[PATCH] rcu: Mention rcu_bh in description of rcutorture's torture_type parameter
[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
32 /*
33  * The per-CPU workqueue (if single thread, we always use the first
34  * possible cpu).
35  *
36  * The sequence counters are for flush_scheduled_work().  It wants to wait
37  * until all currently-scheduled works are completed, but it doesn't
38  * want to be livelocked by new, incoming ones.  So it waits until
39  * remove_sequence is >= the insert_sequence which pertained when
40  * flush_scheduled_work() was called.
41  */
42 struct cpu_workqueue_struct {
43
44         spinlock_t lock;
45
46         long remove_sequence;   /* Least-recently added (next to run) */
47         long insert_sequence;   /* Next to add */
48
49         struct list_head worklist;
50         wait_queue_head_t more_work;
51         wait_queue_head_t work_done;
52
53         struct workqueue_struct *wq;
54         struct task_struct *thread;
55
56         int run_depth;          /* Detect run_workqueue() recursion depth */
57 } ____cacheline_aligned;
58
59 /*
60  * The externally visible workqueue abstraction is an array of
61  * per-CPU workqueues:
62  */
63 struct workqueue_struct {
64         struct cpu_workqueue_struct *cpu_wq;
65         const char *name;
66         struct list_head list;  /* Empty if single thread */
67 };
68
69 /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
70    threads to each one as cpus come/go. */
71 static DEFINE_MUTEX(workqueue_mutex);
72 static LIST_HEAD(workqueues);
73
74 static int singlethread_cpu;
75
76 /* If it's single threaded, it isn't in the list of workqueues. */
77 static inline int is_single_threaded(struct workqueue_struct *wq)
78 {
79         return list_empty(&wq->list);
80 }
81
82 /* Preempt must be disabled. */
83 static void __queue_work(struct cpu_workqueue_struct *cwq,
84                          struct work_struct *work)
85 {
86         unsigned long flags;
87
88         spin_lock_irqsave(&cwq->lock, flags);
89         work->wq_data = cwq;
90         list_add_tail(&work->entry, &cwq->worklist);
91         cwq->insert_sequence++;
92         wake_up(&cwq->more_work);
93         spin_unlock_irqrestore(&cwq->lock, flags);
94 }
95
96 /**
97  * queue_work - queue work on a workqueue
98  * @wq: workqueue to use
99  * @work: work to queue
100  *
101  * Returns non-zero if it was successfully added.
102  *
103  * We queue the work to the CPU it was submitted, but there is no
104  * guarantee that it will be processed by that CPU.
105  */
106 int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
107 {
108         int ret = 0, cpu = get_cpu();
109
110         if (!test_and_set_bit(0, &work->pending)) {
111                 if (unlikely(is_single_threaded(wq)))
112                         cpu = singlethread_cpu;
113                 BUG_ON(!list_empty(&work->entry));
114                 __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
115                 ret = 1;
116         }
117         put_cpu();
118         return ret;
119 }
120 EXPORT_SYMBOL_GPL(queue_work);
121
122 static void delayed_work_timer_fn(unsigned long __data)
123 {
124         struct work_struct *work = (struct work_struct *)__data;
125         struct workqueue_struct *wq = work->wq_data;
126         int cpu = smp_processor_id();
127
128         if (unlikely(is_single_threaded(wq)))
129                 cpu = singlethread_cpu;
130
131         __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
132 }
133
134 /**
135  * queue_delayed_work - queue work on a workqueue after delay
136  * @wq: workqueue to use
137  * @work: work to queue
138  * @delay: number of jiffies to wait before queueing
139  *
140  * Returns non-zero if it was successfully added.
141  */
142 int fastcall queue_delayed_work(struct workqueue_struct *wq,
143                         struct work_struct *work, unsigned long delay)
144 {
145         int ret = 0;
146         struct timer_list *timer = &work->timer;
147
148         if (!test_and_set_bit(0, &work->pending)) {
149                 BUG_ON(timer_pending(timer));
150                 BUG_ON(!list_empty(&work->entry));
151
152                 /* This stores wq for the moment, for the timer_fn */
153                 work->wq_data = wq;
154                 timer->expires = jiffies + delay;
155                 timer->data = (unsigned long)work;
156                 timer->function = delayed_work_timer_fn;
157                 add_timer(timer);
158                 ret = 1;
159         }
160         return ret;
161 }
162 EXPORT_SYMBOL_GPL(queue_delayed_work);
163
164 /**
165  * queue_delayed_work_on - queue work on specific CPU after delay
166  * @cpu: CPU number to execute work on
167  * @wq: workqueue to use
168  * @work: work to queue
169  * @delay: number of jiffies to wait before queueing
170  *
171  * Returns non-zero if it was successfully added.
