[PATCH] fix kernel-doc warnings in 2.6.20-rc1
[sfrench/cifs-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 /*
89  * Set the workqueue on which a work item is to be run
90  * - Must *only* be called if the pending flag is set
91  */
92 static inline void set_wq_data(struct work_struct *work, void *wq)
93 {
94         unsigned long new;
95
96         BUG_ON(!work_pending(work));
97
98         new = (unsigned long) wq | (1UL << WORK_STRUCT_PENDING);
99         new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
100         atomic_long_set(&work->data, new);
101 }
102
103 static inline void *get_wq_data(struct work_struct *work)
104 {
105         return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);
106 }
107
108 static int __run_work(struct cpu_workqueue_struct *cwq, struct work_struct *work)
109 {
110         int ret = 0;
111         unsigned long flags;
112
113         spin_lock_irqsave(&cwq->lock, flags);
114         /*
115          * We need to re-validate the work info after we've gotten
116          * the cpu_workqueue lock. We can run the work now iff:
117          *
118          *  - the wq_data still matches the cpu_workqueue_struct
119          *  - AND the work is still marked pending
120          *  - AND the work is still on a list (which will be this
121          *    workqueue_struct list)
122          *
123          * All these conditions are important, because we
124          * need to protect against the work being run right
125          * now on another CPU (all but the last one might be
126          * true if it's currently running and has not been
127          * released yet, for example).
128          */
129         if (get_wq_data(work) == cwq
130             && work_pending(work)
131             && !list_empty(&work->entry)) {
132                 work_func_t f = work->func;
133                 list_del_init(&work->entry);
134                 spin_unlock_irqrestore(&cwq->lock, flags);
135
136                 if (!test_bit(WORK_STRUCT_NOAUTOREL, work_data_bits(work)))
137                         work_release(work);
138                 f(work);
139
140                 spin_lock_irqsave(&cwq->lock, flags);
141                 cwq->remove_sequence++;
142                 wake_up(&cwq->work_done);
143                 ret = 1;
144         }
145         spin_unlock_irqrestore(&cwq->lock, flags);
146         return ret;
147 }
148
149 /**
150  * run_scheduled_work - run scheduled work synchronously
151  * @work: work to run
152  *
153  * This checks if the work was pending, and runs it
154  * synchronously if so. It returns a boolean to indicate
155  * whether it had any scheduled work to run or not.
156  *
157  * NOTE! This _only_ works for normal work_structs. You
158  * CANNOT use this for delayed work, because the wq data
159  * for delayed work will not point properly to the per-
160  * CPU workqueue struct, but will change!
161  */
162 int fastcall run_scheduled_work(struct work_struct *work)
163 {
164         for (;;) {
165                 struct cpu_workqueue_struct *cwq;
166
167                 if (!work_pending(work))
168                         return 0;
169                 if (list_empty(&work->entry))
170                         return 0;
171                 /* NOTE! This depends intimately on __queue_work! */
172                 cwq = get_wq_data(work);
173                 if (!cwq)
174                         return 0;
175                 if (__run_work(cwq, work))
176                         return 1;
177         }
178 }
179 EXPORT_SYMBOL(run_scheduled_work);
180
181 /* Preempt must be disabled. */
182 static void __queue_work(struct cpu_workqueue_struct *cwq,
183                          struct work_struct *work)
184 {
185         unsigned long flags;
186
187         spin_lock_irqsave(&cwq->lock, flags);
188         set_wq_data(work, cwq);
189         list_add_tail(&work->entry, &cwq->worklist);
190         cwq->insert_sequence++;
191         wake_up(&cwq->more_work);
192         spin_unlock_irqrestore(&cwq->lock, flags);
193 }
194
195 /**
196  * queue_work - queue work on a workqueue
197  * @wq: workqueue to use
198  * @work: work to queue
199  *
200  * Returns 0 if @work was already on a queue, non-zero otherwise.
201  *
202  * We queue the work to the CPU it was submitted, but there is no
203  * guarantee that it will be processed by that CPU.
