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b8a21626 PZ |
1 | /* |
2 | * Generic wait-for-completion handler; | |
3 | * | |
4 | * It differs from semaphores in that their default case is the opposite, | |
5 | * wait_for_completion default blocks whereas semaphore default non-block. The | |
6 | * interface also makes it easy to 'complete' multiple waiting threads, | |
7 | * something which isn't entirely natural for semaphores. | |
8 | * | |
9 | * But more importantly, the primitive documents the usage. Semaphores would | |
10 | * typically be used for exclusion which gives rise to priority inversion. | |
11 | * Waiting for completion is a typically sync point, but not an exclusion point. | |
12 | */ | |
13 | ||
174cd4b1 | 14 | #include <linux/sched/signal.h> |
b17b0153 | 15 | #include <linux/sched/debug.h> |
b8a21626 PZ |
16 | #include <linux/completion.h> |
17 | ||
18 | /** | |
19 | * complete: - signals a single thread waiting on this completion | |
20 | * @x: holds the state of this particular completion | |
21 | * | |
22 | * This will wake up a single thread waiting on this completion. Threads will be | |
23 | * awakened in the same order in which they were queued. | |
24 | * | |
25 | * See also complete_all(), wait_for_completion() and related routines. | |
26 | * | |
27 | * It may be assumed that this function implies a write memory barrier before | |
28 | * changing the task state if and only if any tasks are woken up. | |
29 | */ | |
30 | void complete(struct completion *x) | |
31 | { | |
32 | unsigned long flags; | |
33 | ||
34 | spin_lock_irqsave(&x->wait.lock, flags); | |
cd8084f9 BP |
35 | |
36 | /* | |
37 | * Perform commit of crossrelease here. | |
38 | */ | |
39 | complete_release_commit(x); | |
40 | ||
da9647e0 PZ |
41 | if (x->done != UINT_MAX) |
42 | x->done++; | |
b8a21626 PZ |
43 | __wake_up_locked(&x->wait, TASK_NORMAL, 1); |
44 | spin_unlock_irqrestore(&x->wait.lock, flags); | |
45 | } | |
46 | EXPORT_SYMBOL(complete); | |
47 | ||
48 | /** | |
49 | * complete_all: - signals all threads waiting on this completion | |
50 | * @x: holds the state of this particular completion | |
51 | * | |
52 | * This will wake up all threads waiting on this particular completion event. | |
53 | * | |
54 | * It may be assumed that this function implies a write memory barrier before | |
55 | * changing the task state if and only if any tasks are woken up. | |
9c878320 SR |
56 | * |
57 | * Since complete_all() sets the completion of @x permanently to done | |
58 | * to allow multiple waiters to finish, a call to reinit_completion() | |
59 | * must be used on @x if @x is to be used again. The code must make | |
60 | * sure that all waiters have woken and finished before reinitializing | |
61 | * @x. Also note that the function completion_done() can not be used | |
62 | * to know if there are still waiters after complete_all() has been called. | |
b8a21626 PZ |
63 | */ |
64 | void complete_all(struct completion *x) | |
65 | { | |
66 | unsigned long flags; | |
67 | ||
68 | spin_lock_irqsave(&x->wait.lock, flags); | |
da9647e0 | 69 | x->done = UINT_MAX; |
b8a21626 PZ |
70 | __wake_up_locked(&x->wait, TASK_NORMAL, 0); |
71 | spin_unlock_irqrestore(&x->wait.lock, flags); | |
72 | } | |
73 | EXPORT_SYMBOL(complete_all); | |
74 | ||
75 | static inline long __sched | |
76 | do_wait_for_common(struct completion *x, | |
77 | long (*action)(long), long timeout, int state) | |
78 | { | |
79 | if (!x->done) { | |
80 | DECLARE_WAITQUEUE(wait, current); | |
81 | ||
ac6424b9 | 82 | __add_wait_queue_entry_tail_exclusive(&x->wait, &wait); |
b8a21626 PZ |
83 | do { |
84 | if (signal_pending_state(state, current)) { | |
85 | timeout = -ERESTARTSYS; | |
86 | break; | |
87 | } | |
88 | __set_current_state(state); | |
89 | spin_unlock_irq(&x->wait.lock); | |
90 | timeout = action(timeout); | |
91 | spin_lock_irq(&x->wait.lock); | |
92 | } while (!x->done && timeout); | |
93 | __remove_wait_queue(&x->wait, &wait); | |
94 | if (!x->done) | |
95 | return timeout; | |
96 | } | |
da9647e0 PZ |
97 | if (x->done != UINT_MAX) |
98 | x->done--; | |
b8a21626 PZ |
99 | return timeout ?: 1; |
100 | } | |
101 | ||
102 | static inline long __sched | |
103 | __wait_for_common(struct completion *x, | |
104 | long (*action)(long), long timeout, int state) | |
105 | { | |
106 | might_sleep(); | |
107 | ||
cd8084f9 BP |
108 | complete_acquire(x); |
109 | ||
b8a21626 PZ |
110 | spin_lock_irq(&x->wait.lock); |
111 | timeout = do_wait_for_common(x, action, timeout, state); | |
112 | spin_unlock_irq(&x->wait.lock); | |
