Line data Source code
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 :
34 : static DEFINE_SPINLOCK(kthread_create_lock);
35 : static LIST_HEAD(kthread_create_list);
36 : struct task_struct *kthreadd_task;
37 :
38 : struct 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 :
52 : struct 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 :
65 : enum KTHREAD_BITS {
66 : KTHREAD_IS_PER_CPU = 0,
67 : KTHREAD_SHOULD_STOP,
68 : KTHREAD_SHOULD_PARK,
69 : };
70 :
71 48 : static 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 48 : current->set_child_tid = (__force void __user *)kthread;
79 : }
80 :
81 29437 : static inline struct kthread *to_kthread(struct task_struct *k)
82 : {
83 29437 : WARN_ON(!(k->flags & PF_KTHREAD));
84 29437 : return (__force void *)k->set_child_tid;
85 : }
86 :
87 0 : void free_kthread_struct(struct task_struct *k)
88 : {
89 0 : 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 0 : kthread = to_kthread(k);
96 : #ifdef CONFIG_BLK_CGROUP
97 : WARN_ON_ONCE(kthread && kthread->blkcg_css);
98 : #endif
99 0 : kfree(kthread);
100 0 : }
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 : */
109 8062 : bool kthread_should_stop(void)
110 : {
111 8062 : return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
112 : }
113 : EXPORT_SYMBOL(kthread_should_stop);
114 :
115 9370 : bool __kthread_should_park(struct task_struct *k)
116 : {
117 9370 : return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(k)->flags);
118 : }
119 : EXPORT_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 : */
132 7788 : bool kthread_should_park(void)
133 : {
134 7788 : return __kthread_should_park(current);
135 : }
136 : EXPORT_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 : */
147 0 : bool kthread_freezable_should_stop(bool *was_frozen)
148 : {
149 0 : bool frozen = false;
150 :
151 0 : might_sleep();
152 :
153 0 : if (unlikely(freezing(current)))
154 : frozen = __refrigerator(true);
155 :
156 0 : if (was_frozen)
157 0 : *was_frozen = frozen;
158 :
159 0 : return kthread_should_stop();
160 : }
161 : EXPORT_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 : */
169 0 : void *kthread_func(struct task_struct *task)
170 : {
171 0 : if (task->flags & PF_KTHREAD)
172 0 : return to_kthread(task)->threadfn;
173 : return NULL;
174 : }
175 : EXPORT_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 : */
185 3803 : void *kthread_data(struct task_struct *task)
186 : {
187 3803 : return to_kthread(task)->data;
188 : }
189 : EXPORT_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 : */
200 0 : void *kthread_probe_data(struct task_struct *task)
201 : {
202 0 : struct kthread *kthread = to_kthread(task);
203 0 : void *data = NULL;
204 :
205 0 : copy_from_kernel_nofault(&data, &kthread->data, sizeof(data));
206 0 : return data;
207 : }
208 :
209 48 : static void __kthread_parkme(struct kthread *self)
210 : {
211 60 : 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 60 : set_special_state(TASK_PARKED);
222 60 : 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 12 : preempt_disable();
231 12 : complete(&self->parked);
232 12 : schedule_preempt_disabled();
233 60 : preempt_enable();
234 : }
235 48 : __set_current_state(TASK_RUNNING);
236 48 : }
237 :
238 0 : void kthread_parkme(void)
239 : {
240 0 : __kthread_parkme(to_kthread(current));
241 0 : }
242 : EXPORT_SYMBOL_GPL(kthread_parkme);
243 :
244 48 : static int kthread(void *_create)
245 : {
246 : /* Copy data: it's on kthread's stack */
247 48 : struct kthread_create_info *create = _create;
248 48 : int (*threadfn)(void *data) = create->threadfn;
249 48 : void *data = create->data;
250 48 : struct completion *done;
251 48 : struct kthread *self;
252 48 : int ret;
253 :
254 48 : self = kzalloc(sizeof(*self), GFP_KERNEL);
255 48 : set_kthread_struct(self);
256 :
257 : /* If user was SIGKILLed, I release the structure. */
258 48 : done = xchg(&create->done, NULL);
259 48 : if (!done) {
260 0 : kfree(create);
261 0 : do_exit(-EINTR);
262 : }
263 :
264 48 : if (!self) {
265 0 : create->result = ERR_PTR(-ENOMEM);
266 0 : complete(done);
267 0 : do_exit(-ENOMEM);
268 : }
269 :
270 48 : self->threadfn = threadfn;
271 48 : self->data = data;
272 48 : init_completion(&self->exited);
273 48 : init_completion(&self->parked);
274 48 : current->vfork_done = &self->exited;
275 :
276 : /* OK, tell user we're spawned, wait for stop or wakeup */
277 48 : __set_current_state(TASK_UNINTERRUPTIBLE);
278 48 : 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 48 : preempt_disable();
284 48 : complete(done);
285 48 : schedule_preempt_disabled();
286 48 : preempt_enable();
287 :
288 48 : ret = -EINTR;
289 48 : if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
290 48 : cgroup_kthread_ready();
291 48 : __kthread_parkme(self);
292 48 : ret = threadfn(data);
293 : }
294 0 : do_exit(ret);
295 : }
296 :
297 : /* called from kernel_clone() to get node information for about to be created task */
298 951 : int tsk_fork_get_node(struct task_struct *tsk)
299 : {
300 : #ifdef CONFIG_NUMA
301 951 : if (tsk == kthreadd_task)
302 48 : return tsk->pref_node_fork;
303 : #endif
304 : return NUMA_NO_NODE;
305 : }
306 :
307 48 : static void create_kthread(struct kthread_create_info *create)
308 : {
309 48 : int pid;
310 :
311 : #ifdef CONFIG_NUMA
312 48 : current->pref_node_fork = create->node;
313 : #endif
314 : /* We want our own signal handler (we take no signals by default). */
315 48 : pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
316 48 : if (pid < 0) {
317 : /* If user was SIGKILLed, I release the structure. */
318 0 : struct completion *done = xchg(&create->done, NULL);
319 :
320 0 : if (!done) {
321 0 : kfree(create);
322 0 : return;
323 : }
324 0 : create->result = ERR_PTR(pid);
325 0 : complete(done);
326 : }
327 : }
328 :
329 : static __printf(4, 0)
330 48 : struct 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 48 : DECLARE_COMPLETION_ONSTACK(done);
336 48 : struct task_struct *task;
337 48 : struct kthread_create_info *create = kmalloc(sizeof(*create),
338 : GFP_KERNEL);
339 :
340 48 : if (!create)
341 48 : return ERR_PTR(-ENOMEM);
342 48 : create->threadfn = threadfn;
343 48 : create->data = data;
344 48 : create->node = node;
345 48 : create->done = &done;
346 :
347 48 : spin_lock(&kthread_create_lock);
348 48 : list_add_tail(&create->list, &kthread_create_list);
349 48 : spin_unlock(&kthread_create_lock);
350 :
351 48 : 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 48 : 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 0 : if (xchg(&create->done, NULL))
364 48 : return ERR_PTR(-EINTR);
365 : /*
366 : * kthreadd (or new kernel thread) will call complete()
367 : * shortly.
