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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
31 /*
32  * The per-CPU workqueue (if single thread, we always use the first
33  * possible cpu).
34  *
35  * The sequence counters are for flush_scheduled_work().  It wants to wait
36  * until until all currently-scheduled works are completed, but it doesn't
37  * want to be livelocked by new, incoming ones.  So it waits until
38  * remove_sequence is >= the insert_sequence which pertained when
39  * flush_scheduled_work() was called.
40  */
41 struct cpu_workqueue_struct {
42
43         spinlock_t lock;
44
45         long remove_sequence;   /* Least-recently added (next to run) */
46         long insert_sequence;   /* Next to add */
47
48         struct list_head worklist;
49         wait_queue_head_t more_work;
50         wait_queue_head_t work_done;
51
52         struct workqueue_struct *wq;
53         task_t *thread;
54
55         int run_depth;          /* Detect run_workqueue() recursion depth */
56 } ____cacheline_aligned;
57
58 /*
59  * The externally visible workqueue abstraction is an array of
60  * per-CPU workqueues:
61  */
62 struct workqueue_struct {
63         struct cpu_workqueue_struct *cpu_wq;
64         const char *name;
65         struct list_head list;  /* Empty if single thread */
66 };
67
68 /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
69    threads to each one as cpus come/go. */
70 static DEFINE_SPINLOCK(workqueue_lock);
71 static LIST_HEAD(workqueues);
72
73 static int singlethread_cpu;
74
75 /* If it's single threaded, it isn't in the list of workqueues. */
76 static inline int is_single_threaded(struct workqueue_struct *wq)
77 {
78         return list_empty(&wq->list);
79 }
80
81 /* Preempt must be disabled. */
82 static void __queue_work(struct cpu_workqueue_struct *cwq,
83                          struct work_struct *work)
84 {
85         unsigned long flags;
86
87         spin_lock_irqsave(&cwq->lock, flags);
88         work->wq_data = cwq;
89         list_add_tail(&work->entry, &cwq->worklist);
90         cwq->insert_sequence++;
91         wake_up(&cwq->more_work);
92         spin_unlock_irqrestore(&cwq->lock, flags);
93 }
94
95 /*
96  * Queue work on a workqueue. Return non-zero if it was successfully
97  * added.
98  *
99  * We queue the work to the CPU it was submitted, but there is no
100  * guarantee that it will be processed by that CPU.
101  */
102 int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
103 {
104         int ret = 0, cpu = get_cpu();
105
106         if (!test_and_set_bit(0, &work->pending)) {
107                 if (unlikely(is_single_threaded(wq)))
108                         cpu = singlethread_cpu;
109                 BUG_ON(!list_empty(&work->entry));
110                 __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
111                 ret = 1;
112         }
113         put_cpu();
114         return ret;
115 }
116
117 static void delayed_work_timer_fn(unsigned long __data)
118 {
119         struct work_struct *work = (struct work_struct *)__data;
120         struct workqueue_struct *wq = work->wq_data;
121         int cpu = smp_processor_id();
122
123         if (unlikely(is_single_threaded(wq)))
124                 cpu = singlethread_cpu;
125
126         __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
127 }
128
129 int fastcall queue_delayed_work(struct workqueue_struct *wq,
130                         struct work_struct *work, unsigned long delay)
131 {
132         int ret = 0;
133         struct timer_list *timer = &work->timer;
134
135         if (!test_and_set_bit(0, &work->pending)) {
136                 BUG_ON(timer_pending(timer));
137                 BUG_ON(!list_empty(&work->entry));
138
139                 /* This stores wq for the moment, for the timer_fn */
140                 work->wq_data = wq;
141                 timer->expires = jiffies + delay;
142                 timer->data = (unsigned long)work;
143                 timer->function = delayed_work_timer_fn;
144                 add_timer(timer);
145                 ret = 1;
146         }
147         return ret;
148 }
149
150 static void run_workqueue(struct cpu_workqueue_struct *cwq)
151 {
152         unsigned long flags;
153
154         /*
155          * Keep taking off work from the queue until
156          * done.
