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 <trace/events/sched.h>
25 static DEFINE_SPINLOCK(kthread_create_lock);
26 static LIST_HEAD(kthread_create_list);
27 struct task_struct *kthreadd_task;
29 struct kthread_create_info
31 /* Information passed to kthread() from kthreadd. */
32 int (*threadfn)(void *data);
36 /* Result passed back to kthread_create() from kthreadd. */
37 struct task_struct *result;
38 struct completion *done;
40 struct list_head list;
47 struct completion parked;
48 struct completion exited;
49 #ifdef CONFIG_BLK_CGROUP
50 struct cgroup_subsys_state *blkcg_css;
55 KTHREAD_IS_PER_CPU = 0,
60 static inline void set_kthread_struct(void *kthread)
63 * We abuse ->set_child_tid to avoid the new member and because it
64 * can't be wrongly copied by copy_process(). We also rely on fact
65 * that the caller can't exec, so PF_KTHREAD can't be cleared.
67 current->set_child_tid = (__force void __user *)kthread;
70 static inline struct kthread *to_kthread(struct task_struct *k)
72 WARN_ON(!(k->flags & PF_KTHREAD));
73 return (__force void *)k->set_child_tid;
76 void free_kthread_struct(struct task_struct *k)
78 struct kthread *kthread;
81 * Can be NULL if this kthread was created by kernel_thread()
82 * or if kmalloc() in kthread() failed.
84 kthread = to_kthread(k);
85 #ifdef CONFIG_BLK_CGROUP
86 WARN_ON_ONCE(kthread && kthread->blkcg_css);
92 * kthread_should_stop - should this kthread return now?
94 * When someone calls kthread_stop() on your kthread, it will be woken
95 * and this will return true. You should then return, and your return
96 * value will be passed through to kthread_stop().
98 bool kthread_should_stop(void)
100 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
102 EXPORT_SYMBOL(kthread_should_stop);
105 * kthread_should_park - should this kthread park now?
107 * When someone calls kthread_park() on your kthread, it will be woken
108 * and this will return true. You should then do the necessary
109 * cleanup and call kthread_parkme()
111 * Similar to kthread_should_stop(), but this keeps the thread alive
112 * and in a park position. kthread_unpark() "restarts" the thread and
113 * calls the thread function again.
115 bool kthread_should_park(void)
117 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
119 EXPORT_SYMBOL_GPL(kthread_should_park);
122 * kthread_freezable_should_stop - should this freezable kthread return now?
123 * @was_frozen: optional out parameter, indicates whether %current was frozen
125 * kthread_should_stop() for freezable kthreads, which will enter
126 * refrigerator if necessary. This function is safe from kthread_stop() /
127 * freezer deadlock and freezable kthreads should use this function instead
128 * of calling try_to_freeze() directly.
130 bool kthread_freezable_should_stop(bool *was_frozen)
136 if (unlikely(freezing(current)))
137 frozen = __refrigerator(true);
140 *was_frozen = frozen;
142 return kthread_should_stop();
144 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
147 * kthread_data - return data value specified on kthread creation
148 * @task: kthread task in question
150 * Return the data value specified when kthread @task was created.
151 * The caller is responsible for ensuring the validity of @task when
152 * calling this function.
154 void *kthread_data(struct task_struct *task)
156 return to_kthread(task)->data;
160 * kthread_probe_data - speculative version of kthread_data()
161 * @task: possible kthread task in question
163 * @task could be a kthread task. Return the data value specified when it
164 * was created if accessible. If @task isn't a kthread task or its data is
165 * inaccessible for any reason, %NULL is returned. This function requires
166 * that @task itself is safe to dereference.
168 void *kthread_probe_data(struct task_struct *task)
170 struct kthread *kthread = to_kthread(task);
173 probe_kernel_read(&data, &kthread->data, sizeof(data));
177 static void __kthread_parkme(struct kthread *self)
181 * TASK_PARKED is a special state; we must serialize against
182 * possible pending wakeups to avoid store-store collisions on
185 * Such a collision might possibly result in the task state
186 * changin from TASK_PARKED and us failing the
187 * wait_task_inactive() in kthread_park().
