91bacb13a7e2fec56f5067f12e0b97c1043c30b7
[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
17 #include <linux/module.h>
18 #include <linux/kernel.h>
19 #include <linux/sched.h>
20 #include <linux/init.h>
21 #include <linux/signal.h>
22 #include <linux/completion.h>
23 #include <linux/workqueue.h>
24 #include <linux/slab.h>
25 #include <linux/cpu.h>
26 #include <linux/notifier.h>
27 #include <linux/kthread.h>
28
29 /*
30  * The per-CPU workqueue (if single thread, we always use cpu 0's).
31  *
32  * The sequence counters are for flush_scheduled_work().  It wants to wait
33  * until until all currently-scheduled works are completed, but it doesn't
34  * want to be livelocked by new, incoming ones.  So it waits until
35  * remove_sequence is >= the insert_sequence which pertained when
36  * flush_scheduled_work() was called.
37  */
38 struct cpu_workqueue_struct {
39
40         spinlock_t lock;
41
42         long remove_sequence;   /* Least-recently added (next to run) */
43         long insert_sequence;   /* Next to add */
44
45         struct list_head worklist;
46         wait_queue_head_t more_work;
47         wait_queue_head_t work_done;
48
49         struct workqueue_struct *wq;
50         task_t *thread;
51
52         int run_depth;          /* Detect run_workqueue() recursion depth */
53 } ____cacheline_aligned;
54
55 /*
56  * The externally visible workqueue abstraction is an array of
57  * per-CPU workqueues:
58  */
59 struct workqueue_struct {
60         struct cpu_workqueue_struct cpu_wq[NR_CPUS];
61         const char *name;
62         struct list_head list;  /* Empty if single thread */
63 };
64
65 /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
66    threads to each one as cpus come/go. */
67 static DEFINE_SPINLOCK(workqueue_lock);
68 static LIST_HEAD(workqueues);
69
70 /* If it's single threaded, it isn't in the list of workqueues. */
71 static inline int is_single_threaded(struct workqueue_struct *wq)
72 {
73         return list_empty(&wq->list);
74 }
75
76 /* Preempt must be disabled. */
77 static void __queue_work(struct cpu_workqueue_struct *cwq,
78                          struct work_struct *work)
79 {
80         unsigned long flags;
81
82         spin_lock_irqsave(&cwq->lock, flags);
83         work->wq_data = cwq;
84         list_add_tail(&work->entry, &cwq->worklist);
85         cwq->insert_sequence++;
86         wake_up(&cwq->more_work);
87         spin_unlock_irqrestore(&cwq->lock, flags);
88 }
89
90 /*
91  * Queue work on a workqueue. Return non-zero if it was successfully
92  * added.
93  *
94  * We queue the work to the CPU it was submitted, but there is no
95  * guarantee that it will be processed by that CPU.
96  */
97 int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
98 {
99         int ret = 0, cpu = get_cpu();
100
101         if (!test_and_set_bit(0, &work->pending)) {
102                 if (unlikely(is_single_threaded(wq)))
103                         cpu = 0;
104                 BUG_ON(!list_empty(&work->entry));
105                 __queue_work(wq->cpu_wq + cpu, work);
106                 ret = 1;
107         }
108         put_cpu();
109         return ret;
110 }
111
112 static void delayed_work_timer_fn(unsigned long __data)
113 {
114         struct work_struct *work = (struct work_struct *)__data;
115         struct workqueue_struct *wq = work->wq_data;
116         int cpu = smp_processor_id();
117
118         if (unlikely(is_single_threaded(wq)))
119                 cpu = 0;
120
121         __queue_work(wq->cpu_wq + cpu, work);
122 }
123
124 int fastcall queue_delayed_work(struct workqueue_struct *wq,
125                         struct work_struct *work, unsigned long delay)
126 {
127         int ret = 0;
128         struct timer_list *timer = &work->timer;
129
130         if (!test_and_set_bit(0, &work->pending)) {
131                 BUG_ON(timer_pending(timer));
132                 BUG_ON(!list_empty(&work->entry));
133
134                 /* This stores wq for the moment, for the timer_fn */
135                 work->wq_data = wq;
136                 timer->expires = jiffies + delay;
137                 timer->data = (unsigned long)work;
138                 timer->function = delayed_work_timer_fn;
139                 add_timer(timer);
140                 ret = 1;
141         }
142         return ret;
143 }
144
145 static inline void run_workqueue(struct cpu_workqueue_struct *cwq)
146 {
147         unsigned long flags;
148
149         /*
150          * Keep taking off work from the queue until
151          * done.
