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 static inline void set_kthread_struct(void *kthread)
59 * We abuse ->set_child_tid to avoid the new member and because it
60 * can't be wrongly copied by copy_process(). We also rely on fact
61 * that the caller can't exec, so PF_KTHREAD can't be cleared.
63 current->set_child_tid = (__force void __user *)kthread;
66 static inline struct kthread *to_kthread(struct task_struct *k)
68 WARN_ON(!(k->flags & PF_KTHREAD));
69 return (__force void *)k->set_child_tid;
72 void free_kthread_struct(struct task_struct *k)
75 * Can be NULL if this kthread was created by kernel_thread()
76 * or if kmalloc() in kthread() failed.
81 #define __to_kthread(vfork) \
82 container_of(vfork, struct kthread, exited)
85 * TODO: kill it and use to_kthread(). But we still need the users
86 * like kthread_stop() which has to sync with the exiting kthread.
88 static struct kthread *to_live_kthread(struct task_struct *k)
90 struct completion *vfork = ACCESS_ONCE(k->vfork_done);
91 if (likely(vfork) && try_get_task_stack(k))
92 return __to_kthread(vfork);
97 * kthread_should_stop - should this kthread return now?
99 * When someone calls kthread_stop() on your kthread, it will be woken
100 * and this will return true. You should then return, and your return
101 * value will be passed through to kthread_stop().
103 bool kthread_should_stop(void)
105 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
107 EXPORT_SYMBOL(kthread_should_stop);
110 * kthread_should_park - should this kthread park now?
112 * When someone calls kthread_park() on your kthread, it will be woken
113 * and this will return true. You should then do the necessary
114 * cleanup and call kthread_parkme()
116 * Similar to kthread_should_stop(), but this keeps the thread alive
117 * and in a park position. kthread_unpark() "restarts" the thread and
118 * calls the thread function again.
120 bool kthread_should_park(void)
122 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
124 EXPORT_SYMBOL_GPL(kthread_should_park);
127 * kthread_freezable_should_stop - should this freezable kthread return now?
128 * @was_frozen: optional out parameter, indicates whether %current was frozen
130 * kthread_should_stop() for freezable kthreads, which will enter
131 * refrigerator if necessary. This function is safe from kthread_stop() /
132 * freezer deadlock and freezable kthreads should use this function instead
133 * of calling try_to_freeze() directly.
135 bool kthread_freezable_should_stop(bool *was_frozen)
141 if (unlikely(freezing(current)))
142 frozen = __refrigerator(true);
145 *was_frozen = frozen;
147 return kthread_should_stop();
149 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
152 * kthread_data - return data value specified on kthread creation
153 * @task: kthread task in question
155 * Return the data value specified when kthread @task was created.
156 * The caller is responsible for ensuring the validity of @task when
157 * calling this function.
159 void *kthread_data(struct task_struct *task)
161 return to_kthread(task)->data;
165 * kthread_probe_data - speculative version of kthread_data()
166 * @task: possible kthread task in question
168 * @task could be a kthread task. Return the data value specified when it
169 * was created if accessible. If @task isn't a kthread task or its data is
170 * inaccessible for any reason, %NULL is returned. This function requires
171 * that @task itself is safe to dereference.
