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