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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 * 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 char *full_name;
42 int (*threadfn)(void *data);
43 void *data;
44 int node;
45
46 /* Result passed back to kthread_create() from kthreadd. */
47 struct task_struct *result;
48 struct completion *done;
49
50 struct list_head list;
51};
52
53struct kthread {
54 unsigned long flags;
55 unsigned int cpu;
56 int result;
57 int (*threadfn)(void *);
58 void *data;
59 struct completion parked;
60 struct completion exited;
61#ifdef CONFIG_BLK_CGROUP
62 struct cgroup_subsys_state *blkcg_css;
63#endif
64 /* To store the full name if task comm is truncated. */
65 char *full_name;
66};
67
68enum KTHREAD_BITS {
69 KTHREAD_IS_PER_CPU = 0,
70 KTHREAD_SHOULD_STOP,
71 KTHREAD_SHOULD_PARK,
72};
73
74static inline struct kthread *to_kthread(struct task_struct *k)
75{
76 WARN_ON(!(k->flags & PF_KTHREAD));
77 return k->worker_private;
78}
79
80/*
81 * Variant of to_kthread() that doesn't assume @p is a kthread.
82 *
83 * Per construction; when:
84 *
85 * (p->flags & PF_KTHREAD) && p->worker_private
86 *
87 * the task is both a kthread and struct kthread is persistent. However
88 * PF_KTHREAD on it's own is not, kernel_thread() can exec() (See umh.c and
89 * begin_new_exec()).
90 */
91static inline struct kthread *__to_kthread(struct task_struct *p)
92{
93 void *kthread = p->worker_private;
94 if (kthread && !(p->flags & PF_KTHREAD))
95 kthread = NULL;
96 return kthread;
97}
98
99void get_kthread_comm(char *buf, size_t buf_size, struct task_struct *tsk)
100{
101 struct kthread *kthread = to_kthread(tsk);
102
103 if (!kthread || !kthread->full_name) {
104 __get_task_comm(buf, buf_size, tsk);
105 return;
106 }
107
108 strscpy_pad(buf, kthread->full_name, buf_size);
109}
110
111bool set_kthread_struct(struct task_struct *p)
112{
113 struct kthread *kthread;
114
115 if (WARN_ON_ONCE(to_kthread(p)))
116 return false;
117
118 kthread = kzalloc(sizeof(*kthread), GFP_KERNEL);
119 if (!kthread)
120 return false;
121
122 init_completion(&kthread->exited);
123 init_completion(&kthread->parked);
124 p->vfork_done = &kthread->exited;
125
126 p->worker_private = kthread;
127 return true;
128}
129
130void free_kthread_struct(struct task_struct *k)
131{
132 struct kthread *kthread;
133
134 /*
135 * Can be NULL if kmalloc() in set_kthread_struct() failed.
136 */
137 kthread = to_kthread(k);
138 if (!kthread)
139 return;
140
141#ifdef CONFIG_BLK_CGROUP
142 WARN_ON_ONCE(kthread->blkcg_css);
143#endif
144 k->worker_private = NULL;
145 kfree(kthread->full_name);
146 kfree(kthread);
147}
148
149/**
150 * kthread_should_stop - should this kthread return now?
151 *
152 * When someone calls kthread_stop() on your kthread, it will be woken
153 * and this will return true. You should then return, and your return
154 * value will be passed through to kthread_stop().
155 */
156bool kthread_should_stop(void)
157{
158 return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
159}
160EXPORT_SYMBOL(kthread_should_stop);
161
162static bool __kthread_should_park(struct task_struct *k)
163{
164 return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(k)->flags);
165}
166
167/**
168 * kthread_should_park - should this kthread park now?
169 *
170 * When someone calls kthread_park() on your kthread, it will be woken
171 * and this will return true. You should then do the necessary
172 * cleanup and call kthread_parkme()
173 *
174 * Similar to kthread_should_stop(), but this keeps the thread alive
175 * and in a park position. kthread_unpark() "restarts" the thread and
176 * calls the thread function again.
177 */
178bool kthread_should_park(void)
179{
180 return __kthread_should_park(current);
181}
182EXPORT_SYMBOL_GPL(kthread_should_park);
183
184bool kthread_should_stop_or_park(void)
185{
186 struct kthread *kthread = __to_kthread(current);
187
188 if (!kthread)
189 return false;
190
191 return kthread->flags & (BIT(KTHREAD_SHOULD_STOP) | BIT(KTHREAD_SHOULD_PARK));
192}
193
194/**
195 * kthread_freezable_should_stop - should this freezable kthread return now?
196 * @was_frozen: optional out parameter, indicates whether %current was frozen
197 *
198 * kthread_should_stop() for freezable kthreads, which will enter
199 * refrigerator if necessary. This function is safe from kthread_stop() /
200 * freezer deadlock and freezable kthreads should use this function instead
201 * of calling try_to_freeze() directly.
202 */
203bool kthread_freezable_should_stop(bool *was_frozen)
204{
205 bool frozen = false;
206
207 might_sleep();
208
209 if (unlikely(freezing(current)))
210 frozen = __refrigerator(true);
211
212 if (was_frozen)
213 *was_frozen = frozen;
214
215 return kthread_should_stop();
216}
217EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);
218
219/**
220 * kthread_func - return the function specified on kthread creation
221 * @task: kthread task in question
222 *
223 * Returns NULL if the task is not a kthread.
224 */
225void *kthread_func(struct task_struct *task)
226{
227 struct kthread *kthread = __to_kthread(task);
228 if (kthread)
229 return kthread->threadfn;
230 return NULL;
231}
232EXPORT_SYMBOL_GPL(kthread_func);
233
234/**
235 * kthread_data - return data value specified on kthread creation
236 * @task: kthread task in question
237 *
238 * Return the data value specified when kthread @task was created.
239 * The caller is responsible for ensuring the validity of @task when
240 * calling this function.