368 : */
369 0 : wait_for_completion(&done);
370 : }
371 48 : task = create->result;
372 48 : if (!IS_ERR(task)) {
373 48 : static const struct sched_param param = { .sched_priority = 0 };
374 48 : char name[TASK_COMM_LEN];
375 :
376 : /*
377 : * task is already visible to other tasks, so updating
378 : * COMM must be protected.
379 : */
380 48 : vsnprintf(name, sizeof(name), namefmt, args);
381 48 : 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 48 : sched_setscheduler_nocheck(task, SCHED_NORMAL, ¶m);
387 48 : set_cpus_allowed_ptr(task,
388 : housekeeping_cpumask(HK_FLAG_KTHREAD));
389 : }
390 48 : kfree(create);
391 48 : 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 : */
417 48 : struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
418 : void *data, int node,
419 : const char namefmt[],
420 : ...)
421 : {
422 48 : struct task_struct *task;
423 48 : va_list args;
424 :
425 48 : va_start(args, namefmt);
426 48 : task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
427 48 : va_end(args);
428 :
429 48 : return task;
430 : }
431 : EXPORT_SYMBOL(kthread_create_on_node);
432 :
433 52 : static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
434 : {
435 52 : unsigned long flags;
436 :
437 52 : if (!wait_task_inactive(p, state)) {
438 0 : WARN_ON(1);
439 0 : return;
440 : }
441 :
442 : /* It's safe because the task is inactive. */
443 52 : raw_spin_lock_irqsave(&p->pi_lock, flags);
444 52 : do_set_cpus_allowed(p, mask);
445 52 : p->flags |= PF_NO_SETAFFINITY;
446 52 : raw_spin_unlock_irqrestore(&p->pi_lock, flags);
447 : }
448 :
449 24 : static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
450 : {
451 24 : __kthread_bind_mask(p, cpumask_of(cpu), state);
452 24 : }
453 :
454 28 : void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
455 : {
456 28 : __kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
457 28 : }
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 : */
468 12 : void kthread_bind(struct task_struct *p, unsigned int cpu)
469 : {
470 0 : __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
471 0 : }
472 : EXPORT_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 : */
484 12 : struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
485 : void *data, unsigned int cpu,
486 : const char *namefmt)
487 : {
488 12 : struct task_struct *p;
489 :
490 12 : p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
491 : cpu);
492 12 : if (IS_ERR(p))
493 : return p;
494 12 : kthread_bind(p, cpu);
495 : /* CPU hotplug need to bind once again when unparking the thread. */
496 12 : to_kthread(p)->cpu = cpu;
497 12 : return p;
498 : }
499 :
500 30 : void kthread_set_per_cpu(struct task_struct *k, int cpu)
501 : {
502 30 : struct kthread *kthread = to_kthread(k);
503 30 : if (!kthread)
504 : return;
505 :
506 30 : WARN_ON_ONCE(!(k->flags & PF_NO_SETAFFINITY));
507 :
508 30 : if (cpu < 0) {
509 0 : clear_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
510 0 : return;
511 : }
512 :
513 30 : kthread->cpu = cpu;
514 30 : set_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
515 : }
516 :
517 8137 : bool kthread_is_per_cpu(struct task_struct *k)
518 : {
519 8137 : struct kthread *kthread = to_kthread(k);
520 8142 : if (!kthread)
521 : return false;
522 :
523 7855 : return test_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
524 : }
525 :
526 : /**
527 : * kthread_unpark - unpark a thread created by kthread_create().
528 : * @k: thread created by kthread_create().
529 : *
530 : * Sets kthread_should_park() for @k to return false, wakes it, and
531 : * waits for it to return. If the thread is marked percpu then its
532 : * bound to the cpu again.
533 : */
534 12 : void kthread_unpark(struct task_struct *k)
535 : {
536 12 : struct kthread *kthread = to_kthread(k);
537 :
538 : /*
539 : * Newly created kthread was parked when the CPU was offline.
540 : * The binding was lost and we need to set it again.
