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 #include "sched.h"
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 15
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 * It may be assumed that this function implies a write memory barrier before
43 * accessing the task state. !! 26 * changing the task state if and only if any tasks are woken up.
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 spin_lock_irqsave(&x->wait.lock, flags);
>> 33
>> 34 if (x->done != UINT_MAX)
>> 35 x->done++;
>> 36 __wake_up_locked(&x->wait, TASK_NORMAL, 1);
>> 37 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 * It may be assumed that this function implies a write memory barrier before
58 * accessing the task state. !! 48 * changing the task state if and only if any tasks are woken up.
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 spin_lock_irqsave(&x->wait.lock, flags);
72 <<
73 raw_spin_lock_irqsave(&x->wait.lock, f <<
74 x->done = UINT_MAX; 62 x->done = UINT_MAX;
75 swake_up_all_locked(&x->wait); !! 63 __wake_up_locked(&x->wait, TASK_NORMAL, 0);
76 raw_spin_unlock_irqrestore(&x->wait.lo !! 64 spin_unlock_irqrestore(&x->wait.lock, flags);
77 } 65 }
78 EXPORT_SYMBOL(complete_all); 66 EXPORT_SYMBOL(complete_all);
79 67
80 static inline long __sched 68 static inline long __sched
81 do_wait_for_common(struct completion *x, 69 do_wait_for_common(struct completion *x,
82 long (*action)(long), long 70 long (*action)(long), long timeout, int state)
83 { 71 {
84 if (!x->done) { 72 if (!x->done) {
85 DECLARE_SWAITQUEUE(wait); !! 73 DECLARE_WAITQUEUE(wait, current);
86 74
>> 75 __add_wait_queue_entry_tail_exclusive(&x->wait, &wait);
87 do { 76 do {
88 if (signal_pending_sta 77 if (signal_pending_state(state, current)) {
89 timeout = -ERE 78 timeout = -ERESTARTSYS;
90 break; 79 break;
91 } 80 }
92 __prepare_to_swait(&x- <<
93 __set_current_state(st 81 __set_current_state(state);
94 raw_spin_unlock_irq(&x !! 82 spin_unlock_irq(&x->wait.lock);
95 timeout = action(timeo 83 timeout = action(timeout);
96 raw_spin_lock_irq(&x-> !! 84 spin_lock_irq(&x->wait.lock);
97 } while (!x->done && timeout); 85 } while (!x->done && timeout);
98 __finish_swait(&x->wait, &wait !! 86 __remove_wait_queue(&x->wait, &wait);
99 if (!x->done) 87 if (!x->done)
100 return timeout; 88 return timeout;
101 } 89 }
102 if (x->done != UINT_MAX) 90 if (x->done != UINT_MAX)
103 x->done--; 91 x->done--;
104 return timeout ?: 1; 92 return timeout ?: 1;
105 } 93 }
106 94
107 static inline long __sched 95 static inline long __sched
108 __wait_for_common(struct completion *x, 96 __wait_for_common(struct completion *x,
109 long (*action)(long), long t 97 long (*action)(long), long timeout, int state)
110 { 98 {
111 might_sleep(); 99 might_sleep();
112 100
113 complete_acquire(x); 101 complete_acquire(x);
114 102
115 raw_spin_lock_irq(&x->wait.lock); !! 103 spin_lock_irq(&x->wait.lock);
116 timeout = do_wait_for_common(x, action 104 timeout = do_wait_for_common(x, action, timeout, state);
117 raw_spin_unlock_irq(&x->wait.lock); !! 105 spin_unlock_irq(&x->wait.lock);
118 106
119 complete_release(x); 107 complete_release(x);
120 108
121 return timeout; 109 return timeout;
122 } 110 }
123 111
124 static long __sched 112 static long __sched
125 wait_for_common(struct completion *x, long tim 113 wait_for_common(struct completion *x, long timeout, int state)
126 { 114 {
127 return __wait_for_common(x, schedule_t 115 return __wait_for_common(x, schedule_timeout, timeout, state);
128 } 116 }
129 117
130 static long __sched 118 static long __sched
131 wait_for_common_io(struct completion *x, long 119 wait_for_common_io(struct completion *x, long timeout, int state)
132 { 120 {
133 return __wait_for_common(x, io_schedul 121 return __wait_for_common(x, io_schedule_timeout, timeout, state);
134 } 122 }
135 123
136 /** 124 /**
137 * wait_for_completion: - waits for completion 125 * wait_for_completion: - waits for completion of a task
138 * @x: holds the state of this particular com 126 * @x: holds the state of this particular completion
139 * 127 *
140 * This waits to be signaled for completion of 128 * This waits to be signaled for completion of a specific task. It is NOT
141 * interruptible and there is no timeout. 129 * interruptible and there is no timeout.