241 */
242void *kthread_data(struct task_struct *task)
243{
244 return to_kthread(task)->data;
245}
246EXPORT_SYMBOL_GPL(kthread_data);
247
248/**
249 * kthread_probe_data - speculative version of kthread_data()
250 * @task: possible kthread task in question
251 *
252 * @task could be a kthread task. Return the data value specified when it
253 * was created if accessible. If @task isn't a kthread task or its data is
254 * inaccessible for any reason, %NULL is returned. This function requires
255 * that @task itself is safe to dereference.
256 */
257void *kthread_probe_data(struct task_struct *task)
258{
259 struct kthread *kthread = __to_kthread(task);
260 void *data = NULL;
261
262 if (kthread)
263 copy_from_kernel_nofault(&data, &kthread->data, sizeof(data));
264 return data;
265}
266
267static void __kthread_parkme(struct kthread *self)
268{
269 for (;;) {
270 /*
271 * TASK_PARKED is a special state; we must serialize against
272 * possible pending wakeups to avoid store-store collisions on
273 * task->state.
274 *
275 * Such a collision might possibly result in the task state
276 * changin from TASK_PARKED and us failing the
277 * wait_task_inactive() in kthread_park().
278 */
279 set_special_state(TASK_PARKED);
280 if (!test_bit(KTHREAD_SHOULD_PARK, &self->flags))
281 break;
282
283 /*
284 * Thread is going to call schedule(), do not preempt it,
285 * or the caller of kthread_park() may spend more time in
286 * wait_task_inactive().
287 */
288 preempt_disable();
289 complete(&self->parked);
290 schedule_preempt_disabled();
291 preempt_enable();
292 }
293 __set_current_state(TASK_RUNNING);
294}
295
296void kthread_parkme(void)
297{
298 __kthread_parkme(to_kthread(current));
299}
300EXPORT_SYMBOL_GPL(kthread_parkme);
301
302/**
303 * kthread_exit - Cause the current kthread return @result to kthread_stop().
304 * @result: The integer value to return to kthread_stop().
305 *
306 * While kthread_exit can be called directly, it exists so that
307 * functions which do some additional work in non-modular code such as
308 * module_put_and_kthread_exit can be implemented.
309 *
310 * Does not return.
311 */
312void __noreturn kthread_exit(long result)
313{
314 struct kthread *kthread = to_kthread(current);
315 kthread->result = result;
316 do_exit(0);
317}
318
319/**
320 * kthread_complete_and_exit - Exit the current kthread.
321 * @comp: Completion to complete
322 * @code: The integer value to return to kthread_stop().
323 *
324 * If present, complete @comp and then return code to kthread_stop().
325 *
326 * A kernel thread whose module may be removed after the completion of
327 * @comp can use this function to exit safely.
328 *
329 * Does not return.
330 */
331void __noreturn kthread_complete_and_exit(struct completion *comp, long code)
332{
333 if (comp)
334 complete(comp);
335
336 kthread_exit(code);
337}
338EXPORT_SYMBOL(kthread_complete_and_exit);
339
340static int kthread(void *_create)
341{
342 static const struct sched_param param = { .sched_priority = 0 };
343 /* Copy data: it's on kthread's stack */
344 struct kthread_create_info *create = _create;
345 int (*threadfn)(void *data) = create->threadfn;
346 void *data = create->data;
347 struct completion *done;
348 struct kthread *self;
349 int ret;
350
351 self = to_kthread(current);
352
353 /* Release the structure when caller killed by a fatal signal. */
354 done = xchg(&create->done, NULL);
355 if (!done) {
356 kfree(create->full_name);
357 kfree(create);
358 kthread_exit(-EINTR);
359 }
360
361 self->full_name = create->full_name;
362 self->threadfn = threadfn;
363 self->data = data;
364
365 /*
366 * The new thread inherited kthreadd's priority and CPU mask. Reset
367 * back to default in case they have been changed.
368 */
369 sched_setscheduler_nocheck(current, SCHED_NORMAL, ¶m);
370 set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_TYPE_KTHREAD));
371
372 /* OK, tell user we're spawned, wait for stop or wakeup */
373 __set_current_state(TASK_UNINTERRUPTIBLE);
374 create->result = current;
375 /*
376 * Thread is going to call schedule(), do not preempt it,
377 * or the creator may spend more time in wait_task_inactive().
378 */
379 preempt_disable();
380 complete(done);
381 schedule_preempt_disabled();
382 preempt_enable();
383
384 ret = -EINTR;
385 if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
386 cgroup_kthread_ready();
387 __kthread_parkme(self);
388 ret = threadfn(data);
389 }
390 kthread_exit(ret);
391}
392
393/* called from kernel_clone() to get node information for about to be created task */
394int tsk_fork_get_node(struct task_struct *tsk)
395{
396#ifdef CONFIG_NUMA
397 if (tsk == kthreadd_task)
398 return tsk->pref_node_fork;
399#endif
400 return NUMA_NO_NODE;
401}
402
403static void create_kthread(struct kthread_create_info *create)
404{
405 int pid;
406
407#ifdef CONFIG_NUMA
408 current->pref_node_fork = create->node;
409#endif
410 /* We want our own signal handler (we take no signals by default). */
411 pid = kernel_thread(kthread, create, create->full_name,
412 CLONE_FS | CLONE_FILES | SIGCHLD);
413 if (pid < 0) {
414 /* Release the structure when caller killed by a fatal signal. */
415 struct completion *done = xchg(&create->done, NULL);
416
417 kfree(create->full_name);
418 if (!done) {
419 kfree(create);
420 return;
421 }
422 create->result = ERR_PTR(pid);
423 complete(done);
424 }
425}
426
427static __printf(4, 0)
428struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
429 void *data, int node,
430 const char namefmt[],
431 va_list args)
432{
433 DECLARE_COMPLETION_ONSTACK(done);
434 struct task_struct *task;
435 struct kthread_create_info *create = kmalloc(sizeof(*create),
436 GFP_KERNEL);
437
438 if (!create)
439 return ERR_PTR(-ENOMEM);
440 create->threadfn = threadfn;
441 create->data = data;
442 create->node = node;
443 create->done = &done;
444 create->full_name = kvasprintf(GFP_KERNEL, namefmt, args);
445 if (!create->full_name) {
446 task = ERR_PTR(-ENOMEM);
447 goto free_create;
448 }
449
450 spin_lock(&kthread_create_lock);
451 list_add_tail(&create->list, &kthread_create_list);
452 spin_unlock(&kthread_create_lock);
453
454 wake_up_process(kthreadd_task);
455 /*
456 * Wait for completion in killable state, for I might be chosen by
457 * the OOM killer while kthreadd is trying to allocate memory for
458 * new kernel thread.