541 : */
542 12 : if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
543 12 : __kthread_bind(k, kthread->cpu, TASK_PARKED);
544 :
545 12 : clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
546 : /*
547 : * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup.
548 : */
549 12 : wake_up_state(k, TASK_PARKED);
550 12 : }
551 : EXPORT_SYMBOL_GPL(kthread_unpark);
552 :
553 : /**
554 : * kthread_park - park a thread created by kthread_create().
555 : * @k: thread created by kthread_create().
556 : *
557 : * Sets kthread_should_park() for @k to return true, wakes it, and
558 : * waits for it to return. This can also be called after kthread_create()
559 : * instead of calling wake_up_process(): the thread will park without
560 : * calling threadfn().
561 : *
562 : * Returns 0 if the thread is parked, -ENOSYS if the thread exited.
563 : * If called by the kthread itself just the park bit is set.
564 : */
565 12 : int kthread_park(struct task_struct *k)
566 : {
567 12 : struct kthread *kthread = to_kthread(k);
568 :
569 12 : if (WARN_ON(k->flags & PF_EXITING))
570 : return -ENOSYS;
571 :
572 12 : if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK, &kthread->flags)))
573 : return -EBUSY;
574 :
575 12 : set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
576 12 : if (k != current) {
577 12 : wake_up_process(k);
578 : /*
579 : * Wait for __kthread_parkme() to complete(), this means we
580 : * _will_ have TASK_PARKED and are about to call schedule().
581 : */
582 12 : wait_for_completion(&kthread->parked);
583 : /*
584 : * Now wait for that schedule() to complete and the task to
585 : * get scheduled out.
586 : */
587 12 : WARN_ON_ONCE(!wait_task_inactive(k, TASK_PARKED));
588 : }
589 :
590 : return 0;
591 : }
592 : EXPORT_SYMBOL_GPL(kthread_park);
593 :
594 : /**
595 : * kthread_stop - stop a thread created by kthread_create().
596 : * @k: thread created by kthread_create().
597 : *
598 : * Sets kthread_should_stop() for @k to return true, wakes it, and
599 : * waits for it to exit. This can also be called after kthread_create()
600 : * instead of calling wake_up_process(): the thread will exit without
601 : * calling threadfn().
602 : *
603 : * If threadfn() may call do_exit() itself, the caller must ensure
604 : * task_struct can't go away.
605 : *
606 : * Returns the result of threadfn(), or %-EINTR if wake_up_process()
607 : * was never called.
608 : */
609 0 : int kthread_stop(struct task_struct *k)
610 : {
611 0 : struct kthread *kthread;
612 0 : int ret;
613 :
614 0 : trace_sched_kthread_stop(k);
615 :
616 0 : get_task_struct(k);
617 0 : kthread = to_kthread(k);
618 0 : set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
619 0 : kthread_unpark(k);
620 0 : wake_up_process(k);
621 0 : wait_for_completion(&kthread->exited);
622 0 : ret = k->exit_code;
623 0 : put_task_struct(k);
624 :
625 0 : trace_sched_kthread_stop_ret(ret);
626 0 : return ret;
627 : }
628 : EXPORT_SYMBOL(kthread_stop);
629 :
630 1 : int kthreadd(void *unused)
631 : {
632 1 : struct task_struct *tsk = current;
633 :
634 : /* Setup a clean context for our children to inherit. */
635 1 : set_task_comm(tsk, "kthreadd");
636 1 : ignore_signals(tsk);
637 1 : set_cpus_allowed_ptr(tsk, housekeeping_cpumask(HK_FLAG_KTHREAD));
638 1 : set_mems_allowed(node_states[N_MEMORY]);
639 :
640 1 : current->flags |= PF_NOFREEZE;
641 1 : cgroup_init_kthreadd();
642 :
643 49 : for (;;) {
644 49 : set_current_state(TASK_INTERRUPTIBLE);
645 49 : if (list_empty(&kthread_create_list))
646 49 : schedule();
647 48 : __set_current_state(TASK_RUNNING);
648 :
649 48 : spin_lock(&kthread_create_lock);
650 96 : while (!list_empty(&kthread_create_list)) {
651 48 : struct kthread_create_info *create;
652 :
653 48 : create = list_entry(kthread_create_list.next,
654 : struct kthread_create_info, list);
655 48 : list_del_init(&create->list);
656 48 : spin_unlock(&kthread_create_lock);
657 :
658 48 : create_kthread(create);
659 :
660 144 : spin_lock(&kthread_create_lock);
661 : }
662 97 : spin_unlock(&kthread_create_lock);
663 : }
664 :
665 : return 0;
666 : }
667 :
668 0 : void __kthread_init_worker(struct kthread_worker *worker,
669 : const char *name,
670 : struct lock_class_key *key)
671 : {
672 0 : memset(worker, 0, sizeof(struct kthread_worker));
673 0 : raw_spin_lock_init(&worker->lock);
674 0 : lockdep_set_class_and_name(&worker->lock, key, name);
675 0 : INIT_LIST_HEAD(&worker->work_list);
676 0 : INIT_LIST_HEAD(&worker->delayed_work_list);
677 0 : }
678 : EXPORT_SYMBOL_GPL(__kthread_init_worker);
679 :
680 : /**
681 : * kthread_worker_fn - kthread function to process kthread_worker
682 : * @worker_ptr: pointer to initialized kthread_worker
683 : *
684 : * This function implements the main cycle of kthread worker. It processes
685 : * work_list until it is stopped with kthread_stop(). It sleeps when the queue
686 : * is empty.
