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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}
100
101/**
102 * kthread_freezable_should_stop - should this freezable kthread return now?
103 * @was_frozen: optional out parameter, indicates whether %current was frozen
104 *
105 * kthread_should_stop() for freezable kthreads, which will enter
106 * refrigerator if necessary. This function is safe from kthread_stop() /
107 * freezer deadlock and freezable kthreads should use this function instead
108 * of calling try_to_freeze() directly.
109 */
110bool kthread_freezable_should_stop(bool *was_frozen)
111{
112 bool frozen = false;
113
114 might_sleep();
115
116 if (unlikely(freezing(current)))
117 frozen = __refrigerator(true);
118
119 if (was_frozen)
120 *was_frozen = frozen;
121
122 return kthread_should_stop();
123}
124EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
125
126/**
127 * kthread_data - return data value specified on kthread creation
128 * @task: kthread task in question
129 *
130 * Return the data value specified when kthread @task was created.
131 * The caller is responsible for ensuring the validity of @task when
132 * calling this function.
133 */
134void *kthread_data(struct task_struct *task)
135{
136 return to_kthread(task)->data;
137}
138
139/**
140 * probe_kthread_data - speculative version of kthread_data()
141 * @task: possible kthread task in question
142 *
143 * @task could be a kthread task. Return the data value specified when it
144 * was created if accessible. If @task isn't a kthread task or its data is
145 * inaccessible for any reason, %NULL is returned. This function requires
146 * that @task itself is safe to dereference.
147 */
148void *probe_kthread_data(struct task_struct *task)
149{
150 struct kthread *kthread = to_kthread(task);
151 void *data = NULL;
152
153 probe_kernel_read(&data, &kthread->data, sizeof(data));
154 return data;
155}
156
157static void __kthread_parkme(struct kthread *self)
158{
159 __set_current_state(TASK_PARKED);
160 while (test_bit(KTHREAD_SHOULD_PARK, &self->flags)) {
161 if (!test_and_set_bit(KTHREAD_IS_PARKED, &self->flags))
162 complete(&self->parked);
163 schedule();
164 __set_current_state(TASK_PARKED);
165 }
166 clear_bit(KTHREAD_IS_PARKED, &self->flags);
167 __set_current_state(TASK_RUNNING);
168}
169
170void kthread_parkme(void)
171{
172 __kthread_parkme(to_kthread(current));
173}
174
175static int kthread(void *_create)
176{
177 /* Copy data: it's on kthread's stack */
178 struct kthread_create_info *create = _create;
179 int (*threadfn)(void *data) = create->threadfn;
180 void *data = create->data;
181 struct completion *done;
182 struct kthread self;
183 int ret;
184
185 self.flags = 0;
186 self.data = data;
187 init_completion(&self.exited);
188 init_completion(&self.parked);
189 current->vfork_done = &self.exited;
190
191 /* If user was SIGKILLed, I release the structure. */
192 done = xchg(&create->done, NULL);
193 if (!done) {
194 kfree(create);
195 do_exit(-EINTR);
196 }
197 /* OK, tell user we're spawned, wait for stop or wakeup */
198 __set_current_state(TASK_UNINTERRUPTIBLE);
199 create->result = current;
200 complete(done);
201 schedule();
202
203 ret = -EINTR;
204
205 if (!test_bit(KTHREAD_SHOULD_STOP, &self.flags)) {
206 __kthread_parkme(&self);
207 ret = threadfn(data);
208 }
209 /* we can't just return, we must preserve "self" on stack */
210 do_exit(ret);
211}
212
213/* called from do_fork() to get node information for about to be created task */
214int tsk_fork_get_node(struct task_struct *tsk)
215{
216#ifdef CONFIG_NUMA
217 if (tsk == kthreadd_task)
218 return tsk->pref_node_fork;
219#endif
220 return NUMA_NO_NODE;
221}
222
223static void create_kthread(struct kthread_create_info *create)
224{
225 int pid;
226
227#ifdef CONFIG_NUMA
228 current->pref_node_fork = create->node;
229#endif
230 /* We want our own signal handler (we take no signals by default). */
231 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
232 if (pid < 0) {
233 /* If user was SIGKILLed, I release the structure. */
234 struct completion *done = xchg(&create->done, NULL);
235
236 if (!done) {
237 kfree(create);
238 return;
239 }
240 create->result = ERR_PTR(pid);
241 complete(done);
242 }
243}
244
245/**
246 * kthread_create_on_node - create a kthread.
247 * @threadfn: the function to run until signal_pending(current).
248 * @data: data ptr for @threadfn.
249 * @node: memory node number.
250 * @namefmt: printf-style name for the thread.
251 *
252 * Description: This helper function creates and names a kernel
253 * thread. The thread will be stopped: use wake_up_process() to start
254 * it. See also kthread_run().
255 *
256 * If thread is going to be bound on a particular cpu, give its node
257 * in @node, to get NUMA affinity for kthread stack, or else give -1.
258 * When woken, the thread will run @threadfn() with @data as its
259 * argument. @threadfn() can either call do_exit() directly if it is a
260 * standalone thread for which no one will call kthread_stop(), or
261 * return when 'kthread_should_stop()' is true (which means
262 * kthread_stop() has been called). The return value should be zero
263 * or a negative error number; it will be passed to kthread_stop().
264 *
265 * Returns a task_struct or ERR_PTR(-ENOMEM).
266 */
267struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
268 void *data, int node,
269 const char namefmt[],
270 ...)
271{
272 DECLARE_COMPLETION_ONSTACK(done);
273 struct task_struct *task;
274 struct kthread_create_info *create = kmalloc(sizeof(*create),
275 GFP_KERNEL);
276
277 if (!create)
278 return ERR_PTR(-ENOMEM);
279 create->threadfn = threadfn;
280 create->data = data;
281 create->node = node;
282 create->done = &done;
283
284 spin_lock(&kthread_create_lock);
285 list_add_tail(&create->list, &kthread_create_list);
286 spin_unlock(&kthread_create_lock);
287
288 wake_up_process(kthreadd_task);
289 /*
290 * Wait for completion in killable state, for I might be chosen by
291 * the OOM killer while kthreadd is trying to allocate memory for
292 * new kernel thread.
293 */
294 if (unlikely(wait_for_completion_killable(&done))) {
295 /*
296 * If I was SIGKILLed before kthreadd (or new kernel thread)
297 * calls complete(), leave the cleanup of this structure to
298 * that thread.
299 */
300 if (xchg(&create->done, NULL))
301 return ERR_PTR(-ENOMEM);
302 /*
303 * kthreadd (or new kernel thread) will call complete()
304 * shortly.
305 */
306 wait_for_completion(&done);
307 }
308 task = create->result;
309 if (!IS_ERR(task)) {
310 static const struct sched_param param = { .sched_priority = 0 };
311 va_list args;
312
313 va_start(args, namefmt);
314 vsnprintf(task->comm, sizeof(task->comm), namefmt, args);
315 va_end(args);
316 /*
317 * root may have changed our (kthreadd's) priority or CPU mask.
318 * The kernel thread should not inherit these properties.
319 */
320 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
321 set_cpus_allowed_ptr(task, cpu_all_mask);
322 }
323 kfree(create);
324 return task;
325}
326EXPORT_SYMBOL(kthread_create_on_node);
327
328static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
329{
330 /* Must have done schedule() in kthread() before we set_task_cpu */
331 if (!wait_task_inactive(p, state)) {
332 WARN_ON(1);
333 return;
334 }
335 /* It's safe because the task is inactive. */
336 do_set_cpus_allowed(p, cpumask_of(cpu));
337 p->flags |= PF_NO_SETAFFINITY;
338}
339
340/**
341 * kthread_bind - bind a just-created kthread to a cpu.
