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 <uapi/linux/sched/types.h>
9 #include <linux/sched.h>
10 #include <linux/sched/task.h>
11 #include <linux/kthread.h>
12 #include <linux/completion.h>
13 #include <linux/err.h>
14 #include <linux/cpuset.h>
15 #include <linux/unistd.h>
16 #include <linux/file.h>
17 #include <linux/export.h>
18 #include <linux/mutex.h>
19 #include <linux/slab.h>
20 #include <linux/freezer.h>
21 #include <linux/ptrace.h>
22 #include <linux/uaccess.h>
23 #include <linux/numa.h>
24 #include <trace/events/sched.h>
26 static DEFINE_SPINLOCK(kthread_create_lock);
27 static LIST_HEAD(kthread_create_list);
28 struct task_struct *kthreadd_task;
30 struct kthread_create_info
32 /* Information passed to kthread() from kthreadd. */
33 int (*threadfn)(void *data);
37 /* Result passed back to kthread_create() from kthreadd. */
38 struct task_struct *result;
39 struct completion *done;
41 struct list_head list;
48 struct completion parked;
49 struct completion exited;
50 #ifdef CONFIG_BLK_CGROUP
51 struct cgroup_subsys_state *blkcg_css;
56 KTHREAD_IS_PER_CPU = 0,
61 static inline void set_kthread_struct(void *kthread)
64 * We abuse ->set_child_tid to avoid the new member and because it
65 * can't be wrongly copied by copy_process(). We also rely on fact
66 * that the caller can't exec, so PF_KTHREAD can't be cleared.
68 current->set_child_tid = (__force void __user *)kthread;
71 static inline struct kthread *to_kthread(struct task_struct *k)
73 WARN_ON(!(k->flags & PF_KTHREAD));
74 return (__force void *)k->set_child_tid;
77 void free_kthread_struct(struct task_struct *k)
79 struct kthread *kthread;
82 * Can be NULL if this kthread was created by kernel_thread()
83 * or if kmalloc() in kthread() failed.
85 kthread = to_kthread(k);
86 #ifdef CONFIG_BLK_CGROUP
87 WARN_ON_ONCE(kthread && kthread->blkcg_css);
93 * kthread_should_stop - should this kthread return now?
95 * When someone calls kthread_stop() on your kthread, it will be woken
96 * and this will return true. You should then return, and your return
97 * value will be passed through to kthread_stop().
99 bool kthread_should_stop(void)
101 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
103 EXPORT_SYMBOL(kthread_should_stop);
106 * kthread_should_park - should this kthread park now?
108 * When someone calls kthread_park() on your kthread, it will be woken
109 * and this will return true. You should then do the necessary
110 * cleanup and call kthread_parkme()
112 * Similar to kthread_should_stop(), but this keeps the thread alive
113 * and in a park position. kthread_unpark() "restarts" the thread and
114 * calls the thread function again.
116 bool kthread_should_park(void)
118 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
120 EXPORT_SYMBOL_GPL(kthread_should_park);
123 * kthread_freezable_should_stop - should this freezable kthread return now?
124 * @was_frozen: optional out parameter, indicates whether %current was frozen
126 * kthread_should_stop() for freezable kthreads, which will enter
127 * refrigerator if necessary. This function is safe from kthread_stop() /
128 * freezer deadlock and freezable kthreads should use this function instead
129 * of calling try_to_freeze() directly.
131 bool kthread_freezable_should_stop(bool *was_frozen)
137 if (unlikely(freezing(current)))
138 frozen = __refrigerator(true);
141 *was_frozen = frozen;
143 return kthread_should_stop();
145 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
148 * kthread_data - return data value specified on kthread creation
149 * @task: kthread task in question
151 * Return the data value specified when kthread @task was created.
152 * The caller is responsible for ensuring the validity of @task when
153 * calling this function.
155 void *kthread_data(struct task_struct *task)
157 return to_kthread(task)->data;
161 * kthread_probe_data - speculative version of kthread_data()
162 * @task: possible kthread task in question
164 * @task could be a kthread task. Return the data value specified when it
165 * was created if accessible. If @task isn't a kthread task or its data is
166 * inaccessible for any reason, %NULL is returned. This function requires
167 * that @task itself is safe to dereference.
