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);
67 if (likely(vfork) && try_get_task_stack(k))
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 * kthread_probe_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 *kthread_probe_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);
247 static struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
248 void *data, int node,
249 const char namefmt[],
252 DECLARE_COMPLETION_ONSTACK(done);
253 struct task_struct *task;
254 struct kthread_create_info *create = kmalloc(sizeof(*create),
258 return ERR_PTR(-ENOMEM);
259 create->threadfn = threadfn;
262 create->done = &done;
264 spin_lock(&kthread_create_lock);
265 list_add_tail(&create->list, &kthread_create_list);
266 spin_unlock(&kthread_create_lock);
268 wake_up_process(kthreadd_task);
270 * Wait for completion in killable state, for I might be chosen by
271 * the OOM killer while kthreadd is trying to allocate memory for
274 if (unlikely(wait_for_completion_killable(&done))) {
276 * If I was SIGKILLed before kthreadd (or new kernel thread)
277 * calls complete(), leave the cleanup of this structure to
280 if (xchg(&create->done, NULL))
281 return ERR_PTR(-EINTR);
283 * kthreadd (or new kernel thread) will call complete()
286 wait_for_completion(&done);
288 task = create->result;
290 static const struct sched_param param = { .sched_priority = 0 };
292 vsnprintf(task->comm, sizeof(task->comm), namefmt, args);
294 * root may have changed our (kthreadd's) priority or CPU mask.
295 * The kernel thread should not inherit these properties.
297 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
298 set_cpus_allowed_ptr(task, cpu_all_mask);
305 * kthread_create_on_node - create a kthread.
306 * @threadfn: the function to run until signal_pending(current).
307 * @data: data ptr for @threadfn.
308 * @node: task and thread structures for the thread are allocated on this node
309 * @namefmt: printf-style name for the thread.
311 * Description: This helper function creates and names a kernel
312 * thread. The thread will be stopped: use wake_up_process() to start
313 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
314 * is affine to all CPUs.
316 * If thread is going to be bound on a particular cpu, give its node
317 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
318 * When woken, the thread will run @threadfn() with @data as its
319 * argument. @threadfn() can either call do_exit() directly if it is a
320 * standalone thread for which no one will call kthread_stop(), or
321 * return when 'kthread_should_stop()' is true (which means
322 * kthread_stop() has been called). The return value should be zero
323 * or a negative error number; it will be passed to kthread_stop().
325 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
327 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
328 void *data, int node,
329 const char namefmt[],
332 struct task_struct *task;
335 va_start(args, namefmt);
336 task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
341 EXPORT_SYMBOL(kthread_create_on_node);
343 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
347 if (!wait_task_inactive(p, state)) {
352 /* It's safe because the task is inactive. */
353 raw_spin_lock_irqsave(&p->pi_lock, flags);
354 do_set_cpus_allowed(p, mask);
355 p->flags |= PF_NO_SETAFFINITY;
356 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
359 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
361 __kthread_bind_mask(p, cpumask_of(cpu), state);
364 void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
366 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
370 * kthread_bind - bind a just-created kthread to a cpu.
371 * @p: thread created by kthread_create().
372 * @cpu: cpu (might not be online, must be possible) for @k to run on.
374 * Description: This function is equivalent to set_cpus_allowed(),
375 * except that @cpu doesn't need to be online, and the thread must be
376 * stopped (i.e., just returned from kthread_create()).
378 void kthread_bind(struct task_struct *p, unsigned int cpu)
380 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
382 EXPORT_SYMBOL(kthread_bind);
385 * kthread_create_on_cpu - Create a cpu bound kthread
386 * @threadfn: the function to run until signal_pending(current).
387 * @data: data ptr for @threadfn.
388 * @cpu: The cpu on which the thread should be bound,
389 * @namefmt: printf-style name for the thread. Format is restricted
390 * to "name.*%u". Code fills in cpu number.
392 * Description: This helper function creates and names a kernel thread
393 * The thread will be woken and put into park mode.
