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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Generic waiting primitives.
4 *
5 * (C) 2004 Nadia Yvette Chambers, Oracle
6 */
7#include "sched.h"
8
9void __init_waitqueue_head(struct wait_queue_head *wq_head, const char *name, struct lock_class_key *key)
10{
11 spin_lock_init(&wq_head->lock);
12 lockdep_set_class_and_name(&wq_head->lock, key, name);
13 INIT_LIST_HEAD(&wq_head->head);
14}
15
16EXPORT_SYMBOL(__init_waitqueue_head);
17
18void add_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
19{
20 unsigned long flags;
21
22 wq_entry->flags &= ~WQ_FLAG_EXCLUSIVE;
23 spin_lock_irqsave(&wq_head->lock, flags);
24 __add_wait_queue(wq_head, wq_entry);
25 spin_unlock_irqrestore(&wq_head->lock, flags);
26}
27EXPORT_SYMBOL(add_wait_queue);
28
29void add_wait_queue_exclusive(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
30{
31 unsigned long flags;
32
33 wq_entry->flags |= WQ_FLAG_EXCLUSIVE;
34 spin_lock_irqsave(&wq_head->lock, flags);
35 __add_wait_queue_entry_tail(wq_head, wq_entry);
36 spin_unlock_irqrestore(&wq_head->lock, flags);
37}
38EXPORT_SYMBOL(add_wait_queue_exclusive);
39
40void remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
41{
42 unsigned long flags;
43
44 spin_lock_irqsave(&wq_head->lock, flags);
45 __remove_wait_queue(wq_head, wq_entry);
46 spin_unlock_irqrestore(&wq_head->lock, flags);
47}
48EXPORT_SYMBOL(remove_wait_queue);
49
50/*
51 * Scan threshold to break wait queue walk.
52 * This allows a waker to take a break from holding the
53 * wait queue lock during the wait queue walk.
54 */
55#define WAITQUEUE_WALK_BREAK_CNT 64
56
57/*
58 * The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
59 * wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
60 * number) then we wake all the non-exclusive tasks and one exclusive task.
61 *
62 * There are circumstances in which we can try to wake a task which has already
63 * started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
64 * zero in this (rare) case, and we handle it by continuing to scan the queue.
65 */
66static int __wake_up_common(struct wait_queue_head *wq_head, unsigned int mode,
67 int nr_exclusive, int wake_flags, void *key,
68 wait_queue_entry_t *bookmark)
69{
70 wait_queue_entry_t *curr, *next;
71 int cnt = 0;
72
73 lockdep_assert_held(&wq_head->lock);
74
75 if (bookmark && (bookmark->flags & WQ_FLAG_BOOKMARK)) {
76 curr = list_next_entry(bookmark, entry);
77
78 list_del(&bookmark->entry);
79 bookmark->flags = 0;
80 } else
81 curr = list_first_entry(&wq_head->head, wait_queue_entry_t, entry);
82
83 if (&curr->entry == &wq_head->head)
84 return nr_exclusive;
85
86 list_for_each_entry_safe_from(curr, next, &wq_head->head, entry) {
87 unsigned flags = curr->flags;
88 int ret;
89
90 if (flags & WQ_FLAG_BOOKMARK)
91 continue;
92
93 ret = curr->func(curr, mode, wake_flags, key);
94 if (ret < 0)
95 break;
96 if (ret && (flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive)
97 break;
98
99 if (bookmark && (++cnt > WAITQUEUE_WALK_BREAK_CNT) &&
100 (&next->entry != &wq_head->head)) {
101 bookmark->flags = WQ_FLAG_BOOKMARK;
102 list_add_tail(&bookmark->entry, &next->entry);
103 break;
104 }
105 }
106
107 return nr_exclusive;
108}
109
110static void __wake_up_common_lock(struct wait_queue_head *wq_head, unsigned int mode,
111 int nr_exclusive, int wake_flags, void *key)
112{
113 unsigned long flags;
114 wait_queue_entry_t bookmark;
115
116 bookmark.flags = 0;
117 bookmark.private = NULL;
118 bookmark.func = NULL;
119 INIT_LIST_HEAD(&bookmark.entry);
120
121 do {
122 spin_lock_irqsave(&wq_head->lock, flags);
123 nr_exclusive = __wake_up_common(wq_head, mode, nr_exclusive,
124 wake_flags, key, &bookmark);
125 spin_unlock_irqrestore(&wq_head->lock, flags);
126 } while (bookmark.flags & WQ_FLAG_BOOKMARK);
127}
128
129/**
130 * __wake_up - wake up threads blocked on a waitqueue.
