projects/linux·blob v4.11-rc5 · refs

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1/* Kernel thread helper functions.
2 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
3 *
4 * Creation is done via kthreadd, so that we get a clean environment
5 * even if we're invoked from userspace (think modprobe, hotplug cpu,
6 * etc.).
7 */
8#include <uapi/linux/sched/types.h>
9#include <linux/sched.h>
10#include <linux/sched/task.h>
11#include <linux/kthread.h>
12#include <linux/completion.h>
13#include <linux/err.h>
14#include <linux/cpuset.h>
15#include <linux/unistd.h>
16#include <linux/file.h>
17#include <linux/export.h>
18#include <linux/mutex.h>
19#include <linux/slab.h>
20#include <linux/freezer.h>
21#include <linux/ptrace.h>
22#include <linux/uaccess.h>
23#include <trace/events/sched.h>
24
25static DEFINE_SPINLOCK(kthread_create_lock);
26static LIST_HEAD(kthread_create_list);
27struct task_struct *kthreadd_task;
28
29struct kthread_create_info
30{
31 /* Information passed to kthread() from kthreadd. */
32 int (*threadfn)(void *data);
33 void *data;
34 int node;
35
36 /* Result passed back to kthread_create() from kthreadd. */
37 struct task_struct *result;
38 struct completion *done;
39
40 struct list_head list;
41};
42
43struct kthread {
44 unsigned long flags;
45 unsigned int cpu;
46 void *data;
47 struct completion parked;
48 struct completion exited;
49};
50
51enum KTHREAD_BITS {
52 KTHREAD_IS_PER_CPU = 0,
53 KTHREAD_SHOULD_STOP,
54 KTHREAD_SHOULD_PARK,
55 KTHREAD_IS_PARKED,
56};
57
58static inline void set_kthread_struct(void *kthread)
59{
60 /*
61 * We abuse ->set_child_tid to avoid the new member and because it
62 * can't be wrongly copied by copy_process(). We also rely on fact
63 * that the caller can't exec, so PF_KTHREAD can't be cleared.
64 */
65 current->set_child_tid = (__force void __user *)kthread;
66}
67
68static inline struct kthread *to_kthread(struct task_struct *k)
69{
70 WARN_ON(!(k->flags & PF_KTHREAD));
71 return (__force void *)k->set_child_tid;
72}
73
74void free_kthread_struct(struct task_struct *k)
75{
76 /*
77 * Can be NULL if this kthread was created by kernel_thread()
78 * or if kmalloc() in kthread() failed.
79 */
80 kfree(to_kthread(k));
81}
82
83/**
84 * kthread_should_stop - should this kthread return now?
85 *
86 * When someone calls kthread_stop() on your kthread, it will be woken
87 * and this will return true. You should then return, and your return
88 * value will be passed through to kthread_stop().
89 */
90bool kthread_should_stop(void)
91{
92 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
93}
94EXPORT_SYMBOL(kthread_should_stop);
95
96/**
97 * kthread_should_park - should this kthread park now?
98 *
99 * When someone calls kthread_park() on your kthread, it will be woken
100 * and this will return true. You should then do the necessary
101 * cleanup and call kthread_parkme()
102 *
103 * Similar to kthread_should_stop(), but this keeps the thread alive
104 * and in a park position. kthread_unpark() "restarts" the thread and
105 * calls the thread function again.
106 */
107bool kthread_should_park(void)
108{
109 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
110}
111EXPORT_SYMBOL_GPL(kthread_should_park);
112
113/**
114 * kthread_freezable_should_stop - should this freezable kthread return now?
115 * @was_frozen: optional out parameter, indicates whether %current was frozen
116 *
117 * kthread_should_stop() for freezable kthreads, which will enter
118 * refrigerator if necessary. This function is safe from kthread_stop() /
119 * freezer deadlock and freezable kthreads should use this function instead
120 * of calling try_to_freeze() directly.
121 */
122bool kthread_freezable_should_stop(bool *was_frozen)
123{
124 bool frozen = false;
125
126 might_sleep();
127
128 if (unlikely(freezing(current)))
129 frozen = __refrigerator(true);
130
131 if (was_frozen)
132 *was_frozen = frozen;
133
134 return kthread_should_stop();
135}
136EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
137
138/**
139 * kthread_data - return data value specified on kthread creation
140 * @task: kthread task in question
141 *
142 * Return the data value specified when kthread @task was created.
143 * The caller is responsible for ensuring the validity of @task when
144 * calling this function.
