[PATCH] hotplug CPU: clean up hotcpu_notifier() use
[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 #include <linux/freezer.h>
33 #include <linux/kallsyms.h>
34 #include <linux/debug_locks.h>
35
36 /*
37  * The per-CPU workqueue (if single thread, we always use the first
38  * possible cpu).
39  *
40  * The sequence counters are for flush_scheduled_work().  It wants to wait
41  * until all currently-scheduled works are completed, but it doesn't
42  * want to be livelocked by new, incoming ones.  So it waits until
43  * remove_sequence is >= the insert_sequence which pertained when
44  * flush_scheduled_work() was called.
45  */
46 struct cpu_workqueue_struct {
47
48         spinlock_t lock;
49
50         long remove_sequence;   /* Least-recently added (next to run) */
51         long insert_sequence;   /* Next to add */
52
53         struct list_head worklist;
54         wait_queue_head_t more_work;
55         wait_queue_head_t work_done;
56
57         struct workqueue_struct *wq;
58         struct task_struct *thread;
59
60         int run_depth;          /* Detect run_workqueue() recursion depth */
61
62         int freezeable;         /* Freeze the thread during suspend */
63 } ____cacheline_aligned;
64
65 /*
66  * The externally visible workqueue abstraction is an array of
67  * per-CPU workqueues:
68  */
69 struct workqueue_struct {
70         struct cpu_workqueue_struct *cpu_wq;
71         const char *name;
72         struct list_head list;  /* Empty if single thread */
73 };
74
75 /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
76    threads to each one as cpus come/go. */
77 static DEFINE_MUTEX(workqueue_mutex);
78 static LIST_HEAD(workqueues);
79
80 static int singlethread_cpu;
81
82 /* If it's single threaded, it isn't in the list of workqueues. */
83 static inline int is_single_threaded(struct workqueue_struct *wq)
84 {
85         return list_empty(&wq->list);
86 }
87
88 static inline void set_wq_data(struct work_struct *work, void *wq)
89 {
90         unsigned long new, old, res;
91
92         /* assume the pending flag is already set and that the task has already
93          * been queued on this workqueue */
94         new = (unsigned long) wq | (1UL << WORK_STRUCT_PENDING);
95         res = work->management;
96         if (res != new) {
97                 do {
98                         old = res;
99                         new = (unsigned long) wq;
100                         new |= (old & WORK_STRUCT_FLAG_MASK);
101                         res = cmpxchg(&work->management, old, new);
102                 } while (res != old);
103         }
104 }
105
106 static inline void *get_wq_data(struct work_struct *work)
107 {
108         return (void *) (work->management & WORK_STRUCT_WQ_DATA_MASK);
109 }
110
111 /* Preempt must be disabled. */
112 static void __queue_work(struct cpu_workqueue_struct *cwq,
113                          struct work_struct *work)
114 {
115         unsigned long flags;
116
117         spin_lock_irqsave(&cwq->lock, flags);
118         set_wq_data(work, cwq);
119         list_add_tail(&work->entry, &cwq->worklist);
120         cwq->insert_sequence++;
121         wake_up(&cwq->more_work);
122         spin_unlock_irqrestore(&cwq->lock, flags);
123 }
124
125 /**
126  * queue_work - queue work on a workqueue
127  * @wq: workqueue to use
128  * @work: work to queue
129  *
130  * Returns 0 if @work was already on a queue, non-zero otherwise.
131  *
132  * We queue the work to the CPU it was submitted, but there is no
133  * guarantee that it will be processed by that CPU.