131 * @wq_head: the waitqueue
132 * @mode: which threads
133 * @nr_exclusive: how many wake-one or wake-many threads to wake up
134 * @key: is directly passed to the wakeup function
135 *
136 * If this function wakes up a task, it executes a full memory barrier before
137 * accessing the task state.
138 */
139void __wake_up(struct wait_queue_head *wq_head, unsigned int mode,
140 int nr_exclusive, void *key)
141{
142 __wake_up_common_lock(wq_head, mode, nr_exclusive, 0, key);
143}
144EXPORT_SYMBOL(__wake_up);
145
146/*
147 * Same as __wake_up but called with the spinlock in wait_queue_head_t held.
148 */
149void __wake_up_locked(struct wait_queue_head *wq_head, unsigned int mode, int nr)
150{
151 __wake_up_common(wq_head, mode, nr, 0, NULL, NULL);
152}
153EXPORT_SYMBOL_GPL(__wake_up_locked);
154
155void __wake_up_locked_key(struct wait_queue_head *wq_head, unsigned int mode, void *key)
156{
157 __wake_up_common(wq_head, mode, 1, 0, key, NULL);
158}
159EXPORT_SYMBOL_GPL(__wake_up_locked_key);
160
161void __wake_up_locked_key_bookmark(struct wait_queue_head *wq_head,
162 unsigned int mode, void *key, wait_queue_entry_t *bookmark)
163{
164 __wake_up_common(wq_head, mode, 1, 0, key, bookmark);
165}
166EXPORT_SYMBOL_GPL(__wake_up_locked_key_bookmark);
167
168/**
169 * __wake_up_sync_key - wake up threads blocked on a waitqueue.
170 * @wq_head: the waitqueue
171 * @mode: which threads
172 * @nr_exclusive: how many wake-one or wake-many threads to wake up
173 * @key: opaque value to be passed to wakeup targets
174 *
175 * The sync wakeup differs that the waker knows that it will schedule
176 * away soon, so while the target thread will be woken up, it will not
177 * be migrated to another CPU - ie. the two threads are 'synchronized'
178 * with each other. This can prevent needless bouncing between CPUs.
179 *
180 * On UP it can prevent extra preemption.
181 *
182 * If this function wakes up a task, it executes a full memory barrier before
183 * accessing the task state.
184 */
185void __wake_up_sync_key(struct wait_queue_head *wq_head, unsigned int mode,
186 int nr_exclusive, void *key)
187{
188 int wake_flags = 1; /* XXX WF_SYNC */
189
190 if (unlikely(!wq_head))
191 return;
192
193 if (unlikely(nr_exclusive != 1))
194 wake_flags = 0;
195
196 __wake_up_common_lock(wq_head, mode, nr_exclusive, wake_flags, key);
197}
198EXPORT_SYMBOL_GPL(__wake_up_sync_key);
199
200/*
201 * __wake_up_sync - see __wake_up_sync_key()
202 */
203void __wake_up_sync(struct wait_queue_head *wq_head, unsigned int mode, int nr_exclusive)
204{
205 __wake_up_sync_key(wq_head, mode, nr_exclusive, NULL);
206}
207EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */
208
209/*
210 * Note: we use "set_current_state()" _after_ the wait-queue add,
211 * because we need a memory barrier there on SMP, so that any
212 * wake-function that tests for the wait-queue being active
213 * will be guaranteed to see waitqueue addition _or_ subsequent
214 * tests in this thread will see the wakeup having taken place.
215 *
216 * The spin_unlock() itself is semi-permeable and only protects
217 * one way (it only protects stuff inside the critical region and
218 * stops them from bleeding out - it would still allow subsequent
219 * loads to move into the critical region).