459 */
460 if (unlikely(wait_for_completion_killable(&done))) {
461 /*
462 * If I was killed by a fatal signal before kthreadd (or new
463 * kernel thread) calls complete(), leave the cleanup of this
464 * structure to that thread.
465 */
466 if (xchg(&create->done, NULL))
467 return ERR_PTR(-EINTR);
468 /*
469 * kthreadd (or new kernel thread) will call complete()
470 * shortly.
471 */
472 wait_for_completion(&done);
473 }
474 task = create->result;
475free_create:
476 kfree(create);
477 return task;
478}
479
480/**
481 * kthread_create_on_node - create a kthread.
482 * @threadfn: the function to run until signal_pending(current).
483 * @data: data ptr for @threadfn.
484 * @node: task and thread structures for the thread are allocated on this node
485 * @namefmt: printf-style name for the thread.
486 *
487 * Description: This helper function creates and names a kernel
488 * thread. The thread will be stopped: use wake_up_process() to start
489 * it. See also kthread_run(). The new thread has SCHED_NORMAL policy and
490 * is affine to all CPUs.
491 *
492 * If thread is going to be bound on a particular cpu, give its node
493 * in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
494 * When woken, the thread will run @threadfn() with @data as its
495 * argument. @threadfn() can either return directly if it is a
496 * standalone thread for which no one will call kthread_stop(), or
497 * return when 'kthread_should_stop()' is true (which means
498 * kthread_stop() has been called). The return value should be zero
499 * or a negative error number; it will be passed to kthread_stop().
500 *
501 * Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
502 */
503struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
504 void *data, int node,
505 const char namefmt[],
506 ...)
507{
508 struct task_struct *task;
509 va_list args;
510
511 va_start(args, namefmt);
512 task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
513 va_end(args);
514
515 return task;
516}
517EXPORT_SYMBOL(kthread_create_on_node);
518
519static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, unsigned int state)
520{
521 unsigned long flags;
522
523 if (!wait_task_inactive(p, state)) {
524 WARN_ON(1);
525 return;
526 }
527
528 /* It's safe because the task is inactive. */
529 raw_spin_lock_irqsave(&p->pi_lock, flags);
530 do_set_cpus_allowed(p, mask);
531 p->flags |= PF_NO_SETAFFINITY;
532 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
533}
534
535static void __kthread_bind(struct task_struct *p, unsigned int cpu, unsigned int state)
536{
537 __kthread_bind_mask(p, cpumask_of(cpu), state);
538}
539
540void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
541{
542 __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
543}
544
545/**
546 * kthread_bind - bind a just-created kthread to a cpu.
547 * @p: thread created by kthread_create().
548 * @cpu: cpu (might not be online, must be possible) for @k to run on.
549 *
550 * Description: This function is equivalent to set_cpus_allowed(),
551 * except that @cpu doesn't need to be online, and the thread must be
552 * stopped (i.e., just returned from kthread_create()).
553 */
554void kthread_bind(struct task_struct *p, unsigned int cpu)
555{
556 __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
557}
558EXPORT_SYMBOL(kthread_bind);
559
560/**
561 * kthread_create_on_cpu - Create a cpu bound kthread
562 * @threadfn: the function to run until signal_pending(current).
563 * @data: data ptr for @threadfn.
564 * @cpu: The cpu on which the thread should be bound,
565 * @namefmt: printf-style name for the thread. Format is restricted
566 * to "name.*%u". Code fills in cpu number.
567 *
568 * Description: This helper function creates and names a kernel thread
569 */
570struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
571 void *data, unsigned int cpu,
572 const char *namefmt)
573{
574 struct task_struct *p;
575
576 p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
577 cpu);
578 if (IS_ERR(p))
579 return p;
580 kthread_bind(p, cpu);
581 /* CPU hotplug need to bind once again when unparking the thread. */
582 to_kthread(p)->cpu = cpu;
583 return p;
584}
585EXPORT_SYMBOL(kthread_create_on_cpu);
586
587void kthread_set_per_cpu(struct task_struct *k, int cpu)
588{
589 struct kthread *kthread = to_kthread(k);
590 if (!kthread)
591 return;
592
593 WARN_ON_ONCE(!(k->flags & PF_NO_SETAFFINITY));
594
595 if (cpu < 0) {
596 clear_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
597 return;
598 }
599
600 kthread->cpu = cpu;
601 set_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
602}
603
604bool kthread_is_per_cpu(struct task_struct *p)
605{
606 struct kthread *kthread = __to_kthread(p);
607 if (!kthread)
608 return false;
609
610 return test_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
611}
612
613/**
614 * kthread_unpark - unpark a thread created by kthread_create().
615 * @k: thread created by kthread_create().
616 *
617 * Sets kthread_should_park() for @k to return false, wakes it, and
618 * waits for it to return. If the thread is marked percpu then its
619 * bound to the cpu again.
620 */
621void kthread_unpark(struct task_struct *k)
622{
623 struct kthread *kthread = to_kthread(k);
624
625 /*
626 * Newly created kthread was parked when the CPU was offline.
627 * The binding was lost and we need to set it again.
628 */
629 if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
630 __kthread_bind(k, kthread->cpu, TASK_PARKED);
631
632 clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
633 /*
634 * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup.
635 */
636 wake_up_state(k, TASK_PARKED);
637}
638EXPORT_SYMBOL_GPL(kthread_unpark);
639
640/**
641 * kthread_park - park a thread created by kthread_create().
642 * @k: thread created by kthread_create().