157          */
158         spin_lock_irqsave(&cwq->lock, flags);
159         cwq->run_depth++;
160         if (cwq->run_depth > 3) {
161                 /* morton gets to eat his hat */
162                 printk("%s: recursion depth exceeded: %d\n",
163                         __FUNCTION__, cwq->run_depth);
164                 dump_stack();
165         }
166         while (!list_empty(&cwq->worklist)) {
167                 struct work_struct *work = list_entry(cwq->worklist.next,
168                                                 struct work_struct, entry);
169                 void (*f) (void *) = work->func;
170                 void *data = work->data;
171
172                 list_del_init(cwq->worklist.next);
173                 spin_unlock_irqrestore(&cwq->lock, flags);
174
175                 BUG_ON(work->wq_data != cwq);
176                 clear_bit(0, &work->pending);
177                 f(data);
178
179                 spin_lock_irqsave(&cwq->lock, flags);
180                 cwq->remove_sequence++;
181                 wake_up(&cwq->work_done);
182         }
183         cwq->run_depth--;
184         spin_unlock_irqrestore(&cwq->lock, flags);
185 }
186
187 static int worker_thread(void *__cwq)
188 {
189         struct cpu_workqueue_struct *cwq = __cwq;
190         DECLARE_WAITQUEUE(wait, current);
191         struct k_sigaction sa;
192         sigset_t blocked;
193
194         current->flags |= PF_NOFREEZE;
195
196         set_user_nice(current, -5);
197
198         /* Block and flush all signals */
199         sigfillset(&blocked);
200         sigprocmask(SIG_BLOCK, &blocked, NULL);
201         flush_signals(current);
202
203         /* SIG_IGN makes children autoreap: see do_notify_parent(). */
204         sa.sa.sa_handler = SIG_IGN;
205         sa.sa.sa_flags = 0;
206         siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
207         do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
208
209         set_current_state(TASK_INTERRUPTIBLE);
210         while (!kthread_should_stop()) {
211                 add_wait_queue(&cwq->more_work, &wait);
212                 if (list_empty(&cwq->worklist))
213                         schedule();
214                 else
215                         __set_current_state(TASK_RUNNING);
216                 remove_wait_queue(&cwq->more_work, &wait);
217
218                 if (!list_empty(&cwq->worklist))
219                         run_workqueue(cwq);
220                 set_current_state(TASK_INTERRUPTIBLE);
221         }
222         __set_current_state(TASK_RUNNING);
223         return 0;
224 }
225
226 static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
227 {
228         if (cwq->thread == current) {
229                 /*
230                  * Probably keventd trying to flush its own queue. So simply run
231                  * it by hand rather than deadlocking.
232                  */
233                 run_workqueue(cwq);
234         } else {
235                 DEFINE_WAIT(wait);
236                 long sequence_needed;
237
238                 spin_lock_irq(&cwq->lock);
239                 sequence_needed = cwq->insert_sequence;
240
241                 while (sequence_needed - cwq->remove_sequence > 0) {
242                         prepare_to_wait(&cwq->work_done, &wait,
243                                         TASK_UNINTERRUPTIBLE);
244                         spin_unlock_irq(&cwq->lock);
245                         schedule();
246                         spin_lock_irq(&cwq->lock);
247                 }
248                 finish_wait(&cwq->work_done, &wait);
249                 spin_unlock_irq(&cwq->lock);
250         }
251 }
252
253 /*
254  * flush_workqueue - ensure that any scheduled work has run to completion.
255  *
256  * Forces execution of the workqueue and blocks until its completion.
257  * This is typically used in driver shutdown handlers.
258  *
259  * This function will sample each workqueue's current insert_sequence number and
260  * will sleep until the head sequence is greater than or equal to that.  This
261  * means that we sleep until all works which were queued on entry have been
262  * handled, but we are not livelocked by new incoming ones.
263  *
264  * This function used to run the workqueues itself.  Now we just wait for the
265  * helper threads to do it.
