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[mirror_ubuntu-bionic-kernel.git] / kernel / kthread.c
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
23 static DEFINE_SPINLOCK(kthread_create_lock);
24 static LIST_HEAD(kthread_create_list);
25 struct task_struct *kthreadd_task;
26
27 struct 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
41 struct kthread {
42 unsigned long flags;
43 unsigned int cpu;
44 void *data;
45 struct completion parked;
46 struct completion exited;
47 };
48
49 enum 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
59 static inline struct kthread *to_kthread(struct task_struct *k)
60 {
61 return __to_kthread(k->vfork_done);
62 }
63
64 static 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 */
79 bool kthread_should_stop(void)
80 {
81 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
82 }
83 EXPORT_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 */
96 bool kthread_should_park(void)
97 {
98 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(current)->flags);
99 }
100 EXPORT_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 */
111 bool 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 }
125 EXPORT_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 */
135 void *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 */
149 void *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
158 static 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
171 void kthread_parkme(void)
172 {
173 __kthread_parkme(to_kthread(current));
174 }
175 EXPORT_SYMBOL_GPL(kthread_parkme);
176
177 static 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 */
216 int 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
225 static 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: task and thread structures for the thread are allocated on this node
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(). The new thread has SCHED_NORMAL policy and
257 * is affine to all CPUs.
258 *
259 * If thread is going to be bound on a particular cpu, give its node
260 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
261 * When woken, the thread will run @threadfn() with @data as its
262 * argument. @threadfn() can either call do_exit() directly if it is a
263 * standalone thread for which no one will call kthread_stop(), or
264 * return when 'kthread_should_stop()' is true (which means
265 * kthread_stop() has been called). The return value should be zero
266 * or a negative error number; it will be passed to kthread_stop().
267 *
268 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
269 */
270 struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
271 void *data, int node,
272 const char namefmt[],
273 ...)
274 {
275 DECLARE_COMPLETION_ONSTACK(done);
276 struct task_struct *task;
277 struct kthread_create_info *create = kmalloc(sizeof(*create),
278 GFP_KERNEL);
279
280 if (!create)
281 return ERR_PTR(-ENOMEM);
282 create->threadfn = threadfn;
283 create->data = data;
284 create->node = node;
285 create->done = &done;
286
287 spin_lock(&kthread_create_lock);
288 list_add_tail(&create->list, &kthread_create_list);
289 spin_unlock(&kthread_create_lock);
290
291 wake_up_process(kthreadd_task);
292 /*
293 * Wait for completion in killable state, for I might be chosen by
294 * the OOM killer while kthreadd is trying to allocate memory for
295 * new kernel thread.
296 */
297 if (unlikely(wait_for_completion_killable(&done))) {
298 /*
299 * If I was SIGKILLed before kthreadd (or new kernel thread)
300 * calls complete(), leave the cleanup of this structure to
301 * that thread.
302 */
303 if (xchg(&create->done, NULL))
304 return ERR_PTR(-EINTR);
305 /*
306 * kthreadd (or new kernel thread) will call complete()
307 * shortly.
308 */
309 wait_for_completion(&done);
310 }
311 task = create->result;
312 if (!IS_ERR(task)) {
313 static const struct sched_param param = { .sched_priority = 0 };
314 va_list args;
315
316 va_start(args, namefmt);
317 vsnprintf(task->comm, sizeof(task->comm), namefmt, args);
318 va_end(args);
319 /*
320 * root may have changed our (kthreadd's) priority or CPU mask.
321 * The kernel thread should not inherit these properties.