395 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
396 void *data, unsigned int cpu,
399 struct task_struct *p;
401 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
405 kthread_bind(p, cpu);
406 /* CPU hotplug need to bind once again when unparking the thread. */
407 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
408 to_kthread(p)->cpu = cpu;
412 static void __kthread_unpark(struct task_struct *k, struct kthread *kthread)
414 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
416 * We clear the IS_PARKED bit here as we don't wait
417 * until the task has left the park code. So if we'd
418 * park before that happens we'd see the IS_PARKED bit
419 * which might be about to be cleared.
421 if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
423 * Newly created kthread was parked when the CPU was offline.
424 * The binding was lost and we need to set it again.
426 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
427 __kthread_bind(k, kthread->cpu, TASK_PARKED);
428 wake_up_state(k, TASK_PARKED);
433 * kthread_unpark - unpark a thread created by kthread_create().
434 * @k: thread created by kthread_create().
436 * Sets kthread_should_park() for @k to return false, wakes it, and
437 * waits for it to return. If the thread is marked percpu then its
438 * bound to the cpu again.
440 void kthread_unpark(struct task_struct *k)
442 struct kthread *kthread = to_live_kthread(k);
445 __kthread_unpark(k, kthread);
449 EXPORT_SYMBOL_GPL(kthread_unpark);
452 * kthread_park - park a thread created by kthread_create().
453 * @k: thread created by kthread_create().
455 * Sets kthread_should_park() for @k to return true, wakes it, and
456 * waits for it to return. This can also be called after kthread_create()
457 * instead of calling wake_up_process(): the thread will park without
458 * calling threadfn().
460 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
461 * If called by the kthread itself just the park bit is set.
463 int kthread_park(struct task_struct *k)
465 struct kthread *kthread = to_live_kthread(k);
469 if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
470 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
473 wait_for_completion(&kthread->parked);
481 EXPORT_SYMBOL_GPL(kthread_park);
484 * kthread_stop - stop a thread created by kthread_create().
485 * @k: thread created by kthread_create().
487 * Sets kthread_should_stop() for @k to return true, wakes it, and
488 * waits for it to exit. This can also be called after kthread_create()
489 * instead of calling wake_up_process(): the thread will exit without
490 * calling threadfn().
492 * If threadfn() may call do_exit() itself, the caller must ensure
493 * task_struct can't go away.
495 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
498 int kthread_stop(struct task_struct *k)
500 struct kthread *kthread;
503 trace_sched_kthread_stop(k);
506 kthread = to_live_kthread(k);
508 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
509 __kthread_unpark(k, kthread);
511 wait_for_completion(&kthread->exited);
517 trace_sched_kthread_stop_ret(ret);
520 EXPORT_SYMBOL(kthread_stop);
522 int kthreadd(void *unused)
524 struct task_struct *tsk = current;
526 /* Setup a clean context for our children to inherit. */
527 set_task_comm(tsk, "kthreadd");
529 set_cpus_allowed_ptr(tsk, cpu_all_mask);
530 set_mems_allowed(node_states[N_MEMORY]);
532 current->flags |= PF_NOFREEZE;
535 set_current_state(TASK_INTERRUPTIBLE);
536 if (list_empty(&kthread_create_list))
538 __set_current_state(TASK_RUNNING);
540 spin_lock(&kthread_create_lock);
541 while (!list_empty(&kthread_create_list)) {
542 struct kthread_create_info *create;
544 create = list_entry(kthread_create_list.next,
545 struct kthread_create_info, list);
546 list_del_init(&create->list);
547 spin_unlock(&kthread_create_lock);
549 create_kthread(create);
551 spin_lock(&kthread_create_lock);
553 spin_unlock(&kthread_create_lock);
559 void __kthread_init_worker(struct kthread_worker *worker,
561 struct lock_class_key *key)
563 spin_lock_init(&worker->lock);
564 lockdep_set_class_and_name(&worker->lock, key, name);
565 INIT_LIST_HEAD(&worker->work_list);
568 EXPORT_SYMBOL_GPL(__kthread_init_worker);
571 * kthread_worker_fn - kthread function to process kthread_worker
572 * @worker_ptr: pointer to initialized kthread_worker
574 * This function can be used as @threadfn to kthread_create() or
575 * kthread_run() with @worker_ptr argument pointing to an initialized
576 * kthread_worker. The started kthread will process work_list until
577 * the it is stopped with kthread_stop(). A kthread can also call
578 * this function directly after extra initialization.