152          */
153         spin_lock_irqsave(&cwq->lock, flags);
154         cwq->run_depth++;
155         if (cwq->run_depth > 3) {
156                 /* morton gets to eat his hat */
157                 printk("%s: recursion depth exceeded: %d\n",
158                         __FUNCTION__, cwq->run_depth);
159                 dump_stack();
160         }
161         while (!list_empty(&cwq->worklist)) {
162                 struct work_struct *work = list_entry(cwq->worklist.next,
163                                                 struct work_struct, entry);
164                 void (*f) (void *) = work->func;
165                 void *data = work->data;
166
167                 list_del_init(cwq->worklist.next);
168                 spin_unlock_irqrestore(&cwq->lock, flags);
169
170                 BUG_ON(work->wq_data != cwq);
171                 clear_bit(0, &work->pending);
172                 f(data);
173
174                 spin_lock_irqsave(&cwq->lock, flags);
175                 cwq->remove_sequence++;
176                 wake_up(&cwq->work_done);
177         }
178         cwq->run_depth--;
179         spin_unlock_irqrestore(&cwq->lock, flags);
180 }
181
182 static int worker_thread(void *__cwq)
183 {
184         struct cpu_workqueue_struct *cwq = __cwq;
185         DECLARE_WAITQUEUE(wait, current);
186         struct k_sigaction sa;
187         sigset_t blocked;
188
189         current->flags |= PF_NOFREEZE;
190
191         set_user_nice(current, -5);
192
193         /* Block and flush all signals */
194         sigfillset(&blocked);
195         sigprocmask(SIG_BLOCK, &blocked, NULL);
196         flush_signals(current);
197
198         /* SIG_IGN makes children autoreap: see do_notify_parent(). */
199         sa.sa.sa_handler = SIG_IGN;
200         sa.sa.sa_flags = 0;
201         siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
202         do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
203
204         set_current_state(TASK_INTERRUPTIBLE);
205         while (!kthread_should_stop()) {
206                 add_wait_queue(&cwq->more_work, &wait);
207                 if (list_empty(&cwq->worklist))
208                         schedule();
209                 else
210                         __set_current_state(TASK_RUNNING);
211                 remove_wait_queue(&cwq->more_work, &wait);
212
213                 if (!list_empty(&cwq->worklist))
214                         run_workqueue(cwq);
215                 set_current_state(TASK_INTERRUPTIBLE);
216         }
217         __set_current_state(TASK_RUNNING);
218         return 0;
219 }
220
221 static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
222 {
223         if (cwq->thread == current) {
224                 /*
225                  * Probably keventd trying to flush its own queue. So simply run
226                  * it by hand rather than deadlocking.
227                  */
228                 run_workqueue(cwq);
229         } else {
230                 DEFINE_WAIT(wait);
231                 long sequence_needed;
232
233                 spin_lock_irq(&cwq->lock);
234                 sequence_needed = cwq->insert_sequence;
235
236                 while (sequence_needed - cwq->remove_sequence > 0) {
237                         prepare_to_wait(&cwq->work_done, &wait,
238                                         TASK_UNINTERRUPTIBLE);
239                         spin_unlock_irq(&cwq->lock);
240                         schedule();
241                         spin_lock_irq(&cwq->lock);
242                 }
243                 finish_wait(&cwq->work_done, &wait);
244                 spin_unlock_irq(&cwq->lock);
245         }
246 }
247
248 /*
249  * flush_workqueue - ensure that any scheduled work has run to completion.
250  *
251  * Forces execution of the workqueue and blocks until its completion.
252  * This is typically used in driver shutdown handlers.
253  *
254  * This function will sample each workqueue's current insert_sequence number and
255  * will sleep until the head sequence is greater than or equal to that.  This
256  * means that we sleep until all works which were queued on entry have been
257  * handled, but we are not livelocked by new incoming ones.
258  *
259  * This function used to run the workqueues itself.  Now we just wait for the
260  * helper threads to do it.