322 */
323 sched_setscheduler_nocheck(task, SCHED_NORMAL, &param);
324 set_cpus_allowed_ptr(task, cpu_all_mask);
325 }
326 kfree(create);
327 return task;
328 }
329 EXPORT_SYMBOL(kthread_create_on_node);
330
331 static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
332 {
333 unsigned long flags;
334
335 if (!wait_task_inactive(p, state)) {
336 WARN_ON(1);
337 return;
338 }
339
340 /* It's safe because the task is inactive. */
341 raw_spin_lock_irqsave(&p->pi_lock, flags);
342 do_set_cpus_allowed(p, mask);
343 p->flags |= PF_NO_SETAFFINITY;
344 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
345 }
346
347 static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
348 {
349 __kthread_bind_mask(p, cpumask_of(cpu), state);
350 }
351
352 void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
353 {
354 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
355 }
356
357 /**
358 * kthread_bind - bind a just-created kthread to a cpu.
359 * @p: thread created by kthread_create().
360 * @cpu: cpu (might not be online, must be possible) for @k to run on.
361 *
362 * Description: This function is equivalent to set_cpus_allowed(),
363 * except that @cpu doesn't need to be online, and the thread must be
364 * stopped (i.e., just returned from kthread_create()).
365 */
366 void kthread_bind(struct task_struct *p, unsigned int cpu)
367 {
368 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
369 }
370 EXPORT_SYMBOL(kthread_bind);
371
372 /**
373 * kthread_create_on_cpu - Create a cpu bound kthread
374 * @threadfn: the function to run until signal_pending(current).
375 * @data: data ptr for @threadfn.
376 * @cpu: The cpu on which the thread should be bound,
377 * @namefmt: printf-style name for the thread. Format is restricted
378 * to "name.*%u". Code fills in cpu number.
379 *
380 * Description: This helper function creates and names a kernel thread
381 * The thread will be woken and put into park mode.
382 */
383 struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
384 void *data, unsigned int cpu,
385 const char *namefmt)
386 {
387 struct task_struct *p;
388
389 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
390 cpu);
391 if (IS_ERR(p))
392 return p;
393 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
394 to_kthread(p)->cpu = cpu;
395 /* Park the thread to get it out of TASK_UNINTERRUPTIBLE state */
396 kthread_park(p);
397 return p;
398 }
399
400 static void __kthread_unpark(struct task_struct *k, struct kthread *kthread)
401 {
402 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
403 /*
404 * We clear the IS_PARKED bit here as we don't wait
405 * until the task has left the park code. So if we'd
406 * park before that happens we'd see the IS_PARKED bit
407 * which might be about to be cleared.
408 */
409 if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
410 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
411 __kthread_bind(k, kthread->cpu, TASK_PARKED);
412 wake_up_state(k, TASK_PARKED);
413 }
414 }
415
416 /**
417 * kthread_unpark - unpark a thread created by kthread_create().
418 * @k: thread created by kthread_create().
419 *
420 * Sets kthread_should_park() for @k to return false, wakes it, and
421 * waits for it to return. If the thread is marked percpu then its
422 * bound to the cpu again.
423 */
424 void kthread_unpark(struct task_struct *k)
425 {
426 struct kthread *kthread = to_live_kthread(k);
427
428 if (kthread)
429 __kthread_unpark(k, kthread);
430 }
431 EXPORT_SYMBOL_GPL(kthread_unpark);
432
433 /**
434 * kthread_park - park a thread created by kthread_create().
435 * @k: thread created by kthread_create().
436 *
437 * Sets kthread_should_park() for @k to return true, wakes it, and
438 * waits for it to return. This can also be called after kthread_create()
439 * instead of calling wake_up_process(): the thread will park without
440 * calling threadfn().
441 *
442 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
443 * If called by the kthread itself just the park bit is set.
444 */
445 int kthread_park(struct task_struct *k)
446 {
447 struct kthread *kthread = to_live_kthread(k);
448 int ret = -ENOSYS;
449
450 if (kthread) {
451 if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
452 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
453 if (k != current) {
454 wake_up_process(k);
455 wait_for_completion(&kthread->parked);
456 }
457 }
458 ret = 0;
459 }
460 return ret;
461 }
462 EXPORT_SYMBOL_GPL(kthread_park);
463
464 /**
465 * kthread_stop - stop a thread created by kthread_create().