cd8084f9 BP |
113 | |
114 | complete_release(x); | |
115 | ||
b8a21626 PZ |
116 | return timeout; |
117 | } | |
118 | ||
119 | static long __sched | |
120 | wait_for_common(struct completion *x, long timeout, int state) | |
121 | { | |
122 | return __wait_for_common(x, schedule_timeout, timeout, state); | |
123 | } | |
124 | ||
125 | static long __sched | |
126 | wait_for_common_io(struct completion *x, long timeout, int state) | |
127 | { | |
128 | return __wait_for_common(x, io_schedule_timeout, timeout, state); | |
129 | } | |
130 | ||
131 | /** | |
132 | * wait_for_completion: - waits for completion of a task | |
133 | * @x: holds the state of this particular completion | |
134 | * | |
135 | * This waits to be signaled for completion of a specific task. It is NOT | |
136 | * interruptible and there is no timeout. | |
137 | * | |
138 | * See also similar routines (i.e. wait_for_completion_timeout()) with timeout | |
139 | * and interrupt capability. Also see complete(). | |
140 | */ | |
141 | void __sched wait_for_completion(struct completion *x) | |
142 | { | |
143 | wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE); | |
144 | } | |
145 | EXPORT_SYMBOL(wait_for_completion); | |
146 | ||
147 | /** | |
148 | * wait_for_completion_timeout: - waits for completion of a task (w/timeout) | |
149 | * @x: holds the state of this particular completion | |
150 | * @timeout: timeout value in jiffies | |
151 | * | |
152 | * This waits for either a completion of a specific task to be signaled or for a | |
153 | * specified timeout to expire. The timeout is in jiffies. It is not | |
154 | * interruptible. | |
155 | * | |
156 | * Return: 0 if timed out, and positive (at least 1, or number of jiffies left | |
157 | * till timeout) if completed. | |
158 | */ | |
159 | unsigned long __sched | |
160 | wait_for_completion_timeout(struct completion *x, unsigned long timeout) | |
161 | { | |
162 | return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE); | |
163 | } | |
164 | EXPORT_SYMBOL(wait_for_completion_timeout); | |
165 | ||
166 | /** | |
167 | * wait_for_completion_io: - waits for completion of a task | |
168 | * @x: holds the state of this particular completion | |
169 | * | |
170 | * This waits to be signaled for completion of a specific task. It is NOT | |
171 | * interruptible and there is no timeout. The caller is accounted as waiting | |
a1bd5373 | 172 | * for IO (which traditionally means blkio only). |
b8a21626 PZ |
173 | */ |
174 | void __sched wait_for_completion_io(struct completion *x) | |
175 | { | |
176 | wait_for_common_io(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE); | |
177 | } | |
178 | EXPORT_SYMBOL(wait_for_completion_io); | |
179 | ||
180 | /** | |
181 | * wait_for_completion_io_timeout: - waits for completion of a task (w/timeout) | |
182 | * @x: holds the state of this particular completion | |
183 | * @timeout: timeout value in jiffies | |
184 | * | |
185 | * This waits for either a completion of a specific task to be signaled or for a | |
186 | * specified timeout to expire. The timeout is in jiffies. It is not | |
a1bd5373 WS |
187 | * interruptible. The caller is accounted as waiting for IO (which traditionally |
188 | * means blkio only). | |
b8a21626 PZ |
189 | * |
190 | * Return: 0 if timed out, and positive (at least 1, or number of jiffies left | |
191 | * till timeout) if completed. | |
192 | */ | |
193 | unsigned long __sched | |
194 | wait_for_completion_io_timeout(struct completion *x, unsigned long timeout) | |
195 | { | |
196 | return wait_for_common_io(x, timeout, TASK_UNINTERRUPTIBLE); | |
197 | } | |
198 | EXPORT_SYMBOL(wait_for_completion_io_timeout); | |
199 | ||
200 | /** | |
201 | * wait_for_completion_interruptible: - waits for completion of a task (w/intr) | |
202 | * @x: holds the state of this particular completion | |
203 | * | |
204 | * This waits for completion of a specific task to be signaled. It is | |
205 | * interruptible. | |
206 | * | |
207 | * Return: -ERESTARTSYS if interrupted, 0 if completed. | |
208 | */ | |
209 | int __sched wait_for_completion_interruptible(struct completion *x) | |
210 | { | |
211 | long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE); | |
212 | if (t == -ERESTARTSYS) | |
213 | return t; | |
214 | return 0; | |
215 | } | |
216 | EXPORT_SYMBOL(wait_for_completion_interruptible); | |
217 | ||
218 | /** | |
219 | * wait_for_completion_interruptible_timeout: - waits for completion (w/(to,intr)) | |
220 | * @x: holds the state of this particular completion | |
221 | * @timeout: timeout value in jiffies | |
