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 <trace/events/sched.h>
23 static DEFINE_SPINLOCK(kthread_create_lock);
24 static LIST_HEAD(kthread_create_list);
25 struct task_struct *kthreadd_task;
27 struct kthread_create_info
29 /* Information passed to kthread() from kthreadd. */
30 int (*threadfn)(void *data);
34 /* Result passed back to kthread_create() from kthreadd. */
35 struct task_struct *result;
36 struct completion *done;
38 struct list_head list;
45 struct completion parked;
46 struct completion exited;
50 KTHREAD_IS_PER_CPU = 0,
56 #define __to_kthread(vfork) \
57 container_of(vfork, struct kthread, exited)
59 static inline struct kthread *to_kthread(struct task_struct *k)
61 return __to_kthread(k->vfork_done);
64 static struct kthread *to_live_kthread(struct task_struct *k)
66 struct completion *vfork = ACCESS_ONCE(k->vfork_done);
68 return __to_kthread(vfork);
73 * kthread_should_stop - should this kthread return now?
75 * When someone calls kthread_stop() on your kthread, it will be woken
76 * and this will return true. You should then return, and your return
77 * value will be passed through to kthread_stop().
79 bool kthread_should_stop(void)
81 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
83 EXPORT_SYMBOL(kthread_should_stop);
86 * kthread_should_park - should this kthread park now?
88 * When someone calls kthread_park() on your kthread, it will be woken
89 * and this will return true. You should then do the necessary
90 * cleanup and call kthread_parkme()
92 * Similar to kthread_should_stop(), but this keeps the thread alive
93 * and in a park position. kthread_unpark() "restarts" the thread and
94 * calls the thread function again.
96 bool kthread_should_park(void)
98 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
100 EXPORT_SYMBOL_GPL(kthread_should_park);
103 * kthread_freezable_should_stop - should this freezable kthread return now?
104 * @was_frozen: optional out parameter, indicates whether %current was frozen
106 * kthread_should_stop() for freezable kthreads, which will enter
107 * refrigerator if necessary. This function is safe from kthread_stop() /
108 * freezer deadlock and freezable kthreads should use this function instead
109 * of calling try_to_freeze() directly.
111 bool kthread_freezable_should_stop(bool *was_frozen)
117 if (unlikely(freezing(current)))
118 frozen = __refrigerator(true);
121 *was_frozen = frozen;
123 return kthread_should_stop();
125 EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
128 * kthread_data - return data value specified on kthread creation
129 * @task: kthread task in question
131 * Return the data value specified when kthread @task was created.
132 * The caller is responsible for ensuring the validity of @task when
133 * calling this function.
135 void *kthread_data(struct task_struct *task)
137 return to_kthread(task)->data;
141 * probe_kthread_data - speculative version of kthread_data()
142 * @task: possible kthread task in question
144 * @task could be a kthread task. Return the data value specified when it
145 * was created if accessible. If @task isn't a kthread task or its data is
146 * inaccessible for any reason, %NULL is returned. This function requires
147 * that @task itself is safe to dereference.
149 void *probe_kthread_data(struct task_struct *task)
151 struct kthread *kthread = to_kthread(task);
154 probe_kernel_read(&data, &kthread->data, sizeof(data));
158 static void __kthread_parkme(struct kthread *self)
160 __set_current_state(TASK_PARKED);
161 while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) {
162 if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags))
163 complete(&self->parked);
165 __set_current_state(TASK_PARKED);
167 clear_bit(KTHREAD_IS_PARKED, &self->flags);
168 __set_current_state(TASK_RUNNING);
171 void kthread_parkme(void)
173 __kthread_parkme(to_kthread(current));
175 EXPORT_SYMBOL_GPL(kthread_parkme);
177 static int kthread(void *_create)
179 /* Copy data: it's on kthread's stack */
180 struct kthread_create_info *create = _create;
181 int (*threadfn)(void *data) = create->threadfn;
182 void *data = create->data;
183 struct completion *done;
189 init_completion(&self.exited);
190 init_completion(&self.parked);
191 current->vfork_done = &self.exited;
193 /* If user was SIGKILLed, I release the structure. */
194 done = xchg(&create->done, NULL);
199 /* OK, tell user we're spawned, wait for stop or wakeup */
200 __set_current_state(TASK_UNINTERRUPTIBLE);
201 create->result = current;
207 if (!test_bit(KTHREAD_SHOULD_STOP, &self.flags)) {
208 __kthread_parkme(&self);
209 ret = threadfn(data);
211 /* we can't just return, we must preserve "self" on stack */
215 /* called from do_fork() to get node information for about to be created task */
216 int tsk_fork_get_node(struct task_struct *tsk)
219 if (tsk == kthreadd_task)
220 return tsk->pref_node_fork;
225 static void create_kthread(struct kthread_create_info *create)
230 current->pref_node_fork = create->node;
232 /* We want our own signal handler (we take no signals by default). */
233 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
235 /* If user was SIGKILLed, I release the structure. */
236 struct completion *done = xchg(&create->done, NULL);
242 create->result = ERR_PTR(pid);
248 * kthread_create_on_node - create a kthread.