134  */
135 int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
136 {
137         int ret = 0, cpu = get_cpu();
138
139         if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
140                 if (unlikely(is_single_threaded(wq)))
141                         cpu = singlethread_cpu;
142                 BUG_ON(!list_empty(&work->entry));
143                 __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
144                 ret = 1;
145         }
146         put_cpu();
147         return ret;
148 }
149 EXPORT_SYMBOL_GPL(queue_work);
150
151 static void delayed_work_timer_fn(unsigned long __data)
152 {
153         struct delayed_work *dwork = (struct delayed_work *)__data;
154         struct workqueue_struct *wq = get_wq_data(&dwork->work);
155         int cpu = smp_processor_id();
156
157         if (unlikely(is_single_threaded(wq)))
158                 cpu = singlethread_cpu;
159
160         __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), &dwork->work);
161 }
162
163 /**
164  * queue_delayed_work - queue work on a workqueue after delay
165  * @wq: workqueue to use
166  * @work: delayable work to queue
167  * @delay: number of jiffies to wait before queueing
168  *
169  * Returns 0 if @work was already on a queue, non-zero otherwise.
170  */
171 int fastcall queue_delayed_work(struct workqueue_struct *wq,
172                         struct delayed_work *dwork, unsigned long delay)
173 {
174         int ret = 0;
175         struct timer_list *timer = &dwork->timer;
176         struct work_struct *work = &dwork->work;
177
178         if (delay == 0)
179                 return queue_work(wq, work);
180
181         if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
182                 BUG_ON(timer_pending(timer));
183                 BUG_ON(!list_empty(&work->entry));
184
185                 /* This stores wq for the moment, for the timer_fn */
186                 set_wq_data(work, wq);
187                 timer->expires = jiffies + delay;
188                 timer->data = (unsigned long)dwork;
189                 timer->function = delayed_work_timer_fn;
190                 add_timer(timer);
191                 ret = 1;
192         }
193         return ret;
194 }
195 EXPORT_SYMBOL_GPL(queue_delayed_work);
196
197 /**
198  * queue_delayed_work_on - queue work on specific CPU after delay
199  * @cpu: CPU number to execute work on
200  * @wq: workqueue to use
201  * @work: work to queue
202  * @delay: number of jiffies to wait before queueing
203  *
204  * Returns 0 if @work was already on a queue, non-zero otherwise.
205  */
206 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
207                         struct delayed_work *dwork, unsigned long delay)
208 {
209         int ret = 0;
210         struct timer_list *timer = &dwork->timer;
211         struct work_struct *work = &dwork->work;
212
213         if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
214                 BUG_ON(timer_pending(timer));
215                 BUG_ON(!list_empty(&work->entry));
216
217                 /* This stores wq for the moment, for the timer_fn */
218                 set_wq_data(work, wq);
219                 timer->expires = jiffies + delay;
220                 timer->data = (unsigned long)dwork;
221                 timer->function = delayed_work_timer_fn;
222                 add_timer_on(timer, cpu);
223                 ret = 1;
224         }
225         return ret;
226 }
227 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
228
229 static void run_workqueue(struct cpu_workqueue_struct *cwq)
230 {
231         unsigned long flags;
232
233         /*
234          * Keep taking off work from the queue until
235          * done.
