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/cgroup.h>
15 #include <linux/cpuset.h>
16 #include <linux/unistd.h>
17 #include <linux/file.h>
18 #include <linux/export.h>
19 #include <linux/mutex.h>
20 #include <linux/slab.h>
21 #include <linux/freezer.h>
22 #include <linux/ptrace.h>
23 #include <linux/uaccess.h>
24 #include <linux/numa.h>
25 #include <trace/events/sched.h>
27 static DEFINE_SPINLOCK(kthread_create_lock);
28 static LIST_HEAD(kthread_create_list);
29 struct task_struct *kthreadd_task;
31 struct kthread_create_info
33 /* Information passed to kthread() from kthreadd. */
34 int (*threadfn)(void *data);
38 /* Result passed back to kthread_create() from kthreadd. */
39 struct task_struct *result;
40 struct completion *done;
42 struct list_head list;
49 struct completion parked;
50 struct completion exited;
51 #ifdef CONFIG_BLK_CGROUP
52 struct cgroup_subsys_state *blkcg_css;
57 KTHREAD_IS_PER_CPU = 0,
62 static inline void set_kthread_struct(void *kthread)
65 * We abuse ->set_child_tid to avoid the new member and because it
66 * can't be wrongly copied by copy_process(). We also rely on fact
67 * that the caller can't exec, so PF_KTHREAD can't be cleared.
69 current->set_child_tid = (__force void __user *)kthread;
72 static inline struct kthread *to_kthread(struct task_struct *k)
74 WARN_ON(!(k->flags & PF_KTHREAD));
75 return (__force void *)k->set_child_tid;
78 void free_kthread_struct(struct task_struct *k)
80 struct kthread *kthread;
83 * Can be NULL if this kthread was created by kernel_thread()
84 * or if kmalloc() in kthread() failed.
86 kthread = to_kthread(k);
87 #ifdef CONFIG_BLK_CGROUP
88 WARN_ON_ONCE(kthread && kthread->blkcg_css);
94 * kthread_should_stop - should this kthread return now?
96 * When someone calls kthread_stop() on your kthread, it will be woken
97 * and this will return true. You should then return, and your return
98 * value will be passed through to kthread_stop().
100 bool kthread_should_stop(void)
102 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
104 EXPORT_SYMBOL(kthread_should_stop);
106 bool __kthread_should_park(struct task_struct *k)
108 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(k)->flags);
110 EXPORT_SYMBOL_GPL(__kthread_should_park);
113 * kthread_should_park - should this kthread park now?
115 * When someone calls kthread_park() on your kthread, it will be woken
116 * and this will return true. You should then do the necessary
117 * cleanup and call kthread_parkme()
119 * Similar to kthread_should_stop(), but this keeps the thread alive
120 * and in a park position. kthread_unpark() "restarts" the thread and
121 * calls the thread function again.
123 bool kthread_should_park(void)
125 return __kthread_should_park(current);
127 EXPORT_SYMBOL_GPL(kthread_should_park);
130 * kthread_freezable_should_stop - should this freezable kthread return now?
131 * @was_frozen: optional out parameter, indicates whether %current was frozen
133 * kthread_should_stop() for freezable kthreads, which will enter
134 * refrigerator if necessary. This function is safe from kthread_stop() /
135 * freezer deadlock and freezable kthreads should use this function instead
136 * of calling try_to_freeze() directly.
138 bool kthread_freezable_should_stop(bool *was_frozen)
144 if (unlikely(freezing(current)))
145 frozen = __refrigerator(true);
148 *was_frozen = frozen;
150 return kthread_should_stop();
152 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
155 * kthread_data - return data value specified on kthread creation
156 * @task: kthread task in question
158 * Return the data value specified when kthread @task was created.
159 * The caller is responsible for ensuring the validity of @task when
160 * calling this function.
