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