1 // SPDX-License-Identifier: GPL-2.0 1 // SPDX-License-Identifier: GPL-2.0
2 2
3 /* 3 /*
4 * Generic wait-for-completion handler; 4 * Generic wait-for-completion handler;
5 * 5 *
6 * It differs from semaphores in that their de 6 * It differs from semaphores in that their default case is the opposite,
7 * wait_for_completion default blocks whereas 7 * wait_for_completion default blocks whereas semaphore default non-block. The
8 * interface also makes it easy to 'complete' 8 * interface also makes it easy to 'complete' multiple waiting threads,
9 * something which isn't entirely natural for 9 * something which isn't entirely natural for semaphores.
10 * 10 *
11 * But more importantly, the primitive documen 11 * But more importantly, the primitive documents the usage. Semaphores would
12 * typically be used for exclusion which gives 12 * typically be used for exclusion which gives rise to priority inversion.
13 * Waiting for completion is a typically sync 13 * Waiting for completion is a typically sync point, but not an exclusion point.
14 */ 14 */
15 15
16 static void complete_with_flags(struct complet <<
17 { <<
18 unsigned long flags; <<
19 <<
20 raw_spin_lock_irqsave(&x->wait.lock, f <<
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.lo <<
26 } <<
27 <<
28 void complete_on_current_cpu(struct completion <<
29 { <<
30 return complete_with_flags(x, WF_CURRE <<
31 } <<
32 <<
33 /** 16 /**
34 * complete: - signals a single thread waiting 17 * complete: - signals a single thread waiting on this completion
35 * @x: holds the state of this particular com 18 * @x: holds the state of this particular completion
36 * 19 *
37 * This will wake up a single thread waiting o 20 * This will wake up a single thread waiting on this completion. Threads will be
38 * awakened in the same order in which they we 21 * awakened in the same order in which they were queued.
39 * 22 *
40 * See also complete_all(), wait_for_completio 23 * See also complete_all(), wait_for_completion() and related routines.
41 * 24 *
42 * If this function wakes up a task, it execut 25 * If this function wakes up a task, it executes a full memory barrier before
43 * accessing the task state. 26 * accessing the task state.
44 */ 27 */
45 void complete(struct completion *x) 28 void complete(struct completion *x)
46 { 29 {
47 complete_with_flags(x, 0); !! 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);
48 } 38 }
49 EXPORT_SYMBOL(complete); 39 EXPORT_SYMBOL(complete);
50 40
51 /** 41 /**
52 * complete_all: - signals all threads waiting 42 * complete_all: - signals all threads waiting on this completion
53 * @x: holds the state of this particular com 43 * @x: holds the state of this particular completion
54 * 44 *
55 * This will wake up all threads waiting on th 45 * This will wake up all threads waiting on this particular completion event.
56 * 46 *
57 * If this function wakes up a task, it execut 47 * If this function wakes up a task, it executes a full memory barrier before
58 * accessing the task state. 48 * accessing the task state.
59 * 49 *
60 * Since complete_all() sets the completion of 50 * Since complete_all() sets the completion of @x permanently to done
61 * to allow multiple waiters to finish, a call 51 * to allow multiple waiters to finish, a call to reinit_completion()
62 * must be used on @x if @x is to be used agai 52 * must be used on @x if @x is to be used again. The code must make
63 * sure that all waiters have woken and finish 53 * sure that all waiters have woken and finished before reinitializing
64 * @x. Also note that the function completion_ 54 * @x. Also note that the function completion_done() can not be used
65 * to know if there are still waiters after co 55 * to know if there are still waiters after complete_all() has been called.