249 * @threadfn: the function to run until signal_pending(current).
250 * @data: data ptr for @threadfn.
251 * @node: memory node number.
252 * @namefmt: printf-style name for the thread.
254 * Description: This helper function creates and names a kernel
255 * thread. The thread will be stopped: use wake_up_process() to start
256 * it. See also kthread_run().
258 * If thread is going to be bound on a particular cpu, give its node
259 * in @node, to get NUMA affinity for kthread stack, or else give -1.
260 * When woken, the thread will run @threadfn() with @data as its
261 * argument. @threadfn() can either call do_exit() directly if it is a
262 * standalone thread for which no one will call kthread_stop(), or
263 * return when 'kthread_should_stop()' is true (which means
264 * kthread_stop() has been called). The return value should be zero
265 * or a negative error number; it will be passed to kthread_stop().
267 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
269 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
270 void *data, int node,
271 const char namefmt[],
274 DECLARE_COMPLETION_ONSTACK(done);
275 struct task_struct *task;
276 struct kthread_create_info *create = kmalloc(sizeof(*create),
280 return ERR_PTR(-ENOMEM);
281 create->threadfn = threadfn;
284 create->done = &done;
286 spin_lock(&kthread_create_lock);
287 list_add_tail(&create->list, &kthread_create_list);
288 spin_unlock(&kthread_create_lock);
290 wake_up_process(kthreadd_task);
292 * Wait for completion in killable state, for I might be chosen by
293 * the OOM killer while kthreadd is trying to allocate memory for
296 if (unlikely(wait_for_completion_killable(&done))) {
298 * If I was SIGKILLed before kthreadd (or new kernel thread)
299 * calls complete(), leave the cleanup of this structure to
302 if (xchg(&create->done, NULL))
303 return ERR_PTR(-EINTR);
305 * kthreadd (or new kernel thread) will call complete()
308 wait_for_completion(&done);
310 task = create->result;
312 static const struct sched_param param = { .sched_priority = 0 };
315 va_start(args, namefmt);
316 vsnprintf(task->comm, sizeof(task->comm), namefmt, args);
319 * root may have changed our (kthreadd's) priority or CPU mask.
320 * The kernel thread should not inherit these properties.
322 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
323 set_cpus_allowed_ptr(task, cpu_all_mask);
328 EXPORT_SYMBOL(kthread_create_on_node);
330 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
334 if (!wait_task_inactive(p, state)) {
339 /* It's safe because the task is inactive. */
340 raw_spin_lock_irqsave(&p->pi_lock, flags);
341 do_set_cpus_allowed(p, mask);
342 p->flags |= PF_NO_SETAFFINITY;
343 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
346 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
348 __kthread_bind_mask(p, cpumask_of(cpu), state);
351 void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
353 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
357 * kthread_bind - bind a just-created kthread to a cpu.
358 * @p: thread created by kthread_create().
359 * @cpu: cpu (might not be online, must be possible) for @k to run on.
361 * Description: This function is equivalent to set_cpus_allowed(),
362 * except that @cpu doesn't need to be online, and the thread must be
363 * stopped (i.e., just returned from kthread_create()).
365 void kthread_bind(struct task_struct *p, unsigned int cpu)
367 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
369 EXPORT_SYMBOL(kthread_bind);
372 * kthread_create_on_cpu - Create a cpu bound kthread
373 * @threadfn: the function to run until signal_pending(current).