173 void *kthread_probe_data(struct task_struct *task)
175 struct kthread *kthread = to_kthread(task);
178 probe_kernel_read(&data, &kthread->data, sizeof(data));
182 static void __kthread_parkme(struct kthread *self)
184 __set_current_state(TASK_PARKED);
185 while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) {
186 if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags))
187 complete(&self->parked);
189 __set_current_state(TASK_PARKED);
191 clear_bit(KTHREAD_IS_PARKED, &self->flags);
192 __set_current_state(TASK_RUNNING);
195 void kthread_parkme(void)
197 __kthread_parkme(to_kthread(current));
199 EXPORT_SYMBOL_GPL(kthread_parkme);
201 static int kthread(void *_create)
203 /* Copy data: it's on kthread's stack */
204 struct kthread_create_info *create = _create;
205 int (*threadfn)(void *data) = create->threadfn;
206 void *data = create->data;
207 struct completion *done;
208 struct kthread *self;
211 self = kmalloc(sizeof(*self), GFP_KERNEL);
212 set_kthread_struct(self);
214 /* If user was SIGKILLed, I release the structure. */
215 done = xchg(&create->done, NULL);
222 create->result = ERR_PTR(-ENOMEM);
229 init_completion(&self->exited);
230 init_completion(&self->parked);
231 current->vfork_done = &self->exited;
233 /* OK, tell user we're spawned, wait for stop or wakeup */
234 __set_current_state(TASK_UNINTERRUPTIBLE);
235 create->result = current;
240 if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
241 __kthread_parkme(self);
242 ret = threadfn(data);
247 /* called from do_fork() to get node information for about to be created task */
248 int tsk_fork_get_node(struct task_struct *tsk)
251 if (tsk == kthreadd_task)
252 return tsk->pref_node_fork;
257 static void create_kthread(struct kthread_create_info *create)
262 current->pref_node_fork = create->node;
264 /* We want our own signal handler (we take no signals by default). */
265 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
267 /* If user was SIGKILLed, I release the structure. */
268 struct completion *done = xchg(&create->done, NULL);
274 create->result = ERR_PTR(pid);
279 static struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
280 void *data, int node,
281 const char namefmt[],
284 DECLARE_COMPLETION_ONSTACK(done);
285 struct task_struct *task;
286 struct kthread_create_info *create = kmalloc(sizeof(*create),
290 return ERR_PTR(-ENOMEM);
291 create->threadfn = threadfn;
294 create->done = &done;
296 spin_lock(&kthread_create_lock);
297 list_add_tail(&create->list, &kthread_create_list);
298 spin_unlock(&kthread_create_lock);
300 wake_up_process(kthreadd_task);
302 * Wait for completion in killable state, for I might be chosen by
303 * the OOM killer while kthreadd is trying to allocate memory for
306 if (unlikely(wait_for_completion_killable(&done))) {
308 * If I was SIGKILLed before kthreadd (or new kernel thread)
309 * calls complete(), leave the cleanup of this structure to
312 if (xchg(&create->done, NULL))
313 return ERR_PTR(-EINTR);
315 * kthreadd (or new kernel thread) will call complete()
318 wait_for_completion(&done);
320 task = create->result;
322 static const struct sched_param param = { .sched_priority = 0 };
324 vsnprintf(task->comm, sizeof(task->comm), namefmt, args);
326 * root may have changed our (kthreadd's) priority or CPU mask.
327 * The kernel thread should not inherit these properties.
329 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
330 set_cpus_allowed_ptr(task, cpu_all_mask);
337 * kthread_create_on_node - create a kthread.
338 * @threadfn: the function to run until signal_pending(current).
339 * @data: data ptr for @threadfn.
340 * @node: task and thread structures for the thread are allocated on this node
341 * @namefmt: printf-style name for the thread.
343 * Description: This helper function creates and names a kernel
344 * thread. The thread will be stopped: use wake_up_process() to start
345 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
346 * is affine to all CPUs.
348 * If thread is going to be bound on a particular cpu, give its node
349 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
350 * When woken, the thread will run @threadfn() with @data as its
351 * argument. @threadfn() can either call do_exit() directly if it is a
352 * standalone thread for which no one will call kthread_stop(), or
353 * return when 'kthread_should_stop()' is true (which means
354 * kthread_stop() has been called). The return value should be zero
355 * or a negative error number; it will be passed to kthread_stop().
357 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
359 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
360 void *data, int node,
361 const char namefmt[],
364 struct task_struct *task;
367 va_start(args, namefmt);
368 task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
373 EXPORT_SYMBOL(kthread_create_on_node);
375 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
379 if (!wait_task_inactive(p, state)) {
384 /* It's safe because the task is inactive. */
385 raw_spin_lock_irqsave(&p->pi_lock, flags);
386 do_set_cpus_allowed(p, mask);
387 p->flags |= PF_NO_SETAFFINITY;
388 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
391 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
393 __kthread_bind_mask(p, cpumask_of(cpu), state);
396 void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
398 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
402 * kthread_bind - bind a just-created kthread to a cpu.
