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 | 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 | |
53 | struct 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 | |
68 | enum KTHREAD_BITS { |
69 | KTHREAD_IS_PER_CPU = 0, |
70 | KTHREAD_SHOULD_STOP, |
71 | KTHREAD_SHOULD_PARK, |
72 | }; |
73 | |
74 | static 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 | */ |
91 | static 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 | |
99 | void get_kthread_comm(char *buf, size_t buf_size, struct task_struct *tsk) |
100 | { |
101 | struct kthread *kthread = to_kthread(k: tsk); |
102 | |
103 | if (!kthread || !kthread->full_name) { |
104 | __get_task_comm(to: buf, len: buf_size, tsk); |
105 | return; |
106 | } |
107 | |
108 | strscpy_pad(dest: buf, src: kthread->full_name, count: buf_size); |
109 | } |
110 | |
111 | bool 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(size: sizeof(*kthread), GFP_KERNEL); |
119 | if (!kthread) |
120 | return false; |
121 | |
122 | init_completion(x: &kthread->exited); |
123 | init_completion(x: &kthread->parked); |
124 | p->vfork_done = &kthread->exited; |
125 | |
126 | p->worker_private = kthread; |
127 | return true; |
128 | } |
129 | |
130 | void 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(objp: kthread->full_name); |
146 | kfree(objp: 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 | */ |
156 | bool kthread_should_stop(void) |
157 | { |
158 | return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags); |
159 | } |
160 | EXPORT_SYMBOL(kthread_should_stop); |
161 | |
162 | static 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 | */ |
178 | bool kthread_should_park(void) |
179 | { |
180 | return __kthread_should_park(current); |
181 | } |
182 | EXPORT_SYMBOL_GPL(kthread_should_park); |
183 | |
184 | bool 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 | */ |
203 | bool 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(check_kthr_stop: true); |
211 | |
212 | if (was_frozen) |
213 | *was_frozen = frozen; |
214 | |
215 | return kthread_should_stop(); |
216 | } |
217 | EXPORT_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 | */ |
225 | void *kthread_func(struct task_struct *task) |
226 | { |
227 | struct kthread *kthread = __to_kthread(p: task); |
228 | if (kthread) |
229 | return kthread->threadfn; |
230 | return NULL; |
231 | } |
232 | EXPORT_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 | */ |
242 | void *kthread_data(struct task_struct *task) |
243 | { |
244 | return to_kthread(k: task)->data; |
245 | } |
246 | EXPORT_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 | */ |
257 | void *kthread_probe_data(struct task_struct *task) |
258 | { |
259 | struct kthread *kthread = __to_kthread(p: task); |
260 | void *data = NULL; |
261 | |
262 | if (kthread) |
263 | copy_from_kernel_nofault(dst: &data, src: &kthread->data, size: sizeof(data)); |
264 | return data; |
265 | } |
266 | |
267 | static 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 | |
296 | void kthread_parkme(void) |
297 | { |
298 | __kthread_parkme(self: to_kthread(current)); |
299 | } |
300 | EXPORT_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 | */ |
312 | void __noreturn kthread_exit(long result) |
313 | { |
314 | struct kthread *kthread = to_kthread(current); |
315 | kthread->result = result; |
316 | do_exit(error_code: 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 | */ |
331 | void __noreturn kthread_complete_and_exit(struct completion *comp, long code) |
332 | { |
333 | if (comp) |
334 | complete(comp); |
335 | |
336 | kthread_exit(result: code); |
337 | } |
338 | EXPORT_SYMBOL(kthread_complete_and_exit); |
339 | |
340 | static 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(objp: create->full_name); |
357 | kfree(objp: create); |
358 | kthread_exit(result: -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, new_mask: housekeeping_cpumask(type: 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(result: ret); |
391 | } |
392 | |
393 | /* called from kernel_clone() to get node information for about to be created task */ |
394 | int 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 | |
403 | static 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(fn: kthread, arg: create, name: 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(objp: create->full_name); |
418 | if (!done) { |
419 | kfree(objp: create); |
420 | return; |
421 | } |
422 | create->result = ERR_PTR(error: pid); |
423 | complete(done); |
424 | } |
425 | } |
426 | |
427 | static __printf(4, 0) |
428 | struct 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(size: sizeof(*create), |
436 | GFP_KERNEL); |
437 | |
438 | if (!create) |
439 | return ERR_PTR(error: -ENOMEM); |
440 | create->threadfn = threadfn; |
441 | create->data = data; |
442 | create->node = node; |
443 | create->done = &done; |
444 | create->full_name = kvasprintf(GFP_KERNEL, fmt: namefmt, args); |
445 | if (!create->full_name) { |
446 | task = ERR_PTR(error: -ENOMEM); |
447 | goto free_create; |
448 | } |
449 | |
450 | spin_lock(lock: &kthread_create_lock); |
451 | list_add_tail(new: &create->list, head: &kthread_create_list); |
452 | spin_unlock(lock: &kthread_create_lock); |
453 | |
454 | wake_up_process(tsk: 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(error: -EINTR); |
468 | /* |
