1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Kernel thread helper functions.
3 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
5 * Creation is done via kthreadd, so that we get a clean environment
6 * even if we're invoked from userspace (think modprobe, hotplug cpu,
9 #include <uapi/linux/sched/types.h>
10 #include <linux/sched.h>
11 #include <linux/sched/task.h>
12 #include <linux/kthread.h>
13 #include <linux/completion.h>
14 #include <linux/err.h>
15 #include <linux/cgroup.h>
16 #include <linux/cpuset.h>
17 #include <linux/unistd.h>
18 #include <linux/file.h>
19 #include <linux/export.h>
20 #include <linux/mutex.h>
21 #include <linux/slab.h>
22 #include <linux/freezer.h>
23 #include <linux/ptrace.h>
24 #include <linux/uaccess.h>
25 #include <linux/numa.h>
26 #include <trace/events/sched.h>
28 static DEFINE_SPINLOCK(kthread_create_lock);
29 static LIST_HEAD(kthread_create_list);
30 struct task_struct *kthreadd_task;
32 struct kthread_create_info
34 /* Information passed to kthread() from kthreadd. */
35 int (*threadfn)(void *data);
39 /* Result passed back to kthread_create() from kthreadd. */
40 struct task_struct *result;
41 struct completion *done;
43 struct list_head list;
50 struct completion parked;
51 struct completion exited;
52 #ifdef CONFIG_BLK_CGROUP
53 struct cgroup_subsys_state *blkcg_css;
58 KTHREAD_IS_PER_CPU = 0,
63 static inline void set_kthread_struct(void *kthread)
66 * We abuse ->set_child_tid to avoid the new member and because it
67 * can't be wrongly copied by copy_process(). We also rely on fact
68 * that the caller can't exec, so PF_KTHREAD can't be cleared.
70 current->set_child_tid = (__force void __user *)kthread;
73 static inline struct kthread *to_kthread(struct task_struct *k)
75 WARN_ON(!(k->flags & PF_KTHREAD));
76 return (__force void *)k->set_child_tid;
79 void free_kthread_struct(struct task_struct *k)
81 struct kthread *kthread;
84 * Can be NULL if this kthread was created by kernel_thread()
85 * or if kmalloc() in kthread() failed.
87 kthread = to_kthread(k);
88 #ifdef CONFIG_BLK_CGROUP
89 WARN_ON_ONCE(kthread && kthread->blkcg_css);
95 * kthread_should_stop - should this kthread return now?
97 * When someone calls kthread_stop() on your kthread, it will be woken
98 * and this will return true. You should then return, and your return
99 * value will be passed through to kthread_stop().
101 bool kthread_should_stop(void)
103 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
105 EXPORT_SYMBOL(kthread_should_stop);
107 bool __kthread_should_park(struct task_struct *k)
109 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(k)->flags);
111 EXPORT_SYMBOL_GPL(__kthread_should_park);
114 * kthread_should_park - should this kthread park now?
116 * When someone calls kthread_park() on your kthread, it will be woken
117 * and this will return true. You should then do the necessary
118 * cleanup and call kthread_parkme()
120 * Similar to kthread_should_stop(), but this keeps the thread alive
121 * and in a park position. kthread_unpark() "restarts" the thread and
122 * calls the thread function again.
124 bool kthread_should_park(void)
126 return __kthread_should_park(current);
128 EXPORT_SYMBOL_GPL(kthread_should_park);
131 * kthread_freezable_should_stop - should this freezable kthread return now?
132 * @was_frozen: optional out parameter, indicates whether %current was frozen
134 * kthread_should_stop() for freezable kthreads, which will enter
135 * refrigerator if necessary. This function is safe from kthread_stop() /
136 * freezer deadlock and freezable kthreads should use this function instead
137 * of calling try_to_freeze() directly.