222 | * | |
223 | * This waits for either a completion of a specific task to be signaled or for a | |
224 | * specified timeout to expire. It is interruptible. The timeout is in jiffies. | |
225 | * | |
226 | * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1, | |
227 | * or number of jiffies left till timeout) if completed. | |
228 | */ | |
229 | long __sched | |
230 | wait_for_completion_interruptible_timeout(struct completion *x, | |
231 | unsigned long timeout) | |
232 | { | |
233 | return wait_for_common(x, timeout, TASK_INTERRUPTIBLE); | |
234 | } | |
235 | EXPORT_SYMBOL(wait_for_completion_interruptible_timeout); | |
236 | ||
237 | /** | |
238 | * wait_for_completion_killable: - waits for completion of a task (killable) | |
239 | * @x: holds the state of this particular completion | |
240 | * | |
241 | * This waits to be signaled for completion of a specific task. It can be | |
242 | * interrupted by a kill signal. | |
243 | * | |
244 | * Return: -ERESTARTSYS if interrupted, 0 if completed. | |
245 | */ | |
246 | int __sched wait_for_completion_killable(struct completion *x) | |
247 | { | |
248 | long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE); | |
249 | if (t == -ERESTARTSYS) | |
250 | return t; | |
251 | return 0; | |
252 | } | |
253 | EXPORT_SYMBOL(wait_for_completion_killable); | |
254 | ||
255 | /** | |
256 | * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable)) | |
257 | * @x: holds the state of this particular completion | |
258 | * @timeout: timeout value in jiffies | |
259 | * | |
260 | * This waits for either a completion of a specific task to be | |
261 | * signaled or for a specified timeout to expire. It can be | |
262 | * interrupted by a kill signal. The timeout is in jiffies. | |
263 | * | |
264 | * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1, | |
265 | * or number of jiffies left till timeout) if completed. | |
266 | */ | |
267 | long __sched | |
268 | wait_for_completion_killable_timeout(struct completion *x, | |
269 | unsigned long timeout) | |
270 | { | |
271 | return wait_for_common(x, timeout, TASK_KILLABLE); | |
272 | } | |
273 | EXPORT_SYMBOL(wait_for_completion_killable_timeout); | |
274 | ||
275 | /** | |
276 | * try_wait_for_completion - try to decrement a completion without blocking | |
277 | * @x: completion structure | |
278 | * | |
279 | * Return: 0 if a decrement cannot be done without blocking | |
280 | * 1 if a decrement succeeded. | |
281 | * | |
282 | * If a completion is being used as a counting completion, | |
283 | * attempt to decrement the counter without blocking. This | |
284 | * enables us to avoid waiting if the resource the completion | |
285 | * is protecting is not available. | |
286 | */ | |
287 | bool try_wait_for_completion(struct completion *x) | |
288 | { | |
289 | unsigned long flags; | |
290 | int ret = 1; | |
291 | ||
7c34e318 NMG |
292 | /* |
293 | * Since x->done will need to be locked only | |
294 | * in the non-blocking case, we check x->done | |
295 | * first without taking the lock so we can | |
296 | * return early in the blocking case. | |
297 | */ | |
bc956015 | 298 | if (!READ_ONCE(x->done)) |
7c34e318 NMG |
299 | return 0; |
300 | ||
b8a21626 PZ |
301 | spin_lock_irqsave(&x->wait.lock, flags); |
302 | if (!x->done) | |
303 | ret = 0; | |
da9647e0 | 304 | else if (x->done != UINT_MAX) |
b8a21626 PZ |
305 | x->done--; |
306 | spin_unlock_irqrestore(&x->wait.lock, flags); | |
307 | return ret; | |
308 | } | |
309 | EXPORT_SYMBOL(try_wait_for_completion); | |
310 | ||
311 | /** | |
312 | * completion_done - Test to see if a completion has any waiters | |
313 | * @x: completion structure | |
314 | * | |
315 | * Return: 0 if there are waiters (wait_for_completion() in progress) | |
316 | * 1 if there are no waiters. | |
317 | * | |
9c878320 | 318 | * Note, this will always return true if complete_all() was called on @X. |
b8a21626 PZ |
319 | */ |
320 | bool completion_done(struct completion *x) | |
321 | { | |
dec13c42 PM |
322 | unsigned long flags; |
323 | ||
bc956015 ON |
324 | if (!READ_ONCE(x->done)) |
325 | return false; | |
326 | ||
327 | /* | |
328 | * If ->done, we need to wait for complete() to release ->wait.lock | |
329 | * otherwise we can end up freeing the completion before complete() | |
330 | * is done referencing it. | |
bc956015 | 331 | */ |
dec13c42 PM |
332 | spin_lock_irqsave(&x->wait.lock, flags); |
333 | spin_unlock_irqrestore(&x->wait.lock, flags); | |
bc956015 | 334 | return true; |
b8a21626 PZ |
335 | } |
336 | EXPORT_SYMBOL(completion_done); |