403 * @p: thread created by kthread_create().
404 * @cpu: cpu (might not be online, must be possible) for @k to run on.
406 * Description: This function is equivalent to set_cpus_allowed(),
407 * except that @cpu doesn't need to be online, and the thread must be
408 * stopped (i.e., just returned from kthread_create()).
410 void kthread_bind(struct task_struct *p, unsigned int cpu)
412 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
414 EXPORT_SYMBOL(kthread_bind);
417 * kthread_create_on_cpu - Create a cpu bound kthread
418 * @threadfn: the function to run until signal_pending(current).
419 * @data: data ptr for @threadfn.
420 * @cpu: The cpu on which the thread should be bound,
421 * @namefmt: printf-style name for the thread. Format is restricted
422 * to "name.*%u". Code fills in cpu number.
424 * Description: This helper function creates and names a kernel thread
425 * The thread will be woken and put into park mode.
427 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
428 void *data, unsigned int cpu,
431 struct task_struct *p;
433 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
437 kthread_bind(p, cpu);
438 /* CPU hotplug need to bind once again when unparking the thread. */
439 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
440 to_kthread(p)->cpu = cpu;
444 static void __kthread_unpark(struct task_struct *k, struct kthread *kthread)
446 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
448 * We clear the IS_PARKED bit here as we don't wait
449 * until the task has left the park code. So if we'd
450 * park before that happens we'd see the IS_PARKED bit
451 * which might be about to be cleared.
453 if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
455 * Newly created kthread was parked when the CPU was offline.
456 * The binding was lost and we need to set it again.
458 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
459 __kthread_bind(k, kthread->cpu, TASK_PARKED);
460 wake_up_state(k, TASK_PARKED);
465 * kthread_unpark - unpark a thread created by kthread_create().
466 * @k: thread created by kthread_create().
468 * Sets kthread_should_park() for @k to return false, wakes it, and
469 * waits for it to return. If the thread is marked percpu then its
470 * bound to the cpu again.
472 void kthread_unpark(struct task_struct *k)
474 struct kthread *kthread = to_live_kthread(k);
477 __kthread_unpark(k, kthread);
481 EXPORT_SYMBOL_GPL(kthread_unpark);
484 * kthread_park - park a thread created by kthread_create().
485 * @k: thread created by kthread_create().
487 * Sets kthread_should_park() for @k to return true, wakes it, and
488 * waits for it to return. This can also be called after kthread_create()
489 * instead of calling wake_up_process(): the thread will park without
490 * calling threadfn().
492 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
493 * If called by the kthread itself just the park bit is set.
495 int kthread_park(struct task_struct *k)
497 struct kthread *kthread = to_live_kthread(k);
501 if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
502 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
505 wait_for_completion(&kthread->parked);
513 EXPORT_SYMBOL_GPL(kthread_park);
516 * kthread_stop - stop a thread created by kthread_create().
517 * @k: thread created by kthread_create().
519 * Sets kthread_should_stop() for @k to return true, wakes it, and
520 * waits for it to exit. This can also be called after kthread_create()
521 * instead of calling wake_up_process(): the thread will exit without
522 * calling threadfn().
524 * If threadfn() may call do_exit() itself, the caller must ensure
525 * task_struct can't go away.
