Branch data Line data Source code
1 : : /*
2 : : * Generic waiting primitives.
3 : : *
4 : : * (C) 2004 Nadia Yvette Chambers, Oracle
5 : : */
6 : : #include <linux/init.h>
7 : : #include <linux/export.h>
8 : : #include <linux/sched.h>
9 : : #include <linux/mm.h>
10 : : #include <linux/wait.h>
11 : : #include <linux/hash.h>
12 : :
13 : 0 : void __init_waitqueue_head(wait_queue_head_t *q, const char *name, struct lock_class_key *key)
14 : : {
15 : 8549699 : spin_lock_init(&q->lock);
16 : : lockdep_set_class_and_name(&q->lock, key, name);
17 : 8549699 : INIT_LIST_HEAD(&q->task_list);
18 : 8549699 : }
19 : :
20 : : EXPORT_SYMBOL(__init_waitqueue_head);
21 : :
22 : 0 : void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait)
23 : : {
24 : : unsigned long flags;
25 : :
26 : 1489682 : wait->flags &= ~WQ_FLAG_EXCLUSIVE;
27 : 1489682 : spin_lock_irqsave(&q->lock, flags);
28 : : __add_wait_queue(q, wait);
29 : : spin_unlock_irqrestore(&q->lock, flags);
30 : 1489722 : }
31 : : EXPORT_SYMBOL(add_wait_queue);
32 : :
33 : 0 : void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait)
34 : : {
35 : : unsigned long flags;
36 : :
37 : 0 : wait->flags |= WQ_FLAG_EXCLUSIVE;
38 : 0 : spin_lock_irqsave(&q->lock, flags);
39 : : __add_wait_queue_tail(q, wait);
40 : : spin_unlock_irqrestore(&q->lock, flags);
41 : 0 : }
42 : : EXPORT_SYMBOL(add_wait_queue_exclusive);
43 : :
44 : 0 : void remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait)
45 : : {
46 : : unsigned long flags;
47 : :
48 : 1489636 : spin_lock_irqsave(&q->lock, flags);
49 : : __remove_wait_queue(q, wait);
50 : : spin_unlock_irqrestore(&q->lock, flags);
51 : 1489727 : }
52 : : EXPORT_SYMBOL(remove_wait_queue);
53 : :
54 : :
55 : : /*
56 : : * The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
57 : : * wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
58 : : * number) then we wake all the non-exclusive tasks and one exclusive task.
59 : : *
60 : : * There are circumstances in which we can try to wake a task which has already
61 : : * started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
62 : : * zero in this (rare) case, and we handle it by continuing to scan the queue.
63 : : */
64 : 0 : static void __wake_up_common(wait_queue_head_t *q, unsigned int mode,
65 : : int nr_exclusive, int wake_flags, void *key)
66 : : {
67 : : wait_queue_t *curr, *next;
68 : :
69 [ + + ]: 14847403 : list_for_each_entry_safe(curr, next, &q->task_list, task_list) {
70 : 3243393 : unsigned flags = curr->flags;
71 : :
72 [ + + ][ + + ]: 3243393 : if (curr->func(curr, mode, wake_flags, key) &&
73 [ + + ]: 1630173 : (flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive)
74 : : break;
75 : : }
76 : 440 : }
77 : :
78 : : /**
79 : : * __wake_up - wake up threads blocked on a waitqueue.
80 : : * @q: the waitqueue
81 : : * @mode: which threads
82 : : * @nr_exclusive: how many wake-one or wake-many threads to wake up
83 : : * @key: is directly passed to the wakeup function
84 : : *
85 : : * It may be assumed that this function implies a write memory barrier before
86 : : * changing the task state if and only if any tasks are woken up.
87 : : */
88 : 0 : void __wake_up(wait_queue_head_t *q, unsigned int mode,
89 : : int nr_exclusive, void *key)
90 : : {
91 : : unsigned long flags;
92 : :
93 : 9719314 : spin_lock_irqsave(&q->lock, flags);
94 : 9714744 : __wake_up_common(q, mode, nr_exclusive, 0, key);
95 : : spin_unlock_irqrestore(&q->lock, flags);
96 : 9726217 : }
97 : : EXPORT_SYMBOL(__wake_up);
98 : :
99 : : /*
100 : : * Same as __wake_up but called with the spinlock in wait_queue_head_t held.