204  */
205 int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
206 {
207         int ret = 0, cpu = get_cpu();
208
209         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
210                 if (unlikely(is_single_threaded(wq)))
211                         cpu = singlethread_cpu;
212                 BUG_ON(!list_empty(&work->entry));
213                 __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
214                 ret = 1;
215         }
216         put_cpu();
217         return ret;
218 }
219 EXPORT_SYMBOL_GPL(queue_work);
220
221 static void delayed_work_timer_fn(unsigned long __data)
222 {
223         struct delayed_work *dwork = (struct delayed_work *)__data;
224         struct workqueue_struct *wq = get_wq_data(&dwork->work);
225         int cpu = smp_processor_id();
226
227         if (unlikely(is_single_threaded(wq)))
228                 cpu = singlethread_cpu;
229
230         __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), &dwork->work);
231 }
232
233 /**
234  * queue_delayed_work - queue work on a workqueue after delay
235  * @wq: workqueue to use
236  * @dwork: delayable work to queue
237  * @delay: number of jiffies to wait before queueing
238  *
239  * Returns 0 if @work was already on a queue, non-zero otherwise.
240  */
241 int fastcall queue_delayed_work(struct workqueue_struct *wq,
242                         struct delayed_work *dwork, unsigned long delay)
243 {
244         int ret = 0;
245         struct timer_list *timer = &dwork->timer;
246         struct work_struct *work = &dwork->work;
247
248         if (delay == 0)
249                 return queue_work(wq, work);
250
251         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
252                 BUG_ON(timer_pending(timer));
253                 BUG_ON(!list_empty(&work->entry));
254
255                 /* This stores wq for the moment, for the timer_fn */
256                 set_wq_data(work, wq);
257                 timer->expires = jiffies + delay;
258                 timer->data = (unsigned long)dwork;
259                 timer->function = delayed_work_timer_fn;
260                 add_timer(timer);
261                 ret = 1;
262         }
263         return ret;
264 }
265 EXPORT_SYMBOL_GPL(queue_delayed_work);
266
267 /**
268  * queue_delayed_work_on - queue work on specific CPU after delay
269  * @cpu: CPU number to execute work on
270  * @wq: workqueue to use
271  * @dwork: work to queue
272  * @delay: number of jiffies to wait before queueing
273  *
274  * Returns 0 if @work was already on a queue, non-zero otherwise.
275  */
276 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
277                         struct delayed_work *dwork, unsigned long delay)
278 {
279         int ret = 0;
280         struct timer_list *timer = &dwork->timer;
281         struct work_struct *work = &dwork->work;
282
283         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
284                 BUG_ON(timer_pending(timer));
285                 BUG_ON(!list_empty(&work->entry));
286
287                 /* This stores wq for the moment, for the timer_fn */
288                 set_wq_data(work, wq);
289                 timer->expires = jiffies + delay;
290                 timer->data = (unsigned long)dwork;
291                 timer->function = delayed_work_timer_fn;
292                 add_timer_on(timer, cpu);
293                 ret = 1;
294         }
295         return ret;
296 }
297 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
298
299 static void run_workqueue(struct cpu_workqueue_struct *cwq)
300 {
301         unsigned long flags;
302
303         /*
304          * Keep taking off work from the queue until
305          * done.
