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