projects/linux·blob v2.6.27-rc5 · refs

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1/*
2 * linux/kernel/workqueue.c
3 *
4 * Generic mechanism for defining kernel helper threads for running
5 * arbitrary tasks in process context.
6 *
7 * Started by Ingo Molnar, Copyright (C) 2002
8 *
9 * Derived from the taskqueue/keventd code by:
10 *
11 * David Woodhouse <[email protected]>
12 * Andrew Morton <[email protected]>
13 * Kai Petzke <[email protected]>
14 * Theodore Ts'o <[email protected]>
15 *
16 * Made to use alloc_percpu by Christoph Lameter.
17 */
18
19#include <linux/module.h>
20#include <linux/kernel.h>
21#include <linux/sched.h>
22#include <linux/init.h>
23#include <linux/signal.h>
24#include <linux/completion.h>
25#include <linux/workqueue.h>
26#include <linux/slab.h>
27#include <linux/cpu.h>
28#include <linux/notifier.h>
29#include <linux/kthread.h>
30#include <linux/hardirq.h>
31#include <linux/mempolicy.h>
32#include <linux/freezer.h>
33#include <linux/kallsyms.h>
34#include <linux/debug_locks.h>
35#include <linux/lockdep.h>
36
37/*
38 * The per-CPU workqueue (if single thread, we always use the first
39 * possible cpu).
40 */
41struct cpu_workqueue_struct {
42
43 spinlock_t lock;
44
45 struct list_head worklist;
46 wait_queue_head_t more_work;
47 struct work_struct *current_work;
48
49 struct workqueue_struct *wq;
50 struct task_struct *thread;
51
52 int run_depth; /* Detect run_workqueue() recursion depth */
53} ____cacheline_aligned;
54
55/*
56 * The externally visible workqueue abstraction is an array of
57 * per-CPU workqueues:
58 */
59struct workqueue_struct {
60 struct cpu_workqueue_struct *cpu_wq;
61 struct list_head list;
62 const char *name;
63 int singlethread;
64 int freezeable; /* Freeze threads during suspend */
65#ifdef CONFIG_LOCKDEP
66 struct lockdep_map lockdep_map;
67#endif
68};
69
70/* Serializes the accesses to the list of workqueues. */
71static DEFINE_SPINLOCK(workqueue_lock);
72static LIST_HEAD(workqueues);
73
74static int singlethread_cpu __read_mostly;
75static cpumask_t cpu_singlethread_map __read_mostly;
76/*
77 * _cpu_down() first removes CPU from cpu_online_map, then CPU_DEAD
78 * flushes cwq->worklist. This means that flush_workqueue/wait_on_work
79 * which comes in between can't use for_each_online_cpu(). We could
80 * use cpu_possible_map, the cpumask below is more a documentation
81 * than optimization.
82 */
83static cpumask_t cpu_populated_map __read_mostly;
84
85/* If it's single threaded, it isn't in the list of workqueues. */
86static inline int is_single_threaded(struct workqueue_struct *wq)
87{
88 return wq->singlethread;
89}
90
91static const cpumask_t *wq_cpu_map(struct workqueue_struct *wq)
92{
93 return is_single_threaded(wq)
94 ? &cpu_singlethread_map : &cpu_populated_map;
95}
96
97static
98struct cpu_workqueue_struct *wq_per_cpu(struct workqueue_struct *wq, int cpu)
99{
100 if (unlikely(is_single_threaded(wq)))
101 cpu = singlethread_cpu;
102 return per_cpu_ptr(wq->cpu_wq, cpu);
103}
104
105/*
106 * Set the workqueue on which a work item is to be run
107 * - Must *only* be called if the pending flag is set
108 */
109static inline void set_wq_data(struct work_struct *work,
110 struct cpu_workqueue_struct *cwq)
111{
112 unsigned long new;
113
114 BUG_ON(!work_pending(work));
115
116 new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING);
117 new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
118 atomic_long_set(&work->data, new);
119}
120
121static inline
122struct cpu_workqueue_struct *get_wq_data(struct work_struct *work)
123{
124 return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);
125}
126
127static void insert_work(struct cpu_workqueue_struct *cwq,
128 struct work_struct *work, struct list_head *head)
129{
130 set_wq_data(work, cwq);
131 /*
132 * Ensure that we get the right work->data if we see the
133 * result of list_add() below, see try_to_grab_pending().