162 void *kthread_data(struct task_struct *task)
164 return to_kthread(task)->data;
168 * kthread_probe_data - speculative version of kthread_data()
169 * @task: possible kthread task in question
171 * @task could be a kthread task. Return the data value specified when it
172 * was created if accessible. If @task isn't a kthread task or its data is
173 * inaccessible for any reason, %NULL is returned. This function requires
174 * that @task itself is safe to dereference.
176 void *kthread_probe_data(struct task_struct *task)
178 struct kthread *kthread = to_kthread(task);
181 probe_kernel_read(&data, &kthread->data, sizeof(data));
185 static void __kthread_parkme(struct kthread *self)
189 * TASK_PARKED is a special state; we must serialize against
190 * possible pending wakeups to avoid store-store collisions on
193 * Such a collision might possibly result in the task state
194 * changin from TASK_PARKED and us failing the
195 * wait_task_inactive() in kthread_park().
197 set_special_state(TASK_PARKED);
198 if (!test_bit(KTHREAD_SHOULD_PARK, &self->flags))
201 complete(&self->parked);
204 __set_current_state(TASK_RUNNING);
207 void kthread_parkme(void)
209 __kthread_parkme(to_kthread(current));
211 EXPORT_SYMBOL_GPL(kthread_parkme);
213 static int kthread(void *_create)
215 /* Copy data: it's on kthread's stack */
216 struct kthread_create_info *create = _create;
217 int (*threadfn)(void *data) = create->threadfn;
218 void *data = create->data;
219 struct completion *done;
220 struct kthread *self;
223 self = kzalloc(sizeof(*self), GFP_KERNEL);
224 set_kthread_struct(self);
226 /* If user was SIGKILLed, I release the structure. */
227 done = xchg(&create->done, NULL);
234 create->result = ERR_PTR(-ENOMEM);
240 init_completion(&self->exited);
241 init_completion(&self->parked);
242 current->vfork_done = &self->exited;
244 /* OK, tell user we're spawned, wait for stop or wakeup */
245 __set_current_state(TASK_UNINTERRUPTIBLE);
246 create->result = current;
251 if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
252 cgroup_kthread_ready();
253 __kthread_parkme(self);
254 ret = threadfn(data);
259 /* called from do_fork() to get node information for about to be created task */
260 int tsk_fork_get_node(struct task_struct *tsk)
263 if (tsk == kthreadd_task)
264 return tsk->pref_node_fork;
269 static void create_kthread(struct kthread_create_info *create)
274 current->pref_node_fork = create->node;
276 /* We want our own signal handler (we take no signals by default). */
277 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
279 /* If user was SIGKILLed, I release the structure. */
280 struct completion *done = xchg(&create->done, NULL);
286 create->result = ERR_PTR(pid);
291 static __printf(4, 0)
292 struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
293 void *data, int node,
294 const char namefmt[],
297 DECLARE_COMPLETION_ONSTACK(done);
298 struct task_struct *task;
299 struct kthread_create_info *create = kmalloc(sizeof(*create),
303 return ERR_PTR(-ENOMEM);
304 create->threadfn = threadfn;
307 create->done = &done;
309 spin_lock(&kthread_create_lock);
310 list_add_tail(&create->list, &kthread_create_list);
311 spin_unlock(&kthread_create_lock);
313 wake_up_process(kthreadd_task);
315 * Wait for completion in killable state, for I might be chosen by
316 * the OOM killer while kthreadd is trying to allocate memory for
319 if (unlikely(wait_for_completion_killable(&done))) {
321 * If I was SIGKILLed before kthreadd (or new kernel thread)
322 * calls complete(), leave the cleanup of this structure to
325 if (xchg(&create->done, NULL))
326 return ERR_PTR(-EINTR);
328 * kthreadd (or new kernel thread) will call complete()
331 wait_for_completion(&done);
333 task = create->result;
335 static const struct sched_param param = { .sched_priority = 0 };
336 char name[TASK_COMM_LEN];
339 * task is already visible to other tasks, so updating
340 * COMM must be protected.