139 bool kthread_freezable_should_stop(bool *was_frozen)
145 if (unlikely(freezing(current)))
146 frozen = __refrigerator(true);
149 *was_frozen = frozen;
151 return kthread_should_stop();
153 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
156 * kthread_data - return data value specified on kthread creation
157 * @task: kthread task in question
159 * Return the data value specified when kthread @task was created.
160 * The caller is responsible for ensuring the validity of @task when
161 * calling this function.
163 void *kthread_data(struct task_struct *task)
165 return to_kthread(task)->data;
169 * kthread_probe_data - speculative version of kthread_data()
170 * @task: possible kthread task in question
172 * @task could be a kthread task. Return the data value specified when it
173 * was created if accessible. If @task isn't a kthread task or its data is
174 * inaccessible for any reason, %NULL is returned. This function requires
175 * that @task itself is safe to dereference.
177 void *kthread_probe_data(struct task_struct *task)
179 struct kthread *kthread = to_kthread(task);
182 probe_kernel_read(&data, &kthread->data, sizeof(data));
186 static void __kthread_parkme(struct kthread *self)
190 * TASK_PARKED is a special state; we must serialize against
191 * possible pending wakeups to avoid store-store collisions on
194 * Such a collision might possibly result in the task state
195 * changin from TASK_PARKED and us failing the
196 * wait_task_inactive() in kthread_park().
198 set_special_state(TASK_PARKED);
199 if (!test_bit(KTHREAD_SHOULD_PARK, &self->flags))
202 complete(&self->parked);
205 __set_current_state(TASK_RUNNING);
208 void kthread_parkme(void)
210 __kthread_parkme(to_kthread(current));
212 EXPORT_SYMBOL_GPL(kthread_parkme);
214 static int kthread(void *_create)
216 /* Copy data: it's on kthread's stack */
217 struct kthread_create_info *create = _create;
218 int (*threadfn)(void *data) = create->threadfn;
219 void *data = create->data;
220 struct completion *done;
221 struct kthread *self;
224 self = kzalloc(sizeof(*self), GFP_KERNEL);
225 set_kthread_struct(self);
227 /* If user was SIGKILLed, I release the structure. */
228 done = xchg(&create->done, NULL);
235 create->result = ERR_PTR(-ENOMEM);
241 init_completion(&self->exited);
242 init_completion(&self->parked);
243 current->vfork_done = &self->exited;
245 /* OK, tell user we're spawned, wait for stop or wakeup */
246 __set_current_state(TASK_UNINTERRUPTIBLE);
247 create->result = current;
252 if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
253 cgroup_kthread_ready();
254 __kthread_parkme(self);
255 ret = threadfn(data);
260 /* called from do_fork() to get node information for about to be created task */
261 int tsk_fork_get_node(struct task_struct *tsk)
264 if (tsk == kthreadd_task)
265 return tsk->pref_node_fork;
270 static void create_kthread(struct kthread_create_info *create)
275 current->pref_node_fork = create->node;
277 /* We want our own signal handler (we take no signals by default). */
278 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
280 /* If user was SIGKILLed, I release the structure. */
281 struct completion *done = xchg(&create->done, NULL);
287 create->result = ERR_PTR(pid);
292 static __printf(4, 0)
293 struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
294 void *data, int node,
295 const char namefmt[],
298 DECLARE_COMPLETION_ONSTACK(done);
299 struct task_struct *task;
300 struct kthread_create_info *create = kmalloc(sizeof(*create),
304 return ERR_PTR(-ENOMEM);
305 create->threadfn = threadfn;
308 create->done = &done;
310 spin_lock(&kthread_create_lock);
311 list_add_tail(&create->list, &kthread_create_list);
312 spin_unlock(&kthread_create_lock);
314 wake_up_process(kthreadd_task);
316 * Wait for completion in killable state, for I might be chosen by
317 * the OOM killer while kthreadd is trying to allocate memory for
320 if (unlikely(wait_for_completion_killable(&done))) {
322 * If I was SIGKILLed before kthreadd (or new kernel thread)
323 * calls complete(), leave the cleanup of this structure to
326 if (xchg(&create->done, NULL))
327 return ERR_PTR(-EINTR);
329 * kthreadd (or new kernel thread) will call complete()
332 wait_for_completion(&done);
334 task = create->result;
336 static const struct sched_param param = { .sched_priority = 0 };
337 char name[TASK_COMM_LEN];
340 * task is already visible to other tasks, so updating
341 * COMM must be protected.