220 */
221void
222prepare_to_wait(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state)
223{
224 unsigned long flags;
225
226 wq_entry->flags &= ~WQ_FLAG_EXCLUSIVE;
227 spin_lock_irqsave(&wq_head->lock, flags);
228 if (list_empty(&wq_entry->entry))
229 __add_wait_queue(wq_head, wq_entry);
230 set_current_state(state);
231 spin_unlock_irqrestore(&wq_head->lock, flags);
232}
233EXPORT_SYMBOL(prepare_to_wait);
234
235void
236prepare_to_wait_exclusive(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state)
237{
238 unsigned long flags;
239
240 wq_entry->flags |= WQ_FLAG_EXCLUSIVE;
241 spin_lock_irqsave(&wq_head->lock, flags);
242 if (list_empty(&wq_entry->entry))
243 __add_wait_queue_entry_tail(wq_head, wq_entry);
244 set_current_state(state);
245 spin_unlock_irqrestore(&wq_head->lock, flags);
246}
247EXPORT_SYMBOL(prepare_to_wait_exclusive);
248
249void init_wait_entry(struct wait_queue_entry *wq_entry, int flags)
250{
251 wq_entry->flags = flags;
252 wq_entry->private = current;
253 wq_entry->func = autoremove_wake_function;
254 INIT_LIST_HEAD(&wq_entry->entry);
255}
256EXPORT_SYMBOL(init_wait_entry);
257
258long prepare_to_wait_event(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state)
259{
260 unsigned long flags;
261 long ret = 0;
262
263 spin_lock_irqsave(&wq_head->lock, flags);
264 if (signal_pending_state(state, current)) {
265 /*
266 * Exclusive waiter must not fail if it was selected by wakeup,
267 * it should "consume" the condition we were waiting for.
268 *
269 * The caller will recheck the condition and return success if
270 * we were already woken up, we can not miss the event because
271 * wakeup locks/unlocks the same wq_head->lock.
272 *
273 * But we need to ensure that set-condition + wakeup after that
274 * can't see us, it should wake up another exclusive waiter if
275 * we fail.
276 */
277 list_del_init(&wq_entry->entry);
278 ret = -ERESTARTSYS;
279 } else {
280 if (list_empty(&wq_entry->entry)) {
281 if (wq_entry->flags & WQ_FLAG_EXCLUSIVE)
282 __add_wait_queue_entry_tail(wq_head, wq_entry);
283 else
284 __add_wait_queue(wq_head, wq_entry);
285 }
286 set_current_state(state);
287 }
288 spin_unlock_irqrestore(&wq_head->lock, flags);
289
290 return ret;
291}
292EXPORT_SYMBOL(prepare_to_wait_event);
293
294/*
295 * Note! These two wait functions are entered with the
296 * wait-queue lock held (and interrupts off in the _irq
297 * case), so there is no race with testing the wakeup
298 * condition in the caller before they add the wait
299 * entry to the wake queue.
300 */
301int do_wait_intr(wait_queue_head_t *wq, wait_queue_entry_t *wait)
302{
303 if (likely(list_empty(&wait->entry)))
304 __add_wait_queue_entry_tail(wq, wait);
305
306 set_current_state(TASK_INTERRUPTIBLE);
307 if (signal_pending(current))
308 return -ERESTARTSYS;
309
310 spin_unlock(&wq->lock);
311 schedule();
312 spin_lock(&wq->lock);
313
314 return 0;
315}
316EXPORT_SYMBOL(do_wait_intr);
317
318int do_wait_intr_irq(wait_queue_head_t *wq, wait_queue_entry_t *wait)
319{
320 if (likely(list_empty(&wait->entry)))
321 __add_wait_queue_entry_tail(wq, wait);
322
323 set_current_state(TASK_INTERRUPTIBLE);
324 if (signal_pending(current))
325 return -ERESTARTSYS;
326
327 spin_unlock_irq(&wq->lock);
328 schedule();
329 spin_lock_irq(&wq->lock);
330
331 return 0;
332}
333EXPORT_SYMBOL(do_wait_intr_irq);
334
335/**
336 * finish_wait - clean up after waiting in a queue
337 * @wq_head: waitqueue waited on
338 * @wq_entry: wait descriptor
339 *
340 * Sets current thread back to running state and removes
341 * the wait descriptor from the given waitqueue if still
342 * queued.