134 */
135 smp_wmb();
136 list_add_tail(&work->entry, head);
137 wake_up(&cwq->more_work);
138}
139
140static void __queue_work(struct cpu_workqueue_struct *cwq,
141 struct work_struct *work)
142{
143 unsigned long flags;
144
145 spin_lock_irqsave(&cwq->lock, flags);
146 insert_work(cwq, work, &cwq->worklist);
147 spin_unlock_irqrestore(&cwq->lock, flags);
148}
149
150/**
151 * queue_work - queue work on a workqueue
152 * @wq: workqueue to use
153 * @work: work to queue
154 *
155 * Returns 0 if @work was already on a queue, non-zero otherwise.
156 *
157 * We queue the work to the CPU on which it was submitted, but if the CPU dies
158 * it can be processed by another CPU.
159 */
160int queue_work(struct workqueue_struct *wq, struct work_struct *work)
161{
162 int ret;
163
164 ret = queue_work_on(get_cpu(), wq, work);
165 put_cpu();
166
167 return ret;
168}
169EXPORT_SYMBOL_GPL(queue_work);
170
171/**
172 * queue_work_on - queue work on specific cpu
173 * @cpu: CPU number to execute work on
174 * @wq: workqueue to use
175 * @work: work to queue
176 *
177 * Returns 0 if @work was already on a queue, non-zero otherwise.
178 *
179 * We queue the work to a specific CPU, the caller must ensure it
180 * can't go away.
181 */
182int
183queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
184{
185 int ret = 0;
186
187 if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
188 BUG_ON(!list_empty(&work->entry));
189 __queue_work(wq_per_cpu(wq, cpu), work);
190 ret = 1;
191 }
192 return ret;
193}
194EXPORT_SYMBOL_GPL(queue_work_on);
195
196static void delayed_work_timer_fn(unsigned long __data)
197{
198 struct delayed_work *dwork = (struct delayed_work *)__data;
199 struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work);
200 struct workqueue_struct *wq = cwq->wq;
201
202 __queue_work(wq_per_cpu(wq, smp_processor_id()), &dwork->work);
203}
204
205/**
206 * queue_delayed_work - queue work on a workqueue after delay
207 * @wq: workqueue to use
208 * @dwork: delayable work to queue
209 * @delay: number of jiffies to wait before queueing
210 *
211 * Returns 0 if @work was already on a queue, non-zero otherwise.
212 */
213int queue_delayed_work(struct workqueue_struct *wq,
214 struct delayed_work *dwork, unsigned long delay)
215{
216 if (delay == 0)
217 return queue_work(wq, &dwork->work);
218
219 return queue_delayed_work_on(-1, wq, dwork, delay);
220}
221EXPORT_SYMBOL_GPL(queue_delayed_work);
222
223/**
224 * queue_delayed_work_on - queue work on specific CPU after delay
225 * @cpu: CPU number to execute work on
226 * @wq: workqueue to use
227 * @dwork: work to queue
228 * @delay: number of jiffies to wait before queueing
229 *
230 * Returns 0 if @work was already on a queue, non-zero otherwise.
231 */
232int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
233 struct delayed_work *dwork, unsigned long delay)
234{
235 int ret = 0;
236 struct timer_list *timer = &dwork->timer;
237 struct work_struct *work = &dwork->work;
238
239 if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
240 BUG_ON(timer_pending(timer));
241 BUG_ON(!list_empty(&work->entry));
242
243 timer_stats_timer_set_start_info(&dwork->timer);
244
245 /* This stores cwq for the moment, for the timer_fn */
246 set_wq_data(work, wq_per_cpu(wq, raw_smp_processor_id()));
247 timer->expires = jiffies + delay;
248 timer->data = (unsigned long)dwork;
249 timer->function = delayed_work_timer_fn;
250
251 if (unlikely(cpu >= 0))
252 add_timer_on(timer, cpu);
253 else
254 add_timer(timer);
255 ret = 1;
256 }
257 return ret;
258}
259EXPORT_SYMBOL_GPL(queue_delayed_work_on);
260
261static void run_workqueue(struct cpu_workqueue_struct *cwq)
262{
263 spin_lock_irq(&cwq->lock);
264 cwq->run_depth++;
265 if (cwq->run_depth > 3) {
266 /* morton gets to eat his hat */
267 printk("%s: recursion depth exceeded: %d\n",
268 __func__, cwq->run_depth);
269 dump_stack();
270 }
271 while (!list_empty(&cwq->worklist)) {
272 struct work_struct *work = list_entry(cwq->worklist.next,
273 struct work_struct, entry);
274 work_func_t f = work->func;
275#ifdef CONFIG_LOCKDEP
276 /*
277 * It is permissible to free the struct work_struct
278 * from inside the function that is called from it,
279 * this we need to take into account for lockdep too.