527 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
530 int kthread_stop(struct task_struct *k)
532 struct kthread *kthread;
535 trace_sched_kthread_stop(k);
538 kthread = to_live_kthread(k);
540 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
541 __kthread_unpark(k, kthread);
543 wait_for_completion(&kthread->exited);
549 trace_sched_kthread_stop_ret(ret);
552 EXPORT_SYMBOL(kthread_stop);
554 int kthreadd(void *unused)
556 struct task_struct *tsk = current;
558 /* Setup a clean context for our children to inherit. */
559 set_task_comm(tsk, "kthreadd");
561 set_cpus_allowed_ptr(tsk, cpu_all_mask);
562 set_mems_allowed(node_states[N_MEMORY]);
564 current->flags |= PF_NOFREEZE;
567 set_current_state(TASK_INTERRUPTIBLE);
568 if (list_empty(&kthread_create_list))
570 __set_current_state(TASK_RUNNING);
572 spin_lock(&kthread_create_lock);
573 while (!list_empty(&kthread_create_list)) {
574 struct kthread_create_info *create;
576 create = list_entry(kthread_create_list.next,
577 struct kthread_create_info, list);
578 list_del_init(&create->list);
579 spin_unlock(&kthread_create_lock);
581 create_kthread(create);
583 spin_lock(&kthread_create_lock);
585 spin_unlock(&kthread_create_lock);
591 void __kthread_init_worker(struct kthread_worker *worker,
593 struct lock_class_key *key)
595 memset(worker, 0, sizeof(struct kthread_worker));
596 spin_lock_init(&worker->lock);
597 lockdep_set_class_and_name(&worker->lock, key, name);
598 INIT_LIST_HEAD(&worker->work_list);
599 INIT_LIST_HEAD(&worker->delayed_work_list);
601 EXPORT_SYMBOL_GPL(__kthread_init_worker);
604 * kthread_worker_fn - kthread function to process kthread_worker
605 * @worker_ptr: pointer to initialized kthread_worker
607 * This function implements the main cycle of kthread worker. It processes
608 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
611 * The works are not allowed to keep any locks, disable preemption or interrupts
612 * when they finish. There is defined a safe point for freezing when one work
613 * finishes and before a new one is started.
615 * Also the works must not be handled by more than one worker at the same time,
616 * see also kthread_queue_work().
618 int kthread_worker_fn(void *worker_ptr)
620 struct kthread_worker *worker = worker_ptr;
621 struct kthread_work *work;
624 * FIXME: Update the check and remove the assignment when all kthread
625 * worker users are created using kthread_create_worker*() functions.
627 WARN_ON(worker->task && worker->task != current);
628 worker->task = current;
630 if (worker->flags & KTW_FREEZABLE)
634 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
636 if (kthread_should_stop()) {
637 __set_current_state(TASK_RUNNING);
638 spin_lock_irq(&worker->lock);
640 spin_unlock_irq(&worker->lock);
645 spin_lock_irq(&worker->lock);
646 if (!list_empty(&worker->work_list)) {
647 work = list_first_entry(&worker->work_list,
648 struct kthread_work, node);
649 list_del_init(&work->node);
651 worker->current_work = work;
652 spin_unlock_irq(&worker->lock);
655 __set_current_state(TASK_RUNNING);
657 } else if (!freezing(current))
663 EXPORT_SYMBOL_GPL(kthread_worker_fn);
665 static struct kthread_worker *
666 __kthread_create_worker(int cpu, unsigned int flags,
667 const char namefmt[], va_list args)
669 struct kthread_worker *worker;
670 struct task_struct *task;
672 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
674 return ERR_PTR(-ENOMEM);
676 kthread_init_worker(worker);
679 char name[TASK_COMM_LEN];
682 * kthread_create_worker_on_cpu() allows to pass a generic
683 * namefmt in compare with kthread_create_on_cpu. We need
686 vsnprintf(name, sizeof(name), namefmt, args);
687 task = kthread_create_on_cpu(kthread_worker_fn, worker,
690 task = __kthread_create_on_node(kthread_worker_fn, worker,
697 worker->flags = flags;
699 wake_up_process(task);
704 return ERR_CAST(task);
708 * kthread_create_worker - create a kthread worker
709 * @flags: flags modifying the default behavior of the worker
710 * @namefmt: printf-style name for the kthread worker (task).
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.
716 struct kthread_worker *
717 kthread_create_worker(unsigned int flags, const char namefmt[], ...)
