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(&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 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
476 * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup.
478 wake_up_state(k, TASK_PARKED);
480 EXPORT_SYMBOL_GPL(kthread_unpark);
483 * kthread_park - park a thread created by kthread_create().
484 * @k: thread created by kthread_create().
486 * Sets kthread_should_park() for @k to return true, wakes it, and
487 * waits for it to return. This can also be called after kthread_create()
488 * instead of calling wake_up_process(): the thread will park without
489 * calling threadfn().
491 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
492 * If called by the kthread itself just the park bit is set.
494 int kthread_park(struct task_struct *k)
496 struct kthread *kthread = to_kthread(k);
498 if (WARN_ON(k->flags & PF_EXITING))
501 if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK, &kthread->flags)))
504 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
508 * Wait for __kthread_parkme() to complete(), this means we
509 * _will_ have TASK_PARKED and are about to call schedule().
511 wait_for_completion(&kthread->parked);
513 * Now wait for that schedule() to complete and the task to
516 WARN_ON_ONCE(!wait_task_inactive(k, TASK_PARKED));
521 EXPORT_SYMBOL_GPL(kthread_park);
524 * kthread_stop - stop a thread created by kthread_create().
525 * @k: thread created by kthread_create().
527 * Sets kthread_should_stop() for @k to return true, wakes it, and
528 * waits for it to exit. This can also be called after kthread_create()
529 * instead of calling wake_up_process(): the thread will exit without
530 * calling threadfn().
532 * If threadfn() may call do_exit() itself, the caller must ensure
533 * task_struct can't go away.
535 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
538 int kthread_stop(struct task_struct *k)
540 struct kthread *kthread;
543 trace_sched_kthread_stop(k);
546 kthread = to_kthread(k);
547 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
550 wait_for_completion(&kthread->exited);
554 trace_sched_kthread_stop_ret(ret);
557 EXPORT_SYMBOL(kthread_stop);
559 int kthreadd(void *unused)
561 struct task_struct *tsk = current;
563 /* Setup a clean context for our children to inherit. */
564 set_task_comm(tsk, "kthreadd");
566 set_cpus_allowed_ptr(tsk, cpu_all_mask);
567 set_mems_allowed(node_states[N_MEMORY]);
569 current->flags |= PF_NOFREEZE;
570 cgroup_init_kthreadd();
573 set_current_state(TASK_INTERRUPTIBLE);
574 if (list_empty(&kthread_create_list))
576 __set_current_state(TASK_RUNNING);
578 spin_lock(&kthread_create_lock);
579 while (!list_empty(&kthread_create_list)) {
580 struct kthread_create_info *create;
582 create = list_entry(kthread_create_list.next,
583 struct kthread_create_info, list);
584 list_del_init(&create->list);
585 spin_unlock(&kthread_create_lock);
587 create_kthread(create);
589 spin_lock(&kthread_create_lock);
591 spin_unlock(&kthread_create_lock);
597 void __kthread_init_worker(struct kthread_worker *worker,
599 struct lock_class_key *key)
601 memset(worker, 0, sizeof(struct kthread_worker));
602 raw_spin_lock_init(&worker->lock);
603 lockdep_set_class_and_name(&worker->lock, key, name);
604 INIT_LIST_HEAD(&worker->work_list);
605 INIT_LIST_HEAD(&worker->delayed_work_list);
607 EXPORT_SYMBOL_GPL(__kthread_init_worker);
610 * kthread_worker_fn - kthread function to process kthread_worker
611 * @worker_ptr: pointer to initialized kthread_worker
613 * This function implements the main cycle of kthread worker. It processes
614 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
617 * The works are not allowed to keep any locks, disable preemption or interrupts
618 * when they finish. There is defined a safe point for freezing when one work
619 * finishes and before a new one is started.
621 * Also the works must not be handled by more than one worker at the same time,
622 * see also kthread_queue_work().