189 set_special_state(TASK_PARKED);
190 if (!test_bit(KTHREAD_SHOULD_PARK, &self->flags))
193 complete_all(&self->parked);
196 __set_current_state(TASK_RUNNING);
199 void kthread_parkme(void)
201 __kthread_parkme(to_kthread(current));
203 EXPORT_SYMBOL_GPL(kthread_parkme);
205 static int kthread(void *_create)
207 /* Copy data: it's on kthread's stack */
208 struct kthread_create_info *create = _create;
209 int (*threadfn)(void *data) = create->threadfn;
210 void *data = create->data;
211 struct completion *done;
212 struct kthread *self;
215 self = kzalloc(sizeof(*self), GFP_KERNEL);
216 set_kthread_struct(self);
218 /* If user was SIGKILLed, I release the structure. */
219 done = xchg(&create->done, NULL);
226 create->result = ERR_PTR(-ENOMEM);
232 init_completion(&self->exited);
233 init_completion(&self->parked);
234 current->vfork_done = &self->exited;
236 /* OK, tell user we're spawned, wait for stop or wakeup */
237 __set_current_state(TASK_UNINTERRUPTIBLE);
238 create->result = current;
243 if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
244 cgroup_kthread_ready();
245 __kthread_parkme(self);
246 ret = threadfn(data);
251 /* called from do_fork() to get node information for about to be created task */
252 int tsk_fork_get_node(struct task_struct *tsk)
255 if (tsk == kthreadd_task)
256 return tsk->pref_node_fork;
261 static void create_kthread(struct kthread_create_info *create)
266 current->pref_node_fork = create->node;
268 /* We want our own signal handler (we take no signals by default). */
269 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
271 /* If user was SIGKILLed, I release the structure. */
272 struct completion *done = xchg(&create->done, NULL);
278 create->result = ERR_PTR(pid);
283 static __printf(4, 0)
284 struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
285 void *data, int node,
286 const char namefmt[],
289 DECLARE_COMPLETION_ONSTACK(done);
290 struct task_struct *task;
291 struct kthread_create_info *create = kmalloc(sizeof(*create),
295 return ERR_PTR(-ENOMEM);
296 create->threadfn = threadfn;
299 create->done = &done;
301 spin_lock(&kthread_create_lock);
302 list_add_tail(&create->list, &kthread_create_list);
303 spin_unlock(&kthread_create_lock);
305 wake_up_process(kthreadd_task);
307 * Wait for completion in killable state, for I might be chosen by
308 * the OOM killer while kthreadd is trying to allocate memory for
311 if (unlikely(wait_for_completion_killable(&done))) {
313 * If I was SIGKILLed before kthreadd (or new kernel thread)
314 * calls complete(), leave the cleanup of this structure to
317 if (xchg(&create->done, NULL))
318 return ERR_PTR(-EINTR);
320 * kthreadd (or new kernel thread) will call complete()
323 wait_for_completion(&done);
325 task = create->result;
327 static const struct sched_param param = { .sched_priority = 0 };
328 char name[TASK_COMM_LEN];
331 * task is already visible to other tasks, so updating
332 * COMM must be protected.
334 vsnprintf(name, sizeof(name), namefmt, args);
335 set_task_comm(task, name);
337 * root may have changed our (kthreadd's) priority or CPU mask.
338 * The kernel thread should not inherit these properties.
340 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
341 set_cpus_allowed_ptr(task, cpu_all_mask);
348 * kthread_create_on_node - create a kthread.
349 * @threadfn: the function to run until signal_pending(current).
350 * @data: data ptr for @threadfn.
351 * @node: task and thread structures for the thread are allocated on this node
352 * @namefmt: printf-style name for the thread.
354 * Description: This helper function creates and names a kernel
355 * thread. The thread will be stopped: use wake_up_process() to start
356 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
357 * is affine to all CPUs.
359 * If thread is going to be bound on a particular cpu, give its node
360 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
361 * When woken, the thread will run @threadfn() with @data as its
362 * argument. @threadfn() can either call do_exit() directly if it is a
363 * standalone thread for which no one will call kthread_stop(), or
364 * return when 'kthread_should_stop()' is true (which means
365 * kthread_stop() has been called). The return value should be zero
366 * or a negative error number; it will be passed to kthread_stop().
