,
2121 struct work_struct *target, struct worker *worker)
2123 struct list_head *head;
2124 unsigned int linked = 0;
2127 * debugobject calls are safe here even with gcwq->lock locked
2128 * as we know for sure that this will not trigger any of the
2129 * checks and call back into the fixup functions where we
2130 * might deadlock.
2132 INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
2133 __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));
2134 init_completion(&barr->done);
2137 * If @target is currently being executed, schedule the
2138 * barrier to the worker; otherwise, put it after @target.
2140 if (worker)
2141 head = worker->scheduled.next;
2142 else {
2143 unsigned long *bits = work_data_bits(target);
2145 head = target->entry.next;
2146 /* there can already be other linked works, inherit and set */
2147 linked = *bits & WORK_STRUCT_LINKED;
2148 __set_bit(WORK_STRUCT_LINKED_BIT, bits);
2151 debug_work_activate(&barr->work);
2152 insert_work(cwq, &barr->work, head,
2153 work_color_to_flags(WORK_NO_COLOR) | linked);
2157 * flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing
2158 * @wq: workqueue being flushed
2159 * @flush_color: new flush color, < 0 for no-op
2160 * @work_color: new work color, < 0 for no-op
2162 * Prepare cwqs for workqueue flushing.
2164 * If @flush_color is non-negative, flush_color on all cwqs should be
2165 * -1. If no cwq has in-flight commands at the specified color, all
2166 * cwq->flush_color's stay at -1 and %false is returned. If any cwq
2167 * has in flight commands, its cwq->flush_color is set to
2168 * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq
2169 * wakeup logic is armed and %true is returned.
2171 * The caller should have initialized @wq->first_flusher prior to
2172 * calling this function with non-negative @flush_color. If
2173 * @flush_color is negative, no flush color update is done and %false
2174 * is returned.
2176 * If @work_color is non-negative, all cwqs should have the same
2177 * work_color which is previous to @work_color and all will be
2178 * advanced to @work_color.
2180 * CONTEXT:
2181 * mutex_lock(wq->flush_mutex).
2183 * RETURNS:
2184 * %true if @flush_color >= 0 and there's something to flush. %false
2185 * otherwise.
2187 static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq,
2188 int flush_color, int work_color)
2190 bool wait = false;
2191 unsigned int cpu;
2193 if (flush_color >= 0) {
2194 BUG_ON(atomic_read(&wq->nr_cwqs_to_flush));
2195 atomic_set(&wq->nr_cwqs_to_flush, 1);
2198 for_each_cwq_cpu(cpu, wq) {
2199 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2200 struct global_cwq *gcwq = cwq->gcwq;
2202 spin_lock_irq(&gcwq->lock);
2204 if (flush_color >= 0) {
2205 BUG_ON(cwq->flush_color != -1);
2207 if (cwq->nr_in_flight[flush_color]) {
2208 cwq->flush_color = flush_color;
2209 atomic_inc(&wq->nr_cwqs_to_flush);
2210 wait = true;
2214 if (work_color >= 0) {
2215 BUG_ON(work_color != work_next_color(cwq->work_color));
2216 cwq->work_color = work_color;
2219 spin_unlock_irq(&gcwq->lock);
2222 if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_to_flush))
2223 complete(&wq->first_flusher->done);
2225 return wait;
2229 * flush_workqueue - ensure that any scheduled work has run to completion.
2230 * @wq: workqueue to flush
2232 * Forces execution of the workqueue and blocks until its completion.
2233 * This is typically used in driver shutdown handlers.
2235 * We sleep until all works which were queued on entry have been handled,
2236 * but we are not livelocked by new incoming ones.
2238 void flush_workqueue(struct workqueue_struct *wq)
2240 struct wq_flusher this_flusher = {
2241 .list = LIST_HEAD_INIT(this_flusher.list),
2242 .flush_color = -1,
2243 .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
2245 int next_color;
2247 lock_map_acquire(&wq->lockdep_map);
2248 lock_map_release(&wq->lockdep_map);
2250 mutex_lock(&wq->flush_mutex);
2253 * Start-to-wait phase
2255 next_color = work_next_color(wq->work_color);
2257 if (next_color != wq->flush_color) {
2259 * Color space is not full. The current work_color
2260 * becomes our flush_color and work_color is advanced
2261 * by one.
2263 BUG_ON(!list_empty(&wq->flusher_overflow));
2264 this_flusher.flush_color = wq->work_color;
2265 wq->work_color = next_color;
2267 if (!wq->first_flusher) {
2268 /* no flush in progress, become the first flusher */
2269 BUG_ON(wq->flush_color != this_flusher.flush_color);
2271 wq->first_flusher = &this_flusher;
2273 if (!flush_workqueue_prep_cwqs(wq, wq->flush_color,
2274 wq->work_color)) {
2275 /* nothing to flush, done */
2276 wq->flush_color = next_color;
2277 wq->first_flusher = NULL;
2278 goto out_unlock;
2280 } else {
2281 /* wait in queue */
2282 BUG_ON(wq->flush_color == this_flusher.flush_color);
2283 list_add_tail(&this_flusher.list, &wq->flusher_queue);
2284 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2286 } else {
2288 * Oops, color space is full, wait on overflow queue.
2289 * The next flush completion will assign us
2290 * flush_color and transfer to flusher_queue.
2292 list_add_tail(&this_flusher.list, &wq->flusher_overflow);
2295 mutex_unlock(&wq->flush_mutex);
2297 wait_for_completion(&this_flusher.done);
2300 * Wake-up-and-cascade phase
2302 * First flushers are responsible for cascading flushes and
2303 * handling overflow. Non-first flushers can simply return.
2305 if (wq->first_flusher != &this_flusher)
2306 return;
2308 mutex_lock(&wq->flush_mutex);
2310 /* we might have raced, check again with mutex held */
2311 if (wq->first_flusher != &this_flusher)
2312 goto out_unlock;
2314 wq->first_flusher = NULL;
2316 BUG_ON(!list_empty(&this_flusher.list));
2317 BUG_ON(wq->flush_color != this_flusher.flush_color);
2319 while (true) {
2320 struct wq_flusher *next, *tmp;
2322 /* complete all the flushers sharing the current flush color */
2323 list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) {
2324 if (next->flush_color != wq->flush_color)
2325 break;
2326 list_del_init(&next->list);
2327 complete(&next->done);
2330 BUG_ON(!list_empty(&wq->flusher_overflow) &&
2331 wq->flush_color != work_next_color(wq->work_color));
2333 /* this flush_color is finished, advance by one */
2334 wq->flush_color = work_next_color(wq->flush_color);
2336 /* one color has been freed, handle overflow queue */
2337 if (!list_empty(&wq->flusher_overflow)) {
2339 * Assign the same color to all overflowed
2340 * flushers, advance work_color and append to
2341 * flusher_queue. This is the start-to-wait
2342 * phase for these overflowed flushers.