342 * @p: thread created by kthread_create().
343 * @cpu: cpu (might not be online, must be possible) for @k to run on.
344 *
345 * Description: This function is equivalent to set_cpus_allowed(),
346 * except that @cpu doesn't need to be online, and the thread must be
347 * stopped (i.e., just returned from kthread_create()).
348 */
349void kthread_bind(struct task_struct *p, unsigned int cpu)
350{
351 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
352}
353EXPORT_SYMBOL(kthread_bind);
354
355/**
356 * kthread_create_on_cpu - Create a cpu bound kthread
357 * @threadfn: the function to run until signal_pending(current).
358 * @data: data ptr for @threadfn.
359 * @cpu: The cpu on which the thread should be bound,
360 * @namefmt: printf-style name for the thread. Format is restricted
361 * to "name.*%u". Code fills in cpu number.
362 *
363 * Description: This helper function creates and names a kernel thread
364 * The thread will be woken and put into park mode.
365 */
366struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
367 void *data, unsigned int cpu,
368 const char *namefmt)
369{
370 struct task_struct *p;
371
372 p = kthread_create_on_node(threadfn, data, cpu_to_mem(cpu), namefmt,
373 cpu);
374 if (IS_ERR(p))
375 return p;
376 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
377 to_kthread(p)->cpu = cpu;
378 /* Park the thread to get it out of TASK_UNINTERRUPTIBLE state */
379 kthread_park(p);
380 return p;
381}
382
383static void __kthread_unpark(struct task_struct *k, struct kthread *kthread)
384{
385 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
386 /*
387 * We clear the IS_PARKED bit here as we don't wait
388 * until the task has left the park code. So if we'd
389 * park before that happens we'd see the IS_PARKED bit
390 * which might be about to be cleared.
391 */
392 if (test_and_clear_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
393 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
394 __kthread_bind(k, kthread->cpu, TASK_PARKED);
395 wake_up_state(k, TASK_PARKED);
396 }
397}
398
399/**
400 * kthread_unpark - unpark a thread created by kthread_create().
401 * @k: thread created by kthread_create().
402 *
403 * Sets kthread_should_park() for @k to return false, wakes it, and
404 * waits for it to return. If the thread is marked percpu then its
405 * bound to the cpu again.
406 */
407void kthread_unpark(struct task_struct *k)
408{
409 struct kthread *kthread = to_live_kthread(k);
410
411 if (kthread)
412 __kthread_unpark(k, kthread);
413}
414
415/**
416 * kthread_park - park a thread created by kthread_create().
417 * @k: thread created by kthread_create().
418 *
419 * Sets kthread_should_park() for @k to return true, wakes it, and
420 * waits for it to return. This can also be called after kthread_create()
421 * instead of calling wake_up_process(): the thread will park without
422 * calling threadfn().
423 *
424 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
425 * If called by the kthread itself just the park bit is set.
426 */
427int kthread_park(struct task_struct *k)
428{
429 struct kthread *kthread = to_live_kthread(k);
430 int ret = -ENOSYS;
431
432 if (kthread) {
433 if (!test_bit(KTHREAD_IS_PARKED, &kthread->flags)) {
434 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
435 if (k != current) {
436 wake_up_process(k);
437 wait_for_completion(&kthread->parked);
438 }
439 }
440 ret = 0;
441 }
442 return ret;
443}
444
445/**
446 * kthread_stop - stop a thread created by kthread_create().
447 * @k: thread created by kthread_create().
448 *
449 * Sets kthread_should_stop() for @k to return true, wakes it, and
450 * waits for it to exit. This can also be called after kthread_create()
451 * instead of calling wake_up_process(): the thread will exit without
452 * calling threadfn().
453 *
454 * If threadfn() may call do_exit() itself, the caller must ensure
455 * task_struct can't go away.
456 *
457 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
458 * was never called.
459 */
460int kthread_stop(struct task_struct *k)
461{
462 struct kthread *kthread;
463 int ret;
464
465 trace_sched_kthread_stop(k);
466
467 get_task_struct(k);
468 kthread = to_live_kthread(k);
469 if (kthread) {
470 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
471 __kthread_unpark(k, kthread);
472 wake_up_process(k);
473 wait_for_completion(&kthread->exited);
474 }
475 ret = k->exit_code;
476 put_task_struct(k);
477
478 trace_sched_kthread_stop_ret(ret);
479 return ret;
480}
481EXPORT_SYMBOL(kthread_stop);
482
483int kthreadd(void *unused)
484{
485 struct task_struct *tsk = current;
486
487 /* Setup a clean context for our children to inherit. */
488 set_task_comm(tsk, "kthreadd");
489 ignore_signals(tsk);
490 set_cpus_allowed_ptr(tsk, cpu_all_mask);
491 set_mems_allowed(node_states[N_MEMORY]);
492
493 current->flags |= PF_NOFREEZE;
494
495 for (;;) {
496 set_current_state(TASK_INTERRUPTIBLE);
497 if (list_empty(&kthread_create_list))
498 schedule();
499 __set_current_state(TASK_RUNNING);
500
501 spin_lock(&kthread_create_lock);
502 while (!list_empty(&kthread_create_list)) {
503 struct kthread_create_info *create;
504
505 create = list_entry(kthread_create_list.next,
506 struct kthread_create_info, list);
507 list_del_init(&create->list);
508 spin_unlock(&kthread_create_lock);
509
510 create_kthread(create);
511
512 spin_lock(&kthread_create_lock);
513 }
514 spin_unlock(&kthread_create_lock);
515 }
516
517 return 0;
518}
519
520void __init_kthread_worker(struct kthread_worker *worker,
521 const char *name,
522 struct lock_class_key *key)
523{
524 spin_lock_init(&worker->lock);
525 lockdep_set_class_and_name(&worker->lock, key, name);
526 INIT_LIST_HEAD(&worker->work_list);
527 worker->task = NULL;
528}
529EXPORT_SYMBOL_GPL(__init_kthread_worker);
530
531/**
532 * kthread_worker_fn - kthread function to process kthread_worker
533 * @worker_ptr: pointer to initialized kthread_worker
534 *
535 * This function can be used as @threadfn to kthread_create() or
536 * kthread_run() with @worker_ptr argument pointing to an initialized
537 * kthread_worker. The started kthread will process work_list until
538 * the it is stopped with kthread_stop(). A kthread can also call
539 * this function directly after extra initialization.
540 *
541 * Different kthreads can be used for the same kthread_worker as long
542 * as there's only one kthread attached to it at any given time. A
543 * kthread_worker without an attached kthread simply collects queued
544 * kthread_works.