368 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
370 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
371 void *data, int node,
372 const char namefmt[],
375 struct task_struct *task;
378 va_start(args, namefmt);
379 task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
384 EXPORT_SYMBOL(kthread_create_on_node);
386 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
390 if (!wait_task_inactive(p, state)) {
395 /* It's safe because the task is inactive. */
396 raw_spin_lock_irqsave(&p->pi_lock, flags);
397 do_set_cpus_allowed(p, mask);
398 p->flags |= PF_NO_SETAFFINITY;
399 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
402 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
404 __kthread_bind_mask(p, cpumask_of(cpu), state);
407 void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
409 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
413 * kthread_bind - bind a just-created kthread to a cpu.
414 * @p: thread created by kthread_create().
415 * @cpu: cpu (might not be online, must be possible) for @k to run on.
417 * Description: This function is equivalent to set_cpus_allowed(),
418 * except that @cpu doesn't need to be online, and the thread must be
419 * stopped (i.e., just returned from kthread_create()).
421 void kthread_bind(struct task_struct *p, unsigned int cpu)
423 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
425 EXPORT_SYMBOL(kthread_bind);
428 * kthread_create_on_cpu - Create a cpu bound kthread
429 * @threadfn: the function to run until signal_pending(current).
430 * @data: data ptr for @threadfn.
431 * @cpu: The cpu on which the thread should be bound,
432 * @namefmt: printf-style name for the thread. Format is restricted
433 * to "name.*%u". Code fills in cpu number.
435 * Description: This helper function creates and names a kernel thread
436 * The thread will be woken and put into park mode.
438 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
439 void *data, unsigned int cpu,
442 struct task_struct *p;
444 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
448 kthread_bind(p, cpu);
449 /* CPU hotplug need to bind once again when unparking the thread. */
450 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
451 to_kthread(p)->cpu = cpu;
456 * kthread_unpark - unpark a thread created by kthread_create().
457 * @k: thread created by kthread_create().
459 * Sets kthread_should_park() for @k to return false, wakes it, and
460 * waits for it to return. If the thread is marked percpu then its
461 * bound to the cpu again.
463 void kthread_unpark(struct task_struct *k)
465 struct kthread *kthread = to_kthread(k);
468 * Newly created kthread was parked when the CPU was offline.
469 * The binding was lost and we need to set it again.
471 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
472 __kthread_bind(k, kthread->cpu, TASK_PARKED);
474 reinit_completion(&kthread->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 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
506 * Wait for __kthread_parkme() to complete(), this means we
507 * _will_ have TASK_PARKED and are about to call schedule().
509 wait_for_completion(&kthread->parked);
511 * Now wait for that schedule() to complete and the task to
514 WARN_ON_ONCE(!wait_task_inactive(k, TASK_PARKED));
519 EXPORT_SYMBOL_GPL(kthread_park);
522 * kthread_stop - stop a thread created by kthread_create().
523 * @k: thread created by kthread_create().
525 * Sets kthread_should_stop() for @k to return true, wakes it, and
526 * waits for it to exit. This can also be called after kthread_create()
527 * instead of calling wake_up_process(): the thread will exit without
528 * calling threadfn().
530 * If threadfn() may call do_exit() itself, the caller must ensure
531 * task_struct can't go away.