466 * @k: thread created by kthread_create().
467 *
468 * Sets kthread_should_stop() for @k to return true, wakes it, and
469 * waits for it to exit. This can also be called after kthread_create()
470 * instead of calling wake_up_process(): the thread will exit without
471 * calling threadfn().
472 *
473 * If threadfn() may call do_exit() itself, the caller must ensure
474 * task_struct can't go away.
475 *
476 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
477 * was never called.
478 */
479 int kthread_stop(struct task_struct *k)
480 {
481 struct kthread *kthread;
482 int ret;
483
484 trace_sched_kthread_stop(k);
485
486 get_task_struct(k);
487 kthread = to_live_kthread(k);
488 if (kthread) {
489 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
490 __kthread_unpark(k, kthread);
491 wake_up_process(k);
492 wait_for_completion(&kthread->exited);
493 }
494 ret = k->exit_code;
495 put_task_struct(k);
496
497 trace_sched_kthread_stop_ret(ret);
498 return ret;
499 }
500 EXPORT_SYMBOL(kthread_stop);
501
502 int kthreadd(void *unused)
503 {
504 struct task_struct *tsk = current;
505
506 /* Setup a clean context for our children to inherit. */
507 set_task_comm(tsk, "kthreadd");
508 ignore_signals(tsk);
509 set_cpus_allowed_ptr(tsk, cpu_all_mask);
510 set_mems_allowed(node_states[N_MEMORY]);
511
512 current->flags |= PF_NOFREEZE;
513
514 for (;;) {
515 set_current_state(TASK_INTERRUPTIBLE);
516 if (list_empty(&kthread_create_list))
517 schedule();
518 __set_current_state(TASK_RUNNING);
519
520 spin_lock(&kthread_create_lock);
521 while (!list_empty(&kthread_create_list)) {
522 struct kthread_create_info *create;
523
524 create = list_entry(kthread_create_list.next,
525 struct kthread_create_info, list);
526 list_del_init(&create->list);
527 spin_unlock(&kthread_create_lock);
528
529 create_kthread(create);
530
531 spin_lock(&kthread_create_lock);
532 }
533 spin_unlock(&kthread_create_lock);
534 }
535
536 return 0;
537 }
538
539 void __init_kthread_worker(struct kthread_worker *worker,
540 const char *name,
541 struct lock_class_key *key)
542 {
543 spin_lock_init(&worker->lock);
544 lockdep_set_class_and_name(&worker->lock, key, name);
545 INIT_LIST_HEAD(&worker->work_list);
546 worker->task = NULL;
547 }
548 EXPORT_SYMBOL_GPL(__init_kthread_worker);
549
550 /**
551 * kthread_worker_fn - kthread function to process kthread_worker
552 * @worker_ptr: pointer to initialized kthread_worker
553 *
554 * This function can be used as @threadfn to kthread_create() or
555 * kthread_run() with @worker_ptr argument pointing to an initialized
556 * kthread_worker. The started kthread will process work_list until
557 * the it is stopped with kthread_stop(). A kthread can also call
558 * this function directly after extra initialization.
559 *
560 * Different kthreads can be used for the same kthread_worker as long
561 * as there's only one kthread attached to it at any given time. A
562 * kthread_worker without an attached kthread simply collects queued
563 * kthread_works.