545 */
546int kthread_worker_fn(void *worker_ptr)
547{
548 struct kthread_worker *worker = worker_ptr;
549 struct kthread_work *work;
550
551 WARN_ON(worker->task);
552 worker->task = current;
553repeat:
554 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
555
556 if (kthread_should_stop()) {
557 __set_current_state(TASK_RUNNING);
558 spin_lock_irq(&worker->lock);
559 worker->task = NULL;
560 spin_unlock_irq(&worker->lock);
561 return 0;
562 }
563
564 work = NULL;
565 spin_lock_irq(&worker->lock);
566 if (!list_empty(&worker->work_list)) {
567 work = list_first_entry(&worker->work_list,
568 struct kthread_work, node);
569 list_del_init(&work->node);
570 }
571 worker->current_work = work;
572 spin_unlock_irq(&worker->lock);
573
574 if (work) {
575 __set_current_state(TASK_RUNNING);
576 work->func(work);
577 } else if (!freezing(current))
578 schedule();
579
580 try_to_freeze();
581 goto repeat;
582}
583EXPORT_SYMBOL_GPL(kthread_worker_fn);
584
585/* insert @work before @pos in @worker */
586static void insert_kthread_work(struct kthread_worker *worker,
587 struct kthread_work *work,
588 struct list_head *pos)
589{
590 lockdep_assert_held(&worker->lock);
591
592 list_add_tail(&work->node, pos);
593 work->worker = worker;
594 if (likely(worker->task))
595 wake_up_process(worker->task);
596}
597
598/**
599 * queue_kthread_work - queue a kthread_work
600 * @worker: target kthread_worker
601 * @work: kthread_work to queue
602 *
603 * Queue @work to work processor @task for async execution. @task
604 * must have been created with kthread_worker_create(). Returns %true
605 * if @work was successfully queued, %false if it was already pending.
606 */
607bool queue_kthread_work(struct kthread_worker *worker,
608 struct kthread_work *work)
609{
610 bool ret = false;
611 unsigned long flags;
612
613 spin_lock_irqsave(&worker->lock, flags);
614 if (list_empty(&work->node)) {
615 insert_kthread_work(worker, work, &worker->work_list);
616 ret = true;
617 }
618 spin_unlock_irqrestore(&worker->lock, flags);
619 return ret;
620}
621EXPORT_SYMBOL_GPL(queue_kthread_work);
622
623struct kthread_flush_work {
624 struct kthread_work work;
625 struct completion done;
626};
627
628static void kthread_flush_work_fn(struct kthread_work *work)
629{
630 struct kthread_flush_work *fwork =
631 container_of(work, struct kthread_flush_work, work);
632 complete(&fwork->done);
633}
634
635/**
636 * flush_kthread_work - flush a kthread_work
637 * @work: work to flush
638 *
639 * If @work is queued or executing, wait for it to finish execution.
640 */
641void flush_kthread_work(struct kthread_work *work)
642{
643 struct kthread_flush_work fwork = {
644 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
645 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
646 };
647 struct kthread_worker *worker;
648 bool noop = false;
649
650retry:
651 worker = work->worker;
652 if (!worker)
653 return;
654
655 spin_lock_irq(&worker->lock);
656 if (work->worker != worker) {
657 spin_unlock_irq(&worker->lock);
658 goto retry;
659 }
660
661 if (!list_empty(&work->node))
662 insert_kthread_work(worker, &fwork.work, work->node.next);
663 else if (worker->current_work == work)
664 insert_kthread_work(worker, &fwork.work, worker->work_list.next);
665 else
666 noop = true;
667
668 spin_unlock_irq(&worker->lock);
669
670 if (!noop)
671 wait_for_completion(&fwork.done);
672}
673EXPORT_SYMBOL_GPL(flush_kthread_work);
674
675/**
676 * flush_kthread_worker - flush all current works on a kthread_worker
677 * @worker: worker to flush
678 *
679 * Wait until all currently executing or pending works on @worker are
680 * finished.
681 */
682void flush_kthread_worker(struct kthread_worker *worker)
683{
684 struct kthread_flush_work fwork = {
685 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
686 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
687 };
688
689 queue_kthread_work(worker, &fwork.work);
690 wait_for_completion(&fwork.done);
691}
692EXPORT_SYMBOL_GPL(flush_kthread_worker);
1// SPDX-License-Identifier: GPL-2.0-only
2/* Kernel thread helper functions.
3 * Copyright (C) 2004 IBM Corporation, Rusty Russell.
4 * Copyright (C) 2009 Red Hat, Inc.
5 *
6 * Creation is done via kthreadd, so that we get a clean environment
7 * even if we're invoked from userspace (think modprobe, hotplug cpu,
8 * etc.).
9 */
10#include <uapi/linux/sched/types.h>
11#include <linux/mm.h>
12#include <linux/mmu_context.h>
13#include <linux/sched.h>
14#include <linux/sched/mm.h>
15#include <linux/sched/task.h>
16#include <linux/kthread.h>
17#include <linux/completion.h>
18#include <linux/err.h>
19#include <linux/cgroup.h>
20#include <linux/cpuset.h>
21#include <linux/unistd.h>
22#include <linux/file.h>
23#include <linux/export.h>
24#include <linux/mutex.h>
25#include <linux/slab.h>
26#include <linux/freezer.h>
27#include <linux/ptrace.h>
28#include <linux/uaccess.h>
29#include <linux/numa.h>
30#include <linux/sched/isolation.h>
31#include <trace/events/sched.h>
32
33
34static DEFINE_SPINLOCK(kthread_create_lock);
35static LIST_HEAD(kthread_create_list);
36struct task_struct *kthreadd_task;
37
38struct kthread_create_info
39{
40 /* Information passed to kthread() from kthreadd. */
41 int (*threadfn)(void *data);
42 void *data;
43 int node;
44
45 /* Result passed back to kthread_create() from kthreadd. */
46 struct task_struct *result;
47 struct completion *done;
48
49 struct list_head list;
50};
51
52struct kthread {
53 unsigned long flags;
54 unsigned int cpu;
55 int (*threadfn)(void *);
56 void *data;
57 mm_segment_t oldfs;
58 struct completion parked;
59 struct completion exited;
60#ifdef CONFIG_BLK_CGROUP
61 struct cgroup_subsys_state *blkcg_css;
62#endif
63};
64
65enum KTHREAD_BITS {
66 KTHREAD_IS_PER_CPU = 0,
67 KTHREAD_SHOULD_STOP,
68 KTHREAD_SHOULD_PARK,
69};
70
71static inline void set_kthread_struct(void *kthread)
72{
73 /*
74 * We abuse ->set_child_tid to avoid the new member and because it
75 * can't be wrongly copied by copy_process(). We also rely on fact
76 * that the caller can't exec, so PF_KTHREAD can't be cleared.
77 */
78 current->set_child_tid = (__force void __user *)kthread;
79}
80
81static inline struct kthread *to_kthread(struct task_struct *k)
82{
83 WARN_ON(!(k->flags & PF_KTHREAD));
84 return (__force void *)k->set_child_tid;
85}
86
87void free_kthread_struct(struct task_struct *k)
88{
89 struct kthread *kthread;
90
91 /*
92 * Can be NULL if this kthread was created by kernel_thread()
93 * or if kmalloc() in kthread() failed.
94 */
95 kthread = to_kthread(k);
96#ifdef CONFIG_BLK_CGROUP
97 WARN_ON_ONCE(kthread && kthread->blkcg_css);
98#endif
99 kfree(kthread);
100}
101
102/**
103 * kthread_should_stop - should this kthread return now?
104 *
105 * When someone calls kthread_stop() on your kthread, it will be woken
106 * and this will return true. You should then return, and your return
107 * value will be passed through to kthread_stop().
108 */
109bool kthread_should_stop(void)
110{
111 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
112}
113EXPORT_SYMBOL(kthread_should_stop);
114
115bool __kthread_should_park(struct task_struct *k)
116{
117 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(k)->flags);
118}
119EXPORT_SYMBOL_GPL(__kthread_should_park);
120
121/**
122 * kthread_should_park - should this kthread park now?