469 | * kthreadd (or new kernel thread) will call complete() |
470 | * shortly. |
471 | */ |
472 | wait_for_completion(&done); |
473 | } |
474 | task = create->result; |
475 | free_create: |
476 | kfree(objp: 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 | */ |
503 | struct 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 | } |
517 | EXPORT_SYMBOL(kthread_create_on_node); |
518 | |
519 | static 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, match_state: 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, new_mask: mask); |
531 | p->flags |= PF_NO_SETAFFINITY; |
532 | raw_spin_unlock_irqrestore(&p->pi_lock, flags); |
533 | } |
534 | |
535 | static 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 | |
540 | void 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 | */ |
554 | void kthread_bind(struct task_struct *p, unsigned int cpu) |
555 | { |
556 | __kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE); |
557 | } |
558 | EXPORT_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 | */ |
570 | struct 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(ptr: p)) |
579 | return p; |
580 | kthread_bind(p, cpu); |
581 | /* CPU hotplug need to bind once again when unparking the thread. */ |
582 | to_kthread(k: p)->cpu = cpu; |
583 | return p; |
584 | } |
585 | EXPORT_SYMBOL(kthread_create_on_cpu); |
586 | |
587 | void 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(nr: KTHREAD_IS_PER_CPU, addr: &kthread->flags); |
597 | return; |
598 | } |
599 | |
600 | kthread->cpu = cpu; |
601 | set_bit(nr: KTHREAD_IS_PER_CPU, addr: &kthread->flags); |
602 | } |
603 | |
604 | bool 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 | */ |
621 | void 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(p: k, cpu: kthread->cpu, TASK_PARKED); |
631 | |
632 | clear_bit(nr: KTHREAD_SHOULD_PARK, addr: &kthread->flags); |
633 | /* |
634 | * __kthread_parkme() will either see !SHOULD_PARK or get the wakeup. |
635 | */ |
636 | wake_up_state(tsk: k, TASK_PARKED); |
637 | } |
638 | EXPORT_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 | */ |
652 | int 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(nr: KTHREAD_SHOULD_PARK, addr: &kthread->flags); |
663 | if (k != current) { |
664 | wake_up_process(tsk: 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 | } |
679 | EXPORT_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 | */ |
696 | int kthread_stop(struct task_struct *k) |
697 | { |
698 | struct kthread *kthread; |
699 | int ret; |
700 | |
701 | trace_sched_kthread_stop(t: k); |
702 | |
703 | get_task_struct(t: k); |
704 | kthread = to_kthread(k); |
705 | set_bit(nr: KTHREAD_SHOULD_STOP, addr: &kthread->flags); |
706 | kthread_unpark(k); |
707 | set_tsk_thread_flag(tsk: k, TIF_NOTIFY_SIGNAL); |
708 | wake_up_process(tsk: k); |
709 | wait_for_completion(&kthread->exited); |
710 | ret = kthread->result; |
711 | put_task_struct(t: k); |
712 | |
713 | trace_sched_kthread_stop_ret(ret); |
714 | return ret; |
715 | } |
716 | EXPORT_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 | */ |
726 | int kthread_stop_put(struct task_struct *k) |
727 | { |
728 | int ret; |
729 | |
730 | ret = kthread_stop(k); |
731 | put_task_struct(t: k); |
732 | return ret; |
733 | } |
734 | EXPORT_SYMBOL(kthread_stop_put); |
735 | |
736 | int 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, from: "kthreadd" ); |
742 | ignore_signals(tsk); |
743 | set_cpus_allowed_ptr(p: tsk, new_mask: housekeeping_cpumask(type: 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(head: &kthread_create_list)) |
752 | schedule(); |
753 | __set_current_state(TASK_RUNNING); |
754 | |
755 | spin_lock(lock: &kthread_create_lock); |
756 | while (!list_empty(head: &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(entry: &create->list); |
762 | spin_unlock(lock: &kthread_create_lock); |
763 | |
764 | create_kthread(create); |
765 | |
766 | spin_lock(lock: &kthread_create_lock); |
767 | } |
768 | spin_unlock(lock: &kthread_create_lock); |
769 | } |
770 | |
771 | return 0; |
772 | } |
773 | |
774 | void __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(list: &worker->work_list); |
782 | INIT_LIST_HEAD(list: &worker->delayed_work_list); |
783 | } |
784 | EXPORT_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 | */ |
801 | int 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 | |
816 | repeat: |
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(head: &worker->work_list)) { |
830 | work = list_first_entry(&worker->work_list, |
831 | struct kthread_work, node); |
832 | list_del_init(entry: &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, function: func); |
847 | } else if (!freezing(current)) |
848 | schedule(); |
849 | |
850 | try_to_freeze(); |
851 | cond_resched(); |
852 | goto repeat; |
853 | } |
854 | EXPORT_SYMBOL_GPL(kthread_worker_fn); |
855 | |
856 | static __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(size: sizeof(*worker), GFP_KERNEL); |
865 | if (!worker) |
866 | return ERR_PTR(error: -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(threadfn: kthread_worker_fn, data: worker, |
874 | node, namefmt, args); |
875 | if (IS_ERR(ptr: 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(tsk: task); |
884 | return worker; |
885 | |
886 | fail_task: |
887 | kfree(objp: worker); |
888 | return ERR_CAST(ptr: 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 | */ |
