projects/linux·blob v4.2-rc8 · refs

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1/* Kernel thread helper functions.
2 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
3 *
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,
6 * etc.).
7 */
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>
22
23static DEFINE_SPINLOCK(kthread_create_lock);
24static LIST_HEAD(kthread_create_list);
25struct task_struct *kthreadd_task;
26
27struct kthread_create_info
28{
29 /* Information passed to kthread() from kthreadd. */
30 int (*threadfn)(void *data);
31 void *data;
32 int node;
33
34 /* Result passed back to kthread_create() from kthreadd. */
35 struct task_struct *result;
36 struct completion *done;
37
38 struct list_head list;
39};
40
41struct kthread {
42 unsigned long flags;
43 unsigned int cpu;
44 void *data;
45 struct completion parked;
46 struct completion exited;
47};
48
49enum KTHREAD_BITS {
50 KTHREAD_IS_PER_CPU = 0,
51 KTHREAD_SHOULD_STOP,
52 KTHREAD_SHOULD_PARK,
53 KTHREAD_IS_PARKED,
54};
55
56#define __to_kthread(vfork) \
57 container_of(vfork, struct kthread, exited)
58
59static inline struct kthread *to_kthread(struct task_struct *k)
60{
61 return __to_kthread(k->vfork_done);
62}
63
64static struct kthread *to_live_kthread(struct task_struct *k)
65{
66 struct completion *vfork = ACCESS_ONCE(k->vfork_done);
67 if (likely(vfork))
68 return __to_kthread(vfork);
69 return NULL;
70}
71
72/**
73 * kthread_should_stop - should this kthread return now?
74 *
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().
78 */
79bool kthread_should_stop(void)
80{
81 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
82}
83EXPORT_SYMBOL(kthread_should_stop);
84
85/**
86 * kthread_should_park - should this kthread park now?
87 *
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()
91 *
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.
95 */
96bool kthread_should_park(void)
97{
98 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
99}
100EXPORT_SYMBOL_GPL(kthread_should_park);
101
102/**
103 * kthread_freezable_should_stop - should this freezable kthread return now?
104 * @was_frozen: optional out parameter, indicates whether %current was frozen
105 *
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.
110 */
111bool kthread_freezable_should_stop(bool *was_frozen)
112{
113 bool frozen = false;
114
115 might_sleep();
116
117 if (unlikely(freezing(current)))
118 frozen = __refrigerator(true);
119
120 if (was_frozen)
121 *was_frozen = frozen;
122
123 return kthread_should_stop();
124}
125EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
126
127/**
128 * kthread_data - return data value specified on kthread creation
129 * @task: kthread task in question
130 *
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.
134 */
135void *kthread_data(struct task_struct *task)
136{
137 return to_kthread(task)->data;
138}
139
140/**
141 * probe_kthread_data - speculative version of kthread_data()
142 * @task: possible kthread task in question
143 *
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.
148 */
149void *probe_kthread_data(struct task_struct *task)
150{
151 struct kthread *kthread = to_kthread(task);
152 void *data = NULL;
153
154 probe_kernel_read(&data, &kthread->data, sizeof(data));
155 return data;
156}
157
158static void __kthread_parkme(struct kthread *self)
159{
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);
164 schedule();
165 __set_current_state(TASK_PARKED);
166 }
167 clear_bit(KTHREAD_IS_PARKED, &self->flags);
168 __set_current_state(TASK_RUNNING);
169}
170
171void kthread_parkme(void)
172{
173 __kthread_parkme(to_kthread(current));
174}
175EXPORT_SYMBOL_GPL(kthread_parkme);
176
177static int kthread(void *_create)
178{
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;
184 struct kthread self;
185 int ret;
186
187 self.flags = 0;
188 self.data = data;
189 init_completion(&self.exited);
190 init_completion(&self.parked);
191 current->vfork_done = &self.exited;
192
193 /* If user was SIGKILLed, I release the structure. */
194 done = xchg(&create->done, NULL);
195 if (!done) {
196 kfree(create);
197 do_exit(-EINTR);
198 }
199 /* OK, tell user we're spawned, wait for stop or wakeup */
200 __set_current_state(TASK_UNINTERRUPTIBLE);
201 create->result = current;
202 complete(done);
203 schedule();
204
205 ret = -EINTR;
206
207 if (!test_bit(KTHREAD_SHOULD_STOP, &self.flags)) {
208 __kthread_parkme(&self);
209 ret = threadfn(data);
210 }
211 /* we can't just return, we must preserve "self" on stack */
212 do_exit(ret);
213}
214
215/* called from do_fork() to get node information for about to be created task */
216int tsk_fork_get_node(struct task_struct *tsk)
217{
218#ifdef CONFIG_NUMA
219 if (tsk == kthreadd_task)
220 return tsk->pref_node_fork;
221#endif
222 return NUMA_NO_NODE;
223}
224
225static void create_kthread(struct kthread_create_info *create)
226{
227 int pid;
228
229#ifdef CONFIG_NUMA
230 current->pref_node_fork = create->node;
231#endif
232 /* We want our own signal handler (we take no signals by default). */
233 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
234 if (pid < 0) {
235 /* If user was SIGKILLed, I release the structure. */
236 struct completion *done = xchg(&create->done, NULL);
237
238 if (!done) {
239 kfree(create);
240 return;
241 }
242 create->result = ERR_PTR(pid);
243 complete(done);
244 }
245}
246
247/**
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.