719 struct kthread_worker *worker;
722 va_start(args, namefmt);
723 worker = __kthread_create_worker(-1, flags, namefmt, args);
728 EXPORT_SYMBOL(kthread_create_worker);
731 * kthread_create_worker_on_cpu - create a kthread worker and bind it
732 * it to a given CPU and the associated NUMA node.
734 * @flags: flags modifying the default behavior of the worker
735 * @namefmt: printf-style name for the kthread worker (task).
737 * Use a valid CPU number if you want to bind the kthread worker
738 * to the given CPU and the associated NUMA node.
740 * A good practice is to add the cpu number also into the worker name.
741 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
743 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
744 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
745 * when the worker was SIGKILLed.
747 struct kthread_worker *
748 kthread_create_worker_on_cpu(int cpu, unsigned int flags,
749 const char namefmt[], ...)
751 struct kthread_worker *worker;
754 va_start(args, namefmt);
755 worker = __kthread_create_worker(cpu, flags, namefmt, args);
760 EXPORT_SYMBOL(kthread_create_worker_on_cpu);
763 * Returns true when the work could not be queued at the moment.
764 * It happens when it is already pending in a worker list
765 * or when it is being cancelled.
767 static inline bool queuing_blocked(struct kthread_worker *worker,
768 struct kthread_work *work)
770 lockdep_assert_held(&worker->lock);
772 return !list_empty(&work->node) || work->canceling;
775 static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
776 struct kthread_work *work)
778 lockdep_assert_held(&worker->lock);
779 WARN_ON_ONCE(!list_empty(&work->node));
780 /* Do not use a work with >1 worker, see kthread_queue_work() */
781 WARN_ON_ONCE(work->worker && work->worker != worker);
784 /* insert @work before @pos in @worker */
785 static void kthread_insert_work(struct kthread_worker *worker,
786 struct kthread_work *work,
787 struct list_head *pos)
789 kthread_insert_work_sanity_check(worker, work);
791 list_add_tail(&work->node, pos);
792 work->worker = worker;
793 if (!worker->current_work && likely(worker->task))
794 wake_up_process(worker->task);
798 * kthread_queue_work - queue a kthread_work
799 * @worker: target kthread_worker
800 * @work: kthread_work to queue
802 * Queue @work to work processor @task for async execution. @task
803 * must have been created with kthread_worker_create(). Returns %true
804 * if @work was successfully queued, %false if it was already pending.
806 * Reinitialize the work if it needs to be used by another worker.
807 * For example, when the worker was stopped and started again.
809 bool kthread_queue_work(struct kthread_worker *worker,
810 struct kthread_work *work)
815 spin_lock_irqsave(&worker->lock, flags);
816 if (!queuing_blocked(worker, work)) {
817 kthread_insert_work(worker, work, &worker->work_list);
820 spin_unlock_irqrestore(&worker->lock, flags);
823 EXPORT_SYMBOL_GPL(kthread_queue_work);
826 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
827 * delayed work when the timer expires.
828 * @__data: pointer to the data associated with the timer
830 * The format of the function is defined by struct timer_list.
831 * It should have been called from irqsafe timer with irq already off.
833 void kthread_delayed_work_timer_fn(unsigned long __data)
835 struct kthread_delayed_work *dwork =
836 (struct kthread_delayed_work *)__data;
837 struct kthread_work *work = &dwork->work;
838 struct kthread_worker *worker = work->worker;
841 * This might happen when a pending work is reinitialized.
842 * It means that it is used a wrong way.
844 if (WARN_ON_ONCE(!worker))
847 spin_lock(&worker->lock);
848 /* Work must not be used with >1 worker, see kthread_queue_work(). */
849 WARN_ON_ONCE(work->worker != worker);
851 /* Move the work from worker->delayed_work_list. */
852 WARN_ON_ONCE(list_empty(&work->node));
853 list_del_init(&work->node);
854 kthread_insert_work(worker, work, &worker->work_list);
856 spin_unlock(&worker->lock);
858 EXPORT_SYMBOL(kthread_delayed_work_timer_fn);
860 void __kthread_queue_delayed_work(struct kthread_worker *worker,
861 struct kthread_delayed_work *dwork,
864 struct timer_list *timer = &dwork->timer;
865 struct kthread_work *work = &dwork->work;
867 WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn ||
868 timer->data != (unsigned long)dwork);
871 * If @delay is 0, queue @dwork->work immediately. This is for
872 * both optimization and correctness. The earliest @timer can
873 * expire is on the closest next tick and delayed_work users depend
874 * on that there's no such delay when @delay is 0.