145 */
146void *kthread_data(struct task_struct *task)
147{
148 return to_kthread(task)->data;
149}
150
151/**
152 * kthread_probe_data - speculative version of kthread_data()
153 * @task: possible kthread task in question
154 *
155 * @task could be a kthread task. Return the data value specified when it
156 * was created if accessible. If @task isn't a kthread task or its data is
157 * inaccessible for any reason, %NULL is returned. This function requires
158 * that @task itself is safe to dereference.
159 */
160void *kthread_probe_data(struct task_struct *task)
161{
162 struct kthread *kthread = to_kthread(task);
163 void *data = NULL;
164
165 probe_kernel_read(&data, &kthread->data, sizeof(data));
166 return data;
167}
168
169static void __kthread_parkme(struct kthread *self)
170{
171 __set_current_state(TASK_PARKED);
172 while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) {
173 if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags))
174 complete(&self->parked);
175 schedule();
176 __set_current_state(TASK_PARKED);
177 }
178 clear_bit(KTHREAD_IS_PARKED, &self->flags);
179 __set_current_state(TASK_RUNNING);
180}
181
182void kthread_parkme(void)
183{
184 __kthread_parkme(to_kthread(current));
185}
186EXPORT_SYMBOL_GPL(kthread_parkme);
187
188static int kthread(void *_create)
189{
190 /* Copy data: it's on kthread's stack */
191 struct kthread_create_info *create = _create;
192 int (*threadfn)(void *data) = create->threadfn;
193 void *data = create->data;
194 struct completion *done;
195 struct kthread *self;
196 int ret;
197
198 self = kmalloc(sizeof(*self), GFP_KERNEL);
199 set_kthread_struct(self);
200
201 /* If user was SIGKILLed, I release the structure. */
202 done = xchg(&create->done, NULL);
203 if (!done) {
204 kfree(create);
205 do_exit(-EINTR);
206 }
207
208 if (!self) {
209 create->result = ERR_PTR(-ENOMEM);
210 complete(done);
211 do_exit(-ENOMEM);
212 }
213
214 self->flags = 0;
215 self->data = data;
216 init_completion(&self->exited);
217 init_completion(&self->parked);
218 current->vfork_done = &self->exited;
219
220 /* OK, tell user we're spawned, wait for stop or wakeup */
221 __set_current_state(TASK_UNINTERRUPTIBLE);
222 create->result = current;
223 complete(done);
224 schedule();
225
226 ret = -EINTR;
227 if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
228 __kthread_parkme(self);
229 ret = threadfn(data);
230 }
231 do_exit(ret);
232}
233
234/* called from do_fork() to get node information for about to be created task */
235int tsk_fork_get_node(struct task_struct *tsk)
236{
237#ifdef CONFIG_NUMA
238 if (tsk == kthreadd_task)
239 return tsk->pref_node_fork;
240#endif
241 return NUMA_NO_NODE;
242}
243
244static void create_kthread(struct kthread_create_info *create)
245{
246 int pid;
247
248#ifdef CONFIG_NUMA
249 current->pref_node_fork = create->node;
250#endif
251 /* We want our own signal handler (we take no signals by default). */
252 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
253 if (pid < 0) {
254 /* If user was SIGKILLed, I release the structure. */
255 struct completion *done = xchg(&create->done, NULL);
256
257 if (!done) {
258 kfree(create);
259 return;
260 }
261 create->result = ERR_PTR(pid);
262 complete(done);
263 }
264}
265
266static __printf(4, 0)
267struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
268 void *data, int node,
269 const char namefmt[],
270 va_list args)
271{
272 DECLARE_COMPLETION_ONSTACK(done);
273 struct task_struct *task;
274 struct kthread_create_info *create = kmalloc(sizeof(*create),
275 GFP_KERNEL);
276
277 if (!create)
278 return ERR_PTR(-ENOMEM);
279 create->threadfn = threadfn;
280 create->data = data;
281 create->node = node;
282 create->done = &done;
283
284 spin_lock(&kthread_create_lock);
285 list_add_tail(&create->list, &kthread_create_list);
286 spin_unlock(&kthread_create_lock);
287
288 wake_up_process(kthreadd_task);
289 /*
290 * Wait for completion in killable state, for I might be chosen by
291 * the OOM killer while kthreadd is trying to allocate memory for
292 * new kernel thread.
