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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: 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 */
270struct 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, ¶m);
324 set_cpus_allowed_ptr(task, cpu_all_mask);
325 }
326 kfree(create);
327 return task;
328}
329EXPORT_SYMBOL(kthread_create_on_node);
330
331static 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
347static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
348{
349 __kthread_bind_mask(p, cpumask_of(cpu), state);
350}
351
352void 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 */
366void kthread_bind(struct task_struct *p, unsigned int cpu)
367{
368 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
369}
370EXPORT_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 */
383struct 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
400static 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 */
424void 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}
431EXPORT_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 */
445int 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}
462EXPORT_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 */
479int 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}
500EXPORT_SYMBOL(kthread_stop);
501
502int 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
539void __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}
548EXPORT_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 */
565int 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;
572repeat:
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}
602EXPORT_SYMBOL_GPL(kthread_worker_fn);
603
604/* insert @work before @pos in @worker */
605static 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 */
626bool 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}
640EXPORT_SYMBOL_GPL(queue_kthread_work);
641
642struct kthread_flush_work {
643 struct kthread_work work;
644 struct completion done;
645};
646
647static 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 */
660void 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
669retry:
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}
692EXPORT_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 */
701void 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}
711EXPORT_SYMBOL_GPL(flush_kthread_worker);
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/module.h>
16#include <linux/mutex.h>
17#include <linux/slab.h>
18#include <linux/freezer.h>
19#include <trace/events/sched.h>
20
21static DEFINE_SPINLOCK(kthread_create_lock);
22static LIST_HEAD(kthread_create_list);
23struct task_struct *kthreadd_task;
24
25struct kthread_create_info
26{
27 /* Information passed to kthread() from kthreadd. */
28 int (*threadfn)(void *data);
29 void *data;
30 int node;
31
32 /* Result passed back to kthread_create() from kthreadd. */
33 struct task_struct *result;
34 struct completion done;
35
36 struct list_head list;
37};
38
39struct kthread {
40 int should_stop;
41 void *data;
42 struct completion exited;
43};
44
45#define to_kthread(tsk) \
46 container_of((tsk)->vfork_done, struct kthread, exited)
47
48/**
49 * kthread_should_stop - should this kthread return now?
50 *
51 * When someone calls kthread_stop() on your kthread, it will be woken
52 * and this will return true. You should then return, and your return
53 * value will be passed through to kthread_stop().
54 */
55int kthread_should_stop(void)
56{
57 return to_kthread(current)->should_stop;
58}
59EXPORT_SYMBOL(kthread_should_stop);
60
61/**
62 * kthread_data - return data value specified on kthread creation
63 * @task: kthread task in question
64 *
65 * Return the data value specified when kthread @task was created.
66 * The caller is responsible for ensuring the validity of @task when
67 * calling this function.
68 */
69void *kthread_data(struct task_struct *task)
70{
71 return to_kthread(task)->data;
72}
73
74static int kthread(void *_create)
75{
76 /* Copy data: it's on kthread's stack */
77 struct kthread_create_info *create = _create;
78 int (*threadfn)(void *data) = create->threadfn;
79 void *data = create->data;
80 struct kthread self;
81 int ret;
82
83 self.should_stop = 0;
84 self.data = data;
85 init_completion(&self.exited);
86 current->vfork_done = &self.exited;
87
88 /* OK, tell user we're spawned, wait for stop or wakeup */
89 __set_current_state(TASK_UNINTERRUPTIBLE);
90 create->result = current;
91 complete(&create->done);
92 schedule();
93
94 ret = -EINTR;
95 if (!self.should_stop)
96 ret = threadfn(data);
97
98 /* we can't just return, we must preserve "self" on stack */
99 do_exit(ret);
100}
101
102/* called from do_fork() to get node information for about to be created task */
103int tsk_fork_get_node(struct task_struct *tsk)
104{
105#ifdef CONFIG_NUMA
106 if (tsk == kthreadd_task)
107 return tsk->pref_node_fork;
108#endif
109 return numa_node_id();
110}
111
112static void create_kthread(struct kthread_create_info *create)
113{
114 int pid;
115
116#ifdef CONFIG_NUMA
117 current->pref_node_fork = create->node;
118#endif
119 /* We want our own signal handler (we take no signals by default). */
120 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
121 if (pid < 0) {
122 create->result = ERR_PTR(pid);
123 complete(&create->done);
124 }
125}
126
127/**
128 * kthread_create_on_node - create a kthread.
129 * @threadfn: the function to run until signal_pending(current).
130 * @data: data ptr for @threadfn.
131 * @node: memory node number.
132 * @namefmt: printf-style name for the thread.
133 *
134 * Description: This helper function creates and names a kernel
135 * thread. The thread will be stopped: use wake_up_process() to start
136 * it. See also kthread_run().
137 *
138 * If thread is going to be bound on a particular cpu, give its node
139 * in @node, to get NUMA affinity for kthread stack, or else give -1.
