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