2344 list_for_each_entry(tmp, &wq->flusher_overflow, list)
2345 tmp->flush_color = wq->work_color;
2347 wq->work_color = work_next_color(wq->work_color);
2349 list_splice_tail_init(&wq->flusher_overflow,
2350 &wq->flusher_queue);
2351 flush_workqueue_prep_cwqs(wq, -1, wq->work_color);
2354 if (list_empty(&wq->flusher_queue)) {
2355 BUG_ON(wq->flush_color != wq->work_color);
2356 break;
2360 * Need to flush more colors. Make the next flusher
2361 * the new first flusher and arm cwqs.
2363 BUG_ON(wq->flush_color == wq->work_color);
2364 BUG_ON(wq->flush_color != next->flush_color);
2366 list_del_init(&next->list);
2367 wq->first_flusher = next;
2369 if (flush_workqueue_prep_cwqs(wq, wq->flush_color, -1))
2370 break;
2373 * Meh... this color is already done, clear first
2374 * flusher and repeat cascading.
2376 wq->first_flusher = NULL;
2379 out_unlock:
2380 mutex_unlock(&wq->flush_mutex);
2382 EXPORT_SYMBOL_GPL(flush_workqueue);
2384 static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,
2385 bool wait_executing)
2387 struct worker *worker = NULL;
2388 struct global_cwq *gcwq;
2389 struct cpu_workqueue_struct *cwq;
2391 might_sleep();
2392 gcwq = get_work_gcwq(work);
2393 if (!gcwq)
2394 return false;
2396 spin_lock_irq(&gcwq->lock);
2397 if (!list_empty(&work->entry)) {
2399 * See the comment near try_to_grab_pending()->smp_rmb().
2400 * If it was re-queued to a different gcwq under us, we
2401 * are not going to wait.
2403 smp_rmb();
2404 cwq = get_work_cwq(work);
2405 if (unlikely(!cwq || gcwq != cwq->gcwq))
2406 goto already_gone;
2407 } else if (wait_executing) {
2408 worker = find_worker_executing_work(gcwq, work);
2409 if (!worker)
2410 goto already_gone;
2411 cwq = worker->current_cwq;
2412 } else
2413 goto already_gone;
2415 insert_wq_barrier(cwq, barr, work, worker);
2416 spin_unlock_irq(&gcwq->lock);
2419 * If @max_active is 1 or rescuer is in use, flushing another work
2420 * item on the same workqueue may lead to deadlock. Make sure the
2421 * flusher is not running on the same workqueue by verifying write
2422 * access.
2424 if (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER)
2425 lock_map_acquire(&cwq->wq->lockdep_map);
2426 else
2427 lock_map_acquire_read(&cwq->wq->lockdep_map);
2428 lock_map_release(&cwq->wq->lockdep_map);
2430 return true;
2431 already_gone:
2432 spin_unlock_irq(&gcwq->lock);
2433 return false;
2437 * flush_work - wait for a work to finish executing the last queueing instance
2438 * @work: the work to flush
2440 * Wait until @work has finished execution. This function considers
2441 * only the last queueing instance of @work. If @work has been
2442 * enqueued across different CPUs on a non-reentrant workqueue or on
2443 * multiple workqueues, @work might still be executing on return on
2444 * some of the CPUs from earlier queueing.
2446 * If @work was queued only on a non-reentrant, ordered or unbound
2447 * workqueue, @work is guaranteed to be idle on return if it hasn't
2448 * been requeued since flush started.
2450 * RETURNS:
2451 * %true if flush_work() waited for the work to finish execution,
2452 * %false if it was already idle.
2454 bool flush_work(struct work_struct *work)
2456 struct wq_barrier barr;
2458 if (start_flush_work(work, &barr, true)) {
2459 wait_for_completion(&barr.done);
2460 destroy_work_on_stack(&barr.work);
2461 return true;
2462 } else
2463 return false;
2465 EXPORT_SYMBOL_GPL(flush_work);
2467 static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work)
2469 struct wq_barrier barr;
2470 struct worker *worker;
2472 spin_lock_irq(&gcwq->lock);
2474 worker = find_worker_executing_work(gcwq, work);
2475 if (unlikely(worker))
2476 insert_wq_barrier(worker->current_cwq, &barr, work, worker);
2478 spin_unlock_irq(&gcwq->lock);
2480 if (unlikely(worker)) {
2481 wait_for_completion(&barr.done);
2482 destroy_work_on_stack(&barr.work);
2483 return true;
2484 } else
2485 return false;
2488 static bool wait_on_work(struct work_struct *work)
2490 bool ret = false;
2491 int cpu;
2493 might_sleep();
2495 lock_map_acquire(&work->lockdep_map);
2496 lock_map_release(&work->lockdep_map);
2498 for_each_gcwq_cpu(cpu)
2499 ret |= wait_on_cpu_work(get_gcwq(cpu), work);
2500 return ret;
2504 * flush_work_sync - wait until a work has finished execution
2505 * @work: the work to flush
2507 * Wait until @work has finished execution. On return, it's
2508 * guaranteed that all queueing instances of @work which happened
2509 * before this function is called are finished. In other words, if
2510 * @work hasn't been requeued since this function was called, @work is
2511 * guaranteed to be idle on return.
2513 * RETURNS:
2514 * %true if flush_work_sync() waited for the work to finish execution,
2515 * %false if it was already idle.
2517 bool flush_work_sync(struct work_struct *work)
2519 struct wq_barrier barr;
2520 bool pending, waited;
2522 /* we'll wait for executions separately, queue barr only if pending */
2523 pending = start_flush_work(work, &barr, false);
2525 /* wait for executions to finish */
2526 waited = wait_on_work(work);
2528 /* wait for the pending one */
2529 if (pending) {
2530 wait_for_completion(&barr.done);
2531 destroy_work_on_stack(&barr.work);
2534 return pending || waited;
2536 EXPORT_SYMBOL_GPL(flush_work_sync);
2539 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
2540 * so this work can't be re-armed in any way.
2542 static int try_to_grab_pending(struct work_struct *work)
2544 struct global_cwq *gcwq;
2545 int ret = -1;
2547 if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work)))
2548 return 0;
2551 * The queueing is in progress, or it is already queued. Try to
2552 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
2554 gcwq = get_work_gcwq(work);
2555 if (!gcwq)
2556 return ret;
2558 spin_lock_irq(&gcwq->lock);
2559 if (!list_empty(&work->entry)) {
2561 * This work is queued, but perhaps we locked the wrong gcwq.