343 vsnprintf(name, sizeof(name), namefmt, args);
344 set_task_comm(task, name);
346 * root may have changed our (kthreadd's) priority or CPU mask.
347 * The kernel thread should not inherit these properties.
349 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
350 set_cpus_allowed_ptr(task, cpu_all_mask);
357 * kthread_create_on_node - create a kthread.
358 * @threadfn: the function to run until signal_pending(current).
359 * @data: data ptr for @threadfn.
360 * @node: task and thread structures for the thread are allocated on this node
361 * @namefmt: printf-style name for the thread.
363 * Description: This helper function creates and names a kernel
364 * thread. The thread will be stopped: use wake_up_process() to start
365 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
366 * is affine to all CPUs.
368 * If thread is going to be bound on a particular cpu, give its node
369 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
370 * When woken, the thread will run @threadfn() with @data as its
371 * argument. @threadfn() can either call do_exit() directly if it is a
372 * standalone thread for which no one will call kthread_stop(), or
373 * return when 'kthread_should_stop()' is true (which means
374 * kthread_stop() has been called). The return value should be zero
375 * or a negative error number; it will be passed to kthread_stop().
377 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
379 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
380 void *data, int node,
381 const char namefmt[],
384 struct task_struct *task;
387 va_start(args, namefmt);
388 task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
393 EXPORT_SYMBOL(kthread_create_on_node);
395 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
399 if (!wait_task_inactive(p, state)) {
404 /* It's safe because the task is inactive. */
405 raw_spin_lock_irqsave(&p->pi_lock, flags);
406 do_set_cpus_allowed(p, mask);
407 p->flags |= PF_NO_SETAFFINITY;
408 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
411 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
413 __kthread_bind_mask(p, cpumask_of(cpu), state);
416 void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
418 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
422 * kthread_bind - bind a just-created kthread to a cpu.
423 * @p: thread created by kthread_create().
424 * @cpu: cpu (might not be online, must be possible) for @k to run on.
426 * Description: This function is equivalent to set_cpus_allowed(),
427 * except that @cpu doesn't need to be online, and the thread must be
428 * stopped (i.e., just returned from kthread_create()).
430 void kthread_bind(struct task_struct *p, unsigned int cpu)
432 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
434 EXPORT_SYMBOL(kthread_bind);
437 * kthread_create_on_cpu - Create a cpu bound kthread
438 * @threadfn: the function to run until signal_pending(current).
439 * @data: data ptr for @threadfn.
440 * @cpu: The cpu on which the thread should be bound,
441 * @namefmt: printf-style name for the thread. Format is restricted
442 * to "name.*%u". Code fills in cpu number.
444 * Description: This helper function creates and names a kernel thread
445 * The thread will be woken and put into park mode.
447 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
448 void *data, unsigned int cpu,
451 struct task_struct *p;
453 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
457 kthread_bind(p, cpu);
458 /* CPU hotplug need to bind once again when unparking the thread. */
459 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
460 to_kthread(p)->cpu = cpu;
465 * kthread_unpark - unpark a thread created by kthread_create().
466 * @k: thread created by kthread_create().
468 * Sets kthread_should_park() for @k to return false, wakes it, and
469 * waits for it to return. If the thread is marked percpu then its
470 * bound to the cpu again.
472 void kthread_unpark(struct task_struct *k)
474 struct kthread *kthread = to_kthread(k);
477 * Newly created kthread was parked when the CPU was offline.
478 * The binding was lost and we need to set it again.