266  */
267 void fastcall flush_workqueue(struct workqueue_struct *wq)
268 {
269         might_sleep();
270
271         if (is_single_threaded(wq)) {
272                 /* Always use first cpu's area. */
273                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu));
274         } else {
275                 int cpu;
276
277                 lock_cpu_hotplug();
278                 for_each_online_cpu(cpu)
279                         flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
280                 unlock_cpu_hotplug();
281         }
282 }
283
284 static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
285                                                    int cpu)
286 {
287         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
288         struct task_struct *p;
289
290         spin_lock_init(&cwq->lock);
291         cwq->wq = wq;
292         cwq->thread = NULL;
293         cwq->insert_sequence = 0;
294         cwq->remove_sequence = 0;
295         INIT_LIST_HEAD(&cwq->worklist);
296         init_waitqueue_head(&cwq->more_work);
297         init_waitqueue_head(&cwq->work_done);
298
299         if (is_single_threaded(wq))
300                 p = kthread_create(worker_thread, cwq, "%s", wq->name);
301         else
302                 p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
303         if (IS_ERR(p))
304                 return NULL;
305         cwq->thread = p;
306         return p;
307 }
308
309 struct workqueue_struct *__create_workqueue(const char *name,
310                                             int singlethread)
311 {
312         int cpu, destroy = 0;
313         struct workqueue_struct *wq;
314         struct task_struct *p;
315
316         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
317         if (!wq)
318                 return NULL;
319
320         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
321         if (!wq->cpu_wq) {
322                 kfree(wq);
323                 return NULL;
324         }
325
326         wq->name = name;
327         /* We don't need the distraction of CPUs appearing and vanishing. */
328         lock_cpu_hotplug();
329         if (singlethread) {
330                 INIT_LIST_HEAD(&wq->list);
331                 p = create_workqueue_thread(wq, singlethread_cpu);
332                 if (!p)
333                         destroy = 1;
334                 else
335                         wake_up_process(p);
336         } else {
337                 spin_lock(&workqueue_lock);
338                 list_add(&wq->list, &workqueues);
339                 spin_unlock(&workqueue_lock);
340                 for_each_online_cpu(cpu) {
341                         p = create_workqueue_thread(wq, cpu);
342                         if (p) {
343                                 kthread_bind(p, cpu);
344                                 wake_up_process(p);
345                         } else
346                                 destroy = 1;
347                 }
348         }
349         unlock_cpu_hotplug();
350
351         /*
352          * Was there any error during startup? If yes then clean up:
353          */
354         if (destroy) {
355                 destroy_workqueue(wq);
356                 wq = NULL;
357         }
358         return wq;
359 }
360
361 static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
362 {
363         struct cpu_workqueue_struct *cwq;
364         unsigned long flags;
365         struct task_struct *p;
366
367         cwq = per_cpu_ptr(wq->cpu_wq, cpu);
368         spin_lock_irqsave(&cwq->lock, flags);
369         p = cwq->thread;
370         cwq->thread = NULL;
371         spin_unlock_irqrestore(&cwq->lock, flags);
372         if (p)
373                 kthread_stop(p);
374 }
375
376 void destroy_workqueue(struct workqueue_struct *wq)
377 {
378         int cpu;
379
380         flush_workqueue(wq);
381
382         /* We don't need the distraction of CPUs appearing and vanishing. */
383         lock_cpu_hotplug();
384         if (is_single_threaded(wq))
385                 cleanup_workqueue_thread(wq, singlethread_cpu);
386         else {
387                 for_each_online_cpu(cpu)
388                         cleanup_workqueue_thread(wq, cpu);
389                 spin_lock(&workqueue_lock);
390                 list_del(&wq->list);
391                 spin_unlock(&workqueue_lock);
392         }
393         unlock_cpu_hotplug();
394         free_percpu(wq->cpu_wq);
395         kfree(wq);
396 }
397
398 static struct workqueue_struct *keventd_wq;
399
400 int fastcall schedule_work(struct work_struct *work)
401 {
402         return queue_work(keventd_wq, work);
403 }
404
405 int fastcall schedule_delayed_work(struct work_struct *work, unsigned long delay)
406 {
407         return queue_delayed_work(keventd_wq, work, delay);
408 }
409
410 int schedule_delayed_work_on(int cpu,
411                         struct work_struct *work, unsigned long delay)
412 {
413         int ret = 0;
414         struct timer_list *timer = &work->timer;
415
416         if (!test_and_set_bit(0, &work->pending)) {
417                 BUG_ON(timer_pending(timer));
418                 BUG_ON(!list_empty(&work->entry));
419                 /* This stores keventd_wq for the moment, for the timer_fn */
420                 work->wq_data = keventd_wq;
421                 timer->expires = jiffies + delay;
422                 timer->data = (unsigned long)work;
423                 timer->function = delayed_work_timer_fn;
424                 add_timer_on(timer, cpu);
425                 ret = 1;
426         }
427         return ret;
428 }
429
430 int schedule_on_each_cpu(void (*func) (void *info), void *info)
431 {
432         int cpu;
433         struct work_struct *work;
434
435         work = kmalloc(NR_CPUS * sizeof(struct work_struct), GFP_KERNEL);
436
437         if (!work)
438                 return -ENOMEM;
439         for_each_online_cpu(cpu) {
440                 INIT_WORK(work + cpu, func, info);
441                 __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),
442                                 work + cpu);
443         }
444         flush_workqueue(keventd_wq);
445         kfree(work);
446         return 0;
447 }
448
449 void flush_scheduled_work(void)
450 {
451         flush_workqueue(keventd_wq);
452 }
453
454 /**
455  * cancel_rearming_delayed_workqueue - reliably kill off a delayed
456  *                      work whose handler rearms the delayed work.