2562 * In that case we must see the new value after rmb(), see
2563 * insert_work()->wmb().
2565 smp_rmb();
2566 if (gcwq == get_work_gcwq(work)) {
2567 debug_work_deactivate(work);
2568 list_del_init(&work->entry);
2569 cwq_dec_nr_in_flight(get_work_cwq(work),
2570 get_work_color(work),
2571 *work_data_bits(work) & WORK_STRUCT_DELAYED);
2572 ret = 1;
2575 spin_unlock_irq(&gcwq->lock);
2577 return ret;
2580 static bool __cancel_work_timer(struct work_struct *work,
2581 struct timer_list* timer)
2583 int ret;
2585 do {
2586 ret = (timer && likely(del_timer(timer)));
2587 if (!ret)
2588 ret = try_to_grab_pending(work);
2589 wait_on_work(work);
2590 } while (unlikely(ret < 0));
2592 clear_work_data(work);
2593 return ret;
2597 * cancel_work_sync - cancel a work and wait for it to finish
2598 * @work: the work to cancel
2600 * Cancel @work and wait for its execution to finish. This function
2601 * can be used even if the work re-queues itself or migrates to
2602 * another workqueue. On return from this function, @work is
2603 * guaranteed to be not pending or executing on any CPU.
2605 * cancel_work_sync(&delayed_work->work) must not be used for
2606 * delayed_work's. Use cancel_delayed_work_sync() instead.
2608 * The caller must ensure that the workqueue on which @work was last
2609 * queued can't be destroyed before this function returns.
2611 * RETURNS:
2612 * %true if @work was pending, %false otherwise.
2614 bool cancel_work_sync(struct work_struct *work)
2616 return __cancel_work_timer(work, NULL);
2618 EXPORT_SYMBOL_GPL(cancel_work_sync);
2621 * flush_delayed_work - wait for a dwork to finish executing the last queueing
2622 * @dwork: the delayed work to flush
2624 * Delayed timer is cancelled and the pending work is queued for
2625 * immediate execution. Like flush_work(), this function only
2626 * considers the last queueing instance of @dwork.
2628 * RETURNS:
2629 * %true if flush_work() waited for the work to finish execution,
2630 * %false if it was already idle.
2632 bool flush_delayed_work(struct delayed_work *dwork)
2634 if (del_timer_sync(&dwork->timer))
2635 __queue_work(raw_smp_processor_id(),
2636 get_work_cwq(&dwork->work)->wq, &dwork->work);
2637 return flush_work(&dwork->work);
2639 EXPORT_SYMBOL(flush_delayed_work);
2642 * flush_delayed_work_sync - wait for a dwork to finish
2643 * @dwork: the delayed work to flush
2645 * Delayed timer is cancelled and the pending work is queued for
2646 * execution immediately. Other than timer handling, its behavior
2647 * is identical to flush_work_sync().
2649 * RETURNS:
2650 * %true if flush_work_sync() waited for the work to finish execution,
2651 * %false if it was already idle.
2653 bool flush_delayed_work_sync(struct delayed_work *dwork)
2655 if (del_timer_sync(&dwork->timer))
2656 __queue_work(raw_smp_processor_id(),
2657 get_work_cwq(&dwork->work)->wq, &dwork->work);
2658 return flush_work_sync(&dwork->work);
2660 EXPORT_SYMBOL(flush_delayed_work_sync);
2663 * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
2664 * @dwork: the delayed work cancel
2666 * This is cancel_work_sync() for delayed works.
2668 * RETURNS:
2669 * %true if @dwork was pending, %false otherwise.
2671 bool cancel_delayed_work_sync(struct delayed_work *dwork)
2673 return __cancel_work_timer(&dwork->work, &dwork->timer);
2675 EXPORT_SYMBOL(cancel_delayed_work_sync);
2678 * schedule_work - put work task in global workqueue
2679 * @work: job to be done
2681 * Returns zero if @work was already on the kernel-global workqueue and
2682 * non-zero otherwise.
2684 * This puts a job in the kernel-global workqueue if it was not already
2685 * queued and leaves it in the same position on the kernel-global
2686 * workqueue otherwise.
2688 int schedule_work(struct work_struct *work)
2690 return queue_work(system_wq, work);
2692 EXPORT_SYMBOL(schedule_work);
2695 * schedule_work_on - put work task on a specific cpu
2696 * @cpu: cpu to put the work task on
2697 * @work: job to be done
2699 * This puts a job on a specific cpu
2701 int schedule_work_on(int cpu, struct work_struct *work)
2703 return queue_work_on(cpu, system_wq, work);
2705 EXPORT_SYMBOL(schedule_work_on);
2708 * schedule_delayed_work - put work task in global workqueue after delay
2709 * @dwork: job to be done
2710 * @delay: number of jiffies to wait or 0 for immediate execution
2712 * After waiting for a given time this puts a job in the kernel-global
2713 * workqueue.
2715 int schedule_delayed_work(struct delayed_work *dwork,
2716 unsigned long delay)
2718 return queue_delayed_work(system_wq, dwork, delay);
2720 EXPORT_SYMBOL(schedule_delayed_work);
2723 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
2724 * @cpu: cpu to use
2725 * @dwork: job to be done
2726 * @delay: number of jiffies to wait
2728 * After waiting for a given time this puts a job in the kernel-global
2729 * workqueue on the specified CPU.
2731 int schedule_delayed_work_on(int cpu,
2732 struct delayed_work *dwork, unsigned long delay)
2734 return queue_delayed_work_on(cpu, system_wq, dwork, delay);
2736 EXPORT_SYMBOL(schedule_delayed_work_on);
2739 * schedule_on_each_cpu - execute a function synchronously on each online CPU
2740 * @func: the function to call
2742 * schedule_on_each_cpu() executes @func on each online CPU using the
2743 * system workqueue and blocks until all CPUs have completed.
2744 * schedule_on_each_cpu() is very slow.
2746 * RETURNS:
2747 * 0 on success, -errno on failure.
2749 int schedule_on_each_cpu(work_func_t func)
2751 int cpu;
2752 struct work_struct __percpu *works;
2754 works = alloc_percpu(struct work_struct);
2755 if (!works)
2756 return -ENOMEM;
2758 get_online_cpus();
2760 for_each_online_cpu(cpu) {
2761 struct work_struct *work = per_cpu_ptr(works, cpu);
2763 INIT_WORK(work, func);
2764 schedule_work_on(cpu, work);
2767 for_each_online_cpu(cpu)
2768 flush_work(per_cpu_ptr(works, cpu));
2770 put_online_cpus();
2771 free_percpu(works);
2772 return 0;
2776 * flush_scheduled_work - ensure that any scheduled work has run to completion.