687 : *
688 : * The works are not allowed to keep any locks, disable preemption or interrupts
689 : * when they finish. There is defined a safe point for freezing when one work
690 : * finishes and before a new one is started.
691 : *
692 : * Also the works must not be handled by more than one worker at the same time,
693 : * see also kthread_queue_work().
694 : */
695 0 : int kthread_worker_fn(void *worker_ptr)
696 : {
697 0 : struct kthread_worker *worker = worker_ptr;
698 0 : struct kthread_work *work;
699 :
700 : /*
701 : * FIXME: Update the check and remove the assignment when all kthread
702 : * worker users are created using kthread_create_worker*() functions.
703 : */
704 0 : WARN_ON(worker->task && worker->task != current);
705 0 : worker->task = current;
706 :
707 0 : if (worker->flags & KTW_FREEZABLE)
708 : set_freezable();
709 :
710 0 : repeat:
711 0 : set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */
712 :
713 0 : if (kthread_should_stop()) {
714 0 : __set_current_state(TASK_RUNNING);
715 0 : raw_spin_lock_irq(&worker->lock);
716 0 : worker->task = NULL;
717 0 : raw_spin_unlock_irq(&worker->lock);
718 0 : return 0;
719 : }
720 :
721 0 : work = NULL;
722 0 : raw_spin_lock_irq(&worker->lock);
723 0 : if (!list_empty(&worker->work_list)) {
724 0 : work = list_first_entry(&worker->work_list,
725 : struct kthread_work, node);
726 0 : list_del_init(&work->node);
727 : }
728 0 : worker->current_work = work;
729 0 : raw_spin_unlock_irq(&worker->lock);
730 :
731 0 : if (work) {
732 0 : kthread_work_func_t func = work->func;
733 0 : __set_current_state(TASK_RUNNING);
734 0 : trace_sched_kthread_work_execute_start(work);
735 0 : work->func(work);
736 : /*
737 : * Avoid dereferencing work after this point. The trace
738 : * event only cares about the address.
739 : */
740 0 : trace_sched_kthread_work_execute_end(work, func);
741 0 : } else if (!freezing(current))
742 0 : schedule();
743 :
744 0 : try_to_freeze();
745 0 : cond_resched();
746 0 : goto repeat;
747 : }
748 : EXPORT_SYMBOL_GPL(kthread_worker_fn);
749 :
750 : static __printf(3, 0) struct kthread_worker *
751 0 : __kthread_create_worker(int cpu, unsigned int flags,
752 : const char namefmt[], va_list args)
753 : {
754 0 : struct kthread_worker *worker;
755 0 : struct task_struct *task;
756 0 : int node = NUMA_NO_NODE;
757 :
758 0 : worker = kzalloc(sizeof(*worker), GFP_KERNEL);
759 0 : if (!worker)
760 0 : return ERR_PTR(-ENOMEM);
761 :
762 0 : kthread_init_worker(worker);
763 :
764 0 : if (cpu >= 0)
765 0 : node = cpu_to_node(cpu);
766 :
767 0 : task = __kthread_create_on_node(kthread_worker_fn, worker,
768 : node, namefmt, args);
769 0 : if (IS_ERR(task))
770 0 : goto fail_task;
771 :
772 0 : if (cpu >= 0)
773 0 : kthread_bind(task, cpu);
774 :
775 0 : worker->flags = flags;
776 0 : worker->task = task;
777 0 : wake_up_process(task);
778 0 : return worker;
779 :
780 0 : fail_task:
781 0 : kfree(worker);
782 0 : return ERR_CAST(task);
783 : }
784 :
785 : /**
786 : * kthread_create_worker - create a kthread worker
787 : * @flags: flags modifying the default behavior of the worker
788 : * @namefmt: printf-style name for the kthread worker (task).
789 : *
790 : * Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
791 : * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
792 : * when the worker was SIGKILLed.
793 : */
794 : struct kthread_worker *
795 0 : kthread_create_worker(unsigned int flags, const char namefmt[], ...)
796 : {
797 0 : struct kthread_worker *worker;
798 0 : va_list args;
799 :
800 0 : va_start(args, namefmt);
801 0 : worker = __kthread_create_worker(-1, flags, namefmt, args);
802 0 : va_end(args);
803 :
804 0 : return worker;
805 : }
806 : EXPORT_SYMBOL(kthread_create_worker);
807 :
808 : /**
809 : * kthread_create_worker_on_cpu - create a kthread worker and bind it
810 : * to a given CPU and the associated NUMA node.
811 : * @cpu: CPU number
812 : * @flags: flags modifying the default behavior of the worker
813 : * @namefmt: printf-style name for the kthread worker (task).
814 : *
815 : * Use a valid CPU number if you want to bind the kthread worker
816 : * to the given CPU and the associated NUMA node.
817 : *
818 : * A good practice is to add the cpu number also into the worker name.
819 : * For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
820 : *
821 : * CPU hotplug:
822 : * The kthread worker API is simple and generic. It just provides a way
823 : * to create, use, and destroy workers.
824 : *
825 : * It is up to the API user how to handle CPU hotplug. They have to decide
826 : * how to handle pending work items, prevent queuing new ones, and
827 : * restore the functionality when the CPU goes off and on. There are a
828 : * few catches:
829 : *
830 : * - CPU affinity gets lost when it is scheduled on an offline CPU.
831 : *
832 : * - The worker might not exist when the CPU was off when the user
833 : * created the workers.
834 : *
835 : * Good practice is to implement two CPU hotplug callbacks and to
836 : * destroy/create the worker when the CPU goes down/up.