253 *
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().
257 *
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().
266 *
267 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
268 */
269struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
270 void *data, int node,
271 const char namefmt[],
272 ...)
273{
274 DECLARE_COMPLETION_ONSTACK(done);
275 struct task_struct *task;
276 struct kthread_create_info *create = kmalloc(sizeof(*create),
277 GFP_KERNEL);
278
279 if (!create)
280 return ERR_PTR(-ENOMEM);
281 create->threadfn = threadfn;
282 create->data = data;
283 create->node = node;
284 create->done = &done;
285
286 spin_lock(&kthread_create_lock);
287 list_add_tail(&create->list, &kthread_create_list);
288 spin_unlock(&kthread_create_lock);
289
290 wake_up_process(kthreadd_task);
291 /*
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
294 * new kernel thread.
295 */
296 if (unlikely(wait_for_completion_killable(&done))) {
297 /*
298 * If I was SIGKILLed before kthreadd (or new kernel thread)
299 * calls complete(), leave the cleanup of this structure to
300 * that thread.
301 */
302 if (xchg(&create->done, NULL))
303 return ERR_PTR(-EINTR);
304 /*
305 * kthreadd (or new kernel thread) will call complete()
306 * shortly.
307 */
308 wait_for_completion(&done);
309 }
310 task = create->result;
311 if (!IS_ERR(task)) {
312 static const struct sched_param param = { .sched_priority = 0 };
313 va_list args;
314
315 va_start(args, namefmt);
316 vsnprintf(task->comm, sizeof(task->comm), namefmt, args);
317 va_end(args);
318 /*
319 * root may have changed our (kthreadd's) priority or CPU mask.
320 * The kernel thread should not inherit these properties.
321 */
322 sched_setscheduler_nocheck(task, SCHED_NORMAL, &param);
323 set_cpus_allowed_ptr(task, cpu_all_mask);
324 }
325 kfree(create);
326 return task;
327}
328EXPORT_SYMBOL(kthread_create_on_node);
329
330static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
331{
332 /* Must have done schedule() in kthread() before we set_task_cpu */
333 if (!wait_task_inactive(p, state)) {
334 WARN_ON(1);
335 return;
336 }
337 /* It's safe because the task is inactive. */
338 do_set_cpus_allowed(p, cpumask_of(cpu));
339 p->flags |= PF_NO_SETAFFINITY;
340}
341
342/**
343 * kthread_bind - bind a just-created kthread to a cpu.
344 * @p: thread created by kthread_create().
345 * @cpu: cpu (might not be online, must be possible) for @k to run on.
346 *
347 * Description: This function is equivalent to set_cpus_allowed(),
348 * except that @cpu doesn't need to be online, and the thread must be
349 * stopped (i.e., just returned from kthread_create()).
350 */
351void kthread_bind(struct task_struct *p, unsigned int cpu)
352{
353 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
354}
355EXPORT_SYMBOL(kthread_bind);
356
357/**
358 * kthread_create_on_cpu - Create a cpu bound kthread
359 * @threadfn: the function to run until signal_pending(current).
360 * @data: data ptr for @threadfn.
361 * @cpu: The cpu on which the thread should be bound,
362 * @namefmt: printf-style name for the thread. Format is restricted
363 * to "name.*%u". Code fills in cpu number.
364 *
365 * Description: This helper function creates and names a kernel thread
366 * The thread will be woken and put into park mode.
367 */
368struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
369 void *data, unsigned int cpu,
370 const char *namefmt)
371{
372 struct task_struct *p;
373
374 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
375 cpu);
376 if (IS_ERR(p))
377 return p;
378 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
379 to_kthread(p)->cpu = cpu;
380 /* Park the thread to get it out of TASK_UNINTERRUPTIBLE state */
381 kthread_park(p);
382 return p;
383}
384
385static void __kthread_unpark(struct task_struct *k, struct kthread *kthread)
386{
387 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
388 /*
389 * We clear the IS_PARKED bit here as we don't wait
390 * until the task has left the park code. So if we'd
391 * park before that happens we'd see the IS_PARKED bit
392 * which might be about to be cleared.