66 */ 56 */
67 void complete_all(struct completion *x) 57 void complete_all(struct completion *x)
68 { 58 {
69 unsigned long flags; 59 unsigned long flags;
70 60
71 lockdep_assert_RT_in_threaded_ctx(); 61 lockdep_assert_RT_in_threaded_ctx();
72 62
73 raw_spin_lock_irqsave(&x->wait.lock, f 63 raw_spin_lock_irqsave(&x->wait.lock, flags);
74 x->done = UINT_MAX; 64 x->done = UINT_MAX;
75 swake_up_all_locked(&x->wait); 65 swake_up_all_locked(&x->wait);
76 raw_spin_unlock_irqrestore(&x->wait.lo 66 raw_spin_unlock_irqrestore(&x->wait.lock, flags);
77 } 67 }
78 EXPORT_SYMBOL(complete_all); 68 EXPORT_SYMBOL(complete_all);
79 69
80 static inline long __sched 70 static inline long __sched
81 do_wait_for_common(struct completion *x, 71 do_wait_for_common(struct completion *x,
82 long (*action)(long), long 72 long (*action)(long), long timeout, int state)
83 { 73 {
84 if (!x->done) { 74 if (!x->done) {
85 DECLARE_SWAITQUEUE(wait); 75 DECLARE_SWAITQUEUE(wait);
86 76
87 do { 77 do {
88 if (signal_pending_sta 78 if (signal_pending_state(state, current)) {
89 timeout = -ERE 79 timeout = -ERESTARTSYS;
90 break; 80 break;
91 } 81 }
92 __prepare_to_swait(&x- 82 __prepare_to_swait(&x->wait, &wait);
93 __set_current_state(st 83 __set_current_state(state);
94 raw_spin_unlock_irq(&x 84 raw_spin_unlock_irq(&x->wait.lock);
95 timeout = action(timeo 85 timeout = action(timeout);
96 raw_spin_lock_irq(&x-> 86 raw_spin_lock_irq(&x->wait.lock);
97 } while (!x->done && timeout); 87 } while (!x->done && timeout);
98 __finish_swait(&x->wait, &wait 88 __finish_swait(&x->wait, &wait);
99 if (!x->done) 89 if (!x->done)
100 return timeout; 90 return timeout;
101 } 91 }
102 if (x->done != UINT_MAX) 92 if (x->done != UINT_MAX)
103 x->done--; 93 x->done--;
104 return timeout ?: 1; 94 return timeout ?: 1;
105 } 95 }
106 96
107 static inline long __sched 97 static inline long __sched
108 __wait_for_common(struct completion *x, 98 __wait_for_common(struct completion *x,
109 long (*action)(long), long t 99 long (*action)(long), long timeout, int state)
110 { 100 {
111 might_sleep(); 101 might_sleep();
112 102
113 complete_acquire(x); 103 complete_acquire(x);
114 104
115 raw_spin_lock_irq(&x->wait.lock); 105 raw_spin_lock_irq(&x->wait.lock);
116 timeout = do_wait_for_common(x, action 106 timeout = do_wait_for_common(x, action, timeout, state);
117 raw_spin_unlock_irq(&x->wait.lock); 107 raw_spin_unlock_irq(&x->wait.lock);
118 108
119 complete_release(x); 109 complete_release(x);
120 110
121 return timeout; 111 return timeout;
122 } 112 }
123 113
124 static long __sched 114 static long __sched
125 wait_for_common(struct completion *x, long tim 115 wait_for_common(struct completion *x, long timeout, int state)
126 { 116 {
127 return __wait_for_common(x, schedule_t 117 return __wait_for_common(x, schedule_timeout, timeout, state);
128 } 118 }
129 119
130 static long __sched 120 static long __sched
131 wait_for_common_io(struct completion *x, long 121 wait_for_common_io(struct completion *x, long timeout, int state)
132 { 122 {
133 return __wait_for_common(x, io_schedul 123 return __wait_for_common(x, io_schedule_timeout, timeout, state);
134 } 124 }
135 125
136 /** 126 /**
137 * wait_for_completion: - waits for completion 127 * wait_for_completion: - waits for completion of a task
138 * @x: holds the state of this particular com 128 * @x: holds the state of this particular completion
139 * 129 *
140 * This waits to be signaled for completion of 130 * This waits to be signaled for completion of a specific task. It is NOT
141 * interruptible and there is no timeout. 131 * interruptible and there is no timeout.
142 * 132 *
143 * See also similar routines (i.e. wait_for_co 133 * See also similar routines (i.e. wait_for_completion_timeout()) with timeout
144 * and interrupt capability. Also see complete 134 * and interrupt capability. Also see complete().
