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 <linux/sched.h>
9 #include <linux/kthread.h>
10 #include <linux/completion.h>
11 #include <linux/err.h>
12 #include <linux/cpuset.h>
13 #include <linux/unistd.h>
14 #include <linux/file.h>
15 #include <linux/export.h>
16 #include <linux/mutex.h>
17 #include <linux/slab.h>
18 #include <linux/freezer.h>
19 #include <linux/ptrace.h>
20 #include <linux/uaccess.h>
21 #include <linux/cgroup.h>
22 #include <trace/events/sched.h>
24 static DEFINE_SPINLOCK(kthread_create_lock);
25 static LIST_HEAD(kthread_create_list);
26 struct task_struct *kthreadd_task;
28 struct kthread_create_info
30 /* Information passed to kthread() from kthreadd. */
31 int (*threadfn)(void *data);
35 /* Result passed back to kthread_create() from kthreadd. */
36 struct task_struct *result;
37 struct completion *done;
39 struct list_head list;
46 struct completion parked;
47 struct completion exited;
51 KTHREAD_IS_PER_CPU = 0,
57 #define __to_kthread(vfork) \
58 container_of(vfork, struct kthread, exited)
60 static inline struct kthread *to_kthread(struct task_struct *k)
62 return __to_kthread(k->vfork_done);
65 static struct kthread *to_live_kthread(struct task_struct *k)
67 struct completion *vfork = ACCESS_ONCE(k->vfork_done);
68 if (likely(vfork) && try_get_task_stack(k))
69 return __to_kthread(vfork);
74 * kthread_should_stop - should this kthread return now?
76 * When someone calls kthread_stop() on your kthread, it will be woken
77 * and this will return true. You should then return, and your return
78 * value will be passed through to kthread_stop().
80 bool kthread_should_stop(void)
82 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
84 EXPORT_SYMBOL(kthread_should_stop);
87 * kthread_should_park - should this kthread park now?
89 * When someone calls kthread_park() on your kthread, it will be woken
90 * and this will return true. You should then do the necessary
91 * cleanup and call kthread_parkme()
93 * Similar to kthread_should_stop(), but this keeps the thread alive
94 * and in a park position. kthread_unpark() "restarts" the thread and
95 * calls the thread function again.
97 bool kthread_should_park(void)
99 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
101 EXPORT_SYMBOL_GPL(kthread_should_park);
104 * kthread_freezable_should_stop - should this freezable kthread return now?
105 * @was_frozen: optional out parameter, indicates whether %current was frozen
107 * kthread_should_stop() for freezable kthreads, which will enter
108 * refrigerator if necessary. This function is safe from kthread_stop() /
109 * freezer deadlock and freezable kthreads should use this function instead
110 * of calling try_to_freeze() directly.
112 bool kthread_freezable_should_stop(bool *was_frozen)
118 if (unlikely(freezing(current)))
119 frozen = __refrigerator(true);
122 *was_frozen = frozen;
124 return kthread_should_stop();
126 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
129 * kthread_data - return data value specified on kthread creation
130 * @task: kthread task in question
132 * Return the data value specified when kthread @task was created.
133 * The caller is responsible for ensuring the validity of @task when
134 * calling this function.
136 void *kthread_data(struct task_struct *task)
138 return to_kthread(task)->data;
142 * probe_kthread_data - speculative version of kthread_data()
143 * @task: possible kthread task in question
145 * @task could be a kthread task. Return the data value specified when it
146 * was created if accessible. If @task isn't a kthread task or its data is
147 * inaccessible for any reason, %NULL is returned. This function requires
148 * that @task itself is safe to dereference.
