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1// SPDX-License-Identifier: GPL-2.0
2
3/*
4 * Generic wait-for-completion handler;
5 *
6 * It differs from semaphores in that their default case is the opposite,
7 * wait_for_completion default blocks whereas semaphore default non-block. The
8 * interface also makes it easy to 'complete' multiple waiting threads,
9 * something which isn't entirely natural for semaphores.
10 *
11 * But more importantly, the primitive documents the usage. Semaphores would
12 * typically be used for exclusion which gives rise to priority inversion.
13 * Waiting for completion is a typically sync point, but not an exclusion point.
14 */
15
16/**
17 * complete: - signals a single thread waiting on this completion
18 * @x: holds the state of this particular completion
19 *
20 * This will wake up a single thread waiting on this completion. Threads will be
21 * awakened in the same order in which they were queued.
22 *
23 * See also complete_all(), wait_for_completion() and related routines.
24 *
25 * If this function wakes up a task, it executes a full memory barrier before
26 * accessing the task state.
27 */
28void complete(struct completion *x)
29{
30 unsigned long flags;
31
32 raw_spin_lock_irqsave(&x->wait.lock, flags);
33
34 if (x->done != UINT_MAX)
35 x->done++;
36 swake_up_locked(&x->wait);
37 raw_spin_unlock_irqrestore(&x->wait.lock, flags);
38}
39EXPORT_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 * If this function wakes up a task, it executes a full memory barrier before
48 * accessing the task state.
49 *
50 * Since complete_all() sets the completion of @x permanently to done
51 * to allow multiple waiters to finish, a call to reinit_completion()
52 * must be used on @x if @x is to be used again. The code must make
53 * sure that all waiters have woken and finished before reinitializing
54 * @x. Also note that the function completion_done() can not be used
55 * to know if there are still waiters after complete_all() has been called.
56 */
57void complete_all(struct completion *x)
58{
59 unsigned long flags;
60
61 lockdep_assert_RT_in_threaded_ctx();
62
63 raw_spin_lock_irqsave(&x->wait.lock, flags);
64 x->done = UINT_MAX;
65 swake_up_all_locked(&x->wait);
66 raw_spin_unlock_irqrestore(&x->wait.lock, flags);
67}
68EXPORT_SYMBOL(complete_all);
69
70static inline long __sched
71do_wait_for_common(struct completion *x,
72 long (*action)(long), long timeout, int state)
73{
74 if (!x->done) {
75 DECLARE_SWAITQUEUE(wait);
76
77 do {
78 if (signal_pending_state(state, current)) {
79 timeout = -ERESTARTSYS;
80 break;
81 }
82 __prepare_to_swait(&x->wait, &wait);
83 __set_current_state(state);
84 raw_spin_unlock_irq(&x->wait.lock);
85 timeout = action(timeout);
86 raw_spin_lock_irq(&x->wait.lock);
87 } while (!x->done && timeout);
88 __finish_swait(&x->wait, &wait);
89 if (!x->done)
90 return timeout;
91 }
92 if (x->done != UINT_MAX)
93 x->done--;
94 return timeout ?: 1;
95}
96
97static inline long __sched
98__wait_for_common(struct completion *x,
99 long (*action)(long), long timeout, int state)
100{
101 might_sleep();
102
103 complete_acquire(x);
104
105 raw_spin_lock_irq(&x->wait.lock);
106 timeout = do_wait_for_common(x, action, timeout, state);
107 raw_spin_unlock_irq(&x->wait.lock);
108
109 complete_release(x);
110
111 return timeout;
112}
113
114static long __sched
115wait_for_common(struct completion *x, long timeout, int state)
116{
117 return __wait_for_common(x, schedule_timeout, timeout, state);
118}
119
120static long __sched
121wait_for_common_io(struct completion *x, long timeout, int state)
122{
123 return __wait_for_common(x, io_schedule_timeout, timeout, state);
124}
125
126/**
127 * wait_for_completion: - waits for completion of a task
128 * @x: holds the state of this particular completion
129 *
130 * This waits to be signaled for completion of a specific task. It is NOT
131 * interruptible and there is no timeout.
132 *
133 * See also similar routines (i.e. wait_for_completion_timeout()) with timeout
134 * and interrupt capability. Also see complete().