145 */ 135 */
146 void __sched wait_for_completion(struct comple 136 void __sched wait_for_completion(struct completion *x)
147 { 137 {
148 wait_for_common(x, MAX_SCHEDULE_TIMEOU 138 wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
149 } 139 }
150 EXPORT_SYMBOL(wait_for_completion); 140 EXPORT_SYMBOL(wait_for_completion);
151 141
152 /** 142 /**
153 * wait_for_completion_timeout: - waits for co 143 * wait_for_completion_timeout: - waits for completion of a task (w/timeout)
154 * @x: holds the state of this particular com 144 * @x: holds the state of this particular completion
155 * @timeout: timeout value in jiffies 145 * @timeout: timeout value in jiffies
156 * 146 *
157 * This waits for either a completion of a spe 147 * This waits for either a completion of a specific task to be signaled or for a
158 * specified timeout to expire. The timeout is 148 * specified timeout to expire. The timeout is in jiffies. It is not
159 * interruptible. 149 * interruptible.
160 * 150 *
161 * Return: 0 if timed out, and positive (at le 151 * Return: 0 if timed out, and positive (at least 1, or number of jiffies left
162 * till timeout) if completed. 152 * till timeout) if completed.
163 */ 153 */
164 unsigned long __sched 154 unsigned long __sched
165 wait_for_completion_timeout(struct completion 155 wait_for_completion_timeout(struct completion *x, unsigned long timeout)
166 { 156 {
167 return wait_for_common(x, timeout, TAS 157 return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE);
168 } 158 }
169 EXPORT_SYMBOL(wait_for_completion_timeout); 159 EXPORT_SYMBOL(wait_for_completion_timeout);
170 160
171 /** 161 /**
172 * wait_for_completion_io: - waits for complet 162 * wait_for_completion_io: - waits for completion of a task
173 * @x: holds the state of this particular com 163 * @x: holds the state of this particular completion
174 * 164 *
175 * This waits to be signaled for completion of 165 * This waits to be signaled for completion of a specific task. It is NOT
176 * interruptible and there is no timeout. The 166 * interruptible and there is no timeout. The caller is accounted as waiting
177 * for IO (which traditionally means blkio onl 167 * for IO (which traditionally means blkio only).
178 */ 168 */
179 void __sched wait_for_completion_io(struct com 169 void __sched wait_for_completion_io(struct completion *x)
180 { 170 {
181 wait_for_common_io(x, MAX_SCHEDULE_TIM 171 wait_for_common_io(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
182 } 172 }
183 EXPORT_SYMBOL(wait_for_completion_io); 173 EXPORT_SYMBOL(wait_for_completion_io);
184 174
185 /** 175 /**
186 * wait_for_completion_io_timeout: - waits for 176 * wait_for_completion_io_timeout: - waits for completion of a task (w/timeout)
187 * @x: holds the state of this particular com 177 * @x: holds the state of this particular completion
188 * @timeout: timeout value in jiffies 178 * @timeout: timeout value in jiffies
189 * 179 *
190 * This waits for either a completion of a spe 180 * This waits for either a completion of a specific task to be signaled or for a
191 * specified timeout to expire. The timeout is 181 * specified timeout to expire. The timeout is in jiffies. It is not
192 * interruptible. The caller is accounted as w 182 * interruptible. The caller is accounted as waiting for IO (which traditionally
193 * means blkio only). 183 * means blkio only).
194 * 184 *
195 * Return: 0 if timed out, and positive (at le 185 * Return: 0 if timed out, and positive (at least 1, or number of jiffies left
196 * till timeout) if completed. 186 * till timeout) if completed.
197 */ 187 */
198 unsigned long __sched 188 unsigned long __sched
199 wait_for_completion_io_timeout(struct completi 189 wait_for_completion_io_timeout(struct completion *x, unsigned long timeout)
200 { 190 {
201 return wait_for_common_io(x, timeout, 191 return wait_for_common_io(x, timeout, TASK_UNINTERRUPTIBLE);
202 } 192 }
203 EXPORT_SYMBOL(wait_for_completion_io_timeout); 193 EXPORT_SYMBOL(wait_for_completion_io_timeout);
204 194
205 /** 195 /**
206 * wait_for_completion_interruptible: - waits 196 * wait_for_completion_interruptible: - waits for completion of a task (w/intr)
207 * @x: holds the state of this particular com 197 * @x: holds the state of this particular completion
208 * 198 *
209 * This waits for completion of a specific tas 199 * This waits for completion of a specific task to be signaled. It is
210 * interruptible. 200 * interruptible.
211 * 201 *
212 * Return: -ERESTARTSYS if interrupted, 0 if c 202 * Return: -ERESTARTSYS if interrupted, 0 if completed.