169 void *kthread_probe_data(struct task_struct *task)
171 struct kthread *kthread = to_kthread(task);
174 probe_kernel_read(&data, &kthread->data, sizeof(data));
178 static void __kthread_parkme(struct kthread *self)
182 * TASK_PARKED is a special state; we must serialize against
183 * possible pending wakeups to avoid store-store collisions on
186 * Such a collision might possibly result in the task state
187 * changin from TASK_PARKED and us failing the
188 * wait_task_inactive() in kthread_park().
190 set_special_state(TASK_PARKED);
191 if (!test_bit(KTHREAD_SHOULD_PARK, &self->flags))
194 complete(&self->parked);
197 __set_current_state(TASK_RUNNING);
200 void kthread_parkme(void)
202 __kthread_parkme(to_kthread(current));
204 EXPORT_SYMBOL_GPL(kthread_parkme);
206 static int kthread(void *_create)
208 /* Copy data: it's on kthread's stack */
209 struct kthread_create_info *create = _create;
210 int (*threadfn)(void *data) = create->threadfn;
211 void *data = create->data;
212 struct completion *done;
213 struct kthread *self;
216 self = kzalloc(sizeof(*self), GFP_KERNEL);
217 set_kthread_struct(self);
219 /* If user was SIGKILLed, I release the structure. */
220 done = xchg(&create->done, NULL);
227 create->result = ERR_PTR(-ENOMEM);
233 init_completion(&self->exited);
234 init_completion(&self->parked);
235 current->vfork_done = &self->exited;
237 /* OK, tell user we're spawned, wait for stop or wakeup */
238 __set_current_state(TASK_UNINTERRUPTIBLE);
239 create->result = current;
244 if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
245 cgroup_kthread_ready();
246 __kthread_parkme(self);
247 ret = threadfn(data);
252 /* called from do_fork() to get node information for about to be created task */
253 int tsk_fork_get_node(struct task_struct *tsk)
256 if (tsk == kthreadd_task)
257 return tsk->pref_node_fork;
262 static void create_kthread(struct kthread_create_info *create)
267 current->pref_node_fork = create->node;
269 /* We want our own signal handler (we take no signals by default). */
270 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
272 /* If user was SIGKILLed, I release the structure. */
273 struct completion *done = xchg(&create->done, NULL);
279 create->result = ERR_PTR(pid);
284 static __printf(4, 0)
285 struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
286 void *data, int node,
287 const char namefmt[],
290 DECLARE_COMPLETION_ONSTACK(done);
291 struct task_struct *task;
292 struct kthread_create_info *create = kmalloc(sizeof(*create),
296 return ERR_PTR(-ENOMEM);
297 create->threadfn = threadfn;
300 create->done = &done;
302 spin_lock(&kthread_create_lock);
303 list_add_tail(&create->list, &kthread_create_list);
304 spin_unlock(&kthread_create_lock);
306 wake_up_process(kthreadd_task);
308 * Wait for completion in killable state, for I might be chosen by
309 * the OOM killer while kthreadd is trying to allocate memory for
312 if (unlikely(wait_for_completion_killable(&done))) {
314 * If I was SIGKILLed before kthreadd (or new kernel thread)
315 * calls complete(), leave the cleanup of this structure to
318 if (xchg(&create->done, NULL))
319 return ERR_PTR(-EINTR);
321 * kthreadd (or new kernel thread) will call complete()
324 wait_for_completion(&done);
326 task = create->result;
328 static const struct sched_param param = { .sched_priority = 0 };
329 char name[TASK_COMM_LEN];
332 * task is already visible to other tasks, so updating
333 * COMM must be protected.
335 vsnprintf(name, sizeof(name), namefmt, args);
336 set_task_comm(task, name);
338 * root may have changed our (kthreadd's) priority or CPU mask.
339 * The kernel thread should not inherit these properties.
341 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
342 set_cpus_allowed_ptr(task, cpu_all_mask);
349 * kthread_create_on_node - create a kthread.
350 * @threadfn: the function to run until signal_pending(current).
351 * @data: data ptr for @threadfn.