142 * 130 *
143 * See also similar routines (i.e. wait_for_co 131 * See also similar routines (i.e. wait_for_completion_timeout()) with timeout
144 * and interrupt capability. Also see complete 132 * and interrupt capability. Also see complete().
145 */ 133 */
146 void __sched wait_for_completion(struct comple 134 void __sched wait_for_completion(struct completion *x)
147 { 135 {
148 wait_for_common(x, MAX_SCHEDULE_TIMEOU 136 wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
149 } 137 }
150 EXPORT_SYMBOL(wait_for_completion); 138 EXPORT_SYMBOL(wait_for_completion);
151 139
152 /** 140 /**
153 * wait_for_completion_timeout: - waits for co 141 * wait_for_completion_timeout: - waits for completion of a task (w/timeout)
154 * @x: holds the state of this particular com 142 * @x: holds the state of this particular completion
155 * @timeout: timeout value in jiffies 143 * @timeout: timeout value in jiffies
156 * 144 *
157 * This waits for either a completion of a spe 145 * This waits for either a completion of a specific task to be signaled or for a
158 * specified timeout to expire. The timeout is 146 * specified timeout to expire. The timeout is in jiffies. It is not
159 * interruptible. 147 * interruptible.
160 * 148 *
161 * Return: 0 if timed out, and positive (at le 149 * Return: 0 if timed out, and positive (at least 1, or number of jiffies left
162 * till timeout) if completed. 150 * till timeout) if completed.
163 */ 151 */
164 unsigned long __sched 152 unsigned long __sched
165 wait_for_completion_timeout(struct completion 153 wait_for_completion_timeout(struct completion *x, unsigned long timeout)
166 { 154 {
167 return wait_for_common(x, timeout, TAS 155 return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE);
168 } 156 }
169 EXPORT_SYMBOL(wait_for_completion_timeout); 157 EXPORT_SYMBOL(wait_for_completion_timeout);
170 158
171 /** 159 /**
172 * wait_for_completion_io: - waits for complet 160 * wait_for_completion_io: - waits for completion of a task
173 * @x: holds the state of this particular com 161 * @x: holds the state of this particular completion
174 * 162 *
175 * This waits to be signaled for completion of 163 * This waits to be signaled for completion of a specific task. It is NOT
176 * interruptible and there is no timeout. The 164 * interruptible and there is no timeout. The caller is accounted as waiting
177 * for IO (which traditionally means blkio onl 165 * for IO (which traditionally means blkio only).
178 */ 166 */
179 void __sched wait_for_completion_io(struct com 167 void __sched wait_for_completion_io(struct completion *x)
180 { 168 {
181 wait_for_common_io(x, MAX_SCHEDULE_TIM 169 wait_for_common_io(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
182 } 170 }
183 EXPORT_SYMBOL(wait_for_completion_io); 171 EXPORT_SYMBOL(wait_for_completion_io);
184 172
185 /** 173 /**
186 * wait_for_completion_io_timeout: - waits for 174 * wait_for_completion_io_timeout: - waits for completion of a task (w/timeout)
187 * @x: holds the state of this particular com 175 * @x: holds the state of this particular completion
188 * @timeout: timeout value in jiffies 176 * @timeout: timeout value in jiffies
189 * 177 *
190 * This waits for either a completion of a spe 178 * This waits for either a completion of a specific task to be signaled or for a
191 * specified timeout to expire. The timeout is 179 * specified timeout to expire. The timeout is in jiffies. It is not
192 * interruptible. The caller is accounted as w 180 * interruptible. The caller is accounted as waiting for IO (which traditionally
193 * means blkio only). 181 * means blkio only).
194 * 182 *
195 * Return: 0 if timed out, and positive (at le 183 * Return: 0 if timed out, and positive (at least 1, or number of jiffies left
196 * till timeout) if completed. 184 * till timeout) if completed.
