967479756511a9c15e10e8fa3fb27c346982da7f
[linux-2.6.git] / kernel / workqueue.c
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 <dwmw2@infradead.org>
12  *   Andrew Morton <andrewm@uow.edu.au>
13  *   Kai Petzke <wpp@marie.physik.tu-berlin.de>
14  *   Theodore Ts'o <tytso@mit.edu>
15  *
16  * Made to use alloc_percpu by Christoph Lameter <clameter@sgi.com>.
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
33 /*
34  * The per-CPU workqueue (if single thread, we always use the first
35  * possible cpu).
36  *
37  * The sequence counters are for flush_scheduled_work().  It wants to wait
38  * until all currently-scheduled works are completed, but it doesn't
39  * want to be livelocked by new, incoming ones.  So it waits until
40  * remove_sequence is >= the insert_sequence which pertained when
41  * flush_scheduled_work() was called.
42  */
43 struct cpu_workqueue_struct {
44
45         spinlock_t lock;
46
47         long remove_sequence;   /* Least-recently added (next to run) */
48         long insert_sequence;   /* Next to add */
49
50         struct list_head worklist;
51         wait_queue_head_t more_work;
52         wait_queue_head_t work_done;
53
54         struct workqueue_struct *wq;
55         struct task_struct *thread;
56
57         int run_depth;          /* Detect run_workqueue() recursion depth */
58 } ____cacheline_aligned;
59
60 /*
61  * The externally visible workqueue abstraction is an array of
62  * per-CPU workqueues:
63  */
64 struct workqueue_struct {
65         struct cpu_workqueue_struct *cpu_wq;
66         const char *name;
67         struct list_head list;  /* Empty if single thread */
68 };
69
70 /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
71    threads to each one as cpus come/go. */
72 static DEFINE_MUTEX(workqueue_mutex);
73 static LIST_HEAD(workqueues);
74
75 static int singlethread_cpu;
76
77 /* If it's single threaded, it isn't in the list of workqueues. */
78 static inline int is_single_threaded(struct workqueue_struct *wq)
79 {
80         return list_empty(&wq->list);
81 }
82
83 static inline void set_wq_data(struct work_struct *work, void *wq)
84 {
85         unsigned long new, old, res;
86
87         /* assume the pending flag is already set and that the task has already
88          * been queued on this workqueue */
89         new = (unsigned long) wq | (1UL << WORK_STRUCT_PENDING);
90         res = work->management;
91         if (res != new) {
92                 do {
93                         old = res;
94                         new = (unsigned long) wq;
95                         new |= (old & WORK_STRUCT_FLAG_MASK);
96                         res = cmpxchg(&work->management, old, new);
97                 } while (res != old);
98         }
99 }
100
101 static inline void *get_wq_data(struct work_struct *work)
102 {
103         return (void *) (work->management & WORK_STRUCT_WQ_DATA_MASK);
104 }
105
106 /* Preempt must be disabled. */
107 static void __queue_work(struct cpu_workqueue_struct *cwq,
108                          struct work_struct *work)
109 {
110         unsigned long flags;
111
112         spin_lock_irqsave(&cwq->lock, flags);
113         set_wq_data(work, cwq);
114         list_add_tail(&work->entry, &cwq->worklist);
115         cwq->insert_sequence++;
116         wake_up(&cwq->more_work);
117         spin_unlock_irqrestore(&cwq->lock, flags);
118 }
119
120 /**
121  * queue_work - queue work on a workqueue
122  * @wq: workqueue to use
123  * @work: work to queue
124  *
125  * Returns 0 if @work was already on a queue, non-zero otherwise.
126  *
127  * We queue the work to the CPU it was submitted, but there is no
128  * guarantee that it will be processed by that CPU.