533 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
536 int kthread_stop(struct task_struct *k)
538 struct kthread *kthread;
541 trace_sched_kthread_stop(k);
544 kthread = to_kthread(k);
545 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
548 wait_for_completion(&kthread->exited);
552 trace_sched_kthread_stop_ret(ret);
555 EXPORT_SYMBOL(kthread_stop);
557 int kthreadd(void *unused)
559 struct task_struct *tsk = current;
561 /* Setup a clean context for our children to inherit. */
562 set_task_comm(tsk, "kthreadd");
564 set_cpus_allowed_ptr(tsk, cpu_all_mask);
565 set_mems_allowed(node_states[N_MEMORY]);
567 current->flags |= PF_NOFREEZE;
568 cgroup_init_kthreadd();
571 set_current_state(TASK_INTERRUPTIBLE);
572 if (list_empty(&kthread_create_list))
574 __set_current_state(TASK_RUNNING);
576 spin_lock(&kthread_create_lock);
577 while (!list_empty(&kthread_create_list)) {
578 struct kthread_create_info *create;
580 create = list_entry(kthread_create_list.next,
581 struct kthread_create_info, list);
582 list_del_init(&create->list);
583 spin_unlock(&kthread_create_lock);
585 create_kthread(create);
587 spin_lock(&kthread_create_lock);
589 spin_unlock(&kthread_create_lock);
595 void __kthread_init_worker(struct kthread_worker *worker,
597 struct lock_class_key *key)
599 memset(worker, 0, sizeof(struct kthread_worker));
600 spin_lock_init(&worker->lock);
601 lockdep_set_class_and_name(&worker->lock, key, name);
602 INIT_LIST_HEAD(&worker->work_list);
603 INIT_LIST_HEAD(&worker->delayed_work_list);
605 EXPORT_SYMBOL_GPL(__kthread_init_worker);
608 * kthread_worker_fn - kthread function to process kthread_worker
609 * @worker_ptr: pointer to initialized kthread_worker
611 * This function implements the main cycle of kthread worker. It processes
612 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
615 * The works are not allowed to keep any locks, disable preemption or interrupts
616 * when they finish. There is defined a safe point for freezing when one work
617 * finishes and before a new one is started.
619 * Also the works must not be handled by more than one worker at the same time,
620 * see also kthread_queue_work().
622 int kthread_worker_fn(void *worker_ptr)
624 struct kthread_worker *worker = worker_ptr;
625 struct kthread_work *work;
628 * FIXME: Update the check and remove the assignment when all kthread
629 * worker users are created using kthread_create_worker*() functions.
631 WARN_ON(worker->task && worker->task != current);
632 worker->task = current;
634 if (worker->flags & KTW_FREEZABLE)
638 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
640 if (kthread_should_stop()) {
641 __set_current_state(TASK_RUNNING);
642 spin_lock_irq(&worker->lock);
644 spin_unlock_irq(&worker->lock);
649 spin_lock_irq(&worker->lock);
650 if (!list_empty(&worker->work_list)) {
651 work = list_first_entry(&worker->work_list,
652 struct kthread_work, node);
653 list_del_init(&work->node);
655 worker->current_work = work;
656 spin_unlock_irq(&worker->lock);
659 __set_current_state(TASK_RUNNING);
661 } else if (!freezing(current))
668 EXPORT_SYMBOL_GPL(kthread_worker_fn);
670 static __printf(3, 0) struct kthread_worker *
671 __kthread_create_worker(int cpu, unsigned int flags,
672 const char namefmt[], va_list args)
674 struct kthread_worker *worker;
675 struct task_struct *task;
678 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
680 return ERR_PTR(-ENOMEM);
682 kthread_init_worker(worker);
685 node = cpu_to_node(cpu);
687 task = __kthread_create_on_node(kthread_worker_fn, worker,
688 node, namefmt, args);
693 kthread_bind(task, cpu);
695 worker->flags = flags;
697 wake_up_process(task);
702 return ERR_CAST(task);
706 * kthread_create_worker - create a kthread worker
707 * @flags: flags modifying the default behavior of the worker
708 * @namefmt: printf-style name for the kthread worker (task).
710 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
711 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
712 * when the worker was SIGKILLed.
714 struct kthread_worker *
715 kthread_create_worker(unsigned int flags, const char namefmt[], ...)
717 struct kthread_worker *worker;
720 va_start(args, namefmt);
721 worker = __kthread_create_worker(-1, flags, namefmt, args);
726 EXPORT_SYMBOL(kthread_create_worker);
729 * kthread_create_worker_on_cpu - create a kthread worker and bind it
730 * it to a given CPU and the associated NUMA node.
732 * @flags: flags modifying the default behavior of the worker
733 * @namefmt: printf-style name for the kthread worker (task).
735 * Use a valid CPU number if you want to bind the kthread worker
736 * to the given CPU and the associated NUMA node.
738 * A good practice is to add the cpu number also into the worker name.
739 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
741 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
742 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
743 * when the worker was SIGKILLed.
745 struct kthread_worker *
746 kthread_create_worker_on_cpu(int cpu, unsigned int flags,
747 const char namefmt[], ...)