2778 * Forces execution of the kernel-global workqueue and blocks until its
2779 * completion.
2781 * Think twice before calling this function! It's very easy to get into
2782 * trouble if you don't take great care. Either of the following situations
2783 * will lead to deadlock:
2785 * One of the work items currently on the workqueue needs to acquire
2786 * a lock held by your code or its caller.
2788 * Your code is running in the context of a work routine.
2790 * They will be detected by lockdep when they occur, but the first might not
2791 * occur very often. It depends on what work items are on the workqueue and
2792 * what locks they need, which you have no control over.
2794 * In most situations flushing the entire workqueue is overkill; you merely
2795 * need to know that a particular work item isn't queued and isn't running.
2796 * In such cases you should use cancel_delayed_work_sync() or
2797 * cancel_work_sync() instead.
2799 void flush_scheduled_work(void)
2801 flush_workqueue(system_wq);
2803 EXPORT_SYMBOL(flush_scheduled_work);
2806 * execute_in_process_context - reliably execute the routine with user context
2807 * @fn: the function to execute
2808 * @ew: guaranteed storage for the execute work structure (must
2809 * be available when the work executes)
2811 * Executes the function immediately if process context is available,
2812 * otherwise schedules the function for delayed execution.
2814 * Returns: 0 - function was executed
2815 * 1 - function was scheduled for execution
2817 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
2819 if (!in_interrupt()) {
2820 fn(&ew->work);
2821 return 0;
2824 INIT_WORK(&ew->work, fn);
2825 schedule_work(&ew->work);
2827 return 1;
2829 EXPORT_SYMBOL_GPL(execute_in_process_context);
2831 int keventd_up(void)
2833 return system_wq != NULL;
2836 static int alloc_cwqs(struct workqueue_struct *wq)
2839 * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS.
2840 * Make sure that the alignment isn't lower than that of
2841 * unsigned long long.
2843 const size_t size = sizeof(struct cpu_workqueue_struct);
2844 const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS,
2845 __alignof__(unsigned long long));
2846 #ifdef CONFIG_SMP
2847 bool percpu = !(wq->flags & WQ_UNBOUND);
2848 #else
2849 bool percpu = false;
2850 #endif
2852 if (percpu)
2853 wq->cpu_wq.pcpu = __alloc_percpu(size, align);
2854 else {
2855 void *ptr;
2858 * Allocate enough room to align cwq and put an extra
2859 * pointer at the end pointing back to the originally
2860 * allocated pointer which will be used for free.
2862 ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL);
2863 if (ptr) {
2864 wq->cpu_wq.single = PTR_ALIGN(ptr, align);
2865 *(void **)(wq->cpu_wq.single + 1) = ptr;
2869 /* just in case, make sure it's actually aligned */
2870 BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align));
2871 return wq->cpu_wq.v ? 0 : -ENOMEM;
2874 static void free_cwqs(struct workqueue_struct *wq)
2876 #ifdef CONFIG_SMP
2877 bool percpu = !(wq->flags & WQ_UNBOUND);
2878 #else
2879 bool percpu = false;
2880 #endif
2882 if (percpu)
2883 free_percpu(wq->cpu_wq.pcpu);
2884 else if (wq->cpu_wq.single) {
2885 /* the pointer to free is stored right after the cwq */
2886 kfree(*(void **)(wq->cpu_wq.single + 1));
2890 static int wq_clamp_max_active(int max_active, unsigned int flags,
2891 const char *name)
2893 int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE;
2895 if (max_active < 1 || max_active > lim)
2896 printk(KERN_WARNING "workqueue: max_active %d requested for %s "
2897 "is out of range, clamping between %d and %d\n",
2898 max_active, name, 1, lim);
2900 return clamp_val(max_active, 1, lim);
2903 struct workqueue_struct *__alloc_workqueue_key(const char *name,
2904 unsigned int flags,
2905 int max_active,
2906 struct lock_class_key *key,
2907 const char *lock_name)
2909 struct workqueue_struct *wq;
2910 unsigned int cpu;
2913 * Workqueues which may be used during memory reclaim should
2914 * have a rescuer to guarantee forward progress.
2916 if (flags & WQ_MEM_RECLAIM)
2917 flags |= WQ_RESCUER;
2920 * Unbound workqueues aren't concurrency managed and should be
2921 * dispatched to workers immediately.
2923 if (flags & WQ_UNBOUND)
2924 flags |= WQ_HIGHPRI;
2926 max_active = max_active ?: WQ_DFL_ACTIVE;
2927 max_active = wq_clamp_max_active(max_active, flags, name);
2929 wq = kzalloc(sizeof(*wq), GFP_KERNEL);
2930 if (!wq)
2931 goto err;
2933 wq->flags = flags;
2934 wq->saved_max_active = max_active;
2935 mutex_init(&wq->flush_mutex);
2936 atomic_set(&wq->nr_cwqs_to_flush, 0);
2937 INIT_LIST_HEAD(&wq->flusher_queue);
2938 INIT_LIST_HEAD(&wq->flusher_overflow);
2940 wq->name = name;
2941 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
2942 INIT_LIST_HEAD(&wq->list);
2944 if (alloc_cwqs(wq) < 0)
2945 goto err;
2947 for_each_cwq_cpu(cpu, wq) {
2948 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
2949 struct global_cwq *gcwq = get_gcwq(cpu);
2951 BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK);
2952 cwq->gcwq = gcwq;
2953 cwq->wq = wq;
2954 cwq->flush_color = -1;
2955 cwq->max_active = max_active;
2956 INIT_LIST_HEAD(&cwq->delayed_works);
2959 if (flags & WQ_RESCUER) {
2960 struct worker *rescuer;
2962 if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL))
2963 goto err;
2965 wq->rescuer = rescuer = alloc_worker();
2966 if (!rescuer)
2967 goto err;
2969 rescuer->task = kthread_create(rescuer_thread, wq, "%s", name);
2970 if (IS_ERR(rescuer->task))
2971 goto err;
2973 rescuer->task->flags |= PF_THREAD_BOUND;
2974 wake_up_process(rescuer->task);
2978 * workqueue_lock protects global freeze state and workqueues
2979 * list. Grab it, set max_active accordingly and add the new
2980 * workqueue to workqueues list.