393 */
394 if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
395 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
396 __kthread_bind(k, kthread->cpu, TASK_PARKED);
397 wake_up_state(k, TASK_PARKED);
398 }
399}
400
401/**
402 * kthread_unpark - unpark a thread created by kthread_create().
403 * @k: thread created by kthread_create().
404 *
405 * Sets kthread_should_park() for @k to return false, wakes it, and
406 * waits for it to return. If the thread is marked percpu then its
407 * bound to the cpu again.
408 */
409void kthread_unpark(struct task_struct *k)
410{
411 struct kthread *kthread = to_live_kthread(k);
412
413 if (kthread)
414 __kthread_unpark(k, kthread);
415}
416EXPORT_SYMBOL_GPL(kthread_unpark);
417
418/**
419 * kthread_park - park a thread created by kthread_create().
420 * @k: thread created by kthread_create().
421 *
422 * Sets kthread_should_park() for @k to return true, wakes it, and
423 * waits for it to return. This can also be called after kthread_create()
424 * instead of calling wake_up_process(): the thread will park without
425 * calling threadfn().
426 *
427 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
428 * If called by the kthread itself just the park bit is set.
429 */
430int kthread_park(struct task_struct *k)
431{
432 struct kthread *kthread = to_live_kthread(k);
433 int ret = -ENOSYS;
434
435 if (kthread) {
436 if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
437 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
438 if (k != current) {
439 wake_up_process(k);
440 wait_for_completion(&kthread->parked);
441 }
442 }
443 ret = 0;
444 }
445 return ret;
446}
447EXPORT_SYMBOL_GPL(kthread_park);
448
449/**
450 * kthread_stop - stop a thread created by kthread_create().
451 * @k: thread created by kthread_create().
452 *
453 * Sets kthread_should_stop() for @k to return true, wakes it, and
454 * waits for it to exit. This can also be called after kthread_create()
455 * instead of calling wake_up_process(): the thread will exit without
456 * calling threadfn().
457 *
458 * If threadfn() may call do_exit() itself, the caller must ensure
459 * task_struct can't go away.
460 *
461 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
462 * was never called.
463 */
464int kthread_stop(struct task_struct *k)
465{
466 struct kthread *kthread;
467 int ret;
468
469 trace_sched_kthread_stop(k);
470
471 get_task_struct(k);
472 kthread = to_live_kthread(k);
473 if (kthread) {
474 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
475 __kthread_unpark(k, kthread);
476 wake_up_process(k);
477 wait_for_completion(&kthread->exited);
478 }
479 ret = k->exit_code;
480 put_task_struct(k);
481
482 trace_sched_kthread_stop_ret(ret);
483 return ret;
484}
485EXPORT_SYMBOL(kthread_stop);
486
487int kthreadd(void *unused)
488{
489 struct task_struct *tsk = current;
490
491 /* Setup a clean context for our children to inherit. */
492 set_task_comm(tsk, "kthreadd");
493 ignore_signals(tsk);
494 set_cpus_allowed_ptr(tsk, cpu_all_mask);
495 set_mems_allowed(node_states[N_MEMORY]);
496
497 current->flags |= PF_NOFREEZE;
498
499 for (;;) {
500 set_current_state(TASK_INTERRUPTIBLE);
501 if (list_empty(&kthread_create_list))
502 schedule();
503 __set_current_state(TASK_RUNNING);
504
505 spin_lock(&kthread_create_lock);
506 while (!list_empty(&kthread_create_list)) {
507 struct kthread_create_info *create;
508
509 create = list_entry(kthread_create_list.next,
510 struct kthread_create_info, list);
511 list_del_init(&create->list);
512 spin_unlock(&kthread_create_lock);
513
514 create_kthread(create);
515
516 spin_lock(&kthread_create_lock);
517 }
518 spin_unlock(&kthread_create_lock);
519 }
520
521 return 0;
522}
523
524void __init_kthread_worker(struct kthread_worker *worker,
525 const char *name,
526 struct lock_class_key *key)
527{
528 spin_lock_init(&worker->lock);
529 lockdep_set_class_and_name(&worker->lock, key, name);
530 INIT_LIST_HEAD(&worker->work_list);
531 worker->task = NULL;
532}
533EXPORT_SYMBOL_GPL(__init_kthread_worker);
534
535/**
536 * kthread_worker_fn - kthread function to process kthread_worker
537 * @worker_ptr: pointer to initialized kthread_worker
538 *
539 * This function can be used as @threadfn to kthread_create() or
540 * kthread_run() with @worker_ptr argument pointing to an initialized
541 * kthread_worker. The started kthread will process work_list until
542 * the it is stopped with kthread_stop(). A kthread can also call
543 * this function directly after extra initialization.