749 struct kthread_worker *worker;
752 va_start(args, namefmt);
753 worker = __kthread_create_worker(cpu, flags, namefmt, args);
758 EXPORT_SYMBOL(kthread_create_worker_on_cpu);
761 * Returns true when the work could not be queued at the moment.
762 * It happens when it is already pending in a worker list
763 * or when it is being cancelled.
765 static inline bool queuing_blocked(struct kthread_worker *worker,
766 struct kthread_work *work)
768 lockdep_assert_held(&worker->lock);
770 return !list_empty(&work->node) || work->canceling;
773 static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
774 struct kthread_work *work)
776 lockdep_assert_held(&worker->lock);
777 WARN_ON_ONCE(!list_empty(&work->node));
778 /* Do not use a work with >1 worker, see kthread_queue_work() */
779 WARN_ON_ONCE(work->worker && work->worker != worker);
782 /* insert @work before @pos in @worker */
783 static void kthread_insert_work(struct kthread_worker *worker,
784 struct kthread_work *work,
785 struct list_head *pos)
787 kthread_insert_work_sanity_check(worker, work);
789 list_add_tail(&work->node, pos);
790 work->worker = worker;
791 if (!worker->current_work && likely(worker->task))
792 wake_up_process(worker->task);
796 * kthread_queue_work - queue a kthread_work
797 * @worker: target kthread_worker
798 * @work: kthread_work to queue
800 * Queue @work to work processor @task for async execution. @task
801 * must have been created with kthread_worker_create(). Returns %true
802 * if @work was successfully queued, %false if it was already pending.
804 * Reinitialize the work if it needs to be used by another worker.
805 * For example, when the worker was stopped and started again.
807 bool kthread_queue_work(struct kthread_worker *worker,
808 struct kthread_work *work)
813 spin_lock_irqsave(&worker->lock, flags);
814 if (!queuing_blocked(worker, work)) {
815 kthread_insert_work(worker, work, &worker->work_list);
818 spin_unlock_irqrestore(&worker->lock, flags);
821 EXPORT_SYMBOL_GPL(kthread_queue_work);
824 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
825 * delayed work when the timer expires.
826 * @t: pointer to the expired timer
828 * The format of the function is defined by struct timer_list.
829 * It should have been called from irqsafe timer with irq already off.
831 void kthread_delayed_work_timer_fn(struct timer_list *t)
833 struct kthread_delayed_work *dwork = from_timer(dwork, t, timer);
834 struct kthread_work *work = &dwork->work;
835 struct kthread_worker *worker = work->worker;
838 * This might happen when a pending work is reinitialized.
839 * It means that it is used a wrong way.
841 if (WARN_ON_ONCE(!worker))
844 spin_lock(&worker->lock);
845 /* Work must not be used with >1 worker, see kthread_queue_work(). */
846 WARN_ON_ONCE(work->worker != worker);
848 /* Move the work from worker->delayed_work_list. */
849 WARN_ON_ONCE(list_empty(&work->node));
850 list_del_init(&work->node);
851 kthread_insert_work(worker, work, &worker->work_list);
853 spin_unlock(&worker->lock);
855 EXPORT_SYMBOL(kthread_delayed_work_timer_fn);
857 void __kthread_queue_delayed_work(struct kthread_worker *worker,
858 struct kthread_delayed_work *dwork,
861 struct timer_list *timer = &dwork->timer;
862 struct kthread_work *work = &dwork->work;
864 WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);
867 * If @delay is 0, queue @dwork->work immediately. This is for
868 * both optimization and correctness. The earliest @timer can
869 * expire is on the closest next tick and delayed_work users depend
870 * on that there's no such delay when @delay is 0.