123 *
124 * When someone calls kthread_park() on your kthread, it will be woken
125 * and this will return true. You should then do the necessary
126 * cleanup and call kthread_parkme()
127 *
128 * Similar to kthread_should_stop(), but this keeps the thread alive
129 * and in a park position. kthread_unpark() "restarts" the thread and
130 * calls the thread function again.
131 */
132bool kthread_should_park(void)
133{
134 return __kthread_should_park(current);
135}
136EXPORT_SYMBOL_GPL(kthread_should_park);
137
138/**
139 * kthread_freezable_should_stop - should this freezable kthread return now?
140 * @was_frozen: optional out parameter, indicates whether %current was frozen
141 *
142 * kthread_should_stop() for freezable kthreads, which will enter
143 * refrigerator if necessary. This function is safe from kthread_stop() /
144 * freezer deadlock and freezable kthreads should use this function instead
145 * of calling try_to_freeze() directly.
146 */
147bool kthread_freezable_should_stop(bool *was_frozen)
148{
149 bool frozen = false;
150
151 might_sleep();
152
153 if (unlikely(freezing(current)))
154 frozen = __refrigerator(true);
155
156 if (was_frozen)
157 *was_frozen = frozen;
158
159 return kthread_should_stop();
160}
161EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
162
163/**
164 * kthread_func - return the function specified on kthread creation
165 * @task: kthread task in question
166 *
167 * Returns NULL if the task is not a kthread.
168 */
169void *kthread_func(struct task_struct *task)
170{
171 if (task->flags & PF_KTHREAD)
172 return to_kthread(task)->threadfn;
173 return NULL;
174}
175EXPORT_SYMBOL_GPL(kthread_func);
176
177/**
178 * kthread_data - return data value specified on kthread creation
179 * @task: kthread task in question
180 *
181 * Return the data value specified when kthread @task was created.
182 * The caller is responsible for ensuring the validity of @task when
183 * calling this function.
184 */
185void *kthread_data(struct task_struct *task)
186{
187 return to_kthread(task)->data;
188}
189EXPORT_SYMBOL_GPL(kthread_data);
190
191/**
192 * kthread_probe_data - speculative version of kthread_data()
193 * @task: possible kthread task in question
194 *
195 * @task could be a kthread task. Return the data value specified when it
196 * was created if accessible. If @task isn't a kthread task or its data is
197 * inaccessible for any reason, %NULL is returned. This function requires
198 * that @task itself is safe to dereference.
199 */
200void *kthread_probe_data(struct task_struct *task)
201{
202 struct kthread *kthread = to_kthread(task);
203 void *data = NULL;
204
205 copy_from_kernel_nofault(&data, &kthread->data, sizeof(data));
206 return data;
207}
208
209static void __kthread_parkme(struct kthread *self)
210{
211 for (;;) {
212 /*
213 * TASK_PARKED is a special state; we must serialize against
214 * possible pending wakeups to avoid store-store collisions on
215 * task->state.
216 *
217 * Such a collision might possibly result in the task state
218 * changin from TASK_PARKED and us failing the
219 * wait_task_inactive() in kthread_park().
220 */
221 set_special_state(TASK_PARKED);
222 if (!test_bit(KTHREAD_SHOULD_PARK, &self->flags))
223 break;
224
225 /*
226 * Thread is going to call schedule(), do not preempt it,
227 * or the caller of kthread_park() may spend more time in
228 * wait_task_inactive().
229 */
230 preempt_disable();
231 complete(&self->parked);
232 schedule_preempt_disabled();
233 preempt_enable();
234 }
235 __set_current_state(TASK_RUNNING);
236}
237
238void kthread_parkme(void)
239{
240 __kthread_parkme(to_kthread(current));
241}
242EXPORT_SYMBOL_GPL(kthread_parkme);
243
244static int kthread(void *_create)
245{
246 /* Copy data: it's on kthread's stack */
247 struct kthread_create_info *create = _create;
248 int (*threadfn)(void *data) = create->threadfn;
249 void *data = create->data;
250 struct completion *done;
251 struct kthread *self;
252 int ret;
253
254 self = kzalloc(sizeof(*self), GFP_KERNEL);
255 set_kthread_struct(self);
256
257 /* If user was SIGKILLed, I release the structure. */
258 done = xchg(&create->done, NULL);
259 if (!done) {
260 kfree(create);
261 do_exit(-EINTR);
262 }
263
264 if (!self) {
265 create->result = ERR_PTR(-ENOMEM);
266 complete(done);
267 do_exit(-ENOMEM);
268 }
269
270 self->threadfn = threadfn;
271 self->data = data;
272 init_completion(&self->exited);
273 init_completion(&self->parked);
274 current->vfork_done = &self->exited;
275
276 /* OK, tell user we're spawned, wait for stop or wakeup */
277 __set_current_state(TASK_UNINTERRUPTIBLE);
278 create->result = current;
279 /*
280 * Thread is going to call schedule(), do not preempt it,
281 * or the creator may spend more time in wait_task_inactive().
282 */
283 preempt_disable();
284 complete(done);
285 schedule_preempt_disabled();
286 preempt_enable();
287
288 ret = -EINTR;
289 if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
290 cgroup_kthread_ready();
291 __kthread_parkme(self);
292 ret = threadfn(data);
293 }
294 do_exit(ret);
295}
296
297/* called from do_fork() to get node information for about to be created task */
298int tsk_fork_get_node(struct task_struct *tsk)
299{
300#ifdef CONFIG_NUMA
301 if (tsk == kthreadd_task)
302 return tsk->pref_node_fork;
303#endif
304 return NUMA_NO_NODE;
305}
306
307static void create_kthread(struct kthread_create_info *create)
308{
309 int pid;
310
311#ifdef CONFIG_NUMA
312 current->pref_node_fork = create->node;
313#endif
314 /* We want our own signal handler (we take no signals by default). */
315 pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
316 if (pid < 0) {
317 /* If user was SIGKILLed, I release the structure. */
318 struct completion *done = xchg(&create->done, NULL);
319
320 if (!done) {
321 kfree(create);
322 return;
323 }
324 create->result = ERR_PTR(pid);
325 complete(done);
326 }
327}
328
329static __printf(4, 0)
330struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
331 void *data, int node,
332 const char namefmt[],
333 va_list args)
334{
335 DECLARE_COMPLETION_ONSTACK(done);
336 struct task_struct *task;
337 struct kthread_create_info *create = kmalloc(sizeof(*create),
338 GFP_KERNEL);
339
340 if (!create)
341 return ERR_PTR(-ENOMEM);
342 create->threadfn = threadfn;
343 create->data = data;
344 create->node = node;
345 create->done = &done;
346
347 spin_lock(&kthread_create_lock);
348 list_add_tail(&create->list, &kthread_create_list);
349 spin_unlock(&kthread_create_lock);
350
351 wake_up_process(kthreadd_task);
352 /*
353 * Wait for completion in killable state, for I might be chosen by
354 * the OOM killer while kthreadd is trying to allocate memory for
355 * new kernel thread.
356 */
357 if (unlikely(wait_for_completion_killable(&done))) {
358 /*
359 * If I was SIGKILLed before kthreadd (or new kernel thread)
360 * calls complete(), leave the cleanup of this structure to
361 * that thread.
362 */
363 if (xchg(&create->done, NULL))
364 return ERR_PTR(-EINTR);
365 /*
366 * kthreadd (or new kernel thread) will call complete()
367 * shortly.
368 */
369 wait_for_completion(&done);
370 }
371 task = create->result;
372 if (!IS_ERR(task)) {
373 static const struct sched_param param = { .sched_priority = 0 };
374 char name[TASK_COMM_LEN];
375
376 /*
377 * task is already visible to other tasks, so updating
378 * COMM must be protected.