480 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
481 __kthread_bind(k, kthread->cpu, TASK_PARKED);
483 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
485 * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup.
487 wake_up_state(k, TASK_PARKED);
489 EXPORT_SYMBOL_GPL(kthread_unpark);
492 * kthread_park - park a thread created by kthread_create().
493 * @k: thread created by kthread_create().
495 * Sets kthread_should_park() for @k to return true, wakes it, and
496 * waits for it to return. This can also be called after kthread_create()
497 * instead of calling wake_up_process(): the thread will park without
498 * calling threadfn().
500 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
501 * If called by the kthread itself just the park bit is set.
503 int kthread_park(struct task_struct *k)
505 struct kthread *kthread = to_kthread(k);
507 if (WARN_ON(k->flags & PF_EXITING))
510 if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK, &kthread->flags)))
513 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
517 * Wait for __kthread_parkme() to complete(), this means we
518 * _will_ have TASK_PARKED and are about to call schedule().
520 wait_for_completion(&kthread->parked);
522 * Now wait for that schedule() to complete and the task to
525 WARN_ON_ONCE(!wait_task_inactive(k, TASK_PARKED));
530 EXPORT_SYMBOL_GPL(kthread_park);
533 * kthread_stop - stop a thread created by kthread_create().
534 * @k: thread created by kthread_create().
536 * Sets kthread_should_stop() for @k to return true, wakes it, and
537 * waits for it to exit. This can also be called after kthread_create()
538 * instead of calling wake_up_process(): the thread will exit without
539 * calling threadfn().
541 * If threadfn() may call do_exit() itself, the caller must ensure
542 * task_struct can't go away.
544 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
547 int kthread_stop(struct task_struct *k)
549 struct kthread *kthread;
552 trace_sched_kthread_stop(k);
555 kthread = to_kthread(k);
556 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
559 wait_for_completion(&kthread->exited);
563 trace_sched_kthread_stop_ret(ret);
566 EXPORT_SYMBOL(kthread_stop);
568 int kthreadd(void *unused)
570 struct task_struct *tsk = current;
572 /* Setup a clean context for our children to inherit. */
573 set_task_comm(tsk, "kthreadd");
575 set_cpus_allowed_ptr(tsk, cpu_all_mask);
576 set_mems_allowed(node_states[N_MEMORY]);
578 current->flags |= PF_NOFREEZE;
579 cgroup_init_kthreadd();
582 set_current_state(TASK_INTERRUPTIBLE);
583 if (list_empty(&kthread_create_list))
585 __set_current_state(TASK_RUNNING);
587 spin_lock(&kthread_create_lock);
588 while (!list_empty(&kthread_create_list)) {
589 struct kthread_create_info *create;
591 create = list_entry(kthread_create_list.next,
592 struct kthread_create_info, list);
593 list_del_init(&create->list);
594 spin_unlock(&kthread_create_lock);
596 create_kthread(create);
598 spin_lock(&kthread_create_lock);
600 spin_unlock(&kthread_create_lock);
606 void __kthread_init_worker(struct kthread_worker *worker,
608 struct lock_class_key *key)
610 memset(worker, 0, sizeof(struct kthread_worker));
611 raw_spin_lock_init(&worker->lock);
612 lockdep_set_class_and_name(&worker->lock, key, name);
613 INIT_LIST_HEAD(&worker->work_list);
614 INIT_LIST_HEAD(&worker->delayed_work_list);
616 EXPORT_SYMBOL_GPL(__kthread_init_worker);
619 * kthread_worker_fn - kthread function to process kthread_worker
620 * @worker_ptr: pointer to initialized kthread_worker
622 * This function implements the main cycle of kthread worker. It processes
623 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
626 * The works are not allowed to keep any locks, disable preemption or interrupts
627 * when they finish. There is defined a safe point for freezing when one work
628 * finishes and before a new one is started.
630 * Also the works must not be handled by more than one worker at the same time,
631 * see also kthread_queue_work().
