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