342 vsnprintf(name, sizeof(name), namefmt, args);
343 set_task_comm(task, name);
345 * root may have changed our (kthreadd's) priority or CPU mask.
346 * The kernel thread should not inherit these properties.
348 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
349 set_cpus_allowed_ptr(task, cpu_all_mask);
356 * kthread_create_on_node - create a kthread.
357 * @threadfn: the function to run until signal_pending(current).
358 * @data: data ptr for @threadfn.
359 * @node: task and thread structures for the thread are allocated on this node
360 * @namefmt: printf-style name for the thread.
362 * Description: This helper function creates and names a kernel
363 * thread. The thread will be stopped: use wake_up_process() to start
364 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
365 * is affine to all CPUs.
367 * If thread is going to be bound on a particular cpu, give its node
368 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
369 * When woken, the thread will run @threadfn() with @data as its
370 * argument. @threadfn() can either call do_exit() directly if it is a
371 * standalone thread for which no one will call kthread_stop(), or
372 * return when 'kthread_should_stop()' is true (which means
373 * kthread_stop() has been called). The return value should be zero
374 * or a negative error number; it will be passed to kthread_stop().
376 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
378 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
379 void *data, int node,
380 const char namefmt[],
383 struct task_struct *task;
386 va_start(args, namefmt);
387 task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
392 EXPORT_SYMBOL(kthread_create_on_node);
394 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
398 if (!wait_task_inactive(p, state)) {
403 /* It's safe because the task is inactive. */
404 raw_spin_lock_irqsave(&p->pi_lock, flags);
405 do_set_cpus_allowed(p, mask);
406 p->flags |= PF_NO_SETAFFINITY;
407 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
410 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
412 __kthread_bind_mask(p, cpumask_of(cpu), state);
415 void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
417 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
421 * kthread_bind - bind a just-created kthread to a cpu.
422 * @p: thread created by kthread_create().
423 * @cpu: cpu (might not be online, must be possible) for @k to run on.
425 * Description: This function is equivalent to set_cpus_allowed(),
426 * except that @cpu doesn't need to be online, and the thread must be
427 * stopped (i.e., just returned from kthread_create()).
429 void kthread_bind(struct task_struct *p, unsigned int cpu)
431 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
433 EXPORT_SYMBOL(kthread_bind);
436 * kthread_create_on_cpu - Create a cpu bound kthread
437 * @threadfn: the function to run until signal_pending(current).
438 * @data: data ptr for @threadfn.
439 * @cpu: The cpu on which the thread should be bound,
440 * @namefmt: printf-style name for the thread. Format is restricted
441 * to "name.*%u". Code fills in cpu number.
443 * Description: This helper function creates and names a kernel thread
444 * The thread will be woken and put into park mode.
446 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
447 void *data, unsigned int cpu,
450 struct task_struct *p;
452 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
456 kthread_bind(p, cpu);
457 /* CPU hotplug need to bind once again when unparking the thread. */
458 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
459 to_kthread(p)->cpu = cpu;
464 * kthread_unpark - unpark a thread created by kthread_create().
465 * @k: thread created by kthread_create().
467 * Sets kthread_should_park() for @k to return false, wakes it, and
468 * waits for it to return. If the thread is marked percpu then its
469 * bound to the cpu again.
471 void kthread_unpark(struct task_struct *k)
473 struct kthread *kthread = to_kthread(k);
476 * Newly created kthread was parked when the CPU was offline.
477 * The binding was lost and we need to set it again.
479 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
480 __kthread_bind(k, kthread->cpu, TASK_PARKED);
482 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
484 * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup.
486 wake_up_state(k, TASK_PARKED);
488 EXPORT_SYMBOL_GPL(kthread_unpark);
491 * kthread_park - park a thread created by kthread_create().