343 */
344void finish_wait(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
345{
346 unsigned long flags;
347
348 __set_current_state(TASK_RUNNING);
349 /*
350 * We can check for list emptiness outside the lock
351 * IFF:
352 * - we use the "careful" check that verifies both
353 * the next and prev pointers, so that there cannot
354 * be any half-pending updates in progress on other
355 * CPU's that we haven't seen yet (and that might
356 * still change the stack area.
357 * and
358 * - all other users take the lock (ie we can only
359 * have _one_ other CPU that looks at or modifies
360 * the list).
361 */
362 if (!list_empty_careful(&wq_entry->entry)) {
363 spin_lock_irqsave(&wq_head->lock, flags);
364 list_del_init(&wq_entry->entry);
365 spin_unlock_irqrestore(&wq_head->lock, flags);
366 }
367}
368EXPORT_SYMBOL(finish_wait);
369
370int autoremove_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *key)
371{
372 int ret = default_wake_function(wq_entry, mode, sync, key);
373
374 if (ret)
375 list_del_init(&wq_entry->entry);
376
377 return ret;
378}
379EXPORT_SYMBOL(autoremove_wake_function);
380
381static inline bool is_kthread_should_stop(void)
382{
383 return (current->flags & PF_KTHREAD) && kthread_should_stop();
384}
385
386/*
387 * DEFINE_WAIT_FUNC(wait, woken_wake_func);
388 *
389 * add_wait_queue(&wq_head, &wait);
390 * for (;;) {
391 * if (condition)
392 * break;
393 *
394 * // in wait_woken() // in woken_wake_function()
395 *
396 * p->state = mode; wq_entry->flags |= WQ_FLAG_WOKEN;
397 * smp_mb(); // A try_to_wake_up():
398 * if (!(wq_entry->flags & WQ_FLAG_WOKEN)) <full barrier>
399 * schedule() if (p->state & mode)
400 * p->state = TASK_RUNNING; p->state = TASK_RUNNING;
401 * wq_entry->flags &= ~WQ_FLAG_WOKEN; ~~~~~~~~~~~~~~~~~~
402 * smp_mb(); // B condition = true;
403 * } smp_mb(); // C
404 * remove_wait_queue(&wq_head, &wait); wq_entry->flags |= WQ_FLAG_WOKEN;
405 */
406long wait_woken(struct wait_queue_entry *wq_entry, unsigned mode, long timeout)
407{
408 /*
409 * The below executes an smp_mb(), which matches with the full barrier
410 * executed by the try_to_wake_up() in woken_wake_function() such that
411 * either we see the store to wq_entry->flags in woken_wake_function()
412 * or woken_wake_function() sees our store to current->state.
413 */
414 set_current_state(mode); /* A */
415 if (!(wq_entry->flags & WQ_FLAG_WOKEN) && !is_kthread_should_stop())
416 timeout = schedule_timeout(timeout);
417 __set_current_state(TASK_RUNNING);
418
419 /*
420 * The below executes an smp_mb(), which matches with the smp_mb() (C)
421 * in woken_wake_function() such that either we see the wait condition
422 * being true or the store to wq_entry->flags in woken_wake_function()
423 * follows ours in the coherence order.
424 */
425 smp_store_mb(wq_entry->flags, wq_entry->flags & ~WQ_FLAG_WOKEN); /* B */
426
427 return timeout;
428}
429EXPORT_SYMBOL(wait_woken);
430
431int woken_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *key)
432{
433 /* Pairs with the smp_store_mb() in wait_woken(). */
434 smp_mb(); /* C */
435 wq_entry->flags |= WQ_FLAG_WOKEN;
436
437 return default_wake_function(wq_entry, mode, sync, key);
438}
439EXPORT_SYMBOL(woken_wake_function);
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Generic waiting primitives.