129  */
130 int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
131 {
132         int ret = 0, cpu = get_cpu();
133
134         if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
135                 if (unlikely(is_single_threaded(wq)))
136                         cpu = singlethread_cpu;
137                 BUG_ON(!list_empty(&work->entry));
138                 __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
139                 ret = 1;
140         }
141         put_cpu();
142         return ret;
143 }
144 EXPORT_SYMBOL_GPL(queue_work);
145
146 static void delayed_work_timer_fn(unsigned long __data)
147 {
148         struct delayed_work *dwork = (struct delayed_work *)__data;
149         struct workqueue_struct *wq = get_wq_data(&dwork->work);
150         int cpu = smp_processor_id();
151
152         if (unlikely(is_single_threaded(wq)))
153                 cpu = singlethread_cpu;
154
155         __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), &dwork->work);
156 }
157
158 /**
159  * queue_delayed_work - queue work on a workqueue after delay
160  * @wq: workqueue to use
161  * @work: delayable work to queue
162  * @delay: number of jiffies to wait before queueing
163  *
164  * Returns 0 if @work was already on a queue, non-zero otherwise.
165  */
166 int fastcall queue_delayed_work(struct workqueue_struct *wq,
167                         struct delayed_work *dwork, unsigned long delay)
168 {
169         int ret = 0;
170         struct timer_list *timer = &dwork->timer;
171         struct work_struct *work = &dwork->work;
172
173         if (delay == 0)
174                 return queue_work(wq, work);
175
176         if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
177                 BUG_ON(timer_pending(timer));
178                 BUG_ON(!list_empty(&work->entry));
179
180                 /* This stores wq for the moment, for the timer_fn */
181                 set_wq_data(work, wq);
182                 timer->expires = jiffies + delay;
183                 timer->data = (unsigned long)dwork;
184                 timer->function = delayed_work_timer_fn;
185                 add_timer(timer);
186                 ret = 1;
187         }
188         return ret;
189 }
190 EXPORT_SYMBOL_GPL(queue_delayed_work);
191
192 /**
193  * queue_delayed_work_on - queue work on specific CPU after delay
194  * @cpu: CPU number to execute work on
195  * @wq: workqueue to use
196  * @work: work to queue
197  * @delay: number of jiffies to wait before queueing
198  *
199  * Returns 0 if @work was already on a queue, non-zero otherwise.
200  */
201 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
202                         struct delayed_work *dwork, unsigned long delay)
203 {
204         int ret = 0;
205         struct timer_list *timer = &dwork->timer;
206         struct work_struct *work = &dwork->work;
207
208         if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
209                 BUG_ON(timer_pending(timer));
210                 BUG_ON(!list_empty(&work->entry));
211
212                 /* This stores wq for the moment, for the timer_fn */
213                 set_wq_data(work, wq);
214                 timer->expires = jiffies + delay;
215                 timer->data = (unsigned long)dwork;
216                 timer->function = delayed_work_timer_fn;
217                 add_timer_on(timer, cpu);
218                 ret = 1;
219         }
220         return ret;
221 }
222 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
223
224 static void run_workqueue(struct cpu_workqueue_struct *cwq)
225 {
226         unsigned long flags;
227
228         /*
229          * Keep taking off work from the queue until
230          * done.