492 * @k: thread created by kthread_create().
494 * Sets kthread_should_park() for @k to return true, wakes it, and
495 * waits for it to return. This can also be called after kthread_create()
496 * instead of calling wake_up_process(): the thread will park without
497 * calling threadfn().
499 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
500 * If called by the kthread itself just the park bit is set.
502 int kthread_park(struct task_struct *k)
504 struct kthread *kthread = to_kthread(k);
506 if (WARN_ON(k->flags & PF_EXITING))
509 if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK, &kthread->flags)))
512 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
516 * Wait for __kthread_parkme() to complete(), this means we
517 * _will_ have TASK_PARKED and are about to call schedule().
519 wait_for_completion(&kthread->parked);
521 * Now wait for that schedule() to complete and the task to
524 WARN_ON_ONCE(!wait_task_inactive(k, TASK_PARKED));
529 EXPORT_SYMBOL_GPL(kthread_park);
532 * kthread_stop - stop a thread created by kthread_create().
533 * @k: thread created by kthread_create().
535 * Sets kthread_should_stop() for @k to return true, wakes it, and
536 * waits for it to exit. This can also be called after kthread_create()
537 * instead of calling wake_up_process(): the thread will exit without
538 * calling threadfn().
540 * If threadfn() may call do_exit() itself, the caller must ensure
541 * task_struct can't go away.
543 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
546 int kthread_stop(struct task_struct *k)
548 struct kthread *kthread;
551 trace_sched_kthread_stop(k);
554 kthread = to_kthread(k);
555 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
558 wait_for_completion(&kthread->exited);
562 trace_sched_kthread_stop_ret(ret);
565 EXPORT_SYMBOL(kthread_stop);
567 int kthreadd(void *unused)
569 struct task_struct *tsk = current;
571 /* Setup a clean context for our children to inherit. */
572 set_task_comm(tsk, "kthreadd");
574 set_cpus_allowed_ptr(tsk, cpu_all_mask);
575 set_mems_allowed(node_states[N_MEMORY]);
577 current->flags |= PF_NOFREEZE;
578 cgroup_init_kthreadd();
581 set_current_state(TASK_INTERRUPTIBLE);
582 if (list_empty(&kthread_create_list))
584 __set_current_state(TASK_RUNNING);
586 spin_lock(&kthread_create_lock);
587 while (!list_empty(&kthread_create_list)) {
588 struct kthread_create_info *create;
590 create = list_entry(kthread_create_list.next,
591 struct kthread_create_info, list);
592 list_del_init(&create->list);
593 spin_unlock(&kthread_create_lock);
595 create_kthread(create);
597 spin_lock(&kthread_create_lock);
599 spin_unlock(&kthread_create_lock);
605 void __kthread_init_worker(struct kthread_worker *worker,
607 struct lock_class_key *key)
609 memset(worker, 0, sizeof(struct kthread_worker));
610 raw_spin_lock_init(&worker->lock);
611 lockdep_set_class_and_name(&worker->lock, key, name);
612 INIT_LIST_HEAD(&worker->work_list);
613 INIT_LIST_HEAD(&worker->delayed_work_list);
615 EXPORT_SYMBOL_GPL(__kthread_init_worker);
618 * kthread_worker_fn - kthread function to process kthread_worker
619 * @worker_ptr: pointer to initialized kthread_worker
621 * This function implements the main cycle of kthread worker. It processes
622 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
625 * The works are not allowed to keep any locks, disable preemption or interrupts
626 * when they finish. There is defined a safe point for freezing when one work
627 * finishes and before a new one is started.
629 * Also the works must not be handled by more than one worker at the same time,
630 * see also kthread_queue_work().
632 int kthread_worker_fn(void *worker_ptr)
634 struct kthread_worker *worker = worker_ptr;
635 struct kthread_work *work;
638 * FIXME: Update the check and remove the assignment when all kthread
639 * worker users are created using kthread_create_worker*() functions.