197 */ 185 */
198 unsigned long __sched 186 unsigned long __sched
199 wait_for_completion_io_timeout(struct completi 187 wait_for_completion_io_timeout(struct completion *x, unsigned long timeout)
200 { 188 {
201 return wait_for_common_io(x, timeout, 189 return wait_for_common_io(x, timeout, TASK_UNINTERRUPTIBLE);
202 } 190 }
203 EXPORT_SYMBOL(wait_for_completion_io_timeout); 191 EXPORT_SYMBOL(wait_for_completion_io_timeout);
204 192
205 /** 193 /**
206 * wait_for_completion_interruptible: - waits 194 * wait_for_completion_interruptible: - waits for completion of a task (w/intr)
207 * @x: holds the state of this particular com 195 * @x: holds the state of this particular completion
208 * 196 *
209 * This waits for completion of a specific tas 197 * This waits for completion of a specific task to be signaled. It is
210 * interruptible. 198 * interruptible.
211 * 199 *
212 * Return: -ERESTARTSYS if interrupted, 0 if c 200 * Return: -ERESTARTSYS if interrupted, 0 if completed.
213 */ 201 */
214 int __sched wait_for_completion_interruptible( 202 int __sched wait_for_completion_interruptible(struct completion *x)
215 { 203 {
216 long t = wait_for_common(x, MAX_SCHEDU 204 long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE);
217 <<
218 if (t == -ERESTARTSYS) 205 if (t == -ERESTARTSYS)
219 return t; 206 return t;
220 return 0; 207 return 0;
221 } 208 }
222 EXPORT_SYMBOL(wait_for_completion_interruptibl 209 EXPORT_SYMBOL(wait_for_completion_interruptible);
223 210
224 /** 211 /**
225 * wait_for_completion_interruptible_timeout: 212 * wait_for_completion_interruptible_timeout: - waits for completion (w/(to,intr))
226 * @x: holds the state of this particular com 213 * @x: holds the state of this particular completion
227 * @timeout: timeout value in jiffies 214 * @timeout: timeout value in jiffies
228 * 215 *
229 * This waits for either a completion of a spe 216 * This waits for either a completion of a specific task to be signaled or for a
230 * specified timeout to expire. It is interrup 217 * specified timeout to expire. It is interruptible. The timeout is in jiffies.
231 * 218 *
232 * Return: -ERESTARTSYS if interrupted, 0 if t 219 * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1,
233 * or number of jiffies left till timeout) if 220 * or number of jiffies left till timeout) if completed.
234 */ 221 */
235 long __sched 222 long __sched
236 wait_for_completion_interruptible_timeout(stru 223 wait_for_completion_interruptible_timeout(struct completion *x,
237 unsi 224 unsigned long timeout)
238 { 225 {
239 return wait_for_common(x, timeout, TAS 226 return wait_for_common(x, timeout, TASK_INTERRUPTIBLE);
240 } 227 }
241 EXPORT_SYMBOL(wait_for_completion_interruptibl 228 EXPORT_SYMBOL(wait_for_completion_interruptible_timeout);
242 229
243 /** 230 /**
244 * wait_for_completion_killable: - waits for c 231 * wait_for_completion_killable: - waits for completion of a task (killable)
245 * @x: holds the state of this particular com 232 * @x: holds the state of this particular completion
246 * 233 *
247 * This waits to be signaled for completion of 234 * This waits to be signaled for completion of a specific task. It can be
248 * interrupted by a kill signal. 235 * interrupted by a kill signal.
249 * 236 *
250 * Return: -ERESTARTSYS if interrupted, 0 if c 237 * Return: -ERESTARTSYS if interrupted, 0 if completed.
251 */ 238 */
252 int __sched wait_for_completion_killable(struc 239 int __sched wait_for_completion_killable(struct completion *x)
253 { 240 {
254 long t = wait_for_common(x, MAX_SCHEDU 241 long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE);
255 <<
256 if (t == -ERESTARTSYS) 242 if (t == -ERESTARTSYS)
257 return t; 243 return t;
258 return 0; 244 return 0;
259 } 245 }
260 EXPORT_SYMBOL(wait_for_completion_killable); 246 EXPORT_SYMBOL(wait_for_completion_killable);
261 247
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 /** 248 /**
273 * wait_for_completion_killable_timeout: - wai 249 * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable))
274 * @x: holds the state of this particular com 250 * @x: holds the state of this particular completion
275 * @timeout: timeout value in jiffies 251 * @timeout: timeout value in jiffies
276 * 252 *
277 * This waits for either a completion of a spe 253 * This waits for either a completion of a specific task to be
278 * signaled or for a specified timeout to expi 254 * signaled or for a specified timeout to expire. It can be
279 * interrupted by a kill signal. The timeout i 255 * interrupted by a kill signal. The timeout is in jiffies.