231          */
232         spin_lock_irqsave(&cwq->lock, flags);
233         cwq->run_depth++;
234         if (cwq->run_depth > 3) {
235                 /* morton gets to eat his hat */
236                 printk("%s: recursion depth exceeded: %d\n",
237                         __FUNCTION__, cwq->run_depth);
238                 dump_stack();
239         }
240         while (!list_empty(&cwq->worklist)) {
241                 struct work_struct *work = list_entry(cwq->worklist.next,
242                                                 struct work_struct, entry);
243                 work_func_t f = work->func;
244                 void *data = work->data;
245
246                 list_del_init(cwq->worklist.next);
247                 spin_unlock_irqrestore(&cwq->lock, flags);
248
249                 BUG_ON(get_wq_data(work) != cwq);
250                 clear_bit(WORK_STRUCT_PENDING, &work->management);
251                 f(data);
252
253                 spin_lock_irqsave(&cwq->lock, flags);
254                 cwq->remove_sequence++;
255                 wake_up(&cwq->work_done);
256         }
257         cwq->run_depth--;
258         spin_unlock_irqrestore(&cwq->lock, flags);
259 }
260
261 static int worker_thread(void *__cwq)
262 {
263         struct cpu_workqueue_struct *cwq = __cwq;
264         DECLARE_WAITQUEUE(wait, current);
265         struct k_sigaction sa;
266         sigset_t blocked;
267
268         current->flags |= PF_NOFREEZE;
269
270         set_user_nice(current, -5);
271
272         /* Block and flush all signals */
273         sigfillset(&blocked);
274         sigprocmask(SIG_BLOCK, &blocked, NULL);
275         flush_signals(current);
276
277         /*
278          * We inherited MPOL_INTERLEAVE from the booting kernel.
279          * Set MPOL_DEFAULT to insure node local allocations.
280          */
281         numa_default_policy();
282
283         /* SIG_IGN makes children autoreap: see do_notify_parent(). */
284         sa.sa.sa_handler = SIG_IGN;
285         sa.sa.sa_flags = 0;
286         siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
287         do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
288
289         set_current_state(TASK_INTERRUPTIBLE);
290         while (!kthread_should_stop()) {
291                 add_wait_queue(&cwq->more_work, &wait);
292                 if (list_empty(&cwq->worklist))
293                         schedule();
294                 else
295                         __set_current_state(TASK_RUNNING);
296                 remove_wait_queue(&cwq->more_work, &wait);
297
298                 if (!list_empty(&cwq->worklist))
299                         run_workqueue(cwq);
300                 set_current_state(TASK_INTERRUPTIBLE);
301         }
302         __set_current_state(TASK_RUNNING);
303         return 0;
304 }
305
306 static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
307 {
308         if (cwq->thread == current) {
309                 /*
310                  * Probably keventd trying to flush its own queue. So simply run
311                  * it by hand rather than deadlocking.
312                  */
313                 run_workqueue(cwq);
314         } else {
315                 DEFINE_WAIT(wait);
316                 long sequence_needed;
317
318                 spin_lock_irq(&cwq->lock);
319                 sequence_needed = cwq->insert_sequence;
320
321                 while (sequence_needed - cwq->remove_sequence > 0) {
322                         prepare_to_wait(&cwq->work_done, &wait,
323                                         TASK_UNINTERRUPTIBLE);
324                         spin_unlock_irq(&cwq->lock);
325                         schedule();
326                         spin_lock_irq(&cwq->lock);
327                 }
328                 finish_wait(&cwq->work_done, &wait);
329                 spin_unlock_irq(&cwq->lock);
330         }
331 }
332
333 /**
334  * flush_workqueue - ensure that any scheduled work has run to completion.
335  * @wq: workqueue to flush
336  *
337  * Forces execution of the workqueue and blocks until its completion.
338  * This is typically used in driver shutdown handlers.
339  *
340  * This function will sample each workqueue's current insert_sequence number and
341  * will sleep until the head sequence is greater than or equal to that.  This
342  * means that we sleep until all works which were queued on entry have been
343  * handled, but we are not livelocked by new incoming ones.
344  *
345  * This function used to run the workqueues itself.  Now we just wait for the
346  * helper threads to do it.