624 int kthread_worker_fn(void *worker_ptr)
626 struct kthread_worker *worker = worker_ptr;
627 struct kthread_work *work;
630 * FIXME: Update the check and remove the assignment when all kthread
631 * worker users are created using kthread_create_worker*() functions.
633 WARN_ON(worker->task && worker->task != current);
634 worker->task = current;
636 if (worker->flags & KTW_FREEZABLE)
640 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
642 if (kthread_should_stop()) {
643 __set_current_state(TASK_RUNNING);
644 raw_spin_lock_irq(&worker->lock);
646 raw_spin_unlock_irq(&worker->lock);
651 raw_spin_lock_irq(&worker->lock);
652 if (!list_empty(&worker->work_list)) {
653 work = list_first_entry(&worker->work_list,
654 struct kthread_work, node);
655 list_del_init(&work->node);
657 worker->current_work = work;
658 raw_spin_unlock_irq(&worker->lock);
661 __set_current_state(TASK_RUNNING);
663 } else if (!freezing(current))
670 EXPORT_SYMBOL_GPL(kthread_worker_fn);
672 static __printf(3, 0) struct kthread_worker *
673 __kthread_create_worker(int cpu, unsigned int flags,
674 const char namefmt[], va_list args)
676 struct kthread_worker *worker;
677 struct task_struct *task;
680 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
682 return ERR_PTR(-ENOMEM);
684 kthread_init_worker(worker);
687 node = cpu_to_node(cpu);
689 task = __kthread_create_on_node(kthread_worker_fn, worker,
690 node, namefmt, args);
695 kthread_bind(task, cpu);
697 worker->flags = flags;
699 wake_up_process(task);
704 return ERR_CAST(task);
708 * kthread_create_worker - create a kthread worker
709 * @flags: flags modifying the default behavior of the worker
710 * @namefmt: printf-style name for the kthread worker (task).
712 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
713 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
714 * when the worker was SIGKILLed.
716 struct kthread_worker *
717 kthread_create_worker(unsigned int flags, const char namefmt[], ...)
719 struct kthread_worker *worker;
722 va_start(args, namefmt);
723 worker = __kthread_create_worker(-1, flags, namefmt, args);
728 EXPORT_SYMBOL(kthread_create_worker);
731 * kthread_create_worker_on_cpu - create a kthread worker and bind it
732 * it to a given CPU and the associated NUMA node.
734 * @flags: flags modifying the default behavior of the worker
735 * @namefmt: printf-style name for the kthread worker (task).
737 * Use a valid CPU number if you want to bind the kthread worker
738 * to the given CPU and the associated NUMA node.
740 * A good practice is to add the cpu number also into the worker name.
741 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
743 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
744 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
745 * when the worker was SIGKILLed.
747 struct kthread_worker *
748 kthread_create_worker_on_cpu(int cpu, unsigned int flags,
749 const char namefmt[], ...)
751 struct kthread_worker *worker;
754 va_start(args, namefmt);
755 worker = __kthread_create_worker(cpu, flags, namefmt, args);
760 EXPORT_SYMBOL(kthread_create_worker_on_cpu);
763 * Returns true when the work could not be queued at the moment.
764 * It happens when it is already pending in a worker list
765 * or when it is being cancelled.
767 static inline bool queuing_blocked(struct kthread_worker *worker,
768 struct kthread_work *work)
770 lockdep_assert_held(&worker->lock);
772 return !list_empty(&work->node) || work->canceling;
775 static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
776 struct kthread_work *work)
778 lockdep_assert_held(&worker->lock);
779 WARN_ON_ONCE(!list_empty(&work->node));
780 /* Do not use a work with >1 worker, see kthread_queue_work() */
781 WARN_ON_ONCE(work->worker && work->worker != worker);
784 /* insert @work before @pos in @worker */
785 static void kthread_insert_work(struct kthread_worker *worker,
786 struct kthread_work *work,
787 struct list_head *pos)
789 kthread_insert_work_sanity_check(worker, work);
791 list_add_tail(&work->node, pos);
792 work->worker = worker;
793 if (!worker->current_work && likely(worker->task))
794 wake_up_process(worker->task);
798 * kthread_queue_work - queue a kthread_work
799 * @worker: target kthread_worker
800 * @work: kthread_work to queue
802 * Queue @work to work processor @task for async execution. @task
803 * must have been created with kthread_worker_create(). Returns %true
804 * if @work was successfully queued, %false if it was already pending.