564 */
565 int kthread_worker_fn(void *worker_ptr)
566 {
567 struct kthread_worker *worker = worker_ptr;
568 struct kthread_work *work;
569
570 WARN_ON(worker->task);
571 worker->task = current;
572 repeat:
573 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
574
575 if (kthread_should_stop()) {
576 __set_current_state(TASK_RUNNING);
577 spin_lock_irq(&worker->lock);
578 worker->task = NULL;
579 spin_unlock_irq(&worker->lock);
580 return 0;
581 }
582
583 work = NULL;
584 spin_lock_irq(&worker->lock);
585 if (!list_empty(&worker->work_list)) {
586 work = list_first_entry(&worker->work_list,
587 struct kthread_work, node);
588 list_del_init(&work->node);
589 }
590 worker->current_work = work;
591 spin_unlock_irq(&worker->lock);
592
593 if (work) {
594 __set_current_state(TASK_RUNNING);
595 work->func(work);
596 } else if (!freezing(current))
597 schedule();
598
599 try_to_freeze();
600 goto repeat;
601 }
602 EXPORT_SYMBOL_GPL(kthread_worker_fn);
603
604 /* insert @work before @pos in @worker */
605 static void insert_kthread_work(struct kthread_worker *worker,
606 struct kthread_work *work,
607 struct list_head *pos)
608 {
609 lockdep_assert_held(&worker->lock);
610
611 list_add_tail(&work->node, pos);
612 work->worker = worker;
613 if (!worker->current_work && likely(worker->task))
614 wake_up_process(worker->task);
615 }
616
617 /**
618 * queue_kthread_work - queue a kthread_work
619 * @worker: target kthread_worker
620 * @work: kthread_work to queue
621 *
622 * Queue @work to work processor @task for async execution. @task
623 * must have been created with kthread_worker_create(). Returns %true
624 * if @work was successfully queued, %false if it was already pending.
625 */
626 bool queue_kthread_work(struct kthread_worker *worker,
627 struct kthread_work *work)
628 {
629 bool ret = false;
630 unsigned long flags;
631
632 spin_lock_irqsave(&worker->lock, flags);
633 if (list_empty(&work->node)) {
634 insert_kthread_work(worker, work, &worker->work_list);
635 ret = true;
636 }
637 spin_unlock_irqrestore(&worker->lock, flags);
638 return ret;
639 }
640 EXPORT_SYMBOL_GPL(queue_kthread_work);
641
642 struct kthread_flush_work {
643 struct kthread_work work;
644 struct completion done;
645 };
646
647 static void kthread_flush_work_fn(struct kthread_work *work)
648 {
649 struct kthread_flush_work *fwork =
650 container_of(work, struct kthread_flush_work, work);
651 complete(&fwork->done);
652 }
653
654 /**
655 * flush_kthread_work - flush a kthread_work
656 * @work: work to flush
657 *
658 * If @work is queued or executing, wait for it to finish execution.
659 */
660 void flush_kthread_work(struct kthread_work *work)
661 {
662 struct kthread_flush_work fwork = {
663 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
664 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
665 };
666 struct kthread_worker *worker;
667 bool noop = false;
668
669 retry:
670 worker = work->worker;
671 if (!worker)
672 return;
673
674 spin_lock_irq(&worker->lock);
675 if (work->worker != worker) {
676 spin_unlock_irq(&worker->lock);
677 goto retry;
678 }
679
680 if (!list_empty(&work->node))
681 insert_kthread_work(worker, &fwork.work, work->node.next);
682 else if (worker->current_work == work)
683 insert_kthread_work(worker, &fwork.work, worker->work_list.next);
684 else
685 noop = true;
686
687 spin_unlock_irq(&worker->lock);
688
689 if (!noop)
690 wait_for_completion(&fwork.done);
691 }
692 EXPORT_SYMBOL_GPL(flush_kthread_work);
693
694 /**
695 * flush_kthread_worker - flush all current works on a kthread_worker
696 * @worker: worker to flush
697 *
698 * Wait until all currently executing or pending works on @worker are
699 * finished.
700 */
701 void flush_kthread_worker(struct kthread_worker *worker)
702 {
703 struct kthread_flush_work fwork = {
704 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
705 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
706 };
707
708 queue_kthread_work(worker, &fwork.work);
709 wait_for_completion(&fwork.done);
710 }
711 EXPORT_SYMBOL_GPL(flush_kthread_worker);