641 WARN_ON(worker->task && worker->task != current);
642 worker->task = current;
644 if (worker->flags & KTW_FREEZABLE)
648 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
650 if (kthread_should_stop()) {
651 __set_current_state(TASK_RUNNING);
652 raw_spin_lock_irq(&worker->lock);
654 raw_spin_unlock_irq(&worker->lock);
659 raw_spin_lock_irq(&worker->lock);
660 if (!list_empty(&worker->work_list)) {
661 work = list_first_entry(&worker->work_list,
662 struct kthread_work, node);
663 list_del_init(&work->node);
665 worker->current_work = work;
666 raw_spin_unlock_irq(&worker->lock);
669 __set_current_state(TASK_RUNNING);
671 } else if (!freezing(current))
678 EXPORT_SYMBOL_GPL(kthread_worker_fn);
680 static __printf(3, 0) struct kthread_worker *
681 __kthread_create_worker(int cpu, unsigned int flags,
682 const char namefmt[], va_list args)
684 struct kthread_worker *worker;
685 struct task_struct *task;
686 int node = NUMA_NO_NODE;
688 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
690 return ERR_PTR(-ENOMEM);
692 kthread_init_worker(worker);
695 node = cpu_to_node(cpu);
697 task = __kthread_create_on_node(kthread_worker_fn, worker,
698 node, namefmt, args);
703 kthread_bind(task, cpu);
705 worker->flags = flags;
707 wake_up_process(task);
712 return ERR_CAST(task);
716 * kthread_create_worker - create a kthread worker
717 * @flags: flags modifying the default behavior of the worker
718 * @namefmt: printf-style name for the kthread worker (task).
720 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
721 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
722 * when the worker was SIGKILLed.
724 struct kthread_worker *
725 kthread_create_worker(unsigned int flags, const char namefmt[], ...)
727 struct kthread_worker *worker;
730 va_start(args, namefmt);
731 worker = __kthread_create_worker(-1, flags, namefmt, args);
736 EXPORT_SYMBOL(kthread_create_worker);
739 * kthread_create_worker_on_cpu - create a kthread worker and bind it
740 * it to a given CPU and the associated NUMA node.
742 * @flags: flags modifying the default behavior of the worker
743 * @namefmt: printf-style name for the kthread worker (task).
745 * Use a valid CPU number if you want to bind the kthread worker
746 * to the given CPU and the associated NUMA node.
748 * A good practice is to add the cpu number also into the worker name.
749 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
751 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
752 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
753 * when the worker was SIGKILLed.
755 struct kthread_worker *
756 kthread_create_worker_on_cpu(int cpu, unsigned int flags,
757 const char namefmt[], ...)
759 struct kthread_worker *worker;
762 va_start(args, namefmt);
763 worker = __kthread_create_worker(cpu, flags, namefmt, args);
768 EXPORT_SYMBOL(kthread_create_worker_on_cpu);
771 * Returns true when the work could not be queued at the moment.
772 * It happens when it is already pending in a worker list
773 * or when it is being cancelled.
775 static inline bool queuing_blocked(struct kthread_worker *worker,
776 struct kthread_work *work)
778 lockdep_assert_held(&worker->lock);
780 return !list_empty(&work->node) || work->canceling;
783 static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
784 struct kthread_work *work)
786 lockdep_assert_held(&worker->lock);
787 WARN_ON_ONCE(!list_empty(&work->node));
788 /* Do not use a work with >1 worker, see kthread_queue_work() */
789 WARN_ON_ONCE(work->worker && work->worker != worker);
792 /* insert @work before @pos in @worker */
793 static void kthread_insert_work(struct kthread_worker *worker,
794 struct kthread_work *work,
795 struct list_head *pos)
797 kthread_insert_work_sanity_check(worker, work);
799 list_add_tail(&work->node, pos);
800 work->worker = worker;
801 if (!worker->current_work && likely(worker->task))
802 wake_up_process(worker->task);
806 * kthread_queue_work - queue a kthread_work
807 * @worker: target kthread_worker
808 * @work: kthread_work to queue
810 * Queue @work to work processor @task for async execution. @task
811 * must have been created with kthread_worker_create(). Returns %true
812 * if @work was successfully queued, %false if it was already pending.
