]>
Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
2 | * Generic waiting primitives. | |
3 | * | |
6d49e352 | 4 | * (C) 2004 Nadia Yvette Chambers, Oracle |
1da177e4 | 5 | */ |
1da177e4 | 6 | #include <linux/init.h> |
9984de1a | 7 | #include <linux/export.h> |
1da177e4 LT |
8 | #include <linux/sched.h> |
9 | #include <linux/mm.h> | |
10 | #include <linux/wait.h> | |
11 | #include <linux/hash.h> | |
12 | ||
f07fdec5 | 13 | void __init_waitqueue_head(wait_queue_head_t *q, const char *name, struct lock_class_key *key) |
21d71f51 IM |
14 | { |
15 | spin_lock_init(&q->lock); | |
f07fdec5 | 16 | lockdep_set_class_and_name(&q->lock, key, name); |
21d71f51 IM |
17 | INIT_LIST_HEAD(&q->task_list); |
18 | } | |
eb4542b9 | 19 | |
2fc39111 | 20 | EXPORT_SYMBOL(__init_waitqueue_head); |
eb4542b9 | 21 | |
7ad5b3a5 | 22 | void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait) |
1da177e4 LT |
23 | { |
24 | unsigned long flags; | |
25 | ||
26 | wait->flags &= ~WQ_FLAG_EXCLUSIVE; | |
27 | spin_lock_irqsave(&q->lock, flags); | |
28 | __add_wait_queue(q, wait); | |
29 | spin_unlock_irqrestore(&q->lock, flags); | |
30 | } | |
31 | EXPORT_SYMBOL(add_wait_queue); | |
32 | ||
7ad5b3a5 | 33 | void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait) |
1da177e4 LT |
34 | { |
35 | unsigned long flags; | |
36 | ||
37 | wait->flags |= WQ_FLAG_EXCLUSIVE; | |
38 | spin_lock_irqsave(&q->lock, flags); | |
39 | __add_wait_queue_tail(q, wait); | |
40 | spin_unlock_irqrestore(&q->lock, flags); | |
41 | } | |
42 | EXPORT_SYMBOL(add_wait_queue_exclusive); | |
43 | ||
7ad5b3a5 | 44 | void remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait) |
1da177e4 LT |
45 | { |
46 | unsigned long flags; | |
47 | ||
48 | spin_lock_irqsave(&q->lock, flags); | |
49 | __remove_wait_queue(q, wait); | |
50 | spin_unlock_irqrestore(&q->lock, flags); | |
51 | } | |
52 | EXPORT_SYMBOL(remove_wait_queue); | |
53 | ||
54 | ||
b4145872 PZ |
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 | 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 | list_for_each_entry_safe(curr, next, &q->task_list, task_list) { | |
70 | unsigned flags = curr->flags; | |
71 | ||
72 | if (curr->func(curr, mode, wake_flags, key) && | |
73 | (flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive) | |
74 | break; | |
75 | } | |
76 | } | |
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 | void __wake_up(wait_queue_head_t *q, unsigned int mode, | |
89 | int nr_exclusive, void *key) | |
90 | { | |
91 | unsigned long flags; | |
92 | ||
93 | spin_lock_irqsave(&q->lock, flags); | |
94 | __wake_up_common(q, mode, nr_exclusive, 0, key); | |
95 | spin_unlock_irqrestore(&q->lock, flags); | |
96 | } | |
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 | void __wake_up_locked(wait_queue_head_t *q, unsigned int mode, int nr) | |
103 | { | |
104 | __wake_up_common(q, mode, nr, 0, NULL); | |
105 | } | |
106 | EXPORT_SYMBOL_GPL(__wake_up_locked); | |
107 | ||
108 | void __wake_up_locked_key(wait_queue_head_t *q, unsigned int mode, void *key) | |
109 | { | |
110 | __wake_up_common(q, mode, 1, 0, key); | |
111 | } | |
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 | 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 | if (unlikely(!q)) | |
138 | return; | |
139 | ||
140 | if (unlikely(nr_exclusive != 1)) | |
141 | wake_flags = 0; | |
142 | ||
143 | spin_lock_irqsave(&q->lock, flags); | |
144 | __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 | void __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive) | |
153 | { | |
154 | __wake_up_sync_key(q, mode, nr_exclusive, NULL); | |
155 | } | |
156 | EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */ | |
157 | ||
1da177e4 LT |
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 | |
59c51591 | 168 | * loads to move into the critical region). |
1da177e4 | 169 | */ |
7ad5b3a5 | 170 | void |
1da177e4 LT |
171 | prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state) |
172 | { | |
173 | unsigned long flags; | |
174 | ||