837 : *
838 : * Return:
839 : * The pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
840 : * when the needed structures could not get allocated, and ERR_PTR(-EINTR)
841 : * when the worker was SIGKILLed.
842 : */
843 : struct kthread_worker *
844 0 : kthread_create_worker_on_cpu(int cpu, unsigned int flags,
845 : const char namefmt[], ...)
846 : {
847 0 : struct kthread_worker *worker;
848 0 : va_list args;
849 :
850 0 : va_start(args, namefmt);
851 0 : worker = __kthread_create_worker(cpu, flags, namefmt, args);
852 0 : va_end(args);
853 :
854 0 : return worker;
855 : }
856 : EXPORT_SYMBOL(kthread_create_worker_on_cpu);
857 :
858 : /*
859 : * Returns true when the work could not be queued at the moment.
860 : * It happens when it is already pending in a worker list
861 : * or when it is being cancelled.
862 : */
863 0 : static inline bool queuing_blocked(struct kthread_worker *worker,
864 : struct kthread_work *work)
865 : {
866 0 : lockdep_assert_held(&worker->lock);
867 :
868 0 : return !list_empty(&work->node) || work->canceling;
869 : }
870 :
871 0 : static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
872 : struct kthread_work *work)
873 : {
874 0 : lockdep_assert_held(&worker->lock);
875 0 : WARN_ON_ONCE(!list_empty(&work->node));
876 : /* Do not use a work with >1 worker, see kthread_queue_work() */
877 0 : WARN_ON_ONCE(work->worker && work->worker != worker);
878 0 : }
879 :
880 : /* insert @work before @pos in @worker */
881 0 : static void kthread_insert_work(struct kthread_worker *worker,
882 : struct kthread_work *work,
883 : struct list_head *pos)
884 : {
885 0 : kthread_insert_work_sanity_check(worker, work);
886 :
887 0 : trace_sched_kthread_work_queue_work(worker, work);
888 :
889 0 : list_add_tail(&work->node, pos);
890 0 : work->worker = worker;
891 0 : if (!worker->current_work && likely(worker->task))
892 0 : wake_up_process(worker->task);
893 0 : }
894 :
895 : /**
896 : * kthread_queue_work - queue a kthread_work
897 : * @worker: target kthread_worker
898 : * @work: kthread_work to queue
899 : *
900 : * Queue @work to work processor @task for async execution. @task
901 : * must have been created with kthread_worker_create(). Returns %true
902 : * if @work was successfully queued, %false if it was already pending.
903 : *
904 : * Reinitialize the work if it needs to be used by another worker.
905 : * For example, when the worker was stopped and started again.
906 : */
907 0 : bool kthread_queue_work(struct kthread_worker *worker,
908 : struct kthread_work *work)
909 : {
910 0 : bool ret = false;
911 0 : unsigned long flags;
912 :
913 0 : raw_spin_lock_irqsave(&worker->lock, flags);
914 0 : if (!queuing_blocked(worker, work)) {
915 0 : kthread_insert_work(worker, work, &worker->work_list);
916 0 : ret = true;
917 : }
918 0 : raw_spin_unlock_irqrestore(&worker->lock, flags);
919 0 : return ret;
920 : }
921 : EXPORT_SYMBOL_GPL(kthread_queue_work);
922 :
923 : /**
924 : * kthread_delayed_work_timer_fn - callback that queues the associated kthread
925 : * delayed work when the timer expires.
926 : * @t: pointer to the expired timer
927 : *
928 : * The format of the function is defined by struct timer_list.
929 : * It should have been called from irqsafe timer with irq already off.
930 : */
931 0 : void kthread_delayed_work_timer_fn(struct timer_list *t)
932 : {
933 0 : struct kthread_delayed_work *dwork = from_timer(dwork, t, timer);
934 0 : struct kthread_work *work = &dwork->work;
935 0 : struct kthread_worker *worker = work->worker;
936 0 : unsigned long flags;
937 :
938 : /*
939 : * This might happen when a pending work is reinitialized.
940 : * It means that it is used a wrong way.
941 : */
942 0 : if (WARN_ON_ONCE(!worker))
943 : return;
944 :
945 0 : raw_spin_lock_irqsave(&worker->lock, flags);
946 : /* Work must not be used with >1 worker, see kthread_queue_work(). */
947 0 : WARN_ON_ONCE(work->worker != worker);
948 :
949 : /* Move the work from worker->delayed_work_list. */
950 0 : WARN_ON_ONCE(list_empty(&work->node));
951 0 : list_del_init(&work->node);
952 0 : if (!work->canceling)
953 0 : kthread_insert_work(worker, work, &worker->work_list);
954 :
955 0 : raw_spin_unlock_irqrestore(&worker->lock, flags);
956 : }
957 : EXPORT_SYMBOL(kthread_delayed_work_timer_fn);
958 :
959 0 : static void __kthread_queue_delayed_work(struct kthread_worker *worker,
960 : struct kthread_delayed_work *dwork,
961 : unsigned long delay)
962 : {
963 0 : struct timer_list *timer = &dwork->timer;
964 0 : struct kthread_work *work = &dwork->work;
965 :
966 0 : WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);
967 :
968 : /*
969 : * If @delay is 0, queue @dwork->work immediately. This is for
970 : * both optimization and correctness. The earliest @timer can
971 : * expire is on the closest next tick and delayed_work users depend
972 : * on that there's no such delay when @delay is 0.