814 * Reinitialize the work if it needs to be used by another worker.
815 * For example, when the worker was stopped and started again.
817 bool kthread_queue_work(struct kthread_worker *worker,
818 struct kthread_work *work)
823 raw_spin_lock_irqsave(&worker->lock, flags);
824 if (!queuing_blocked(worker, work)) {
825 kthread_insert_work(worker, work, &worker->work_list);
828 raw_spin_unlock_irqrestore(&worker->lock, flags);
831 EXPORT_SYMBOL_GPL(kthread_queue_work);
834 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
835 * delayed work when the timer expires.
836 * @t: pointer to the expired timer
838 * The format of the function is defined by struct timer_list.
839 * It should have been called from irqsafe timer with irq already off.
841 void kthread_delayed_work_timer_fn(struct timer_list *t)
843 struct kthread_delayed_work *dwork = from_timer(dwork, t, timer);
844 struct kthread_work *work = &dwork->work;
845 struct kthread_worker *worker = work->worker;
849 * This might happen when a pending work is reinitialized.
850 * It means that it is used a wrong way.
852 if (WARN_ON_ONCE(!worker))
855 raw_spin_lock_irqsave(&worker->lock, flags);
856 /* Work must not be used with >1 worker, see kthread_queue_work(). */
857 WARN_ON_ONCE(work->worker != worker);
859 /* Move the work from worker->delayed_work_list. */
860 WARN_ON_ONCE(list_empty(&work->node));
861 list_del_init(&work->node);
862 kthread_insert_work(worker, work, &worker->work_list);
864 raw_spin_unlock_irqrestore(&worker->lock, flags);
866 EXPORT_SYMBOL(kthread_delayed_work_timer_fn);
868 void __kthread_queue_delayed_work(struct kthread_worker *worker,
869 struct kthread_delayed_work *dwork,
872 struct timer_list *timer = &dwork->timer;
873 struct kthread_work *work = &dwork->work;
875 WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);
878 * If @delay is 0, queue @dwork->work immediately. This is for
879 * both optimization and correctness. The earliest @timer can
880 * expire is on the closest next tick and delayed_work users depend
881 * on that there's no such delay when @delay is 0.
884 kthread_insert_work(worker, work, &worker->work_list);
888 /* Be paranoid and try to detect possible races already now. */
889 kthread_insert_work_sanity_check(worker, work);
891 list_add(&work->node, &worker->delayed_work_list);
892 work->worker = worker;
893 timer->expires = jiffies + delay;
898 * kthread_queue_delayed_work - queue the associated kthread work
900 * @worker: target kthread_worker
901 * @dwork: kthread_delayed_work to queue
902 * @delay: number of jiffies to wait before queuing
904 * If the work has not been pending it starts a timer that will queue
905 * the work after the given @delay. If @delay is zero, it queues the
908 * Return: %false if the @work has already been pending. It means that
909 * either the timer was running or the work was queued. It returns %true
912 bool kthread_queue_delayed_work(struct kthread_worker *worker,
913 struct kthread_delayed_work *dwork,
916 struct kthread_work *work = &dwork->work;
920 raw_spin_lock_irqsave(&worker->lock, flags);
922 if (!queuing_blocked(worker, work)) {
923 __kthread_queue_delayed_work(worker, dwork, delay);
927 raw_spin_unlock_irqrestore(&worker->lock, flags);
930 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
932 struct kthread_flush_work {
933 struct kthread_work work;
934 struct completion done;
937 static void kthread_flush_work_fn(struct kthread_work *work)
939 struct kthread_flush_work *fwork =
940 container_of(work, struct kthread_flush_work, work);
941 complete(&fwork->done);
945 * kthread_flush_work - flush a kthread_work
946 * @work: work to flush
948 * If @work is queued or executing, wait for it to finish execution.