643 *
644 * Sets kthread_should_park() for @k to return true, wakes it, and
645 * waits for it to return. This can also be called after kthread_create()
646 * instead of calling wake_up_process(): the thread will park without
647 * calling threadfn().
648 *
649 * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
650 * If called by the kthread itself just the park bit is set.
651 */
652int kthread_park(struct task_struct *k)
653{
654 struct kthread *kthread = to_kthread(k);
655
656 if (WARN_ON(k->flags & PF_EXITING))
657 return -ENOSYS;
658
659 if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK, &kthread->flags)))
660 return -EBUSY;
661
662 set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
663 if (k != current) {
664 wake_up_process(k);
665 /*
666 * Wait for __kthread_parkme() to complete(), this means we
667 * _will_ have TASK_PARKED and are about to call schedule().
668 */
669 wait_for_completion(&kthread->parked);
670 /*
671 * Now wait for that schedule() to complete and the task to
672 * get scheduled out.
673 */
674 WARN_ON_ONCE(!wait_task_inactive(k, TASK_PARKED));
675 }
676
677 return 0;
678}
679EXPORT_SYMBOL_GPL(kthread_park);
680
681/**
682 * kthread_stop - stop a thread created by kthread_create().
683 * @k: thread created by kthread_create().
684 *
685 * Sets kthread_should_stop() for @k to return true, wakes it, and
686 * waits for it to exit. This can also be called after kthread_create()
687 * instead of calling wake_up_process(): the thread will exit without
688 * calling threadfn().
689 *
690 * If threadfn() may call kthread_exit() itself, the caller must ensure
691 * task_struct can't go away.
692 *
693 * Returns the result of threadfn(), or %-EINTR if wake_up_process()
694 * was never called.
695 */
696int kthread_stop(struct task_struct *k)
697{
698 struct kthread *kthread;
699 int ret;
700
701 trace_sched_kthread_stop(k);
702
703 get_task_struct(k);
704 kthread = to_kthread(k);
705 set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
706 kthread_unpark(k);
707 set_tsk_thread_flag(k, TIF_NOTIFY_SIGNAL);
708 wake_up_process(k);
709 wait_for_completion(&kthread->exited);
710 ret = kthread->result;
711 put_task_struct(k);
712
713 trace_sched_kthread_stop_ret(ret);
714 return ret;
715}
716EXPORT_SYMBOL(kthread_stop);
717
718/**
719 * kthread_stop_put - stop a thread and put its task struct
720 * @k: thread created by kthread_create().
721 *
722 * Stops a thread created by kthread_create() and put its task_struct.
723 * Only use when holding an extra task struct reference obtained by
724 * calling get_task_struct().
725 */
726int kthread_stop_put(struct task_struct *k)
727{
728 int ret;
729
730 ret = kthread_stop(k);
731 put_task_struct(k);
732 return ret;
733}
734EXPORT_SYMBOL(kthread_stop_put);
735
736int kthreadd(void *unused)
737{
738 struct task_struct *tsk = current;
739
740 /* Setup a clean context for our children to inherit. */
741 set_task_comm(tsk, "kthreadd");
742 ignore_signals(tsk);
743 set_cpus_allowed_ptr(tsk, housekeeping_cpumask(HK_TYPE_KTHREAD));
744 set_mems_allowed(node_states[N_MEMORY]);
745
746 current->flags |= PF_NOFREEZE;
747 cgroup_init_kthreadd();
748
749 for (;;) {
750 set_current_state(TASK_INTERRUPTIBLE);
751 if (list_empty(&kthread_create_list))
752 schedule();
753 __set_current_state(TASK_RUNNING);
754
755 spin_lock(&kthread_create_lock);
756 while (!list_empty(&kthread_create_list)) {
757 struct kthread_create_info *create;
758
759 create = list_entry(kthread_create_list.next,
760 struct kthread_create_info, list);
761 list_del_init(&create->list);
762 spin_unlock(&kthread_create_lock);
763
764 create_kthread(create);
765
766 spin_lock(&kthread_create_lock);
767 }
768 spin_unlock(&kthread_create_lock);
769 }
770
771 return 0;
772}
773
774void __kthread_init_worker(struct kthread_worker *worker,
775 const char *name,
776 struct lock_class_key *key)
777{
778 memset(worker, 0, sizeof(struct kthread_worker));
779 raw_spin_lock_init(&worker->lock);
780 lockdep_set_class_and_name(&worker->lock, key, name);
781 INIT_LIST_HEAD(&worker->work_list);
782 INIT_LIST_HEAD(&worker->delayed_work_list);
783}
784EXPORT_SYMBOL_GPL(__kthread_init_worker);
785
786/**
787 * kthread_worker_fn - kthread function to process kthread_worker
788 * @worker_ptr: pointer to initialized kthread_worker
789 *
790 * This function implements the main cycle of kthread worker. It processes
791 * work_list until it is stopped with kthread_stop(). It sleeps when the queue
792 * is empty.
793 *
794 * The works are not allowed to keep any locks, disable preemption or interrupts
795 * when they finish. There is defined a safe point for freezing when one work
796 * finishes and before a new one is started.
797 *
798 * Also the works must not be handled by more than one worker at the same time,
799 * see also kthread_queue_work().
800 */
801int kthread_worker_fn(void *worker_ptr)
802{
803 struct kthread_worker *worker = worker_ptr;
804 struct kthread_work *work;
805
806 /*
807 * FIXME: Update the check and remove the assignment when all kthread
808 * worker users are created using kthread_create_worker*() functions.
809 */
810 WARN_ON(worker->task && worker->task != current);
811 worker->task = current;
812
813 if (worker->flags & KTW_FREEZABLE)
814 set_freezable();
815
816repeat:
817 set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
818
819 if (kthread_should_stop()) {
820 __set_current_state(TASK_RUNNING);
821 raw_spin_lock_irq(&worker->lock);
822 worker->task = NULL;
823 raw_spin_unlock_irq(&worker->lock);
824 return 0;
825 }
826
827 work = NULL;
828 raw_spin_lock_irq(&worker->lock);
829 if (!list_empty(&worker->work_list)) {
830 work = list_first_entry(&worker->work_list,
831 struct kthread_work, node);
832 list_del_init(&work->node);
833 }
834 worker->current_work = work;
835 raw_spin_unlock_irq(&worker->lock);
836
837 if (work) {
838 kthread_work_func_t func = work->func;
839 __set_current_state(TASK_RUNNING);
840 trace_sched_kthread_work_execute_start(work);
841 work->func(work);
842 /*
843 * Avoid dereferencing work after this point. The trace
844 * event only cares about the address.