135 */
136void __sched wait_for_completion(struct completion *x)
137{
138 wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
139}
140EXPORT_SYMBOL(wait_for_completion);
141
142/**
143 * wait_for_completion_timeout: - waits for completion of a task (w/timeout)
144 * @x: holds the state of this particular completion
145 * @timeout: timeout value in jiffies
146 *
147 * This waits for either a completion of a specific task to be signaled or for a
148 * specified timeout to expire. The timeout is in jiffies. It is not
149 * interruptible.
150 *
151 * Return: 0 if timed out, and positive (at least 1, or number of jiffies left
152 * till timeout) if completed.
153 */
154unsigned long __sched
155wait_for_completion_timeout(struct completion *x, unsigned long timeout)
156{
157 return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE);
158}
159EXPORT_SYMBOL(wait_for_completion_timeout);
160
161/**
162 * wait_for_completion_io: - waits for completion of a task
163 * @x: holds the state of this particular completion
164 *
165 * This waits to be signaled for completion of a specific task. It is NOT
166 * interruptible and there is no timeout. The caller is accounted as waiting
167 * for IO (which traditionally means blkio only).
168 */
169void __sched wait_for_completion_io(struct completion *x)
170{
171 wait_for_common_io(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
172}
173EXPORT_SYMBOL(wait_for_completion_io);
174
175/**
176 * wait_for_completion_io_timeout: - waits for completion of a task (w/timeout)
177 * @x: holds the state of this particular completion
178 * @timeout: timeout value in jiffies
179 *
180 * This waits for either a completion of a specific task to be signaled or for a
181 * specified timeout to expire. The timeout is in jiffies. It is not
182 * interruptible. The caller is accounted as waiting for IO (which traditionally
183 * means blkio only).
184 *
185 * Return: 0 if timed out, and positive (at least 1, or number of jiffies left
186 * till timeout) if completed.
187 */
188unsigned long __sched
189wait_for_completion_io_timeout(struct completion *x, unsigned long timeout)
190{
191 return wait_for_common_io(x, timeout, TASK_UNINTERRUPTIBLE);
192}
193EXPORT_SYMBOL(wait_for_completion_io_timeout);
194
195/**
196 * wait_for_completion_interruptible: - waits for completion of a task (w/intr)
197 * @x: holds the state of this particular completion
198 *
199 * This waits for completion of a specific task to be signaled. It is
200 * interruptible.
201 *
202 * Return: -ERESTARTSYS if interrupted, 0 if completed.
203 */
204int __sched wait_for_completion_interruptible(struct completion *x)
205{
206 long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE);
207
208 if (t == -ERESTARTSYS)
209 return t;
210 return 0;
211}
212EXPORT_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 */
225long __sched
226wait_for_completion_interruptible_timeout(struct completion *x,
227 unsigned long timeout)
228{
229 return wait_for_common(x, timeout, TASK_INTERRUPTIBLE);
230}
231EXPORT_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 */
242int __sched wait_for_completion_killable(struct completion *x)
243{
244 long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE);
245
246 if (t == -ERESTARTSYS)
247 return t;
248 return 0;
249}
250EXPORT_SYMBOL(wait_for_completion_killable);
251
252int __sched wait_for_completion_state(struct completion *x, unsigned int state)
253{
254 long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, state);
255
256 if (t == -ERESTARTSYS)
257 return t;
258 return 0;
259}
260EXPORT_SYMBOL(wait_for_completion_state);
261
262/**
263 * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable))
264 * @x: holds the state of this particular completion
265 * @timeout: timeout value in jiffies
266 *
267 * This waits for either a completion of a specific task to be
268 * signaled or for a specified timeout to expire. It can be
269 * interrupted by a kill signal. The timeout is in jiffies.
270 *
271 * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1,
272 * or number of jiffies left till timeout) if completed.
273 */
274long __sched
275wait_for_completion_killable_timeout(struct completion *x,
276 unsigned long timeout)
277{
278 return wait_for_common(x, timeout, TASK_KILLABLE);
279}
280EXPORT_SYMBOL(wait_for_completion_killable_timeout);
281
282/**
283 * try_wait_for_completion - try to decrement a completion without blocking
284 * @x: completion structure
285 *
286 * Return: 0 if a decrement cannot be done without blocking
287 * 1 if a decrement succeeded.
288 *
289 * If a completion is being used as a counting completion,
290 * attempt to decrement the counter without blocking. This
291 * enables us to avoid waiting if the resource the completion
292 * is protecting is not available.