352 * @node: task and thread structures for the thread are allocated on this node
353 * @namefmt: printf-style name for the thread.
355 * Description: This helper function creates and names a kernel
356 * thread. The thread will be stopped: use wake_up_process() to start
357 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
358 * is affine to all CPUs.
360 * If thread is going to be bound on a particular cpu, give its node
361 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
362 * When woken, the thread will run @threadfn() with @data as its
363 * argument. @threadfn() can either call do_exit() directly if it is a
364 * standalone thread for which no one will call kthread_stop(), or
365 * return when 'kthread_should_stop()' is true (which means
366 * kthread_stop() has been called). The return value should be zero
367 * or a negative error number; it will be passed to kthread_stop().
369 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
371 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
372 void *data, int node,
373 const char namefmt[],
376 struct task_struct *task;
379 va_start(args, namefmt);
380 task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
385 EXPORT_SYMBOL(kthread_create_on_node);
387 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
391 if (!wait_task_inactive(p, state)) {
396 /* It's safe because the task is inactive. */
397 raw_spin_lock_irqsave(&p->pi_lock, flags);
398 do_set_cpus_allowed(p, mask);
399 p->flags |= PF_NO_SETAFFINITY;
400 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
403 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
405 __kthread_bind_mask(p, cpumask_of(cpu), state);
408 void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
410 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
414 * kthread_bind - bind a just-created kthread to a cpu.
415 * @p: thread created by kthread_create().
416 * @cpu: cpu (might not be online, must be possible) for @k to run on.
418 * Description: This function is equivalent to set_cpus_allowed(),
419 * except that @cpu doesn't need to be online, and the thread must be
420 * stopped (i.e., just returned from kthread_create()).
422 void kthread_bind(struct task_struct *p, unsigned int cpu)
424 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
426 EXPORT_SYMBOL(kthread_bind);
429 * kthread_create_on_cpu - Create a cpu bound kthread
430 * @threadfn: the function to run until signal_pending(current).
431 * @data: data ptr for @threadfn.
432 * @cpu: The cpu on which the thread should be bound,
433 * @namefmt: printf-style name for the thread. Format is restricted
434 * to "name.*%u". Code fills in cpu number.
436 * Description: This helper function creates and names a kernel thread
437 * The thread will be woken and put into park mode.
439 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
440 void *data, unsigned int cpu,
443 struct task_struct *p;
445 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
449 kthread_bind(p, cpu);
450 /* CPU hotplug need to bind once again when unparking the thread. */
451 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
452 to_kthread(p)->cpu = cpu;
457 * kthread_unpark - unpark a thread created by kthread_create().
458 * @k: thread created by kthread_create().
460 * Sets kthread_should_park() for @k to return false, wakes it, and
461 * waits for it to return. If the thread is marked percpu then its
462 * bound to the cpu again.
464 void kthread_unpark(struct task_struct *k)
466 struct kthread *kthread = to_kthread(k);
469 * Newly created kthread was parked when the CPU was offline.
470 * The binding was lost and we need to set it again.
472 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
473 __kthread_bind(k, kthread->cpu, TASK_PARKED);
475 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
477 * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup.
479 wake_up_state(k, TASK_PARKED);
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_kthread(k);
499 if (WARN_ON(k->flags & PF_EXITING))
502 if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK, &kthread->flags)))
505 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
509 * Wait for __kthread_parkme() to complete(), this means we
510 * _will_ have TASK_PARKED and are about to call schedule().
512 wait_for_completion(&kthread->parked);
514 * Now wait for that schedule() to complete and the task to
517 WARN_ON_ONCE(!wait_task_inactive(k, TASK_PARKED));
522 EXPORT_SYMBOL_GPL(kthread_park);
525 * kthread_stop - stop a thread created by kthread_create().
526 * @k: thread created by kthread_create().
528 * Sets kthread_should_stop() for @k to return true, wakes it, and
529 * waits for it to exit. This can also be called after kthread_create()
530 * instead of calling wake_up_process(): the thread will exit without
531 * calling threadfn().
533 * If threadfn() may call do_exit() itself, the caller must ensure
534 * task_struct can't go away.
