1 /* Kernel thread helper functions.
2 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
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,
8 #include <linux/sched.h>
9 #include <linux/kthread.h>
10 #include <linux/completion.h>
11 #include <linux/err.h>
12 #include <linux/cpuset.h>
13 #include <linux/unistd.h>
14 #include <linux/file.h>
15 #include <linux/export.h>
16 #include <linux/mutex.h>
17 #include <linux/slab.h>
18 #include <linux/freezer.h>
19 #include <linux/ptrace.h>
20 #include <linux/uaccess.h>
21 #include <trace/events/sched.h>
23 static DEFINE_SPINLOCK(kthread_create_lock);
24 static LIST_HEAD(kthread_create_list);
25 struct task_struct *kthreadd_task;
27 struct kthread_create_info
29 /* Information passed to kthread() from kthreadd. */
30 int (*threadfn)(void *data);
34 /* Result passed back to kthread_create() from kthreadd. */
35 struct task_struct *result;
36 struct completion *done;
38 struct list_head list;
45 struct completion parked;
46 struct completion exited;
50 KTHREAD_IS_PER_CPU = 0,
56 #define __to_kthread(vfork) \
57 container_of(vfork, struct kthread, exited)
59 static inline struct kthread *to_kthread(struct task_struct *k)
61 return __to_kthread(k->vfork_done);
64 static struct kthread *to_live_kthread(struct task_struct *k)
66 struct completion *vfork = ACCESS_ONCE(k->vfork_done);
67 if (likely(vfork) && try_get_task_stack(k))
68 return __to_kthread(vfork);
73 * kthread_should_stop - should this kthread return now?
75 * When someone calls kthread_stop() on your kthread, it will be woken
76 * and this will return true. You should then return, and your return
77 * value will be passed through to kthread_stop().
79 bool kthread_should_stop(void)
81 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
83 EXPORT_SYMBOL(kthread_should_stop);
86 * kthread_should_park - should this kthread park now?
88 * When someone calls kthread_park() on your kthread, it will be woken
89 * and this will return true. You should then do the necessary
90 * cleanup and call kthread_parkme()
92 * Similar to kthread_should_stop(), but this keeps the thread alive
93 * and in a park position. kthread_unpark() "restarts" the thread and
94 * calls the thread function again.
96 bool kthread_should_park(void)
98 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
100 EXPORT_SYMBOL_GPL(kthread_should_park);
103 * kthread_freezable_should_stop - should this freezable kthread return now?
104 * @was_frozen: optional out parameter, indicates whether %current was frozen
106 * kthread_should_stop() for freezable kthreads, which will enter
107 * refrigerator if necessary. This function is safe from kthread_stop() /
108 * freezer deadlock and freezable kthreads should use this function instead
109 * of calling try_to_freeze() directly.
111 bool kthread_freezable_should_stop(bool *was_frozen)
117 if (unlikely(freezing(current)))
118 frozen = __refrigerator(true);
121 *was_frozen = frozen;
123 return kthread_should_stop();
125 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
128 * kthread_data - return data value specified on kthread creation
129 * @task: kthread task in question
131 * Return the data value specified when kthread @task was created.
132 * The caller is responsible for ensuring the validity of @task when
133 * calling this function.
135 void *kthread_data(struct task_struct *task)
137 return to_kthread(task)->data;
141 * kthread_probe_data - speculative version of kthread_data()
142 * @task: possible kthread task in question
144 * @task could be a kthread task. Return the data value specified when it
145 * was created if accessible. If @task isn't a kthread task or its data is
146 * inaccessible for any reason, %NULL is returned. This function requires
147 * that @task itself is safe to dereference.
