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.
82 * kthread_should_stop - should this kthread return now?
84 * When someone calls kthread_stop() on your kthread, it will be woken
85 * and this will return true. You should then return, and your return
86 * value will be passed through to kthread_stop().
88 bool kthread_should_stop(void)
90 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
92 EXPORT_SYMBOL(kthread_should_stop);
95 * kthread_should_park - should this kthread park now?
97 * When someone calls kthread_park() on your kthread, it will be woken
98 * and this will return true. You should then do the necessary
99 * cleanup and call kthread_parkme()
101 * Similar to kthread_should_stop(), but this keeps the thread alive
102 * and in a park position. kthread_unpark() "restarts" the thread and
103 * calls the thread function again.
105 bool kthread_should_park(void)
107 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
109 EXPORT_SYMBOL_GPL(kthread_should_park);
112 * kthread_freezable_should_stop - should this freezable kthread return now?
113 * @was_frozen: optional out parameter, indicates whether %current was frozen
115 * kthread_should_stop() for freezable kthreads, which will enter
116 * refrigerator if necessary. This function is safe from kthread_stop() /
117 * freezer deadlock and freezable kthreads should use this function instead
118 * of calling try_to_freeze() directly.
120 bool kthread_freezable_should_stop(bool *was_frozen)
126 if (unlikely(freezing(current)))
127 frozen = __refrigerator(true);
130 *was_frozen = frozen;
132 return kthread_should_stop();
134 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
137 * kthread_data - return data value specified on kthread creation
138 * @task: kthread task in question
140 * Return the data value specified when kthread @task was created.
141 * The caller is responsible for ensuring the validity of @task when
142 * calling this function.
144 void *kthread_data(struct task_struct *task)
146 return to_kthread(task)->data;
150 * kthread_probe_data - speculative version of kthread_data()
151 * @task: possible kthread task in question
153 * @task could be a kthread task. Return the data value specified when it
154 * was created if accessible. If @task isn't a kthread task or its data is
155 * inaccessible for any reason, %NULL is returned. This function requires
156 * that @task itself is safe to dereference.
158 void *kthread_probe_data(struct task_struct *task)
160 struct kthread *kthread = to_kthread(task);
163 probe_kernel_read(&data, &kthread->data, sizeof(data));
167 static void __kthread_parkme(struct kthread *self)
169 __set_current_state(TASK_PARKED);
170 while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) {
171 if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags))
172 complete(&self->parked);
174 __set_current_state(TASK_PARKED);
176 clear_bit(KTHREAD_IS_PARKED, &self->flags);
177 __set_current_state(TASK_RUNNING);
180 void kthread_parkme(void)
182 __kthread_parkme(to_kthread(current));
184 EXPORT_SYMBOL_GPL(kthread_parkme);
186 static int kthread(void *_create)
188 /* Copy data: it's on kthread's stack */
189 struct kthread_create_info *create = _create;
190 int (*threadfn)(void *data) = create->threadfn;
191 void *data = create->data;
192 struct completion *done;
193 struct kthread *self;
196 self = kmalloc(sizeof(*self), GFP_KERNEL);
197 set_kthread_struct(self);
199 /* If user was SIGKILLed, I release the structure. */
200 done = xchg(&create->done, NULL);
207 create->result = ERR_PTR(-ENOMEM);
214 init_completion(&self->exited);
215 init_completion(&self->parked);
216 current->vfork_done = &self->exited;
218 /* OK, tell user we're spawned, wait for stop or wakeup */
219 __set_current_state(TASK_UNINTERRUPTIBLE);
220 create->result = current;
225 if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
226 __kthread_parkme(self);
227 ret = threadfn(data);
232 /* called from do_fork() to get node information for about to be created task */
233 int tsk_fork_get_node(struct task_struct *tsk)
236 if (tsk == kthreadd_task)
237 return tsk->pref_node_fork;
242 static void create_kthread(struct kthread_create_info *create)
247 current->pref_node_fork = create->node;
249 /* We want our own signal handler (we take no signals by default). */
250 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
252 /* If user was SIGKILLed, I release the structure. */
253 struct completion *done = xchg(&create->done, NULL);
259 create->result = ERR_PTR(pid);
264 static __printf(4, 0)
265 struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
266 void *data, int node,
267 const char namefmt[],
270 DECLARE_COMPLETION_ONSTACK(done);
271 struct task_struct *task;
272 struct kthread_create_info *create = kmalloc(sizeof(*create),
276 return ERR_PTR(-ENOMEM);
277 create->threadfn = threadfn;
280 create->done = &done;
282 spin_lock(&kthread_create_lock);
283 list_add_tail(&create->list, &kthread_create_list);
284 spin_unlock(&kthread_create_lock);
286 wake_up_process(kthreadd_task);
288 * Wait for completion in killable state, for I might be chosen by
289 * the OOM killer while kthreadd is trying to allocate memory for
292 if (unlikely(wait_for_completion_killable(&done))) {
294 * If I was SIGKILLed before kthreadd (or new kernel thread)
295 * calls complete(), leave the cleanup of this structure to
298 if (xchg(&create->done, NULL))
299 return ERR_PTR(-EINTR);
301 * kthreadd (or new kernel thread) will call complete()
304 wait_for_completion(&done);
306 task = create->result;
308 static const struct sched_param param = { .sched_priority = 0 };
310 vsnprintf(task->comm, sizeof(task->comm), namefmt, args);
312 * root may have changed our (kthreadd's) priority or CPU mask.