306          */
307         spin_lock_irqsave(&cwq->lock, flags);
308         cwq->run_depth++;
309         if (cwq->run_depth > 3) {
310                 /* morton gets to eat his hat */
311                 printk("%s: recursion depth exceeded: %d\n",
312                         __FUNCTION__, cwq->run_depth);
313                 dump_stack();
314         }
315         while (!list_empty(&cwq->worklist)) {
316                 struct work_struct *work = list_entry(cwq->worklist.next,
317                                                 struct work_struct, entry);
318                 work_func_t f = work->func;
319
320                 list_del_init(cwq->worklist.next);
321                 spin_unlock_irqrestore(&cwq->lock, flags);
322
323                 BUG_ON(get_wq_data(work) != cwq);
324                 if (!test_bit(WORK_STRUCT_NOAUTOREL, work_data_bits(work)))
325                         work_release(work);
326                 f(work);
327
328                 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
329                         printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
330                                         "%s/0x%08x/%d\n",
331                                         current->comm, preempt_count(),
332                                         current->pid);
333                         printk(KERN_ERR "    last function: ");
334                         print_symbol("%s\n", (unsigned long)f);
335                         debug_show_held_locks(current);
336                         dump_stack();
337                 }
338
339                 spin_lock_irqsave(&cwq->lock, flags);
340                 cwq->remove_sequence++;
341                 wake_up(&cwq->work_done);
342         }
343         cwq->run_depth--;
344         spin_unlock_irqrestore(&cwq->lock, flags);
345 }
346
347 static int worker_thread(void *__cwq)
348 {
349         struct cpu_workqueue_struct *cwq = __cwq;
350         DECLARE_WAITQUEUE(wait, current);
351         struct k_sigaction sa;
352         sigset_t blocked;
353
354         if (!cwq->freezeable)
355                 current->flags |= PF_NOFREEZE;
356
357         set_user_nice(current, -5);
358
359         /* Block and flush all signals */
360         sigfillset(&blocked);
361         sigprocmask(SIG_BLOCK, &blocked, NULL);
362         flush_signals(current);
363
364         /*
365          * We inherited MPOL_INTERLEAVE from the booting kernel.
366          * Set MPOL_DEFAULT to insure node local allocations.
367          */
368         numa_default_policy();
369
370         /* SIG_IGN makes children autoreap: see do_notify_parent(). */
371         sa.sa.sa_handler = SIG_IGN;
372         sa.sa.sa_flags = 0;
373         siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
374         do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
375
376         set_current_state(TASK_INTERRUPTIBLE);
377         while (!kthread_should_stop()) {
378                 if (cwq->freezeable)
379                         try_to_freeze();
380
381                 add_wait_queue(&cwq->more_work, &wait);
382                 if (list_empty(&cwq->worklist))
383                         schedule();
384                 else
385                         __set_current_state(TASK_RUNNING);
386                 remove_wait_queue(&cwq->more_work, &wait);
387
388                 if (!list_empty(&cwq->worklist))
389                         run_workqueue(cwq);
390                 set_current_state(TASK_INTERRUPTIBLE);
391         }
392         __set_current_state(TASK_RUNNING);
393         return 0;
394 }
395
396 static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
397 {
398         if (cwq->thread == current) {
399                 /*
400                  * Probably keventd trying to flush its own queue. So simply run
401                  * it by hand rather than deadlocking.
402                  */
403                 run_workqueue(cwq);
404         } else {
405                 DEFINE_WAIT(wait);
406                 long sequence_needed;
407
408                 spin_lock_irq(&cwq->lock);
409                 sequence_needed = cwq->insert_sequence;
410
411                 while (sequence_needed - cwq->remove_sequence > 0) {
412                         prepare_to_wait(&cwq->work_done, &wait,
413                                         TASK_UNINTERRUPTIBLE);
414                         spin_unlock_irq(&cwq->lock);
415                         schedule();
416                         spin_lock_irq(&cwq->lock);
417                 }
418                 finish_wait(&cwq->work_done, &wait);
419                 spin_unlock_irq(&cwq->lock);
420         }
421 }
422
423 /**
424  * flush_workqueue - ensure that any scheduled work has run to completion.
425  * @wq: workqueue to flush
426  *
427  * Forces execution of the workqueue and blocks until its completion.
428  * This is typically used in driver shutdown handlers.
429  *
430  * This function will sample each workqueue's current insert_sequence number and
431  * will sleep until the head sequence is greater than or equal to that.  This
432  * means that we sleep until all works which were queued on entry have been
433  * handled, but we are not livelocked by new incoming ones.
434  *
435  * This function used to run the workqueues itself.  Now we just wait for the
436  * helper threads to do it.