633 int kthread_worker_fn(void *worker_ptr)
635 struct kthread_worker *worker = worker_ptr;
636 struct kthread_work *work;
639 * FIXME: Update the check and remove the assignment when all kthread
640 * worker users are created using kthread_create_worker*() functions.
642 WARN_ON(worker->task && worker->task != current);
643 worker->task = current;
645 if (worker->flags & KTW_FREEZABLE)
649 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
651 if (kthread_should_stop()) {
652 __set_current_state(TASK_RUNNING);
653 raw_spin_lock_irq(&worker->lock);
655 raw_spin_unlock_irq(&worker->lock);
660 raw_spin_lock_irq(&worker->lock);
661 if (!list_empty(&worker->work_list)) {
662 work = list_first_entry(&worker->work_list,
663 struct kthread_work, node);
664 list_del_init(&work->node);
666 worker->current_work = work;
667 raw_spin_unlock_irq(&worker->lock);
670 __set_current_state(TASK_RUNNING);
672 } else if (!freezing(current))
679 EXPORT_SYMBOL_GPL(kthread_worker_fn);
681 static __printf(3, 0) struct kthread_worker *
682 __kthread_create_worker(int cpu, unsigned int flags,
683 const char namefmt[], va_list args)
685 struct kthread_worker *worker;
686 struct task_struct *task;
687 int node = NUMA_NO_NODE;
689 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
691 return ERR_PTR(-ENOMEM);
693 kthread_init_worker(worker);
696 node = cpu_to_node(cpu);
698 task = __kthread_create_on_node(kthread_worker_fn, worker,
699 node, namefmt, args);
704 kthread_bind(task, cpu);
706 worker->flags = flags;
708 wake_up_process(task);
713 return ERR_CAST(task);
717 * kthread_create_worker - create a kthread worker
718 * @flags: flags modifying the default behavior of the worker
719 * @namefmt: printf-style name for the kthread worker (task).
721 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
722 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
723 * when the worker was SIGKILLed.
725 struct kthread_worker *
726 kthread_create_worker(unsigned int flags, const char namefmt[], ...)
728 struct kthread_worker *worker;
731 va_start(args, namefmt);
732 worker = __kthread_create_worker(-1, flags, namefmt, args);
737 EXPORT_SYMBOL(kthread_create_worker);
740 * kthread_create_worker_on_cpu - create a kthread worker and bind it
741 * it to a given CPU and the associated NUMA node.
743 * @flags: flags modifying the default behavior of the worker
744 * @namefmt: printf-style name for the kthread worker (task).
746 * Use a valid CPU number if you want to bind the kthread worker
747 * to the given CPU and the associated NUMA node.
749 * A good practice is to add the cpu number also into the worker name.
750 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
752 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
753 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
754 * when the worker was SIGKILLed.
756 struct kthread_worker *
757 kthread_create_worker_on_cpu(int cpu, unsigned int flags,
758 const char namefmt[], ...)
760 struct kthread_worker *worker;
763 va_start(args, namefmt);
764 worker = __kthread_create_worker(cpu, flags, namefmt, args);
769 EXPORT_SYMBOL(kthread_create_worker_on_cpu);
772 * Returns true when the work could not be queued at the moment.
773 * It happens when it is already pending in a worker list
774 * or when it is being cancelled.