150 void *probe_kthread_data(struct task_struct *task)
152 struct kthread *kthread = to_kthread(task);
155 probe_kernel_read(&data, &kthread->data, sizeof(data));
159 static void __kthread_parkme(struct kthread *self)
161 __set_current_state(TASK_PARKED);
162 while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) {
163 if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags))
164 complete(&self->parked);
166 __set_current_state(TASK_PARKED);
168 clear_bit(KTHREAD_IS_PARKED, &self->flags);
169 __set_current_state(TASK_RUNNING);
172 void kthread_parkme(void)
174 __kthread_parkme(to_kthread(current));
176 EXPORT_SYMBOL_GPL(kthread_parkme);
178 static int kthread(void *_create)
180 /* Copy data: it's on kthread's stack */
181 struct kthread_create_info *create = _create;
182 int (*threadfn)(void *data) = create->threadfn;
183 void *data = create->data;
184 struct completion *done;
190 init_completion(&self.exited);
191 init_completion(&self.parked);
192 current->vfork_done = &self.exited;
194 /* If user was SIGKILLed, I release the structure. */
195 done = xchg(&create->done, NULL);
200 /* OK, tell user we're spawned, wait for stop or wakeup */
201 __set_current_state(TASK_UNINTERRUPTIBLE);
202 create->result = current;
208 if (!test_bit(KTHREAD_SHOULD_STOP, &self.flags)) {
209 cgroup_kthread_ready();
210 __kthread_parkme(&self);
211 ret = threadfn(data);
213 /* we can't just return, we must preserve "self" on stack */
217 /* called from do_fork() to get node information for about to be created task */
218 int tsk_fork_get_node(struct task_struct *tsk)
221 if (tsk == kthreadd_task)
222 return tsk->pref_node_fork;
227 static void create_kthread(struct kthread_create_info *create)
232 current->pref_node_fork = create->node;
234 /* We want our own signal handler (we take no signals by default). */
235 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
237 /* If user was SIGKILLed, I release the structure. */
238 struct completion *done = xchg(&create->done, NULL);
244 create->result = ERR_PTR(pid);
250 * kthread_create_on_node - create a kthread.
251 * @threadfn: the function to run until signal_pending(current).
252 * @data: data ptr for @threadfn.
253 * @node: task and thread structures for the thread are allocated on this node
254 * @namefmt: printf-style name for the thread.
256 * Description: This helper function creates and names a kernel
257 * thread. The thread will be stopped: use wake_up_process() to start
258 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
259 * is affine to all CPUs.
261 * If thread is going to be bound on a particular cpu, give its node
262 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
263 * When woken, the thread will run @threadfn() with @data as its
264 * argument. @threadfn() can either call do_exit() directly if it is a
265 * standalone thread for which no one will call kthread_stop(), or
266 * return when 'kthread_should_stop()' is true (which means
267 * kthread_stop() has been called). The return value should be zero
268 * or a negative error number; it will be passed to kthread_stop().
270 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
272 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
273 void *data, int node,
274 const char namefmt[],
277 DECLARE_COMPLETION_ONSTACK(done);
278 struct task_struct *task;
279 struct kthread_create_info *create = kmalloc(sizeof(*create),
283 return ERR_PTR(-ENOMEM);
284 create->threadfn = threadfn;
287 create->done = &done;
289 spin_lock(&kthread_create_lock);
290 list_add_tail(&create->list, &kthread_create_list);
291 spin_unlock(&kthread_create_lock);
293 wake_up_process(kthreadd_task);
295 * Wait for completion in killable state, for I might be chosen by
296 * the OOM killer while kthreadd is trying to allocate memory for
299 if (unlikely(wait_for_completion_killable(&done))) {
301 * If I was SIGKILLed before kthreadd (or new kernel thread)
302 * calls complete(), leave the cleanup of this structure to
305 if (xchg(&create->done, NULL))
306 return ERR_PTR(-EINTR);
308 * kthreadd (or new kernel thread) will call complete()
311 wait_for_completion(&done);
313 task = create->result;
315 static const struct sched_param param = { .sched_priority = 0 };
316 char name[TASK_COMM_LEN];
319 va_start(args, namefmt);
321 * task is already visible to other tasks, so updating
322 * COMM must be protected.
324 vsnprintf(name, sizeof(name), namefmt, args);
325 set_task_comm(task, name);
328 * root may have changed our (kthreadd's) priority or CPU mask.