873 kthread_insert_work(worker, work, &worker->work_list);
877 /* Be paranoid and try to detect possible races already now. */
878 kthread_insert_work_sanity_check(worker, work);
880 list_add(&work->node, &worker->delayed_work_list);
881 work->worker = worker;
882 timer->expires = jiffies + delay;
887 * kthread_queue_delayed_work - queue the associated kthread work
889 * @worker: target kthread_worker
890 * @dwork: kthread_delayed_work to queue
891 * @delay: number of jiffies to wait before queuing
893 * If the work has not been pending it starts a timer that will queue
894 * the work after the given @delay. If @delay is zero, it queues the
897 * Return: %false if the @work has already been pending. It means that
898 * either the timer was running or the work was queued. It returns %true
901 bool kthread_queue_delayed_work(struct kthread_worker *worker,
902 struct kthread_delayed_work *dwork,
905 struct kthread_work *work = &dwork->work;
909 spin_lock_irqsave(&worker->lock, flags);
911 if (!queuing_blocked(worker, work)) {
912 __kthread_queue_delayed_work(worker, dwork, delay);
916 spin_unlock_irqrestore(&worker->lock, flags);
919 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
921 struct kthread_flush_work {
922 struct kthread_work work;
923 struct completion done;
926 static void kthread_flush_work_fn(struct kthread_work *work)
928 struct kthread_flush_work *fwork =
929 container_of(work, struct kthread_flush_work, work);
930 complete(&fwork->done);
934 * kthread_flush_work - flush a kthread_work
935 * @work: work to flush
937 * If @work is queued or executing, wait for it to finish execution.
939 void kthread_flush_work(struct kthread_work *work)
941 struct kthread_flush_work fwork = {
942 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
943 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
945 struct kthread_worker *worker;
948 worker = work->worker;
952 spin_lock_irq(&worker->lock);
953 /* Work must not be used with >1 worker, see kthread_queue_work(). */
954 WARN_ON_ONCE(work->worker != worker);
956 if (!list_empty(&work->node))
957 kthread_insert_work(worker, &fwork.work, work->node.next);
958 else if (worker->current_work == work)
959 kthread_insert_work(worker, &fwork.work,
960 worker->work_list.next);
964 spin_unlock_irq(&worker->lock);
967 wait_for_completion(&fwork.done);
969 EXPORT_SYMBOL_GPL(kthread_flush_work);
972 * This function removes the work from the worker queue. Also it makes sure
973 * that it won't get queued later via the delayed work's timer.
975 * The work might still be in use when this function finishes. See the
976 * current_work proceed by the worker.
978 * Return: %true if @work was pending and successfully canceled,
979 * %false if @work was not pending
981 static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
982 unsigned long *flags)
984 /* Try to cancel the timer if exists. */
986 struct kthread_delayed_work *dwork =
987 container_of(work, struct kthread_delayed_work, work);
988 struct kthread_worker *worker = work->worker;
991 * del_timer_sync() must be called to make sure that the timer
992 * callback is not running. The lock must be temporary released
993 * to avoid a deadlock with the callback. In the meantime,
994 * any queuing is blocked by setting the canceling counter.
997 spin_unlock_irqrestore(&worker->lock, *flags);
998 del_timer_sync(&dwork->timer);
999 spin_lock_irqsave(&worker->lock, *flags);
1004 * Try to remove the work from a worker list. It might either
1005 * be from worker->work_list or from worker->delayed_work_list.
1007 if (!list_empty(&work->node)) {
1008 list_del_init(&work->node);
1016 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1017 * @worker: kthread worker to use
1018 * @dwork: kthread delayed work to queue
1019 * @delay: number of jiffies to wait before queuing
1021 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1022 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1023 * @work is guaranteed to be queued immediately.
1025 * Return: %true if @dwork was pending and its timer was modified,
1028 * A special case is when the work is being canceled in parallel.
1029 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1030 * or yet another kthread_mod_delayed_work() call. We let the other command
1031 * win and return %false here. The caller is supposed to synchronize these
1032 * operations a reasonable way.
1034 * This function is safe to call from any context including IRQ handler.