776 static inline bool queuing_blocked(struct kthread_worker *worker,
777 struct kthread_work *work)
779 lockdep_assert_held(&worker->lock);
781 return !list_empty(&work->node) || work->canceling;
784 static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
785 struct kthread_work *work)
787 lockdep_assert_held(&worker->lock);
788 WARN_ON_ONCE(!list_empty(&work->node));
789 /* Do not use a work with >1 worker, see kthread_queue_work() */
790 WARN_ON_ONCE(work->worker && work->worker != worker);
793 /* insert @work before @pos in @worker */
794 static void kthread_insert_work(struct kthread_worker *worker,
795 struct kthread_work *work,
796 struct list_head *pos)
798 kthread_insert_work_sanity_check(worker, work);
800 list_add_tail(&work->node, pos);
801 work->worker = worker;
802 if (!worker->current_work && likely(worker->task))
803 wake_up_process(worker->task);
807 * kthread_queue_work - queue a kthread_work
808 * @worker: target kthread_worker
809 * @work: kthread_work to queue
811 * Queue @work to work processor @task for async execution. @task
812 * must have been created with kthread_worker_create(). Returns %true
813 * if @work was successfully queued, %false if it was already pending.
815 * Reinitialize the work if it needs to be used by another worker.
816 * For example, when the worker was stopped and started again.
818 bool kthread_queue_work(struct kthread_worker *worker,
819 struct kthread_work *work)
824 raw_spin_lock_irqsave(&worker->lock, flags);
825 if (!queuing_blocked(worker, work)) {
826 kthread_insert_work(worker, work, &worker->work_list);
829 raw_spin_unlock_irqrestore(&worker->lock, flags);
832 EXPORT_SYMBOL_GPL(kthread_queue_work);
835 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
836 * delayed work when the timer expires.
837 * @t: pointer to the expired timer
839 * The format of the function is defined by struct timer_list.
840 * It should have been called from irqsafe timer with irq already off.
842 void kthread_delayed_work_timer_fn(struct timer_list *t)
844 struct kthread_delayed_work *dwork = from_timer(dwork, t, timer);
845 struct kthread_work *work = &dwork->work;
846 struct kthread_worker *worker = work->worker;
850 * This might happen when a pending work is reinitialized.
851 * It means that it is used a wrong way.
853 if (WARN_ON_ONCE(!worker))
856 raw_spin_lock_irqsave(&worker->lock, flags);
857 /* Work must not be used with >1 worker, see kthread_queue_work(). */
858 WARN_ON_ONCE(work->worker != worker);
860 /* Move the work from worker->delayed_work_list. */
861 WARN_ON_ONCE(list_empty(&work->node));
862 list_del_init(&work->node);
863 kthread_insert_work(worker, work, &worker->work_list);
865 raw_spin_unlock_irqrestore(&worker->lock, flags);
867 EXPORT_SYMBOL(kthread_delayed_work_timer_fn);
869 void __kthread_queue_delayed_work(struct kthread_worker *worker,
870 struct kthread_delayed_work *dwork,
873 struct timer_list *timer = &dwork->timer;
874 struct kthread_work *work = &dwork->work;
876 WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);
879 * If @delay is 0, queue @dwork->work immediately. This is for
880 * both optimization and correctness. The earliest @timer can
881 * expire is on the closest next tick and delayed_work users depend
882 * on that there's no such delay when @delay is 0.
885 kthread_insert_work(worker, work, &worker->work_list);
889 /* Be paranoid and try to detect possible races already now. */
890 kthread_insert_work_sanity_check(worker, work);
892 list_add(&work->node, &worker->delayed_work_list);
893 work->worker = worker;
894 timer->expires = jiffies + delay;
899 * kthread_queue_delayed_work - queue the associated kthread work
901 * @worker: target kthread_worker
902 * @dwork: kthread_delayed_work to queue
903 * @delay: number of jiffies to wait before queuing
905 * If the work has not been pending it starts a timer that will queue
906 * the work after the given @delay. If @delay is zero, it queues the
909 * Return: %false if the @work has already been pending. It means that
910 * either the timer was running or the work was queued. It returns %true
913 bool kthread_queue_delayed_work(struct kthread_worker *worker,
914 struct kthread_delayed_work *dwork,
917 struct kthread_work *work = &dwork->work;
921 raw_spin_lock_irqsave(&worker->lock, flags);
923 if (!queuing_blocked(worker, work)) {
924 __kthread_queue_delayed_work(worker, dwork, delay);
928 raw_spin_unlock_irqrestore(&worker->lock, flags);
931 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
933 struct kthread_flush_work {
934 struct kthread_work work;
935 struct completion done;
938 static void kthread_flush_work_fn(struct kthread_work *work)
940 struct kthread_flush_work *fwork =
941 container_of(work, struct kthread_flush_work, work);
942 complete(&fwork->done);
946 * kthread_flush_work - flush a kthread_work
947 * @work: work to flush
949 * If @work is queued or executing, wait for it to finish execution.
