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