236          */
237         spin_lock_irqsave(&cwq->lock, flags);
238         cwq->run_depth++;
239         if (cwq->run_depth > 3) {
240                 /* morton gets to eat his hat */
241                 printk("%s: recursion depth exceeded: %d\n",
242                         __FUNCTION__, cwq->run_depth);
243                 dump_stack();
244         }
245         while (!list_empty(&cwq->worklist)) {
246                 struct work_struct *work = list_entry(cwq->worklist.next,
247                                                 struct work_struct, entry);
248                 work_func_t f = work->func;
249
250                 list_del_init(cwq->worklist.next);
251                 spin_unlock_irqrestore(&cwq->lock, flags);
252
253                 BUG_ON(get_wq_data(work) != cwq);
254                 if (!test_bit(WORK_STRUCT_NOAUTOREL, &work->management))
255                         work_release(work);
256                 f(work);
257
258                 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
259                         printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
260                                         "%s/0x%08x/%d\n",
261                                         current->comm, preempt_count(),
262                                         current->pid);
263                         printk(KERN_ERR "    last function: ");
264                         print_symbol("%s\n", (unsigned long)f);
265                         debug_show_held_locks(current);
266                         dump_stack();
267                 }
268
269                 spin_lock_irqsave(&cwq->lock, flags);
270                 cwq->remove_sequence++;
271                 wake_up(&cwq->work_done);
272         }
273         cwq->run_depth--;
274         spin_unlock_irqrestore(&cwq->lock, flags);
275 }
276
277 static int worker_thread(void *__cwq)
278 {
279         struct cpu_workqueue_struct *cwq = __cwq;
280         DECLARE_WAITQUEUE(wait, current);
281         struct k_sigaction sa;
282         sigset_t blocked;
283
284         if (!cwq->freezeable)
285                 current->flags |= PF_NOFREEZE;
286
287         set_user_nice(current, -5);
288
289         /* Block and flush all signals */
290         sigfillset(&blocked);
291         sigprocmask(SIG_BLOCK, &blocked, NULL);
292         flush_signals(current);
293
294         /*
295          * We inherited MPOL_INTERLEAVE from the booting kernel.
296          * Set MPOL_DEFAULT to insure node local allocations.
297          */
298         numa_default_policy();
299
300         /* SIG_IGN makes children autoreap: see do_notify_parent(). */
301         sa.sa.sa_handler = SIG_IGN;
302         sa.sa.sa_flags = 0;
303         siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
304         do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
305
306         set_current_state(TASK_INTERRUPTIBLE);
307         while (!kthread_should_stop()) {
308                 if (cwq->freezeable)
309                         try_to_freeze();
310
311                 add_wait_queue(&cwq->more_work, &wait);
312                 if (list_empty(&cwq->worklist))
313                         schedule();
314                 else
315                         __set_current_state(TASK_RUNNING);
316                 remove_wait_queue(&cwq->more_work, &wait);
317
318                 if (!list_empty(&cwq->worklist))
319                         run_workqueue(cwq);
320                 set_current_state(TASK_INTERRUPTIBLE);
321         }
322         __set_current_state(TASK_RUNNING);
323         return 0;
324 }
325
326 static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
327 {
328         if (cwq->thread == current) {
329                 /*
330                  * Probably keventd trying to flush its own queue. So simply run
331                  * it by hand rather than deadlocking.
332                  */
333                 run_workqueue(cwq);
334         } else {
335                 DEFINE_WAIT(wait);
336                 long sequence_needed;
337
338                 spin_lock_irq(&cwq->lock);
339                 sequence_needed = cwq->insert_sequence;
340
341                 while (sequence_needed - cwq->remove_sequence > 0) {
342                         prepare_to_wait(&cwq->work_done, &wait,
343                                         TASK_UNINTERRUPTIBLE);
344                         spin_unlock_irq(&cwq->lock);
345                         schedule();
346                         spin_lock_irq(&cwq->lock);
347                 }
348                 finish_wait(&cwq->work_done, &wait);
349                 spin_unlock_irq(&cwq->lock);
350         }
351 }
352
353 /**
354  * flush_workqueue - ensure that any scheduled work has run to completion.
355  * @wq: workqueue to flush
356  *
357  * Forces execution of the workqueue and blocks until its completion.
358  * This is typically used in driver shutdown handlers.
359  *
360  * This function will sample each workqueue's current insert_sequence number and
361  * will sleep until the head sequence is greater than or equal to that.  This
362  * means that we sleep until all works which were queued on entry have been
363  * handled, but we are not livelocked by new incoming ones.
364  *
365  * This function used to run the workqueues itself.  Now we just wait for the
366  * helper threads to do it.