329 * The kernel thread should not inherit these properties.
331 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
332 set_cpus_allowed_ptr(task, cpu_all_mask);
337 EXPORT_SYMBOL(kthread_create_on_node);
339 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
343 if (!wait_task_inactive(p, state)) {
348 /* It's safe because the task is inactive. */
349 raw_spin_lock_irqsave(&p->pi_lock, flags);
350 do_set_cpus_allowed(p, mask);
351 p->flags |= PF_NO_SETAFFINITY;
352 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
355 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
357 __kthread_bind_mask(p, cpumask_of(cpu), state);
360 void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
362 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
366 * kthread_bind - bind a just-created kthread to a cpu.
367 * @p: thread created by kthread_create().
368 * @cpu: cpu (might not be online, must be possible) for @k to run on.
370 * Description: This function is equivalent to set_cpus_allowed(),
371 * except that @cpu doesn't need to be online, and the thread must be
372 * stopped (i.e., just returned from kthread_create()).
374 void kthread_bind(struct task_struct *p, unsigned int cpu)
376 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
378 EXPORT_SYMBOL(kthread_bind);
381 * kthread_create_on_cpu - Create a cpu bound kthread
382 * @threadfn: the function to run until signal_pending(current).
383 * @data: data ptr for @threadfn.
384 * @cpu: The cpu on which the thread should be bound,
385 * @namefmt: printf-style name for the thread. Format is restricted
386 * to "name.*%u". Code fills in cpu number.
388 * Description: This helper function creates and names a kernel thread
389 * The thread will be woken and put into park mode.
391 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
392 void *data, unsigned int cpu,
395 struct task_struct *p;
397 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
401 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
402 to_kthread(p)->cpu = cpu;
403 /* Park the thread to get it out of TASK_UNINTERRUPTIBLE state */
408 static void __kthread_unpark(struct task_struct *k, struct kthread *kthread)
410 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
412 * We clear the IS_PARKED bit here as we don't wait
413 * until the task has left the park code. So if we'd
414 * park before that happens we'd see the IS_PARKED bit
415 * which might be about to be cleared.
417 if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
418 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
419 __kthread_bind(k, kthread->cpu, TASK_PARKED);
420 wake_up_state(k, TASK_PARKED);
425 * kthread_unpark - unpark a thread created by kthread_create().
426 * @k: thread created by kthread_create().
428 * Sets kthread_should_park() for @k to return false, wakes it, and
429 * waits for it to return. If the thread is marked percpu then its
430 * bound to the cpu again.
432 void kthread_unpark(struct task_struct *k)
434 struct kthread *kthread = to_live_kthread(k);
437 __kthread_unpark(k, kthread);
441 EXPORT_SYMBOL_GPL(kthread_unpark);
444 * kthread_park - park a thread created by kthread_create().
445 * @k: thread created by kthread_create().
447 * Sets kthread_should_park() for @k to return true, wakes it, and
448 * waits for it to return. This can also be called after kthread_create()
449 * instead of calling wake_up_process(): the thread will park without
450 * calling threadfn().
452 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
453 * If called by the kthread itself just the park bit is set.
455 int kthread_park(struct task_struct *k)
457 struct kthread *kthread = to_live_kthread(k);
461 if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
462 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
465 wait_for_completion(&kthread->parked);
473 EXPORT_SYMBOL_GPL(kthread_park);
476 * kthread_stop - stop a thread created by kthread_create().
477 * @k: thread created by kthread_create().
479 * Sets kthread_should_stop() for @k to return true, wakes it, and
480 * waits for it to exit. This can also be called after kthread_create()
481 * instead of calling wake_up_process(): the thread will exit without
482 * calling threadfn().
484 * If threadfn() may call do_exit() itself, the caller must ensure
485 * task_struct can't go away.