374 * @data: data ptr for @threadfn.
375 * @cpu: The cpu on which the thread should be bound,
376 * @namefmt: printf-style name for the thread. Format is restricted
377 * to "name.*%u". Code fills in cpu number.
379 * Description: This helper function creates and names a kernel thread
380 * The thread will be woken and put into park mode.
382 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
383 void *data, unsigned int cpu,
386 struct task_struct *p;
388 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
392 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
393 to_kthread(p)->cpu = cpu;
394 /* Park the thread to get it out of TASK_UNINTERRUPTIBLE state */
399 static void __kthread_unpark(struct task_struct *k, struct kthread *kthread)
401 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
403 * We clear the IS_PARKED bit here as we don't wait
404 * until the task has left the park code. So if we'd
405 * park before that happens we'd see the IS_PARKED bit
406 * which might be about to be cleared.
408 if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
409 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
410 __kthread_bind(k, kthread->cpu, TASK_PARKED);
411 wake_up_state(k, TASK_PARKED);
416 * kthread_unpark - unpark a thread created by kthread_create().
417 * @k: thread created by kthread_create().
419 * Sets kthread_should_park() for @k to return false, wakes it, and
420 * waits for it to return. If the thread is marked percpu then its
421 * bound to the cpu again.
423 void kthread_unpark(struct task_struct *k)
425 struct kthread *kthread = to_live_kthread(k);
428 __kthread_unpark(k, kthread);
430 EXPORT_SYMBOL_GPL(kthread_unpark);
433 * kthread_park - park a thread created by kthread_create().
434 * @k: thread created by kthread_create().
436 * Sets kthread_should_park() for @k to return true, wakes it, and
437 * waits for it to return. This can also be called after kthread_create()
438 * instead of calling wake_up_process(): the thread will park without
439 * calling threadfn().
441 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
442 * If called by the kthread itself just the park bit is set.
444 int kthread_park(struct task_struct *k)
446 struct kthread *kthread = to_live_kthread(k);
450 if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
451 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
454 wait_for_completion(&kthread->parked);
461 EXPORT_SYMBOL_GPL(kthread_park);
464 * kthread_stop - stop a thread created by kthread_create().
465 * @k: thread created by kthread_create().
467 * Sets kthread_should_stop() for @k to return true, wakes it, and
468 * waits for it to exit. This can also be called after kthread_create()
469 * instead of calling wake_up_process(): the thread will exit without
470 * calling threadfn().
472 * If threadfn() may call do_exit() itself, the caller must ensure
473 * task_struct can't go away.
475 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
478 int kthread_stop(struct task_struct *k)
480 struct kthread *kthread;
483 trace_sched_kthread_stop(k);
486 kthread = to_live_kthread(k);
488 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
489 __kthread_unpark(k, kthread);
491 wait_for_completion(&kthread->exited);
496 trace_sched_kthread_stop_ret(ret);
499 EXPORT_SYMBOL(kthread_stop);
501 int kthreadd(void *unused)
503 struct task_struct *tsk = current;
505 /* Setup a clean context for our children to inherit. */
506 set_task_comm(tsk, "kthreadd");
508 set_cpus_allowed_ptr(tsk, cpu_all_mask);
509 set_mems_allowed(node_states[N_MEMORY]);
511 current->flags |= PF_NOFREEZE;
514 set_current_state(TASK_INTERRUPTIBLE);
515 if (list_empty(&kthread_create_list))
517 __set_current_state(TASK_RUNNING);
519 spin_lock(&kthread_create_lock);
520 while (!list_empty(&kthread_create_list)) {
521 struct kthread_create_info *create;
523 create = list_entry(kthread_create_list.next,
524 struct kthread_create_info, list);
525 list_del_init(&create->list);
526 spin_unlock(&kthread_create_lock);
528 create_kthread(create);
530 spin_lock(&kthread_create_lock);
532 spin_unlock(&kthread_create_lock);
538 void __init_kthread_worker(struct kthread_worker *worker,
540 struct lock_class_key *key)
542 spin_lock_init(&worker->lock);
543 lockdep_set_class_and_name(&worker->lock, key, name);
544 INIT_LIST_HEAD(&worker->work_list);
547 EXPORT_SYMBOL_GPL(__init_kthread_worker);
550 * kthread_worker_fn - kthread function to process kthread_worker
551 * @worker_ptr: pointer to initialized kthread_worker
553 * This function can be used as @threadfn to kthread_create() or
554 * kthread_run() with @worker_ptr argument pointing to an initialized
555 * kthread_worker. The started kthread will process work_list until
556 * the it is stopped with kthread_stop(). A kthread can also call
557 * this function directly after extra initialization.