172  */
173 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
174                         struct work_struct *work, unsigned long delay)
175 {
176         int ret = 0;
177         struct timer_list *timer = &work->timer;
178
179         if (!test_and_set_bit(0, &work->pending)) {
180                 BUG_ON(timer_pending(timer));
181                 BUG_ON(!list_empty(&work->entry));
182
183                 /* This stores wq for the moment, for the timer_fn */
184                 work->wq_data = wq;
185                 timer->expires = jiffies + delay;
186                 timer->data = (unsigned long)work;
187                 timer->function = delayed_work_timer_fn;
188                 add_timer_on(timer, cpu);
189                 ret = 1;
190         }
191         return ret;
192 }
193 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
194
195 static void run_workqueue(struct cpu_workqueue_struct *cwq)
196 {
197         unsigned long flags;
198
199         /*
200          * Keep taking off work from the queue until
201          * done.
202          */
203         spin_lock_irqsave(&cwq->lock, flags);
204         cwq->run_depth++;
205         if (cwq->run_depth > 3) {
206                 /* morton gets to eat his hat */
207                 printk("%s: recursion depth exceeded: %d\n",
208                         __FUNCTION__, cwq->run_depth);
209                 dump_stack();
210         }
211         while (!list_empty(&cwq->worklist)) {
212                 struct work_struct *work = list_entry(cwq->worklist.next,
213                                                 struct work_struct, entry);
214                 void (*f) (void *) = work->func;
215                 void *data = work->data;
216
217                 list_del_init(cwq->worklist.next);
218                 spin_unlock_irqrestore(&cwq->lock, flags);
219
220                 BUG_ON(work->wq_data != cwq);
221                 clear_bit(0, &work->pending);
222                 f(data);
223
224                 spin_lock_irqsave(&cwq->lock, flags);
225                 cwq->remove_sequence++;
226                 wake_up(&cwq->work_done);
227         }
228         cwq->run_depth--;
229         spin_unlock_irqrestore(&cwq->lock, flags);
230 }
231
232 static int worker_thread(void *__cwq)
233 {
234         struct cpu_workqueue_struct *cwq = __cwq;
235         DECLARE_WAITQUEUE(wait, current);
236         struct k_sigaction sa;
237         sigset_t blocked;
238
239         current->flags |= PF_NOFREEZE;
240
241         set_user_nice(current, -5);
242
243         /* Block and flush all signals */
244         sigfillset(&blocked);
245         sigprocmask(SIG_BLOCK, &blocked, NULL);
246         flush_signals(current);
247
248         /* SIG_IGN makes children autoreap: see do_notify_parent(). */
249         sa.sa.sa_handler = SIG_IGN;
250         sa.sa.sa_flags = 0;
251         siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
252         do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
253
254         set_current_state(TASK_INTERRUPTIBLE);
255         while (!kthread_should_stop()) {
256                 add_wait_queue(&cwq->more_work, &wait);
257                 if (list_empty(&cwq->worklist))
258                         schedule();
259                 else
260                         __set_current_state(TASK_RUNNING);
261                 remove_wait_queue(&cwq->more_work, &wait);
262
263                 if (!list_empty(&cwq->worklist))
264                         run_workqueue(cwq);
265                 set_current_state(TASK_INTERRUPTIBLE);
266         }
267         __set_current_state(TASK_RUNNING);
268         return 0;
269 }
270
271 static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
272 {
273         if (cwq->thread == current) {
274                 /*
275                  * Probably keventd trying to flush its own queue. So simply run
276                  * it by hand rather than deadlocking.
277                  */
278                 run_workqueue(cwq);
279         } else {
280                 DEFINE_WAIT(wait);
281                 long sequence_needed;
282
283                 spin_lock_irq(&cwq->lock);
284                 sequence_needed = cwq->insert_sequence;
285
286                 while (sequence_needed - cwq->remove_sequence > 0) {
287                         prepare_to_wait(&cwq->work_done, &wait,
288                                         TASK_UNINTERRUPTIBLE);
289                         spin_unlock_irq(&cwq->lock);
290                         schedule();
291                         spin_lock_irq(&cwq->lock);
292                 }
293                 finish_wait(&cwq->work_done, &wait);
294                 spin_unlock_irq(&cwq->lock);
295         }
296 }
297
298 /**
299  * flush_workqueue - ensure that any scheduled work has run to completion.