149 void *kthread_probe_data(struct task_struct *task)
151 struct kthread *kthread = to_kthread(task);
154 probe_kernel_read(&data, &kthread->data, sizeof(data));
158 static void __kthread_parkme(struct kthread *self)
160 __set_current_state(TASK_PARKED);
161 while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) {
162 if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags))
163 complete(&self->parked);
165 __set_current_state(TASK_PARKED);
167 clear_bit(KTHREAD_IS_PARKED, &self->flags);
168 __set_current_state(TASK_RUNNING);
171 void kthread_parkme(void)
173 __kthread_parkme(to_kthread(current));
175 EXPORT_SYMBOL_GPL(kthread_parkme);
177 static int kthread(void *_create)
179 /* Copy data: it's on kthread's stack */
180 struct kthread_create_info *create = _create;
181 int (*threadfn)(void *data) = create->threadfn;
182 void *data = create->data;
183 struct completion *done;
189 init_completion(&self.exited);
190 init_completion(&self.parked);
191 current->vfork_done = &self.exited;
193 /* If user was SIGKILLed, I release the structure. */
194 done = xchg(&create->done, NULL);
199 /* OK, tell user we're spawned, wait for stop or wakeup */
200 __set_current_state(TASK_UNINTERRUPTIBLE);
201 create->result = current;
207 if (!test_bit(KTHREAD_SHOULD_STOP, &self.flags)) {
208 __kthread_parkme(&self);
209 ret = threadfn(data);
211 /* we can't just return, we must preserve "self" on stack */
215 /* called from do_fork() to get node information for about to be created task */
216 int tsk_fork_get_node(struct task_struct *tsk)
219 if (tsk == kthreadd_task)
220 return tsk->pref_node_fork;
225 static void create_kthread(struct kthread_create_info *create)
230 current->pref_node_fork = create->node;
232 /* We want our own signal handler (we take no signals by default). */
233 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
235 /* If user was SIGKILLed, I release the structure. */
236 struct completion *done = xchg(&create->done, NULL);
242 create->result = ERR_PTR(pid);
247 static struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
248 void *data, int node,
249 const char namefmt[],
252 DECLARE_COMPLETION_ONSTACK(done);
253 struct task_struct *task;
254 struct kthread_create_info *create = kmalloc(sizeof(*create),
258 return ERR_PTR(-ENOMEM);
259 create->threadfn = threadfn;
262 create->done = &done;
264 spin_lock(&kthread_create_lock);
265 list_add_tail(&create->list, &kthread_create_list);
266 spin_unlock(&kthread_create_lock);
268 wake_up_process(kthreadd_task);
270 * Wait for completion in killable state, for I might be chosen by
271 * the OOM killer while kthreadd is trying to allocate memory for
274 if (unlikely(wait_for_completion_killable(&done))) {
276 * If I was SIGKILLed before kthreadd (or new kernel thread)
277 * calls complete(), leave the cleanup of this structure to
280 if (xchg(&create->done, NULL))
281 return ERR_PTR(-EINTR);
283 * kthreadd (or new kernel thread) will call complete()
286 wait_for_completion(&done);
288 task = create->result;
290 static const struct sched_param param = { .sched_priority = 0 };
292 vsnprintf(task->comm, sizeof(task->comm), namefmt, args);
294 * root may have changed our (kthreadd's) priority or CPU mask.
295 * The kernel thread should not inherit these properties.
297 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
298 set_cpus_allowed_ptr(task, cpu_all_mask);
305 * kthread_create_on_node - create a kthread.
306 * @threadfn: the function to run until signal_pending(current).
307 * @data: data ptr for @threadfn.
308 * @node: task and thread structures for the thread are allocated on this node
309 * @namefmt: printf-style name for the thread.
311 * Description: This helper function creates and names a kernel
312 * thread. The thread will be stopped: use wake_up_process() to start
313 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
314 * is affine to all CPUs.
316 * If thread is going to be bound on a particular cpu, give its node
317 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
318 * When woken, the thread will run @threadfn() with @data as its
319 * argument. @threadfn() can either call do_exit() directly if it is a
320 * standalone thread for which no one will call kthread_stop(), or
321 * return when 'kthread_should_stop()' is true (which means
322 * kthread_stop() has been called). The return value should be zero
323 * or a negative error number; it will be passed to kthread_stop().