4 *
5 * (C) 2004 Nadia Yvette Chambers, Oracle
6 */
7
8void __init_waitqueue_head(struct wait_queue_head *wq_head, const char *name, struct lock_class_key *key)
9{
10 spin_lock_init(&wq_head->lock);
11 lockdep_set_class_and_name(&wq_head->lock, key, name);
12 INIT_LIST_HEAD(&wq_head->head);
13}
14
15EXPORT_SYMBOL(__init_waitqueue_head);
16
17void add_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
18{
19 unsigned long flags;
20
21 wq_entry->flags &= ~WQ_FLAG_EXCLUSIVE;
22 spin_lock_irqsave(&wq_head->lock, flags);
23 __add_wait_queue(wq_head, wq_entry);
24 spin_unlock_irqrestore(&wq_head->lock, flags);
25}
26EXPORT_SYMBOL(add_wait_queue);
27
28void add_wait_queue_exclusive(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
29{
30 unsigned long flags;
31
32 wq_entry->flags |= WQ_FLAG_EXCLUSIVE;
33 spin_lock_irqsave(&wq_head->lock, flags);
34 __add_wait_queue_entry_tail(wq_head, wq_entry);
35 spin_unlock_irqrestore(&wq_head->lock, flags);
36}
37EXPORT_SYMBOL(add_wait_queue_exclusive);
38
39void add_wait_queue_priority(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
40{
41 unsigned long flags;
42
43 wq_entry->flags |= WQ_FLAG_EXCLUSIVE | WQ_FLAG_PRIORITY;
44 spin_lock_irqsave(&wq_head->lock, flags);
45 __add_wait_queue(wq_head, wq_entry);
46 spin_unlock_irqrestore(&wq_head->lock, flags);
47}
48EXPORT_SYMBOL_GPL(add_wait_queue_priority);
49
50void remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
51{
52 unsigned long flags;
53
54 spin_lock_irqsave(&wq_head->lock, flags);
55 __remove_wait_queue(wq_head, wq_entry);
56 spin_unlock_irqrestore(&wq_head->lock, flags);
57}
58EXPORT_SYMBOL(remove_wait_queue);
59
60/*
61 * The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
62 * wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
63 * number) then we wake that number of exclusive tasks, and potentially all
64 * the non-exclusive tasks. Normally, exclusive tasks will be at the end of
65 * the list and any non-exclusive tasks will be woken first. A priority task
66 * may be at the head of the list, and can consume the event without any other
67 * tasks being woken.
68 *
69 * There are circumstances in which we can try to wake a task which has already
70 * started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
71 * zero in this (rare) case, and we handle it by continuing to scan the queue.
72 */
73static int __wake_up_common(struct wait_queue_head *wq_head, unsigned int mode,
74 int nr_exclusive, int wake_flags, void *key)
75{
76 wait_queue_entry_t *curr, *next;
77
78 lockdep_assert_held(&wq_head->lock);
79
80 curr = list_first_entry(&wq_head->head, wait_queue_entry_t, entry);
81
82 if (&curr->entry == &wq_head->head)
83 return nr_exclusive;
84
85 list_for_each_entry_safe_from(curr, next, &wq_head->head, entry) {
86 unsigned flags = curr->flags;
87 int ret;
88
89 ret = curr->func(curr, mode, wake_flags, key);
90 if (ret < 0)
91 break;
92 if (ret && (flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive)
93 break;
94 }
95
96 return nr_exclusive;
97}
98
99static int __wake_up_common_lock(struct wait_queue_head *wq_head, unsigned int mode,
100 int nr_exclusive, int wake_flags, void *key)
101{
102 unsigned long flags;
103 int remaining;
104
105 spin_lock_irqsave(&wq_head->lock, flags);
106 remaining = __wake_up_common(wq_head, mode, nr_exclusive, wake_flags,
107 key);
108 spin_unlock_irqrestore(&wq_head->lock, flags);
109
110 return nr_exclusive - remaining;
111}
112
113/**
114 * __wake_up - wake up threads blocked on a waitqueue.
115 * @wq_head: the waitqueue
116 * @mode: which threads
117 * @nr_exclusive: how many wake-one or wake-many threads to wake up
118 * @key: is directly passed to the wakeup function
119 *
120 * If this function wakes up a task, it executes a full memory barrier
121 * before accessing the task state. Returns the number of exclusive
122 * tasks that were awaken.