457  * @wq:   the controlling workqueue structure
458  * @work: the delayed work struct
459  */
460 void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
461                                        struct work_struct *work)
462 {
463         while (!cancel_delayed_work(work))
464                 flush_workqueue(wq);
465 }
466 EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
467
468 /**
469  * cancel_rearming_delayed_work - reliably kill off a delayed keventd
470  *                      work whose handler rearms the delayed work.
471  * @work: the delayed work struct
472  */
473 void cancel_rearming_delayed_work(struct work_struct *work)
474 {
475         cancel_rearming_delayed_workqueue(keventd_wq, work);
476 }
477 EXPORT_SYMBOL(cancel_rearming_delayed_work);
478
479 int keventd_up(void)
480 {
481         return keventd_wq != NULL;
482 }
483
484 int current_is_keventd(void)
485 {
486         struct cpu_workqueue_struct *cwq;
487         int cpu = smp_processor_id();   /* preempt-safe: keventd is per-cpu */
488         int ret = 0;
489
490         BUG_ON(!keventd_wq);
491
492         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
493         if (current == cwq->thread)
494                 ret = 1;
495
496         return ret;
497
498 }
499
500 #ifdef CONFIG_HOTPLUG_CPU
501 /* Take the work from this (downed) CPU. */
502 static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
503 {
504         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
505         LIST_HEAD(list);
506         struct work_struct *work;
507
508         spin_lock_irq(&cwq->lock);
509         list_splice_init(&cwq->worklist, &list);
510
511         while (!list_empty(&list)) {
512                 printk("Taking work for %s\n", wq->name);
513                 work = list_entry(list.next,struct work_struct,entry);
514                 list_del(&work->entry);
515                 __queue_work(per_cpu_ptr(wq->cpu_wq, smp_processor_id()), work);
516         }
517         spin_unlock_irq(&cwq->lock);
518 }
519
520 /* We're holding the cpucontrol mutex here */
521 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
522                                   unsigned long action,
523                                   void *hcpu)
524 {
525         unsigned int hotcpu = (unsigned long)hcpu;
526         struct workqueue_struct *wq;
527
528         switch (action) {
529         case CPU_UP_PREPARE:
530                 /* Create a new workqueue thread for it. */
531                 list_for_each_entry(wq, &workqueues, list) {
532                         if (!create_workqueue_thread(wq, hotcpu)) {
533                                 printk("workqueue for %i failed\n", hotcpu);
534                                 return NOTIFY_BAD;
535                         }
536                 }
537                 break;
538
539         case CPU_ONLINE:
540                 /* Kick off worker threads. */
541                 list_for_each_entry(wq, &workqueues, list) {
542                         struct cpu_workqueue_struct *cwq;
543
544                         cwq = per_cpu_ptr(wq->cpu_wq, hotcpu);
545                         kthread_bind(cwq->thread, hotcpu);
546                         wake_up_process(cwq->thread);
547                 }
548                 break;
549
550         case CPU_UP_CANCELED:
551                 list_for_each_entry(wq, &workqueues, list) {
552                         /* Unbind so it can run. */
553                         kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,
554                                      any_online_cpu(cpu_online_map));
555                         cleanup_workqueue_thread(wq, hotcpu);
556                 }
557                 break;
558
559         case CPU_DEAD:
560                 list_for_each_entry(wq, &workqueues, list)
561                         cleanup_workqueue_thread(wq, hotcpu);
562                 list_for_each_entry(wq, &workqueues, list)
563                         take_over_work(wq, hotcpu);
564                 break;
565         }
566
567         return NOTIFY_OK;
568 }
569 #endif
570
571 void init_workqueues(void)
572 {
573         singlethread_cpu = first_cpu(cpu_possible_map);
574         hotcpu_notifier(workqueue_cpu_callback, 0);
575         keventd_wq = create_workqueue("events");
576         BUG_ON(!keventd_wq);
577 }
578
579 EXPORT_SYMBOL_GPL(__create_workqueue);
580 EXPORT_SYMBOL_GPL(queue_work);
581 EXPORT_SYMBOL_GPL(queue_delayed_work);
582 EXPORT_SYMBOL_GPL(flush_workqueue);
583 EXPORT_SYMBOL_GPL(destroy_workqueue);
584
585 EXPORT_SYMBOL(schedule_work);
586 EXPORT_SYMBOL(schedule_delayed_work);
587 EXPORT_SYMBOL(schedule_delayed_work_on);
588 EXPORT_SYMBOL(flush_scheduled_work);