313 * The kernel thread should not inherit these properties.
315 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
316 set_cpus_allowed_ptr(task, cpu_all_mask);
323 * kthread_create_on_node - create a kthread.
324 * @threadfn: the function to run until signal_pending(current).
325 * @data: data ptr for @threadfn.
326 * @node: task and thread structures for the thread are allocated on this node
327 * @namefmt: printf-style name for the thread.
329 * Description: This helper function creates and names a kernel
330 * thread. The thread will be stopped: use wake_up_process() to start
331 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
332 * is affine to all CPUs.
334 * If thread is going to be bound on a particular cpu, give its node
335 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
336 * When woken, the thread will run @threadfn() with @data as its
337 * argument. @threadfn() can either call do_exit() directly if it is a
338 * standalone thread for which no one will call kthread_stop(), or
339 * return when 'kthread_should_stop()' is true (which means
340 * kthread_stop() has been called). The return value should be zero
341 * or a negative error number; it will be passed to kthread_stop().
343 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
345 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
346 void *data, int node,
347 const char namefmt[],
350 struct task_struct *task;
353 va_start(args, namefmt);
354 task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
359 EXPORT_SYMBOL(kthread_create_on_node);
361 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
365 if (!wait_task_inactive(p, state)) {
370 /* It's safe because the task is inactive. */
371 raw_spin_lock_irqsave(&p->pi_lock, flags);
372 do_set_cpus_allowed(p, mask);
373 p->flags |= PF_NO_SETAFFINITY;
374 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
377 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
379 __kthread_bind_mask(p, cpumask_of(cpu), state);
382 void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
384 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
388 * kthread_bind - bind a just-created kthread to a cpu.
389 * @p: thread created by kthread_create().
390 * @cpu: cpu (might not be online, must be possible) for @k to run on.
392 * Description: This function is equivalent to set_cpus_allowed(),
393 * except that @cpu doesn't need to be online, and the thread must be
394 * stopped (i.e., just returned from kthread_create()).
396 void kthread_bind(struct task_struct *p, unsigned int cpu)
398 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
400 EXPORT_SYMBOL(kthread_bind);
403 * kthread_create_on_cpu - Create a cpu bound kthread
404 * @threadfn: the function to run until signal_pending(current).
405 * @data: data ptr for @threadfn.
406 * @cpu: The cpu on which the thread should be bound,
407 * @namefmt: printf-style name for the thread. Format is restricted
408 * to "name.*%u". Code fills in cpu number.
410 * Description: This helper function creates and names a kernel thread
411 * The thread will be woken and put into park mode.
413 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
414 void *data, unsigned int cpu,
417 struct task_struct *p;
419 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
423 kthread_bind(p, cpu);
424 /* CPU hotplug need to bind once again when unparking the thread. */
425 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
426 to_kthread(p)->cpu = cpu;
431 * kthread_unpark - unpark a thread created by kthread_create().
432 * @k: thread created by kthread_create().
434 * Sets kthread_should_park() for @k to return false, wakes it, and
435 * waits for it to return. If the thread is marked percpu then its
436 * bound to the cpu again.
438 void kthread_unpark(struct task_struct *k)
440 struct kthread *kthread = to_kthread(k);
442 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
444 * We clear the IS_PARKED bit here as we don't wait
445 * until the task has left the park code. So if we'd
446 * park before that happens we'd see the IS_PARKED bit
447 * which might be about to be cleared.
