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