293 */
294 if (unlikely(wait_for_completion_killable(&done))) {
295 /*
296 * If I was SIGKILLed before kthreadd (or new kernel thread)
297 * calls complete(), leave the cleanup of this structure to
298 * that thread.
299 */
300 if (xchg(&create->done, NULL))
301 return ERR_PTR(-EINTR);
302 /*
303 * kthreadd (or new kernel thread) will call complete()
304 * shortly.
305 */
306 wait_for_completion(&done);
307 }
308 task = create->result;
309 if (!IS_ERR(task)) {
310 static const struct sched_param param = { .sched_priority = 0 };
311
312 vsnprintf(task->comm, sizeof(task->comm), namefmt, args);
313 /*
314 * root may have changed our (kthreadd's) priority or CPU mask.
315 * The kernel thread should not inherit these properties.
316 */
317 sched_setscheduler_nocheck(task, SCHED_NORMAL, &param);
318 set_cpus_allowed_ptr(task, cpu_all_mask);
319 }
320 kfree(create);
321 return task;
322}
323
324/**
325 * kthread_create_on_node - create a kthread.
326 * @threadfn: the function to run until signal_pending(current).
327 * @data: data ptr for @threadfn.
328 * @node: task and thread structures for the thread are allocated on this node
329 * @namefmt: printf-style name for the thread.
330 *
331 * Description: This helper function creates and names a kernel
332 * thread. The thread will be stopped: use wake_up_process() to start
333 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
334 * is affine to all CPUs.
335 *
336 * If thread is going to be bound on a particular cpu, give its node
337 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
338 * When woken, the thread will run @threadfn() with @data as its
339 * argument. @threadfn() can either call do_exit() directly if it is a
340 * standalone thread for which no one will call kthread_stop(), or
341 * return when 'kthread_should_stop()' is true (which means
342 * kthread_stop() has been called). The return value should be zero
343 * or a negative error number; it will be passed to kthread_stop().
344 *
345 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
346 */
347struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
348 void *data, int node,
349 const char namefmt[],
350 ...)
351{
352 struct task_struct *task;
353 va_list args;
354
355 va_start(args, namefmt);
356 task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
357 va_end(args);
358
359 return task;
360}
361EXPORT_SYMBOL(kthread_create_on_node);
362
363static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
364{
365 unsigned long flags;
366
367 if (!wait_task_inactive(p, state)) {
368 WARN_ON(1);
369 return;
370 }
371
372 /* It's safe because the task is inactive. */
373 raw_spin_lock_irqsave(&p->pi_lock, flags);
374 do_set_cpus_allowed(p, mask);
375 p->flags |= PF_NO_SETAFFINITY;
376 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
377}
378
379static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
380{
381 __kthread_bind_mask(p, cpumask_of(cpu), state);
382}
383
384void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
385{
386 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
387}
388
389/**
390 * kthread_bind - bind a just-created kthread to a cpu.
391 * @p: thread created by kthread_create().
392 * @cpu: cpu (might not be online, must be possible) for @k to run on.
393 *
394 * Description: This function is equivalent to set_cpus_allowed(),
395 * except that @cpu doesn't need to be online, and the thread must be
396 * stopped (i.e., just returned from kthread_create()).
397 */
398void kthread_bind(struct task_struct *p, unsigned int cpu)
399{
400 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
401}
402EXPORT_SYMBOL(kthread_bind);
403
404/**
405 * kthread_create_on_cpu - Create a cpu bound kthread
406 * @threadfn: the function to run until signal_pending(current).
407 * @data: data ptr for @threadfn.
408 * @cpu: The cpu on which the thread should be bound,
409 * @namefmt: printf-style name for the thread. Format is restricted
410 * to "name.*%u". Code fills in cpu number.
411 *
412 * Description: This helper function creates and names a kernel thread
413 * The thread will be woken and put into park mode.
414 */
415struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
416 void *data, unsigned int cpu,
417 const char *namefmt)
418{
419 struct task_struct *p;
420
421 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
422 cpu);
423 if (IS_ERR(p))
424 return p;
425 kthread_bind(p, cpu);
426 /* CPU hotplug need to bind once again when unparking the thread. */
427 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
428 to_kthread(p)->cpu = cpu;
429 return p;
430}
431
432/**
433 * kthread_unpark - unpark a thread created by kthread_create().
434 * @k: thread created by kthread_create().
435 *
436 * Sets kthread_should_park() for @k to return false, wakes it, and
437 * waits for it to return. If the thread is marked percpu then its
438 * bound to the cpu again.