123 */
124int __wake_up(struct wait_queue_head *wq_head, unsigned int mode,
125 int nr_exclusive, void *key)
126{
127 return __wake_up_common_lock(wq_head, mode, nr_exclusive, 0, key);
128}
129EXPORT_SYMBOL(__wake_up);
130
131void __wake_up_on_current_cpu(struct wait_queue_head *wq_head, unsigned int mode, void *key)
132{
133 __wake_up_common_lock(wq_head, mode, 1, WF_CURRENT_CPU, key);
134}
135
136/*
137 * Same as __wake_up but called with the spinlock in wait_queue_head_t held.
138 */
139void __wake_up_locked(struct wait_queue_head *wq_head, unsigned int mode, int nr)
140{
141 __wake_up_common(wq_head, mode, nr, 0, NULL);
142}
143EXPORT_SYMBOL_GPL(__wake_up_locked);
144
145void __wake_up_locked_key(struct wait_queue_head *wq_head, unsigned int mode, void *key)
146{
147 __wake_up_common(wq_head, mode, 1, 0, key);
148}
149EXPORT_SYMBOL_GPL(__wake_up_locked_key);
150
151/**
152 * __wake_up_sync_key - wake up threads blocked on a waitqueue.
153 * @wq_head: the waitqueue
154 * @mode: which threads
155 * @key: opaque value to be passed to wakeup targets
156 *
157 * The sync wakeup differs that the waker knows that it will schedule
158 * away soon, so while the target thread will be woken up, it will not
159 * be migrated to another CPU - ie. the two threads are 'synchronized'
160 * with each other. This can prevent needless bouncing between CPUs.
161 *
162 * On UP it can prevent extra preemption.
163 *
164 * If this function wakes up a task, it executes a full memory barrier before
165 * accessing the task state.
166 */
167void __wake_up_sync_key(struct wait_queue_head *wq_head, unsigned int mode,
168 void *key)
169{
170 if (unlikely(!wq_head))
171 return;
172
173 __wake_up_common_lock(wq_head, mode, 1, WF_SYNC, key);
174}
175EXPORT_SYMBOL_GPL(__wake_up_sync_key);
176
177/**
178 * __wake_up_locked_sync_key - wake up a thread blocked on a locked waitqueue.
179 * @wq_head: the waitqueue
180 * @mode: which threads
181 * @key: opaque value to be passed to wakeup targets
182 *
183 * The sync wakeup differs in that the waker knows that it will schedule
184 * away soon, so while the target thread will be woken up, it will not
185 * be migrated to another CPU - ie. the two threads are 'synchronized'
186 * with each other. This can prevent needless bouncing between CPUs.
187 *
188 * On UP it can prevent extra preemption.
189 *
190 * If this function wakes up a task, it executes a full memory barrier before
191 * accessing the task state.
192 */
193void __wake_up_locked_sync_key(struct wait_queue_head *wq_head,
194 unsigned int mode, void *key)
195{
196 __wake_up_common(wq_head, mode, 1, WF_SYNC, key);
197}
198EXPORT_SYMBOL_GPL(__wake_up_locked_sync_key);
199
200/*
201 * __wake_up_sync - see __wake_up_sync_key()
202 */
203void __wake_up_sync(struct wait_queue_head *wq_head, unsigned int mode)
204{
205 __wake_up_sync_key(wq_head, mode, NULL);
206}
207EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */
208
209void __wake_up_pollfree(struct wait_queue_head *wq_head)
210{
211 __wake_up(wq_head, TASK_NORMAL, 0, poll_to_key(EPOLLHUP | POLLFREE));
212 /* POLLFREE must have cleared the queue. */
213 WARN_ON_ONCE(waitqueue_active(wq_head));
214}
215
216/*
217 * Note: we use "set_current_state()" _after_ the wait-queue add,
218 * because we need a memory barrier there on SMP, so that any
219 * wake-function that tests for the wait-queue being active
220 * will be guaranteed to see waitqueue addition _or_ subsequent
221 * tests in this thread will see the wakeup having taken place.
222 *
223 * The spin_unlock() itself is semi-permeable and only protects
224 * one way (it only protects stuff inside the critical region and
225 * stops them from bleeding out - it would still allow subsequent
226 * loads to move into the critical region).