973 : */
974 0 : if (!delay) {
975 0 : kthread_insert_work(worker, work, &worker->work_list);
976 0 : return;
977 : }
978 :
979 : /* Be paranoid and try to detect possible races already now. */
980 0 : kthread_insert_work_sanity_check(worker, work);
981 :
982 0 : list_add(&work->node, &worker->delayed_work_list);
983 0 : work->worker = worker;
984 0 : timer->expires = jiffies + delay;
985 0 : add_timer(timer);
986 : }
987 :
988 : /**
989 : * kthread_queue_delayed_work - queue the associated kthread work
990 : * after a delay.
991 : * @worker: target kthread_worker
992 : * @dwork: kthread_delayed_work to queue
993 : * @delay: number of jiffies to wait before queuing
994 : *
995 : * If the work has not been pending it starts a timer that will queue
996 : * the work after the given @delay. If @delay is zero, it queues the
997 : * work immediately.
998 : *
999 : * Return: %false if the @work has already been pending. It means that
1000 : * either the timer was running or the work was queued. It returns %true
1001 : * otherwise.
1002 : */
1003 0 : bool kthread_queue_delayed_work(struct kthread_worker *worker,
1004 : struct kthread_delayed_work *dwork,
1005 : unsigned long delay)
1006 : {
1007 0 : struct kthread_work *work = &dwork->work;
1008 0 : unsigned long flags;
1009 0 : bool ret = false;
1010 :
1011 0 : raw_spin_lock_irqsave(&worker->lock, flags);
1012 :
1013 0 : if (!queuing_blocked(worker, work)) {
1014 0 : __kthread_queue_delayed_work(worker, dwork, delay);
1015 0 : ret = true;
1016 : }
1017 :
1018 0 : raw_spin_unlock_irqrestore(&worker->lock, flags);
1019 0 : return ret;
1020 : }
1021 : EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);
1022 :
1023 : struct kthread_flush_work {
1024 : struct kthread_work work;
1025 : struct completion done;
1026 : };
1027 :
1028 0 : static void kthread_flush_work_fn(struct kthread_work *work)
1029 : {
1030 0 : struct kthread_flush_work *fwork =
1031 0 : container_of(work, struct kthread_flush_work, work);
1032 0 : complete(&fwork->done);
1033 0 : }
1034 :
1035 : /**
1036 : * kthread_flush_work - flush a kthread_work
1037 : * @work: work to flush
1038 : *
1039 : * If @work is queued or executing, wait for it to finish execution.
1040 : */
1041 0 : void kthread_flush_work(struct kthread_work *work)
1042 : {
1043 0 : struct kthread_flush_work fwork = {
1044 : KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1045 0 : COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1046 : };
1047 0 : struct kthread_worker *worker;
1048 0 : bool noop = false;
1049 :
1050 0 : worker = work->worker;
1051 0 : if (!worker)
1052 0 : return;
1053 :
1054 0 : raw_spin_lock_irq(&worker->lock);
1055 : /* Work must not be used with >1 worker, see kthread_queue_work(). */
1056 0 : WARN_ON_ONCE(work->worker != worker);
1057 :
1058 0 : if (!list_empty(&work->node))
1059 0 : kthread_insert_work(worker, &fwork.work, work->node.next);
1060 0 : else if (worker->current_work == work)
1061 0 : kthread_insert_work(worker, &fwork.work,
1062 : worker->work_list.next);
1063 : else
1064 : noop = true;
1065 :
1066 0 : raw_spin_unlock_irq(&worker->lock);
1067 :
1068 0 : if (!noop)
1069 0 : wait_for_completion(&fwork.done);
1070 : }
1071 : EXPORT_SYMBOL_GPL(kthread_flush_work);
1072 :
1073 : /*
1074 : * This function removes the work from the worker queue. Also it makes sure
1075 : * that it won't get queued later via the delayed work's timer.
1076 : *
1077 : * The work might still be in use when this function finishes. See the
1078 : * current_work proceed by the worker.
1079 : *
1080 : * Return: %true if @work was pending and successfully canceled,
1081 : * %false if @work was not pending
1082 : */
1083 0 : static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
1084 : unsigned long *flags)
1085 : {
1086 : /* Try to cancel the timer if exists. */
1087 0 : if (is_dwork) {
1088 0 : struct kthread_delayed_work *dwork =
1089 0 : container_of(work, struct kthread_delayed_work, work);
1090 0 : struct kthread_worker *worker = work->worker;
1091 :
1092 : /*
1093 : * del_timer_sync() must be called to make sure that the timer
1094 : * callback is not running. The lock must be temporary released
1095 : * to avoid a deadlock with the callback. In the meantime,
1096 : * any queuing is blocked by setting the canceling counter.
1097 : */
1098 0 : work->canceling++;
1099 0 : raw_spin_unlock_irqrestore(&worker->lock, *flags);
1100 0 : del_timer_sync(&dwork->timer);
1101 0 : raw_spin_lock_irqsave(&worker->lock, *flags);
1102 0 : work->canceling--;
1103 : }
1104 :
1105 : /*
1106 : * Try to remove the work from a worker list. It might either
1107 : * be from worker->work_list or from worker->delayed_work_list.
1108 : */
1109 0 : if (!list_empty(&work->node)) {
1110 0 : list_del_init(&work->node);
1111 0 : return true;
1112 : }
1113 :
1114 : return false;
1115 : }
1116 :
1117 : /**
1118 : * kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
1119 : * @worker: kthread worker to use
1120 : * @dwork: kthread delayed work to queue
1121 : * @delay: number of jiffies to wait before queuing
1122 : *
1123 : * If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
1124 : * modify @dwork's timer so that it expires after @delay. If @delay is zero,
1125 : * @work is guaranteed to be queued immediately.
1126 : *
1127 : * Return: %true if @dwork was pending and its timer was modified,
1128 : * %false otherwise.