806 * Reinitialize the work if it needs to be used by another worker.
807 * For example, when the worker was stopped and started again.
809 bool kthread_queue_work(struct kthread_worker *worker,
810 struct kthread_work *work)
815 raw_spin_lock_irqsave(&worker->lock, flags);
816 if (!queuing_blocked(worker, work)) {
817 kthread_insert_work(worker, work, &worker->work_list);
820 raw_spin_unlock_irqrestore(&worker->lock, flags);
823 EXPORT_SYMBOL_GPL(kthread_queue_work);
826 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
827 * delayed work when the timer expires.
828 * @t: pointer to the expired timer
830 * The format of the function is defined by struct timer_list.
831 * It should have been called from irqsafe timer with irq already off.
833 void kthread_delayed_work_timer_fn(struct timer_list *t)
835 struct kthread_delayed_work *dwork = from_timer(dwork, t, timer);
836 struct kthread_work *work = &dwork->work;
837 struct kthread_worker *worker = work->worker;
841 * This might happen when a pending work is reinitialized.
842 * It means that it is used a wrong way.
844 if (WARN_ON_ONCE(!worker))
847 raw_spin_lock_irqsave(&worker->lock, flags);
848 /* Work must not be used with >1 worker, see kthread_queue_work(). */
849 WARN_ON_ONCE(work->worker != worker);
851 /* Move the work from worker->delayed_work_list. */
852 WARN_ON_ONCE(list_empty(&work->node));
853 list_del_init(&work->node);
854 kthread_insert_work(worker, work, &worker->work_list);
856 raw_spin_unlock_irqrestore(&worker->lock, flags);
858 EXPORT_SYMBOL(kthread_delayed_work_timer_fn);
860 void __kthread_queue_delayed_work(struct kthread_worker *worker,
861 struct kthread_delayed_work *dwork,
864 struct timer_list *timer = &dwork->timer;
865 struct kthread_work *work = &dwork->work;
867 WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);
870 * If @delay is 0, queue @dwork->work immediately. This is for
871 * both optimization and correctness. The earliest @timer can
872 * expire is on the closest next tick and delayed_work users depend
873 * on that there's no such delay when @delay is 0.
876 kthread_insert_work(worker, work, &worker->work_list);
880 /* Be paranoid and try to detect possible races already now. */
881 kthread_insert_work_sanity_check(worker, work);
883 list_add(&work->node, &worker->delayed_work_list);
884 work->worker = worker;
885 timer->expires = jiffies + delay;
890 * kthread_queue_delayed_work - queue the associated kthread work
892 * @worker: target kthread_worker
893 * @dwork: kthread_delayed_work to queue
894 * @delay: number of jiffies to wait before queuing
896 * If the work has not been pending it starts a timer that will queue
897 * the work after the given @delay. If @delay is zero, it queues the
900 * Return: %false if the @work has already been pending. It means that
901 * either the timer was running or the work was queued. It returns %true
904 bool kthread_queue_delayed_work(struct kthread_worker *worker,
905 struct kthread_delayed_work *dwork,
908 struct kthread_work *work = &dwork->work;
912 raw_spin_lock_irqsave(&worker->lock, flags);
914 if (!queuing_blocked(worker, work)) {
915 __kthread_queue_delayed_work(worker, dwork, delay);
919 raw_spin_unlock_irqrestore(&worker->lock, flags);
922 EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
924 struct kthread_flush_work {
925 struct kthread_work work;
926 struct completion done;
929 static void kthread_flush_work_fn(struct kthread_work *work)
931 struct kthread_flush_work *fwork =
932 container_of(work, struct kthread_flush_work, work);
933 complete(&fwork->done);
937 * kthread_flush_work - flush a kthread_work
938 * @work: work to flush
940 * If @work is queued or executing, wait for it to finish execution.