293 */
294bool try_wait_for_completion(struct completion *x)
295{
296 unsigned long flags;
297 bool ret = true;
298
299 /*
300 * Since x->done will need to be locked only
301 * in the non-blocking case, we check x->done
302 * first without taking the lock so we can
303 * return early in the blocking case.
304 */
305 if (!READ_ONCE(x->done))
306 return false;
307
308 raw_spin_lock_irqsave(&x->wait.lock, flags);
309 if (!x->done)
310 ret = false;
311 else if (x->done != UINT_MAX)
312 x->done--;
313 raw_spin_unlock_irqrestore(&x->wait.lock, flags);
314 return ret;
315}
316EXPORT_SYMBOL(try_wait_for_completion);
317
318/**
319 * completion_done - Test to see if a completion has any waiters
320 * @x: completion structure
321 *
322 * Return: 0 if there are waiters (wait_for_completion() in progress)
323 * 1 if there are no waiters.
324 *
325 * Note, this will always return true if complete_all() was called on @X.
326 */
327bool completion_done(struct completion *x)
328{
329 unsigned long flags;
330
331 if (!READ_ONCE(x->done))
332 return false;
333
334 /*
335 * If ->done, we need to wait for complete() to release ->wait.lock
336 * otherwise we can end up freeing the completion before complete()
337 * is done referencing it.
338 */
339 raw_spin_lock_irqsave(&x->wait.lock, flags);
340 raw_spin_unlock_irqrestore(&x->wait.lock, flags);
341 return true;
342}
343EXPORT_SYMBOL(completion_done);
1// SPDX-License-Identifier: GPL-2.0
2
3/*
4 * Generic wait-for-completion handler;
5 *
6 * It differs from semaphores in that their default case is the opposite,
7 * wait_for_completion default blocks whereas semaphore default non-block. The
8 * interface also makes it easy to 'complete' multiple waiting threads,
9 * something which isn't entirely natural for semaphores.
10 *
11 * But more importantly, the primitive documents the usage. Semaphores would
12 * typically be used for exclusion which gives rise to priority inversion.
13 * Waiting for completion is a typically sync point, but not an exclusion point.
14 */
15
16static void complete_with_flags(struct completion *x, int wake_flags)
17{
18 unsigned long flags;
19
20 raw_spin_lock_irqsave(&x->wait.lock, flags);
21
22 if (x->done != UINT_MAX)
23 x->done++;
24 swake_up_locked(&x->wait, wake_flags);
25 raw_spin_unlock_irqrestore(&x->wait.lock, flags);
26}
27
28void complete_on_current_cpu(struct completion *x)
29{
30 return complete_with_flags(x, WF_CURRENT_CPU);
31}
32
33/**
34 * complete: - signals a single thread waiting on this completion
35 * @x: holds the state of this particular completion
36 *
37 * This will wake up a single thread waiting on this completion. Threads will be
38 * awakened in the same order in which they were queued.
39 *
40 * See also complete_all(), wait_for_completion() and related routines.
41 *
42 * If this function wakes up a task, it executes a full memory barrier before
43 * accessing the task state.
44 */
45void complete(struct completion *x)
46{
47 complete_with_flags(x, 0);
48}
49EXPORT_SYMBOL(complete);
50
51/**
52 * complete_all: - signals all threads waiting on this completion
53 * @x: holds the state of this particular completion
54 *
55 * This will wake up all threads waiting on this particular completion event.
56 *
57 * If this function wakes up a task, it executes a full memory barrier before
58 * accessing the task state.
59 *
60 * Since complete_all() sets the completion of @x permanently to done
61 * to allow multiple waiters to finish, a call to reinit_completion()
62 * must be used on @x if @x is to be used again. The code must make
63 * sure that all waiters have woken and finished before reinitializing
64 * @x. Also note that the function completion_done() can not be used
65 * to know if there are still waiters after complete_all() has been called.