1129 : *
1130 : * A special case is when the work is being canceled in parallel.
1131 : * It might be caused either by the real kthread_cancel_delayed_work_sync()
1132 : * or yet another kthread_mod_delayed_work() call. We let the other command
1133 : * win and return %false here. The caller is supposed to synchronize these
1134 : * operations a reasonable way.
1135 : *
1136 : * This function is safe to call from any context including IRQ handler.
1137 : * See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
1138 : * for details.
1139 : */
1140 0 : bool kthread_mod_delayed_work(struct kthread_worker *worker,
1141 : struct kthread_delayed_work *dwork,
1142 : unsigned long delay)
1143 : {
1144 0 : struct kthread_work *work = &dwork->work;
1145 0 : unsigned long flags;
1146 0 : int ret = false;
1147 :
1148 0 : raw_spin_lock_irqsave(&worker->lock, flags);
1149 :
1150 : /* Do not bother with canceling when never queued. */
1151 0 : if (!work->worker)
1152 0 : goto fast_queue;
1153 :
1154 : /* Work must not be used with >1 worker, see kthread_queue_work() */
1155 0 : WARN_ON_ONCE(work->worker != worker);
1156 :
1157 : /* Do not fight with another command that is canceling this work. */
1158 0 : if (work->canceling)
1159 0 : goto out;
1160 :
1161 0 : ret = __kthread_cancel_work(work, true, &flags);
1162 0 : fast_queue:
1163 0 : __kthread_queue_delayed_work(worker, dwork, delay);
1164 0 : out:
1165 0 : raw_spin_unlock_irqrestore(&worker->lock, flags);
1166 0 : return ret;
1167 : }
1168 : EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);
1169 :
1170 0 : static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
1171 : {
1172 0 : struct kthread_worker *worker = work->worker;
1173 0 : unsigned long flags;
1174 0 : int ret = false;
1175 :
1176 0 : if (!worker)
1177 0 : goto out;
1178 :
1179 0 : raw_spin_lock_irqsave(&worker->lock, flags);
1180 : /* Work must not be used with >1 worker, see kthread_queue_work(). */
1181 0 : WARN_ON_ONCE(work->worker != worker);
1182 :
1183 0 : ret = __kthread_cancel_work(work, is_dwork, &flags);
1184 :
1185 0 : if (worker->current_work != work)
1186 0 : goto out_fast;
1187 :
1188 : /*
1189 : * The work is in progress and we need to wait with the lock released.
1190 : * In the meantime, block any queuing by setting the canceling counter.
1191 : */
1192 0 : work->canceling++;
1193 0 : raw_spin_unlock_irqrestore(&worker->lock, flags);
1194 0 : kthread_flush_work(work);
1195 0 : raw_spin_lock_irqsave(&worker->lock, flags);
1196 0 : work->canceling--;
1197 :
1198 0 : out_fast:
1199 0 : raw_spin_unlock_irqrestore(&worker->lock, flags);
1200 0 : out:
1201 0 : return ret;
1202 : }
1203 :
1204 : /**
1205 : * kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
1206 : * @work: the kthread work to cancel
1207 : *
1208 : * Cancel @work and wait for its execution to finish. This function
1209 : * can be used even if the work re-queues itself. On return from this
1210 : * function, @work is guaranteed to be not pending or executing on any CPU.
1211 : *
1212 : * kthread_cancel_work_sync(&delayed_work->work) must not be used for
1213 : * delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
1214 : *
1215 : * The caller must ensure that the worker on which @work was last
1216 : * queued can't be destroyed before this function returns.
1217 : *
1218 : * Return: %true if @work was pending, %false otherwise.
1219 : */
1220 0 : bool kthread_cancel_work_sync(struct kthread_work *work)
1221 : {
1222 0 : return __kthread_cancel_work_sync(work, false);
1223 : }
1224 : EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);
1225 :
1226 : /**
1227 : * kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
1228 : * wait for it to finish.
1229 : * @dwork: the kthread delayed work to cancel
1230 : *
1231 : * This is kthread_cancel_work_sync() for delayed works.
1232 : *
1233 : * Return: %true if @dwork was pending, %false otherwise.
1234 : */
1235 0 : bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
1236 : {
1237 0 : return __kthread_cancel_work_sync(&dwork->work, true);
1238 : }
1239 : EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
1240 :
1241 : /**
1242 : * kthread_flush_worker - flush all current works on a kthread_worker
1243 : * @worker: worker to flush
1244 : *
1245 : * Wait until all currently executing or pending works on @worker are
1246 : * finished.
1247 : */
1248 0 : void kthread_flush_worker(struct kthread_worker *worker)
1249 : {
1250 0 : struct kthread_flush_work fwork = {
1251 : KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
1252 0 : COMPLETION_INITIALIZER_ONSTACK(fwork.done),
1253 : };
1254 :
1255 0 : kthread_queue_work(worker, &fwork.work);
1256 0 : wait_for_completion(&fwork.done);
1257 0 : }
1258 : EXPORT_SYMBOL_GPL(kthread_flush_worker);
1259 :
1260 : /**
1261 : * kthread_destroy_worker - destroy a kthread worker
1262 : * @worker: worker to be destroyed
1263 : *
1264 : * Flush and destroy @worker. The simple flush is enough because the kthread
1265 : * worker API is used only in trivial scenarios. There are no multi-step state
1266 : * machines needed.