487 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
490 int kthread_stop(struct task_struct *k)
492 struct kthread *kthread;
495 trace_sched_kthread_stop(k);
498 kthread = to_live_kthread(k);
500 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
501 __kthread_unpark(k, kthread);
503 wait_for_completion(&kthread->exited);
509 trace_sched_kthread_stop_ret(ret);
512 EXPORT_SYMBOL(kthread_stop);
514 int kthreadd(void *unused)
516 struct task_struct *tsk = current;
518 /* Setup a clean context for our children to inherit. */
519 set_task_comm(tsk, "kthreadd");
521 set_cpus_allowed_ptr(tsk, cpu_all_mask);
522 set_mems_allowed(node_states[N_MEMORY]);
524 current->flags |= PF_NOFREEZE;
525 cgroup_init_kthreadd();
528 set_current_state(TASK_INTERRUPTIBLE);
529 if (list_empty(&kthread_create_list))
531 __set_current_state(TASK_RUNNING);
533 spin_lock(&kthread_create_lock);
534 while (!list_empty(&kthread_create_list)) {
535 struct kthread_create_info *create;
537 create = list_entry(kthread_create_list.next,
538 struct kthread_create_info, list);
539 list_del_init(&create->list);
540 spin_unlock(&kthread_create_lock);
542 create_kthread(create);
544 spin_lock(&kthread_create_lock);
546 spin_unlock(&kthread_create_lock);
552 void __init_kthread_worker(struct kthread_worker *worker,
554 struct lock_class_key *key)
556 spin_lock_init(&worker->lock);
557 lockdep_set_class_and_name(&worker->lock, key, name);
558 INIT_LIST_HEAD(&worker->work_list);
561 EXPORT_SYMBOL_GPL(__init_kthread_worker);
564 * kthread_worker_fn - kthread function to process kthread_worker
565 * @worker_ptr: pointer to initialized kthread_worker
567 * This function can be used as @threadfn to kthread_create() or
568 * kthread_run() with @worker_ptr argument pointing to an initialized
569 * kthread_worker. The started kthread will process work_list until
570 * the it is stopped with kthread_stop(). A kthread can also call
571 * this function directly after extra initialization.
573 * Different kthreads can be used for the same kthread_worker as long
574 * as there's only one kthread attached to it at any given time. A
575 * kthread_worker without an attached kthread simply collects queued
578 int kthread_worker_fn(void *worker_ptr)
580 struct kthread_worker *worker = worker_ptr;
581 struct kthread_work *work;
583 WARN_ON(worker->task);
584 worker->task = current;
586 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
588 if (kthread_should_stop()) {
589 __set_current_state(TASK_RUNNING);
590 spin_lock_irq(&worker->lock);
592 spin_unlock_irq(&worker->lock);
597 spin_lock_irq(&worker->lock);
598 if (!list_empty(&worker->work_list)) {
599 work = list_first_entry(&worker->work_list,
600 struct kthread_work, node);
601 list_del_init(&work->node);
603 worker->current_work = work;
604 spin_unlock_irq(&worker->lock);
607 __set_current_state(TASK_RUNNING);
609 } else if (!freezing(current))
615 EXPORT_SYMBOL_GPL(kthread_worker_fn);
618 * Returns true when the work could not be queued at the moment.
619 * It happens when it is already pending in a worker list
620 * or when it is being cancelled.
622 static inline bool queuing_blocked(struct kthread_worker *worker,
623 struct kthread_work *work)
625 lockdep_assert_held(&worker->lock);
627 return !list_empty(&work->node) || work->canceling;
630 /* insert @work before @pos in @worker */
631 static void insert_kthread_work(struct kthread_worker *worker,
632 struct kthread_work *work,
633 struct list_head *pos)
635 lockdep_assert_held(&worker->lock);
637 list_add_tail(&work->node, pos);
638 work->worker = worker;
639 if (!worker->current_work && likely(worker->task))
640 wake_up_process(worker->task);
644 * queue_kthread_work - queue a kthread_work
645 * @worker: target kthread_worker
646 * @work: kthread_work to queue
648 * Queue @work to work processor @task for async execution. @task
649 * must have been created with kthread_worker_create(). Returns %true
650 * if @work was successfully queued, %false if it was already pending.