1035 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1038 bool kthread_mod_delayed_work(struct kthread_worker *worker,
1039 struct kthread_delayed_work *dwork,
1040 unsigned long delay)
1042 struct kthread_work *work = &dwork->work;
1043 unsigned long flags;
1046 spin_lock_irqsave(&worker->lock, flags);
1048 /* Do not bother with canceling when never queued. */
1052 /* Work must not be used with >1 worker, see kthread_queue_work() */
1053 WARN_ON_ONCE(work->worker != worker);
1055 /* Do not fight with another command that is canceling this work. */
1056 if (work->canceling)
1059 ret = __kthread_cancel_work(work, true, &flags);
1061 __kthread_queue_delayed_work(worker, dwork, delay);
1063 spin_unlock_irqrestore(&worker->lock, flags);
1066 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1068 static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1070 struct kthread_worker *worker = work->worker;
1071 unsigned long flags;
1077 spin_lock_irqsave(&worker->lock, flags);
1078 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1079 WARN_ON_ONCE(work->worker != worker);
1081 ret = __kthread_cancel_work(work, is_dwork, &flags);
1083 if (worker->current_work != work)
1087 * The work is in progress and we need to wait with the lock released.
1088 * In the meantime, block any queuing by setting the canceling counter.
1091 spin_unlock_irqrestore(&worker->lock, flags);
1092 kthread_flush_work(work);
1093 spin_lock_irqsave(&worker->lock, flags);
1097 spin_unlock_irqrestore(&worker->lock, flags);
1103 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1104 * @work: the kthread work to cancel
1106 * Cancel @work and wait for its execution to finish. This function
1107 * can be used even if the work re-queues itself. On return from this
1108 * function, @work is guaranteed to be not pending or executing on any CPU.
1110 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1111 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1113 * The caller must ensure that the worker on which @work was last
1114 * queued can't be destroyed before this function returns.
1116 * Return: %true if @work was pending, %false otherwise.
1118 bool kthread_cancel_work_sync(struct kthread_work *work)
1120 return __kthread_cancel_work_sync(work, false);
1122 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1125 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1126 * wait for it to finish.
1127 * @dwork: the kthread delayed work to cancel
1129 * This is kthread_cancel_work_sync() for delayed works.
1131 * Return: %true if @dwork was pending, %false otherwise.
1133 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1135 return __kthread_cancel_work_sync(&dwork->work, true);
1137 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1140 * kthread_flush_worker - flush all current works on a kthread_worker
1141 * @worker: worker to flush
1143 * Wait until all currently executing or pending works on @worker are
1146 void kthread_flush_worker(struct kthread_worker *worker)
1148 struct kthread_flush_work fwork = {
1149 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1150 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1153 kthread_queue_work(worker, &fwork.work);
1154 wait_for_completion(&fwork.done);
1156 EXPORT_SYMBOL_GPL(kthread_flush_worker);
1159 * kthread_destroy_worker - destroy a kthread worker
1160 * @worker: worker to be destroyed
1162 * Flush and destroy @worker. The simple flush is enough because the kthread
1163 * worker API is used only in trivial scenarios. There are no multi-step state
1166 void kthread_destroy_worker(struct kthread_worker *worker)
1168 struct task_struct *task;
1170 task = worker->task;
1174 kthread_flush_worker(worker);
1176 WARN_ON(!list_empty(&worker->work_list));
1179 EXPORT_SYMBOL(kthread_destroy_worker);
1181 #ifdef CONFIG_BLK_CGROUP
1183 * kthread_associate_blkcg - associate blkcg to current kthread
1184 * @css: the cgroup info
1186 * Current thread must be a kthread. The thread is running jobs on behalf of
1187 * other threads. In some cases, we expect the jobs attach cgroup info of
1188 * original threads instead of that of current thread. This function stores
1189 * original thread's cgroup info in current kthread context for later
1192 void kthread_associate_blkcg(struct cgroup_subsys_state *css)
1194 struct kthread *kthread;
1196 if (!(current->flags & PF_KTHREAD))
1198 kthread = to_kthread(current);
1202 if (kthread->blkcg_css) {
1203 css_put(kthread->blkcg_css);
1204 kthread->blkcg_css = NULL;
1208 kthread->blkcg_css = css;
1211 EXPORT_SYMBOL(kthread_associate_blkcg);
1214 * kthread_blkcg - get associated blkcg css of current kthread
1216 * Current thread must be a kthread.
1218 struct cgroup_subsys_state *kthread_blkcg(void)
1220 struct kthread *kthread;
1222 if (current->flags & PF_KTHREAD) {
1223 kthread = to_kthread(current);
1225 return kthread->blkcg_css;
1229 EXPORT_SYMBOL(kthread_blkcg);