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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
b8a21626 PZ |
2 | /* |
3 | * Generic wait-for-completion handler; | |
4 | * | |
5 | * It differs from semaphores in that their default case is the opposite, | |
6 | * wait_for_completion default blocks whereas semaphore default non-block. The | |
7 | * interface also makes it easy to 'complete' multiple waiting threads, | |
8 | * something which isn't entirely natural for semaphores. | |
9 | * | |
10 | * But more importantly, the primitive documents the usage. Semaphores would | |
11 | * typically be used for exclusion which gives rise to priority inversion. | |
12 | * Waiting for completion is a typically sync point, but not an exclusion point. | |
13 | */ | |
325ea10c | 14 | #include "sched.h" |
b8a21626 PZ |
15 | |
16 | /** | |
17 | * complete: - signals a single thread waiting on this completion | |
18 | * @x: holds the state of this particular completion | |
19 | * | |
20 | * This will wake up a single thread waiting on this completion. Threads will be | |
21 | * awakened in the same order in which they were queued. | |
22 | * | |
23 | * See also complete_all(), wait_for_completion() and related routines. | |
24 | * | |
7696f991 AP |
25 | * If this function wakes up a task, it executes a full memory barrier before |
26 | * accessing the task state. | |
b8a21626 PZ |
27 | */ |
28 | void complete(struct completion *x) | |
29 | { | |
30 | unsigned long flags; | |
31 | ||
32 | spin_lock_irqsave(&x->wait.lock, flags); | |
cd8084f9 | 33 | |
da9647e0 PZ |
34 | if (x->done != UINT_MAX) |
35 | x->done++; | |
b8a21626 PZ |
36 | __wake_up_locked(&x->wait, TASK_NORMAL, 1); |
37 | spin_unlock_irqrestore(&x->wait.lock, flags); | |
38 | } | |
39 | EXPORT_SYMBOL(complete); | |
40 | ||
41 | /** | |
42 | * complete_all: - signals all threads waiting on this completion | |
43 | * @x: holds the state of this particular completion | |
44 | * | |
45 | * This will wake up all threads waiting on this particular completion event. | |
46 | * | |
7696f991 AP |
47 | * If this function wakes up a task, it executes a full memory barrier before |
48 | * accessing the task state. | |
9c878320 SR |
49 | * |
50 | * Since complete_all() sets the completion of @x permanently to done | |
51 | * to allow multiple waiters to finish, a call to reinit_completion() | |
52 | * must be used on @x if @x is to be used again. The code must make | |
53 | * sure that all waiters have woken and finished before reinitializing | |
54 | * @x. Also note that the function completion_done() can not be used | |
55 | * to know if there are still waiters after complete_all() has been called. | |
b8a21626 PZ |
56 | */ |
57 | void complete_all(struct completion *x) | |
58 | { | |
59 | unsigned long flags; | |
60 | ||
61 | spin_lock_irqsave(&x->wait.lock, flags); | |
da9647e0 | 62 | x->done = UINT_MAX; |
b8a21626 PZ |
63 | __wake_up_locked(&x->wait, TASK_NORMAL, 0); |
64 | spin_unlock_irqrestore(&x->wait.lock, flags); | |
65 | } | |
66 | EXPORT_SYMBOL(complete_all); | |
67 | ||
68 | static inline long __sched | |
69 | do_wait_for_common(struct completion *x, | |
70 | long (*action)(long), long timeout, int state) | |
71 | { | |
72 | if (!x->done) { | |
73 | DECLARE_WAITQUEUE(wait, current); | |
74 | ||
ac6424b9 | 75 | __add_wait_queue_entry_tail_exclusive(&x->wait, &wait); |
b8a21626 PZ |
76 | do { |
77 | if (signal_pending_state(state, current)) { | |
78 | timeout = -ERESTARTSYS; | |
79 | break; | |
80 | } | |
81 | __set_current_state(state); | |
82 | spin_unlock_irq(&x->wait.lock); | |
83 | timeout = action(timeout); | |
84 | spin_lock_irq(&x->wait.lock); | |
85 | } while (!x->done && timeout); | |
86 | __remove_wait_queue(&x->wait, &wait); | |
87 | if (!x->done) | |
88 | return timeout; | |
89 | } | |
da9647e0 PZ |
90 | if (x->done != UINT_MAX) |
91 | x->done--; | |
b8a21626 PZ |
92 | return timeout ?: 1; |
93 | } | |
94 | ||
95 | static inline long __sched | |
96 | __wait_for_common(struct completion *x, | |
97 | long (*action)(long), long timeout, int state) | |
98 | { | |
99 | might_sleep(); | |
100 | ||
cd8084f9 BP |
101 | complete_acquire(x); |
102 | ||
b8a21626 PZ |
103 | spin_lock_irq(&x->wait.lock); |
104 | timeout = do_wait_for_common(x, action, timeout, state); | |
105 | spin_unlock_irq(&x->wait.lock); | |
cd8084f9 BP |
106 | |
107 | complete_release(x); | |
108 | ||
b8a21626 PZ |
109 | return timeout; |
110 | } | |
111 | ||
112 | static long __sched | |
