1 /* 2 * Generic wait-for-completion handler; 3 * 4 * It differs from semaphores in that their default case is the opposite, 5 * wait_for_completion default blocks whereas semaphore default non-block. The 6 * interface also makes it easy to 'complete' multiple waiting threads, 7 * something which isn't entirely natural for semaphores. 8 * 9 * But more importantly, the primitive documents the usage. Semaphores would 10 * typically be used for exclusion which gives rise to priority inversion. 11 * Waiting for completion is a typically sync point, but not an exclusion point. 12 */ 13 14 #include <linux/sched.h> 15 #include <linux/completion.h> 16 17 /** 18 * complete: - signals a single thread waiting on this completion 19 * @x: holds the state of this particular completion 20 * 21 * This will wake up a single thread waiting on this completion. Threads will be 22 * awakened in the same order in which they were queued. 23 * 24 * See also complete_all(), wait_for_completion() and related routines. 25 * 26 * It may be assumed that this function implies a write memory barrier before 27 * changing the task state if and only if any tasks are woken up. 28 */ 29 void complete(struct completion *x) 30 { 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); 37 } 38 EXPORT_SYMBOL(complete); 39 40 /** 41 * complete_all: - signals all threads waiting on this completion 42 * @x: holds the state of this particular completion 43 * 44 * This will wake up all threads waiting on this particular completion event. 45 * 46 * It may be assumed that this function implies a write memory barrier before 47 * changing the task state if and only if any tasks are woken up. 48 */ 49 void complete_all(struct completion *x) 50 { 51 unsigned long flags; 52 53 spin_lock_irqsave(&x->wait.lock, flags); 54 x->done += UINT_MAX/2; 55 __wake_up_locked(&x->wait, TASK_NORMAL, 0); 56 spin_unlock_irqrestore(&x->wait.lock, flags); 57 } 58 EXPORT_SYMBOL(complete_all); 59 60 static inline long __sched 61 do_wait_for_common(struct completion *x, 62 long (*action)(long), long timeout, int state) 63 { 64 if (!x->done) { 65 DECLARE_WAITQUEUE(wait, current); 66 67 __add_wait_queue_tail_exclusive(&x->wait, &wait); 68 do { 69 if (signal_pending_state(state, current)) { 70 timeout = -ERESTARTSYS; 71 break; 72 } 73 __set_current_state(state); 74 spin_unlock_irq(&x->wait.lock); 75 timeout = action(timeout); 76 spin_lock_irq(&x->wait.lock); 77 } while (!x->done && timeout); 78 __remove_wait_queue(&x->wait, &wait); 79 if (!x->done) 80 return timeout; 81 } 82 x->done--; 83 return timeout ?: 1; 84 } 85 86 static inline long __sched 87 __wait_for_common(struct completion *x, 88 long (*action)(long), long timeout, int state) 89 { 90 might_sleep(); 91 92 spin_lock_irq(&x->wait.lock); 93 timeout = do_wait_for_common(x, action, timeout, state); 94 spin_unlock_irq(&x->wait.lock); 95 return timeout; 96 } 97 98 static long __sched 99 wait_for_common(struct completion *x, long timeout, int state) 100 { 101 return __wait_for_common(x, schedule_timeout, timeout, state); 102 } 103 104 static long __sched 105 wait_for_common_io(struct completion *x, long timeout, int state) 106 { 107 return __wait_for_common(x, io_schedule_timeout, timeout, state); 108 } 109 110 /** 111 * wait_for_completion: - waits for completion of a task 112 * @x: holds the state of this particular completion 113 * 114 * This waits to be signaled for completion of a specific task. It is NOT 115 * interruptible and there is no timeout. 116 * 117 * See also similar routines (i.e. wait_for_completion_timeout()) with timeout 118 * and interrupt capability. Also see complete(). 119 */ 120 void __sched wait_for_completion(struct completion *x) 121 { 122 wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE); 123 } 124 EXPORT_SYMBOL(wait_for_completion); 125 126 /** 127 * wait_for_completion_timeout: - waits for completion of a task (w/timeout) 128 * @x: holds the state of this particular completion 129 * @timeout: timeout value in jiffies 130 * 131 * This waits for either a completion of a specific task to be signaled or for a 132 * specified timeout to expire. The timeout is in jiffies. It is not 133 * interruptible. 134 * 135 * Return: 0 if timed out, and positive (at least 1, or number of jiffies left 136 * till timeout) if completed. 