280 * To avoid bogus "held lock freed" warnings as well
281 * as problems when looking into work->lockdep_map,
282 * make a copy and use that here.
283 */
284 struct lockdep_map lockdep_map = work->lockdep_map;
285#endif
286
287 cwq->current_work = work;
288 list_del_init(cwq->worklist.next);
289 spin_unlock_irq(&cwq->lock);
290
291 BUG_ON(get_wq_data(work) != cwq);
292 work_clear_pending(work);
293 lock_map_acquire(&cwq->wq->lockdep_map);
294 lock_map_acquire(&lockdep_map);
295 f(work);
296 lock_map_release(&lockdep_map);
297 lock_map_release(&cwq->wq->lockdep_map);
298
299 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
300 printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
301 "%s/0x%08x/%d\n",
302 current->comm, preempt_count(),
303 task_pid_nr(current));
304 printk(KERN_ERR " last function: ");
305 print_symbol("%s\n", (unsigned long)f);
306 debug_show_held_locks(current);
307 dump_stack();
308 }
309
310 spin_lock_irq(&cwq->lock);
311 cwq->current_work = NULL;
312 }
313 cwq->run_depth--;
314 spin_unlock_irq(&cwq->lock);
315}
316
317static int worker_thread(void *__cwq)
318{
319 struct cpu_workqueue_struct *cwq = __cwq;
320 DEFINE_WAIT(wait);
321
322 if (cwq->wq->freezeable)
323 set_freezable();
324
325 set_user_nice(current, -5);
326
327 for (;;) {
328 prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);
329 if (!freezing(current) &&
330 !kthread_should_stop() &&
331 list_empty(&cwq->worklist))
332 schedule();
333 finish_wait(&cwq->more_work, &wait);
334
335 try_to_freeze();
336
337 if (kthread_should_stop())
338 break;
339
340 run_workqueue(cwq);
341 }
342
343 return 0;
344}
345
346struct wq_barrier {
347 struct work_struct work;
348 struct completion done;
349};
350
351static void wq_barrier_func(struct work_struct *work)
352{
353 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
354 complete(&barr->done);
355}
356
357static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
358 struct wq_barrier *barr, struct list_head *head)
359{
360 INIT_WORK(&barr->work, wq_barrier_func);
361 __set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
362
363 init_completion(&barr->done);
364
365 insert_work(cwq, &barr->work, head);
366}
367
368static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
369{
370 int active;
371
372 if (cwq->thread == current) {
373 /*
374 * Probably keventd trying to flush its own queue. So simply run
375 * it by hand rather than deadlocking.
376 */
377 run_workqueue(cwq);
378 active = 1;
379 } else {
380 struct wq_barrier barr;
381
382 active = 0;
383 spin_lock_irq(&cwq->lock);
384 if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
385 insert_wq_barrier(cwq, &barr, &cwq->worklist);
386 active = 1;
387 }
388 spin_unlock_irq(&cwq->lock);
389
390 if (active)
391 wait_for_completion(&barr.done);
392 }
393
394 return active;
395}
396
397/**
398 * flush_workqueue - ensure that any scheduled work has run to completion.
399 * @wq: workqueue to flush
400 *
401 * Forces execution of the workqueue and blocks until its completion.
402 * This is typically used in driver shutdown handlers.
403 *
404 * We sleep until all works which were queued on entry have been handled,
405 * but we are not livelocked by new incoming ones.
406 *
407 * This function used to run the workqueues itself. Now we just wait for the
408 * helper threads to do it.
