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