580 * Different kthreads can be used for the same kthread_worker as long
581 * as there's only one kthread attached to it at any given time. A
582 * kthread_worker without an attached kthread simply collects queued
585 int kthread_worker_fn(void *worker_ptr)
587 struct kthread_worker *worker = worker_ptr;
588 struct kthread_work *work;
590 WARN_ON(worker->task);
591 worker->task = current;
593 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
595 if (kthread_should_stop()) {
596 __set_current_state(TASK_RUNNING);
597 spin_lock_irq(&worker->lock);
599 spin_unlock_irq(&worker->lock);
604 spin_lock_irq(&worker->lock);
605 if (!list_empty(&worker->work_list)) {
606 work = list_first_entry(&worker->work_list,
607 struct kthread_work, node);
608 list_del_init(&work->node);
610 worker->current_work = work;
611 spin_unlock_irq(&worker->lock);
614 __set_current_state(TASK_RUNNING);
616 } else if (!freezing(current))
622 EXPORT_SYMBOL_GPL(kthread_worker_fn);
624 /* insert @work before @pos in @worker */
625 static void kthread_insert_work(struct kthread_worker *worker,
626 struct kthread_work *work,
627 struct list_head *pos)
629 lockdep_assert_held(&worker->lock);
631 list_add_tail(&work->node, pos);
632 work->worker = worker;
633 if (!worker->current_work && likely(worker->task))
634 wake_up_process(worker->task);
638 * kthread_queue_work - queue a kthread_work
639 * @worker: target kthread_worker
640 * @work: kthread_work to queue
642 * Queue @work to work processor @task for async execution. @task
643 * must have been created with kthread_worker_create(). Returns %true
644 * if @work was successfully queued, %false if it was already pending.
646 bool kthread_queue_work(struct kthread_worker *worker,
647 struct kthread_work *work)
652 spin_lock_irqsave(&worker->lock, flags);
653 if (list_empty(&work->node)) {
654 kthread_insert_work(worker, work, &worker->work_list);
657 spin_unlock_irqrestore(&worker->lock, flags);
660 EXPORT_SYMBOL_GPL(kthread_queue_work);
662 struct kthread_flush_work {
663 struct kthread_work work;
664 struct completion done;
667 static void kthread_flush_work_fn(struct kthread_work *work)
669 struct kthread_flush_work *fwork =
670 container_of(work, struct kthread_flush_work, work);
671 complete(&fwork->done);
675 * kthread_flush_work - flush a kthread_work
676 * @work: work to flush
678 * If @work is queued or executing, wait for it to finish execution.
680 void kthread_flush_work(struct kthread_work *work)
682 struct kthread_flush_work fwork = {
683 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
684 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
686 struct kthread_worker *worker;
690 worker = work->worker;
694 spin_lock_irq(&worker->lock);
695 if (work->worker != worker) {
696 spin_unlock_irq(&worker->lock);
700 if (!list_empty(&work->node))
701 kthread_insert_work(worker, &fwork.work, work->node.next);
702 else if (worker->current_work == work)
703 kthread_insert_work(worker, &fwork.work,
704 worker->work_list.next);
708 spin_unlock_irq(&worker->lock);
711 wait_for_completion(&fwork.done);
713 EXPORT_SYMBOL_GPL(kthread_flush_work);
716 * kthread_flush_worker - flush all current works on a kthread_worker
717 * @worker: worker to flush
719 * Wait until all currently executing or pending works on @worker are
722 void kthread_flush_worker(struct kthread_worker *worker)
724 struct kthread_flush_work fwork = {
725 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
726 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
729 kthread_queue_work(worker, &fwork.work);
730 wait_for_completion(&fwork.done);
732 EXPORT_SYMBOL_GPL(kthread_flush_worker);