536 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
539 int kthread_stop(struct task_struct *k)
541 struct kthread *kthread;
544 trace_sched_kthread_stop(k);
547 kthread = to_kthread(k);
548 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
551 wait_for_completion(&kthread->exited);
555 trace_sched_kthread_stop_ret(ret);
558 EXPORT_SYMBOL(kthread_stop);
560 int kthreadd(void *unused)
562 struct task_struct *tsk = current;
564 /* Setup a clean context for our children to inherit. */
565 set_task_comm(tsk, "kthreadd");
567 set_cpus_allowed_ptr(tsk, cpu_all_mask);
568 set_mems_allowed(node_states[N_MEMORY]);
570 current->flags |= PF_NOFREEZE;
571 cgroup_init_kthreadd();
574 set_current_state(TASK_INTERRUPTIBLE);
575 if (list_empty(&kthread_create_list))
577 __set_current_state(TASK_RUNNING);
579 spin_lock(&kthread_create_lock);
580 while (!list_empty(&kthread_create_list)) {
581 struct kthread_create_info *create;
583 create = list_entry(kthread_create_list.next,
584 struct kthread_create_info, list);
585 list_del_init(&create->list);
586 spin_unlock(&kthread_create_lock);
588 create_kthread(create);
590 spin_lock(&kthread_create_lock);
592 spin_unlock(&kthread_create_lock);
598 void __kthread_init_worker(struct kthread_worker *worker,
600 struct lock_class_key *key)
602 memset(worker, 0, sizeof(struct kthread_worker));
603 spin_lock_init(&worker->lock);
604 lockdep_set_class_and_name(&worker->lock, key, name);
605 INIT_LIST_HEAD(&worker->work_list);
606 INIT_LIST_HEAD(&worker->delayed_work_list);
608 EXPORT_SYMBOL_GPL(__kthread_init_worker);
611 * kthread_worker_fn - kthread function to process kthread_worker
612 * @worker_ptr: pointer to initialized kthread_worker
614 * This function implements the main cycle of kthread worker. It processes
615 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
618 * The works are not allowed to keep any locks, disable preemption or interrupts
619 * when they finish. There is defined a safe point for freezing when one work
620 * finishes and before a new one is started.
622 * Also the works must not be handled by more than one worker at the same time,
623 * see also kthread_queue_work().
625 int kthread_worker_fn(void *worker_ptr)
627 struct kthread_worker *worker = worker_ptr;
628 struct kthread_work *work;
631 * FIXME: Update the check and remove the assignment when all kthread
632 * worker users are created using kthread_create_worker*() functions.
634 WARN_ON(worker->task && worker->task != current);
635 worker->task = current;
637 if (worker->flags & KTW_FREEZABLE)
641 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
643 if (kthread_should_stop()) {
644 __set_current_state(TASK_RUNNING);
645 spin_lock_irq(&worker->lock);
647 spin_unlock_irq(&worker->lock);
652 spin_lock_irq(&worker->lock);
653 if (!list_empty(&worker->work_list)) {
654 work = list_first_entry(&worker->work_list,
655 struct kthread_work, node);
656 list_del_init(&work->node);
658 worker->current_work = work;
659 spin_unlock_irq(&worker->lock);
662 __set_current_state(TASK_RUNNING);
664 } else if (!freezing(current))
671 EXPORT_SYMBOL_GPL(kthread_worker_fn);
673 static __printf(3, 0) struct kthread_worker *
674 __kthread_create_worker(int cpu, unsigned int flags,
675 const char namefmt[], va_list args)
677 struct kthread_worker *worker;
678 struct task_struct *task;
679 int node = NUMA_NO_NODE;
681 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
683 return ERR_PTR(-ENOMEM);
685 kthread_init_worker(worker);
688 node = cpu_to_node(cpu);
690 task = __kthread_create_on_node(kthread_worker_fn, worker,
691 node, namefmt, args);
696 kthread_bind(task, cpu);
698 worker->flags = flags;
700 wake_up_process(task);
705 return ERR_CAST(task);
709 * kthread_create_worker - create a kthread worker
710 * @flags: flags modifying the default behavior of the worker
711 * @namefmt: printf-style name for the kthread worker (task).
713 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
714 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
715 * when the worker was SIGKILLed.