845 */
846 trace_sched_kthread_work_execute_end(work, func);
847 } else if (!freezing(current))
848 schedule();
849
850 try_to_freeze();
851 cond_resched();
852 goto repeat;
853}
854EXPORT_SYMBOL_GPL(kthread_worker_fn);
855
856static __printf(3, 0) struct kthread_worker *
857__kthread_create_worker(int cpu, unsigned int flags,
858 const char namefmt[], va_list args)
859{
860 struct kthread_worker *worker;
861 struct task_struct *task;
862 int node = NUMA_NO_NODE;
863
864 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
865 if (!worker)
866 return ERR_PTR(-ENOMEM);
867
868 kthread_init_worker(worker);
869
870 if (cpu >= 0)
871 node = cpu_to_node(cpu);
872
873 task = __kthread_create_on_node(kthread_worker_fn, worker,
874 node, namefmt, args);
875 if (IS_ERR(task))
876 goto fail_task;
877
878 if (cpu >= 0)
879 kthread_bind(task, cpu);
880
881 worker->flags = flags;
882 worker->task = task;
883 wake_up_process(task);
884 return worker;
885
886fail_task:
887 kfree(worker);
888 return ERR_CAST(task);
889}
890
891/**
892 * kthread_create_worker - create a kthread worker
893 * @flags: flags modifying the default behavior of the worker
894 * @namefmt: printf-style name for the kthread worker (task).
895 *
896 * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
897 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
898 * when the caller was killed by a fatal signal.
899 */
900struct kthread_worker *
901kthread_create_worker(unsigned int flags, const char namefmt[], ...)
902{
903 struct kthread_worker *worker;
904 va_list args;
905
906 va_start(args, namefmt);
907 worker = __kthread_create_worker(-1, flags, namefmt, args);
908 va_end(args);
909
910 return worker;
911}
912EXPORT_SYMBOL(kthread_create_worker);
913
914/**
915 * kthread_create_worker_on_cpu - create a kthread worker and bind it
916 * to a given CPU and the associated NUMA node.
917 * @cpu: CPU number
918 * @flags: flags modifying the default behavior of the worker
919 * @namefmt: printf-style name for the kthread worker (task).
920 *
921 * Use a valid CPU number if you want to bind the kthread worker
922 * to the given CPU and the associated NUMA node.
923 *
924 * A good practice is to add the cpu number also into the worker name.
925 * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
926 *
927 * CPU hotplug:
928 * The kthread worker API is simple and generic. It just provides a way
929 * to create, use, and destroy workers.
930 *
931 * It is up to the API user how to handle CPU hotplug. They have to decide
932 * how to handle pending work items, prevent queuing new ones, and
933 * restore the functionality when the CPU goes off and on. There are a
934 * few catches:
935 *
936 * - CPU affinity gets lost when it is scheduled on an offline CPU.
937 *
938 * - The worker might not exist when the CPU was off when the user
939 * created the workers.
940 *
941 * Good practice is to implement two CPU hotplug callbacks and to
942 * destroy/create the worker when the CPU goes down/up.
943 *
944 * Return:
945 * The pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
946 * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
947 * when the caller was killed by a fatal signal.
948 */
949struct kthread_worker *
950kthread_create_worker_on_cpu(int cpu, unsigned int flags,
951 const char namefmt[], ...)
952{
953 struct kthread_worker *worker;
954 va_list args;
955
956 va_start(args, namefmt);
957 worker = __kthread_create_worker(cpu, flags, namefmt, args);
958 va_end(args);
959
960 return worker;
961}
962EXPORT_SYMBOL(kthread_create_worker_on_cpu);
963
964/*
965 * Returns true when the work could not be queued at the moment.
966 * It happens when it is already pending in a worker list
967 * or when it is being cancelled.
968 */
969static inline bool queuing_blocked(struct kthread_worker *worker,
970 struct kthread_work *work)
971{
972 lockdep_assert_held(&worker->lock);
973
974 return !list_empty(&work->node) || work->canceling;
975}
976
977static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
978 struct kthread_work *work)
979{
980 lockdep_assert_held(&worker->lock);
981 WARN_ON_ONCE(!list_empty(&work->node));
982 /* Do not use a work with >1 worker, see kthread_queue_work() */
983 WARN_ON_ONCE(work->worker && work->worker != worker);
984}
985
986/* insert @work before @pos in @worker */
987static void kthread_insert_work(struct kthread_worker *worker,
988 struct kthread_work *work,
989 struct list_head *pos)
990{
991 kthread_insert_work_sanity_check(worker, work);
992
993 trace_sched_kthread_work_queue_work(worker, work);
994
995 list_add_tail(&work->node, pos);
996 work->worker = worker;
997 if (!worker->current_work && likely(worker->task))
998 wake_up_process(worker->task);
999}
1000
1001/**
1002 * kthread_queue_work - queue a kthread_work
1003 * @worker: target kthread_worker
1004 * @work: kthread_work to queue
1005 *
1006 * Queue @work to work processor @task for async execution. @task
1007 * must have been created with kthread_worker_create(). Returns %true
1008 * if @work was successfully queued, %false if it was already pending.
1009 *
1010 * Reinitialize the work if it needs to be used by another worker.
1011 * For example, when the worker was stopped and started again.