449 if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
451 * Newly created kthread was parked when the CPU was offline.
452 * The binding was lost and we need to set it again.
454 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
455 __kthread_bind(k, kthread->cpu, TASK_PARKED);
456 wake_up_state(k, TASK_PARKED);
459 EXPORT_SYMBOL_GPL(kthread_unpark);
462 * kthread_park - park a thread created by kthread_create().
463 * @k: thread created by kthread_create().
465 * Sets kthread_should_park() for @k to return true, wakes it, and
466 * waits for it to return. This can also be called after kthread_create()
467 * instead of calling wake_up_process(): the thread will park without
468 * calling threadfn().
470 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
471 * If called by the kthread itself just the park bit is set.
473 int kthread_park(struct task_struct *k)
475 struct kthread *kthread = to_kthread(k);
477 if (WARN_ON(k->flags & PF_EXITING))
480 if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
481 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
484 wait_for_completion(&kthread->parked);
490 EXPORT_SYMBOL_GPL(kthread_park);
493 * kthread_stop - stop a thread created by kthread_create().
494 * @k: thread created by kthread_create().
496 * Sets kthread_should_stop() for @k to return true, wakes it, and
497 * waits for it to exit. This can also be called after kthread_create()
498 * instead of calling wake_up_process(): the thread will exit without
499 * calling threadfn().
501 * If threadfn() may call do_exit() itself, the caller must ensure
502 * task_struct can't go away.
504 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
507 int kthread_stop(struct task_struct *k)
509 struct kthread *kthread;
512 trace_sched_kthread_stop(k);
515 kthread = to_kthread(k);
516 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
519 wait_for_completion(&kthread->exited);
523 trace_sched_kthread_stop_ret(ret);
526 EXPORT_SYMBOL(kthread_stop);
528 int kthreadd(void *unused)
530 struct task_struct *tsk = current;
532 /* Setup a clean context for our children to inherit. */
533 set_task_comm(tsk, "kthreadd");
535 set_cpus_allowed_ptr(tsk, cpu_all_mask);
536 set_mems_allowed(node_states[N_MEMORY]);
538 current->flags |= PF_NOFREEZE;
541 set_current_state(TASK_INTERRUPTIBLE);
542 if (list_empty(&kthread_create_list))
544 __set_current_state(TASK_RUNNING);
546 spin_lock(&kthread_create_lock);
547 while (!list_empty(&kthread_create_list)) {
548 struct kthread_create_info *create;
550 create = list_entry(kthread_create_list.next,
551 struct kthread_create_info, list);
552 list_del_init(&create->list);
553 spin_unlock(&kthread_create_lock);
555 create_kthread(create);
557 spin_lock(&kthread_create_lock);
559 spin_unlock(&kthread_create_lock);
565 void __kthread_init_worker(struct kthread_worker *worker,
567 struct lock_class_key *key)
569 memset(worker, 0, sizeof(struct kthread_worker));
570 spin_lock_init(&worker->lock);
571 lockdep_set_class_and_name(&worker->lock, key, name);
572 INIT_LIST_HEAD(&worker->work_list);
573 INIT_LIST_HEAD(&worker->delayed_work_list);
575 EXPORT_SYMBOL_GPL(__kthread_init_worker);
578 * kthread_worker_fn - kthread function to process kthread_worker
579 * @worker_ptr: pointer to initialized kthread_worker
581 * This function implements the main cycle of kthread worker. It processes
582 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
585 * The works are not allowed to keep any locks, disable preemption or interrupts
586 * when they finish. There is defined a safe point for freezing when one work
587 * finishes and before a new one is started.
589 * Also the works must not be handled by more than one worker at the same time,
590 * see also kthread_queue_work().
592 int kthread_worker_fn(void *worker_ptr)
594 struct kthread_worker *worker = worker_ptr;
595 struct kthread_work *work;
598 * FIXME: Update the check and remove the assignment when all kthread
599 * worker users are created using kthread_create_worker*() functions.