325 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
327 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
328 void *data, int node,
329 const char namefmt[],
332 struct task_struct *task;
335 va_start(args, namefmt);
336 task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
341 EXPORT_SYMBOL(kthread_create_on_node);
343 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
347 if (!wait_task_inactive(p, state)) {
352 /* It's safe because the task is inactive. */
353 raw_spin_lock_irqsave(&p->pi_lock, flags);
354 do_set_cpus_allowed(p, mask);
355 p->flags |= PF_NO_SETAFFINITY;
356 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
359 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
361 __kthread_bind_mask(p, cpumask_of(cpu), state);
364 void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
366 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
370 * kthread_bind - bind a just-created kthread to a cpu.
371 * @p: thread created by kthread_create().
372 * @cpu: cpu (might not be online, must be possible) for @k to run on.
374 * Description: This function is equivalent to set_cpus_allowed(),
375 * except that @cpu doesn't need to be online, and the thread must be
376 * stopped (i.e., just returned from kthread_create()).
378 void kthread_bind(struct task_struct *p, unsigned int cpu)
380 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
382 EXPORT_SYMBOL(kthread_bind);
385 * kthread_create_on_cpu - Create a cpu bound kthread
386 * @threadfn: the function to run until signal_pending(current).
387 * @data: data ptr for @threadfn.
388 * @cpu: The cpu on which the thread should be bound,
389 * @namefmt: printf-style name for the thread. Format is restricted
390 * to "name.*%u". Code fills in cpu number.
392 * Description: This helper function creates and names a kernel thread
393 * The thread will be woken and put into park mode.
395 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
396 void *data, unsigned int cpu,
399 struct task_struct *p;
401 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
405 kthread_bind(p, cpu);
406 /* CPU hotplug need to bind once again when unparking the thread. */
407 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
408 to_kthread(p)->cpu = cpu;
412 static void __kthread_unpark(struct task_struct *k, struct kthread *kthread)
414 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
416 * We clear the IS_PARKED bit here as we don't wait
417 * until the task has left the park code. So if we'd
418 * park before that happens we'd see the IS_PARKED bit
419 * which might be about to be cleared.
421 if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
423 * Newly created kthread was parked when the CPU was offline.
424 * The binding was lost and we need to set it again.
426 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
427 __kthread_bind(k, kthread->cpu, TASK_PARKED);
428 wake_up_state(k, TASK_PARKED);
433 * kthread_unpark - unpark a thread created by kthread_create().
434 * @k: thread created by kthread_create().
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.
440 void kthread_unpark(struct task_struct *k)
442 struct kthread *kthread = to_live_kthread(k);
445 __kthread_unpark(k, kthread);
449 EXPORT_SYMBOL_GPL(kthread_unpark);
452 * kthread_park - park a thread created by kthread_create().
453 * @k: thread created by kthread_create().
455 * Sets kthread_should_park() for @k to return true, wakes it, and
456 * waits for it to return. This can also be called after kthread_create()
457 * instead of calling wake_up_process(): the thread will park without
458 * calling threadfn().
460 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
461 * If called by the kthread itself just the park bit is set.
463 int kthread_park(struct task_struct *k)
465 struct kthread *kthread = to_live_kthread(k);
469 if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
470 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
473 wait_for_completion(&kthread->parked);
481 EXPORT_SYMBOL_GPL(kthread_park);
484 * kthread_stop - stop a thread created by kthread_create().
485 * @k: thread created by kthread_create().
487 * Sets kthread_should_stop() for @k to return true, wakes it, and
488 * waits for it to exit. This can also be called after kthread_create()
489 * instead of calling wake_up_process(): the thread will exit without
490 * calling threadfn().
492 * If threadfn() may call do_exit() itself, the caller must ensure
493 * task_struct can't go away.