379 */
380 vsnprintf(name, sizeof(name), namefmt, args);
381 set_task_comm(task, name);
382 /*
383 * root may have changed our (kthreadd's) priority or CPU mask.
384 * The kernel thread should not inherit these properties.
385 */
386 sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
387 set_cpus_allowed_ptr(task,
388 housekeeping_cpumask(HK_FLAG_KTHREAD));
389 }
390 kfree(create);
391 return task;
392}
393
394/**
395 * kthread_create_on_node - create a kthread.
396 * @threadfn: the function to run until signal_pending(current).
397 * @data: data ptr for @threadfn.
398 * @node: task and thread structures for the thread are allocated on this node
399 * @namefmt: printf-style name for the thread.
400 *
401 * Description: This helper function creates and names a kernel
402 * thread. The thread will be stopped: use wake_up_process() to start
403 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
404 * is affine to all CPUs.
405 *
406 * If thread is going to be bound on a particular cpu, give its node
407 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
408 * When woken, the thread will run @threadfn() with @data as its
409 * argument. @threadfn() can either call do_exit() directly if it is a
410 * standalone thread for which no one will call kthread_stop(), or
411 * return when 'kthread_should_stop()' is true (which means
412 * kthread_stop() has been called). The return value should be zero
413 * or a negative error number; it will be passed to kthread_stop().
414 *
415 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
416 */
417struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
418 void *data, int node,
419 const char namefmt[],
420 ...)
421{
422 struct task_struct *task;
423 va_list args;
424
425 va_start(args, namefmt);
426 task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
427 va_end(args);
428
429 return task;
430}
431EXPORT_SYMBOL(kthread_create_on_node);
432
433static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
434{
435 unsigned long flags;
436
437 if (!wait_task_inactive(p, state)) {
438 WARN_ON(1);
439 return;
440 }
441
442 /* It's safe because the task is inactive. */
443 raw_spin_lock_irqsave(&p->pi_lock, flags);
444 do_set_cpus_allowed(p, mask);
445 p->flags |= PF_NO_SETAFFINITY;
446 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
447}
448
449static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
450{
451 __kthread_bind_mask(p, cpumask_of(cpu), state);
452}
453
454void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
455{
456 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
457}
458
459/**
460 * kthread_bind - bind a just-created kthread to a cpu.
461 * @p: thread created by kthread_create().
462 * @cpu: cpu (might not be online, must be possible) for @k to run on.
463 *
464 * Description: This function is equivalent to set_cpus_allowed(),
465 * except that @cpu doesn't need to be online, and the thread must be
466 * stopped (i.e., just returned from kthread_create()).
467 */
468void kthread_bind(struct task_struct *p, unsigned int cpu)
469{
470 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
471}
472EXPORT_SYMBOL(kthread_bind);
473
474/**
475 * kthread_create_on_cpu - Create a cpu bound kthread
476 * @threadfn: the function to run until signal_pending(current).
477 * @data: data ptr for @threadfn.
478 * @cpu: The cpu on which the thread should be bound,
479 * @namefmt: printf-style name for the thread. Format is restricted
480 * to "name.*%u". Code fills in cpu number.
481 *
482 * Description: This helper function creates and names a kernel thread
483 */
484struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
485 void *data, unsigned int cpu,
486 const char *namefmt)
487{
488 struct task_struct *p;
489
490 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
491 cpu);
492 if (IS_ERR(p))
493 return p;
494 kthread_bind(p, cpu);
495 /* CPU hotplug need to bind once again when unparking the thread. */
496 set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags);
497 to_kthread(p)->cpu = cpu;
498 return p;
499}
500
501/**
502 * kthread_unpark - unpark a thread created by kthread_create().
503 * @k: thread created by kthread_create().
504 *
505 * Sets kthread_should_park() for @k to return false, wakes it, and
506 * waits for it to return. If the thread is marked percpu then its
507 * bound to the cpu again.
508 */
509void kthread_unpark(struct task_struct *k)
510{
511 struct kthread *kthread = to_kthread(k);
512
513 /*
514 * Newly created kthread was parked when the CPU was offline.
515 * The binding was lost and we need to set it again.
516 */
517 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
518 __kthread_bind(k, kthread->cpu, TASK_PARKED);
519
520 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
521 /*
522 * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup.
523 */
524 wake_up_state(k, TASK_PARKED);
525}
526EXPORT_SYMBOL_GPL(kthread_unpark);
527
528/**
529 * kthread_park - park a thread created by kthread_create().
530 * @k: thread created by kthread_create().
531 *
532 * Sets kthread_should_park() for @k to return true, wakes it, and
533 * waits for it to return. This can also be called after kthread_create()
534 * instead of calling wake_up_process(): the thread will park without
535 * calling threadfn().
536 *
537 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
538 * If called by the kthread itself just the park bit is set.
539 */
540int kthread_park(struct task_struct *k)
541{
542 struct kthread *kthread = to_kthread(k);
543
544 if (WARN_ON(k->flags & PF_EXITING))
545 return -ENOSYS;
546
547 if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK, &kthread->flags)))
548 return -EBUSY;
549
550 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
551 if (k != current) {
552 wake_up_process(k);
553 /*
554 * Wait for __kthread_parkme() to complete(), this means we
555 * _will_ have TASK_PARKED and are about to call schedule().
556 */
557 wait_for_completion(&kthread->parked);
558 /*
559 * Now wait for that schedule() to complete and the task to
560 * get scheduled out.
561 */
562 WARN_ON_ONCE(!wait_task_inactive(k, TASK_PARKED));
563 }
564
565 return 0;
566}
567EXPORT_SYMBOL_GPL(kthread_park);
568
569/**
570 * kthread_stop - stop a thread created by kthread_create().
571 * @k: thread created by kthread_create().
572 *
573 * Sets kthread_should_stop() for @k to return true, wakes it, and
574 * waits for it to exit. This can also be called after kthread_create()
575 * instead of calling wake_up_process(): the thread will exit without
576 * calling threadfn().
577 *
578 * If threadfn() may call do_exit() itself, the caller must ensure
579 * task_struct can't go away.
580 *
581 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
582 * was never called.
583 */
584int kthread_stop(struct task_struct *k)
585{
586 struct kthread *kthread;
587 int ret;
588
589 trace_sched_kthread_stop(k);
590
591 get_task_struct(k);
592 kthread = to_kthread(k);
593 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
594 kthread_unpark(k);
595 wake_up_process(k);
596 wait_for_completion(&kthread->exited);
597 ret = k->exit_code;
598 put_task_struct(k);
599
600 trace_sched_kthread_stop_ret(ret);
601 return ret;
602}
603EXPORT_SYMBOL(kthread_stop);
604
605int kthreadd(void *unused)
606{
607 struct task_struct *tsk = current;
608
609 /* Setup a clean context for our children to inherit. */
610 set_task_comm(tsk, "kthreadd");
611 ignore_signals(tsk);
612 set_cpus_allowed_ptr(tsk, housekeeping_cpumask(HK_FLAG_KTHREAD));
613 set_mems_allowed(node_states[N_MEMORY]);
614
615 current->flags |= PF_NOFREEZE;
616 cgroup_init_kthreadd();
617
618 for (;;) {
619 set_current_state(TASK_INTERRUPTIBLE);
620 if (list_empty(&kthread_create_list))
621 schedule();
622 __set_current_state(TASK_RUNNING);
623
624 spin_lock(&kthread_create_lock);
625 while (!list_empty(&kthread_create_list)) {
626 struct kthread_create_info *create;
627
628 create = list_entry(kthread_create_list.next,
629 struct kthread_create_info, list);
630 list_del_init(&create->list);
631 spin_unlock(&kthread_create_lock);
632
633 create_kthread(create);
634
635 spin_lock(&kthread_create_lock);
636 }
637 spin_unlock(&kthread_create_lock);
638 }
639
640 return 0;
641}
642
643void __kthread_init_worker(struct kthread_worker *worker,
644 const char *name,
645 struct lock_class_key *key)
646{
647 memset(worker, 0, sizeof(struct kthread_worker));
648 raw_spin_lock_init(&worker->lock);
649 lockdep_set_class_and_name(&worker->lock, key, name);
650 INIT_LIST_HEAD(&worker->work_list);
651 INIT_LIST_HEAD(&worker->delayed_work_list);
652}
653EXPORT_SYMBOL_GPL(__kthread_init_worker);
654
655/**
656 * kthread_worker_fn - kthread function to process kthread_worker
657 * @worker_ptr: pointer to initialized kthread_worker
658 *
659 * This function implements the main cycle of kthread worker. It processes
660 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
661 * is empty.