900 | struct kthread_worker * |
901 | kthread_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(cpu: -1, flags, namefmt, args); |
908 | va_end(args); |
909 | |
910 | return worker; |
911 | } |
912 | EXPORT_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 | */ |
949 | struct kthread_worker * |
950 | kthread_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 | } |
962 | EXPORT_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 | */ |
969 | static 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(head: &work->node) || work->canceling; |
975 | } |
976 | |
977 | static 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 */ |
987 | static 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(new: &work->node, head: pos); |
996 | work->worker = worker; |
997 | if (!worker->current_work && likely(worker->task)) |
998 | wake_up_process(tsk: 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 | */ |
1013 | bool 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, pos: &worker->work_list); |
1022 | ret = true; |
1023 | } |
1024 | raw_spin_unlock_irqrestore(&worker->lock, flags); |
1025 | return ret; |
1026 | } |
1027 | EXPORT_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 | */ |
1037 | void 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(entry: &work->node); |
1058 | if (!work->canceling) |
1059 | kthread_insert_work(worker, work, pos: &worker->work_list); |
1060 | |
1061 | raw_spin_unlock_irqrestore(&worker->lock, flags); |
1062 | } |
1063 | EXPORT_SYMBOL(kthread_delayed_work_timer_fn); |
1064 | |
1065 | static 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, pos: &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(new: &work->node, head: &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 | */ |
1109 | bool 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 | } |
1127 | EXPORT_SYMBOL_GPL(kthread_queue_delayed_work); |
1128 | |
1129 | struct kthread_flush_work { |
1130 | struct kthread_work work; |
1131 | struct completion done; |
1132 | }; |
1133 | |
1134 | static 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 | */ |
1147 | void 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(head: &work->node)) |
1165 | kthread_insert_work(worker, work: &fwork.work, pos: work->node.next); |
1166 | else if (worker->current_work == work) |
1167 | kthread_insert_work(worker, work: &fwork.work, |
1168 | pos: 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 | } |
1177 | EXPORT_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 | */ |
1186 | static 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(timer: &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 | */ |
1219 | static 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(head: &work->node)) { |
1226 | list_del_init(entry: &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 | */ |
1256 | bool 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: &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 | |
1295 | fast_queue: |
1296 | __kthread_queue_delayed_work(worker, dwork, delay); |
1297 | out: |
1298 | raw_spin_unlock_irqrestore(&worker->lock, flags); |
1299 | return ret; |
1300 | } |
1301 | EXPORT_SYMBOL_GPL(kthread_mod_delayed_work); |
1302 | |
1303 | static 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: &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 | |
1334 | out_fast: |
1335 | raw_spin_unlock_irqrestore(&worker->lock, flags); |
1336 | out: |
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 | */ |
1356 | bool kthread_cancel_work_sync(struct kthread_work *work) |
1357 | { |
1358 | return __kthread_cancel_work_sync(work, is_dwork: false); |
1359 | } |
1360 | EXPORT_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 | */ |
1371 | bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork) |
1372 | { |
1373 | return __kthread_cancel_work_sync(work: &dwork->work, is_dwork: true); |
1374 | } |
1375 | EXPORT_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 | */ |
1384 | void 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 | } |
1394 | EXPORT_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 | */ |
1408 | void 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(objp: worker); |
1421 | } |
1422 | EXPORT_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 | */ |
1428 | void 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(p: 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(next_mm: mm); |
1450 | switch_mm_irqs_off(prev: active_mm, next: mm, tsk); |
1451 | local_irq_enable(); |
1452 | task_unlock(p: 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(mm: active_mm); |
1467 | } |
1468 | EXPORT_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 | */ |
1474 | void 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(p: 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(p: tsk); |
1498 | |
1499 | mmdrop(mm); |
1500 | } |
1501 | EXPORT_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 | */ |
1514 | void 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(css: kthread->blkcg_css); |
1526 | kthread->blkcg_css = NULL; |
1527 | } |
1528 | if (css) { |
1529 | css_get(css); |
1530 | kthread->blkcg_css = css; |
1531 | } |
1532 | } |
1533 | EXPORT_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 | */ |
1540 | struct 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 |
1552 | |