2982 spin_lock(&workqueue_lock);
2984 if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
2985 for_each_cwq_cpu(cpu, wq)
2986 get_cwq(cpu, wq)->max_active = 0;
2988 list_add(&wq->list, &workqueues);
2990 spin_unlock(&workqueue_lock);
2992 return wq;
2993 err:
2994 if (wq) {
2995 free_cwqs(wq);
2996 free_mayday_mask(wq->mayday_mask);
2997 kfree(wq->rescuer);
2998 kfree(wq);
3000 return NULL;
3002 EXPORT_SYMBOL_GPL(__alloc_workqueue_key);
3005 * destroy_workqueue - safely terminate a workqueue
3006 * @wq: target workqueue
3008 * Safely destroy a workqueue. All work currently pending will be done first.
3010 void destroy_workqueue(struct workqueue_struct *wq)
3012 unsigned int flush_cnt = 0;
3013 unsigned int cpu;
3016 * Mark @wq dying and drain all pending works. Once WQ_DYING is
3017 * set, only chain queueing is allowed. IOW, only currently
3018 * pending or running work items on @wq can queue further work
3019 * items on it. @wq is flushed repeatedly until it becomes empty.
3020 * The number of flushing is detemined by the depth of chaining and
3021 * should be relatively short. Whine if it takes too long.
3023 wq->flags |= WQ_DYING;
3024 reflush:
3025 flush_workqueue(wq);
3027 for_each_cwq_cpu(cpu, wq) {
3028 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3030 if (!cwq->nr_active && list_empty(&cwq->delayed_works))
3031 continue;
3033 if (++flush_cnt == 10 ||
3034 (flush_cnt % 100 == 0 && flush_cnt <= 1000))
3035 printk(KERN_WARNING "workqueue %s: flush on "
3036 "destruction isn't complete after %u tries\n",
3037 wq->name, flush_cnt);
3038 goto reflush;
3042 * wq list is used to freeze wq, remove from list after
3043 * flushing is complete in case freeze races us.
3045 spin_lock(&workqueue_lock);
3046 list_del(&wq->list);
3047 spin_unlock(&workqueue_lock);
3049 /* sanity check */
3050 for_each_cwq_cpu(cpu, wq) {
3051 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3052 int i;
3054 for (i = 0; i < WORK_NR_COLORS; i++)
3055 BUG_ON(cwq->nr_in_flight[i]);
3056 BUG_ON(cwq->nr_active);
3057 BUG_ON(!list_empty(&cwq->delayed_works));
3060 if (wq->flags & WQ_RESCUER) {
3061 kthread_stop(wq->rescuer->task);
3062 free_mayday_mask(wq->mayday_mask);
3063 kfree(wq->rescuer);
3066 free_cwqs(wq);
3067 kfree(wq);
3069 EXPORT_SYMBOL_GPL(destroy_workqueue);
3072 * workqueue_set_max_active - adjust max_active of a workqueue
3073 * @wq: target workqueue
3074 * @max_active: new max_active value.
3076 * Set max_active of @wq to @max_active.
3078 * CONTEXT:
3079 * Don't call from IRQ context.
3081 void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
3083 unsigned int cpu;
3085 max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
3087 spin_lock(&workqueue_lock);
3089 wq->saved_max_active = max_active;
3091 for_each_cwq_cpu(cpu, wq) {
3092 struct global_cwq *gcwq = get_gcwq(cpu);
3094 spin_lock_irq(&gcwq->lock);
3096 if (!(wq->flags & WQ_FREEZABLE) ||
3097 !(gcwq->flags & GCWQ_FREEZING))
3098 get_cwq(gcwq->cpu, wq)->max_active = max_active;
3100 spin_unlock_irq(&gcwq->lock);
3103 spin_unlock(&workqueue_lock);
3105 EXPORT_SYMBOL_GPL(workqueue_set_max_active);
3108 * workqueue_congested - test whether a workqueue is congested
3109 * @cpu: CPU in question
3110 * @wq: target workqueue
3112 * Test whether @wq's cpu workqueue for @cpu is congested. There is
3113 * no synchronization around this function and the test result is
3114 * unreliable and only useful as advisory hints or for debugging.
3116 * RETURNS:
3117 * %true if congested, %false otherwise.
3119 bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq)
3121 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3123 return !list_empty(&cwq->delayed_works);
3125 EXPORT_SYMBOL_GPL(workqueue_congested);
3128 * work_cpu - return the last known associated cpu for @work
3129 * @work: the work of interest
3131 * RETURNS:
3132 * CPU number if @work was ever queued. WORK_CPU_NONE otherwise.
3134 unsigned int work_cpu(struct work_struct *work)
3136 struct global_cwq *gcwq = get_work_gcwq(work);
3138 return gcwq ? gcwq->cpu : WORK_CPU_NONE;
3140 EXPORT_SYMBOL_GPL(work_cpu);
3143 * work_busy - test whether a work is currently pending or running
3144 * @work: the work to be tested
3146 * Test whether @work is currently pending or running. There is no
3147 * synchronization around this function and the test result is
3148 * unreliable and only useful as advisory hints or for debugging.
3149 * Especially for reentrant wqs, the pending state might hide the
3150 * running state.
3152 * RETURNS:
3153 * OR'd bitmask of WORK_BUSY_* bits.
3155 unsigned int work_busy(struct work_struct *work)
3157 struct global_cwq *gcwq = get_work_gcwq(work);
3158 unsigned long flags;
3159 unsigned int ret = 0;
3161 if (!gcwq)
3162 return false;
3164 spin_lock_irqsave(&gcwq->lock, flags);
3166 if (work_pending(work))
3167 ret |= WORK_BUSY_PENDING;
3168 if (find_worker_executing_work(gcwq, work))
3169 ret |= WORK_BUSY_RUNNING;
3171 spin_unlock_irqrestore(&gcwq->lock, flags);
3173 return ret;
3175 EXPORT_SYMBOL_GPL(work_busy);
3178 * CPU hotplug.
3180 * There are two challenges in supporting CPU hotplug. Firstly, there
3181 * are a lot of assumptions on strong associations among work, cwq and
3182 * gcwq which make migrating pending and scheduled works very
3183 * difficult to implement without impacting hot paths. Secondly,
3184 * gcwqs serve mix of short, long and very long running works making
3185 * blocked draining impractical.
3187 * This is solved by allowing a gcwq to be detached from CPU, running
3188 * it with unbound (rogue) workers and allowing it to be reattached
3189 * later if the cpu comes back online. A separate thread is created
3190 * to govern a gcwq in such state and is called the trustee of the
3191 * gcwq.
3193 * Trustee states and their descriptions.
3195 * START Command state used on startup. On CPU_DOWN_PREPARE, a
3196 * new trustee is started with this state.
3198 * IN_CHARGE Once started, trustee will enter this state after
3199 * assuming the manager role and making all existing
3200 * workers rogue. DOWN_PREPARE waits for trustee to
3201 * enter this state. After reaching IN_CHARGE, trustee
3202 * tries to execute the pending worklist until it's empty
3203 * and the state is set to BUTCHER, or the state is set
3204 * to RELEASE.