101 : : */
102 : 0 : void __wake_up_locked(wait_queue_head_t *q, unsigned int mode, int nr)
103 : : {
104 : 1650907 : __wake_up_common(q, mode, nr, 0, NULL);
105 : 1650911 : }
106 : : EXPORT_SYMBOL_GPL(__wake_up_locked);
107 : :
108 : 0 : void __wake_up_locked_key(wait_queue_head_t *q, unsigned int mode, void *key)
109 : : {
110 : 4 : __wake_up_common(q, mode, 1, 0, key);
111 : 4 : }
112 : : EXPORT_SYMBOL_GPL(__wake_up_locked_key);
113 : :
114 : : /**
115 : : * __wake_up_sync_key - wake up threads blocked on a waitqueue.
116 : : * @q: the waitqueue
117 : : * @mode: which threads
118 : : * @nr_exclusive: how many wake-one or wake-many threads to wake up
119 : : * @key: opaque value to be passed to wakeup targets
120 : : *
121 : : * The sync wakeup differs that the waker knows that it will schedule
122 : : * away soon, so while the target thread will be woken up, it will not
123 : : * be migrated to another CPU - ie. the two threads are 'synchronized'
124 : : * with each other. This can prevent needless bouncing between CPUs.
125 : : *
126 : : * On UP it can prevent extra preemption.
127 : : *
128 : : * It may be assumed that this function implies a write memory barrier before
129 : : * changing the task state if and only if any tasks are woken up.
130 : : */
131 : 0 : void __wake_up_sync_key(wait_queue_head_t *q, unsigned int mode,
132 : : int nr_exclusive, void *key)
133 : : {
134 : : unsigned long flags;
135 : : int wake_flags = 1; /* XXX WF_SYNC */
136 : :
137 [ + ]: 1884252 : if (unlikely(!q))
138 : 1884655 : return;
139 : :
140 [ - + ]: 1884268 : if (unlikely(nr_exclusive != 1))
141 : : wake_flags = 0;
142 : :
143 : 1884268 : spin_lock_irqsave(&q->lock, flags);
144 : 1884175 : __wake_up_common(q, mode, nr_exclusive, wake_flags, key);
145 : : spin_unlock_irqrestore(&q->lock, flags);
146 : : }
147 : : EXPORT_SYMBOL_GPL(__wake_up_sync_key);
148 : :
149 : : /*
150 : : * __wake_up_sync - see __wake_up_sync_key()
151 : : */
152 : 0 : void __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
153 : : {
154 : 0 : __wake_up_sync_key(q, mode, nr_exclusive, NULL);
155 : 0 : }
156 : : EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */
157 : :
158 : : /*
159 : : * Note: we use "set_current_state()" _after_ the wait-queue add,
160 : : * because we need a memory barrier there on SMP, so that any
161 : : * wake-function that tests for the wait-queue being active
162 : : * will be guaranteed to see waitqueue addition _or_ subsequent
163 : : * tests in this thread will see the wakeup having taken place.
164 : : *
165 : : * The spin_unlock() itself is semi-permeable and only protects
166 : : * one way (it only protects stuff inside the critical region and
167 : : * stops them from bleeding out - it would still allow subsequent
168 : : * loads to move into the critical region).
169 : : */
170 : : void
171 : 0 : prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state)
172 : : {
173 : : unsigned long flags;
174 : :
175 : 435454 : wait->flags &= ~WQ_FLAG_EXCLUSIVE;
176 : 435454 : spin_lock_irqsave(&q->lock, flags);
177 [ + + ]: 437076 : if (list_empty(&wait->task_list))
178 : : __add_wait_queue(q, wait);
179 : 437076 : set_current_state(state);
180 : : spin_unlock_irqrestore(&q->lock, flags);
181 : 437827 : }
182 : : EXPORT_SYMBOL(prepare_to_wait);
183 : :
184 : : void
185 : 0 : prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state)
186 : : {
187 : : unsigned long flags;
188 : :
189 : 65245 : wait->flags |= WQ_FLAG_EXCLUSIVE;
190 : 65245 : spin_lock_irqsave(&q->lock, flags);
191 [ + + ]: 65258 : if (list_empty(&wait->task_list))
192 : : __add_wait_queue_tail(q, wait);
193 : 65258 : set_current_state(state);
194 : : spin_unlock_irqrestore(&q->lock, flags);
195 : 65259 : }
196 : : EXPORT_SYMBOL(prepare_to_wait_exclusive);
197 : :
198 : 0 : long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state)
199 : : {
200 : : unsigned long flags;
201 : :
202 [ + ]: 1167666 : if (signal_pending_state(state, current))
203 : : return -ERESTARTSYS;
204 : :
205 : 1167751 : wait->private = current;
206 : 1167751 : wait->func = autoremove_wake_function;
207 : :
208 : 1167751 : spin_lock_irqsave(&q->lock, flags);
209 [ + + ]: 1167765 : if (list_empty(&wait->task_list)) {
210 [ - + ]: 744849 : if (wait->flags & WQ_FLAG_EXCLUSIVE)
211 : : __add_wait_queue_tail(q, wait);
212 : : else
213 : : __add_wait_queue(q, wait);
214 : : }
215 : 1167765 : set_current_state(state);
216 : : spin_unlock_irqrestore(&q->lock, flags);
217 : :
218 : 1167767 : return 0;
219 : : }
220 : : EXPORT_SYMBOL(prepare_to_wait_event);
221 : :
222 : : /**
223 : : * finish_wait - clean up after waiting in a queue
224 : : * @q: waitqueue waited on
225 : : * @wait: wait descriptor
226 : : *
227 : : * Sets current thread back to running state and removes
228 : : * the wait descriptor from the given waitqueue if still
229 : : * queued.