439 */
440void kthread_unpark(struct task_struct *k)
441{
442 struct kthread *kthread = to_kthread(k);
443
444 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
445 /*
446 * We clear the IS_PARKED bit here as we don't wait
447 * until the task has left the park code. So if we'd
448 * park before that happens we'd see the IS_PARKED bit
449 * which might be about to be cleared.
450 */
451 if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
452 /*
453 * Newly created kthread was parked when the CPU was offline.
454 * The binding was lost and we need to set it again.
455 */
456 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
457 __kthread_bind(k, kthread->cpu, TASK_PARKED);
458 wake_up_state(k, TASK_PARKED);
459 }
460}
461EXPORT_SYMBOL_GPL(kthread_unpark);
462
463/**
464 * kthread_park - park a thread created by kthread_create().
465 * @k: thread created by kthread_create().
466 *
467 * Sets kthread_should_park() for @k to return true, wakes it, and
468 * waits for it to return. This can also be called after kthread_create()
469 * instead of calling wake_up_process(): the thread will park without
470 * calling threadfn().
471 *
472 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
473 * If called by the kthread itself just the park bit is set.
474 */
475int kthread_park(struct task_struct *k)
476{
477 struct kthread *kthread = to_kthread(k);
478
479 if (WARN_ON(k->flags & PF_EXITING))
480 return -ENOSYS;
481
482 if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
483 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
484 if (k != current) {
485 wake_up_process(k);
486 wait_for_completion(&kthread->parked);
487 }
488 }
489
490 return 0;
491}
492EXPORT_SYMBOL_GPL(kthread_park);
493
494/**
495 * kthread_stop - stop a thread created by kthread_create().
496 * @k: thread created by kthread_create().
497 *
498 * Sets kthread_should_stop() for @k to return true, wakes it, and
499 * waits for it to exit. This can also be called after kthread_create()
500 * instead of calling wake_up_process(): the thread will exit without
501 * calling threadfn().
502 *
503 * If threadfn() may call do_exit() itself, the caller must ensure
504 * task_struct can't go away.
505 *
506 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
507 * was never called.
508 */
509int kthread_stop(struct task_struct *k)
510{
511 struct kthread *kthread;
512 int ret;
513
514 trace_sched_kthread_stop(k);
515
516 get_task_struct(k);
517 kthread = to_kthread(k);
518 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
519 kthread_unpark(k);
520 wake_up_process(k);
521 wait_for_completion(&kthread->exited);
522 ret = k->exit_code;
523 put_task_struct(k);
524
525 trace_sched_kthread_stop_ret(ret);
526 return ret;
527}
528EXPORT_SYMBOL(kthread_stop);
529
530int kthreadd(void *unused)
531{
532 struct task_struct *tsk = current;
533
534 /* Setup a clean context for our children to inherit. */
535 set_task_comm(tsk, "kthreadd");
536 ignore_signals(tsk);
537 set_cpus_allowed_ptr(tsk, cpu_all_mask);
538 set_mems_allowed(node_states[N_MEMORY]);
539
540 current->flags |= PF_NOFREEZE;
541
542 for (;;) {
543 set_current_state(TASK_INTERRUPTIBLE);
544 if (list_empty(&kthread_create_list))
545 schedule();
546 __set_current_state(TASK_RUNNING);
547
548 spin_lock(&kthread_create_lock);
549 while (!list_empty(&kthread_create_list)) {
550 struct kthread_create_info *create;
551
552 create = list_entry(kthread_create_list.next,
553 struct kthread_create_info, list);
554 list_del_init(&create->list);
555 spin_unlock(&kthread_create_lock);
556
557 create_kthread(create);
558
559 spin_lock(&kthread_create_lock);
560 }
561 spin_unlock(&kthread_create_lock);
562 }
563
564 return 0;
565}
566
567void __kthread_init_worker(struct kthread_worker *worker,
568 const char *name,
569 struct lock_class_key *key)
570{
571 memset(worker, 0, sizeof(struct kthread_worker));
572 spin_lock_init(&worker->lock);
573 lockdep_set_class_and_name(&worker->lock, key, name);
574 INIT_LIST_HEAD(&worker->work_list);
575 INIT_LIST_HEAD(&worker->delayed_work_list);
576}
577EXPORT_SYMBOL_GPL(__kthread_init_worker);
578
579/**
580 * kthread_worker_fn - kthread function to process kthread_worker
581 * @worker_ptr: pointer to initialized kthread_worker
582 *
583 * This function implements the main cycle of kthread worker. It processes
584 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
585 * is empty.