942 void kthread_flush_work(struct kthread_work *work)
944 struct kthread_flush_work fwork = {
945 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
946 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
948 struct kthread_worker *worker;
951 worker = work->worker;
955 raw_spin_lock_irq(&worker->lock);
956 /* Work must not be used with >1 worker, see kthread_queue_work(). */
957 WARN_ON_ONCE(work->worker != worker);
959 if (!list_empty(&work->node))
960 kthread_insert_work(worker, &fwork.work, work->node.next);
961 else if (worker->current_work == work)
962 kthread_insert_work(worker, &fwork.work,
963 worker->work_list.next);
967 raw_spin_unlock_irq(&worker->lock);
970 wait_for_completion(&fwork.done);
972 EXPORT_SYMBOL_GPL(kthread_flush_work);
975 * This function removes the work from the worker queue. Also it makes sure
976 * that it won't get queued later via the delayed work's timer.
978 * The work might still be in use when this function finishes. See the
979 * current_work proceed by the worker.
981 * Return: %true if @work was pending and successfully canceled,
982 * %false if @work was not pending
984 static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
985 unsigned long *flags)
987 /* Try to cancel the timer if exists. */
989 struct kthread_delayed_work *dwork =
990 container_of(work, struct kthread_delayed_work, work);
991 struct kthread_worker *worker = work->worker;
994 * del_timer_sync() must be called to make sure that the timer
995 * callback is not running. The lock must be temporary released
996 * to avoid a deadlock with the callback. In the meantime,
997 * any queuing is blocked by setting the canceling counter.
1000 raw_spin_unlock_irqrestore(&worker->lock, *flags);
1001 del_timer_sync(&dwork->timer);
1002 raw_spin_lock_irqsave(&worker->lock, *flags);
1007 * Try to remove the work from a worker list. It might either
1008 * be from worker->work_list or from worker->delayed_work_list.
1010 if (!list_empty(&work->node)) {
1011 list_del_init(&work->node);
1019 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1020 * @worker: kthread worker to use
1021 * @dwork: kthread delayed work to queue
1022 * @delay: number of jiffies to wait before queuing
1024 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1025 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1026 * @work is guaranteed to be queued immediately.
1028 * Return: %true if @dwork was pending and its timer was modified,
1031 * A special case is when the work is being canceled in parallel.
1032 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1033 * or yet another kthread_mod_delayed_work() call. We let the other command
1034 * win and return %false here. The caller is supposed to synchronize these
1035 * operations a reasonable way.
1037 * This function is safe to call from any context including IRQ handler.
1038 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1041 bool kthread_mod_delayed_work(struct kthread_worker *worker,
1042 struct kthread_delayed_work *dwork,
1043 unsigned long delay)
1045 struct kthread_work *work = &dwork->work;
1046 unsigned long flags;
1049 raw_spin_lock_irqsave(&worker->lock, flags);
1051 /* Do not bother with canceling when never queued. */
1055 /* Work must not be used with >1 worker, see kthread_queue_work() */
1056 WARN_ON_ONCE(work->worker != worker);
1058 /* Do not fight with another command that is canceling this work. */
1059 if (work->canceling)
1062 ret = __kthread_cancel_work(work, true, &flags);
1064 __kthread_queue_delayed_work(worker, dwork, delay);
1066 raw_spin_unlock_irqrestore(&worker->lock, flags);
1069 EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1071 static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1073 struct kthread_worker *worker = work->worker;
1074 unsigned long flags;
1080 raw_spin_lock_irqsave(&worker->lock, flags);
1081 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1082 WARN_ON_ONCE(work->worker != worker);
1084 ret = __kthread_cancel_work(work, is_dwork, &flags);
1086 if (worker->current_work != work)
1090 * The work is in progress and we need to wait with the lock released.