261  */
262 void fastcall flush_workqueue(struct workqueue_struct *wq)
263 {
264         might_sleep();
265
266         if (is_single_threaded(wq)) {
267                 /* Always use cpu 0's area. */
268                 flush_cpu_workqueue(wq->cpu_wq + 0);
269         } else {
270                 int cpu;
271
272                 lock_cpu_hotplug();
273                 for_each_online_cpu(cpu)
274                         flush_cpu_workqueue(wq->cpu_wq + cpu);
275                 unlock_cpu_hotplug();
276         }
277 }
278
279 static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
280                                                    int cpu)
281 {
282         struct cpu_workqueue_struct *cwq = wq->cpu_wq + cpu;
283         struct task_struct *p;
284
285         spin_lock_init(&cwq->lock);
286         cwq->wq = wq;
287         cwq->thread = NULL;
288         cwq->insert_sequence = 0;
289         cwq->remove_sequence = 0;
290         INIT_LIST_HEAD(&cwq->worklist);
291         init_waitqueue_head(&cwq->more_work);
292         init_waitqueue_head(&cwq->work_done);
293
294         if (is_single_threaded(wq))
295                 p = kthread_create(worker_thread, cwq, "%s", wq->name);
296         else
297                 p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
298         if (IS_ERR(p))
299                 return NULL;
300         cwq->thread = p;
301         return p;
302 }
303
304 struct workqueue_struct *__create_workqueue(const char *name,
305                                             int singlethread)
306 {
307         int cpu, destroy = 0;
308         struct workqueue_struct *wq;
309         struct task_struct *p;
310
311         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
312         if (!wq)
313                 return NULL;
314
315         wq->name = name;
316         /* We don't need the distraction of CPUs appearing and vanishing. */
317         lock_cpu_hotplug();
318         if (singlethread) {
319                 INIT_LIST_HEAD(&wq->list);
320                 p = create_workqueue_thread(wq, 0);
321                 if (!p)
322                         destroy = 1;
323                 else
324                         wake_up_process(p);
325         } else {
326                 spin_lock(&workqueue_lock);
327                 list_add(&wq->list, &workqueues);
328                 spin_unlock(&workqueue_lock);
329                 for_each_online_cpu(cpu) {
330                         p = create_workqueue_thread(wq, cpu);
331                         if (p) {
332                                 kthread_bind(p, cpu);
333                                 wake_up_process(p);
334                         } else
335                                 destroy = 1;
336                 }
337         }
338         unlock_cpu_hotplug();
339
340         /*
341          * Was there any error during startup? If yes then clean up:
342          */
343         if (destroy) {
344                 destroy_workqueue(wq);
345                 wq = NULL;
346         }
347         return wq;
348 }
349
350 static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
351 {
352         struct cpu_workqueue_struct *cwq;
353         unsigned long flags;
354         struct task_struct *p;
355
356         cwq = wq->cpu_wq + cpu;
357         spin_lock_irqsave(&cwq->lock, flags);
358         p = cwq->thread;
359         cwq->thread = NULL;
360         spin_unlock_irqrestore(&cwq->lock, flags);
361         if (p)
362                 kthread_stop(p);
363 }
364
365 void destroy_workqueue(struct workqueue_struct *wq)
366 {
367         int cpu;
368
369         flush_workqueue(wq);
370
371         /* We don't need the distraction of CPUs appearing and vanishing. */
372         lock_cpu_hotplug();
373         if (is_single_threaded(wq))
374                 cleanup_workqueue_thread(wq, 0);
375         else {
376                 for_each_online_cpu(cpu)
377                         cleanup_workqueue_thread(wq, cpu);
378                 spin_lock(&workqueue_lock);
379                 list_del(&wq->list);
380                 spin_unlock(&workqueue_lock);
381         }
382         unlock_cpu_hotplug();
383         kfree(wq);
384 }
385
386 static struct workqueue_struct *keventd_wq;
387
388 int fastcall schedule_work(struct work_struct *work)
389 {
390         return queue_work(keventd_wq, work);
391 }
392
393 int fastcall schedule_delayed_work(struct work_struct *work, unsigned long delay)
394 {
395         return queue_delayed_work(keventd_wq, work, delay);
396 }
397
398 int schedule_delayed_work_on(int cpu,
399                         struct work_struct *work, unsigned long delay)
400 {
401         int ret = 0;
402         struct timer_list *timer = &work->timer;
403
404         if (!test_and_set_bit(0, &work->pending)) {
405                 BUG_ON(timer_pending(timer));
406                 BUG_ON(!list_empty(&work->entry));
407                 /* This stores keventd_wq for the moment, for the timer_fn */
408                 work->wq_data = keventd_wq;
409                 timer->expires = jiffies + delay;
410                 timer->data = (unsigned long)work;
411                 timer->function = delayed_work_timer_fn;
412                 add_timer_on(timer, cpu);
413                 ret = 1;
414         }
415         return ret;
416 }
417
418 void flush_scheduled_work(void)
419 {
420         flush_workqueue(keventd_wq);
421 }
422
423 /**
424  * cancel_rearming_delayed_workqueue - reliably kill off a delayed
425  *                      work whose handler rearms the delayed work.