586 *
587 * The works are not allowed to keep any locks, disable preemption or interrupts
588 * when they finish. There is defined a safe point for freezing when one work
589 * finishes and before a new one is started.
590 *
591 * Also the works must not be handled by more than one worker at the same time,
592 * see also kthread_queue_work().
593 */
594int kthread_worker_fn(void *worker_ptr)
595{
596 struct kthread_worker *worker = worker_ptr;
597 struct kthread_work *work;
598
599 /*
600 * FIXME: Update the check and remove the assignment when all kthread
601 * worker users are created using kthread_create_worker*() functions.
602 */
603 WARN_ON(worker->task && worker->task != current);
604 worker->task = current;
605
606 if (worker->flags & KTW_FREEZABLE)
607 set_freezable();
608
609repeat:
610 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
611
612 if (kthread_should_stop()) {
613 __set_current_state(TASK_RUNNING);
614 spin_lock_irq(&worker->lock);
615 worker->task = NULL;
616 spin_unlock_irq(&worker->lock);
617 return 0;
618 }
619
620 work = NULL;
621 spin_lock_irq(&worker->lock);
622 if (!list_empty(&worker->work_list)) {
623 work = list_first_entry(&worker->work_list,
624 struct kthread_work, node);
625 list_del_init(&work->node);
626 }
627 worker->current_work = work;
628 spin_unlock_irq(&worker->lock);
629
630 if (work) {
631 __set_current_state(TASK_RUNNING);
632 work->func(work);
633 } else if (!freezing(current))
634 schedule();
635
636 try_to_freeze();
637 goto repeat;
638}
639EXPORT_SYMBOL_GPL(kthread_worker_fn);
640
641static __printf(3, 0) struct kthread_worker *
642__kthread_create_worker(int cpu, unsigned int flags,
643 const char namefmt[], va_list args)
644{
645 struct kthread_worker *worker;
646 struct task_struct *task;
647 int node = -1;
648
649 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
650 if (!worker)
651 return ERR_PTR(-ENOMEM);
652
653 kthread_init_worker(worker);
654
655 if (cpu >= 0)
656 node = cpu_to_node(cpu);
657
658 task = __kthread_create_on_node(kthread_worker_fn, worker,
659 node, namefmt, args);
660 if (IS_ERR(task))
661 goto fail_task;
662
663 if (cpu >= 0)
664 kthread_bind(task, cpu);
665
666 worker->flags = flags;
667 worker->task = task;
668 wake_up_process(task);
669 return worker;
670
671fail_task:
672 kfree(worker);
673 return ERR_CAST(task);
674}
675
676/**
677 * kthread_create_worker - create a kthread worker
678 * @flags: flags modifying the default behavior of the worker
679 * @namefmt: printf-style name for the kthread worker (task).
680 *
681 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
682 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
683 * when the worker was SIGKILLed.
684 */
685struct kthread_worker *
686kthread_create_worker(unsigned int flags, const char namefmt[], ...)
687{
688 struct kthread_worker *worker;
689 va_list args;
690
691 va_start(args, namefmt);
692 worker = __kthread_create_worker(-1, flags, namefmt, args);
693 va_end(args);
694
695 return worker;
696}
697EXPORT_SYMBOL(kthread_create_worker);
698
699/**
700 * kthread_create_worker_on_cpu - create a kthread worker and bind it
701 * it to a given CPU and the associated NUMA node.
702 * @cpu: CPU number
703 * @flags: flags modifying the default behavior of the worker
704 * @namefmt: printf-style name for the kthread worker (task).
705 *
706 * Use a valid CPU number if you want to bind the kthread worker
707 * to the given CPU and the associated NUMA node.
708 *
709 * A good practice is to add the cpu number also into the worker name.
710 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
711 *
712 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
713 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
714 * when the worker was SIGKILLed.
715 */
716struct kthread_worker *
717kthread_create_worker_on_cpu(int cpu, unsigned int flags,
718 const char namefmt[], ...)
719{
720 struct kthread_worker *worker;
721 va_list args;
722
723 va_start(args, namefmt);
724 worker = __kthread_create_worker(cpu, flags, namefmt, args);
725 va_end(args);
726
727 return worker;
728}
729EXPORT_SYMBOL(kthread_create_worker_on_cpu);
730
731/*
732 * Returns true when the work could not be queued at the moment.