437  */
438 void fastcall flush_workqueue(struct workqueue_struct *wq)
439 {
440         might_sleep();
441
442         if (is_single_threaded(wq)) {
443                 /* Always use first cpu's area. */
444                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu));
445         } else {
446                 int cpu;
447
448                 mutex_lock(&workqueue_mutex);
449                 for_each_online_cpu(cpu)
450                         flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
451                 mutex_unlock(&workqueue_mutex);
452         }
453 }
454 EXPORT_SYMBOL_GPL(flush_workqueue);
455
456 static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
457                                                    int cpu, int freezeable)
458 {
459         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
460         struct task_struct *p;
461
462         spin_lock_init(&cwq->lock);
463         cwq->wq = wq;
464         cwq->thread = NULL;
465         cwq->insert_sequence = 0;
466         cwq->remove_sequence = 0;
467         cwq->freezeable = freezeable;
468         INIT_LIST_HEAD(&cwq->worklist);
469         init_waitqueue_head(&cwq->more_work);
470         init_waitqueue_head(&cwq->work_done);
471
472         if (is_single_threaded(wq))
473                 p = kthread_create(worker_thread, cwq, "%s", wq->name);
474         else
475                 p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
476         if (IS_ERR(p))
477                 return NULL;
478         cwq->thread = p;
479         return p;
480 }
481
482 struct workqueue_struct *__create_workqueue(const char *name,
483                                             int singlethread, int freezeable)
484 {
485         int cpu, destroy = 0;
486         struct workqueue_struct *wq;
487         struct task_struct *p;
488
489         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
490         if (!wq)
491                 return NULL;
492
493         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
494         if (!wq->cpu_wq) {
495                 kfree(wq);
496                 return NULL;
497         }
498
499         wq->name = name;
500         mutex_lock(&workqueue_mutex);
501         if (singlethread) {
502                 INIT_LIST_HEAD(&wq->list);
503                 p = create_workqueue_thread(wq, singlethread_cpu, freezeable);
504                 if (!p)
505                         destroy = 1;
506                 else
507                         wake_up_process(p);
508         } else {
509                 list_add(&wq->list, &workqueues);
510                 for_each_online_cpu(cpu) {
511                         p = create_workqueue_thread(wq, cpu, freezeable);
512                         if (p) {
513                                 kthread_bind(p, cpu);
514                                 wake_up_process(p);
515                         } else
516                                 destroy = 1;
517                 }
518         }
519         mutex_unlock(&workqueue_mutex);
520
521         /*
522          * Was there any error during startup? If yes then clean up:
523          */
524         if (destroy) {
525                 destroy_workqueue(wq);
526                 wq = NULL;
527         }
528         return wq;
529 }
530 EXPORT_SYMBOL_GPL(__create_workqueue);
531
532 static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
533 {
534         struct cpu_workqueue_struct *cwq;
535         unsigned long flags;
536         struct task_struct *p;
537
538         cwq = per_cpu_ptr(wq->cpu_wq, cpu);
539         spin_lock_irqsave(&cwq->lock, flags);
540         p = cwq->thread;
541         cwq->thread = NULL;
542         spin_unlock_irqrestore(&cwq->lock, flags);
543         if (p)
544                 kthread_stop(p);
545 }
546
547 /**
548  * destroy_workqueue - safely terminate a workqueue
549  * @wq: target workqueue
550  *
551  * Safely destroy a workqueue. All work currently pending will be done first.
552  */
553 void destroy_workqueue(struct workqueue_struct *wq)
554 {
555         int cpu;
556
557         flush_workqueue(wq);
558
559         /* We don't need the distraction of CPUs appearing and vanishing. */
560         mutex_lock(&workqueue_mutex);
561         if (is_single_threaded(wq))
562                 cleanup_workqueue_thread(wq, singlethread_cpu);
563         else {
564                 for_each_online_cpu(cpu)
565                         cleanup_workqueue_thread(wq, cpu);
566                 list_del(&wq->list);
567         }
568         mutex_unlock(&workqueue_mutex);
569         free_percpu(wq->cpu_wq);
570         kfree(wq);
571 }
572 EXPORT_SYMBOL_GPL(destroy_workqueue);
573
574 static struct workqueue_struct *keventd_wq;
575
576 /**
577  * schedule_work - put work task in global workqueue
578  * @work: job to be done
579  *
580  * This puts a job in the kernel-global workqueue.