140 * When woken, the thread will run @threadfn() with @data as its
141 * argument. @threadfn() can either call do_exit() directly if it is a
142 * standalone thread for which no one will call kthread_stop(), or
143 * return when 'kthread_should_stop()' is true (which means
144 * kthread_stop() has been called). The return value should be zero
145 * or a negative error number; it will be passed to kthread_stop().
146 *
147 * Returns a task_struct or ERR_PTR(-ENOMEM).
148 */
149struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
150 void *data,
151 int node,
152 const char namefmt[],
153 ...)
154{
155 struct kthread_create_info create;
156
157 create.threadfn = threadfn;
158 create.data = data;
159 create.node = node;
160 init_completion(&create.done);
161
162 spin_lock(&kthread_create_lock);
163 list_add_tail(&create.list, &kthread_create_list);
164 spin_unlock(&kthread_create_lock);
165
166 wake_up_process(kthreadd_task);
167 wait_for_completion(&create.done);
168
169 if (!IS_ERR(create.result)) {
170 static const struct sched_param param = { .sched_priority = 0 };
171 va_list args;
172
173 va_start(args, namefmt);
174 vsnprintf(create.result->comm, sizeof(create.result->comm),
175 namefmt, args);
176 va_end(args);
177 /*
178 * root may have changed our (kthreadd's) priority or CPU mask.
179 * The kernel thread should not inherit these properties.
180 */
181 sched_setscheduler_nocheck(create.result, SCHED_NORMAL, ¶m);
182 set_cpus_allowed_ptr(create.result, cpu_all_mask);
183 }
184 return create.result;
185}
186EXPORT_SYMBOL(kthread_create_on_node);
187
188/**
189 * kthread_bind - bind a just-created kthread to a cpu.
190 * @p: thread created by kthread_create().
191 * @cpu: cpu (might not be online, must be possible) for @k to run on.
192 *
193 * Description: This function is equivalent to set_cpus_allowed(),
194 * except that @cpu doesn't need to be online, and the thread must be
195 * stopped (i.e., just returned from kthread_create()).
196 */
197void kthread_bind(struct task_struct *p, unsigned int cpu)
198{
199 /* Must have done schedule() in kthread() before we set_task_cpu */
200 if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) {
201 WARN_ON(1);
202 return;
203 }
204
205 /* It's safe because the task is inactive. */
206 do_set_cpus_allowed(p, cpumask_of(cpu));
207 p->flags |= PF_THREAD_BOUND;
208}
209EXPORT_SYMBOL(kthread_bind);
210
211/**
212 * kthread_stop - stop a thread created by kthread_create().
213 * @k: thread created by kthread_create().
214 *
215 * Sets kthread_should_stop() for @k to return true, wakes it, and
216 * waits for it to exit. This can also be called after kthread_create()
217 * instead of calling wake_up_process(): the thread will exit without
218 * calling threadfn().
219 *
220 * If threadfn() may call do_exit() itself, the caller must ensure
221 * task_struct can't go away.
222 *
223 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
224 * was never called.
225 */
226int kthread_stop(struct task_struct *k)
227{
228 struct kthread *kthread;
229 int ret;
230
231 trace_sched_kthread_stop(k);
232 get_task_struct(k);
233
234 kthread = to_kthread(k);
235 barrier(); /* it might have exited */
236 if (k->vfork_done != NULL) {
237 kthread->should_stop = 1;
238 wake_up_process(k);
239 wait_for_completion(&kthread->exited);
240 }
241 ret = k->exit_code;
242
243 put_task_struct(k);
244 trace_sched_kthread_stop_ret(ret);
245
246 return ret;
247}
248EXPORT_SYMBOL(kthread_stop);
249
250int kthreadd(void *unused)
251{
252 struct task_struct *tsk = current;
253
254 /* Setup a clean context for our children to inherit. */
255 set_task_comm(tsk, "kthreadd");
256 ignore_signals(tsk);
257 set_cpus_allowed_ptr(tsk, cpu_all_mask);
258 set_mems_allowed(node_states[N_HIGH_MEMORY]);
259
260 current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
261
262 for (;;) {
263 set_current_state(TASK_INTERRUPTIBLE);
264 if (list_empty(&kthread_create_list))
265 schedule();
266 __set_current_state(TASK_RUNNING);
267
268 spin_lock(&kthread_create_lock);
269 while (!list_empty(&kthread_create_list)) {
270 struct kthread_create_info *create;
271
272 create = list_entry(kthread_create_list.next,
273 struct kthread_create_info, list);
274 list_del_init(&create->list);
275 spin_unlock(&kthread_create_lock);
276
277 create_kthread(create);
278
279 spin_lock(&kthread_create_lock);
280 }
281 spin_unlock(&kthread_create_lock);
282 }
283
284 return 0;
285}
286
287void __init_kthread_worker(struct kthread_worker *worker,
288 const char *name,
289 struct lock_class_key *key)
290{
291 spin_lock_init(&worker->lock);
292 lockdep_set_class_and_name(&worker->lock, key, name);
293 INIT_LIST_HEAD(&worker->work_list);
294 worker->task = NULL;
295}
296EXPORT_SYMBOL_GPL(__init_kthread_worker);
297
298/**
299 * kthread_worker_fn - kthread function to process kthread_worker
300 * @worker_ptr: pointer to initialized kthread_worker
301 *
302 * This function can be used as @threadfn to kthread_create() or
303 * kthread_run() with @worker_ptr argument pointing to an initialized
304 * kthread_worker. The started kthread will process work_list until
305 * the it is stopped with kthread_stop(). A kthread can also call
306 * this function directly after extra initialization.