113 | wait_for_common(struct completion *x, long timeout, int state) | |
114 | { | |
115 | return __wait_for_common(x, schedule_timeout, timeout, state); | |
116 | } | |
117 | ||
118 | static long __sched | |
119 | wait_for_common_io(struct completion *x, long timeout, int state) | |
120 | { | |
121 | return __wait_for_common(x, io_schedule_timeout, timeout, state); | |
122 | } | |
123 | ||
124 | /** | |
125 | * wait_for_completion: - waits for completion of a task | |
126 | * @x: holds the state of this particular completion | |
127 | * | |
128 | * This waits to be signaled for completion of a specific task. It is NOT | |
129 | * interruptible and there is no timeout. | |
130 | * | |
131 | * See also similar routines (i.e. wait_for_completion_timeout()) with timeout | |
132 | * and interrupt capability. Also see complete(). | |
133 | */ | |
134 | void __sched wait_for_completion(struct completion *x) | |
135 | { | |
136 | wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE); | |
137 | } | |
138 | EXPORT_SYMBOL(wait_for_completion); | |
139 | ||
140 | /** | |
141 | * wait_for_completion_timeout: - waits for completion of a task (w/timeout) | |
142 | * @x: holds the state of this particular completion | |
143 | * @timeout: timeout value in jiffies | |
144 | * | |
145 | * This waits for either a completion of a specific task to be signaled or for a | |
146 | * specified timeout to expire. The timeout is in jiffies. It is not | |
147 | * interruptible. | |
148 | * | |
149 | * Return: 0 if timed out, and positive (at least 1, or number of jiffies left | |
150 | * till timeout) if completed. | |
151 | */ | |
152 | unsigned long __sched | |
153 | wait_for_completion_timeout(struct completion *x, unsigned long timeout) | |
154 | { | |
155 | return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE); | |
156 | } | |
157 | EXPORT_SYMBOL(wait_for_completion_timeout); | |
158 | ||
159 | /** | |
160 | * wait_for_completion_io: - waits for completion of a task | |
161 | * @x: holds the state of this particular completion | |
162 | * | |
163 | * This waits to be signaled for completion of a specific task. It is NOT | |
164 | * interruptible and there is no timeout. The caller is accounted as waiting | |
a1bd5373 | 165 | * for IO (which traditionally means blkio only). |
b8a21626 PZ |
166 | */ |
167 | void __sched wait_for_completion_io(struct completion *x) | |
168 | { | |
169 | wait_for_common_io(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE); | |
170 | } | |
171 | EXPORT_SYMBOL(wait_for_completion_io); | |
172 | ||
173 | /** | |
174 | * wait_for_completion_io_timeout: - waits for completion of a task (w/timeout) | |
175 | * @x: holds the state of this particular completion | |
176 | * @timeout: timeout value in jiffies | |
177 | * | |
178 | * This waits for either a completion of a specific task to be signaled or for a | |
179 | * specified timeout to expire. The timeout is in jiffies. It is not | |
a1bd5373 WS |
180 | * interruptible. The caller is accounted as waiting for IO (which traditionally |
181 | * means blkio only). | |
b8a21626 PZ |
182 | * |
183 | * Return: 0 if timed out, and positive (at least 1, or number of jiffies left | |
184 | * till timeout) if completed. | |
185 | */ | |
186 | unsigned long __sched | |
187 | wait_for_completion_io_timeout(struct completion *x, unsigned long timeout) | |
188 | { | |
189 | return wait_for_common_io(x, timeout, TASK_UNINTERRUPTIBLE); | |
190 | } | |
191 | EXPORT_SYMBOL(wait_for_completion_io_timeout); | |
192 | ||
193 | /** | |
194 | * wait_for_completion_interruptible: - waits for completion of a task (w/intr) | |
195 | * @x: holds the state of this particular completion | |
196 | * | |
197 | * This waits for completion of a specific task to be signaled. It is | |
198 | * interruptible. | |
199 | * | |
200 | * Return: -ERESTARTSYS if interrupted, 0 if completed. | |
201 | */ | |
202 | int __sched wait_for_completion_interruptible(struct completion *x) | |
203 | { | |
204 | long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE); | |
205 | if (t == -ERESTARTSYS) | |
206 | return t; | |
207 | return 0; | |
208 | } | |
209 | EXPORT_SYMBOL(wait_for_completion_interruptible); | |
210 | ||
211 | /** | |
212 | * wait_for_completion_interruptible_timeout: - waits for completion (w/(to,intr)) | |
213 | * @x: holds the state of this particular completion | |
214 | * @timeout: timeout value in jiffies | |
215 | * | |
216 | * This waits for either a completion of a specific task to be signaled or for a | |