717 struct kthread_worker *
718 kthread_create_worker(unsigned int flags, const char namefmt[], ...)
720 struct kthread_worker *worker;
723 va_start(args, namefmt);
724 worker = __kthread_create_worker(-1, flags, namefmt, args);
729 EXPORT_SYMBOL(kthread_create_worker);
732 * kthread_create_worker_on_cpu - create a kthread worker and bind it
733 * it to a given CPU and the associated NUMA node.
735 * @flags: flags modifying the default behavior of the worker
736 * @namefmt: printf-style name for the kthread worker (task).
738 * Use a valid CPU number if you want to bind the kthread worker
739 * to the given CPU and the associated NUMA node.
741 * A good practice is to add the cpu number also into the worker name.
742 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
744 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
745 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
746 * when the worker was SIGKILLed.
748 struct kthread_worker *
749 kthread_create_worker_on_cpu(int cpu, unsigned int flags,
750 const char namefmt[], ...)
752 struct kthread_worker *worker;
755 va_start(args, namefmt);
756 worker = __kthread_create_worker(cpu, flags, namefmt, args);
761 EXPORT_SYMBOL(kthread_create_worker_on_cpu);
764 * Returns true when the work could not be queued at the moment.
765 * It happens when it is already pending in a worker list
766 * or when it is being cancelled.
768 static inline bool queuing_blocked(struct kthread_worker *worker,
769 struct kthread_work *work)
771 lockdep_assert_held(&worker->lock);
773 return !list_empty(&work->node) || work->canceling;
776 static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
777 struct kthread_work *work)
779 lockdep_assert_held(&worker->lock);
780 WARN_ON_ONCE(!list_empty(&work->node));
781 /* Do not use a work with >1 worker, see kthread_queue_work() */
782 WARN_ON_ONCE(work->worker && work->worker != worker);
785 /* insert @work before @pos in @worker */
786 static void kthread_insert_work(struct kthread_worker *worker,
787 struct kthread_work *work,
788 struct list_head *pos)
790 kthread_insert_work_sanity_check(worker, work);
792 list_add_tail(&work->node, pos);
793 work->worker = worker;
794 if (!worker->current_work && likely(worker->task))
795 wake_up_process(worker->task);
799 * kthread_queue_work - queue a kthread_work
800 * @worker: target kthread_worker
801 * @work: kthread_work to queue
803 * Queue @work to work processor @task for async execution. @task
804 * must have been created with kthread_worker_create(). Returns %true
805 * if @work was successfully queued, %false if it was already pending.
807 * Reinitialize the work if it needs to be used by another worker.
808 * For example, when the worker was stopped and started again.
810 bool kthread_queue_work(struct kthread_worker *worker,
811 struct kthread_work *work)
816 spin_lock_irqsave(&worker->lock, flags);
817 if (!queuing_blocked(worker, work)) {
818 kthread_insert_work(worker, work, &worker->work_list);
821 spin_unlock_irqrestore(&worker->lock, flags);
824 EXPORT_SYMBOL_GPL(kthread_queue_work);
827 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
828 * delayed work when the timer expires.
829 * @t: pointer to the expired timer
831 * The format of the function is defined by struct timer_list.
832 * It should have been called from irqsafe timer with irq already off.
834 void kthread_delayed_work_timer_fn(struct timer_list *t)
836 struct kthread_delayed_work *dwork = from_timer(dwork, t, timer);
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);
870 * If @delay is 0, queue @dwork->work immediately. This is for
871 * both optimization and correctness. The earliest @timer can
872 * expire is on the closest next tick and delayed_work users depend
873 * on that there's no such delay when @delay is 0.