601 WARN_ON(worker->task && worker->task != current);
602 worker->task = current;
604 if (worker->flags & KTW_FREEZABLE)
608 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
610 if (kthread_should_stop()) {
611 __set_current_state(TASK_RUNNING);
612 spin_lock_irq(&worker->lock);
614 spin_unlock_irq(&worker->lock);
619 spin_lock_irq(&worker->lock);
620 if (!list_empty(&worker->work_list)) {
621 work = list_first_entry(&worker->work_list,
622 struct kthread_work, node);
623 list_del_init(&work->node);
625 worker->current_work = work;
626 spin_unlock_irq(&worker->lock);
629 __set_current_state(TASK_RUNNING);
631 } else if (!freezing(current))
637 EXPORT_SYMBOL_GPL(kthread_worker_fn);
639 static __printf(3, 0) struct kthread_worker *
640 __kthread_create_worker(int cpu, unsigned int flags,
641 const char namefmt[], va_list args)
643 struct kthread_worker *worker;
644 struct task_struct *task;
647 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
649 return ERR_PTR(-ENOMEM);
651 kthread_init_worker(worker);
654 node = cpu_to_node(cpu);
656 task = __kthread_create_on_node(kthread_worker_fn, worker,
657 node, namefmt, args);
662 kthread_bind(task, cpu);
664 worker->flags = flags;
666 wake_up_process(task);
671 return ERR_CAST(task);
675 * kthread_create_worker - create a kthread worker
676 * @flags: flags modifying the default behavior of the worker
677 * @namefmt: printf-style name for the kthread worker (task).
679 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
680 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
681 * when the worker was SIGKILLed.
683 struct kthread_worker *
684 kthread_create_worker(unsigned int flags, const char namefmt[], ...)
686 struct kthread_worker *worker;
689 va_start(args, namefmt);
690 worker = __kthread_create_worker(-1, flags, namefmt, args);
695 EXPORT_SYMBOL(kthread_create_worker);
698 * kthread_create_worker_on_cpu - create a kthread worker and bind it
699 * it to a given CPU and the associated NUMA node.
701 * @flags: flags modifying the default behavior of the worker
702 * @namefmt: printf-style name for the kthread worker (task).
704 * Use a valid CPU number if you want to bind the kthread worker
705 * to the given CPU and the associated NUMA node.
707 * A good practice is to add the cpu number also into the worker name.
708 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
710 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
711 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
712 * when the worker was SIGKILLed.
714 struct kthread_worker *
715 kthread_create_worker_on_cpu(int cpu, unsigned int flags,
716 const char namefmt[], ...)
718 struct kthread_worker *worker;
721 va_start(args, namefmt);
722 worker = __kthread_create_worker(cpu, flags, namefmt, args);
727 EXPORT_SYMBOL(kthread_create_worker_on_cpu);
730 * Returns true when the work could not be queued at the moment.
731 * It happens when it is already pending in a worker list
732 * or when it is being cancelled.
734 static inline bool queuing_blocked(struct kthread_worker *worker,
735 struct kthread_work *work)
737 lockdep_assert_held(&worker->lock);
739 return !list_empty(&work->node) || work->canceling;
742 static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
743 struct kthread_work *work)
745 lockdep_assert_held(&worker->lock);
746 WARN_ON_ONCE(!list_empty(&work->node));
747 /* Do not use a work with >1 worker, see kthread_queue_work() */
748 WARN_ON_ONCE(work->worker && work->worker != worker);
751 /* insert @work before @pos in @worker */
752 static void kthread_insert_work(struct kthread_worker *worker,
753 struct kthread_work *work,
754 struct list_head *pos)
756 kthread_insert_work_sanity_check(worker, work);
758 list_add_tail(&work->node, pos);
759 work->worker = worker;
760 if (!worker->current_work && likely(worker->task))
761 wake_up_process(worker->task);
765 * kthread_queue_work - queue a kthread_work
766 * @worker: target kthread_worker
767 * @work: kthread_work to queue
769 * Queue @work to work processor @task for async execution. @task
770 * must have been created with kthread_worker_create(). Returns %true
771 * if @work was successfully queued, %false if it was already pending.
773 * Reinitialize the work if it needs to be used by another worker.
774 * For example, when the worker was stopped and started again.
776 bool kthread_queue_work(struct kthread_worker *worker,
777 struct kthread_work *work)
782 spin_lock_irqsave(&worker->lock, flags);
783 if (!queuing_blocked(worker, work)) {
784 kthread_insert_work(worker, work, &worker->work_list);
787 spin_unlock_irqrestore(&worker->lock, flags);
790 EXPORT_SYMBOL_GPL(kthread_queue_work);
793 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
794 * delayed work when the timer expires.
795 * @__data: pointer to the data associated with the timer
797 * The format of the function is defined by struct timer_list.
798 * It should have been called from irqsafe timer with irq already off.
