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