230 : : */
231 : 0 : void finish_wait(wait_queue_head_t *q, wait_queue_t *wait)
232 : : {
233 : : unsigned long flags;
234 : :
235 : 985500 : __set_current_state(TASK_RUNNING);
236 : : /*
237 : : * We can check for list emptiness outside the lock
238 : : * IFF:
239 : : * - we use the "careful" check that verifies both
240 : : * the next and prev pointers, so that there cannot
241 : : * be any half-pending updates in progress on other
242 : : * CPU's that we haven't seen yet (and that might
243 : : * still change the stack area.
244 : : * and
245 : : * - all other users take the lock (ie we can only
246 : : * have _one_ other CPU that looks at or modifies
247 : : * the list).
248 : : */
249 [ + + ]: 985500 : if (!list_empty_careful(&wait->task_list)) {
250 : 715035 : spin_lock_irqsave(&q->lock, flags);
251 : : list_del_init(&wait->task_list);
252 : : spin_unlock_irqrestore(&q->lock, flags);
253 : : }
254 : 10 : }
255 : : EXPORT_SYMBOL(finish_wait);
256 : :
257 : : /**
258 : : * abort_exclusive_wait - abort exclusive waiting in a queue
259 : : * @q: waitqueue waited on
260 : : * @wait: wait descriptor
261 : : * @mode: runstate of the waiter to be woken
262 : : * @key: key to identify a wait bit queue or %NULL
263 : : *
264 : : * Sets current thread back to running state and removes
265 : : * the wait descriptor from the given waitqueue if still
266 : : * queued.
267 : : *
268 : : * Wakes up the next waiter if the caller is concurrently
269 : : * woken up through the queue.
270 : : *
271 : : * This prevents waiter starvation where an exclusive waiter
272 : : * aborts and is woken up concurrently and no one wakes up
273 : : * the next waiter.
274 : : */
275 : 0 : void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait,
276 : : unsigned int mode, void *key)
277 : : {
278 : : unsigned long flags;
279 : :
280 : 0 : __set_current_state(TASK_RUNNING);
281 : 0 : spin_lock_irqsave(&q->lock, flags);
282 [ # # ]: 0 : if (!list_empty(&wait->task_list))
283 : : list_del_init(&wait->task_list);
284 [ # # ]: 0 : else if (waitqueue_active(q))
285 : : __wake_up_locked_key(q, mode, key);
286 : : spin_unlock_irqrestore(&q->lock, flags);
287 : 0 : }
288 : : EXPORT_SYMBOL(abort_exclusive_wait);
289 : :
290 : 0 : int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
291 : : {
292 : 530604 : int ret = default_wake_function(wait, mode, sync, key);
293 : :
294 [ + + ]: 530728 : if (ret)
295 : 507992 : list_del_init(&wait->task_list);
296 : 124 : return ret;
297 : : }
298 : : EXPORT_SYMBOL(autoremove_wake_function);
299 : :
300 : 0 : int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
301 : : {
302 : : struct wait_bit_key *key = arg;
303 : : struct wait_bit_queue *wait_bit
304 : : = container_of(wait, struct wait_bit_queue, wait);
305 : :
306 [ + + ][ + + ]: 235573 : if (wait_bit->key.flags != key->flags ||
307 [ + + ]: 230381 : wait_bit->key.bit_nr != key->bit_nr ||
308 : : test_bit(key->bit_nr, key->flags))
309 : : return 0;
310 : : else
311 : 227429 : return autoremove_wake_function(wait, mode, sync, key);
312 : : }
313 : : EXPORT_SYMBOL(wake_bit_function);
314 : :
315 : : /*
316 : : * To allow interruptible waiting and asynchronous (i.e. nonblocking)
317 : : * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are
318 : : * permitted return codes. Nonzero return codes halt waiting and return.