1012 */
1013bool kthread_queue_work(struct kthread_worker *worker,
1014 struct kthread_work *work)
1015{
1016 bool ret = false;
1017 unsigned long flags;
1018
1019 raw_spin_lock_irqsave(&worker->lock, flags);
1020 if (!queuing_blocked(worker, work)) {
1021 kthread_insert_work(worker, work, &worker->work_list);
1022 ret = true;
1023 }
1024 raw_spin_unlock_irqrestore(&worker->lock, flags);
1025 return ret;
1026}
1027EXPORT_SYMBOL_GPL(kthread_queue_work);
1028
1029/**
1030 * kthread_delayed_work_timer_fn - callback that queues the associated kthread
1031 * delayed work when the timer expires.
1032 * @t: pointer to the expired timer
1033 *
1034 * The format of the function is defined by struct timer_list.
1035 * It should have been called from irqsafe timer with irq already off.
1036 */
1037void kthread_delayed_work_timer_fn(struct timer_list *t)
1038{
1039 struct kthread_delayed_work *dwork = from_timer(dwork, t, timer);
1040 struct kthread_work *work = &dwork->work;
1041 struct kthread_worker *worker = work->worker;
1042 unsigned long flags;
1043
1044 /*
1045 * This might happen when a pending work is reinitialized.
1046 * It means that it is used a wrong way.
1047 */
1048 if (WARN_ON_ONCE(!worker))
1049 return;
1050
1051 raw_spin_lock_irqsave(&worker->lock, flags);
1052 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1053 WARN_ON_ONCE(work->worker != worker);
1054
1055 /* Move the work from worker->delayed_work_list. */
1056 WARN_ON_ONCE(list_empty(&work->node));
1057 list_del_init(&work->node);
1058 if (!work->canceling)
1059 kthread_insert_work(worker, work, &worker->work_list);
1060
1061 raw_spin_unlock_irqrestore(&worker->lock, flags);
1062}
1063EXPORT_SYMBOL(kthread_delayed_work_timer_fn);
1064
1065static void __kthread_queue_delayed_work(struct kthread_worker *worker,
1066 struct kthread_delayed_work *dwork,
1067 unsigned long delay)
1068{
1069 struct timer_list *timer = &dwork->timer;
1070 struct kthread_work *work = &dwork->work;
1071
1072 WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);
1073
1074 /*
1075 * If @delay is 0, queue @dwork->work immediately. This is for
1076 * both optimization and correctness. The earliest @timer can
1077 * expire is on the closest next tick and delayed_work users depend
1078 * on that there's no such delay when @delay is 0.
1079 */
1080 if (!delay) {
1081 kthread_insert_work(worker, work, &worker->work_list);
1082 return;
1083 }
1084
1085 /* Be paranoid and try to detect possible races already now. */
1086 kthread_insert_work_sanity_check(worker, work);
1087
1088 list_add(&work->node, &worker->delayed_work_list);
1089 work->worker = worker;
1090 timer->expires = jiffies + delay;
1091 add_timer(timer);
1092}
1093
1094/**
1095 * kthread_queue_delayed_work - queue the associated kthread work
1096 * after a delay.
1097 * @worker: target kthread_worker
1098 * @dwork: kthread_delayed_work to queue
1099 * @delay: number of jiffies to wait before queuing
1100 *
1101 * If the work has not been pending it starts a timer that will queue
1102 * the work after the given @delay. If @delay is zero, it queues the
1103 * work immediately.
1104 *
1105 * Return: %false if the @work has already been pending. It means that
1106 * either the timer was running or the work was queued. It returns %true
1107 * otherwise.
1108 */
1109bool kthread_queue_delayed_work(struct kthread_worker *worker,
1110 struct kthread_delayed_work *dwork,
1111 unsigned long delay)
1112{
1113 struct kthread_work *work = &dwork->work;
1114 unsigned long flags;
1115 bool ret = false;
1116
1117 raw_spin_lock_irqsave(&worker->lock, flags);
1118
1119 if (!queuing_blocked(worker, work)) {
1120 __kthread_queue_delayed_work(worker, dwork, delay);
1121 ret = true;
1122 }
1123
1124 raw_spin_unlock_irqrestore(&worker->lock, flags);
1125 return ret;
1126}
1127EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
1128
1129struct kthread_flush_work {
1130 struct kthread_work work;
1131 struct completion done;
1132};
1133
1134static void kthread_flush_work_fn(struct kthread_work *work)
1135{
1136 struct kthread_flush_work *fwork =
1137 container_of(work, struct kthread_flush_work, work);
1138 complete(&fwork->done);
1139}
1140
1141/**
1142 * kthread_flush_work - flush a kthread_work
1143 * @work: work to flush
1144 *
1145 * If @work is queued or executing, wait for it to finish execution.
1146 */
1147void kthread_flush_work(struct kthread_work *work)
1148{
1149 struct kthread_flush_work fwork = {
1150 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1151 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1152 };
1153 struct kthread_worker *worker;
1154 bool noop = false;
1155
1156 worker = work->worker;
1157 if (!worker)
1158 return;
1159
1160 raw_spin_lock_irq(&worker->lock);
1161 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1162 WARN_ON_ONCE(work->worker != worker);
1163
1164 if (!list_empty(&work->node))
1165 kthread_insert_work(worker, &fwork.work, work->node.next);
1166 else if (worker->current_work == work)
1167 kthread_insert_work(worker, &fwork.work,
1168 worker->work_list.next);
1169 else
1170 noop = true;
1171
1172 raw_spin_unlock_irq(&worker->lock);
1173
1174 if (!noop)
1175 wait_for_completion(&fwork.done);
1176}
1177EXPORT_SYMBOL_GPL(kthread_flush_work);
1178
1179/*
1180 * Make sure that the timer is neither set nor running and could
1181 * not manipulate the work list_head any longer.
1182 *
1183 * The function is called under worker->lock. The lock is temporary
1184 * released but the timer can't be set again in the meantime.
1185 */
1186static void kthread_cancel_delayed_work_timer(struct kthread_work *work,
1187 unsigned long *flags)
1188{
1189 struct kthread_delayed_work *dwork =
1190 container_of(work, struct kthread_delayed_work, work);
1191 struct kthread_worker *worker = work->worker;
1192
1193 /*
1194 * del_timer_sync() must be called to make sure that the timer
1195 * callback is not running. The lock must be temporary released
1196 * to avoid a deadlock with the callback. In the meantime,
1197 * any queuing is blocked by setting the canceling counter.