347  */
348 void fastcall flush_workqueue(struct workqueue_struct *wq)
349 {
350         might_sleep();
351
352         if (is_single_threaded(wq)) {
353                 /* Always use first cpu's area. */
354                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu));
355         } else {
356                 int cpu;
357
358                 mutex_lock(&workqueue_mutex);
359                 for_each_online_cpu(cpu)
360                         flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
361                 mutex_unlock(&workqueue_mutex);
362         }
363 }
364 EXPORT_SYMBOL_GPL(flush_workqueue);
365
366 static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
367                                                    int cpu)
368 {
369         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
370         struct task_struct *p;
371
372         spin_lock_init(&cwq->lock);
373         cwq->wq = wq;
374         cwq->thread = NULL;
375         cwq->insert_sequence = 0;
376         cwq->remove_sequence = 0;
377         INIT_LIST_HEAD(&cwq->worklist);
378         init_waitqueue_head(&cwq->more_work);
379         init_waitqueue_head(&cwq->work_done);
380
381         if (is_single_threaded(wq))
382                 p = kthread_create(worker_thread, cwq, "%s", wq->name);
383         else
384                 p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
385         if (IS_ERR(p))
386                 return NULL;
387         cwq->thread = p;
388         return p;
389 }
390
391 struct workqueue_struct *__create_workqueue(const char *name,
392                                             int singlethread)
393 {
394         int cpu, destroy = 0;
395         struct workqueue_struct *wq;
396         struct task_struct *p;
397
398         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
399         if (!wq)
400                 return NULL;
401
402         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
403         if (!wq->cpu_wq) {
404                 kfree(wq);
405                 return NULL;
406         }
407
408         wq->name = name;
409         mutex_lock(&workqueue_mutex);
410         if (singlethread) {
411                 INIT_LIST_HEAD(&wq->list);
412                 p = create_workqueue_thread(wq, singlethread_cpu);
413                 if (!p)
414                         destroy = 1;
415                 else
416                         wake_up_process(p);
417         } else {
418                 list_add(&wq->list, &workqueues);
419                 for_each_online_cpu(cpu) {
420                         p = create_workqueue_thread(wq, cpu);
421                         if (p) {
422                                 kthread_bind(p, cpu);
423                                 wake_up_process(p);
424                         } else
425                                 destroy = 1;
426                 }
427         }
428         mutex_unlock(&workqueue_mutex);
429
430         /*
431          * Was there any error during startup? If yes then clean up:
432          */
433         if (destroy) {
434                 destroy_workqueue(wq);
435                 wq = NULL;
436         }
437         return wq;
438 }
439 EXPORT_SYMBOL_GPL(__create_workqueue);
440
441 static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
442 {
443         struct cpu_workqueue_struct *cwq;
444         unsigned long flags;
445         struct task_struct *p;
446
447         cwq = per_cpu_ptr(wq->cpu_wq, cpu);
448         spin_lock_irqsave(&cwq->lock, flags);
449         p = cwq->thread;
450         cwq->thread = NULL;
451         spin_unlock_irqrestore(&cwq->lock, flags);
452         if (p)
453                 kthread_stop(p);
454 }
455
456 /**
457  * destroy_workqueue - safely terminate a workqueue
458  * @wq: target workqueue
459  *
460  * Safely destroy a workqueue. All work currently pending will be done first.
461  */
462 void destroy_workqueue(struct workqueue_struct *wq)
463 {
464         int cpu;
465
466         flush_workqueue(wq);
467
468         /* We don't need the distraction of CPUs appearing and vanishing. */
469         mutex_lock(&workqueue_mutex);
470         if (is_single_threaded(wq))
471                 cleanup_workqueue_thread(wq, singlethread_cpu);
472         else {
473                 for_each_online_cpu(cpu)
474                         cleanup_workqueue_thread(wq, cpu);
475                 list_del(&wq->list);
476         }
477         mutex_unlock(&workqueue_mutex);
478         free_percpu(wq->cpu_wq);
479         kfree(wq);
480 }
481 EXPORT_SYMBOL_GPL(destroy_workqueue);
482
483 static struct workqueue_struct *keventd_wq;
484
485 /**
486  * schedule_work - put work task in global workqueue
487  * @work: job to be done
488  *
489  * This puts a job in the kernel-global workqueue.