426  * @wq:   the controlling workqueue structure
427  * @work: the delayed work struct
428  */
429 void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
430                                        struct work_struct *work)
431 {
432         while (!cancel_delayed_work(work))
433                 flush_workqueue(wq);
434 }
435 EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
436
437 /**
438  * cancel_rearming_delayed_work - reliably kill off a delayed keventd
439  *                      work whose handler rearms the delayed work.
440  * @work: the delayed work struct
441  */
442 void cancel_rearming_delayed_work(struct work_struct *work)
443 {
444         cancel_rearming_delayed_workqueue(keventd_wq, work);
445 }
446 EXPORT_SYMBOL(cancel_rearming_delayed_work);
447
448 int keventd_up(void)
449 {
450         return keventd_wq != NULL;
451 }
452
453 int current_is_keventd(void)
454 {
455         struct cpu_workqueue_struct *cwq;
456         int cpu = smp_processor_id();   /* preempt-safe: keventd is per-cpu */
457         int ret = 0;
458
459         BUG_ON(!keventd_wq);
460
461         cwq = keventd_wq->cpu_wq + cpu;
462         if (current == cwq->thread)
463                 ret = 1;
464
465         return ret;
466
467 }
468
469 #ifdef CONFIG_HOTPLUG_CPU
470 /* Take the work from this (downed) CPU. */
471 static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
472 {
473         struct cpu_workqueue_struct *cwq = wq->cpu_wq + cpu;
474         LIST_HEAD(list);
475         struct work_struct *work;
476
477         spin_lock_irq(&cwq->lock);
478         list_splice_init(&cwq->worklist, &list);
479
480         while (!list_empty(&list)) {
481                 printk("Taking work for %s\n", wq->name);
482                 work = list_entry(list.next,struct work_struct,entry);
483                 list_del(&work->entry);
484                 __queue_work(wq->cpu_wq + smp_processor_id(), work);
485         }
486         spin_unlock_irq(&cwq->lock);
487 }
488
489 /* We're holding the cpucontrol mutex here */
490 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
491                                   unsigned long action,
492                                   void *hcpu)
493 {
494         unsigned int hotcpu = (unsigned long)hcpu;
495         struct workqueue_struct *wq;
496
497         switch (action) {
498         case CPU_UP_PREPARE:
499                 /* Create a new workqueue thread for it. */
500                 list_for_each_entry(wq, &workqueues, list) {
501                         if (!create_workqueue_thread(wq, hotcpu)) {
502                                 printk("workqueue for %i failed\n", hotcpu);
503                                 return NOTIFY_BAD;
504                         }
505                 }
506                 break;
507
508         case CPU_ONLINE:
509                 /* Kick off worker threads. */
510                 list_for_each_entry(wq, &workqueues, list) {
511                         kthread_bind(wq->cpu_wq[hotcpu].thread, hotcpu);
512                         wake_up_process(wq->cpu_wq[hotcpu].thread);
513                 }
514                 break;
515
516         case CPU_UP_CANCELED:
517                 list_for_each_entry(wq, &workqueues, list) {
518                         /* Unbind so it can run. */
519                         kthread_bind(wq->cpu_wq[hotcpu].thread,
520                                      smp_processor_id());
521                         cleanup_workqueue_thread(wq, hotcpu);
522                 }
523                 break;
524
525         case CPU_DEAD:
526                 list_for_each_entry(wq, &workqueues, list)
527                         cleanup_workqueue_thread(wq, hotcpu);
528                 list_for_each_entry(wq, &workqueues, list)
529                         take_over_work(wq, hotcpu);
530                 break;
531         }
532
533         return NOTIFY_OK;
534 }
535 #endif
536
537 void init_workqueues(void)
538 {
539         hotcpu_notifier(workqueue_cpu_callback, 0);
540         keventd_wq = create_workqueue("events");
541         BUG_ON(!keventd_wq);
542 }
543
544 EXPORT_SYMBOL_GPL(__create_workqueue);
545 EXPORT_SYMBOL_GPL(queue_work);
546 EXPORT_SYMBOL_GPL(queue_delayed_work);
547 EXPORT_SYMBOL_GPL(flush_workqueue);
548 EXPORT_SYMBOL_GPL(destroy_workqueue);
549
550 EXPORT_SYMBOL(schedule_work);
551 EXPORT_SYMBOL(schedule_delayed_work);
552 EXPORT_SYMBOL(schedule_delayed_work_on);
553 EXPORT_SYMBOL(flush_scheduled_work);