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