367  */
368 void fastcall flush_workqueue(struct workqueue_struct *wq)
369 {
370         might_sleep();
371
372         if (is_single_threaded(wq)) {
373                 /* Always use first cpu's area. */
374                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu));
375         } else {
376                 int cpu;
377
378                 mutex_lock(&workqueue_mutex);
379                 for_each_online_cpu(cpu)
380                         flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
381                 mutex_unlock(&workqueue_mutex);
382         }
383 }
384 EXPORT_SYMBOL_GPL(flush_workqueue);
385
386 static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
387                                                    int cpu, int freezeable)
388 {
389         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
390         struct task_struct *p;
391
392         spin_lock_init(&cwq->lock);
393         cwq->wq = wq;
394         cwq->thread = NULL;
395         cwq->insert_sequence = 0;
396         cwq->remove_sequence = 0;
397         cwq->freezeable = freezeable;
398         INIT_LIST_HEAD(&cwq->worklist);
399         init_waitqueue_head(&cwq->more_work);
400         init_waitqueue_head(&cwq->work_done);
401
402         if (is_single_threaded(wq))
403                 p = kthread_create(worker_thread, cwq, "%s", wq->name);
404         else
405                 p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
406         if (IS_ERR(p))
407                 return NULL;
408         cwq->thread = p;
409         return p;
410 }
411
412 struct workqueue_struct *__create_workqueue(const char *name,
413                                             int singlethread, int freezeable)
414 {
415         int cpu, destroy = 0;
416         struct workqueue_struct *wq;
417         struct task_struct *p;
418
419         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
420         if (!wq)
421                 return NULL;
422
423         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
424         if (!wq->cpu_wq) {
425                 kfree(wq);
426                 return NULL;
427         }
428
429         wq->name = name;
430         mutex_lock(&workqueue_mutex);
431         if (singlethread) {
432                 INIT_LIST_HEAD(&wq->list);
433                 p = create_workqueue_thread(wq, singlethread_cpu, freezeable);
434                 if (!p)
435                         destroy = 1;
436                 else
437                         wake_up_process(p);
438         } else {
439                 list_add(&wq->list, &workqueues);
440                 for_each_online_cpu(cpu) {
441                         p = create_workqueue_thread(wq, cpu, freezeable);
442                         if (p) {
443                                 kthread_bind(p, cpu);
444                                 wake_up_process(p);
445                         } else
446                                 destroy = 1;
447                 }
448         }
449         mutex_unlock(&workqueue_mutex);
450
451         /*
452          * Was there any error during startup? If yes then clean up:
453          */
454         if (destroy) {
455                 destroy_workqueue(wq);
456                 wq = NULL;
457         }
458         return wq;
459 }
460 EXPORT_SYMBOL_GPL(__create_workqueue);
461
462 static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
463 {
464         struct cpu_workqueue_struct *cwq;
465         unsigned long flags;
466         struct task_struct *p;
467
468         cwq = per_cpu_ptr(wq->cpu_wq, cpu);
469         spin_lock_irqsave(&cwq->lock, flags);
470         p = cwq->thread;
471         cwq->thread = NULL;
472         spin_unlock_irqrestore(&cwq->lock, flags);
473         if (p)
474                 kthread_stop(p);
475 }
476
477 /**
478  * destroy_workqueue - safely terminate a workqueue
479  * @wq: target workqueue
480  *
481  * Safely destroy a workqueue. All work currently pending will be done first.
482  */
483 void destroy_workqueue(struct workqueue_struct *wq)
484 {
485         int cpu;
486
487         flush_workqueue(wq);
488
489         /* We don't need the distraction of CPUs appearing and vanishing. */
490         mutex_lock(&workqueue_mutex);
491         if (is_single_threaded(wq))
492                 cleanup_workqueue_thread(wq, singlethread_cpu);
493         else {
494                 for_each_online_cpu(cpu)
495                         cleanup_workqueue_thread(wq, cpu);
496                 list_del(&wq->list);
497         }
498         mutex_unlock(&workqueue_mutex);
499         free_percpu(wq->cpu_wq);
500         kfree(wq);
501 }
502 EXPORT_SYMBOL_GPL(destroy_workqueue);
503
504 static struct workqueue_struct *keventd_wq;
505
506 /**
507  * schedule_work - put work task in global workqueue
508  * @work: job to be done
509  *
510  * This puts a job in the kernel-global workqueue.
