[NETLINK]: Add properly module refcounting for kernel netlink sockets.
[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 = kmalloc(sizeof(*wq), GFP_KERNEL);
312         if (!wq)
313                 return NULL;
314         memset(wq, 0, sizeof(*wq));
315
316         wq->name = name;
317         /* We don't need the distraction of CPUs appearing and vanishing. */
318         lock_cpu_hotplug();
319         if (singlethread) {
320                 INIT_LIST_HEAD(&wq->list);
321                 p = create_workqueue_thread(wq, 0);
322                 if (!p)
323                         destroy = 1;
324                 else
325                         wake_up_process(p);
326         } else {
327                 spin_lock(&workqueue_lock);
328                 list_add(&wq->list, &workqueues);
329                 spin_unlock(&workqueue_lock);
330                 for_each_online_cpu(cpu) {
331                         p = create_workqueue_thread(wq, cpu);
332                         if (p) {
333                                 kthread_bind(p, cpu);
334                                 wake_up_process(p);
335                         } else
336                                 destroy = 1;
337                 }
338         }
339         unlock_cpu_hotplug();
340
341         /*
342          * Was there any error during startup? If yes then clean up:
343          */
344         if (destroy) {
345                 destroy_workqueue(wq);
346                 wq = NULL;
347         }
348         return wq;
349 }
350
351 static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
352 {
353         struct cpu_workqueue_struct *cwq;
354         unsigned long flags;
355         struct task_struct *p;
356
357         cwq = wq->cpu_wq + cpu;
358         spin_lock_irqsave(&cwq->lock, flags);
359         p = cwq->thread;
360         cwq->thread = NULL;
361         spin_unlock_irqrestore(&cwq->lock, flags);
362         if (p)
363                 kthread_stop(p);
364 }
365
366 void destroy_workqueue(struct workqueue_struct *wq)
367 {
368         int cpu;
369
370         flush_workqueue(wq);
371
372         /* We don't need the distraction of CPUs appearing and vanishing. */
373         lock_cpu_hotplug();
374         if (is_single_threaded(wq))
375                 cleanup_workqueue_thread(wq, 0);
376         else {
377                 for_each_online_cpu(cpu)
378                         cleanup_workqueue_thread(wq, cpu);
379                 spin_lock(&workqueue_lock);
380                 list_del(&wq->list);
381                 spin_unlock(&workqueue_lock);
382         }
383         unlock_cpu_hotplug();
384         kfree(wq);
385 }
386
387 static struct workqueue_struct *keventd_wq;
388
389 int fastcall schedule_work(struct work_struct *work)
390 {
391         return queue_work(keventd_wq, work);
392 }
393
394 int fastcall schedule_delayed_work(struct work_struct *work, unsigned long delay)
395 {
396         return queue_delayed_work(keventd_wq, work, delay);
397 }
398
399 int schedule_delayed_work_on(int cpu,
400                         struct work_struct *work, unsigned long delay)
401 {
402         int ret = 0;
403         struct timer_list *timer = &work->timer;
404
405         if (!test_and_set_bit(0, &work->pending)) {
406                 BUG_ON(timer_pending(timer));
407                 BUG_ON(!list_empty(&work->entry));
408                 /* This stores keventd_wq for the moment, for the timer_fn */
409                 work->wq_data = keventd_wq;
410                 timer->expires = jiffies + delay;
411                 timer->data = (unsigned long)work;
412                 timer->function = delayed_work_timer_fn;
413                 add_timer_on(timer, cpu);
414                 ret = 1;
415         }
416         return ret;
417 }
418
419 void flush_scheduled_work(void)
420 {
421         flush_workqueue(keventd_wq);
422 }
423
424 /**
425  * cancel_rearming_delayed_workqueue - reliably kill off a delayed
426  *                      work whose handler rearms the delayed work.
427  * @wq:   the controlling workqueue structure
428  * @work: the delayed work struct
429  */
430 void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
431                                        struct work_struct *work)
432 {
433         while (!cancel_delayed_work(work))
434                 flush_workqueue(wq);
435 }
436 EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
437
438 /**
439  * cancel_rearming_delayed_work - reliably kill off a delayed keventd
440  *                      work whose handler rearms the delayed work.