409 */
410void flush_workqueue(struct workqueue_struct *wq)
411{
412 const cpumask_t *cpu_map = wq_cpu_map(wq);
413 int cpu;
414
415 might_sleep();
416 lock_map_acquire(&wq->lockdep_map);
417 lock_map_release(&wq->lockdep_map);
418 for_each_cpu_mask_nr(cpu, *cpu_map)
419 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
420}
421EXPORT_SYMBOL_GPL(flush_workqueue);
422
423/**
424 * flush_work - block until a work_struct's callback has terminated
425 * @work: the work which is to be flushed
426 *
427 * Returns false if @work has already terminated.
428 *
429 * It is expected that, prior to calling flush_work(), the caller has
430 * arranged for the work to not be requeued, otherwise it doesn't make
431 * sense to use this function.
432 */
433int flush_work(struct work_struct *work)
434{
435 struct cpu_workqueue_struct *cwq;
436 struct list_head *prev;
437 struct wq_barrier barr;
438
439 might_sleep();
440 cwq = get_wq_data(work);
441 if (!cwq)
442 return 0;
443
444 lock_map_acquire(&cwq->wq->lockdep_map);
445 lock_map_release(&cwq->wq->lockdep_map);
446
447 prev = NULL;
448 spin_lock_irq(&cwq->lock);
449 if (!list_empty(&work->entry)) {
450 /*
451 * See the comment near try_to_grab_pending()->smp_rmb().
452 * If it was re-queued under us we are not going to wait.
453 */
454 smp_rmb();
455 if (unlikely(cwq != get_wq_data(work)))
456 goto out;
457 prev = &work->entry;
458 } else {
459 if (cwq->current_work != work)
460 goto out;
461 prev = &cwq->worklist;
462 }
463 insert_wq_barrier(cwq, &barr, prev->next);
464out:
465 spin_unlock_irq(&cwq->lock);
466 if (!prev)
467 return 0;
468
469 wait_for_completion(&barr.done);
470 return 1;
471}
472EXPORT_SYMBOL_GPL(flush_work);
473
474/*
475 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
476 * so this work can't be re-armed in any way.
477 */
478static int try_to_grab_pending(struct work_struct *work)
479{
480 struct cpu_workqueue_struct *cwq;
481 int ret = -1;
482
483 if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work)))
484 return 0;
485
486 /*
487 * The queueing is in progress, or it is already queued. Try to
488 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
489 */
490
491 cwq = get_wq_data(work);
492 if (!cwq)
493 return ret;
494
495 spin_lock_irq(&cwq->lock);
496 if (!list_empty(&work->entry)) {
497 /*
498 * This work is queued, but perhaps we locked the wrong cwq.
499 * In that case we must see the new value after rmb(), see
500 * insert_work()->wmb().
501 */
502 smp_rmb();
503 if (cwq == get_wq_data(work)) {
504 list_del_init(&work->entry);
505 ret = 1;
506 }
507 }
508 spin_unlock_irq(&cwq->lock);
509
510 return ret;
511}
512
513static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq,
514 struct work_struct *work)
515{
516 struct wq_barrier barr;
517 int running = 0;
518
519 spin_lock_irq(&cwq->lock);
520 if (unlikely(cwq->current_work == work)) {
521 insert_wq_barrier(cwq, &barr, cwq->worklist.next);
522 running = 1;
523 }
524 spin_unlock_irq(&cwq->lock);
525
526 if (unlikely(running))
527 wait_for_completion(&barr.done);
528}
529
530static void wait_on_work(struct work_struct *work)
531{
532 struct cpu_workqueue_struct *cwq;
533 struct workqueue_struct *wq;
534 const cpumask_t *cpu_map;
535 int cpu;
536
537 might_sleep();
538
539 lock_map_acquire(&work->lockdep_map);
540 lock_map_release(&work->lockdep_map);
541
542 cwq = get_wq_data(work);
543 if (!cwq)
544 return;
545
546 wq = cwq->wq;
547 cpu_map = wq_cpu_map(wq);
548
549 for_each_cpu_mask_nr(cpu, *cpu_map)
550 wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
551}
552
553static int __cancel_work_timer(struct work_struct *work,
554 struct timer_list* timer)
555{
556 int ret;
557
558 do {
559 ret = (timer && likely(del_timer(timer)));
560 if (!ret)
561 ret = try_to_grab_pending(work);
562 wait_on_work(work);
563 } while (unlikely(ret < 0));
564
565 work_clear_pending(work);
566 return ret;
567}
568
569/**
570 * cancel_work_sync - block until a work_struct's callback has terminated
571 * @work: the work which is to be flushed
572 *
573 * Returns true if @work was pending.