877 kthread_insert_work(worker, work, &worker->work_list);
881 /* Be paranoid and try to detect possible races already now. */
882 kthread_insert_work_sanity_check(worker, work);
884 list_add(&work->node, &worker->delayed_work_list);
885 work->worker = worker;
886 timer_stats_timer_set_start_info(&dwork->timer);
887 timer->expires = jiffies + delay;
892 * kthread_queue_delayed_work - queue the associated kthread work
894 * @worker: target kthread_worker
895 * @dwork: kthread_delayed_work to queue
896 * @delay: number of jiffies to wait before queuing
898 * If the work has not been pending it starts a timer that will queue
899 * the work after the given @delay. If @delay is zero, it queues the
902 * Return: %false if the @work has already been pending. It means that
903 * either the timer was running or the work was queued. It returns %true
906 bool kthread_queue_delayed_work(struct kthread_worker *worker,
907 struct kthread_delayed_work *dwork,
910 struct kthread_work *work = &dwork->work;
914 spin_lock_irqsave(&worker->lock, flags);
916 if (!queuing_blocked(worker, work)) {
917 __kthread_queue_delayed_work(worker, dwork, delay);
921 spin_unlock_irqrestore(&worker->lock, flags);
924 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
926 struct kthread_flush_work {
927 struct kthread_work work;
928 struct completion done;
931 static void kthread_flush_work_fn(struct kthread_work *work)
933 struct kthread_flush_work *fwork =
934 container_of(work, struct kthread_flush_work, work);
935 complete(&fwork->done);
939 * kthread_flush_work - flush a kthread_work
940 * @work: work to flush
942 * If @work is queued or executing, wait for it to finish execution.
944 void kthread_flush_work(struct kthread_work *work)
946 struct kthread_flush_work fwork = {
947 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
948 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
950 struct kthread_worker *worker;
953 worker = work->worker;
957 spin_lock_irq(&worker->lock);
958 /* Work must not be used with >1 worker, see kthread_queue_work(). */
959 WARN_ON_ONCE(work->worker != worker);
961 if (!list_empty(&work->node))
962 kthread_insert_work(worker, &fwork.work, work->node.next);
963 else if (worker->current_work == work)
964 kthread_insert_work(worker, &fwork.work,
965 worker->work_list.next);
969 spin_unlock_irq(&worker->lock);
972 wait_for_completion(&fwork.done);
974 EXPORT_SYMBOL_GPL(kthread_flush_work);
977 * This function removes the work from the worker queue. Also it makes sure
978 * that it won't get queued later via the delayed work's timer.
980 * The work might still be in use when this function finishes. See the
981 * current_work proceed by the worker.
983 * Return: %true if @work was pending and successfully canceled,
984 * %false if @work was not pending
986 static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
987 unsigned long *flags)
989 /* Try to cancel the timer if exists. */
991 struct kthread_delayed_work *dwork =
992 container_of(work, struct kthread_delayed_work, work);
993 struct kthread_worker *worker = work->worker;
996 * del_timer_sync() must be called to make sure that the timer
997 * callback is not running. The lock must be temporary released
998 * to avoid a deadlock with the callback. In the meantime,
999 * any queuing is blocked by setting the canceling counter.
1002 spin_unlock_irqrestore(&worker->lock, *flags);
1003 del_timer_sync(&dwork->timer);
1004 spin_lock_irqsave(&worker->lock, *flags);
1009 * Try to remove the work from a worker list. It might either
1010 * be from worker->work_list or from worker->delayed_work_list.