66 */
67void complete_all(struct completion *x)
68{
69 unsigned long flags;
70
71 lockdep_assert_RT_in_threaded_ctx();
72
73 raw_spin_lock_irqsave(&x->wait.lock, flags);
74 x->done = UINT_MAX;
75 swake_up_all_locked(&x->wait);
76 raw_spin_unlock_irqrestore(&x->wait.lock, flags);
77}
78EXPORT_SYMBOL(complete_all);
79
80static inline long __sched
81do_wait_for_common(struct completion *x,
82 long (*action)(long), long timeout, int state)
83{
84 if (!x->done) {
85 DECLARE_SWAITQUEUE(wait);
86
87 do {
88 if (signal_pending_state(state, current)) {
89 timeout = -ERESTARTSYS;
90 break;
91 }
92 __prepare_to_swait(&x->wait, &wait);
93 __set_current_state(state);
94 raw_spin_unlock_irq(&x->wait.lock);
95 timeout = action(timeout);
96 raw_spin_lock_irq(&x->wait.lock);
97 } while (!x->done && timeout);
98 __finish_swait(&x->wait, &wait);
99 if (!x->done)
100 return timeout;
101 }
102 if (x->done != UINT_MAX)
103 x->done--;
104 return timeout ?: 1;
105}
106
107static inline long __sched
108__wait_for_common(struct completion *x,
109 long (*action)(long), long timeout, int state)
110{
111 might_sleep();
112
113 complete_acquire(x);
114
115 raw_spin_lock_irq(&x->wait.lock);
116 timeout = do_wait_for_common(x, action, timeout, state);
117 raw_spin_unlock_irq(&x->wait.lock);
118
119 complete_release(x);
120
121 return timeout;
122}
123
124static long __sched
125wait_for_common(struct completion *x, long timeout, int state)
126{
127 return __wait_for_common(x, schedule_timeout, timeout, state);
128}
129
130static long __sched
131wait_for_common_io(struct completion *x, long timeout, int state)
132{
133 return __wait_for_common(x, io_schedule_timeout, timeout, state);
134}
135
136/**
137 * wait_for_completion: - waits for completion of a task
138 * @x: holds the state of this particular completion
139 *
140 * This waits to be signaled for completion of a specific task. It is NOT
141 * interruptible and there is no timeout.
142 *
143 * See also similar routines (i.e. wait_for_completion_timeout()) with timeout
144 * and interrupt capability. Also see complete().
145 */
146void __sched wait_for_completion(struct completion *x)
147{
148 wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
149}
150EXPORT_SYMBOL(wait_for_completion);
151
152/**
153 * wait_for_completion_timeout: - waits for completion of a task (w/timeout)
154 * @x: holds the state of this particular completion
155 * @timeout: timeout value in jiffies
156 *
157 * This waits for either a completion of a specific task to be signaled or for a
158 * specified timeout to expire. The timeout is in jiffies. It is not
159 * interruptible.
160 *
161 * Return: 0 if timed out, and positive (at least 1, or number of jiffies left
162 * till timeout) if completed.
163 */
164unsigned long __sched
165wait_for_completion_timeout(struct completion *x, unsigned long timeout)
166{
167 return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE);
168}
169EXPORT_SYMBOL(wait_for_completion_timeout);
170
171/**
172 * wait_for_completion_io: - waits for completion of a task
173 * @x: holds the state of this particular completion
174 *
175 * This waits to be signaled for completion of a specific task. It is NOT
176 * interruptible and there is no timeout. The caller is accounted as waiting
177 * for IO (which traditionally means blkio only).
178 */
179void __sched wait_for_completion_io(struct completion *x)
180{
181 wait_for_common_io(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
182}
183EXPORT_SYMBOL(wait_for_completion_io);
184
185/**
186 * wait_for_completion_io_timeout: - waits for completion of a task (w/timeout)
187 * @x: holds the state of this particular completion
188 * @timeout: timeout value in jiffies
189 *
190 * This waits for either a completion of a specific task to be signaled or for a
191 * specified timeout to expire. The timeout is in jiffies. It is not
192 * interruptible. The caller is accounted as waiting for IO (which traditionally
193 * means blkio only).
194 *
195 * Return: 0 if timed out, and positive (at least 1, or number of jiffies left
196 * till timeout) if completed.
197 */
198unsigned long __sched
199wait_for_completion_io_timeout(struct completion *x, unsigned long timeout)
200{
201 return wait_for_common_io(x, timeout, TASK_UNINTERRUPTIBLE);
202}
203EXPORT_SYMBOL(wait_for_completion_io_timeout);
204
205/**
206 * wait_for_completion_interruptible: - waits for completion of a task (w/intr)
207 * @x: holds the state of this particular completion
208 *
209 * This waits for completion of a specific task to be signaled. It is
210 * interruptible.
211 *
212 * Return: -ERESTARTSYS if interrupted, 0 if completed.