3206 * BUTCHER Command state which is set by the cpu callback after
3207 * the cpu has went down. Once this state is set trustee
3208 * knows that there will be no new works on the worklist
3209 * and once the worklist is empty it can proceed to
3210 * killing idle workers.
3212 * RELEASE Command state which is set by the cpu callback if the
3213 * cpu down has been canceled or it has come online
3214 * again. After recognizing this state, trustee stops
3215 * trying to drain or butcher and clears ROGUE, rebinds
3216 * all remaining workers back to the cpu and releases
3217 * manager role.
3219 * DONE Trustee will enter this state after BUTCHER or RELEASE
3220 * is complete.
3222 * trustee CPU draining
3223 * took over down complete
3224 * START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE
3225 * | | ^
3226 * | CPU is back online v return workers |
3227 * ----------------> RELEASE --------------
3231 * trustee_wait_event_timeout - timed event wait for trustee
3232 * @cond: condition to wait for
3233 * @timeout: timeout in jiffies
3235 * wait_event_timeout() for trustee to use. Handles locking and
3236 * checks for RELEASE request.
3238 * CONTEXT:
3239 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3240 * multiple times. To be used by trustee.
3242 * RETURNS:
3243 * Positive indicating left time if @cond is satisfied, 0 if timed
3244 * out, -1 if canceled.
3246 #define trustee_wait_event_timeout(cond, timeout) ({ \
3247 long __ret = (timeout); \
3248 while (!((cond) || (gcwq->trustee_state == TRUSTEE_RELEASE)) && \
3249 __ret) { \
3250 spin_unlock_irq(&gcwq->lock); \
3251 __wait_event_timeout(gcwq->trustee_wait, (cond) || \
3252 (gcwq->trustee_state == TRUSTEE_RELEASE), \
3253 __ret); \
3254 spin_lock_irq(&gcwq->lock); \
3256 gcwq->trustee_state == TRUSTEE_RELEASE ? -1 : (__ret); \
3260 * trustee_wait_event - event wait for trustee
3261 * @cond: condition to wait for
3263 * wait_event() for trustee to use. Automatically handles locking and
3264 * checks for CANCEL request.
3266 * CONTEXT:
3267 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3268 * multiple times. To be used by trustee.
3270 * RETURNS:
3271 * 0 if @cond is satisfied, -1 if canceled.
3273 #define trustee_wait_event(cond) ({ \
3274 long __ret1; \
3275 __ret1 = trustee_wait_event_timeout(cond, MAX_SCHEDULE_TIMEOUT);\
3276 __ret1 < 0 ? -1 : 0; \
3279 static int __cpuinit trustee_thread(void *__gcwq)
3281 struct global_cwq *gcwq = __gcwq;
3282 struct worker *worker;
3283 struct work_struct *work;
3284 struct hlist_node *pos;
3285 long rc;
3286 int i;
3288 BUG_ON(gcwq->cpu != smp_processor_id());
3290 spin_lock_irq(&gcwq->lock);
3292 * Claim the manager position and make all workers rogue.
3293 * Trustee must be bound to the target cpu and can't be
3294 * cancelled.
3296 BUG_ON(gcwq->cpu != smp_processor_id());
3297 rc = trustee_wait_event(!(gcwq->flags & GCWQ_MANAGING_WORKERS));
3298 BUG_ON(rc < 0);
3300 gcwq->flags |= GCWQ_MANAGING_WORKERS;
3302 list_for_each_entry(worker, &gcwq->idle_list, entry)
3303 worker->flags |= WORKER_ROGUE;
3305 for_each_busy_worker(worker, i, pos, gcwq)
3306 worker->flags |= WORKER_ROGUE;
3309 * Call schedule() so that we cross rq->lock and thus can
3310 * guarantee sched callbacks see the rogue flag. This is
3311 * necessary as scheduler callbacks may be invoked from other
3312 * cpus.
3314 spin_unlock_irq(&gcwq->lock);
3315 schedule();
3316 spin_lock_irq(&gcwq->lock);
3319 * Sched callbacks are disabled now. Zap nr_running. After
3320 * this, nr_running stays zero and need_more_worker() and
3321 * keep_working() are always true as long as the worklist is
3322 * not empty.
3324 atomic_set(get_gcwq_nr_running(gcwq->cpu), 0);
3326 spin_unlock_irq(&gcwq->lock);
3327 del_timer_sync(&gcwq->idle_timer);
3328 spin_lock_irq(&gcwq->lock);
3331 * We're now in charge. Notify and proceed to drain. We need
3332 * to keep the gcwq running during the whole CPU down
3333 * procedure as other cpu hotunplug callbacks may need to
3334 * flush currently running tasks.
3336 gcwq->trustee_state = TRUSTEE_IN_CHARGE;
3337 wake_up_all(&gcwq->trustee_wait);
3340 * The original cpu is in the process of dying and may go away
3341 * anytime now. When that happens, we and all workers would
3342 * be migrated to other cpus. Try draining any left work. We
3343 * want to get it over with ASAP - spam rescuers, wake up as
3344 * many idlers as necessary and create new ones till the
3345 * worklist is empty. Note that if the gcwq is frozen, there
3346 * may be frozen works in freezable cwqs. Don't declare
3347 * completion while frozen.
3349 while (gcwq->nr_workers != gcwq->nr_idle ||
3350 gcwq->flags & GCWQ_FREEZING ||
3351 gcwq->trustee_state == TRUSTEE_IN_CHARGE) {
3352 int nr_works = 0;
3354 list_for_each_entry(work, &gcwq->worklist, entry) {
3355 send_mayday(work);
3356 nr_works++;
3359 list_for_each_entry(worker, &gcwq->idle_list, entry) {
3360 if (!nr_works--)
3361 break;
3362 wake_up_process(worker->task);
3365 if (need_to_create_worker(gcwq)) {
3366 spin_unlock_irq(&gcwq->lock);
3367 worker = create_worker(gcwq, false);
3368 spin_lock_irq(&gcwq->lock);
3369 if (worker) {
3370 worker->flags |= WORKER_ROGUE;
3371 start_worker(worker);
3375 /* give a breather */
3376 if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0)
3377 break;
3381 * Either all works have been scheduled and cpu is down, or
3382 * cpu down has already been canceled. Wait for and butcher
3383 * all workers till we're canceled.
3385 do {
3386 rc = trustee_wait_event(!list_empty(&gcwq->idle_list));
3387 while (!list_empty(&gcwq->idle_list))
3388 destroy_worker(list_first_entry(&gcwq->idle_list,
3389 struct worker, entry));
3390 } while (gcwq->nr_workers && rc >= 0);
3393 * At this point, either draining has completed and no worker
3394 * is left, or cpu down has been canceled or the cpu is being
3395 * brought back up. There shouldn't be any idle one left.