300  * @wq: workqueue to flush
301  *
302  * Forces execution of the workqueue and blocks until its completion.
303  * This is typically used in driver shutdown handlers.
304  *
305  * This function will sample each workqueue's current insert_sequence number and
306  * will sleep until the head sequence is greater than or equal to that.  This
307  * means that we sleep until all works which were queued on entry have been
308  * handled, but we are not livelocked by new incoming ones.
309  *
310  * This function used to run the workqueues itself.  Now we just wait for the
311  * helper threads to do it.
312  */
313 void fastcall flush_workqueue(struct workqueue_struct *wq)
314 {
315         might_sleep();
316
317         if (is_single_threaded(wq)) {
318                 /* Always use first cpu's area. */
319                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu));
320         } else {
321                 int cpu;
322
323                 mutex_lock(&workqueue_mutex);
324                 for_each_online_cpu(cpu)
325                         flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
326                 mutex_unlock(&workqueue_mutex);
327         }
328 }
329 EXPORT_SYMBOL_GPL(flush_workqueue);
330
331 static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
332                                                    int cpu)
333 {
334         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
335         struct task_struct *p;
336
337         spin_lock_init(&cwq->lock);
338         cwq->wq = wq;
339         cwq->thread = NULL;
340         cwq->insert_sequence = 0;
341         cwq->remove_sequence = 0;
342         INIT_LIST_HEAD(&cwq->worklist);
343         init_waitqueue_head(&cwq->more_work);
344         init_waitqueue_head(&cwq->work_done);
345
346         if (is_single_threaded(wq))
347                 p = kthread_create(worker_thread, cwq, "%s", wq->name);
348         else
349                 p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
350         if (IS_ERR(p))
351                 return NULL;
352         cwq->thread = p;
353         return p;
354 }
355
356 struct workqueue_struct *__create_workqueue(const char *name,
357                                             int singlethread)
358 {
359         int cpu, destroy = 0;
360         struct workqueue_struct *wq;
361         struct task_struct *p;
362
363         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
364         if (!wq)
365                 return NULL;
366
367         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
368         if (!wq->cpu_wq) {
369                 kfree(wq);
370                 return NULL;
371         }
372
373         wq->name = name;
374         mutex_lock(&workqueue_mutex);
375         if (singlethread) {
376                 INIT_LIST_HEAD(&wq->list);
377                 p = create_workqueue_thread(wq, singlethread_cpu);
378                 if (!p)
379                         destroy = 1;
380                 else
381                         wake_up_process(p);
382         } else {
383                 list_add(&wq->list, &workqueues);
384                 for_each_online_cpu(cpu) {
385                         p = create_workqueue_thread(wq, cpu);
386                         if (p) {
387                                 kthread_bind(p, cpu);
388                                 wake_up_process(p);
389                         } else
390                                 destroy = 1;
391                 }
392         }
393         mutex_unlock(&workqueue_mutex);
394
395         /*
396          * Was there any error during startup? If yes then clean up:
397          */
398         if (destroy) {
399                 destroy_workqueue(wq);
400                 wq = NULL;
401         }
402         return wq;
403 }
404 EXPORT_SYMBOL_GPL(__create_workqueue);
405
406 static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
407 {
408         struct cpu_workqueue_struct *cwq;
409         unsigned long flags;
410         struct task_struct *p;
411
412         cwq = per_cpu_ptr(wq->cpu_wq, cpu);
413         spin_lock_irqsave(&cwq->lock, flags);
414         p = cwq->thread;
415         cwq->thread = NULL;
416         spin_unlock_irqrestore(&cwq->lock, flags);
417         if (p)
418                 kthread_stop(p);
419 }
420
421 /**
422  * destroy_workqueue - safely terminate a workqueue
423  * @wq: target workqueue
424  *
425  * Safely destroy a workqueue. All work currently pending will be done first.