319 : : */
320 : : int __sched
321 : 176313 : __wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q,
322 : : int (*action)(void *), unsigned mode)
323 : : {
324 : : int ret = 0;
325 : :
326 : : do {
327 : 176839 : prepare_to_wait(wq, &q->wait, mode);
328 [ + + ]: 178269 : if (test_bit(q->key.bit_nr, q->key.flags))
329 : 175649 : ret = (*action)(q->key.flags);
330 [ + + ][ + - ]: 177910 : } while (test_bit(q->key.bit_nr, q->key.flags) && !ret);
331 : 177384 : finish_wait(wq, &q->wait);
332 : 177430 : return ret;
333 : : }
334 : : EXPORT_SYMBOL(__wait_on_bit);
335 : :
336 : 0 : int __sched out_of_line_wait_on_bit(void *word, int bit,
337 : : int (*action)(void *), unsigned mode)
338 : : {
339 : 40784 : wait_queue_head_t *wq = bit_waitqueue(word, bit);
340 : 81570 : DEFINE_WAIT_BIT(wait, word, bit);
341 : :
342 : 40785 : return __wait_on_bit(wq, &wait, action, mode);
343 : : }
344 : : EXPORT_SYMBOL(out_of_line_wait_on_bit);
345 : :
346 : : int __sched
347 : 63892 : __wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,
348 : : int (*action)(void *), unsigned mode)
349 : : {
350 : : do {
351 : : int ret;
352 : :
353 : 64004 : prepare_to_wait_exclusive(wq, &q->wait, mode);
354 [ + + ]: 64021 : if (!test_bit(q->key.bit_nr, q->key.flags))
355 : 14030 : continue;
356 : 49991 : ret = action(q->key.flags);
357 [ + - ]: 49988 : if (!ret)
358 : 49988 : continue;
359 : 0 : abort_exclusive_wait(wq, &q->wait, mode, &q->key);
360 : 0 : return ret;
361 [ + + ]: 64018 : } while (test_and_set_bit(q->key.bit_nr, q->key.flags));
362 : 63907 : finish_wait(wq, &q->wait);
363 : 63908 : return 0;
364 : : }
365 : : EXPORT_SYMBOL(__wait_on_bit_lock);
366 : :
367 : 0 : int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
368 : : int (*action)(void *), unsigned mode)
369 : : {
370 : 12708 : wait_queue_head_t *wq = bit_waitqueue(word, bit);
371 : 25396 : DEFINE_WAIT_BIT(wait, word, bit);
372 : :
373 : 12698 : return __wait_on_bit_lock(wq, &wait, action, mode);
374 : : }
375 : : EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
376 : :
377 : 0 : void __wake_up_bit(wait_queue_head_t *wq, void *word, int bit)
378 : : {
379 : 80658556 : struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
380 [ + + ]: 80658556 : if (waitqueue_active(wq))
381 : 193699 : __wake_up(wq, TASK_NORMAL, 1, &key);
382 : 0 : }
383 : : EXPORT_SYMBOL(__wake_up_bit);
384 : :
385 : : /**
386 : : * wake_up_bit - wake up a waiter on a bit
387 : : * @word: the word being waited on, a kernel virtual address
388 : : * @bit: the bit of the word being waited on
389 : : *
390 : : * There is a standard hashed waitqueue table for generic use. This
391 : : * is the part of the hashtable's accessor API that wakes up waiters
392 : : * on a bit. For instance, if one were to have waiters on a bitflag,
393 : : * one would call wake_up_bit() after clearing the bit.
394 : : *
395 : : * In order for this to function properly, as it uses waitqueue_active()
396 : : * internally, some kind of memory barrier must be done prior to calling
397 : : * this. Typically, this will be smp_mb__after_clear_bit(), but in some
398 : : * cases where bitflags are manipulated non-atomically under a lock, one
399 : : * may need to use a less regular barrier, such fs/inode.c's smp_mb(),
400 : : * because spin_unlock() does not guarantee a memory barrier.