950 void kthread_flush_work(struct kthread_work *work)
952 struct kthread_flush_work fwork = {
953 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
954 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
956 struct kthread_worker *worker;
959 worker = work->worker;
963 raw_spin_lock_irq(&worker->lock);
964 /* Work must not be used with >1 worker, see kthread_queue_work(). */
965 WARN_ON_ONCE(work->worker != worker);
967 if (!list_empty(&work->node))
968 kthread_insert_work(worker, &fwork.work, work->node.next);
969 else if (worker->current_work == work)
970 kthread_insert_work(worker, &fwork.work,
971 worker->work_list.next);
975 raw_spin_unlock_irq(&worker->lock);
978 wait_for_completion(&fwork.done);
980 EXPORT_SYMBOL_GPL(kthread_flush_work);
983 * This function removes the work from the worker queue. Also it makes sure
984 * that it won't get queued later via the delayed work's timer.
986 * The work might still be in use when this function finishes. See the
987 * current_work proceed by the worker.
989 * Return: %true if @work was pending and successfully canceled,
990 * %false if @work was not pending
992 static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
993 unsigned long *flags)
995 /* Try to cancel the timer if exists. */
997 struct kthread_delayed_work *dwork =
998 container_of(work, struct kthread_delayed_work, work);
999 struct kthread_worker *worker = work->worker;
1002 * del_timer_sync() must be called to make sure that the timer
1003 * callback is not running. The lock must be temporary released
1004 * to avoid a deadlock with the callback. In the meantime,
1005 * any queuing is blocked by setting the canceling counter.
1008 raw_spin_unlock_irqrestore(&worker->lock, *flags);
1009 del_timer_sync(&dwork->timer);
1010 raw_spin_lock_irqsave(&worker->lock, *flags);
1015 * Try to remove the work from a worker list. It might either
1016 * be from worker->work_list or from worker->delayed_work_list.
1018 if (!list_empty(&work->node)) {
1019 list_del_init(&work->node);
1027 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1028 * @worker: kthread worker to use
1029 * @dwork: kthread delayed work to queue
1030 * @delay: number of jiffies to wait before queuing
1032 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1033 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1034 * @work is guaranteed to be queued immediately.
1036 * Return: %true if @dwork was pending and its timer was modified,
1039 * A special case is when the work is being canceled in parallel.
1040 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1041 * or yet another kthread_mod_delayed_work() call. We let the other command
1042 * win and return %false here. The caller is supposed to synchronize these
1043 * operations a reasonable way.
1045 * This function is safe to call from any context including IRQ handler.
1046 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1049 bool kthread_mod_delayed_work(struct kthread_worker *worker,
1050 struct kthread_delayed_work *dwork,
1051 unsigned long delay)
1053 struct kthread_work *work = &dwork->work;
1054 unsigned long flags;
1057 raw_spin_lock_irqsave(&worker->lock, flags);
1059 /* Do not bother with canceling when never queued. */
1063 /* Work must not be used with >1 worker, see kthread_queue_work() */
1064 WARN_ON_ONCE(work->worker != worker);
1066 /* Do not fight with another command that is canceling this work. */
1067 if (work->canceling)
1070 ret = __kthread_cancel_work(work, true, &flags);
1072 __kthread_queue_delayed_work(worker, dwork, delay);
1074 raw_spin_unlock_irqrestore(&worker->lock, flags);
1077 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1079 static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1081 struct kthread_worker *worker = work->worker;
1082 unsigned long flags;
1088 raw_spin_lock_irqsave(&worker->lock, flags);
1089 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1090 WARN_ON_ONCE(work->worker != worker);
1092 ret = __kthread_cancel_work(work, is_dwork, &flags);
1094 if (worker->current_work != work)
1098 * The work is in progress and we need to wait with the lock released.