426  */
427 void destroy_workqueue(struct workqueue_struct *wq)
428 {
429         int cpu;
430
431         flush_workqueue(wq);
432
433         /* We don't need the distraction of CPUs appearing and vanishing. */
434         mutex_lock(&workqueue_mutex);
435         if (is_single_threaded(wq))
436                 cleanup_workqueue_thread(wq, singlethread_cpu);
437         else {
438                 for_each_online_cpu(cpu)
439                         cleanup_workqueue_thread(wq, cpu);
440                 list_del(&wq->list);
441         }
442         mutex_unlock(&workqueue_mutex);
443         free_percpu(wq->cpu_wq);
444         kfree(wq);
445 }
446 EXPORT_SYMBOL_GPL(destroy_workqueue);
447
448 static struct workqueue_struct *keventd_wq;
449
450 /**
451  * schedule_work - put work task in global workqueue
452  * @work: job to be done
453  *
454  * This puts a job in the kernel-global workqueue.
455  */
456 int fastcall schedule_work(struct work_struct *work)
457 {
458         return queue_work(keventd_wq, work);
459 }
460 EXPORT_SYMBOL(schedule_work);
461
462 /**
463  * schedule_delayed_work - put work task in global workqueue after delay
464  * @work: job to be done
465  * @delay: number of jiffies to wait
466  *
467  * After waiting for a given time this puts a job in the kernel-global
468  * workqueue.
469  */
470 int fastcall schedule_delayed_work(struct work_struct *work, unsigned long delay)
471 {
472         return queue_delayed_work(keventd_wq, work, delay);
473 }
474 EXPORT_SYMBOL(schedule_delayed_work);
475
476 /**
477  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
478  * @cpu: cpu to use
479  * @work: job to be done
480  * @delay: number of jiffies to wait
481  *
482  * After waiting for a given time this puts a job in the kernel-global
483  * workqueue on the specified CPU.
484  */
485 int schedule_delayed_work_on(int cpu,
486                         struct work_struct *work, unsigned long delay)
487 {
488         return queue_delayed_work_on(cpu, keventd_wq, work, delay);
489 }
490 EXPORT_SYMBOL(schedule_delayed_work_on);
491
492 /**
493  * schedule_on_each_cpu - call a function on each online CPU from keventd
494  * @func: the function to call
495  * @info: a pointer to pass to func()
496  *
497  * Returns zero on success.
498  * Returns -ve errno on failure.
499  *
500  * Appears to be racy against CPU hotplug.
501  *
502  * schedule_on_each_cpu() is very slow.
503  */
504 int schedule_on_each_cpu(void (*func)(void *info), void *info)
505 {
506         int cpu;
507         struct work_struct *works;
508
509         works = alloc_percpu(struct work_struct);
510         if (!works)
511                 return -ENOMEM;
512
513         mutex_lock(&workqueue_mutex);
514         for_each_online_cpu(cpu) {
515                 INIT_WORK(per_cpu_ptr(works, cpu), func, info);
516                 __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),
517                                 per_cpu_ptr(works, cpu));
518         }
519         mutex_unlock(&workqueue_mutex);
520         flush_workqueue(keventd_wq);
521         free_percpu(works);
522         return 0;
523 }
524
525 void flush_scheduled_work(void)
526 {
527         flush_workqueue(keventd_wq);
528 }
529 EXPORT_SYMBOL(flush_scheduled_work);
530
531 /**
532  * cancel_rearming_delayed_workqueue - reliably kill off a delayed
533  *                      work whose handler rearms the delayed work.
534  * @wq:   the controlling workqueue structure
535  * @work: the delayed work struct
536  */
537 void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
538                                        struct work_struct *work)
539 {
540         while (!cancel_delayed_work(work))
541                 flush_workqueue(wq);
542 }
543 EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
544
545 /**
546  * cancel_rearming_delayed_work - reliably kill off a delayed keventd
547  *                      work whose handler rearms the delayed work.
548  * @work: the delayed work struct
549  */
550 void cancel_rearming_delayed_work(struct work_struct *work)
551 {
552         cancel_rearming_delayed_workqueue(keventd_wq, work);
553 }
554 EXPORT_SYMBOL(cancel_rearming_delayed_work);
555
556 /**
557  * execute_in_process_context - reliably execute the routine with user context
558  * @fn:         the function to execute
559  * @data:       data to pass to the function
560  * @ew:         guaranteed storage for the execute work structure (must
561  *              be available when the work executes)
562  *
563  * Executes the function immediately if process context is available,
564  * otherwise schedules the function for delayed execution.