490  */
491 int fastcall schedule_work(struct work_struct *work)
492 {
493         return queue_work(keventd_wq, work);
494 }
495 EXPORT_SYMBOL(schedule_work);
496
497 /**
498  * schedule_delayed_work - put work task in global workqueue after delay
499  * @dwork: job to be done
500  * @delay: number of jiffies to wait or 0 for immediate execution
501  *
502  * After waiting for a given time this puts a job in the kernel-global
503  * workqueue.
504  */
505 int fastcall schedule_delayed_work(struct delayed_work *dwork, unsigned long delay)
506 {
507         return queue_delayed_work(keventd_wq, dwork, delay);
508 }
509 EXPORT_SYMBOL(schedule_delayed_work);
510
511 /**
512  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
513  * @cpu: cpu to use
514  * @dwork: job to be done
515  * @delay: number of jiffies to wait
516  *
517  * After waiting for a given time this puts a job in the kernel-global
518  * workqueue on the specified CPU.
519  */
520 int schedule_delayed_work_on(int cpu,
521                         struct delayed_work *dwork, unsigned long delay)
522 {
523         return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
524 }
525 EXPORT_SYMBOL(schedule_delayed_work_on);
526
527 /**
528  * schedule_on_each_cpu - call a function on each online CPU from keventd
529  * @func: the function to call
530  * @info: a pointer to pass to func()
531  *
532  * Returns zero on success.
533  * Returns -ve errno on failure.
534  *
535  * Appears to be racy against CPU hotplug.
536  *
537  * schedule_on_each_cpu() is very slow.
538  */
539 int schedule_on_each_cpu(work_func_t func, void *info)
540 {
541         int cpu;
542         struct work_struct *works;
543
544         works = alloc_percpu(struct work_struct);
545         if (!works)
546                 return -ENOMEM;
547
548         mutex_lock(&workqueue_mutex);
549         for_each_online_cpu(cpu) {
550                 INIT_WORK(per_cpu_ptr(works, cpu), func, info);
551                 __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),
552                                 per_cpu_ptr(works, cpu));
553         }
554         mutex_unlock(&workqueue_mutex);
555         flush_workqueue(keventd_wq);
556         free_percpu(works);
557         return 0;
558 }
559
560 void flush_scheduled_work(void)
561 {
562         flush_workqueue(keventd_wq);
563 }
564 EXPORT_SYMBOL(flush_scheduled_work);
565
566 /**
567  * cancel_rearming_delayed_workqueue - reliably kill off a delayed
568  *                      work whose handler rearms the delayed work.
569  * @wq:   the controlling workqueue structure
570  * @dwork: the delayed work struct
571  */
572 void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
573                                        struct delayed_work *dwork)
574 {
575         while (!cancel_delayed_work(dwork))
576                 flush_workqueue(wq);
577 }
578 EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
579
580 /**
581  * cancel_rearming_delayed_work - reliably kill off a delayed keventd
582  *                      work whose handler rearms the delayed work.
583  * @dwork: the delayed work struct
584  */
585 void cancel_rearming_delayed_work(struct delayed_work *dwork)
586 {
587         cancel_rearming_delayed_workqueue(keventd_wq, dwork);
588 }
589 EXPORT_SYMBOL(cancel_rearming_delayed_work);
590
591 /**
592  * execute_in_process_context - reliably execute the routine with user context
593  * @fn:         the function to execute
594  * @data:       data to pass to the function
595  * @ew:         guaranteed storage for the execute work structure (must
596  *              be available when the work executes)
597  *
598  * Executes the function immediately if process context is available,
599  * otherwise schedules the function for delayed execution.