495 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
498 int kthread_stop(struct task_struct *k)
500 struct kthread *kthread;
503 trace_sched_kthread_stop(k);
506 kthread = to_live_kthread(k);
508 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
509 __kthread_unpark(k, kthread);
511 wait_for_completion(&kthread->exited);
517 trace_sched_kthread_stop_ret(ret);
520 EXPORT_SYMBOL(kthread_stop);
522 int kthreadd(void *unused)
524 struct task_struct *tsk = current;
526 /* Setup a clean context for our children to inherit. */
527 set_task_comm(tsk, "kthreadd");
529 set_cpus_allowed_ptr(tsk, cpu_all_mask);
530 set_mems_allowed(node_states[N_MEMORY]);
532 current->flags |= PF_NOFREEZE;
535 set_current_state(TASK_INTERRUPTIBLE);
536 if (list_empty(&kthread_create_list))
538 __set_current_state(TASK_RUNNING);
540 spin_lock(&kthread_create_lock);
541 while (!list_empty(&kthread_create_list)) {
542 struct kthread_create_info *create;
544 create = list_entry(kthread_create_list.next,
545 struct kthread_create_info, list);
546 list_del_init(&create->list);
547 spin_unlock(&kthread_create_lock);
549 create_kthread(create);
551 spin_lock(&kthread_create_lock);
553 spin_unlock(&kthread_create_lock);
559 void __kthread_init_worker(struct kthread_worker *worker,
561 struct lock_class_key *key)
563 spin_lock_init(&worker->lock);
564 lockdep_set_class_and_name(&worker->lock, key, name);
565 INIT_LIST_HEAD(&worker->work_list);
566 INIT_LIST_HEAD(&worker->delayed_work_list);
569 EXPORT_SYMBOL_GPL(__kthread_init_worker);
572 * kthread_worker_fn - kthread function to process kthread_worker
573 * @worker_ptr: pointer to initialized kthread_worker
575 * This function implements the main cycle of kthread worker. It processes
576 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
579 * The works are not allowed to keep any locks, disable preemption or interrupts
580 * when they finish. There is defined a safe point for freezing when one work
581 * finishes and before a new one is started.
583 * Also the works must not be handled by more than one worker at the same time,
584 * see also kthread_queue_work().
586 int kthread_worker_fn(void *worker_ptr)
588 struct kthread_worker *worker = worker_ptr;
589 struct kthread_work *work;
592 * FIXME: Update the check and remove the assignment when all kthread
593 * worker users are created using kthread_create_worker*() functions.
595 WARN_ON(worker->task && worker->task != current);
596 worker->task = current;
598 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
600 if (kthread_should_stop()) {
601 __set_current_state(TASK_RUNNING);
602 spin_lock_irq(&worker->lock);
604 spin_unlock_irq(&worker->lock);
609 spin_lock_irq(&worker->lock);
610 if (!list_empty(&worker->work_list)) {
611 work = list_first_entry(&worker->work_list,
612 struct kthread_work, node);
613 list_del_init(&work->node);
615 worker->current_work = work;
616 spin_unlock_irq(&worker->lock);
619 __set_current_state(TASK_RUNNING);
621 } else if (!freezing(current))
627 EXPORT_SYMBOL_GPL(kthread_worker_fn);
629 static struct kthread_worker *
630 __kthread_create_worker(int cpu, const char namefmt[], va_list args)
632 struct kthread_worker *worker;
633 struct task_struct *task;
635 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
637 return ERR_PTR(-ENOMEM);
639 kthread_init_worker(worker);
642 char name[TASK_COMM_LEN];
645 * kthread_create_worker_on_cpu() allows to pass a generic
646 * namefmt in compare with kthread_create_on_cpu. We need
649 vsnprintf(name, sizeof(name), namefmt, args);
650 task = kthread_create_on_cpu(kthread_worker_fn, worker,
653 task = __kthread_create_on_node(kthread_worker_fn, worker,
661 wake_up_process(task);
666 return ERR_CAST(task);
670 * kthread_create_worker - create a kthread worker
671 * @namefmt: printf-style name for the kthread worker (task).
673 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
674 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
675 * when the worker was SIGKILLed.
677 struct kthread_worker *
678 kthread_create_worker(const char namefmt[], ...)