175 | wait->flags &= ~WQ_FLAG_EXCLUSIVE; | |
176 | spin_lock_irqsave(&q->lock, flags); | |
177 | if (list_empty(&wait->task_list)) | |
178 | __add_wait_queue(q, wait); | |
a25d644f | 179 | set_current_state(state); |
1da177e4 LT |
180 | spin_unlock_irqrestore(&q->lock, flags); |
181 | } | |
182 | EXPORT_SYMBOL(prepare_to_wait); | |
183 | ||
7ad5b3a5 | 184 | void |
1da177e4 LT |
185 | prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state) |
186 | { | |
187 | unsigned long flags; | |
188 | ||
189 | wait->flags |= WQ_FLAG_EXCLUSIVE; | |
190 | spin_lock_irqsave(&q->lock, flags); | |
191 | if (list_empty(&wait->task_list)) | |
192 | __add_wait_queue_tail(q, wait); | |
a25d644f | 193 | set_current_state(state); |
1da177e4 LT |
194 | spin_unlock_irqrestore(&q->lock, flags); |
195 | } | |
196 | EXPORT_SYMBOL(prepare_to_wait_exclusive); | |
197 | ||
c2d81644 ON |
198 | long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state) |
199 | { | |
200 | unsigned long flags; | |
201 | ||
202 | if (signal_pending_state(state, current)) | |
203 | return -ERESTARTSYS; | |
204 | ||
205 | wait->private = current; | |
206 | wait->func = autoremove_wake_function; | |
207 | ||
208 | spin_lock_irqsave(&q->lock, flags); | |
209 | if (list_empty(&wait->task_list)) { | |
210 | if (wait->flags & WQ_FLAG_EXCLUSIVE) | |
211 | __add_wait_queue_tail(q, wait); | |
212 | else | |
213 | __add_wait_queue(q, wait); | |
214 | } | |
215 | set_current_state(state); | |
216 | spin_unlock_irqrestore(&q->lock, flags); | |
217 | ||
218 | return 0; | |
219 | } | |
220 | EXPORT_SYMBOL(prepare_to_wait_event); | |
221 | ||
ee2f154a | 222 | /** |
777c6c5f JW |
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 | */ | |
7ad5b3a5 | 231 | void finish_wait(wait_queue_head_t *q, wait_queue_t *wait) |
1da177e4 LT |
232 | { |
233 | unsigned long flags; | |
234 | ||
235 | __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 | if (!list_empty_careful(&wait->task_list)) { | |
250 | spin_lock_irqsave(&q->lock, flags); | |
251 | list_del_init(&wait->task_list); | |
252 | spin_unlock_irqrestore(&q->lock, flags); | |
253 | } | |
254 | } | |
255 | EXPORT_SYMBOL(finish_wait); | |
256 | ||
ee2f154a | 257 | /** |
777c6c5f JW |
258 | * abort_exclusive_wait - abort exclusive waiting in a queue |
259 | * @q: waitqueue waited on | |
260 | * @wait: wait descriptor | |
ee2f154a | 261 | * @mode: runstate of the waiter to be woken |
777c6c5f JW |
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 | |
25985edc | 272 | * aborts and is woken up concurrently and no one wakes up |
777c6c5f JW |
273 | * the next waiter. |
274 | */ | |
275 | 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 | __set_current_state(TASK_RUNNING); | |
281 | spin_lock_irqsave(&q->lock, flags); | |
282 | if (!list_empty(&wait->task_list)) | |
283 | list_del_init(&wait->task_list); | |
284 | else if (waitqueue_active(q)) | |
78ddb08f | 285 | __wake_up_locked_key(q, mode, key); |
777c6c5f JW |
286 | spin_unlock_irqrestore(&q->lock, flags); |
287 | } | |
288 | EXPORT_SYMBOL(abort_exclusive_wait); | |
289 | ||
1da177e4 LT |
290 | int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key) |
291 | { | |
292 | int ret = default_wake_function(wait, mode, sync, key); | |
293 | ||
294 | if (ret) | |
295 | list_del_init(&wait->task_list); | |
296 | return ret; | |
297 | } | |
298 | EXPORT_SYMBOL(autoremove_wake_function); | |
299 | ||
300 | 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 | if (wait_bit->key.flags != key->flags || | |
307 | wait_bit->key.bit_nr != key->bit_nr || | |
308 | test_bit(key->bit_nr, key->flags)) | |
309 | return 0; | |
310 | else | |
311 | 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 | */ | |
7ad5b3a5 | 320 | int __sched |
1da177e4 LT |
321 | __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 | prepare_to_wait(wq, &q->wait, mode); | |
328 | if (test_bit(q->key.bit_nr, q->key.flags)) | |
329 | ret = (*action)(q->key.flags); | |
330 | } while (test_bit(q->key.bit_nr, q->key.flags) && !ret); | |