574 *
575 * cancel_work_sync() will cancel the work if it is queued. If the work's
576 * callback appears to be running, cancel_work_sync() will block until it
577 * has completed.
578 *
579 * It is possible to use this function if the work re-queues itself. It can
580 * cancel the work even if it migrates to another workqueue, however in that
581 * case it only guarantees that work->func() has completed on the last queued
582 * workqueue.
583 *
584 * cancel_work_sync(&delayed_work->work) should be used only if ->timer is not
585 * pending, otherwise it goes into a busy-wait loop until the timer expires.
586 *
587 * The caller must ensure that workqueue_struct on which this work was last
588 * queued can't be destroyed before this function returns.
589 */
590int cancel_work_sync(struct work_struct *work)
591{
592 return __cancel_work_timer(work, NULL);
593}
594EXPORT_SYMBOL_GPL(cancel_work_sync);
595
596/**
597 * cancel_delayed_work_sync - reliably kill off a delayed work.
598 * @dwork: the delayed work struct
599 *
600 * Returns true if @dwork was pending.
601 *
602 * It is possible to use this function if @dwork rearms itself via queue_work()
603 * or queue_delayed_work(). See also the comment for cancel_work_sync().
604 */
605int cancel_delayed_work_sync(struct delayed_work *dwork)
606{
607 return __cancel_work_timer(&dwork->work, &dwork->timer);
608}
609EXPORT_SYMBOL(cancel_delayed_work_sync);
610
611static struct workqueue_struct *keventd_wq __read_mostly;
612
613/**
614 * schedule_work - put work task in global workqueue
615 * @work: job to be done
616 *
617 * This puts a job in the kernel-global workqueue.
618 */
619int schedule_work(struct work_struct *work)
620{
621 return queue_work(keventd_wq, work);
622}
623EXPORT_SYMBOL(schedule_work);
624
625/*
626 * schedule_work_on - put work task on a specific cpu
627 * @cpu: cpu to put the work task on
628 * @work: job to be done
629 *
630 * This puts a job on a specific cpu
631 */
632int schedule_work_on(int cpu, struct work_struct *work)
633{
634 return queue_work_on(cpu, keventd_wq, work);
635}
636EXPORT_SYMBOL(schedule_work_on);
637
638/**
639 * schedule_delayed_work - put work task in global workqueue after delay
640 * @dwork: job to be done
641 * @delay: number of jiffies to wait or 0 for immediate execution
642 *
643 * After waiting for a given time this puts a job in the kernel-global
644 * workqueue.
645 */
646int schedule_delayed_work(struct delayed_work *dwork,
647 unsigned long delay)
648{
649 return queue_delayed_work(keventd_wq, dwork, delay);
650}
651EXPORT_SYMBOL(schedule_delayed_work);
652
653/**
654 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
655 * @cpu: cpu to use
656 * @dwork: job to be done
657 * @delay: number of jiffies to wait
658 *
659 * After waiting for a given time this puts a job in the kernel-global
660 * workqueue on the specified CPU.
661 */
662int schedule_delayed_work_on(int cpu,
663 struct delayed_work *dwork, unsigned long delay)
664{
665 return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
666}
667EXPORT_SYMBOL(schedule_delayed_work_on);
668
669/**
670 * schedule_on_each_cpu - call a function on each online CPU from keventd
671 * @func: the function to call
672 *
673 * Returns zero on success.
674 * Returns -ve errno on failure.
675 *
676 * schedule_on_each_cpu() is very slow.
677 */
678int schedule_on_each_cpu(work_func_t func)
679{
680 int cpu;
681 struct work_struct *works;
682
683 works = alloc_percpu(struct work_struct);
684 if (!works)
685 return -ENOMEM;
686
687 get_online_cpus();
688 for_each_online_cpu(cpu) {
689 struct work_struct *work = per_cpu_ptr(works, cpu);
690
691 INIT_WORK(work, func);
692 schedule_work_on(cpu, work);
693 }
694 for_each_online_cpu(cpu)
695 flush_work(per_cpu_ptr(works, cpu));
696 put_online_cpus();
697 free_percpu(works);
698 return 0;
699}
700
701void flush_scheduled_work(void)
702{
703 flush_workqueue(keventd_wq);
704}
705EXPORT_SYMBOL(flush_scheduled_work);
706
707/**
708 * execute_in_process_context - reliably execute the routine with user context
709 * @fn: the function to execute
710 * @ew: guaranteed storage for the execute work structure (must
711 * be available when the work executes)
712 *
713 * Executes the function immediately if process context is available,
714 * otherwise schedules the function for delayed execution.