217 | * specified timeout to expire. It is interruptible. The timeout is in jiffies. | |
218 | * | |
219 | * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1, | |
220 | * or number of jiffies left till timeout) if completed. | |
221 | */ | |
222 | long __sched | |
223 | wait_for_completion_interruptible_timeout(struct completion *x, | |
224 | unsigned long timeout) | |
225 | { | |
226 | return wait_for_common(x, timeout, TASK_INTERRUPTIBLE); | |
227 | } | |
228 | EXPORT_SYMBOL(wait_for_completion_interruptible_timeout); | |
229 | ||
230 | /** | |
231 | * wait_for_completion_killable: - waits for completion of a task (killable) | |
232 | * @x: holds the state of this particular completion | |
233 | * | |
234 | * This waits to be signaled for completion of a specific task. It can be | |
235 | * interrupted by a kill signal. | |
236 | * | |
237 | * Return: -ERESTARTSYS if interrupted, 0 if completed. | |
238 | */ | |
239 | int __sched wait_for_completion_killable(struct completion *x) | |
240 | { | |
241 | long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE); | |
242 | if (t == -ERESTARTSYS) | |
243 | return t; | |
244 | return 0; | |
245 | } | |
246 | EXPORT_SYMBOL(wait_for_completion_killable); | |
247 | ||
248 | /** | |
249 | * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable)) | |
250 | * @x: holds the state of this particular completion | |
251 | * @timeout: timeout value in jiffies | |
252 | * | |
253 | * This waits for either a completion of a specific task to be | |
254 | * signaled or for a specified timeout to expire. It can be | |
255 | * interrupted by a kill signal. The timeout is in jiffies. | |
256 | * | |
257 | * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1, | |
258 | * or number of jiffies left till timeout) if completed. | |
259 | */ | |
260 | long __sched | |
261 | wait_for_completion_killable_timeout(struct completion *x, | |
262 | unsigned long timeout) | |
263 | { | |
264 | return wait_for_common(x, timeout, TASK_KILLABLE); | |
265 | } | |
266 | EXPORT_SYMBOL(wait_for_completion_killable_timeout); | |
267 | ||
268 | /** | |
269 | * try_wait_for_completion - try to decrement a completion without blocking | |
270 | * @x: completion structure | |
271 | * | |
272 | * Return: 0 if a decrement cannot be done without blocking | |
273 | * 1 if a decrement succeeded. | |
274 | * | |
275 | * If a completion is being used as a counting completion, | |
276 | * attempt to decrement the counter without blocking. This | |
277 | * enables us to avoid waiting if the resource the completion | |
278 | * is protecting is not available. | |
279 | */ | |
280 | bool try_wait_for_completion(struct completion *x) | |
281 | { | |
282 | unsigned long flags; | |
d17067e4 | 283 | bool ret = true; |
b8a21626 | 284 | |
7c34e318 NMG |
285 | /* |
286 | * Since x->done will need to be locked only | |
287 | * in the non-blocking case, we check x->done | |
288 | * first without taking the lock so we can | |
289 | * return early in the blocking case. | |
290 | */ | |
bc956015 | 291 | if (!READ_ONCE(x->done)) |
d17067e4 | 292 | return false; |
7c34e318 | 293 | |
b8a21626 PZ |
294 | spin_lock_irqsave(&x->wait.lock, flags); |
295 | if (!x->done) | |
d17067e4 | 296 | ret = false; |
da9647e0 | 297 | else if (x->done != UINT_MAX) |
b8a21626 PZ |
298 | x->done--; |
299 | spin_unlock_irqrestore(&x->wait.lock, flags); | |
300 | return ret; | |
301 | } | |
302 | EXPORT_SYMBOL(try_wait_for_completion); | |
303 | ||
304 | /** | |
305 | * completion_done - Test to see if a completion has any waiters | |
306 | * @x: completion structure | |
307 | * | |
308 | * Return: 0 if there are waiters (wait_for_completion() in progress) | |
309 | * 1 if there are no waiters. | |
310 | * | |
9c878320 | 311 | * Note, this will always return true if complete_all() was called on @X. |
b8a21626 PZ |
312 | */ |
313 | bool completion_done(struct completion *x) | |
314 | { | |
dec13c42 PM |
315 | unsigned long flags; |
316 | ||
bc956015 ON |
317 | if (!READ_ONCE(x->done)) |
318 | return false; | |
319 | ||
320 | /* | |
321 | * If ->done, we need to wait for complete() to release ->wait.lock | |
322 | * otherwise we can end up freeing the completion before complete() | |
323 | * is done referencing it. | |
bc956015 | 324 | */ |
dec13c42 PM |
325 | spin_lock_irqsave(&x->wait.lock, flags); |
326 | spin_unlock_irqrestore(&x->wait.lock, flags); | |
bc956015 | 327 | return true; |
b8a21626 PZ |
328 | } |
329 | EXPORT_SYMBOL(completion_done); |