3396 * Tell the remaining busy ones to rebind once it finishes the
3397 * currently scheduled works by scheduling the rebind_work.
3399 WARN_ON(!list_empty(&gcwq->idle_list));
3401 for_each_busy_worker(worker, i, pos, gcwq) {
3402 struct work_struct *rebind_work = &worker->rebind_work;
3405 * Rebind_work may race with future cpu hotplug
3406 * operations. Use a separate flag to mark that
3407 * rebinding is scheduled.
3409 worker->flags |= WORKER_REBIND;
3410 worker->flags &= ~WORKER_ROGUE;
3412 /* queue rebind_work, wq doesn't matter, use the default one */
3413 if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
3414 work_data_bits(rebind_work)))
3415 continue;
3417 debug_work_activate(rebind_work);
3418 insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work,
3419 worker->scheduled.next,
3420 work_color_to_flags(WORK_NO_COLOR));
3423 /* relinquish manager role */
3424 gcwq->flags &= ~GCWQ_MANAGING_WORKERS;
3426 /* notify completion */
3427 gcwq->trustee = NULL;
3428 gcwq->trustee_state = TRUSTEE_DONE;
3429 wake_up_all(&gcwq->trustee_wait);
3430 spin_unlock_irq(&gcwq->lock);
3431 return 0;
3435 * wait_trustee_state - wait for trustee to enter the specified state
3436 * @gcwq: gcwq the trustee of interest belongs to
3437 * @state: target state to wait for
3439 * Wait for the trustee to reach @state. DONE is already matched.
3441 * CONTEXT:
3442 * spin_lock_irq(gcwq->lock) which may be released and regrabbed
3443 * multiple times. To be used by cpu_callback.
3445 static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state)
3446 __releases(&gcwq->lock)
3447 __acquires(&gcwq->lock)
3449 if (!(gcwq->trustee_state == state ||
3450 gcwq->trustee_state == TRUSTEE_DONE)) {
3451 spin_unlock_irq(&gcwq->lock);
3452 __wait_event(gcwq->trustee_wait,
3453 gcwq->trustee_state == state ||
3454 gcwq->trustee_state == TRUSTEE_DONE);
3455 spin_lock_irq(&gcwq->lock);
3459 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
3460 unsigned long action,
3461 void *hcpu)
3463 unsigned int cpu = (unsigned long)hcpu;
3464 struct global_cwq *gcwq = get_gcwq(cpu);
3465 struct task_struct *new_trustee = NULL;
3466 struct worker *uninitialized_var(new_worker);
3467 unsigned long flags;
3469 action &= ~CPU_TASKS_FROZEN;
3471 switch (action) {
3472 case CPU_DOWN_PREPARE:
3473 new_trustee = kthread_create(trustee_thread, gcwq,
3474 "workqueue_trustee/%d\n", cpu);
3475 if (IS_ERR(new_trustee))
3476 return notifier_from_errno(PTR_ERR(new_trustee));
3477 kthread_bind(new_trustee, cpu);
3478 /* fall through */
3479 case CPU_UP_PREPARE:
3480 BUG_ON(gcwq->first_idle);
3481 new_worker = create_worker(gcwq, false);
3482 if (!new_worker) {
3483 if (new_trustee)
3484 kthread_stop(new_trustee);
3485 return NOTIFY_BAD;
3489 /* some are called w/ irq disabled, don't disturb irq status */
3490 spin_lock_irqsave(&gcwq->lock, flags);
3492 switch (action) {
3493 case CPU_DOWN_PREPARE:
3494 /* initialize trustee and tell it to acquire the gcwq */
3495 BUG_ON(gcwq->trustee || gcwq->trustee_state != TRUSTEE_DONE);
3496 gcwq->trustee = new_trustee;
3497 gcwq->trustee_state = TRUSTEE_START;
3498 wake_up_process(gcwq->trustee);
3499 wait_trustee_state(gcwq, TRUSTEE_IN_CHARGE);
3500 /* fall through */
3501 case CPU_UP_PREPARE:
3502 BUG_ON(gcwq->first_idle);
3503 gcwq->first_idle = new_worker;
3504 break;
3506 case CPU_DYING:
3508 * Before this, the trustee and all workers except for
3509 * the ones which are still executing works from
3510 * before the last CPU down must be on the cpu. After
3511 * this, they'll all be diasporas.
3513 gcwq->flags |= GCWQ_DISASSOCIATED;
3514 break;
3516 case CPU_POST_DEAD:
3517 gcwq->trustee_state = TRUSTEE_BUTCHER;
3518 /* fall through */
3519 case CPU_UP_CANCELED:
3520 destroy_worker(gcwq->first_idle);
3521 gcwq->first_idle = NULL;
3522 break;
3524 case CPU_DOWN_FAILED:
3525 case CPU_ONLINE:
3526 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3527 if (gcwq->trustee_state != TRUSTEE_DONE) {
3528 gcwq->trustee_state = TRUSTEE_RELEASE;
3529 wake_up_process(gcwq->trustee);
3530 wait_trustee_state(gcwq, TRUSTEE_DONE);
3534 * Trustee is done and there might be no worker left.
3535 * Put the first_idle in and request a real manager to
3536 * take a look.
3538 spin_unlock_irq(&gcwq->lock);
3539 kthread_bind(gcwq->first_idle->task, cpu);
3540 spin_lock_irq(&gcwq->lock);
3541 gcwq->flags |= GCWQ_MANAGE_WORKERS;
3542 start_worker(gcwq->first_idle);
3543 gcwq->first_idle = NULL;
3544 break;
3547 spin_unlock_irqrestore(&gcwq->lock, flags);
3549 return notifier_from_errno(0);
3552 #ifdef CONFIG_SMP
3554 struct work_for_cpu {
3555 struct completion completion;
3556 long (*fn)(void *);
3557 void *arg;
3558 long ret;
3561 static int do_work_for_cpu(void *_wfc)
3563 struct work_for_cpu *wfc = _wfc;
3564 wfc->ret = wfc->fn(wfc->arg);
3565 complete(&wfc->completion);
3566 return 0;
3570 * work_on_cpu - run a function in user context on a particular cpu
3571 * @cpu: the cpu to run on
3572 * @fn: the function to run
3573 * @arg: the function arg
3575 * This will return the value @fn returns.
3576 * It is up to the caller to ensure that the cpu doesn't go offline.
3577 * The caller must not hold any locks which would prevent @fn from completing.