800 void kthread_delayed_work_timer_fn(unsigned long __data)
802 struct kthread_delayed_work *dwork =
803 (struct kthread_delayed_work *)__data;
804 struct kthread_work *work = &dwork->work;
805 struct kthread_worker *worker = work->worker;
808 * This might happen when a pending work is reinitialized.
809 * It means that it is used a wrong way.
811 if (WARN_ON_ONCE(!worker))
814 spin_lock(&worker->lock);
815 /* Work must not be used with >1 worker, see kthread_queue_work(). */
816 WARN_ON_ONCE(work->worker != worker);
818 /* Move the work from worker->delayed_work_list. */
819 WARN_ON_ONCE(list_empty(&work->node));
820 list_del_init(&work->node);
821 kthread_insert_work(worker, work, &worker->work_list);
823 spin_unlock(&worker->lock);
825 EXPORT_SYMBOL(kthread_delayed_work_timer_fn);
827 void __kthread_queue_delayed_work(struct kthread_worker *worker,
828 struct kthread_delayed_work *dwork,
831 struct timer_list *timer = &dwork->timer;
832 struct kthread_work *work = &dwork->work;
834 WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn ||
835 timer->data != (unsigned long)dwork);
838 * If @delay is 0, queue @dwork->work immediately. This is for
839 * both optimization and correctness. The earliest @timer can
840 * expire is on the closest next tick and delayed_work users depend
841 * on that there's no such delay when @delay is 0.
844 kthread_insert_work(worker, work, &worker->work_list);
848 /* Be paranoid and try to detect possible races already now. */
849 kthread_insert_work_sanity_check(worker, work);
851 list_add(&work->node, &worker->delayed_work_list);
852 work->worker = worker;
853 timer->expires = jiffies + delay;
858 * kthread_queue_delayed_work - queue the associated kthread work
860 * @worker: target kthread_worker
861 * @dwork: kthread_delayed_work to queue
862 * @delay: number of jiffies to wait before queuing
864 * If the work has not been pending it starts a timer that will queue
865 * the work after the given @delay. If @delay is zero, it queues the
868 * Return: %false if the @work has already been pending. It means that
869 * either the timer was running or the work was queued. It returns %true
872 bool kthread_queue_delayed_work(struct kthread_worker *worker,
873 struct kthread_delayed_work *dwork,
876 struct kthread_work *work = &dwork->work;
880 spin_lock_irqsave(&worker->lock, flags);
882 if (!queuing_blocked(worker, work)) {
883 __kthread_queue_delayed_work(worker, dwork, delay);
887 spin_unlock_irqrestore(&worker->lock, flags);
890 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
892 struct kthread_flush_work {
893 struct kthread_work work;
894 struct completion done;
897 static void kthread_flush_work_fn(struct kthread_work *work)
899 struct kthread_flush_work *fwork =
900 container_of(work, struct kthread_flush_work, work);
901 complete(&fwork->done);
905 * kthread_flush_work - flush a kthread_work
906 * @work: work to flush
908 * If @work is queued or executing, wait for it to finish execution.
910 void kthread_flush_work(struct kthread_work *work)
912 struct kthread_flush_work fwork = {
913 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
914 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
916 struct kthread_worker *worker;
919 worker = work->worker;
923 spin_lock_irq(&worker->lock);
924 /* Work must not be used with >1 worker, see kthread_queue_work(). */
925 WARN_ON_ONCE(work->worker != worker);
927 if (!list_empty(&work->node))
928 kthread_insert_work(worker, &fwork.work, work->node.next);
929 else if (worker->current_work == work)
930 kthread_insert_work(worker, &fwork.work,
931 worker->work_list.next);
935 spin_unlock_irq(&worker->lock);
938 wait_for_completion(&fwork.done);
940 EXPORT_SYMBOL_GPL(kthread_flush_work);
943 * This function removes the work from the worker queue. Also it makes sure
944 * that it won't get queued later via the delayed work's timer.
946 * The work might still be in use when this function finishes. See the
947 * current_work proceed by the worker.
949 * Return: %true if @work was pending and successfully canceled,
950 * %false if @work was not pending
952 static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
953 unsigned long *flags)
955 /* Try to cancel the timer if exists. */
957 struct kthread_delayed_work *dwork =
958 container_of(work, struct kthread_delayed_work, work);
959 struct kthread_worker *worker = work->worker;
962 * del_timer_sync() must be called to make sure that the timer
963 * callback is not running. The lock must be temporary released
964 * to avoid a deadlock with the callback. In the meantime,
965 * any queuing is blocked by setting the canceling counter.