137 */ 138 unsigned long __sched 139 wait_for_completion_timeout(struct completion *x, unsigned long timeout) 140 { 141 return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE); 142 } 143 EXPORT_SYMBOL(wait_for_completion_timeout); 144 145 /** 146 * wait_for_completion_io: - waits for completion of a task 147 * @x: holds the state of this particular completion 148 * 149 * This waits to be signaled for completion of a specific task. It is NOT 150 * interruptible and there is no timeout. The caller is accounted as waiting 151 * for IO. 152 */ 153 void __sched wait_for_completion_io(struct completion *x) 154 { 155 wait_for_common_io(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE); 156 } 157 EXPORT_SYMBOL(wait_for_completion_io); 158 159 /** 160 * wait_for_completion_io_timeout: - waits for completion of a task (w/timeout) 161 * @x: holds the state of this particular completion 162 * @timeout: timeout value in jiffies 163 * 164 * This waits for either a completion of a specific task to be signaled or for a 165 * specified timeout to expire. The timeout is in jiffies. It is not 166 * interruptible. The caller is accounted as waiting for IO. 167 * 168 * Return: 0 if timed out, and positive (at least 1, or number of jiffies left 169 * till timeout) if completed. 170 */ 171 unsigned long __sched 172 wait_for_completion_io_timeout(struct completion *x, unsigned long timeout) 173 { 174 return wait_for_common_io(x, timeout, TASK_UNINTERRUPTIBLE); 175 } 176 EXPORT_SYMBOL(wait_for_completion_io_timeout); 177 178 /** 179 * wait_for_completion_interruptible: - waits for completion of a task (w/intr) 180 * @x: holds the state of this particular completion 181 * 182 * This waits for completion of a specific task to be signaled. It is 183 * interruptible. 184 * 185 * Return: -ERESTARTSYS if interrupted, 0 if completed. 186 */ 187 int __sched wait_for_completion_interruptible(struct completion *x) 188 { 189 long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE); 190 if (t == -ERESTARTSYS) 191 return t; 192 return 0; 193 } 194 EXPORT_SYMBOL(wait_for_completion_interruptible); 195 196 /** 197 * wait_for_completion_interruptible_timeout: - waits for completion (w/(to,intr)) 198 * @x: holds the state of this particular completion 199 * @timeout: timeout value in jiffies 200 * 201 * This waits for either a completion of a specific task to be signaled or for a 202 * specified timeout to expire. It is interruptible. The timeout is in jiffies. 203 * 204 * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1, 205 * or number of jiffies left till timeout) if completed. 206 */ 207 long __sched 208 wait_for_completion_interruptible_timeout(struct completion *x, 209 unsigned long timeout) 210 { 211 return wait_for_common(x, timeout, TASK_INTERRUPTIBLE); 212 } 213 EXPORT_SYMBOL(wait_for_completion_interruptible_timeout); 214 215 /** 216 * wait_for_completion_killable: - waits for completion of a task (killable) 217 * @x: holds the state of this particular completion 218 * 219 * This waits to be signaled for completion of a specific task. It can be 220 * interrupted by a kill signal. 221 * 222 * Return: -ERESTARTSYS if interrupted, 0 if completed. 223 */ 224 int __sched wait_for_completion_killable(struct completion *x) 225 { 226 long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE); 227 if (t == -ERESTARTSYS) 228 return t; 229 return 0; 230 } 231 EXPORT_SYMBOL(wait_for_completion_killable); 232 233 /** 234 * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable)) 235 * @x: holds the state of this particular completion 236 * @timeout: timeout value in jiffies 237 * 238 * This waits for either a completion of a specific task to be 239 * signaled or for a specified timeout to expire. It can be 240 * interrupted by a kill signal. The timeout is in jiffies. 241 * 242 * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1, 243 * or number of jiffies left till timeout) if completed. 244 */ 245 long __sched 246 wait_for_completion_killable_timeout(struct completion *x, 247 unsigned long timeout) 248 { 249 return wait_for_common(x, timeout, TASK_KILLABLE); 250 } 251 EXPORT_SYMBOL(wait_for_completion_killable_timeout); 252 253 /** 254 * try_wait_for_completion - try to decrement a completion without blocking 255 * @x: completion structure 256 * 257 * Return: 0 if a decrement cannot be done without blocking 258 * 1 if a decrement succeeded. 259 * 260 * If a completion is being used as a counting completion, 261 * attempt to decrement the counter without blocking. This 262 * enables us to avoid waiting if the resource the completion 263 * is protecting is not available. 264 */ 265 bool try_wait_for_completion(struct completion *x) 266 { 267 unsigned long flags; 268 int ret = 1; 269 270 spin_lock_irqsave(&x->wait.lock, flags); 271 if (!x->done) 272 ret = 0; 273 else 274 x->done--; 275 spin_unlock_irqrestore(&x->wait.lock, flags); 276 return ret; 277 } 278 EXPORT_SYMBOL(try_wait_for_completion); 279 280 /** 281 * completion_done - Test to see if a completion has any waiters 282 * @x: completion structure 283 * 284 * Return: 0 if there are waiters (wait_for_completion() in progress) 285 * 1 if there are no waiters. 286 * 287 */ 288 bool completion_done(struct completion *x) 289 { 290 unsigned long flags; 291 int ret = 1; 292 293 spin_lock_irqsave(&x->wait.lock, flags); 294 if (!x->done) 295 ret = 0; 296 spin_unlock_irqrestore(&x->wait.lock, flags); 297 return ret; 298 } 299 EXPORT_SYMBOL(completion_done); 300