951 void kthread_flush_work(struct kthread_work *work)
953 struct kthread_flush_work fwork = {
954 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
955 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
957 struct kthread_worker *worker;
960 worker = work->worker;
964 raw_spin_lock_irq(&worker->lock);
965 /* Work must not be used with >1 worker, see kthread_queue_work(). */
966 WARN_ON_ONCE(work->worker != worker);
968 if (!list_empty(&work->node))
969 kthread_insert_work(worker, &fwork.work, work->node.next);
970 else if (worker->current_work == work)
971 kthread_insert_work(worker, &fwork.work,
972 worker->work_list.next);
976 raw_spin_unlock_irq(&worker->lock);
979 wait_for_completion(&fwork.done);
981 EXPORT_SYMBOL_GPL(kthread_flush_work);
984 * This function removes the work from the worker queue. Also it makes sure
985 * that it won't get queued later via the delayed work's timer.
987 * The work might still be in use when this function finishes. See the
988 * current_work proceed by the worker.
990 * Return: %true if @work was pending and successfully canceled,
991 * %false if @work was not pending
993 static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
994 unsigned long *flags)
996 /* Try to cancel the timer if exists. */
998 struct kthread_delayed_work *dwork =
999 container_of(work, struct kthread_delayed_work, work);
1000 struct kthread_worker *worker = work->worker;
1003 * del_timer_sync() must be called to make sure that the timer
1004 * callback is not running. The lock must be temporary released
1005 * to avoid a deadlock with the callback. In the meantime,
1006 * any queuing is blocked by setting the canceling counter.
1009 raw_spin_unlock_irqrestore(&worker->lock, *flags);
1010 del_timer_sync(&dwork->timer);
1011 raw_spin_lock_irqsave(&worker->lock, *flags);
1016 * Try to remove the work from a worker list. It might either
1017 * be from worker->work_list or from worker->delayed_work_list.
1019 if (!list_empty(&work->node)) {
1020 list_del_init(&work->node);
1028 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1029 * @worker: kthread worker to use
1030 * @dwork: kthread delayed work to queue
1031 * @delay: number of jiffies to wait before queuing
1033 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1034 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1035 * @work is guaranteed to be queued immediately.
1037 * Return: %true if @dwork was pending and its timer was modified,
1040 * A special case is when the work is being canceled in parallel.
1041 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1042 * or yet another kthread_mod_delayed_work() call. We let the other command
1043 * win and return %false here. The caller is supposed to synchronize these
1044 * operations a reasonable way.
1046 * This function is safe to call from any context including IRQ handler.
1047 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1050 bool kthread_mod_delayed_work(struct kthread_worker *worker,
1051 struct kthread_delayed_work *dwork,
1052 unsigned long delay)
1054 struct kthread_work *work = &dwork->work;
1055 unsigned long flags;
1058 raw_spin_lock_irqsave(&worker->lock, flags);
1060 /* Do not bother with canceling when never queued. */
1064 /* Work must not be used with >1 worker, see kthread_queue_work() */
1065 WARN_ON_ONCE(work->worker != worker);
1067 /* Do not fight with another command that is canceling this work. */
1068 if (work->canceling)
1071 ret = __kthread_cancel_work(work, true, &flags);
1073 __kthread_queue_delayed_work(worker, dwork, delay);
1075 raw_spin_unlock_irqrestore(&worker->lock, flags);
1078 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1080 static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1082 struct kthread_worker *worker = work->worker;
1083 unsigned long flags;
1089 raw_spin_lock_irqsave(&worker->lock, flags);
1090 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1091 WARN_ON_ONCE(work->worker != worker);
1093 ret = __kthread_cancel_work(work, is_dwork, &flags);
1095 if (worker->current_work != work)
1099 * The work is in progress and we need to wait with the lock released.