680 struct kthread_worker *worker;
683 va_start(args, namefmt);
684 worker = __kthread_create_worker(-1, namefmt, args);
689 EXPORT_SYMBOL(kthread_create_worker);
692 * kthread_create_worker_on_cpu - create a kthread worker and bind it
693 * it to a given CPU and the associated NUMA node.
695 * @namefmt: printf-style name for the kthread worker (task).
697 * Use a valid CPU number if you want to bind the kthread worker
698 * to the given CPU and the associated NUMA node.
700 * A good practice is to add the cpu number also into the worker name.
701 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
703 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
704 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
705 * when the worker was SIGKILLed.
707 struct kthread_worker *
708 kthread_create_worker_on_cpu(int cpu, const char namefmt[], ...)
710 struct kthread_worker *worker;
713 va_start(args, namefmt);
714 worker = __kthread_create_worker(cpu, namefmt, args);
719 EXPORT_SYMBOL(kthread_create_worker_on_cpu);
722 * Returns true when the work could not be queued at the moment.
723 * It happens when it is already pending in a worker list
724 * or when it is being cancelled.
726 static inline bool queuing_blocked(struct kthread_worker *worker,
727 struct kthread_work *work)
729 lockdep_assert_held(&worker->lock);
731 return !list_empty(&work->node) || work->canceling;
734 static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
735 struct kthread_work *work)
737 lockdep_assert_held(&worker->lock);
738 WARN_ON_ONCE(!list_empty(&work->node));
739 /* Do not use a work with >1 worker, see kthread_queue_work() */
740 WARN_ON_ONCE(work->worker && work->worker != worker);
743 /* insert @work before @pos in @worker */
744 static void kthread_insert_work(struct kthread_worker *worker,
745 struct kthread_work *work,
746 struct list_head *pos)
748 kthread_insert_work_sanity_check(worker, work);
750 list_add_tail(&work->node, pos);
751 work->worker = worker;
752 if (!worker->current_work && likely(worker->task))
753 wake_up_process(worker->task);
757 * kthread_queue_work - queue a kthread_work
758 * @worker: target kthread_worker
759 * @work: kthread_work to queue
761 * Queue @work to work processor @task for async execution. @task
762 * must have been created with kthread_worker_create(). Returns %true
763 * if @work was successfully queued, %false if it was already pending.
765 * Reinitialize the work if it needs to be used by another worker.
766 * For example, when the worker was stopped and started again.
768 bool kthread_queue_work(struct kthread_worker *worker,
769 struct kthread_work *work)
774 spin_lock_irqsave(&worker->lock, flags);
775 if (!queuing_blocked(worker, work)) {
776 kthread_insert_work(worker, work, &worker->work_list);
779 spin_unlock_irqrestore(&worker->lock, flags);
782 EXPORT_SYMBOL_GPL(kthread_queue_work);
785 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
786 * delayed work when the timer expires.
787 * @__data: pointer to the data associated with the timer
789 * The format of the function is defined by struct timer_list.
790 * It should have been called from irqsafe timer with irq already off.
792 void kthread_delayed_work_timer_fn(unsigned long __data)
794 struct kthread_delayed_work *dwork =
795 (struct kthread_delayed_work *)__data;
796 struct kthread_work *work = &dwork->work;
797 struct kthread_worker *worker = work->worker;
800 * This might happen when a pending work is reinitialized.
801 * It means that it is used a wrong way.
803 if (WARN_ON_ONCE(!worker))
806 spin_lock(&worker->lock);
807 /* Work must not be used with >1 worker, see kthread_queue_work(). */
808 WARN_ON_ONCE(work->worker != worker);
810 /* Move the work from worker->delayed_work_list. */
811 WARN_ON_ONCE(list_empty(&work->node));
812 list_del_init(&work->node);
813 kthread_insert_work(worker, work, &worker->work_list);
815 spin_unlock(&worker->lock);
817 EXPORT_SYMBOL(kthread_delayed_work_timer_fn);
819 void __kthread_queue_delayed_work(struct kthread_worker *worker,
820 struct kthread_delayed_work *dwork,
823 struct timer_list *timer = &dwork->timer;
824 struct kthread_work *work = &dwork->work;
826 WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn ||
827 timer->data != (unsigned long)dwork);
830 * If @delay is 0, queue @dwork->work immediately. This is for
831 * both optimization and correctness. The earliest @timer can
832 * expire is on the closest next tick and delayed_work users depend
833 * on that there's no such delay when @delay is 0.