227 */
228void
229prepare_to_wait(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state)
230{
231 unsigned long flags;
232
233 wq_entry->flags &= ~WQ_FLAG_EXCLUSIVE;
234 spin_lock_irqsave(&wq_head->lock, flags);
235 if (list_empty(&wq_entry->entry))
236 __add_wait_queue(wq_head, wq_entry);
237 set_current_state(state);
238 spin_unlock_irqrestore(&wq_head->lock, flags);
239}
240EXPORT_SYMBOL(prepare_to_wait);
241
242/* Returns true if we are the first waiter in the queue, false otherwise. */
243bool
244prepare_to_wait_exclusive(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state)
245{
246 unsigned long flags;
247 bool was_empty = false;
248
249 wq_entry->flags |= WQ_FLAG_EXCLUSIVE;
250 spin_lock_irqsave(&wq_head->lock, flags);
251 if (list_empty(&wq_entry->entry)) {
252 was_empty = list_empty(&wq_head->head);
253 __add_wait_queue_entry_tail(wq_head, wq_entry);
254 }
255 set_current_state(state);
256 spin_unlock_irqrestore(&wq_head->lock, flags);
257 return was_empty;
258}
259EXPORT_SYMBOL(prepare_to_wait_exclusive);
260
261void init_wait_entry(struct wait_queue_entry *wq_entry, int flags)
262{
263 wq_entry->flags = flags;
264 wq_entry->private = current;
265 wq_entry->func = autoremove_wake_function;
266 INIT_LIST_HEAD(&wq_entry->entry);
267}
268EXPORT_SYMBOL(init_wait_entry);
269
270long prepare_to_wait_event(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry, int state)
271{
272 unsigned long flags;
273 long ret = 0;
274
275 spin_lock_irqsave(&wq_head->lock, flags);
276 if (signal_pending_state(state, current)) {
277 /*
278 * Exclusive waiter must not fail if it was selected by wakeup,
279 * it should "consume" the condition we were waiting for.
280 *
281 * The caller will recheck the condition and return success if
282 * we were already woken up, we can not miss the event because
283 * wakeup locks/unlocks the same wq_head->lock.
284 *
285 * But we need to ensure that set-condition + wakeup after that
286 * can't see us, it should wake up another exclusive waiter if
287 * we fail.
288 */
289 list_del_init(&wq_entry->entry);
290 ret = -ERESTARTSYS;
291 } else {
292 if (list_empty(&wq_entry->entry)) {
293 if (wq_entry->flags & WQ_FLAG_EXCLUSIVE)
294 __add_wait_queue_entry_tail(wq_head, wq_entry);
295 else
296 __add_wait_queue(wq_head, wq_entry);
297 }
298 set_current_state(state);
299 }
300 spin_unlock_irqrestore(&wq_head->lock, flags);
301
302 return ret;
303}
304EXPORT_SYMBOL(prepare_to_wait_event);
305
306/*
307 * Note! These two wait functions are entered with the
308 * wait-queue lock held (and interrupts off in the _irq
309 * case), so there is no race with testing the wakeup
310 * condition in the caller before they add the wait
311 * entry to the wake queue.
312 */
313int do_wait_intr(wait_queue_head_t *wq, wait_queue_entry_t *wait)
314{
315 if (likely(list_empty(&wait->entry)))
316 __add_wait_queue_entry_tail(wq, wait);
317
318 set_current_state(TASK_INTERRUPTIBLE);
319 if (signal_pending(current))
320 return -ERESTARTSYS;
321
322 spin_unlock(&wq->lock);
323 schedule();
324 spin_lock(&wq->lock);
325
326 return 0;
327}
328EXPORT_SYMBOL(do_wait_intr);
329
330int do_wait_intr_irq(wait_queue_head_t *wq, wait_queue_entry_t *wait)
331{
332 if (likely(list_empty(&wait->entry)))
333 __add_wait_queue_entry_tail(wq, wait);
334
335 set_current_state(TASK_INTERRUPTIBLE);
336 if (signal_pending(current))
337 return -ERESTARTSYS;
338
339 spin_unlock_irq(&wq->lock);
340 schedule();
341 spin_lock_irq(&wq->lock);
342
343 return 0;
344}
345EXPORT_SYMBOL(do_wait_intr_irq);
346
347/**
348 * finish_wait - clean up after waiting in a queue
349 * @wq_head: waitqueue waited on
350 * @wq_entry: wait descriptor
351 *
352 * Sets current thread back to running state and removes
353 * the wait descriptor from the given waitqueue if still
354 * queued.