401 : : */
402 : 0 : void wake_up_bit(void *word, int bit)
403 : : {
404 : 16533223 : __wake_up_bit(bit_waitqueue(word, bit), word, bit);
405 : 16557760 : }
406 : : EXPORT_SYMBOL(wake_up_bit);
407 : :
408 : 0 : wait_queue_head_t *bit_waitqueue(void *word, int bit)
409 : : {
410 : : const int shift = BITS_PER_LONG == 32 ? 5 : 6;
411 : 54731295 : const struct zone *zone = page_zone(virt_to_page(word));
412 : 18243765 : unsigned long val = (unsigned long)word << shift | bit;
413 : :
414 : 36487530 : return &zone->wait_table[hash_long(val, zone->wait_table_bits)];
415 : : }
416 : : EXPORT_SYMBOL(bit_waitqueue);
417 : :
418 : : /*
419 : : * Manipulate the atomic_t address to produce a better bit waitqueue table hash
420 : : * index (we're keying off bit -1, but that would produce a horrible hash
421 : : * value).
422 : : */
423 : : static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p)
424 : : {
425 : : if (BITS_PER_LONG == 64) {
426 : : unsigned long q = (unsigned long)p;
427 : : return bit_waitqueue((void *)(q & ~1), q & 1);
428 : : }
429 : 0 : return bit_waitqueue(p, 0);
430 : : }
431 : :
432 : 0 : static int wake_atomic_t_function(wait_queue_t *wait, unsigned mode, int sync,
433 : : void *arg)
434 : : {
435 : : struct wait_bit_key *key = arg;
436 : : struct wait_bit_queue *wait_bit
437 : : = container_of(wait, struct wait_bit_queue, wait);
438 : 0 : atomic_t *val = key->flags;
439 : :
440 [ # # ][ # # ]: 0 : if (wait_bit->key.flags != key->flags ||
441 [ # # ]: 0 : wait_bit->key.bit_nr != key->bit_nr ||
442 : 0 : atomic_read(val) != 0)
443 : : return 0;
444 : 0 : return autoremove_wake_function(wait, mode, sync, key);
445 : : }
446 : :
447 : : /*
448 : : * To allow interruptible waiting and asynchronous (i.e. nonblocking) waiting,
449 : : * the actions of __wait_on_atomic_t() are permitted return codes. Nonzero
450 : : * return codes halt waiting and return.
451 : : */
452 : : static __sched
453 : 0 : int __wait_on_atomic_t(wait_queue_head_t *wq, struct wait_bit_queue *q,
454 : : int (*action)(atomic_t *), unsigned mode)
455 : : {
456 : : atomic_t *val;
457 : : int ret = 0;
458 : :
459 : : do {
460 : 0 : prepare_to_wait(wq, &q->wait, mode);
461 : 0 : val = q->key.flags;
462 [ # # ]: 0 : if (atomic_read(val) == 0)
463 : : break;
464 : 0 : ret = (*action)(val);
465 [ # # ][ # # ]: 0 : } while (!ret && atomic_read(val) != 0);
466 : 0 : finish_wait(wq, &q->wait);
467 : 0 : return ret;
468 : : }
469 : :
470 : : #define DEFINE_WAIT_ATOMIC_T(name, p) \
471 : : struct wait_bit_queue name = { \
472 : : .key = __WAIT_ATOMIC_T_KEY_INITIALIZER(p), \
473 : : .wait = { \
474 : : .private = current, \
475 : : .func = wake_atomic_t_function, \
476 : : .task_list = \
477 : : LIST_HEAD_INIT((name).wait.task_list), \
478 : : }, \
479 : : }
480 : :
481 : 0 : __sched int out_of_line_wait_on_atomic_t(atomic_t *p, int (*action)(atomic_t *),
482 : : unsigned mode)
483 : : {
484 : : wait_queue_head_t *wq = atomic_t_waitqueue(p);
485 : 0 : DEFINE_WAIT_ATOMIC_T(wait, p);
486 : :
487 : 0 : return __wait_on_atomic_t(wq, &wait, action, mode);
488 : : }
489 : : EXPORT_SYMBOL(out_of_line_wait_on_atomic_t);
490 : :
491 : : /**
492 : : * wake_up_atomic_t - Wake up a waiter on a atomic_t
493 : : * @p: The atomic_t being waited on, a kernel virtual address
494 : : *
495 : : * Wake up anyone waiting for the atomic_t to go to zero.
496 : : *
497 : : * Abuse the bit-waker function and its waitqueue hash table set (the atomic_t
498 : : * check is done by the waiter's wake function, not the by the waker itself).
499 : : */
500 : 0 : void wake_up_atomic_t(atomic_t *p)
501 : : {
502 : 0 : __wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR);
503 : 0 : }
504 : : EXPORT_SYMBOL(wake_up_atomic_t);
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