441  * @work: the delayed work struct
442  */
443 void cancel_rearming_delayed_work(struct work_struct *work)
444 {
445         cancel_rearming_delayed_workqueue(keventd_wq, work);
446 }
447 EXPORT_SYMBOL(cancel_rearming_delayed_work);
448
449 int keventd_up(void)
450 {
451         return keventd_wq != NULL;
452 }
453
454 int current_is_keventd(void)
455 {
456         struct cpu_workqueue_struct *cwq;
457         int cpu = smp_processor_id();   /* preempt-safe: keventd is per-cpu */
458         int ret = 0;
459
460         BUG_ON(!keventd_wq);
461
462         cwq = keventd_wq->cpu_wq + cpu;
463         if (current == cwq->thread)
464                 ret = 1;
465
466         return ret;
467
468 }
469
470 #ifdef CONFIG_HOTPLUG_CPU
471 /* Take the work from this (downed) CPU. */
472 static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
473 {
474         struct cpu_workqueue_struct *cwq = wq->cpu_wq + cpu;
475         LIST_HEAD(list);
476         struct work_struct *work;
477
478         spin_lock_irq(&cwq->lock);
479         list_splice_init(&cwq->worklist, &list);
480
481         while (!list_empty(&list)) {
482                 printk("Taking work for %s\n", wq->name);
483                 work = list_entry(list.next,struct work_struct,entry);
484                 list_del(&work->entry);
485                 __queue_work(wq->cpu_wq + smp_processor_id(), work);
486         }
487         spin_unlock_irq(&cwq->lock);
488 }
489
490 /* We're holding the cpucontrol mutex here */
491 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
492                                   unsigned long action,
493                                   void *hcpu)
494 {
495         unsigned int hotcpu = (unsigned long)hcpu;
496         struct workqueue_struct *wq;
497
498         switch (action) {
499         case CPU_UP_PREPARE:
500                 /* Create a new workqueue thread for it. */
501                 list_for_each_entry(wq, &workqueues, list) {
502                         if (create_workqueue_thread(wq, hotcpu) < 0) {
503                                 printk("workqueue for %i failed\n", hotcpu);
504                                 return NOTIFY_BAD;
505                         }
506                 }
507                 break;
508
509         case CPU_ONLINE:
510                 /* Kick off worker threads. */
511                 list_for_each_entry(wq, &workqueues, list) {
512                         kthread_bind(wq->cpu_wq[hotcpu].thread, hotcpu);
513                         wake_up_process(wq->cpu_wq[hotcpu].thread);
514                 }
515                 break;
516
517         case CPU_UP_CANCELED:
518                 list_for_each_entry(wq, &workqueues, list) {
519                         /* Unbind so it can run. */
520                         kthread_bind(wq->cpu_wq[hotcpu].thread,
521                                      smp_processor_id());
522                         cleanup_workqueue_thread(wq, hotcpu);
523                 }
524                 break;
525
526         case CPU_DEAD:
527                 list_for_each_entry(wq, &workqueues, list)
528                         cleanup_workqueue_thread(wq, hotcpu);
529                 list_for_each_entry(wq, &workqueues, list)
530                         take_over_work(wq, hotcpu);
531                 break;
532         }
533
534         return NOTIFY_OK;
535 }
536 #endif
537
538 void init_workqueues(void)
539 {
540         hotcpu_notifier(workqueue_cpu_callback, 0);
541         keventd_wq = create_workqueue("events");
542         BUG_ON(!keventd_wq);
543 }
544
545 EXPORT_SYMBOL_GPL(__create_workqueue);
546 EXPORT_SYMBOL_GPL(queue_work);
547 EXPORT_SYMBOL_GPL(queue_delayed_work);
548 EXPORT_SYMBOL_GPL(flush_workqueue);
549 EXPORT_SYMBOL_GPL(destroy_workqueue);
550
551 EXPORT_SYMBOL(schedule_work);
552 EXPORT_SYMBOL(schedule_delayed_work);
553 EXPORT_SYMBOL(schedule_delayed_work_on);
554 EXPORT_SYMBOL(flush_scheduled_work);