662 *
663 * The works are not allowed to keep any locks, disable preemption or interrupts
664 * when they finish. There is defined a safe point for freezing when one work
665 * finishes and before a new one is started.
666 *
667 * Also the works must not be handled by more than one worker at the same time,
668 * see also kthread_queue_work().
669 */
670int kthread_worker_fn(void *worker_ptr)
671{
672 struct kthread_worker *worker = worker_ptr;
673 struct kthread_work *work;
674
675 /*
676 * FIXME: Update the check and remove the assignment when all kthread
677 * worker users are created using kthread_create_worker*() functions.
678 */
679 WARN_ON(worker->task && worker->task != current);
680 worker->task = current;
681
682 if (worker->flags & KTW_FREEZABLE)
683 set_freezable();
684
685repeat:
686 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
687
688 if (kthread_should_stop()) {
689 __set_current_state(TASK_RUNNING);
690 raw_spin_lock_irq(&worker->lock);
691 worker->task = NULL;
692 raw_spin_unlock_irq(&worker->lock);
693 return 0;
694 }
695
696 work = NULL;
697 raw_spin_lock_irq(&worker->lock);
698 if (!list_empty(&worker->work_list)) {
699 work = list_first_entry(&worker->work_list,
700 struct kthread_work, node);
701 list_del_init(&work->node);
702 }
703 worker->current_work = work;
704 raw_spin_unlock_irq(&worker->lock);
705
706 if (work) {
707 __set_current_state(TASK_RUNNING);
708 work->func(work);
709 } else if (!freezing(current))
710 schedule();
711
712 try_to_freeze();
713 cond_resched();
714 goto repeat;
715}
716EXPORT_SYMBOL_GPL(kthread_worker_fn);
717
718static __printf(3, 0) struct kthread_worker *
719__kthread_create_worker(int cpu, unsigned int flags,
720 const char namefmt[], va_list args)
721{
722 struct kthread_worker *worker;
723 struct task_struct *task;
724 int node = NUMA_NO_NODE;
725
726 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
727 if (!worker)
728 return ERR_PTR(-ENOMEM);
729
730 kthread_init_worker(worker);
731
732 if (cpu >= 0)
733 node = cpu_to_node(cpu);
734
735 task = __kthread_create_on_node(kthread_worker_fn, worker,
736 node, namefmt, args);
737 if (IS_ERR(task))
738 goto fail_task;
739
740 if (cpu >= 0)
741 kthread_bind(task, cpu);
742
743 worker->flags = flags;
744 worker->task = task;
745 wake_up_process(task);
746 return worker;
747
748fail_task:
749 kfree(worker);
750 return ERR_CAST(task);
751}
752
753/**
754 * kthread_create_worker - create a kthread worker
755 * @flags: flags modifying the default behavior of the worker
756 * @namefmt: printf-style name for the kthread worker (task).
757 *
758 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
759 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
760 * when the worker was SIGKILLed.
761 */
762struct kthread_worker *
763kthread_create_worker(unsigned int flags, const char namefmt[], ...)
764{
765 struct kthread_worker *worker;
766 va_list args;
767
768 va_start(args, namefmt);
769 worker = __kthread_create_worker(-1, flags, namefmt, args);
770 va_end(args);
771
772 return worker;
773}
774EXPORT_SYMBOL(kthread_create_worker);
775
776/**
777 * kthread_create_worker_on_cpu - create a kthread worker and bind it
778 * it to a given CPU and the associated NUMA node.
779 * @cpu: CPU number
780 * @flags: flags modifying the default behavior of the worker
781 * @namefmt: printf-style name for the kthread worker (task).
782 *
783 * Use a valid CPU number if you want to bind the kthread worker
784 * to the given CPU and the associated NUMA node.
785 *
786 * A good practice is to add the cpu number also into the worker name.
787 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
788 *
789 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
790 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
791 * when the worker was SIGKILLed.
792 */
793struct kthread_worker *
794kthread_create_worker_on_cpu(int cpu, unsigned int flags,
795 const char namefmt[], ...)
796{
797 struct kthread_worker *worker;
798 va_list args;
799
800 va_start(args, namefmt);
801 worker = __kthread_create_worker(cpu, flags, namefmt, args);
802 va_end(args);
803
804 return worker;
805}
806EXPORT_SYMBOL(kthread_create_worker_on_cpu);
807
808/*
809 * Returns true when the work could not be queued at the moment.
810 * It happens when it is already pending in a worker list
811 * or when it is being cancelled.
812 */
813static inline bool queuing_blocked(struct kthread_worker *worker,
814 struct kthread_work *work)
815{
816 lockdep_assert_held(&worker->lock);
817
818 return !list_empty(&work->node) || work->canceling;
819}
820
821static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
822 struct kthread_work *work)
823{
824 lockdep_assert_held(&worker->lock);
825 WARN_ON_ONCE(!list_empty(&work->node));
826 /* Do not use a work with >1 worker, see kthread_queue_work() */
827 WARN_ON_ONCE(work->worker && work->worker != worker);
828}
829
830/* insert @work before @pos in @worker */
831static void kthread_insert_work(struct kthread_worker *worker,
832 struct kthread_work *work,
833 struct list_head *pos)
834{
835 kthread_insert_work_sanity_check(worker, work);
836
837 list_add_tail(&work->node, pos);
838 work->worker = worker;
839 if (!worker->current_work && likely(worker->task))
840 wake_up_process(worker->task);
841}
842
843/**
844 * kthread_queue_work - queue a kthread_work
845 * @worker: target kthread_worker
846 * @work: kthread_work to queue
847 *
848 * Queue @work to work processor @task for async execution. @task
849 * must have been created with kthread_worker_create(). Returns %true
850 * if @work was successfully queued, %false if it was already pending.
851 *
852 * Reinitialize the work if it needs to be used by another worker.
853 * For example, when the worker was stopped and started again.
854 */
855bool kthread_queue_work(struct kthread_worker *worker,
856 struct kthread_work *work)
857{
858 bool ret = false;
859 unsigned long flags;
860
861 raw_spin_lock_irqsave(&worker->lock, flags);
862 if (!queuing_blocked(worker, work)) {
863 kthread_insert_work(worker, work, &worker->work_list);
864 ret = true;
865 }
866 raw_spin_unlock_irqrestore(&worker->lock, flags);
867 return ret;
868}
869EXPORT_SYMBOL_GPL(kthread_queue_work);
870
871/**
872 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
873 * delayed work when the timer expires.