836 kthread_insert_work(worker, work, &worker->work_list);
840 /* Be paranoid and try to detect possible races already now. */
841 kthread_insert_work_sanity_check(worker, work);
843 list_add(&work->node, &worker->delayed_work_list);
844 work->worker = worker;
845 timer_stats_timer_set_start_info(&dwork->timer);
846 timer->expires = jiffies + delay;
851 * kthread_queue_delayed_work - queue the associated kthread work
853 * @worker: target kthread_worker
854 * @dwork: kthread_delayed_work to queue
855 * @delay: number of jiffies to wait before queuing
857 * If the work has not been pending it starts a timer that will queue
858 * the work after the given @delay. If @delay is zero, it queues the
861 * Return: %false if the @work has already been pending. It means that
862 * either the timer was running or the work was queued. It returns %true
865 bool kthread_queue_delayed_work(struct kthread_worker *worker,
866 struct kthread_delayed_work *dwork,
869 struct kthread_work *work = &dwork->work;
873 spin_lock_irqsave(&worker->lock, flags);
875 if (!queuing_blocked(worker, work)) {
876 __kthread_queue_delayed_work(worker, dwork, delay);
880 spin_unlock_irqrestore(&worker->lock, flags);
883 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
885 struct kthread_flush_work {
886 struct kthread_work work;
887 struct completion done;
890 static void kthread_flush_work_fn(struct kthread_work *work)
892 struct kthread_flush_work *fwork =
893 container_of(work, struct kthread_flush_work, work);
894 complete(&fwork->done);
898 * kthread_flush_work - flush a kthread_work
899 * @work: work to flush
901 * If @work is queued or executing, wait for it to finish execution.
903 void kthread_flush_work(struct kthread_work *work)
905 struct kthread_flush_work fwork = {
906 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
907 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
909 struct kthread_worker *worker;
912 worker = work->worker;
916 spin_lock_irq(&worker->lock);
917 /* Work must not be used with >1 worker, see kthread_queue_work(). */
918 WARN_ON_ONCE(work->worker != worker);
920 if (!list_empty(&work->node))
921 kthread_insert_work(worker, &fwork.work, work->node.next);
922 else if (worker->current_work == work)
923 kthread_insert_work(worker, &fwork.work,
924 worker->work_list.next);
928 spin_unlock_irq(&worker->lock);
931 wait_for_completion(&fwork.done);
933 EXPORT_SYMBOL_GPL(kthread_flush_work);
936 * This function removes the work from the worker queue. Also it makes sure
937 * that it won't get queued later via the delayed work's timer.
939 * The work might still be in use when this function finishes. See the
940 * current_work proceed by the worker.
942 * Return: %true if @work was pending and successfully canceled,
943 * %false if @work was not pending
945 static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
946 unsigned long *flags)
948 /* Try to cancel the timer if exists. */
950 struct kthread_delayed_work *dwork =
951 container_of(work, struct kthread_delayed_work, work);
952 struct kthread_worker *worker = work->worker;
955 * del_timer_sync() must be called to make sure that the timer
956 * callback is not running. The lock must be temporary released
957 * to avoid a deadlock with the callback. In the meantime,
958 * any queuing is blocked by setting the canceling counter.
961 spin_unlock_irqrestore(&worker->lock, *flags);
962 del_timer_sync(&dwork->timer);
963 spin_lock_irqsave(&worker->lock, *flags);
968 * Try to remove the work from a worker list. It might either
969 * be from worker->work_list or from worker->delayed_work_list.