280 * 256 *
281 * Return: -ERESTARTSYS if interrupted, 0 if t 257 * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1,
282 * or number of jiffies left till timeout) if 258 * or number of jiffies left till timeout) if completed.
283 */ 259 */
284 long __sched 260 long __sched
285 wait_for_completion_killable_timeout(struct co 261 wait_for_completion_killable_timeout(struct completion *x,
286 unsigned 262 unsigned long timeout)
287 { 263 {
288 return wait_for_common(x, timeout, TAS 264 return wait_for_common(x, timeout, TASK_KILLABLE);
289 } 265 }
290 EXPORT_SYMBOL(wait_for_completion_killable_tim 266 EXPORT_SYMBOL(wait_for_completion_killable_timeout);
291 267
292 /** 268 /**
293 * try_wait_for_completion - try to decre 269 * try_wait_for_completion - try to decrement a completion without blocking
294 * @x: completion structure 270 * @x: completion structure
295 * 271 *
296 * Return: 0 if a decrement cannot be don 272 * Return: 0 if a decrement cannot be done without blocking
297 * 1 if a decrement succeeded. 273 * 1 if a decrement succeeded.
298 * 274 *
299 * If a completion is being used as a cou 275 * If a completion is being used as a counting completion,
300 * attempt to decrement the counter witho 276 * attempt to decrement the counter without blocking. This
301 * enables us to avoid waiting if the res 277 * enables us to avoid waiting if the resource the completion
302 * is protecting is not available. 278 * is protecting is not available.
303 */ 279 */
304 bool try_wait_for_completion(struct completion 280 bool try_wait_for_completion(struct completion *x)
305 { 281 {
306 unsigned long flags; 282 unsigned long flags;
307 bool ret = true; 283 bool ret = true;
308 284
309 /* 285 /*
310 * Since x->done will need to be locke 286 * Since x->done will need to be locked only
311 * in the non-blocking case, we check 287 * in the non-blocking case, we check x->done
312 * first without taking the lock so we 288 * first without taking the lock so we can
313 * return early in the blocking case. 289 * return early in the blocking case.
314 */ 290 */
315 if (!READ_ONCE(x->done)) 291 if (!READ_ONCE(x->done))
316 return false; 292 return false;
317 293
318 raw_spin_lock_irqsave(&x->wait.lock, f !! 294 spin_lock_irqsave(&x->wait.lock, flags);
319 if (!x->done) 295 if (!x->done)
320 ret = false; 296 ret = false;
321 else if (x->done != UINT_MAX) 297 else if (x->done != UINT_MAX)
322 x->done--; 298 x->done--;
323 raw_spin_unlock_irqrestore(&x->wait.lo !! 299 spin_unlock_irqrestore(&x->wait.lock, flags);
324 return ret; 300 return ret;
325 } 301 }
326 EXPORT_SYMBOL(try_wait_for_completion); 302 EXPORT_SYMBOL(try_wait_for_completion);
327 303
328 /** 304 /**
329 * completion_done - Test to see if a com 305 * completion_done - Test to see if a completion has any waiters
330 * @x: completion structure 306 * @x: completion structure
331 * 307 *
332 * Return: 0 if there are waiters (wait_f 308 * Return: 0 if there are waiters (wait_for_completion() in progress)
333 * 1 if there are no waiters. 309 * 1 if there are no waiters.
334 * 310 *
335 * Note, this will always return true if 311 * Note, this will always return true if complete_all() was called on @X.
336 */ 312 */
337 bool completion_done(struct completion *x) 313 bool completion_done(struct completion *x)
338 { 314 {
339 unsigned long flags; 315 unsigned long flags;
340 316
341 if (!READ_ONCE(x->done)) 317 if (!READ_ONCE(x->done))
342 return false; 318 return false;
343 319
344 /* 320 /*
345 * If ->done, we need to wait for comp 321 * If ->done, we need to wait for complete() to release ->wait.lock
346 * otherwise we can end up freeing the 322 * otherwise we can end up freeing the completion before complete()
347 * is done referencing it. 323 * is done referencing it.
348 */ 324 */
349 raw_spin_lock_irqsave(&x->wait.lock, f !! 325 spin_lock_irqsave(&x->wait.lock, flags);
350 raw_spin_unlock_irqrestore(&x->wait.lo !! 326 spin_unlock_irqrestore(&x->wait.lock, flags);
351 return true; 327 return true;
352 } 328 }
353 EXPORT_SYMBOL(completion_done); 329 EXPORT_SYMBOL(completion_done);
354 330
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