876 kthread_insert_work(worker, work, &worker->work_list);
880 /* Be paranoid and try to detect possible races already now. */
881 kthread_insert_work_sanity_check(worker, work);
883 list_add(&work->node, &worker->delayed_work_list);
884 work->worker = worker;
885 timer->expires = jiffies + delay;
890 * kthread_queue_delayed_work - queue the associated kthread work
892 * @worker: target kthread_worker
893 * @dwork: kthread_delayed_work to queue
894 * @delay: number of jiffies to wait before queuing
896 * If the work has not been pending it starts a timer that will queue
897 * the work after the given @delay. If @delay is zero, it queues the
900 * Return: %false if the @work has already been pending. It means that
901 * either the timer was running or the work was queued. It returns %true
904 bool kthread_queue_delayed_work(struct kthread_worker *worker,
905 struct kthread_delayed_work *dwork,
908 struct kthread_work *work = &dwork->work;
912 spin_lock_irqsave(&worker->lock, flags);
914 if (!queuing_blocked(worker, work)) {
915 __kthread_queue_delayed_work(worker, dwork, delay);
919 spin_unlock_irqrestore(&worker->lock, flags);
922 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
924 struct kthread_flush_work {
925 struct kthread_work work;
926 struct completion done;
929 static void kthread_flush_work_fn(struct kthread_work *work)
931 struct kthread_flush_work *fwork =
932 container_of(work, struct kthread_flush_work, work);
933 complete(&fwork->done);
937 * kthread_flush_work - flush a kthread_work
938 * @work: work to flush
940 * If @work is queued or executing, wait for it to finish execution.
942 void kthread_flush_work(struct kthread_work *work)
944 struct kthread_flush_work fwork = {
945 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
946 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
948 struct kthread_worker *worker;
951 worker = work->worker;
955 spin_lock_irq(&worker->lock);
956 /* Work must not be used with >1 worker, see kthread_queue_work(). */
957 WARN_ON_ONCE(work->worker != worker);
959 if (!list_empty(&work->node))
960 kthread_insert_work(worker, &fwork.work, work->node.next);
961 else if (worker->current_work == work)
962 kthread_insert_work(worker, &fwork.work,
963 worker->work_list.next);
967 spin_unlock_irq(&worker->lock);
970 wait_for_completion(&fwork.done);
972 EXPORT_SYMBOL_GPL(kthread_flush_work);
975 * This function removes the work from the worker queue. Also it makes sure
976 * that it won't get queued later via the delayed work's timer.
978 * The work might still be in use when this function finishes. See the
979 * current_work proceed by the worker.
981 * Return: %true if @work was pending and successfully canceled,
982 * %false if @work was not pending
984 static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
985 unsigned long *flags)
987 /* Try to cancel the timer if exists. */
989 struct kthread_delayed_work *dwork =
990 container_of(work, struct kthread_delayed_work, work);
991 struct kthread_worker *worker = work->worker;
994 * del_timer_sync() must be called to make sure that the timer
995 * callback is not running. The lock must be temporary released
996 * to avoid a deadlock with the callback. In the meantime,
997 * any queuing is blocked by setting the canceling counter.
1000 spin_unlock_irqrestore(&worker->lock, *flags);
1001 del_timer_sync(&dwork->timer);
1002 spin_lock_irqsave(&worker->lock, *flags);
1007 * Try to remove the work from a worker list. It might either
1008 * be from worker->work_list or from worker->delayed_work_list.
1010 if (!list_empty(&work->node)) {
1011 list_del_init(&work->node);
1019 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1020 * @worker: kthread worker to use
1021 * @dwork: kthread delayed work to queue
1022 * @delay: number of jiffies to wait before queuing
1024 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1025 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1026 * @work is guaranteed to be queued immediately.
1028 * Return: %true if @dwork was pending and its timer was modified,
1031 * A special case is when the work is being canceled in parallel.
1032 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1033 * or yet another kthread_mod_delayed_work() call. We let the other command
1034 * win and return %false here. The caller is supposed to synchronize these
1035 * operations a reasonable way.
1037 * This function is safe to call from any context including IRQ handler.