544 *
545 * Different kthreads can be used for the same kthread_worker as long
546 * as there's only one kthread attached to it at any given time. A
547 * kthread_worker without an attached kthread simply collects queued
548 * kthread_works.
549 */
550int kthread_worker_fn(void *worker_ptr)
551{
552 struct kthread_worker *worker = worker_ptr;
553 struct kthread_work *work;
554
555 WARN_ON(worker->task);
556 worker->task = current;
557repeat:
558 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
559
560 if (kthread_should_stop()) {
561 __set_current_state(TASK_RUNNING);
562 spin_lock_irq(&worker->lock);
563 worker->task = NULL;
564 spin_unlock_irq(&worker->lock);
565 return 0;
566 }
567
568 work = NULL;
569 spin_lock_irq(&worker->lock);
570 if (!list_empty(&worker->work_list)) {
571 work = list_first_entry(&worker->work_list,
572 struct kthread_work, node);
573 list_del_init(&work->node);
574 }
575 worker->current_work = work;
576 spin_unlock_irq(&worker->lock);
577
578 if (work) {
579 __set_current_state(TASK_RUNNING);
580 work->func(work);
581 } else if (!freezing(current))
582 schedule();
583
584 try_to_freeze();
585 goto repeat;
586}
587EXPORT_SYMBOL_GPL(kthread_worker_fn);
588
589/* insert @work before @pos in @worker */
590static void insert_kthread_work(struct kthread_worker *worker,
591 struct kthread_work *work,
592 struct list_head *pos)
593{
594 lockdep_assert_held(&worker->lock);
595
596 list_add_tail(&work->node, pos);
597 work->worker = worker;
598 if (!worker->current_work && likely(worker->task))
599 wake_up_process(worker->task);
600}
601
602/**
603 * queue_kthread_work - queue a kthread_work
604 * @worker: target kthread_worker
605 * @work: kthread_work to queue
606 *
607 * Queue @work to work processor @task for async execution. @task
608 * must have been created with kthread_worker_create(). Returns %true
609 * if @work was successfully queued, %false if it was already pending.
610 */
611bool queue_kthread_work(struct kthread_worker *worker,
612 struct kthread_work *work)
613{
614 bool ret = false;
615 unsigned long flags;
616
617 spin_lock_irqsave(&worker->lock, flags);
618 if (list_empty(&work->node)) {
619 insert_kthread_work(worker, work, &worker->work_list);
620 ret = true;
621 }
622 spin_unlock_irqrestore(&worker->lock, flags);
623 return ret;
624}
625EXPORT_SYMBOL_GPL(queue_kthread_work);
626
627struct kthread_flush_work {
628 struct kthread_work work;
629 struct completion done;
630};
631
632static void kthread_flush_work_fn(struct kthread_work *work)
633{
634 struct kthread_flush_work *fwork =
635 container_of(work, struct kthread_flush_work, work);
636 complete(&fwork->done);
637}
638
639/**
640 * flush_kthread_work - flush a kthread_work
641 * @work: work to flush
642 *
643 * If @work is queued or executing, wait for it to finish execution.
644 */
645void flush_kthread_work(struct kthread_work *work)
646{
647 struct kthread_flush_work fwork = {
648 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
649 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
650 };
651 struct kthread_worker *worker;
652 bool noop = false;
653
654retry:
655 worker = work->worker;
656 if (!worker)
657 return;
658
659 spin_lock_irq(&worker->lock);
660 if (work->worker != worker) {
661 spin_unlock_irq(&worker->lock);
662 goto retry;
663 }
664
665 if (!list_empty(&work->node))
666 insert_kthread_work(worker, &fwork.work, work->node.next);
667 else if (worker->current_work == work)
668 insert_kthread_work(worker, &fwork.work, worker->work_list.next);
669 else
670 noop = true;
671
672 spin_unlock_irq(&worker->lock);
673
674 if (!noop)
675 wait_for_completion(&fwork.done);
676}
677EXPORT_SYMBOL_GPL(flush_kthread_work);
678
679/**
680 * flush_kthread_worker - flush all current works on a kthread_worker
681 * @worker: worker to flush
682 *
683 * Wait until all currently executing or pending works on @worker are
684 * finished.
685 */
686void flush_kthread_worker(struct kthread_worker *worker)
687{
688 struct kthread_flush_work fwork = {
689 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
690 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
691 };
692
693 queue_kthread_work(worker, &fwork.work);
694 wait_for_completion(&fwork.done);
695}
696EXPORT_SYMBOL_GPL(flush_kthread_worker);