715 *
716 * Returns: 0 - function was executed
717 * 1 - function was scheduled for execution
718 */
719int execute_in_process_context(work_func_t fn, struct execute_work *ew)
720{
721 if (!in_interrupt()) {
722 fn(&ew->work);
723 return 0;
724 }
725
726 INIT_WORK(&ew->work, fn);
727 schedule_work(&ew->work);
728
729 return 1;
730}
731EXPORT_SYMBOL_GPL(execute_in_process_context);
732
733int keventd_up(void)
734{
735 return keventd_wq != NULL;
736}
737
738int current_is_keventd(void)
739{
740 struct cpu_workqueue_struct *cwq;
741 int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */
742 int ret = 0;
743
744 BUG_ON(!keventd_wq);
745
746 cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
747 if (current == cwq->thread)
748 ret = 1;
749
750 return ret;
751
752}
753
754static struct cpu_workqueue_struct *
755init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
756{
757 struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
758
759 cwq->wq = wq;
760 spin_lock_init(&cwq->lock);
761 INIT_LIST_HEAD(&cwq->worklist);
762 init_waitqueue_head(&cwq->more_work);
763
764 return cwq;
765}
766
767static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
768{
769 struct workqueue_struct *wq = cwq->wq;
770 const char *fmt = is_single_threaded(wq) ? "%s" : "%s/%d";
771 struct task_struct *p;
772
773 p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);
774 /*
775 * Nobody can add the work_struct to this cwq,
776 * if (caller is __create_workqueue)
777 * nobody should see this wq
778 * else // caller is CPU_UP_PREPARE
779 * cpu is not on cpu_online_map
780 * so we can abort safely.
781 */
782 if (IS_ERR(p))
783 return PTR_ERR(p);
784
785 cwq->thread = p;
786
787 return 0;
788}
789
790static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
791{
792 struct task_struct *p = cwq->thread;
793
794 if (p != NULL) {
795 if (cpu >= 0)
796 kthread_bind(p, cpu);
797 wake_up_process(p);
798 }
799}
800
801struct workqueue_struct *__create_workqueue_key(const char *name,
802 int singlethread,
803 int freezeable,
804 struct lock_class_key *key,
805 const char *lock_name)
806{
807 struct workqueue_struct *wq;
808 struct cpu_workqueue_struct *cwq;
809 int err = 0, cpu;
810
811 wq = kzalloc(sizeof(*wq), GFP_KERNEL);
812 if (!wq)
813 return NULL;
814
815 wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
816 if (!wq->cpu_wq) {
817 kfree(wq);
818 return NULL;
819 }
820
821 wq->name = name;
822 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
823 wq->singlethread = singlethread;
824 wq->freezeable = freezeable;
825 INIT_LIST_HEAD(&wq->list);
826
827 if (singlethread) {
828 cwq = init_cpu_workqueue(wq, singlethread_cpu);
829 err = create_workqueue_thread(cwq, singlethread_cpu);
830 start_workqueue_thread(cwq, -1);
831 } else {
832 cpu_maps_update_begin();
833 /*
834 * We must place this wq on list even if the code below fails.
835 * cpu_down(cpu) can remove cpu from cpu_populated_map before
836 * destroy_workqueue() takes the lock, in that case we leak
837 * cwq[cpu]->thread.
838 */
839 spin_lock(&workqueue_lock);
840 list_add(&wq->list, &workqueues);
841 spin_unlock(&workqueue_lock);
842 /*
843 * We must initialize cwqs for each possible cpu even if we
844 * are going to call destroy_workqueue() finally. Otherwise
845 * cpu_up() can hit the uninitialized cwq once we drop the
846 * lock.