971 if (!list_empty(&work->node)) {
972 list_del_init(&work->node);
980 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
981 * @worker: kthread worker to use
982 * @dwork: kthread delayed work to queue
983 * @delay: number of jiffies to wait before queuing
985 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
986 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
987 * @work is guaranteed to be queued immediately.
989 * Return: %true if @dwork was pending and its timer was modified,
992 * A special case is when the work is being canceled in parallel.
993 * It might be caused either by the real kthread_cancel_delayed_work_sync()
994 * or yet another kthread_mod_delayed_work() call. We let the other command
995 * win and return %false here. The caller is supposed to synchronize these
996 * operations a reasonable way.
998 * This function is safe to call from any context including IRQ handler.
999 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1002 bool kthread_mod_delayed_work(struct kthread_worker *worker,
1003 struct kthread_delayed_work *dwork,
1004 unsigned long delay)
1006 struct kthread_work *work = &dwork->work;
1007 unsigned long flags;
1010 spin_lock_irqsave(&worker->lock, flags);
1012 /* Do not bother with canceling when never queued. */
1016 /* Work must not be used with >1 worker, see kthread_queue_work() */
1017 WARN_ON_ONCE(work->worker != worker);
1019 /* Do not fight with another command that is canceling this work. */
1020 if (work->canceling)
1023 ret = __kthread_cancel_work(work, true, &flags);
1025 __kthread_queue_delayed_work(worker, dwork, delay);
1027 spin_unlock_irqrestore(&worker->lock, flags);
1030 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1032 static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1034 struct kthread_worker *worker = work->worker;
1035 unsigned long flags;
1041 spin_lock_irqsave(&worker->lock, flags);
1042 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1043 WARN_ON_ONCE(work->worker != worker);
1045 ret = __kthread_cancel_work(work, is_dwork, &flags);
1047 if (worker->current_work != work)
1051 * The work is in progress and we need to wait with the lock released.
1052 * In the meantime, block any queuing by setting the canceling counter.
1055 spin_unlock_irqrestore(&worker->lock, flags);
1056 kthread_flush_work(work);
1057 spin_lock_irqsave(&worker->lock, flags);
1061 spin_unlock_irqrestore(&worker->lock, flags);
1067 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1068 * @work: the kthread work to cancel
1070 * Cancel @work and wait for its execution to finish. This function
1071 * can be used even if the work re-queues itself. On return from this
1072 * function, @work is guaranteed to be not pending or executing on any CPU.
1074 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1075 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1077 * The caller must ensure that the worker on which @work was last
1078 * queued can't be destroyed before this function returns.
1080 * Return: %true if @work was pending, %false otherwise.
1082 bool kthread_cancel_work_sync(struct kthread_work *work)
1084 return __kthread_cancel_work_sync(work, false);
1086 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1089 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1090 * wait for it to finish.
1091 * @dwork: the kthread delayed work to cancel
1093 * This is kthread_cancel_work_sync() for delayed works.
1095 * Return: %true if @dwork was pending, %false otherwise.
1097 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1099 return __kthread_cancel_work_sync(&dwork->work, true);
1101 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1104 * kthread_flush_worker - flush all current works on a kthread_worker
1105 * @worker: worker to flush
1107 * Wait until all currently executing or pending works on @worker are
1110 void kthread_flush_worker(struct kthread_worker *worker)
1112 struct kthread_flush_work fwork = {
1113 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1114 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1117 kthread_queue_work(worker, &fwork.work);
1118 wait_for_completion(&fwork.done);
1120 EXPORT_SYMBOL_GPL(kthread_flush_worker);
1123 * kthread_destroy_worker - destroy a kthread worker
1124 * @worker: worker to be destroyed
1126 * Flush and destroy @worker. The simple flush is enough because the kthread
1127 * worker API is used only in trivial scenarios. There are no multi-step state
1130 void kthread_destroy_worker(struct kthread_worker *worker)
1132 struct task_struct *task;
1134 task = worker->task;
1138 kthread_flush_worker(worker);
1140 WARN_ON(!list_empty(&worker->work_list));
1143 EXPORT_SYMBOL(kthread_destroy_worker);