1198 */
1199 work->canceling++;
1200 raw_spin_unlock_irqrestore(&worker->lock, *flags);
1201 del_timer_sync(&dwork->timer);
1202 raw_spin_lock_irqsave(&worker->lock, *flags);
1203 work->canceling--;
1204}
1205
1206/*
1207 * This function removes the work from the worker queue.
1208 *
1209 * It is called under worker->lock. The caller must make sure that
1210 * the timer used by delayed work is not running, e.g. by calling
1211 * kthread_cancel_delayed_work_timer().
1212 *
1213 * The work might still be in use when this function finishes. See the
1214 * current_work proceed by the worker.
1215 *
1216 * Return: %true if @work was pending and successfully canceled,
1217 * %false if @work was not pending
1218 */
1219static bool __kthread_cancel_work(struct kthread_work *work)
1220{
1221 /*
1222 * Try to remove the work from a worker list. It might either
1223 * be from worker->work_list or from worker->delayed_work_list.
1224 */
1225 if (!list_empty(&work->node)) {
1226 list_del_init(&work->node);
1227 return true;
1228 }
1229
1230 return false;
1231}
1232
1233/**
1234 * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1235 * @worker: kthread worker to use
1236 * @dwork: kthread delayed work to queue
1237 * @delay: number of jiffies to wait before queuing
1238 *
1239 * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1240 * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1241 * @work is guaranteed to be queued immediately.
1242 *
1243 * Return: %false if @dwork was idle and queued, %true otherwise.
1244 *
1245 * A special case is when the work is being canceled in parallel.
1246 * It might be caused either by the real kthread_cancel_delayed_work_sync()
1247 * or yet another kthread_mod_delayed_work() call. We let the other command
1248 * win and return %true here. The return value can be used for reference
1249 * counting and the number of queued works stays the same. Anyway, the caller
1250 * is supposed to synchronize these operations a reasonable way.
1251 *
1252 * This function is safe to call from any context including IRQ handler.
1253 * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1254 * for details.
1255 */
1256bool kthread_mod_delayed_work(struct kthread_worker *worker,
1257 struct kthread_delayed_work *dwork,
1258 unsigned long delay)
1259{
1260 struct kthread_work *work = &dwork->work;
1261 unsigned long flags;
1262 int ret;
1263
1264 raw_spin_lock_irqsave(&worker->lock, flags);
1265
1266 /* Do not bother with canceling when never queued. */
1267 if (!work->worker) {
1268 ret = false;
1269 goto fast_queue;
1270 }
1271
1272 /* Work must not be used with >1 worker, see kthread_queue_work() */
1273 WARN_ON_ONCE(work->worker != worker);
1274
1275 /*
1276 * Temporary cancel the work but do not fight with another command
1277 * that is canceling the work as well.
1278 *
1279 * It is a bit tricky because of possible races with another
1280 * mod_delayed_work() and cancel_delayed_work() callers.
1281 *
1282 * The timer must be canceled first because worker->lock is released
1283 * when doing so. But the work can be removed from the queue (list)
1284 * only when it can be queued again so that the return value can
1285 * be used for reference counting.
1286 */
1287 kthread_cancel_delayed_work_timer(work, &flags);
1288 if (work->canceling) {
1289 /* The number of works in the queue does not change. */
1290 ret = true;
1291 goto out;
1292 }
1293 ret = __kthread_cancel_work(work);
1294
1295fast_queue:
1296 __kthread_queue_delayed_work(worker, dwork, delay);
1297out:
1298 raw_spin_unlock_irqrestore(&worker->lock, flags);
1299 return ret;
1300}
1301EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1302
1303static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1304{
1305 struct kthread_worker *worker = work->worker;
1306 unsigned long flags;
1307 int ret = false;
1308
1309 if (!worker)
1310 goto out;
1311
1312 raw_spin_lock_irqsave(&worker->lock, flags);
1313 /* Work must not be used with >1 worker, see kthread_queue_work(). */
1314 WARN_ON_ONCE(work->worker != worker);
1315
1316 if (is_dwork)
1317 kthread_cancel_delayed_work_timer(work, &flags);
1318
1319 ret = __kthread_cancel_work(work);
1320
1321 if (worker->current_work != work)
1322 goto out_fast;
1323
1324 /*
1325 * The work is in progress and we need to wait with the lock released.
1326 * In the meantime, block any queuing by setting the canceling counter.
1327 */
1328 work->canceling++;
1329 raw_spin_unlock_irqrestore(&worker->lock, flags);
1330 kthread_flush_work(work);
1331 raw_spin_lock_irqsave(&worker->lock, flags);
1332 work->canceling--;
1333
1334out_fast:
1335 raw_spin_unlock_irqrestore(&worker->lock, flags);
1336out:
1337 return ret;
1338}
1339
1340/**
1341 * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1342 * @work: the kthread work to cancel
1343 *
1344 * Cancel @work and wait for its execution to finish. This function
1345 * can be used even if the work re-queues itself. On return from this
1346 * function, @work is guaranteed to be not pending or executing on any CPU.
1347 *
1348 * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1349 * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1350 *
1351 * The caller must ensure that the worker on which @work was last
1352 * queued can't be destroyed before this function returns.
1353 *
1354 * Return: %true if @work was pending, %false otherwise.
1355 */
1356bool kthread_cancel_work_sync(struct kthread_work *work)
1357{
1358 return __kthread_cancel_work_sync(work, false);
1359}
1360EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1361
1362/**
1363 * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1364 * wait for it to finish.
1365 * @dwork: the kthread delayed work to cancel
1366 *
1367 * This is kthread_cancel_work_sync() for delayed works.
1368 *
1369 * Return: %true if @dwork was pending, %false otherwise.
1370 */
1371bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1372{
1373 return __kthread_cancel_work_sync(&dwork->work, true);
1374}
1375EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1376
1377/**
1378 * kthread_flush_worker - flush all current works on a kthread_worker
1379 * @worker: worker to flush
1380 *
1381 * Wait until all currently executing or pending works on @worker are
1382 * finished.