874 * @t: pointer to the expired timer
875 *
876 * The format of the function is defined by struct timer_list.
877 * It should have been called from irqsafe timer with irq already off.
878 */
879void kthread_delayed_work_timer_fn(struct timer_list *t)
880{
881 struct kthread_delayed_work *dwork = from_timer(dwork, t, timer);
882 struct kthread_work *work = &dwork->work;
883 struct kthread_worker *worker = work->worker;
884 unsigned long flags;
885
886 /*
887 * This might happen when a pending work is reinitialized.
888 * It means that it is used a wrong way.
889 */
890 if (WARN_ON_ONCE(!worker))
891 return;
892
893 raw_spin_lock_irqsave(&worker->lock, flags);
894 /* Work must not be used with >1 worker, see kthread_queue_work(). */
895 WARN_ON_ONCE(work->worker != worker);
896
897 /* Move the work from worker->delayed_work_list. */
898 WARN_ON_ONCE(list_empty(&work->node));
899 list_del_init(&work->node);
900 kthread_insert_work(worker, work, &worker->work_list);
901
902 raw_spin_unlock_irqrestore(&worker->lock, flags);
903}
904EXPORT_SYMBOL(kthread_delayed_work_timer_fn);
905
906static void __kthread_queue_delayed_work(struct kthread_worker *worker,
907 struct kthread_delayed_work *dwork,
908 unsigned long delay)
909{
910 struct timer_list *timer = &dwork->timer;
911 struct kthread_work *work = &dwork->work;
912
913 WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);
914
915 /*
916 * If @delay is 0, queue @dwork->work immediately. This is for
917 * both optimization and correctness. The earliest @timer can
918 * expire is on the closest next tick and delayed_work users depend
919 * on that there's no such delay when @delay is 0.
920 */
921 if (!delay) {
922 kthread_insert_work(worker, work, &worker->work_list);
923 return;
924 }
925
926 /* Be paranoid and try to detect possible races already now. */
927 kthread_insert_work_sanity_check(worker, work);
928
929 list_add(&work->node, &worker->delayed_work_list);
930 work->worker = worker;
931 timer->expires = jiffies + delay;
932 add_timer(timer);
933}
934
935/**
936 * kthread_queue_delayed_work - queue the associated kthread work
937 * after a delay.
938 * @worker: target kthread_worker
939 * @dwork: kthread_delayed_work to queue
940 * @delay: number of jiffies to wait before queuing
941 *
942 * If the work has not been pending it starts a timer that will queue
943 * the work after the given @delay. If @delay is zero, it queues the
944 * work immediately.
945 *
946 * Return: %false if the @work has already been pending. It means that
947 * either the timer was running or the work was queued. It returns %true
948 * otherwise.
949 */
950bool kthread_queue_delayed_work(struct kthread_worker *worker,
951 struct kthread_delayed_work *dwork,
952 unsigned long delay)
953{
954 struct kthread_work *work = &dwork->work;
955 unsigned long flags;
956 bool ret = false;
957
958 raw_spin_lock_irqsave(&worker->lock, flags);
959
960 if (!queuing_blocked(worker, work)) {
961 __kthread_queue_delayed_work(worker, dwork, delay);
962 ret = true;
963 }
964
965 raw_spin_unlock_irqrestore(&worker->lock, flags);
966 return ret;
967}
968EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
969
970struct kthread_flush_work {
971 struct kthread_work work;
972 struct completion done;
973};
974
975static void kthread_flush_work_fn(struct kthread_work *work)
976{
977 struct kthread_flush_work *fwork =
978 container_of(work, struct kthread_flush_work, work);
979 complete(&fwork->done);
980}
981
982/**
983 * kthread_flush_work - flush a kthread_work
984 * @work: work to flush
985 *
986 * If @work is queued or executing, wait for it to finish execution.
987 */
988void kthread_flush_work(struct kthread_work *work)
989{
990 struct kthread_flush_work fwork = {
991 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
992 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
993 };
994 struct kthread_worker *worker;
995 bool noop = false;
996
997 worker = work->worker;
998 if (!worker)
999 return;
1000
1001 raw_spin_lock_irq(&worker->lock);
1002 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1003 WARN_ON_ONCE(work->worker != worker);
1004
1005 if (!list_empty(&work->node))
1006 kthread_insert_work(worker, &fwork.work, work->node.next);
1007 else if (worker->current_work == work)
1008 kthread_insert_work(worker, &fwork.work,
1009 worker->work_list.next);
1010 else
1011 noop = true;
1012
1013 raw_spin_unlock_irq(&worker->lock);
1014
1015 if (!noop)
1016 wait_for_completion(&fwork.done);
1017}
1018EXPORT_SYMBOL_GPL(kthread_flush_work);
1019
1020/*
1021 * This function removes the work from the worker queue. Also it makes sure
1022 * that it won't get queued later via the delayed work's timer.
1023 *
1024 * The work might still be in use when this function finishes. See the
1025 * current_work proceed by the worker.
1026 *
1027 * Return: %true if @work was pending and successfully canceled,
1028 * %false if @work was not pending
1029 */
1030static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
1031 unsigned long *flags)
1032{
1033 /* Try to cancel the timer if exists. */
1034 if (is_dwork) {
1035 struct kthread_delayed_work *dwork =
1036 container_of(work, struct kthread_delayed_work, work);
1037 struct kthread_worker *worker = work->worker;
1038
1039 /*
1040 * del_timer_sync() must be called to make sure that the timer
1041 * callback is not running. The lock must be temporary released
1042 * to avoid a deadlock with the callback. In the meantime,
1043 * any queuing is blocked by setting the canceling counter.
1044 */
1045 work->canceling++;
1046 raw_spin_unlock_irqrestore(&worker->lock, *flags);
1047 del_timer_sync(&dwork->timer);
1048 raw_spin_lock_irqsave(&worker->lock, *flags);
1049 work->canceling--;
1050 }
1051
1052 /*
1053 * Try to remove the work from a worker list. It might either
1054 * be from worker->work_list or from worker->delayed_work_list.
1055 */
1056 if (!list_empty(&work->node)) {
1057 list_del_init(&work->node);
1058 return true;
1059 }
1060
1061 return false;
1062}
1063
1064/**
1065 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1066 * @worker: kthread worker to use
1067 * @dwork: kthread delayed work to queue
1068 * @delay: number of jiffies to wait before queuing
1069 *
1070 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1071 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1072 * @work is guaranteed to be queued immediately.
1073 *
1074 * Return: %true if @dwork was pending and its timer was modified,
1075 * %false otherwise.
1076 *
1077 * A special case is when the work is being canceled in parallel.
1078 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1079 * or yet another kthread_mod_delayed_work() call. We let the other command
1080 * win and return %false here. The caller is supposed to synchronize these
1081 * operations a reasonable way.
1082 *
1083 * This function is safe to call from any context including IRQ handler.
1084 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1085 * for details.