559 * Different kthreads can be used for the same kthread_worker as long
560 * as there's only one kthread attached to it at any given time. A
561 * kthread_worker without an attached kthread simply collects queued
564 int kthread_worker_fn(void *worker_ptr)
566 struct kthread_worker *worker = worker_ptr;
567 struct kthread_work *work;
569 WARN_ON(worker->task);
570 worker->task = current;
572 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
574 if (kthread_should_stop()) {
575 __set_current_state(TASK_RUNNING);
576 spin_lock_irq(&worker->lock);
578 spin_unlock_irq(&worker->lock);
583 spin_lock_irq(&worker->lock);
584 if (!list_empty(&worker->work_list)) {
585 work = list_first_entry(&worker->work_list,
586 struct kthread_work, node);
587 list_del_init(&work->node);
589 worker->current_work = work;
590 spin_unlock_irq(&worker->lock);
593 __set_current_state(TASK_RUNNING);
595 } else if (!freezing(current))
601 EXPORT_SYMBOL_GPL(kthread_worker_fn);
603 /* insert @work before @pos in @worker */
604 static void insert_kthread_work(struct kthread_worker *worker,
605 struct kthread_work *work,
606 struct list_head *pos)
608 lockdep_assert_held(&worker->lock);
610 list_add_tail(&work->node, pos);
611 work->worker = worker;
612 if (!worker->current_work && likely(worker->task))
613 wake_up_process(worker->task);
617 * queue_kthread_work - queue a kthread_work
618 * @worker: target kthread_worker
619 * @work: kthread_work to queue
621 * Queue @work to work processor @task for async execution. @task
622 * must have been created with kthread_worker_create(). Returns %true
623 * if @work was successfully queued, %false if it was already pending.
625 bool queue_kthread_work(struct kthread_worker *worker,
626 struct kthread_work *work)
631 spin_lock_irqsave(&worker->lock, flags);
632 if (list_empty(&work->node)) {
633 insert_kthread_work(worker, work, &worker->work_list);
636 spin_unlock_irqrestore(&worker->lock, flags);
639 EXPORT_SYMBOL_GPL(queue_kthread_work);
641 struct kthread_flush_work {
642 struct kthread_work work;
643 struct completion done;
646 static void kthread_flush_work_fn(struct kthread_work *work)
648 struct kthread_flush_work *fwork =
649 container_of(work, struct kthread_flush_work, work);
650 complete(&fwork->done);
654 * flush_kthread_work - flush a kthread_work
655 * @work: work to flush
657 * If @work is queued or executing, wait for it to finish execution.
659 void flush_kthread_work(struct kthread_work *work)
661 struct kthread_flush_work fwork = {
662 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
663 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
665 struct kthread_worker *worker;
669 worker = work->worker;
673 spin_lock_irq(&worker->lock);
674 if (work->worker != worker) {
675 spin_unlock_irq(&worker->lock);
679 if (!list_empty(&work->node))
680 insert_kthread_work(worker, &fwork.work, work->node.next);
681 else if (worker->current_work == work)
682 insert_kthread_work(worker, &fwork.work, worker->work_list.next);
686 spin_unlock_irq(&worker->lock);
689 wait_for_completion(&fwork.done);
691 EXPORT_SYMBOL_GPL(flush_kthread_work);
694 * flush_kthread_worker - flush all current works on a kthread_worker
695 * @worker: worker to flush
697 * Wait until all currently executing or pending works on @worker are
700 void flush_kthread_worker(struct kthread_worker *worker)
702 struct kthread_flush_work fwork = {
703 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
704 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
707 queue_kthread_work(worker, &fwork.work);
708 wait_for_completion(&fwork.done);
710 EXPORT_SYMBOL_GPL(flush_kthread_worker);