600  *
601  * Returns:     0 - function was executed
602  *              1 - function was scheduled for execution
603  */
604 int execute_in_process_context(work_func_t fn, void *data,
605                                struct execute_work *ew)
606 {
607         if (!in_interrupt()) {
608                 fn(data);
609                 return 0;
610         }
611
612         INIT_WORK(&ew->work, fn, data);
613         schedule_work(&ew->work);
614
615         return 1;
616 }
617 EXPORT_SYMBOL_GPL(execute_in_process_context);
618
619 int keventd_up(void)
620 {
621         return keventd_wq != NULL;
622 }
623
624 int current_is_keventd(void)
625 {
626         struct cpu_workqueue_struct *cwq;
627         int cpu = smp_processor_id();   /* preempt-safe: keventd is per-cpu */
628         int ret = 0;
629
630         BUG_ON(!keventd_wq);
631
632         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
633         if (current == cwq->thread)
634                 ret = 1;
635
636         return ret;
637
638 }
639
640 #ifdef CONFIG_HOTPLUG_CPU
641 /* Take the work from this (downed) CPU. */
642 static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
643 {
644         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
645         struct list_head list;
646         struct work_struct *work;
647
648         spin_lock_irq(&cwq->lock);
649         list_replace_init(&cwq->worklist, &list);
650
651         while (!list_empty(&list)) {
652                 printk("Taking work for %s\n", wq->name);
653                 work = list_entry(list.next,struct work_struct,entry);
654                 list_del(&work->entry);
655                 __queue_work(per_cpu_ptr(wq->cpu_wq, smp_processor_id()), work);
656         }
657         spin_unlock_irq(&cwq->lock);
658 }
659
660 /* We're holding the cpucontrol mutex here */
661 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
662                                   unsigned long action,
663                                   void *hcpu)
664 {
665         unsigned int hotcpu = (unsigned long)hcpu;
666         struct workqueue_struct *wq;
667
668         switch (action) {
669         case CPU_UP_PREPARE:
670                 mutex_lock(&workqueue_mutex);
671                 /* Create a new workqueue thread for it. */
672                 list_for_each_entry(wq, &workqueues, list) {
673                         if (!create_workqueue_thread(wq, hotcpu)) {
674                                 printk("workqueue for %i failed\n", hotcpu);
675                                 return NOTIFY_BAD;
676                         }
677                 }
678                 break;
679
680         case CPU_ONLINE:
681                 /* Kick off worker threads. */
682                 list_for_each_entry(wq, &workqueues, list) {
683                         struct cpu_workqueue_struct *cwq;
684
685                         cwq = per_cpu_ptr(wq->cpu_wq, hotcpu);
686                         kthread_bind(cwq->thread, hotcpu);
687                         wake_up_process(cwq->thread);
688                 }
689                 mutex_unlock(&workqueue_mutex);
690                 break;
691
692         case CPU_UP_CANCELED:
693                 list_for_each_entry(wq, &workqueues, list) {
694                         if (!per_cpu_ptr(wq->cpu_wq, hotcpu)->thread)
695                                 continue;
696                         /* Unbind so it can run. */
697                         kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,
698                                      any_online_cpu(cpu_online_map));
699                         cleanup_workqueue_thread(wq, hotcpu);
700                 }
701                 mutex_unlock(&workqueue_mutex);
702                 break;
703
704         case CPU_DOWN_PREPARE:
705                 mutex_lock(&workqueue_mutex);
706                 break;
707
708         case CPU_DOWN_FAILED:
709                 mutex_unlock(&workqueue_mutex);
710                 break;
711
712         case CPU_DEAD:
713                 list_for_each_entry(wq, &workqueues, list)
714                         cleanup_workqueue_thread(wq, hotcpu);
715                 list_for_each_entry(wq, &workqueues, list)
716                         take_over_work(wq, hotcpu);
717                 mutex_unlock(&workqueue_mutex);
718                 break;
719         }
720
721         return NOTIFY_OK;
722 }
723 #endif
724
725 void init_workqueues(void)
726 {
727         singlethread_cpu = first_cpu(cpu_possible_map);
728         hotcpu_notifier(workqueue_cpu_callback, 0);
729         keventd_wq = create_workqueue("events");
730         BUG_ON(!keventd_wq);
731 }
732