1383 */
1384void kthread_flush_worker(struct kthread_worker *worker)
1385{
1386 struct kthread_flush_work fwork = {
1387 KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1388 COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1389 };
1390
1391 kthread_queue_work(worker, &fwork.work);
1392 wait_for_completion(&fwork.done);
1393}
1394EXPORT_SYMBOL_GPL(kthread_flush_worker);
1395
1396/**
1397 * kthread_destroy_worker - destroy a kthread worker
1398 * @worker: worker to be destroyed
1399 *
1400 * Flush and destroy @worker. The simple flush is enough because the kthread
1401 * worker API is used only in trivial scenarios. There are no multi-step state
1402 * machines needed.
1403 *
1404 * Note that this function is not responsible for handling delayed work, so
1405 * caller should be responsible for queuing or canceling all delayed work items
1406 * before invoke this function.
1407 */
1408void kthread_destroy_worker(struct kthread_worker *worker)
1409{
1410 struct task_struct *task;
1411
1412 task = worker->task;
1413 if (WARN_ON(!task))
1414 return;
1415
1416 kthread_flush_worker(worker);
1417 kthread_stop(task);
1418 WARN_ON(!list_empty(&worker->delayed_work_list));
1419 WARN_ON(!list_empty(&worker->work_list));
1420 kfree(worker);
1421}
1422EXPORT_SYMBOL(kthread_destroy_worker);
1423
1424/**
1425 * kthread_use_mm - make the calling kthread operate on an address space
1426 * @mm: address space to operate on
1427 */
1428void kthread_use_mm(struct mm_struct *mm)
1429{
1430 struct mm_struct *active_mm;
1431 struct task_struct *tsk = current;
1432
1433 WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
1434 WARN_ON_ONCE(tsk->mm);
1435
1436 /*
1437 * It is possible for mm to be the same as tsk->active_mm, but
1438 * we must still mmgrab(mm) and mmdrop_lazy_tlb(active_mm),
1439 * because these references are not equivalent.
1440 */
1441 mmgrab(mm);
1442
1443 task_lock(tsk);
1444 /* Hold off tlb flush IPIs while switching mm's */
1445 local_irq_disable();
1446 active_mm = tsk->active_mm;
1447 tsk->active_mm = mm;
1448 tsk->mm = mm;
1449 membarrier_update_current_mm(mm);
1450 switch_mm_irqs_off(active_mm, mm, tsk);
1451 local_irq_enable();
1452 task_unlock(tsk);
1453#ifdef finish_arch_post_lock_switch
1454 finish_arch_post_lock_switch();
1455#endif
1456
1457 /*
1458 * When a kthread starts operating on an address space, the loop
1459 * in membarrier_{private,global}_expedited() may not observe
1460 * that tsk->mm, and not issue an IPI. Membarrier requires a
1461 * memory barrier after storing to tsk->mm, before accessing
1462 * user-space memory. A full memory barrier for membarrier
1463 * {PRIVATE,GLOBAL}_EXPEDITED is implicitly provided by
1464 * mmdrop_lazy_tlb().
1465 */
1466 mmdrop_lazy_tlb(active_mm);
1467}
1468EXPORT_SYMBOL_GPL(kthread_use_mm);
1469
1470/**
1471 * kthread_unuse_mm - reverse the effect of kthread_use_mm()
1472 * @mm: address space to operate on
1473 */
1474void kthread_unuse_mm(struct mm_struct *mm)
1475{
1476 struct task_struct *tsk = current;
1477
1478 WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
1479 WARN_ON_ONCE(!tsk->mm);
1480
1481 task_lock(tsk);
1482 /*
1483 * When a kthread stops operating on an address space, the loop
1484 * in membarrier_{private,global}_expedited() may not observe
1485 * that tsk->mm, and not issue an IPI. Membarrier requires a
1486 * memory barrier after accessing user-space memory, before
1487 * clearing tsk->mm.
1488 */
1489 smp_mb__after_spinlock();
1490 local_irq_disable();
1491 tsk->mm = NULL;
1492 membarrier_update_current_mm(NULL);
1493 mmgrab_lazy_tlb(mm);
1494 /* active_mm is still 'mm' */
1495 enter_lazy_tlb(mm, tsk);
1496 local_irq_enable();
1497 task_unlock(tsk);
1498
1499 mmdrop(mm);
1500}
1501EXPORT_SYMBOL_GPL(kthread_unuse_mm);
1502
1503#ifdef CONFIG_BLK_CGROUP
1504/**
1505 * kthread_associate_blkcg - associate blkcg to current kthread
1506 * @css: the cgroup info
1507 *
1508 * Current thread must be a kthread. The thread is running jobs on behalf of
1509 * other threads. In some cases, we expect the jobs attach cgroup info of
1510 * original threads instead of that of current thread. This function stores
1511 * original thread's cgroup info in current kthread context for later
1512 * retrieval.
1513 */
1514void kthread_associate_blkcg(struct cgroup_subsys_state *css)
1515{
1516 struct kthread *kthread;
1517
1518 if (!(current->flags & PF_KTHREAD))
1519 return;
1520 kthread = to_kthread(current);
1521 if (!kthread)
1522 return;
1523
1524 if (kthread->blkcg_css) {
1525 css_put(kthread->blkcg_css);
1526 kthread->blkcg_css = NULL;
1527 }
1528 if (css) {
1529 css_get(css);
1530 kthread->blkcg_css = css;
1531 }
1532}
1533EXPORT_SYMBOL(kthread_associate_blkcg);
1534
1535/**
1536 * kthread_blkcg - get associated blkcg css of current kthread
1537 *
1538 * Current thread must be a kthread.
1539 */
1540struct cgroup_subsys_state *kthread_blkcg(void)
1541{
1542 struct kthread *kthread;
1543
1544 if (current->flags & PF_KTHREAD) {
1545 kthread = to_kthread(current);
1546 if (kthread)
1547 return kthread->blkcg_css;
1548 }
1549 return NULL;
1550}
1551#endif