1099 * In the meantime, block any queuing by setting the canceling counter.
1102 raw_spin_unlock_irqrestore(&worker->lock, flags);
1103 kthread_flush_work(work);
1104 raw_spin_lock_irqsave(&worker->lock, flags);
1108 raw_spin_unlock_irqrestore(&worker->lock, flags);
1114 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1115 * @work: the kthread work to cancel
1117 * Cancel @work and wait for its execution to finish. This function
1118 * can be used even if the work re-queues itself. On return from this
1119 * function, @work is guaranteed to be not pending or executing on any CPU.
1121 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1122 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1124 * The caller must ensure that the worker on which @work was last
1125 * queued can't be destroyed before this function returns.
1127 * Return: %true if @work was pending, %false otherwise.
1129 bool kthread_cancel_work_sync(struct kthread_work *work)
1131 return __kthread_cancel_work_sync(work, false);
1133 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1136 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1137 * wait for it to finish.
1138 * @dwork: the kthread delayed work to cancel
1140 * This is kthread_cancel_work_sync() for delayed works.
1142 * Return: %true if @dwork was pending, %false otherwise.
1144 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1146 return __kthread_cancel_work_sync(&dwork->work, true);
1148 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1151 * kthread_flush_worker - flush all current works on a kthread_worker
1152 * @worker: worker to flush
1154 * Wait until all currently executing or pending works on @worker are
1157 void kthread_flush_worker(struct kthread_worker *worker)
1159 struct kthread_flush_work fwork = {
1160 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1161 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1164 kthread_queue_work(worker, &fwork.work);
1165 wait_for_completion(&fwork.done);
1167 EXPORT_SYMBOL_GPL(kthread_flush_worker);
1170 * kthread_destroy_worker - destroy a kthread worker
1171 * @worker: worker to be destroyed
1173 * Flush and destroy @worker. The simple flush is enough because the kthread
1174 * worker API is used only in trivial scenarios. There are no multi-step state
1177 void kthread_destroy_worker(struct kthread_worker *worker)
1179 struct task_struct *task;
1181 task = worker->task;
1185 kthread_flush_worker(worker);
1187 WARN_ON(!list_empty(&worker->work_list));
1190 EXPORT_SYMBOL(kthread_destroy_worker);
1192 #ifdef CONFIG_BLK_CGROUP
1194 * kthread_associate_blkcg - associate blkcg to current kthread
1195 * @css: the cgroup info
1197 * Current thread must be a kthread. The thread is running jobs on behalf of
1198 * other threads. In some cases, we expect the jobs attach cgroup info of
1199 * original threads instead of that of current thread. This function stores
1200 * original thread's cgroup info in current kthread context for later
1203 void kthread_associate_blkcg(struct cgroup_subsys_state *css)
1205 struct kthread *kthread;
1207 if (!(current->flags & PF_KTHREAD))
1209 kthread = to_kthread(current);
1213 if (kthread->blkcg_css) {
1214 css_put(kthread->blkcg_css);
1215 kthread->blkcg_css = NULL;
1219 kthread->blkcg_css = css;
1222 EXPORT_SYMBOL(kthread_associate_blkcg);
1225 * kthread_blkcg - get associated blkcg css of current kthread
1227 * Current thread must be a kthread.
1229 struct cgroup_subsys_state *kthread_blkcg(void)
1231 struct kthread *kthread;
1233 if (current->flags & PF_KTHREAD) {
1234 kthread = to_kthread(current);
1236 return kthread->blkcg_css;
1240 EXPORT_SYMBOL(kthread_blkcg);