511  */
512 int fastcall schedule_work(struct work_struct *work)
513 {
514         return queue_work(keventd_wq, work);
515 }
516 EXPORT_SYMBOL(schedule_work);
517
518 /**
519  * schedule_delayed_work - put work task in global workqueue after delay
520  * @dwork: job to be done
521  * @delay: number of jiffies to wait or 0 for immediate execution
522  *
523  * After waiting for a given time this puts a job in the kernel-global
524  * workqueue.
525  */
526 int fastcall schedule_delayed_work(struct delayed_work *dwork, unsigned long delay)
527 {
528         return queue_delayed_work(keventd_wq, dwork, delay);
529 }
530 EXPORT_SYMBOL(schedule_delayed_work);
531
532 /**
533  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
534  * @cpu: cpu to use
535  * @dwork: job to be done
536  * @delay: number of jiffies to wait
537  *
538  * After waiting for a given time this puts a job in the kernel-global
539  * workqueue on the specified CPU.
540  */
541 int schedule_delayed_work_on(int cpu,
542                         struct delayed_work *dwork, unsigned long delay)
543 {
544         return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
545 }
546 EXPORT_SYMBOL(schedule_delayed_work_on);
547
548 /**
549  * schedule_on_each_cpu - call a function on each online CPU from keventd
550  * @func: the function to call
551  *
552  * Returns zero on success.
553  * Returns -ve errno on failure.
554  *
555  * Appears to be racy against CPU hotplug.
556  *
557  * schedule_on_each_cpu() is very slow.
558  */
559 int schedule_on_each_cpu(work_func_t func)
560 {
561         int cpu;
562         struct work_struct *works;
563
564         works = alloc_percpu(struct work_struct);
565         if (!works)
566                 return -ENOMEM;
567
568         mutex_lock(&workqueue_mutex);
569         for_each_online_cpu(cpu) {
570                 INIT_WORK(per_cpu_ptr(works, cpu), func);
571                 __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),
572                                 per_cpu_ptr(works, cpu));
573         }
574         mutex_unlock(&workqueue_mutex);
575         flush_workqueue(keventd_wq);
576         free_percpu(works);
577         return 0;
578 }
579
580 void flush_scheduled_work(void)
581 {
582         flush_workqueue(keventd_wq);
583 }
584 EXPORT_SYMBOL(flush_scheduled_work);
585
586 /**
587  * cancel_rearming_delayed_workqueue - reliably kill off a delayed
588  *                      work whose handler rearms the delayed work.
589  * @wq:   the controlling workqueue structure
590  * @dwork: the delayed work struct
591  */
592 void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
593                                        struct delayed_work *dwork)
594 {
595         while (!cancel_delayed_work(dwork))
596                 flush_workqueue(wq);
597 }
598 EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
599
600 /**
601  * cancel_rearming_delayed_work - reliably kill off a delayed keventd
602  *                      work whose handler rearms the delayed work.
603  * @dwork: the delayed work struct
604  */
605 void cancel_rearming_delayed_work(struct delayed_work *dwork)
606 {
607         cancel_rearming_delayed_workqueue(keventd_wq, dwork);
608 }
609 EXPORT_SYMBOL(cancel_rearming_delayed_work);
610
611 /**
612  * execute_in_process_context - reliably execute the routine with user context
613  * @fn:         the function to execute
614  * @ew:         guaranteed storage for the execute work structure (must
615  *              be available when the work executes)
616  *
617  * Executes the function immediately if process context is available,
618  * otherwise schedules the function for delayed execution.