213 */
214int __sched wait_for_completion_interruptible(struct completion *x)
215{
216 long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE);
217
218 if (t == -ERESTARTSYS)
219 return t;
220 return 0;
221}
222EXPORT_SYMBOL(wait_for_completion_interruptible);
223
224/**
225 * wait_for_completion_interruptible_timeout: - waits for completion (w/(to,intr))
226 * @x: holds the state of this particular completion
227 * @timeout: timeout value in jiffies
228 *
229 * This waits for either a completion of a specific task to be signaled or for a
230 * specified timeout to expire. It is interruptible. The timeout is in jiffies.
231 *
232 * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1,
233 * or number of jiffies left till timeout) if completed.
234 */
235long __sched
236wait_for_completion_interruptible_timeout(struct completion *x,
237 unsigned long timeout)
238{
239 return wait_for_common(x, timeout, TASK_INTERRUPTIBLE);
240}
241EXPORT_SYMBOL(wait_for_completion_interruptible_timeout);
242
243/**
244 * wait_for_completion_killable: - waits for completion of a task (killable)
245 * @x: holds the state of this particular completion
246 *
247 * This waits to be signaled for completion of a specific task. It can be
248 * interrupted by a kill signal.
249 *
250 * Return: -ERESTARTSYS if interrupted, 0 if completed.
251 */
252int __sched wait_for_completion_killable(struct completion *x)
253{
254 long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE);
255
256 if (t == -ERESTARTSYS)
257 return t;
258 return 0;
259}
260EXPORT_SYMBOL(wait_for_completion_killable);
261
262int __sched wait_for_completion_state(struct completion *x, unsigned int state)
263{
264 long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, state);
265
266 if (t == -ERESTARTSYS)
267 return t;
268 return 0;
269}
270EXPORT_SYMBOL(wait_for_completion_state);
271
272/**
273 * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable))
274 * @x: holds the state of this particular completion
275 * @timeout: timeout value in jiffies
276 *
277 * This waits for either a completion of a specific task to be
278 * signaled or for a specified timeout to expire. It can be
279 * interrupted by a kill signal. The timeout is in jiffies.
280 *
281 * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1,
282 * or number of jiffies left till timeout) if completed.
283 */
284long __sched
285wait_for_completion_killable_timeout(struct completion *x,
286 unsigned long timeout)
287{
288 return wait_for_common(x, timeout, TASK_KILLABLE);
289}
290EXPORT_SYMBOL(wait_for_completion_killable_timeout);
291
292/**
293 * try_wait_for_completion - try to decrement a completion without blocking
294 * @x: completion structure
295 *
296 * Return: 0 if a decrement cannot be done without blocking
297 * 1 if a decrement succeeded.
298 *
299 * If a completion is being used as a counting completion,
300 * attempt to decrement the counter without blocking. This
301 * enables us to avoid waiting if the resource the completion
302 * is protecting is not available.
303 */
304bool try_wait_for_completion(struct completion *x)
305{
306 unsigned long flags;
307 bool ret = true;
308
309 /*
310 * Since x->done will need to be locked only
311 * in the non-blocking case, we check x->done
312 * first without taking the lock so we can
313 * return early in the blocking case.
314 */
315 if (!READ_ONCE(x->done))
316 return false;
317
318 raw_spin_lock_irqsave(&x->wait.lock, flags);
319 if (!x->done)
320 ret = false;
321 else if (x->done != UINT_MAX)
322 x->done--;
323 raw_spin_unlock_irqrestore(&x->wait.lock, flags);
324 return ret;
325}
326EXPORT_SYMBOL(try_wait_for_completion);
327
328/**
329 * completion_done - Test to see if a completion has any waiters
330 * @x: completion structure
331 *
332 * Return: 0 if there are waiters (wait_for_completion() in progress)
333 * 1 if there are no waiters.
334 *
335 * Note, this will always return true if complete_all() was called on @X.
336 */
337bool completion_done(struct completion *x)
338{
339 unsigned long flags;
340
341 if (!READ_ONCE(x->done))
342 return false;
343
344 /*
345 * If ->done, we need to wait for complete() to release ->wait.lock
346 * otherwise we can end up freeing the completion before complete()
347 * is done referencing it.
348 */
349 raw_spin_lock_irqsave(&x->wait.lock, flags);
350 raw_spin_unlock_irqrestore(&x->wait.lock, flags);
351 return true;
352}
353EXPORT_SYMBOL(completion_done);