307 *
308 * Different kthreads can be used for the same kthread_worker as long
309 * as there's only one kthread attached to it at any given time. A
310 * kthread_worker without an attached kthread simply collects queued
311 * kthread_works.
312 */
313int kthread_worker_fn(void *worker_ptr)
314{
315 struct kthread_worker *worker = worker_ptr;
316 struct kthread_work *work;
317
318 WARN_ON(worker->task);
319 worker->task = current;
320repeat:
321 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
322
323 if (kthread_should_stop()) {
324 __set_current_state(TASK_RUNNING);
325 spin_lock_irq(&worker->lock);
326 worker->task = NULL;
327 spin_unlock_irq(&worker->lock);
328 return 0;
329 }
330
331 work = NULL;
332 spin_lock_irq(&worker->lock);
333 if (!list_empty(&worker->work_list)) {
334 work = list_first_entry(&worker->work_list,
335 struct kthread_work, node);
336 list_del_init(&work->node);
337 }
338 spin_unlock_irq(&worker->lock);
339
340 if (work) {
341 __set_current_state(TASK_RUNNING);
342 work->func(work);
343 smp_wmb(); /* wmb worker-b0 paired with flush-b1 */
344 work->done_seq = work->queue_seq;
345 smp_mb(); /* mb worker-b1 paired with flush-b0 */
346 if (atomic_read(&work->flushing))
347 wake_up_all(&work->done);
348 } else if (!freezing(current))
349 schedule();
350
351 try_to_freeze();
352 goto repeat;
353}
354EXPORT_SYMBOL_GPL(kthread_worker_fn);
355
356/**
357 * queue_kthread_work - queue a kthread_work
358 * @worker: target kthread_worker
359 * @work: kthread_work to queue
360 *
361 * Queue @work to work processor @task for async execution. @task
362 * must have been created with kthread_worker_create(). Returns %true
363 * if @work was successfully queued, %false if it was already pending.
364 */
365bool queue_kthread_work(struct kthread_worker *worker,
366 struct kthread_work *work)
367{
368 bool ret = false;
369 unsigned long flags;
370
371 spin_lock_irqsave(&worker->lock, flags);
372 if (list_empty(&work->node)) {
373 list_add_tail(&work->node, &worker->work_list);
374 work->queue_seq++;
375 if (likely(worker->task))
376 wake_up_process(worker->task);
377 ret = true;
378 }
379 spin_unlock_irqrestore(&worker->lock, flags);
380 return ret;
381}
382EXPORT_SYMBOL_GPL(queue_kthread_work);
383
384/**
385 * flush_kthread_work - flush a kthread_work
386 * @work: work to flush
387 *
388 * If @work is queued or executing, wait for it to finish execution.
389 */
390void flush_kthread_work(struct kthread_work *work)
391{
392 int seq = work->queue_seq;
393
394 atomic_inc(&work->flushing);
395
396 /*
397 * mb flush-b0 paired with worker-b1, to make sure either
398 * worker sees the above increment or we see done_seq update.
399 */
400 smp_mb__after_atomic_inc();
401
402 /* A - B <= 0 tests whether B is in front of A regardless of overflow */
403 wait_event(work->done, seq - work->done_seq <= 0);
404 atomic_dec(&work->flushing);
405
406 /*
407 * rmb flush-b1 paired with worker-b0, to make sure our caller
408 * sees every change made by work->func().
409 */
410 smp_mb__after_atomic_dec();
411}
412EXPORT_SYMBOL_GPL(flush_kthread_work);
413
414struct kthread_flush_work {
415 struct kthread_work work;
416 struct completion done;
417};
418
419static void kthread_flush_work_fn(struct kthread_work *work)
420{
421 struct kthread_flush_work *fwork =
422 container_of(work, struct kthread_flush_work, work);
423 complete(&fwork->done);
424}
425
426/**
427 * flush_kthread_worker - flush all current works on a kthread_worker
428 * @worker: worker to flush
429 *
430 * Wait until all currently executing or pending works on @worker are
431 * finished.
432 */
433void flush_kthread_worker(struct kthread_worker *worker)
434{
435 struct kthread_flush_work fwork = {
436 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
437 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
438 };
439
440 queue_kthread_work(worker, &fwork.work);
441 wait_for_completion(&fwork.done);
442}
443EXPORT_SYMBOL_GPL(flush_kthread_worker);