1038 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1041 bool kthread_mod_delayed_work(struct kthread_worker *worker,
1042 struct kthread_delayed_work *dwork,
1043 unsigned long delay)
1045 struct kthread_work *work = &dwork->work;
1046 unsigned long flags;
1049 spin_lock_irqsave(&worker->lock, flags);
1051 /* Do not bother with canceling when never queued. */
1055 /* Work must not be used with >1 worker, see kthread_queue_work() */
1056 WARN_ON_ONCE(work->worker != worker);
1058 /* Do not fight with another command that is canceling this work. */
1059 if (work->canceling)
1062 ret = __kthread_cancel_work(work, true, &flags);
1064 __kthread_queue_delayed_work(worker, dwork, delay);
1066 spin_unlock_irqrestore(&worker->lock, flags);
1069 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1071 static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1073 struct kthread_worker *worker = work->worker;
1074 unsigned long flags;
1080 spin_lock_irqsave(&worker->lock, flags);
1081 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1082 WARN_ON_ONCE(work->worker != worker);
1084 ret = __kthread_cancel_work(work, is_dwork, &flags);
1086 if (worker->current_work != work)
1090 * The work is in progress and we need to wait with the lock released.
1091 * In the meantime, block any queuing by setting the canceling counter.
1094 spin_unlock_irqrestore(&worker->lock, flags);
1095 kthread_flush_work(work);
1096 spin_lock_irqsave(&worker->lock, flags);
1100 spin_unlock_irqrestore(&worker->lock, flags);
1106 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1107 * @work: the kthread work to cancel
1109 * Cancel @work and wait for its execution to finish. This function
1110 * can be used even if the work re-queues itself. On return from this
1111 * function, @work is guaranteed to be not pending or executing on any CPU.
1113 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1114 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1116 * The caller must ensure that the worker on which @work was last
1117 * queued can't be destroyed before this function returns.
1119 * Return: %true if @work was pending, %false otherwise.
1121 bool kthread_cancel_work_sync(struct kthread_work *work)
1123 return __kthread_cancel_work_sync(work, false);
1125 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1128 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1129 * wait for it to finish.
1130 * @dwork: the kthread delayed work to cancel
1132 * This is kthread_cancel_work_sync() for delayed works.
1134 * Return: %true if @dwork was pending, %false otherwise.
1136 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1138 return __kthread_cancel_work_sync(&dwork->work, true);
1140 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1143 * kthread_flush_worker - flush all current works on a kthread_worker
1144 * @worker: worker to flush
1146 * Wait until all currently executing or pending works on @worker are
1149 void kthread_flush_worker(struct kthread_worker *worker)
1151 struct kthread_flush_work fwork = {
1152 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1153 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1156 kthread_queue_work(worker, &fwork.work);
1157 wait_for_completion(&fwork.done);
1159 EXPORT_SYMBOL_GPL(kthread_flush_worker);
1162 * kthread_destroy_worker - destroy a kthread worker
1163 * @worker: worker to be destroyed
1165 * Flush and destroy @worker. The simple flush is enough because the kthread
1166 * worker API is used only in trivial scenarios. There are no multi-step state
1169 void kthread_destroy_worker(struct kthread_worker *worker)
1171 struct task_struct *task;
1173 task = worker->task;
1177 kthread_flush_worker(worker);
1179 WARN_ON(!list_empty(&worker->work_list));
1182 EXPORT_SYMBOL(kthread_destroy_worker);
1184 #ifdef CONFIG_BLK_CGROUP
1186 * kthread_associate_blkcg - associate blkcg to current kthread
1187 * @css: the cgroup info
1189 * Current thread must be a kthread. The thread is running jobs on behalf of
1190 * other threads. In some cases, we expect the jobs attach cgroup info of
1191 * original threads instead of that of current thread. This function stores
1192 * original thread's cgroup info in current kthread context for later
1195 void kthread_associate_blkcg(struct cgroup_subsys_state *css)
1197 struct kthread *kthread;
1199 if (!(current->flags & PF_KTHREAD))
1201 kthread = to_kthread(current);
1205 if (kthread->blkcg_css) {
1206 css_put(kthread->blkcg_css);
1207 kthread->blkcg_css = NULL;
1211 kthread->blkcg_css = css;
1214 EXPORT_SYMBOL(kthread_associate_blkcg);
1217 * kthread_blkcg - get associated blkcg css of current kthread
1219 * Current thread must be a kthread.
1221 struct cgroup_subsys_state *kthread_blkcg(void)
1223 struct kthread *kthread;
1225 if (current->flags & PF_KTHREAD) {
1226 kthread = to_kthread(current);
1228 return kthread->blkcg_css;
1232 EXPORT_SYMBOL(kthread_blkcg);