213 */ 203 */
214 int __sched wait_for_completion_interruptible( 204 int __sched wait_for_completion_interruptible(struct completion *x)
215 { 205 {
216 long t = wait_for_common(x, MAX_SCHEDU 206 long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE);
217 207
218 if (t == -ERESTARTSYS) 208 if (t == -ERESTARTSYS)
219 return t; 209 return t;
220 return 0; 210 return 0;
221 } 211 }
222 EXPORT_SYMBOL(wait_for_completion_interruptibl 212 EXPORT_SYMBOL(wait_for_completion_interruptible);
223 213
224 /** 214 /**
225 * wait_for_completion_interruptible_timeout: 215 * wait_for_completion_interruptible_timeout: - waits for completion (w/(to,intr))
226 * @x: holds the state of this particular com 216 * @x: holds the state of this particular completion
227 * @timeout: timeout value in jiffies 217 * @timeout: timeout value in jiffies
228 * 218 *
229 * This waits for either a completion of a spe 219 * This waits for either a completion of a specific task to be signaled or for a
230 * specified timeout to expire. It is interrup 220 * specified timeout to expire. It is interruptible. The timeout is in jiffies.
231 * 221 *
232 * Return: -ERESTARTSYS if interrupted, 0 if t 222 * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1,
233 * or number of jiffies left till timeout) if 223 * or number of jiffies left till timeout) if completed.
234 */ 224 */
235 long __sched 225 long __sched
236 wait_for_completion_interruptible_timeout(stru 226 wait_for_completion_interruptible_timeout(struct completion *x,
237 unsi 227 unsigned long timeout)
238 { 228 {
239 return wait_for_common(x, timeout, TAS 229 return wait_for_common(x, timeout, TASK_INTERRUPTIBLE);
240 } 230 }
241 EXPORT_SYMBOL(wait_for_completion_interruptibl 231 EXPORT_SYMBOL(wait_for_completion_interruptible_timeout);
242 232
243 /** 233 /**
244 * wait_for_completion_killable: - waits for c 234 * wait_for_completion_killable: - waits for completion of a task (killable)
245 * @x: holds the state of this particular com 235 * @x: holds the state of this particular completion
246 * 236 *
247 * This waits to be signaled for completion of 237 * This waits to be signaled for completion of a specific task. It can be
248 * interrupted by a kill signal. 238 * interrupted by a kill signal.
249 * 239 *
250 * Return: -ERESTARTSYS if interrupted, 0 if c 240 * Return: -ERESTARTSYS if interrupted, 0 if completed.
251 */ 241 */
252 int __sched wait_for_completion_killable(struc 242 int __sched wait_for_completion_killable(struct completion *x)
253 { 243 {
254 long t = wait_for_common(x, MAX_SCHEDU 244 long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE);
255 245
256 if (t == -ERESTARTSYS) 246 if (t == -ERESTARTSYS)
257 return t; 247 return t;
258 return 0; 248 return 0;
259 } 249 }
260 EXPORT_SYMBOL(wait_for_completion_killable); 250 EXPORT_SYMBOL(wait_for_completion_killable);
261 251
262 int __sched wait_for_completion_state(struct c 252 int __sched wait_for_completion_state(struct completion *x, unsigned int state)
263 { 253 {
264 long t = wait_for_common(x, MAX_SCHEDU 254 long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, state);
265 255
266 if (t == -ERESTARTSYS) 256 if (t == -ERESTARTSYS)
267 return t; 257 return t;
268 return 0; 258 return 0;
269 } 259 }
270 EXPORT_SYMBOL(wait_for_completion_state); 260 EXPORT_SYMBOL(wait_for_completion_state);
271 261
272 /** 262 /**
273 * wait_for_completion_killable_timeout: - wai 263 * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable))
274 * @x: holds the state of this particular com 264 * @x: holds the state of this particular completion
275 * @timeout: timeout value in jiffies 265 * @timeout: timeout value in jiffies
276 * 266 *
277 * This waits for either a completion of a spe 267 * This waits for either a completion of a specific task to be
278 * signaled or for a specified timeout to expi 268 * signaled or for a specified timeout to expire. It can be
279 * interrupted by a kill signal. The timeout i 269 * interrupted by a kill signal. The timeout is in jiffies.
280 * 270 *
281 * Return: -ERESTARTSYS if interrupted, 0 if t 271 * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1,
282 * or number of jiffies left till timeout) if 272 * or number of jiffies left till timeout) if completed.