565  *
566  * Returns:     0 - function was executed
567  *              1 - function was scheduled for execution
568  */
569 int execute_in_process_context(void (*fn)(void *data), void *data,
570                                struct execute_work *ew)
571 {
572         if (!in_interrupt()) {
573                 fn(data);
574                 return 0;
575         }
576
577         INIT_WORK(&ew->work, fn, data);
578         schedule_work(&ew->work);
579
580         return 1;
581 }
582 EXPORT_SYMBOL_GPL(execute_in_process_context);
583
584 int keventd_up(void)
585 {
586         return keventd_wq != NULL;
587 }
588
589 int current_is_keventd(void)
590 {
591         struct cpu_workqueue_struct *cwq;
592         int cpu = smp_processor_id();   /* preempt-safe: keventd is per-cpu */
593         int ret = 0;
594
595         BUG_ON(!keventd_wq);
596
597         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
598         if (current == cwq->thread)
599                 ret = 1;
600
601         return ret;
602
603 }
604
605 #ifdef CONFIG_HOTPLUG_CPU
606 /* Take the work from this (downed) CPU. */
607 static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
608 {
609         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
610         struct list_head list;
611         struct work_struct *work;
612
613         spin_lock_irq(&cwq->lock);
614         list_replace_init(&cwq->worklist, &list);
615
616         while (!list_empty(&list)) {
617                 printk("Taking work for %s\n", wq->name);
618                 work = list_entry(list.next,struct work_struct,entry);
619                 list_del(&work->entry);
620                 __queue_work(per_cpu_ptr(wq->cpu_wq, smp_processor_id()), work);
621         }
622         spin_unlock_irq(&cwq->lock);
623 }
624
625 /* We're holding the cpucontrol mutex here */
626 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
627                                   unsigned long action,
628                                   void *hcpu)
629 {
630         unsigned int hotcpu = (unsigned long)hcpu;
631         struct workqueue_struct *wq;
632
633         switch (action) {
634         case CPU_UP_PREPARE:
635                 mutex_lock(&workqueue_mutex);
636                 /* Create a new workqueue thread for it. */
637                 list_for_each_entry(wq, &workqueues, list) {
638                         if (!create_workqueue_thread(wq, hotcpu)) {
639                                 printk("workqueue for %i failed\n", hotcpu);
640                                 return NOTIFY_BAD;
641                         }
642                 }
643                 break;
644
645         case CPU_ONLINE:
646                 /* Kick off worker threads. */
647                 list_for_each_entry(wq, &workqueues, list) {
648                         struct cpu_workqueue_struct *cwq;
649
650                         cwq = per_cpu_ptr(wq->cpu_wq, hotcpu);
651                         kthread_bind(cwq->thread, hotcpu);
652                         wake_up_process(cwq->thread);
653                 }
654                 mutex_unlock(&workqueue_mutex);
655                 break;
656
657         case CPU_UP_CANCELED:
658                 list_for_each_entry(wq, &workqueues, list) {
659                         if (!per_cpu_ptr(wq->cpu_wq, hotcpu)->thread)
660                                 continue;
661                         /* Unbind so it can run. */
662                         kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,
663                                      any_online_cpu(cpu_online_map));
664                         cleanup_workqueue_thread(wq, hotcpu);
665                 }
666                 mutex_unlock(&workqueue_mutex);
667                 break;
668
669         case CPU_DOWN_PREPARE:
670                 mutex_lock(&workqueue_mutex);
671                 break;
672
673         case CPU_DOWN_FAILED:
674                 mutex_unlock(&workqueue_mutex);
675                 break;
676
677         case CPU_DEAD:
678                 list_for_each_entry(wq, &workqueues, list)
679                         cleanup_workqueue_thread(wq, hotcpu);
680                 list_for_each_entry(wq, &workqueues, list)
681                         take_over_work(wq, hotcpu);
682                 mutex_unlock(&workqueue_mutex);
683                 break;
684         }
685
686         return NOTIFY_OK;
687 }
688 #endif
689
690 void init_workqueues(void)
691 {
692         singlethread_cpu = first_cpu(cpu_possible_map);
693         hotcpu_notifier(workqueue_cpu_callback, 0);
694         keventd_wq = create_workqueue("events");
695         BUG_ON(!keventd_wq);
696 }
697