3579 long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
3581 struct task_struct *sub_thread;
3582 struct work_for_cpu wfc = {
3583 .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
3584 .fn = fn,
3585 .arg = arg,
3588 sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
3589 if (IS_ERR(sub_thread))
3590 return PTR_ERR(sub_thread);
3591 kthread_bind(sub_thread, cpu);
3592 wake_up_process(sub_thread);
3593 wait_for_completion(&wfc.completion);
3594 return wfc.ret;
3596 EXPORT_SYMBOL_GPL(work_on_cpu);
3597 #endif /* CONFIG_SMP */
3599 #ifdef CONFIG_FREEZER
3602 * freeze_workqueues_begin - begin freezing workqueues
3604 * Start freezing workqueues. After this function returns, all freezable
3605 * workqueues will queue new works to their frozen_works list instead of
3606 * gcwq->worklist.
3608 * CONTEXT:
3609 * Grabs and releases workqueue_lock and gcwq->lock's.
3611 void freeze_workqueues_begin(void)
3613 unsigned int cpu;
3615 spin_lock(&workqueue_lock);
3617 BUG_ON(workqueue_freezing);
3618 workqueue_freezing = true;
3620 for_each_gcwq_cpu(cpu) {
3621 struct global_cwq *gcwq = get_gcwq(cpu);
3622 struct workqueue_struct *wq;
3624 spin_lock_irq(&gcwq->lock);
3626 BUG_ON(gcwq->flags & GCWQ_FREEZING);
3627 gcwq->flags |= GCWQ_FREEZING;
3629 list_for_each_entry(wq, &workqueues, list) {
3630 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3632 if (cwq && wq->flags & WQ_FREEZABLE)
3633 cwq->max_active = 0;
3636 spin_unlock_irq(&gcwq->lock);
3639 spin_unlock(&workqueue_lock);
3643 * freeze_workqueues_busy - are freezable workqueues still busy?
3645 * Check whether freezing is complete. This function must be called
3646 * between freeze_workqueues_begin() and thaw_workqueues().
3648 * CONTEXT:
3649 * Grabs and releases workqueue_lock.
3651 * RETURNS:
3652 * %true if some freezable workqueues are still busy. %false if freezing
3653 * is complete.
3655 bool freeze_workqueues_busy(void)
3657 unsigned int cpu;
3658 bool busy = false;
3660 spin_lock(&workqueue_lock);
3662 BUG_ON(!workqueue_freezing);
3664 for_each_gcwq_cpu(cpu) {
3665 struct workqueue_struct *wq;
3667 * nr_active is monotonically decreasing. It's safe
3668 * to peek without lock.
3670 list_for_each_entry(wq, &workqueues, list) {
3671 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3673 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3674 continue;
3676 BUG_ON(cwq->nr_active < 0);
3677 if (cwq->nr_active) {
3678 busy = true;
3679 goto out_unlock;
3683 out_unlock:
3684 spin_unlock(&workqueue_lock);
3685 return busy;
3689 * thaw_workqueues - thaw workqueues
3691 * Thaw workqueues. Normal queueing is restored and all collected
3692 * frozen works are transferred to their respective gcwq worklists.
3694 * CONTEXT:
3695 * Grabs and releases workqueue_lock and gcwq->lock's.
3697 void thaw_workqueues(void)
3699 unsigned int cpu;
3701 spin_lock(&workqueue_lock);
3703 if (!workqueue_freezing)
3704 goto out_unlock;
3706 for_each_gcwq_cpu(cpu) {
3707 struct global_cwq *gcwq = get_gcwq(cpu);
3708 struct workqueue_struct *wq;
3710 spin_lock_irq(&gcwq->lock);
3712 BUG_ON(!(gcwq->flags & GCWQ_FREEZING));
3713 gcwq->flags &= ~GCWQ_FREEZING;
3715 list_for_each_entry(wq, &workqueues, list) {
3716 struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
3718 if (!cwq || !(wq->flags & WQ_FREEZABLE))
3719 continue;
3721 /* restore max_active and repopulate worklist */
3722 cwq->max_active = wq->saved_max_active;
3724 while (!list_empty(&cwq->delayed_works) &&
3725 cwq->nr_active < cwq->max_active)
3726 cwq_activate_first_delayed(cwq);
3729 wake_up_worker(gcwq);
3731 spin_unlock_irq(&gcwq->lock);
3734 workqueue_freezing = false;
3735 out_unlock:
3736 spin_unlock(&workqueue_lock);
3738 #endif /* CONFIG_FREEZER */
3740 static int __init init_workqueues(void)
3742 unsigned int cpu;
3743 int i;
3745 cpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE);
3747 /* initialize gcwqs */
3748 for_each_gcwq_cpu(cpu) {
3749 struct global_cwq *gcwq = get_gcwq(cpu);
3751 spin_lock_init(&gcwq->lock);
3752 INIT_LIST_HEAD(&gcwq->worklist);
3753 gcwq->cpu = cpu;
3754 gcwq->flags |= GCWQ_DISASSOCIATED;
3756 INIT_LIST_HEAD(&gcwq->idle_list);
3757 for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++)
3758 INIT_HLIST_HEAD(&gcwq->busy_hash[i]);
3760 init_timer_deferrable(&gcwq->idle_timer);
3761 gcwq->idle_timer.function = idle_worker_timeout;
3762 gcwq->idle_timer.data = (unsigned long)gcwq;
3764 setup_timer(&gcwq->mayday_timer, gcwq_mayday_timeout,
3765 (unsigned long)gcwq);
3767 ida_init(&gcwq->worker_ida);
3769 gcwq->trustee_state = TRUSTEE_DONE;
3770 init_waitqueue_head(&gcwq->trustee_wait);
3773 /* create the initial worker */
3774 for_each_online_gcwq_cpu(cpu) {
3775 struct global_cwq *gcwq = get_gcwq(cpu);
3776 struct worker *worker;
3778 if (cpu != WORK_CPU_UNBOUND)
3779 gcwq->flags &= ~GCWQ_DISASSOCIATED;
3780 worker = create_worker(gcwq, true);
3781 BUG_ON(!worker);
3782 spin_lock_irq(&gcwq->lock);
3783 start_worker(worker);
3784 spin_unlock_irq(&gcwq->lock);
3787 system_wq = alloc_workqueue("events", 0, 0);
3788 system_long_wq = alloc_workqueue("events_long", 0, 0);
3789 system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0);
3790 system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND,
3791 WQ_UNBOUND_MAX_ACTIVE);
3792 system_freezable_wq = alloc_workqueue("events_freezable",
3793 WQ_FREEZABLE, 0);
3794 BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq ||
3795 !system_unbound_wq || !system_freezable_wq);
3796 return 0;
3798 early_initcall(init_workqueues);