619  *
620  * Returns:     0 - function was executed
621  *              1 - function was scheduled for execution
622  */
623 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
624 {
625         if (!in_interrupt()) {
626                 fn(&ew->work);
627                 return 0;
628         }
629
630         INIT_WORK(&ew->work, fn);
631         schedule_work(&ew->work);
632
633         return 1;
634 }
635 EXPORT_SYMBOL_GPL(execute_in_process_context);
636
637 int keventd_up(void)
638 {
639         return keventd_wq != NULL;
640 }
641
642 int current_is_keventd(void)
643 {
644         struct cpu_workqueue_struct *cwq;
645         int cpu = smp_processor_id();   /* preempt-safe: keventd is per-cpu */
646         int ret = 0;
647
648         BUG_ON(!keventd_wq);
649
650         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
651         if (current == cwq->thread)
652                 ret = 1;
653
654         return ret;
655
656 }
657
658 /* Take the work from this (downed) CPU. */
659 static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
660 {
661         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
662         struct list_head list;
663         struct work_struct *work;
664
665         spin_lock_irq(&cwq->lock);
666         list_replace_init(&cwq->worklist, &list);
667
668         while (!list_empty(&list)) {
669                 printk("Taking work for %s\n", wq->name);
670                 work = list_entry(list.next,struct work_struct,entry);
671                 list_del(&work->entry);
672                 __queue_work(per_cpu_ptr(wq->cpu_wq, smp_processor_id()), work);
673         }
674         spin_unlock_irq(&cwq->lock);
675 }
676
677 /* We're holding the cpucontrol mutex here */
678 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
679                                   unsigned long action,
680                                   void *hcpu)
681 {
682         unsigned int hotcpu = (unsigned long)hcpu;
683         struct workqueue_struct *wq;
684
685         switch (action) {
686         case CPU_UP_PREPARE:
687                 mutex_lock(&workqueue_mutex);
688                 /* Create a new workqueue thread for it. */
689                 list_for_each_entry(wq, &workqueues, list) {
690                         if (!create_workqueue_thread(wq, hotcpu, 0)) {
691                                 printk("workqueue for %i failed\n", hotcpu);
692                                 return NOTIFY_BAD;
693                         }
694                 }
695                 break;
696
697         case CPU_ONLINE:
698                 /* Kick off worker threads. */
699                 list_for_each_entry(wq, &workqueues, list) {
700                         struct cpu_workqueue_struct *cwq;
701
702                         cwq = per_cpu_ptr(wq->cpu_wq, hotcpu);
703                         kthread_bind(cwq->thread, hotcpu);
704                         wake_up_process(cwq->thread);
705                 }
706                 mutex_unlock(&workqueue_mutex);
707                 break;
708
709         case CPU_UP_CANCELED:
710                 list_for_each_entry(wq, &workqueues, list) {
711                         if (!per_cpu_ptr(wq->cpu_wq, hotcpu)->thread)
712                                 continue;
713                         /* Unbind so it can run. */
714                         kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,
715                                      any_online_cpu(cpu_online_map));
716                         cleanup_workqueue_thread(wq, hotcpu);
717                 }
718                 mutex_unlock(&workqueue_mutex);
719                 break;
720
721         case CPU_DOWN_PREPARE:
722                 mutex_lock(&workqueue_mutex);
723                 break;
724
725         case CPU_DOWN_FAILED:
726                 mutex_unlock(&workqueue_mutex);
727                 break;
728
729         case CPU_DEAD:
730                 list_for_each_entry(wq, &workqueues, list)
731                         cleanup_workqueue_thread(wq, hotcpu);
732                 list_for_each_entry(wq, &workqueues, list)
733                         take_over_work(wq, hotcpu);
734                 mutex_unlock(&workqueue_mutex);
735                 break;
736         }
737
738         return NOTIFY_OK;
739 }
740
741 void init_workqueues(void)
742 {
743         singlethread_cpu = first_cpu(cpu_possible_map);
744         hotcpu_notifier(workqueue_cpu_callback, 0);
745         keventd_wq = create_workqueue("events");
746         BUG_ON(!keventd_wq);
747 }
748