968 spin_unlock_irqrestore(&worker->lock, *flags);
969 del_timer_sync(&dwork->timer);
970 spin_lock_irqsave(&worker->lock, *flags);
975 * Try to remove the work from a worker list. It might either
976 * be from worker->work_list or from worker->delayed_work_list.
978 if (!list_empty(&work->node)) {
979 list_del_init(&work->node);
987 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
988 * @worker: kthread worker to use
989 * @dwork: kthread delayed work to queue
990 * @delay: number of jiffies to wait before queuing
992 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
993 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
994 * @work is guaranteed to be queued immediately.
996 * Return: %true if @dwork was pending and its timer was modified,
999 * A special case is when the work is being canceled in parallel.
1000 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1001 * or yet another kthread_mod_delayed_work() call. We let the other command
1002 * win and return %false here. The caller is supposed to synchronize these
1003 * operations a reasonable way.
1005 * This function is safe to call from any context including IRQ handler.
1006 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1009 bool kthread_mod_delayed_work(struct kthread_worker *worker,
1010 struct kthread_delayed_work *dwork,
1011 unsigned long delay)
1013 struct kthread_work *work = &dwork->work;
1014 unsigned long flags;
1017 spin_lock_irqsave(&worker->lock, flags);
1019 /* Do not bother with canceling when never queued. */
1023 /* Work must not be used with >1 worker, see kthread_queue_work() */
1024 WARN_ON_ONCE(work->worker != worker);
1026 /* Do not fight with another command that is canceling this work. */
1027 if (work->canceling)
1030 ret = __kthread_cancel_work(work, true, &flags);
1032 __kthread_queue_delayed_work(worker, dwork, delay);
1034 spin_unlock_irqrestore(&worker->lock, flags);
1037 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1039 static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1041 struct kthread_worker *worker = work->worker;
1042 unsigned long flags;
1048 spin_lock_irqsave(&worker->lock, flags);
1049 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1050 WARN_ON_ONCE(work->worker != worker);
1052 ret = __kthread_cancel_work(work, is_dwork, &flags);
1054 if (worker->current_work != work)
1058 * The work is in progress and we need to wait with the lock released.
1059 * In the meantime, block any queuing by setting the canceling counter.
1062 spin_unlock_irqrestore(&worker->lock, flags);
1063 kthread_flush_work(work);
1064 spin_lock_irqsave(&worker->lock, flags);
1068 spin_unlock_irqrestore(&worker->lock, flags);
1074 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1075 * @work: the kthread work to cancel
1077 * Cancel @work and wait for its execution to finish. This function
1078 * can be used even if the work re-queues itself. On return from this
1079 * function, @work is guaranteed to be not pending or executing on any CPU.
1081 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1082 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1084 * The caller must ensure that the worker on which @work was last
1085 * queued can't be destroyed before this function returns.
1087 * Return: %true if @work was pending, %false otherwise.
1089 bool kthread_cancel_work_sync(struct kthread_work *work)
1091 return __kthread_cancel_work_sync(work, false);
1093 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1096 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1097 * wait for it to finish.
1098 * @dwork: the kthread delayed work to cancel
1100 * This is kthread_cancel_work_sync() for delayed works.
1102 * Return: %true if @dwork was pending, %false otherwise.
1104 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1106 return __kthread_cancel_work_sync(&dwork->work, true);
1108 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1111 * kthread_flush_worker - flush all current works on a kthread_worker
1112 * @worker: worker to flush
1114 * Wait until all currently executing or pending works on @worker are
1117 void kthread_flush_worker(struct kthread_worker *worker)
1119 struct kthread_flush_work fwork = {
1120 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1121 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1124 kthread_queue_work(worker, &fwork.work);
1125 wait_for_completion(&fwork.done);
1127 EXPORT_SYMBOL_GPL(kthread_flush_worker);
1130 * kthread_destroy_worker - destroy a kthread worker
1131 * @worker: worker to be destroyed
1133 * Flush and destroy @worker. The simple flush is enough because the kthread
1134 * worker API is used only in trivial scenarios. There are no multi-step state
1137 void kthread_destroy_worker(struct kthread_worker *worker)
1139 struct task_struct *task;
1141 task = worker->task;
1145 kthread_flush_worker(worker);
1147 WARN_ON(!list_empty(&worker->work_list));
1150 EXPORT_SYMBOL(kthread_destroy_worker);