733 * It happens when it is already pending in a worker list
734 * or when it is being cancelled.
735 */
736static inline bool queuing_blocked(struct kthread_worker *worker,
737 struct kthread_work *work)
738{
739 lockdep_assert_held(&worker->lock);
740
741 return !list_empty(&work->node) || work->canceling;
742}
743
744static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
745 struct kthread_work *work)
746{
747 lockdep_assert_held(&worker->lock);
748 WARN_ON_ONCE(!list_empty(&work->node));
749 /* Do not use a work with >1 worker, see kthread_queue_work() */
750 WARN_ON_ONCE(work->worker && work->worker != worker);
751}
752
753/* insert @work before @pos in @worker */
754static void kthread_insert_work(struct kthread_worker *worker,
755 struct kthread_work *work,
756 struct list_head *pos)
757{
758 kthread_insert_work_sanity_check(worker, work);
759
760 list_add_tail(&work->node, pos);
761 work->worker = worker;
762 if (!worker->current_work && likely(worker->task))
763 wake_up_process(worker->task);
764}
765
766/**
767 * kthread_queue_work - queue a kthread_work
768 * @worker: target kthread_worker
769 * @work: kthread_work to queue
770 *
771 * Queue @work to work processor @task for async execution. @task
772 * must have been created with kthread_worker_create(). Returns %true
773 * if @work was successfully queued, %false if it was already pending.
774 *
775 * Reinitialize the work if it needs to be used by another worker.
776 * For example, when the worker was stopped and started again.
777 */
778bool kthread_queue_work(struct kthread_worker *worker,
779 struct kthread_work *work)
780{
781 bool ret = false;
782 unsigned long flags;
783
784 spin_lock_irqsave(&worker->lock, flags);
785 if (!queuing_blocked(worker, work)) {
786 kthread_insert_work(worker, work, &worker->work_list);
787 ret = true;
788 }
789 spin_unlock_irqrestore(&worker->lock, flags);
790 return ret;
791}
792EXPORT_SYMBOL_GPL(kthread_queue_work);
793
794/**
795 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
796 * delayed work when the timer expires.
797 * @__data: pointer to the data associated with the timer
798 *
799 * The format of the function is defined by struct timer_list.
800 * It should have been called from irqsafe timer with irq already off.
801 */
802void kthread_delayed_work_timer_fn(unsigned long __data)
803{
804 struct kthread_delayed_work *dwork =
805 (struct kthread_delayed_work *)__data;
806 struct kthread_work *work = &dwork->work;
807 struct kthread_worker *worker = work->worker;
808
809 /*
810 * This might happen when a pending work is reinitialized.
811 * It means that it is used a wrong way.
812 */
813 if (WARN_ON_ONCE(!worker))
814 return;
815
816 spin_lock(&worker->lock);
817 /* Work must not be used with >1 worker, see kthread_queue_work(). */
818 WARN_ON_ONCE(work->worker != worker);
819
820 /* Move the work from worker->delayed_work_list. */
821 WARN_ON_ONCE(list_empty(&work->node));
822 list_del_init(&work->node);
823 kthread_insert_work(worker, work, &worker->work_list);
824
825 spin_unlock(&worker->lock);
826}
827EXPORT_SYMBOL(kthread_delayed_work_timer_fn);
828
829void __kthread_queue_delayed_work(struct kthread_worker *worker,
830 struct kthread_delayed_work *dwork,
831 unsigned long delay)
832{
833 struct timer_list *timer = &dwork->timer;
834 struct kthread_work *work = &dwork->work;
835
836 WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn ||
837 timer->data != (unsigned long)dwork);
838
839 /*
840 * If @delay is 0, queue @dwork->work immediately. This is for
841 * both optimization and correctness. The earliest @timer can
842 * expire is on the closest next tick and delayed_work users depend
843 * on that there's no such delay when @delay is 0.
844 */
845 if (!delay) {
846 kthread_insert_work(worker, work, &worker->work_list);
847 return;
848 }
849
850 /* Be paranoid and try to detect possible races already now. */
851 kthread_insert_work_sanity_check(worker, work);
852
853 list_add(&work->node, &worker->delayed_work_list);
854 work->worker = worker;
855 timer->expires = jiffies + delay;
856 add_timer(timer);
857}
858
859/**
860 * kthread_queue_delayed_work - queue the associated kthread work
861 * after a delay.
