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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
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