1267 : */
1268 0 : void kthread_destroy_worker(struct kthread_worker *worker)
1269 : {
1270 0 : struct task_struct *task;
1271 :
1272 0 : task = worker->task;
1273 0 : if (WARN_ON(!task))
1274 : return;
1275 :
1276 0 : kthread_flush_worker(worker);
1277 0 : kthread_stop(task);
1278 0 : WARN_ON(!list_empty(&worker->work_list));
1279 0 : kfree(worker);
1280 : }
1281 : EXPORT_SYMBOL(kthread_destroy_worker);
1282 :
1283 : /**
1284 : * kthread_use_mm - make the calling kthread operate on an address space
1285 : * @mm: address space to operate on
1286 : */
1287 0 : void kthread_use_mm(struct mm_struct *mm)
1288 : {
1289 0 : struct mm_struct *active_mm;
1290 0 : struct task_struct *tsk = current;
1291 :
1292 0 : WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
1293 0 : WARN_ON_ONCE(tsk->mm);
1294 :
1295 0 : task_lock(tsk);
1296 : /* Hold off tlb flush IPIs while switching mm's */
1297 0 : local_irq_disable();
1298 0 : active_mm = tsk->active_mm;
1299 0 : if (active_mm != mm) {
1300 0 : mmgrab(mm);
1301 0 : tsk->active_mm = mm;
1302 : }
1303 0 : tsk->mm = mm;
1304 0 : membarrier_update_current_mm(mm);
1305 0 : switch_mm_irqs_off(active_mm, mm, tsk);
1306 0 : local_irq_enable();
1307 0 : task_unlock(tsk);
1308 : #ifdef finish_arch_post_lock_switch
1309 : finish_arch_post_lock_switch();
1310 : #endif
1311 :
1312 : /*
1313 : * When a kthread starts operating on an address space, the loop
1314 : * in membarrier_{private,global}_expedited() may not observe
1315 : * that tsk->mm, and not issue an IPI. Membarrier requires a
1316 : * memory barrier after storing to tsk->mm, before accessing
1317 : * user-space memory. A full memory barrier for membarrier
1318 : * {PRIVATE,GLOBAL}_EXPEDITED is implicitly provided by
1319 : * mmdrop(), or explicitly with smp_mb().
1320 : */
1321 0 : if (active_mm != mm)
1322 0 : mmdrop(active_mm);
1323 : else
1324 0 : smp_mb();
1325 :
1326 0 : to_kthread(tsk)->oldfs = force_uaccess_begin();
1327 0 : }
1328 : EXPORT_SYMBOL_GPL(kthread_use_mm);
1329 :
1330 : /**
1331 : * kthread_unuse_mm - reverse the effect of kthread_use_mm()
1332 : * @mm: address space to operate on
1333 : */
1334 0 : void kthread_unuse_mm(struct mm_struct *mm)
1335 : {
1336 0 : struct task_struct *tsk = current;
1337 :
1338 0 : WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
1339 0 : WARN_ON_ONCE(!tsk->mm);
1340 :
1341 0 : force_uaccess_end(to_kthread(tsk)->oldfs);
1342 :
1343 0 : task_lock(tsk);
1344 : /*
1345 : * When a kthread stops operating on an address space, the loop
1346 : * in membarrier_{private,global}_expedited() may not observe
1347 : * that tsk->mm, and not issue an IPI. Membarrier requires a
1348 : * memory barrier after accessing user-space memory, before
1349 : * clearing tsk->mm.
1350 : */
1351 0 : smp_mb__after_spinlock();
1352 0 : sync_mm_rss(mm);
1353 0 : local_irq_disable();
1354 0 : tsk->mm = NULL;
1355 0 : membarrier_update_current_mm(NULL);
1356 : /* active_mm is still 'mm' */
1357 0 : enter_lazy_tlb(mm, tsk);
1358 0 : local_irq_enable();
1359 0 : task_unlock(tsk);
1360 0 : }
1361 : EXPORT_SYMBOL_GPL(kthread_unuse_mm);
1362 :
1363 : #ifdef CONFIG_BLK_CGROUP
1364 : /**
1365 : * kthread_associate_blkcg - associate blkcg to current kthread
1366 : * @css: the cgroup info
1367 : *
1368 : * Current thread must be a kthread. The thread is running jobs on behalf of
1369 : * other threads. In some cases, we expect the jobs attach cgroup info of
1370 : * original threads instead of that of current thread. This function stores
1371 : * original thread's cgroup info in current kthread context for later
1372 : * retrieval.
1373 : */
1374 : void kthread_associate_blkcg(struct cgroup_subsys_state *css)
1375 : {
1376 : struct kthread *kthread;
1377 :
1378 : if (!(current->flags & PF_KTHREAD))
1379 : return;
1380 : kthread = to_kthread(current);
1381 : if (!kthread)
1382 : return;
1383 :
1384 : if (kthread->blkcg_css) {
1385 : css_put(kthread->blkcg_css);
1386 : kthread->blkcg_css = NULL;
1387 : }
1388 : if (css) {
1389 : css_get(css);
1390 : kthread->blkcg_css = css;
1391 : }
1392 : }
1393 : EXPORT_SYMBOL(kthread_associate_blkcg);
1394 :
1395 : /**
1396 : * kthread_blkcg - get associated blkcg css of current kthread
1397 : *
1398 : * Current thread must be a kthread.
1399 : */
1400 : struct cgroup_subsys_state *kthread_blkcg(void)
1401 : {
1402 : struct kthread *kthread;
1403 :
1404 : if (current->flags & PF_KTHREAD) {
1405 : kthread = to_kthread(current);
1406 : if (kthread)
1407 : return kthread->blkcg_css;
1408 : }
1409 : return NULL;
1410 : }
1411 : EXPORT_SYMBOL(kthread_blkcg);
1412 : #endif
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