862 * @worker: target kthread_worker
863 * @dwork: kthread_delayed_work to queue
864 * @delay: number of jiffies to wait before queuing
865 *
866 * If the work has not been pending it starts a timer that will queue
867 * the work after the given @delay. If @delay is zero, it queues the
868 * work immediately.
869 *
870 * Return: %false if the @work has already been pending. It means that
871 * either the timer was running or the work was queued. It returns %true
872 * otherwise.
873 */
874bool kthread_queue_delayed_work(struct kthread_worker *worker,
875 struct kthread_delayed_work *dwork,
876 unsigned long delay)
877{
878 struct kthread_work *work = &dwork->work;
879 unsigned long flags;
880 bool ret = false;
881
882 spin_lock_irqsave(&worker->lock, flags);
883
884 if (!queuing_blocked(worker, work)) {
885 __kthread_queue_delayed_work(worker, dwork, delay);
886 ret = true;
887 }
888
889 spin_unlock_irqrestore(&worker->lock, flags);
890 return ret;
891}
892EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
893
894struct kthread_flush_work {
895 struct kthread_work work;
896 struct completion done;
897};
898
899static void kthread_flush_work_fn(struct kthread_work *work)
900{
901 struct kthread_flush_work *fwork =
902 container_of(work, struct kthread_flush_work, work);
903 complete(&fwork->done);
904}
905
906/**
907 * kthread_flush_work - flush a kthread_work
908 * @work: work to flush
909 *
910 * If @work is queued or executing, wait for it to finish execution.
911 */
912void kthread_flush_work(struct kthread_work *work)
913{
914 struct kthread_flush_work fwork = {
915 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
916 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
917 };
918 struct kthread_worker *worker;
919 bool noop = false;
920
921 worker = work->worker;
922 if (!worker)
923 return;
924
925 spin_lock_irq(&worker->lock);
926 /* Work must not be used with >1 worker, see kthread_queue_work(). */
927 WARN_ON_ONCE(work->worker != worker);
928
929 if (!list_empty(&work->node))
930 kthread_insert_work(worker, &fwork.work, work->node.next);
931 else if (worker->current_work == work)
932 kthread_insert_work(worker, &fwork.work,
933 worker->work_list.next);
934 else
935 noop = true;
936
937 spin_unlock_irq(&worker->lock);
938
939 if (!noop)
940 wait_for_completion(&fwork.done);
941}
942EXPORT_SYMBOL_GPL(kthread_flush_work);
943
944/*
945 * This function removes the work from the worker queue. Also it makes sure
946 * that it won't get queued later via the delayed work's timer.
947 *
948 * The work might still be in use when this function finishes. See the
949 * current_work proceed by the worker.
950 *
951 * Return: %true if @work was pending and successfully canceled,
952 * %false if @work was not pending
953 */
954static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
955 unsigned long *flags)
956{
957 /* Try to cancel the timer if exists. */
958 if (is_dwork) {
959 struct kthread_delayed_work *dwork =
960 container_of(work, struct kthread_delayed_work, work);
961 struct kthread_worker *worker = work->worker;
962
963 /*
964 * del_timer_sync() must be called to make sure that the timer
965 * callback is not running. The lock must be temporary released
966 * to avoid a deadlock with the callback. In the meantime,
967 * any queuing is blocked by setting the canceling counter.
968 */
969 work->canceling++;
970 spin_unlock_irqrestore(&worker->lock, *flags);
971 del_timer_sync(&dwork->timer);
972 spin_lock_irqsave(&worker->lock, *flags);
973 work->canceling--;
974 }
975
976 /*
977 * Try to remove the work from a worker list. It might either
978 * be from worker->work_list or from worker->delayed_work_list.
979 */
980 if (!list_empty(&work->node)) {
981 list_del_init(&work->node);
982 return true;
983 }
984
985 return false;
986}
987
988/**
989 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
990 * @worker: kthread worker to use
991 * @dwork: kthread delayed work to queue
992 * @delay: number of jiffies to wait before queuing
993 *
994 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
995 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
996 * @work is guaranteed to be queued immediately.
997 *
998 * Return: %true if @dwork was pending and its timer was modified,
999 * %false otherwise.
1000 *
1001 * A special case is when the work is being canceled in parallel.
1002 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1003 * or yet another kthread_mod_delayed_work() call. We let the other command
1004 * win and return %false here. The caller is supposed to synchronize these
1005 * operations a reasonable way.
1006 *
1007 * This function is safe to call from any context including IRQ handler.
1008 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1009 * for details.