1100 * In the meantime, block any queuing by setting the canceling counter.
1103 raw_spin_unlock_irqrestore(&worker->lock, flags);
1104 kthread_flush_work(work);
1105 raw_spin_lock_irqsave(&worker->lock, flags);
1109 raw_spin_unlock_irqrestore(&worker->lock, flags);
1115 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1116 * @work: the kthread work to cancel
1118 * Cancel @work and wait for its execution to finish. This function
1119 * can be used even if the work re-queues itself. On return from this
1120 * function, @work is guaranteed to be not pending or executing on any CPU.
1122 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1123 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1125 * The caller must ensure that the worker on which @work was last
1126 * queued can't be destroyed before this function returns.
1128 * Return: %true if @work was pending, %false otherwise.
1130 bool kthread_cancel_work_sync(struct kthread_work *work)
1132 return __kthread_cancel_work_sync(work, false);
1134 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1137 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1138 * wait for it to finish.
1139 * @dwork: the kthread delayed work to cancel
1141 * This is kthread_cancel_work_sync() for delayed works.
1143 * Return: %true if @dwork was pending, %false otherwise.
1145 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1147 return __kthread_cancel_work_sync(&dwork->work, true);
1149 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1152 * kthread_flush_worker - flush all current works on a kthread_worker
1153 * @worker: worker to flush
1155 * Wait until all currently executing or pending works on @worker are
1158 void kthread_flush_worker(struct kthread_worker *worker)
1160 struct kthread_flush_work fwork = {
1161 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1162 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1165 kthread_queue_work(worker, &fwork.work);
1166 wait_for_completion(&fwork.done);
1168 EXPORT_SYMBOL_GPL(kthread_flush_worker);
1171 * kthread_destroy_worker - destroy a kthread worker
1172 * @worker: worker to be destroyed
1174 * Flush and destroy @worker. The simple flush is enough because the kthread
1175 * worker API is used only in trivial scenarios. There are no multi-step state
1178 void kthread_destroy_worker(struct kthread_worker *worker)
1180 struct task_struct *task;
1182 task = worker->task;
1186 kthread_flush_worker(worker);
1188 WARN_ON(!list_empty(&worker->work_list));
1191 EXPORT_SYMBOL(kthread_destroy_worker);
1193 #ifdef CONFIG_BLK_CGROUP
1195 * kthread_associate_blkcg - associate blkcg to current kthread
1196 * @css: the cgroup info
1198 * Current thread must be a kthread. The thread is running jobs on behalf of
1199 * other threads. In some cases, we expect the jobs attach cgroup info of
1200 * original threads instead of that of current thread. This function stores
1201 * original thread's cgroup info in current kthread context for later
1204 void kthread_associate_blkcg(struct cgroup_subsys_state *css)
1206 struct kthread *kthread;
1208 if (!(current->flags & PF_KTHREAD))
1210 kthread = to_kthread(current);
1214 if (kthread->blkcg_css) {
1215 css_put(kthread->blkcg_css);
1216 kthread->blkcg_css = NULL;
1220 kthread->blkcg_css = css;
1223 EXPORT_SYMBOL(kthread_associate_blkcg);
1226 * kthread_blkcg - get associated blkcg css of current kthread
1228 * Current thread must be a kthread.
1230 struct cgroup_subsys_state *kthread_blkcg(void)
1232 struct kthread *kthread;
1234 if (current->flags & PF_KTHREAD) {
1235 kthread = to_kthread(current);
1237 return kthread->blkcg_css;
1241 EXPORT_SYMBOL(kthread_blkcg);