581  */
582 int fastcall schedule_work(struct work_struct *work)
583 {
584         return queue_work(keventd_wq, work);
585 }
586 EXPORT_SYMBOL(schedule_work);
587
588 /**
589  * schedule_delayed_work - put work task in global workqueue after delay
590  * @dwork: job to be done
591  * @delay: number of jiffies to wait or 0 for immediate execution
592  *
593  * After waiting for a given time this puts a job in the kernel-global
594  * workqueue.
595  */
596 int fastcall schedule_delayed_work(struct delayed_work *dwork, unsigned long delay)
597 {
598         return queue_delayed_work(keventd_wq, dwork, delay);
599 }
600 EXPORT_SYMBOL(schedule_delayed_work);
601
602 /**
603  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
604  * @cpu: cpu to use
605  * @dwork: job to be done
606  * @delay: number of jiffies to wait
607  *
608  * After waiting for a given time this puts a job in the kernel-global
609  * workqueue on the specified CPU.
610  */
611 int schedule_delayed_work_on(int cpu,
612                         struct delayed_work *dwork, unsigned long delay)
613 {
614         return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
615 }
616 EXPORT_SYMBOL(schedule_delayed_work_on);
617
618 /**
619  * schedule_on_each_cpu - call a function on each online CPU from keventd
620  * @func: the function to call
621  *
622  * Returns zero on success.
623  * Returns -ve errno on failure.
624  *
625  * Appears to be racy against CPU hotplug.
626  *
627  * schedule_on_each_cpu() is very slow.
628  */
629 int schedule_on_each_cpu(work_func_t func)
630 {
631         int cpu;
632         struct work_struct *works;
633
634         works = alloc_percpu(struct work_struct);
635         if (!works)
636                 return -ENOMEM;
637
638         mutex_lock(&workqueue_mutex);
639         for_each_online_cpu(cpu) {
640                 struct work_struct *work = per_cpu_ptr(works, cpu);
641
642                 INIT_WORK(work, func);
643                 set_bit(WORK_STRUCT_PENDING, work_data_bits(work));
644                 __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu), work);
645         }
646         mutex_unlock(&workqueue_mutex);
647         flush_workqueue(keventd_wq);
648         free_percpu(works);
649         return 0;
650 }
651
652 void flush_scheduled_work(void)
653 {
654         flush_workqueue(keventd_wq);
655 }
656 EXPORT_SYMBOL(flush_scheduled_work);
657
658 /**
659  * cancel_rearming_delayed_workqueue - reliably kill off a delayed
660  *                      work whose handler rearms the delayed work.
661  * @wq:   the controlling workqueue structure
662  * @dwork: the delayed work struct
663  */
664 void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
665                                        struct delayed_work *dwork)
666 {
667         while (!cancel_delayed_work(dwork))
668                 flush_workqueue(wq);
669 }
670 EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
671
672 /**
673  * cancel_rearming_delayed_work - reliably kill off a delayed keventd
674  *                      work whose handler rearms the delayed work.
675  * @dwork: the delayed work struct
676  */
677 void cancel_rearming_delayed_work(struct delayed_work *dwork)
678 {
679         cancel_rearming_delayed_workqueue(keventd_wq, dwork);
680 }
681 EXPORT_SYMBOL(cancel_rearming_delayed_work);
682
683 /**
684  * execute_in_process_context - reliably execute the routine with user context
685  * @fn:         the function to execute
686  * @ew:         guaranteed storage for the execute work structure (must
687  *              be available when the work executes)
688  *
689  * Executes the function immediately if process context is available,
690  * otherwise schedules the function for delayed execution.