1012 if (!list_empty(&work->node)) {
1013 list_del_init(&work->node);
1021 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1022 * @worker: kthread worker to use
1023 * @dwork: kthread delayed work to queue
1024 * @delay: number of jiffies to wait before queuing
1026 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1027 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1028 * @work is guaranteed to be queued immediately.
1030 * Return: %true if @dwork was pending and its timer was modified,
1033 * A special case is when the work is being canceled in parallel.
1034 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1035 * or yet another kthread_mod_delayed_work() call. We let the other command
1036 * win and return %false here. The caller is supposed to synchronize these
1037 * operations a reasonable way.
1039 * This function is safe to call from any context including IRQ handler.
1040 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1043 bool kthread_mod_delayed_work(struct kthread_worker *worker,
1044 struct kthread_delayed_work *dwork,
1045 unsigned long delay)
1047 struct kthread_work *work = &dwork->work;
1048 unsigned long flags;
1051 spin_lock_irqsave(&worker->lock, flags);
1053 /* Do not bother with canceling when never queued. */
1057 /* Work must not be used with >1 worker, see kthread_queue_work() */
1058 WARN_ON_ONCE(work->worker != worker);
1060 /* Do not fight with another command that is canceling this work. */
1061 if (work->canceling)
1064 ret = __kthread_cancel_work(work, true, &flags);
1066 __kthread_queue_delayed_work(worker, dwork, delay);
1068 spin_unlock_irqrestore(&worker->lock, flags);
1071 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1073 static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1075 struct kthread_worker *worker = work->worker;
1076 unsigned long flags;
1082 spin_lock_irqsave(&worker->lock, flags);
1083 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1084 WARN_ON_ONCE(work->worker != worker);
1086 ret = __kthread_cancel_work(work, is_dwork, &flags);
1088 if (worker->current_work != work)
1092 * The work is in progress and we need to wait with the lock released.
1093 * In the meantime, block any queuing by setting the canceling counter.
1096 spin_unlock_irqrestore(&worker->lock, flags);
1097 kthread_flush_work(work);
1098 spin_lock_irqsave(&worker->lock, flags);
1102 spin_unlock_irqrestore(&worker->lock, flags);
1108 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1109 * @work: the kthread work to cancel
1111 * Cancel @work and wait for its execution to finish. This function
1112 * can be used even if the work re-queues itself. On return from this
1113 * function, @work is guaranteed to be not pending or executing on any CPU.
1115 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1116 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1118 * The caller must ensure that the worker on which @work was last
1119 * queued can't be destroyed before this function returns.
1121 * Return: %true if @work was pending, %false otherwise.
1123 bool kthread_cancel_work_sync(struct kthread_work *work)
1125 return __kthread_cancel_work_sync(work, false);
1127 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1130 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1131 * wait for it to finish.
1132 * @dwork: the kthread delayed work to cancel
1134 * This is kthread_cancel_work_sync() for delayed works.
1136 * Return: %true if @dwork was pending, %false otherwise.
1138 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1140 return __kthread_cancel_work_sync(&dwork->work, true);
1142 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1145 * kthread_flush_worker - flush all current works on a kthread_worker
1146 * @worker: worker to flush
1148 * Wait until all currently executing or pending works on @worker are
1151 void kthread_flush_worker(struct kthread_worker *worker)
1153 struct kthread_flush_work fwork = {
1154 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1155 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1158 kthread_queue_work(worker, &fwork.work);
1159 wait_for_completion(&fwork.done);
1161 EXPORT_SYMBOL_GPL(kthread_flush_worker);
1164 * kthread_destroy_worker - destroy a kthread worker
1165 * @worker: worker to be destroyed
1167 * Flush and destroy @worker. The simple flush is enough because the kthread
1168 * worker API is used only in trivial scenarios. There are no multi-step state
1171 void kthread_destroy_worker(struct kthread_worker *worker)
1173 struct task_struct *task;
1175 task = worker->task;
1179 kthread_flush_worker(worker);
1181 WARN_ON(!list_empty(&worker->work_list));
1184 EXPORT_SYMBOL(kthread_destroy_worker);