1086 */
1087bool kthread_mod_delayed_work(struct kthread_worker *worker,
1088 struct kthread_delayed_work *dwork,
1089 unsigned long delay)
1090{
1091 struct kthread_work *work = &dwork->work;
1092 unsigned long flags;
1093 int ret = false;
1094
1095 raw_spin_lock_irqsave(&worker->lock, flags);
1096
1097 /* Do not bother with canceling when never queued. */
1098 if (!work->worker)
1099 goto fast_queue;
1100
1101 /* Work must not be used with >1 worker, see kthread_queue_work() */
1102 WARN_ON_ONCE(work->worker != worker);
1103
1104 /* Do not fight with another command that is canceling this work. */
1105 if (work->canceling)
1106 goto out;
1107
1108 ret = __kthread_cancel_work(work, true, &flags);
1109fast_queue:
1110 __kthread_queue_delayed_work(worker, dwork, delay);
1111out:
1112 raw_spin_unlock_irqrestore(&worker->lock, flags);
1113 return ret;
1114}
1115EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1116
1117static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1118{
1119 struct kthread_worker *worker = work->worker;
1120 unsigned long flags;
1121 int ret = false;
1122
1123 if (!worker)
1124 goto out;
1125
1126 raw_spin_lock_irqsave(&worker->lock, flags);
1127 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1128 WARN_ON_ONCE(work->worker != worker);
1129
1130 ret = __kthread_cancel_work(work, is_dwork, &flags);
1131
1132 if (worker->current_work != work)
1133 goto out_fast;
1134
1135 /*
1136 * The work is in progress and we need to wait with the lock released.
1137 * In the meantime, block any queuing by setting the canceling counter.
1138 */
1139 work->canceling++;
1140 raw_spin_unlock_irqrestore(&worker->lock, flags);
1141 kthread_flush_work(work);
1142 raw_spin_lock_irqsave(&worker->lock, flags);
1143 work->canceling--;
1144
1145out_fast:
1146 raw_spin_unlock_irqrestore(&worker->lock, flags);
1147out:
1148 return ret;
1149}
1150
1151/**
1152 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1153 * @work: the kthread work to cancel
1154 *
1155 * Cancel @work and wait for its execution to finish. This function
1156 * can be used even if the work re-queues itself. On return from this
1157 * function, @work is guaranteed to be not pending or executing on any CPU.
1158 *
1159 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1160 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1161 *
1162 * The caller must ensure that the worker on which @work was last
1163 * queued can't be destroyed before this function returns.
1164 *
1165 * Return: %true if @work was pending, %false otherwise.
1166 */
1167bool kthread_cancel_work_sync(struct kthread_work *work)
1168{
1169 return __kthread_cancel_work_sync(work, false);
1170}
1171EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1172
1173/**
1174 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1175 * wait for it to finish.
1176 * @dwork: the kthread delayed work to cancel
1177 *
1178 * This is kthread_cancel_work_sync() for delayed works.
1179 *
1180 * Return: %true if @dwork was pending, %false otherwise.
1181 */
1182bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1183{
1184 return __kthread_cancel_work_sync(&dwork->work, true);
1185}
1186EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1187
1188/**
1189 * kthread_flush_worker - flush all current works on a kthread_worker
1190 * @worker: worker to flush
1191 *
1192 * Wait until all currently executing or pending works on @worker are
1193 * finished.
1194 */
1195void kthread_flush_worker(struct kthread_worker *worker)
1196{
1197 struct kthread_flush_work fwork = {
1198 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1199 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1200 };
1201
1202 kthread_queue_work(worker, &fwork.work);
1203 wait_for_completion(&fwork.done);
1204}
1205EXPORT_SYMBOL_GPL(kthread_flush_worker);
1206
1207/**
1208 * kthread_destroy_worker - destroy a kthread worker
1209 * @worker: worker to be destroyed
1210 *
1211 * Flush and destroy @worker. The simple flush is enough because the kthread
1212 * worker API is used only in trivial scenarios. There are no multi-step state
1213 * machines needed.
1214 */
1215void kthread_destroy_worker(struct kthread_worker *worker)
1216{
1217 struct task_struct *task;
1218
1219 task = worker->task;
1220 if (WARN_ON(!task))
1221 return;
1222
1223 kthread_flush_worker(worker);
1224 kthread_stop(task);
1225 WARN_ON(!list_empty(&worker->work_list));
1226 kfree(worker);
1227}
1228EXPORT_SYMBOL(kthread_destroy_worker);
1229
1230/**
1231 * kthread_use_mm - make the calling kthread operate on an address space
1232 * @mm: address space to operate on
1233 */
1234void kthread_use_mm(struct mm_struct *mm)
1235{
1236 struct mm_struct *active_mm;
1237 struct task_struct *tsk = current;
1238
1239 WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
1240 WARN_ON_ONCE(tsk->mm);
1241
1242 task_lock(tsk);
1243 /* Hold off tlb flush IPIs while switching mm's */
1244 local_irq_disable();
1245 active_mm = tsk->active_mm;
1246 if (active_mm != mm) {
1247 mmgrab(mm);
1248 tsk->active_mm = mm;
1249 }
1250 tsk->mm = mm;
1251 switch_mm_irqs_off(active_mm, mm, tsk);
1252 local_irq_enable();
1253 task_unlock(tsk);
1254#ifdef finish_arch_post_lock_switch
1255 finish_arch_post_lock_switch();
1256#endif
1257
1258 if (active_mm != mm)
1259 mmdrop(active_mm);
1260
1261 to_kthread(tsk)->oldfs = force_uaccess_begin();
1262}
1263EXPORT_SYMBOL_GPL(kthread_use_mm);
1264
1265/**
1266 * kthread_unuse_mm - reverse the effect of kthread_use_mm()
1267 * @mm: address space to operate on
1268 */
1269void kthread_unuse_mm(struct mm_struct *mm)
1270{
1271 struct task_struct *tsk = current;
1272
1273 WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
1274 WARN_ON_ONCE(!tsk->mm);
1275
1276 force_uaccess_end(to_kthread(tsk)->oldfs);
1277
1278 task_lock(tsk);
1279 sync_mm_rss(mm);
1280 local_irq_disable();
1281 tsk->mm = NULL;
1282 /* active_mm is still 'mm' */
1283 enter_lazy_tlb(mm, tsk);
1284 local_irq_enable();
1285 task_unlock(tsk);
1286}
1287EXPORT_SYMBOL_GPL(kthread_unuse_mm);
1288
1289#ifdef CONFIG_BLK_CGROUP
1290/**
1291 * kthread_associate_blkcg - associate blkcg to current kthread
1292 * @css: the cgroup info
1293 *
1294 * Current thread must be a kthread. The thread is running jobs on behalf of
1295 * other threads. In some cases, we expect the jobs attach cgroup info of
1296 * original threads instead of that of current thread. This function stores
1297 * original thread's cgroup info in current kthread context for later
1298 * retrieval.
1299 */
1300void kthread_associate_blkcg(struct cgroup_subsys_state *css)
1301{
1302 struct kthread *kthread;
1303
1304 if (!(current->flags & PF_KTHREAD))
1305 return;
1306 kthread = to_kthread(current);
1307 if (!kthread)
1308 return;
1309
1310 if (kthread->blkcg_css) {
1311 css_put(kthread->blkcg_css);
1312 kthread->blkcg_css = NULL;
1313 }
1314 if (css) {
1315 css_get(css);
1316 kthread->blkcg_css = css;
1317 }
1318}
1319EXPORT_SYMBOL(kthread_associate_blkcg);
1320
1321/**
1322 * kthread_blkcg - get associated blkcg css of current kthread
1323 *
1324 * Current thread must be a kthread.
1325 */
1326struct cgroup_subsys_state *kthread_blkcg(void)
1327{
1328 struct kthread *kthread;
1329
1330 if (current->flags & PF_KTHREAD) {
1331 kthread = to_kthread(current);
1332 if (kthread)
1333 return kthread->blkcg_css;
1334 }
1335 return NULL;
1336}
1337EXPORT_SYMBOL(kthread_blkcg);
1338#endif