1010 */
1011bool kthread_mod_delayed_work(struct kthread_worker *worker,
1012 struct kthread_delayed_work *dwork,
1013 unsigned long delay)
1014{
1015 struct kthread_work *work = &dwork->work;
1016 unsigned long flags;
1017 int ret = false;
1018
1019 spin_lock_irqsave(&worker->lock, flags);
1020
1021 /* Do not bother with canceling when never queued. */
1022 if (!work->worker)
1023 goto fast_queue;
1024
1025 /* Work must not be used with >1 worker, see kthread_queue_work() */
1026 WARN_ON_ONCE(work->worker != worker);
1027
1028 /* Do not fight with another command that is canceling this work. */
1029 if (work->canceling)
1030 goto out;
1031
1032 ret = __kthread_cancel_work(work, true, &flags);
1033fast_queue:
1034 __kthread_queue_delayed_work(worker, dwork, delay);
1035out:
1036 spin_unlock_irqrestore(&worker->lock, flags);
1037 return ret;
1038}
1039EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1040
1041static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1042{
1043 struct kthread_worker *worker = work->worker;
1044 unsigned long flags;
1045 int ret = false;
1046
1047 if (!worker)
1048 goto out;
1049
1050 spin_lock_irqsave(&worker->lock, flags);
1051 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1052 WARN_ON_ONCE(work->worker != worker);
1053
1054 ret = __kthread_cancel_work(work, is_dwork, &flags);
1055
1056 if (worker->current_work != work)
1057 goto out_fast;
1058
1059 /*
1060 * The work is in progress and we need to wait with the lock released.
1061 * In the meantime, block any queuing by setting the canceling counter.
1062 */
1063 work->canceling++;
1064 spin_unlock_irqrestore(&worker->lock, flags);
1065 kthread_flush_work(work);
1066 spin_lock_irqsave(&worker->lock, flags);
1067 work->canceling--;
1068
1069out_fast:
1070 spin_unlock_irqrestore(&worker->lock, flags);
1071out:
1072 return ret;
1073}
1074
1075/**
1076 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1077 * @work: the kthread work to cancel
1078 *
1079 * Cancel @work and wait for its execution to finish. This function
1080 * can be used even if the work re-queues itself. On return from this
1081 * function, @work is guaranteed to be not pending or executing on any CPU.
1082 *
1083 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1084 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1085 *
1086 * The caller must ensure that the worker on which @work was last
1087 * queued can't be destroyed before this function returns.
1088 *
1089 * Return: %true if @work was pending, %false otherwise.
1090 */
1091bool kthread_cancel_work_sync(struct kthread_work *work)
1092{
1093 return __kthread_cancel_work_sync(work, false);
1094}
1095EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1096
1097/**
1098 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1099 * wait for it to finish.
1100 * @dwork: the kthread delayed work to cancel
1101 *
1102 * This is kthread_cancel_work_sync() for delayed works.
1103 *
1104 * Return: %true if @dwork was pending, %false otherwise.
1105 */
1106bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1107{
1108 return __kthread_cancel_work_sync(&dwork->work, true);
1109}
1110EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1111
1112/**
1113 * kthread_flush_worker - flush all current works on a kthread_worker
1114 * @worker: worker to flush
1115 *
1116 * Wait until all currently executing or pending works on @worker are
1117 * finished.
1118 */
1119void kthread_flush_worker(struct kthread_worker *worker)
1120{
1121 struct kthread_flush_work fwork = {
1122 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1123 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1124 };
1125
1126 kthread_queue_work(worker, &fwork.work);
1127 wait_for_completion(&fwork.done);
1128}
1129EXPORT_SYMBOL_GPL(kthread_flush_worker);
1130
1131/**
1132 * kthread_destroy_worker - destroy a kthread worker
1133 * @worker: worker to be destroyed
1134 *
1135 * Flush and destroy @worker. The simple flush is enough because the kthread
1136 * worker API is used only in trivial scenarios. There are no multi-step state
1137 * machines needed.
1138 */
1139void kthread_destroy_worker(struct kthread_worker *worker)
1140{
1141 struct task_struct *task;
1142
1143 task = worker->task;
1144 if (WARN_ON(!task))
1145 return;
1146
1147 kthread_flush_worker(worker);
1148 kthread_stop(task);
1149 WARN_ON(!list_empty(&worker->work_list));
1150 kfree(worker);
1151}
1152EXPORT_SYMBOL(kthread_destroy_worker);