691  *
692  * Returns:     0 - function was executed
693  *              1 - function was scheduled for execution
694  */
695 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
696 {
697         if (!in_interrupt()) {
698                 fn(&ew->work);
699                 return 0;
700         }
701
702         INIT_WORK(&ew->work, fn);
703         schedule_work(&ew->work);
704
705         return 1;
706 }
707 EXPORT_SYMBOL_GPL(execute_in_process_context);
708
709 int keventd_up(void)
710 {
711         return keventd_wq != NULL;
712 }
713
714 int current_is_keventd(void)
715 {
716         struct cpu_workqueue_struct *cwq;
717         int cpu = smp_processor_id();   /* preempt-safe: keventd is per-cpu */
718         int ret = 0;
719
720         BUG_ON(!keventd_wq);
721
722         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
723         if (current == cwq->thread)
724                 ret = 1;
725
726         return ret;
727
728 }
729
730 /* Take the work from this (downed) CPU. */
731 static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
732 {
733         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
734         struct list_head list;
735         struct work_struct *work;
736
737         spin_lock_irq(&cwq->lock);
738         list_replace_init(&cwq->worklist, &list);
739
740         while (!list_empty(&list)) {
741                 printk("Taking work for %s\n", wq->name);
742                 work = list_entry(list.next,struct work_struct,entry);
743                 list_del(&work->entry);
744                 __queue_work(per_cpu_ptr(wq->cpu_wq, smp_processor_id()), work);
745         }
746         spin_unlock_irq(&cwq->lock);
747 }
748
749 /* We're holding the cpucontrol mutex here */
750 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
751                                   unsigned long action,
752                                   void *hcpu)
753 {
754         unsigned int hotcpu = (unsigned long)hcpu;
755         struct workqueue_struct *wq;
756
757         switch (action) {
758         case CPU_UP_PREPARE:
759                 mutex_lock(&workqueue_mutex);
760                 /* Create a new workqueue thread for it. */
761                 list_for_each_entry(wq, &workqueues, list) {
762                         if (!create_workqueue_thread(wq, hotcpu, 0)) {
763                                 printk("workqueue for %i failed\n", hotcpu);
764                                 return NOTIFY_BAD;
765                         }
766                 }
767                 break;
768
769         case CPU_ONLINE:
770                 /* Kick off worker threads. */
771                 list_for_each_entry(wq, &workqueues, list) {
772                         struct cpu_workqueue_struct *cwq;
773
774                         cwq = per_cpu_ptr(wq->cpu_wq, hotcpu);
775                         kthread_bind(cwq->thread, hotcpu);
776                         wake_up_process(cwq->thread);
777                 }
778                 mutex_unlock(&workqueue_mutex);
779                 break;
780
781         case CPU_UP_CANCELED:
782                 list_for_each_entry(wq, &workqueues, list) {
783                         if (!per_cpu_ptr(wq->cpu_wq, hotcpu)->thread)
784                                 continue;
785                         /* Unbind so it can run. */
786                         kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,
787                                      any_online_cpu(cpu_online_map));
788                         cleanup_workqueue_thread(wq, hotcpu);
789                 }
790                 mutex_unlock(&workqueue_mutex);
791                 break;
792
793         case CPU_DOWN_PREPARE:
794                 mutex_lock(&workqueue_mutex);
795                 break;
796
797         case CPU_DOWN_FAILED:
798                 mutex_unlock(&workqueue_mutex);
799                 break;
800
801         case CPU_DEAD:
802                 list_for_each_entry(wq, &workqueues, list)
803                         cleanup_workqueue_thread(wq, hotcpu);
804                 list_for_each_entry(wq, &workqueues, list)
805                         take_over_work(wq, hotcpu);
806                 mutex_unlock(&workqueue_mutex);
807                 break;
808         }
809
810         return NOTIFY_OK;
811 }
812
813 void init_workqueues(void)
814 {
815         singlethread_cpu = first_cpu(cpu_possible_map);
816         hotcpu_notifier(workqueue_cpu_callback, 0);
817         keventd_wq = create_workqueue("events");
818         BUG_ON(!keventd_wq);
819 }
820