847 */
848 for_each_possible_cpu(cpu) {
849 cwq = init_cpu_workqueue(wq, cpu);
850 if (err || !cpu_online(cpu))
851 continue;
852 err = create_workqueue_thread(cwq, cpu);
853 start_workqueue_thread(cwq, cpu);
854 }
855 cpu_maps_update_done();
856 }
857
858 if (err) {
859 destroy_workqueue(wq);
860 wq = NULL;
861 }
862 return wq;
863}
864EXPORT_SYMBOL_GPL(__create_workqueue_key);
865
866static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq)
867{
868 /*
869 * Our caller is either destroy_workqueue() or CPU_POST_DEAD,
870 * cpu_add_remove_lock protects cwq->thread.
871 */
872 if (cwq->thread == NULL)
873 return;
874
875 lock_map_acquire(&cwq->wq->lockdep_map);
876 lock_map_release(&cwq->wq->lockdep_map);
877
878 flush_cpu_workqueue(cwq);
879 /*
880 * If the caller is CPU_POST_DEAD and cwq->worklist was not empty,
881 * a concurrent flush_workqueue() can insert a barrier after us.
882 * However, in that case run_workqueue() won't return and check
883 * kthread_should_stop() until it flushes all work_struct's.
884 * When ->worklist becomes empty it is safe to exit because no
885 * more work_structs can be queued on this cwq: flush_workqueue
886 * checks list_empty(), and a "normal" queue_work() can't use
887 * a dead CPU.
888 */
889 kthread_stop(cwq->thread);
890 cwq->thread = NULL;
891}
892
893/**
894 * destroy_workqueue - safely terminate a workqueue
895 * @wq: target workqueue
896 *
897 * Safely destroy a workqueue. All work currently pending will be done first.
898 */
899void destroy_workqueue(struct workqueue_struct *wq)
900{
901 const cpumask_t *cpu_map = wq_cpu_map(wq);
902 int cpu;
903
904 cpu_maps_update_begin();
905 spin_lock(&workqueue_lock);
906 list_del(&wq->list);
907 spin_unlock(&workqueue_lock);
908
909 for_each_cpu_mask_nr(cpu, *cpu_map)
910 cleanup_workqueue_thread(per_cpu_ptr(wq->cpu_wq, cpu));
911 cpu_maps_update_done();
912
913 free_percpu(wq->cpu_wq);
914 kfree(wq);
915}
916EXPORT_SYMBOL_GPL(destroy_workqueue);
917
918static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
919 unsigned long action,
920 void *hcpu)
921{
922 unsigned int cpu = (unsigned long)hcpu;
923 struct cpu_workqueue_struct *cwq;
924 struct workqueue_struct *wq;
925 int ret = NOTIFY_OK;
926
927 action &= ~CPU_TASKS_FROZEN;
928
929 switch (action) {
930 case CPU_UP_PREPARE:
931 cpu_set(cpu, cpu_populated_map);
932 }
933undo:
934 list_for_each_entry(wq, &workqueues, list) {
935 cwq = per_cpu_ptr(wq->cpu_wq, cpu);
936
937 switch (action) {
938 case CPU_UP_PREPARE:
939 if (!create_workqueue_thread(cwq, cpu))
940 break;
941 printk(KERN_ERR "workqueue [%s] for %i failed\n",
942 wq->name, cpu);
943 action = CPU_UP_CANCELED;
944 ret = NOTIFY_BAD;
945 goto undo;
946
947 case CPU_ONLINE:
948 start_workqueue_thread(cwq, cpu);
949 break;
950
951 case CPU_UP_CANCELED:
952 start_workqueue_thread(cwq, -1);
953 case CPU_POST_DEAD:
954 cleanup_workqueue_thread(cwq);
955 break;
956 }
957 }
958
959 switch (action) {
960 case CPU_UP_CANCELED:
961 case CPU_POST_DEAD:
962 cpu_clear(cpu, cpu_populated_map);
963 }
964
965 return ret;
966}
967
968void __init init_workqueues(void)
969{
970 cpu_populated_map = cpu_online_map;
971 singlethread_cpu = first_cpu(cpu_possible_map);
972 cpu_singlethread_map = cpumask_of_cpu(singlethread_cpu);
973 hotcpu_notifier(workqueue_cpu_callback, 0);
974 keventd_wq = create_workqueue("events");
975 BUG_ON(!keventd_wq);
976}