283 */ 273 */
284 long __sched 274 long __sched
285 wait_for_completion_killable_timeout(struct co 275 wait_for_completion_killable_timeout(struct completion *x,
286 unsigned 276 unsigned long timeout)
287 { 277 {
288 return wait_for_common(x, timeout, TAS 278 return wait_for_common(x, timeout, TASK_KILLABLE);
289 } 279 }
290 EXPORT_SYMBOL(wait_for_completion_killable_tim 280 EXPORT_SYMBOL(wait_for_completion_killable_timeout);
291 281
292 /** 282 /**
293 * try_wait_for_completion - try to decre 283 * try_wait_for_completion - try to decrement a completion without blocking
294 * @x: completion structure 284 * @x: completion structure
295 * 285 *
296 * Return: 0 if a decrement cannot be don 286 * Return: 0 if a decrement cannot be done without blocking
297 * 1 if a decrement succeeded. 287 * 1 if a decrement succeeded.
298 * 288 *
299 * If a completion is being used as a cou 289 * If a completion is being used as a counting completion,
300 * attempt to decrement the counter witho 290 * attempt to decrement the counter without blocking. This
301 * enables us to avoid waiting if the res 291 * enables us to avoid waiting if the resource the completion
302 * is protecting is not available. 292 * is protecting is not available.
303 */ 293 */
304 bool try_wait_for_completion(struct completion 294 bool try_wait_for_completion(struct completion *x)
305 { 295 {
306 unsigned long flags; 296 unsigned long flags;
307 bool ret = true; 297 bool ret = true;
308 298
309 /* 299 /*
310 * Since x->done will need to be locke 300 * Since x->done will need to be locked only
311 * in the non-blocking case, we check 301 * in the non-blocking case, we check x->done
312 * first without taking the lock so we 302 * first without taking the lock so we can
313 * return early in the blocking case. 303 * return early in the blocking case.
314 */ 304 */
315 if (!READ_ONCE(x->done)) 305 if (!READ_ONCE(x->done))
316 return false; 306 return false;
317 307
318 raw_spin_lock_irqsave(&x->wait.lock, f 308 raw_spin_lock_irqsave(&x->wait.lock, flags);
319 if (!x->done) 309 if (!x->done)
320 ret = false; 310 ret = false;
321 else if (x->done != UINT_MAX) 311 else if (x->done != UINT_MAX)
322 x->done--; 312 x->done--;
323 raw_spin_unlock_irqrestore(&x->wait.lo 313 raw_spin_unlock_irqrestore(&x->wait.lock, flags);
324 return ret; 314 return ret;
325 } 315 }
326 EXPORT_SYMBOL(try_wait_for_completion); 316 EXPORT_SYMBOL(try_wait_for_completion);
327 317
328 /** 318 /**
329 * completion_done - Test to see if a com 319 * completion_done - Test to see if a completion has any waiters
330 * @x: completion structure 320 * @x: completion structure
331 * 321 *
332 * Return: 0 if there are waiters (wait_f 322 * Return: 0 if there are waiters (wait_for_completion() in progress)
333 * 1 if there are no waiters. 323 * 1 if there are no waiters.
334 * 324 *
335 * Note, this will always return true if 325 * Note, this will always return true if complete_all() was called on @X.
336 */ 326 */
337 bool completion_done(struct completion *x) 327 bool completion_done(struct completion *x)
338 { 328 {
339 unsigned long flags; 329 unsigned long flags;
340 330
341 if (!READ_ONCE(x->done)) 331 if (!READ_ONCE(x->done))
342 return false; 332 return false;
343 333
344 /* 334 /*
345 * If ->done, we need to wait for comp 335 * If ->done, we need to wait for complete() to release ->wait.lock
346 * otherwise we can end up freeing the 336 * otherwise we can end up freeing the completion before complete()
347 * is done referencing it. 337 * is done referencing it.
348 */ 338 */
349 raw_spin_lock_irqsave(&x->wait.lock, f 339 raw_spin_lock_irqsave(&x->wait.lock, flags);
350 raw_spin_unlock_irqrestore(&x->wait.lo 340 raw_spin_unlock_irqrestore(&x->wait.lock, flags);
351 return true; 341 return true;
352 } 342 }
353 EXPORT_SYMBOL(completion_done); 343 EXPORT_SYMBOL(completion_done);
354 344
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