331 | finish_wait(wq, &q->wait); | |
332 | return ret; | |
333 | } | |
334 | EXPORT_SYMBOL(__wait_on_bit); | |
335 | ||
7ad5b3a5 | 336 | int __sched out_of_line_wait_on_bit(void *word, int bit, |
1da177e4 LT |
337 | int (*action)(void *), unsigned mode) |
338 | { | |
339 | wait_queue_head_t *wq = bit_waitqueue(word, bit); | |
340 | DEFINE_WAIT_BIT(wait, word, bit); | |
341 | ||
342 | return __wait_on_bit(wq, &wait, action, mode); | |
343 | } | |
344 | EXPORT_SYMBOL(out_of_line_wait_on_bit); | |
345 | ||
7ad5b3a5 | 346 | int __sched |
1da177e4 LT |
347 | __wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q, |
348 | int (*action)(void *), unsigned mode) | |
349 | { | |
1da177e4 | 350 | do { |
777c6c5f JW |
351 | int ret; |
352 | ||
1da177e4 | 353 | prepare_to_wait_exclusive(wq, &q->wait, mode); |
777c6c5f JW |
354 | if (!test_bit(q->key.bit_nr, q->key.flags)) |
355 | continue; | |
356 | ret = action(q->key.flags); | |
357 | if (!ret) | |
358 | continue; | |
359 | abort_exclusive_wait(wq, &q->wait, mode, &q->key); | |
360 | return ret; | |
1da177e4 LT |
361 | } while (test_and_set_bit(q->key.bit_nr, q->key.flags)); |
362 | finish_wait(wq, &q->wait); | |
777c6c5f | 363 | return 0; |
1da177e4 LT |
364 | } |
365 | EXPORT_SYMBOL(__wait_on_bit_lock); | |
366 | ||
7ad5b3a5 | 367 | int __sched out_of_line_wait_on_bit_lock(void *word, int bit, |
1da177e4 LT |
368 | int (*action)(void *), unsigned mode) |
369 | { | |
370 | wait_queue_head_t *wq = bit_waitqueue(word, bit); | |
371 | DEFINE_WAIT_BIT(wait, word, bit); | |
372 | ||
373 | return __wait_on_bit_lock(wq, &wait, action, mode); | |
374 | } | |
375 | EXPORT_SYMBOL(out_of_line_wait_on_bit_lock); | |
376 | ||
7ad5b3a5 | 377 | void __wake_up_bit(wait_queue_head_t *wq, void *word, int bit) |
1da177e4 LT |
378 | { |
379 | struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit); | |
380 | if (waitqueue_active(wq)) | |
e64d66c8 | 381 | __wake_up(wq, TASK_NORMAL, 1, &key); |
1da177e4 LT |
382 | } |
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 | */ | |
7ad5b3a5 | 402 | void wake_up_bit(void *word, int bit) |
1da177e4 LT |
403 | { |
404 | __wake_up_bit(bit_waitqueue(word, bit), word, bit); | |
405 | } | |
406 | EXPORT_SYMBOL(wake_up_bit); | |
407 | ||
7ad5b3a5 | 408 | wait_queue_head_t *bit_waitqueue(void *word, int bit) |
1da177e4 LT |
409 | { |
410 | const int shift = BITS_PER_LONG == 32 ? 5 : 6; | |
411 | const struct zone *zone = page_zone(virt_to_page(word)); | |
412 | unsigned long val = (unsigned long)word << shift | bit; | |
413 | ||
414 | return &zone->wait_table[hash_long(val, zone->wait_table_bits)]; | |
415 | } | |
416 | EXPORT_SYMBOL(bit_waitqueue); | |
cb65537e DH |
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 | return bit_waitqueue(p, 0); | |
430 | } | |
431 | ||
432 | 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 | atomic_t *val = key->flags; | |
439 | ||
440 | if (wait_bit->key.flags != key->flags || | |
441 | wait_bit->key.bit_nr != key->bit_nr || | |
442 | atomic_read(val) != 0) | |
443 | return 0; | |
444 | 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 | 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 | prepare_to_wait(wq, &q->wait, mode); | |
461 | val = q->key.flags; | |
462 | if (atomic_read(val) == 0) | |
42577ca8 DH |
463 | break; |
464 | ret = (*action)(val); | |
cb65537e DH |
465 | } while (!ret && atomic_read(val) != 0); |
466 | finish_wait(wq, &q->wait); | |
467 | 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 | __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 | DEFINE_WAIT_ATOMIC_T(wait, p); | |
486 | ||
487 | 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 | |
2203547f | 493 | * @p: The atomic_t being waited on, a kernel virtual address |
cb65537e DH |
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 | void wake_up_atomic_t(atomic_t *p) | |
501 | { | |
502 | __wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR); | |
503 | } | |
504 | EXPORT_SYMBOL(wake_up_atomic_t); |