355 */
356void finish_wait(struct wait_queue_head *wq_head, struct wait_queue_entry *wq_entry)
357{
358 unsigned long flags;
359
360 __set_current_state(TASK_RUNNING);
361 /*
362 * We can check for list emptiness outside the lock
363 * IFF:
364 * - we use the "careful" check that verifies both
365 * the next and prev pointers, so that there cannot
366 * be any half-pending updates in progress on other
367 * CPU's that we haven't seen yet (and that might
368 * still change the stack area.
369 * and
370 * - all other users take the lock (ie we can only
371 * have _one_ other CPU that looks at or modifies
372 * the list).
373 */
374 if (!list_empty_careful(&wq_entry->entry)) {
375 spin_lock_irqsave(&wq_head->lock, flags);
376 list_del_init(&wq_entry->entry);
377 spin_unlock_irqrestore(&wq_head->lock, flags);
378 }
379}
380EXPORT_SYMBOL(finish_wait);
381
382int autoremove_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *key)
383{
384 int ret = default_wake_function(wq_entry, mode, sync, key);
385
386 if (ret)
387 list_del_init_careful(&wq_entry->entry);
388
389 return ret;
390}
391EXPORT_SYMBOL(autoremove_wake_function);
392
393/*
394 * DEFINE_WAIT_FUNC(wait, woken_wake_func);
395 *
396 * add_wait_queue(&wq_head, &wait);
397 * for (;;) {
398 * if (condition)
399 * break;
400 *
401 * // in wait_woken() // in woken_wake_function()
402 *
403 * p->state = mode; wq_entry->flags |= WQ_FLAG_WOKEN;
404 * smp_mb(); // A try_to_wake_up():
405 * if (!(wq_entry->flags & WQ_FLAG_WOKEN)) <full barrier>
406 * schedule() if (p->state & mode)
407 * p->state = TASK_RUNNING; p->state = TASK_RUNNING;
408 * wq_entry->flags &= ~WQ_FLAG_WOKEN; ~~~~~~~~~~~~~~~~~~
409 * smp_mb(); // B condition = true;
410 * } smp_mb(); // C
411 * remove_wait_queue(&wq_head, &wait); wq_entry->flags |= WQ_FLAG_WOKEN;
412 */
413long wait_woken(struct wait_queue_entry *wq_entry, unsigned mode, long timeout)
414{
415 /*
416 * The below executes an smp_mb(), which matches with the full barrier
417 * executed by the try_to_wake_up() in woken_wake_function() such that
418 * either we see the store to wq_entry->flags in woken_wake_function()
419 * or woken_wake_function() sees our store to current->state.
420 */
421 set_current_state(mode); /* A */
422 if (!(wq_entry->flags & WQ_FLAG_WOKEN) && !kthread_should_stop_or_park())
423 timeout = schedule_timeout(timeout);
424 __set_current_state(TASK_RUNNING);
425
426 /*
427 * The below executes an smp_mb(), which matches with the smp_mb() (C)
428 * in woken_wake_function() such that either we see the wait condition
429 * being true or the store to wq_entry->flags in woken_wake_function()
430 * follows ours in the coherence order.
431 */
432 smp_store_mb(wq_entry->flags, wq_entry->flags & ~WQ_FLAG_WOKEN); /* B */
433
434 return timeout;
435}
436EXPORT_SYMBOL(wait_woken);
437
438int woken_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *key)
439{
440 /* Pairs with the smp_store_mb() in wait_woken(). */
441 smp_mb(); /* C */
442 wq_entry->flags |= WQ_FLAG_WOKEN;
443
444 return default_wake_function(wq_entry, mode, sync, key);
445}
446EXPORT_SYMBOL(woken_wake_function);