1091 * In the meantime, block any queuing by setting the canceling counter.
1094 raw_spin_unlock_irqrestore(&worker->lock, flags);
1095 kthread_flush_work(work);
1096 raw_spin_lock_irqsave(&worker->lock, flags);
1100 raw_spin_unlock_irqrestore(&worker->lock, flags);
1106 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1107 * @work: the kthread work to cancel
1109 * Cancel @work and wait for its execution to finish. This function
1110 * can be used even if the work re-queues itself. On return from this
1111 * function, @work is guaranteed to be not pending or executing on any CPU.
1113 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1114 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1116 * The caller must ensure that the worker on which @work was last
1117 * queued can't be destroyed before this function returns.
1119 * Return: %true if @work was pending, %false otherwise.
1121 bool kthread_cancel_work_sync(struct kthread_work *work)
1123 return __kthread_cancel_work_sync(work, false);
1125 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1128 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1129 * wait for it to finish.
1130 * @dwork: the kthread delayed work to cancel
1132 * This is kthread_cancel_work_sync() for delayed works.
1134 * Return: %true if @dwork was pending, %false otherwise.
1136 bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1138 return __kthread_cancel_work_sync(&dwork->work, true);
1140 EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1143 * kthread_flush_worker - flush all current works on a kthread_worker
1144 * @worker: worker to flush
1146 * Wait until all currently executing or pending works on @worker are
1149 void kthread_flush_worker(struct kthread_worker *worker)
1151 struct kthread_flush_work fwork = {
1152 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1153 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1156 kthread_queue_work(worker, &fwork.work);
1157 wait_for_completion(&fwork.done);
1159 EXPORT_SYMBOL_GPL(kthread_flush_worker);
1162 * kthread_destroy_worker - destroy a kthread worker
1163 * @worker: worker to be destroyed
1165 * Flush and destroy @worker. The simple flush is enough because the kthread
1166 * worker API is used only in trivial scenarios. There are no multi-step state
1169 void kthread_destroy_worker(struct kthread_worker *worker)
1171 struct task_struct *task;
1173 task = worker->task;
1177 kthread_flush_worker(worker);
1179 WARN_ON(!list_empty(&worker->work_list));
1182 EXPORT_SYMBOL(kthread_destroy_worker);
1184 #ifdef CONFIG_BLK_CGROUP
1186 * kthread_associate_blkcg - associate blkcg to current kthread
1187 * @css: the cgroup info
1189 * Current thread must be a kthread. The thread is running jobs on behalf of
1190 * other threads. In some cases, we expect the jobs attach cgroup info of
1191 * original threads instead of that of current thread. This function stores
1192 * original thread's cgroup info in current kthread context for later
1195 void kthread_associate_blkcg(struct cgroup_subsys_state *css)
1197 struct kthread *kthread;
1199 if (!(current->flags & PF_KTHREAD))
1201 kthread = to_kthread(current);
1205 if (kthread->blkcg_css) {
1206 css_put(kthread->blkcg_css);
1207 kthread->blkcg_css = NULL;
1211 kthread->blkcg_css = css;
1214 EXPORT_SYMBOL(kthread_associate_blkcg);
1217 * kthread_blkcg - get associated blkcg css of current kthread
1219 * Current thread must be a kthread.
1221 struct cgroup_subsys_state *kthread_blkcg(void)
1223 struct kthread *kthread;
1225 if (current->flags & PF_KTHREAD) {
1226 kthread = to_kthread(current);
1228 return kthread->blkcg_css;
1232 EXPORT_SYMBOL(kthread_blkcg);