652 bool queue_kthread_work(struct kthread_worker *worker,
653 struct kthread_work *work)
658 spin_lock_irqsave(&worker->lock, flags);
659 if (!queuing_blocked(worker, work)) {
660 insert_kthread_work(worker, work, &worker->work_list);
663 spin_unlock_irqrestore(&worker->lock, flags);
666 EXPORT_SYMBOL_GPL(queue_kthread_work);
668 struct kthread_flush_work {
669 struct kthread_work work;
670 struct completion done;
673 static void kthread_flush_work_fn(struct kthread_work *work)
675 struct kthread_flush_work *fwork =
676 container_of(work, struct kthread_flush_work, work);
677 complete(&fwork->done);
681 * flush_kthread_work - flush a kthread_work
682 * @work: work to flush
684 * If @work is queued or executing, wait for it to finish execution.
686 void flush_kthread_work(struct kthread_work *work)
688 struct kthread_flush_work fwork = {
689 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
690 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
692 struct kthread_worker *worker;
696 worker = work->worker;
700 spin_lock_irq(&worker->lock);
701 if (work->worker != worker) {
702 spin_unlock_irq(&worker->lock);
706 if (!list_empty(&work->node))
707 insert_kthread_work(worker, &fwork.work, work->node.next);
708 else if (worker->current_work == work)
709 insert_kthread_work(worker, &fwork.work, worker->work_list.next);
713 spin_unlock_irq(&worker->lock);
716 wait_for_completion(&fwork.done);
718 EXPORT_SYMBOL_GPL(flush_kthread_work);
721 * This function removes the work from the worker queue. Also it makes sure
722 * that it won't get queued later via the delayed work's timer.
724 * The work might still be in use when this function finishes. See the
725 * current_work proceed by the worker.
727 * Return: %true if @work was pending and successfully canceled,
728 * %false if @work was not pending
730 static bool __kthread_cancel_work(struct kthread_work *work,
731 unsigned long *flags)
734 * Try to remove the work from a worker list. It might either
735 * be from worker->work_list or from worker->delayed_work_list.
737 if (!list_empty(&work->node)) {
738 list_del_init(&work->node);
745 static bool __kthread_cancel_work_sync(struct kthread_work *work)
747 struct kthread_worker *worker = work->worker;
754 spin_lock_irqsave(&worker->lock, flags);
755 /* Work must not be used with >1 worker, see kthread_queue_work(). */
756 WARN_ON_ONCE(work->worker != worker);
758 ret = __kthread_cancel_work(work, &flags);
760 if (worker->current_work != work)
764 * The work is in progress and we need to wait with the lock released.
765 * In the meantime, block any queuing by setting the canceling counter.
768 spin_unlock_irqrestore(&worker->lock, flags);
769 flush_kthread_work(work);
770 spin_lock_irqsave(&worker->lock, flags);
774 spin_unlock_irqrestore(&worker->lock, flags);
780 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
781 * @work: the kthread work to cancel
783 * Cancel @work and wait for its execution to finish. This function
784 * can be used even if the work re-queues itself. On return from this
785 * function, @work is guaranteed to be not pending or executing on any CPU.
787 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
788 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
790 * The caller must ensure that the worker on which @work was last
791 * queued can't be destroyed before this function returns.
793 * Return: %true if @work was pending, %false otherwise.
795 bool kthread_cancel_work_sync(struct kthread_work *work)
797 return __kthread_cancel_work_sync(work);
799 EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
802 * flush_kthread_worker - flush all current works on a kthread_worker
803 * @worker: worker to flush
805 * Wait until all currently executing or pending works on @worker are
808 void flush_kthread_worker(struct kthread_worker *worker)
810 struct kthread_flush_work fwork = {
811 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
812 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
815 queue_kthread_work(worker, &fwork.work);
816 wait_for_completion(&fwork.done);
818 EXPORT_SYMBOL_GPL(flush_kthread_worker);