2 * Generic wait-for-completion handler;
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.
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.
14 #include <linux/sched.h>
15 #include <linux/completion.h>
18 * complete: - signals a single thread waiting on this completion
19 * @x: holds the state of this particular completion
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.
24 * See also complete_all(), wait_for_completion() and related routines.
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.
29 void complete(struct completion *x)
33 spin_lock_irqsave(&x->wait.lock, flags);
35 __wake_up_locked(&x->wait, TASK_NORMAL, 1);
36 spin_unlock_irqrestore(&x->wait.lock, flags);
38 EXPORT_SYMBOL(complete);
41 * complete_all: - signals all threads waiting on this completion
42 * @x: holds the state of this particular completion
44 * This will wake up all threads waiting on this particular completion event.
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.
49 void complete_all(struct completion *x)
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);
58 EXPORT_SYMBOL(complete_all);
60 static inline long __sched
61 do_wait_for_common(struct completion *x,
62 long (*action)(long), long timeout, int state)
65 DECLARE_WAITQUEUE(wait, current);
67 __add_wait_queue_tail_exclusive(&x->wait, &wait);
69 __set_current_state(state);
70 spin_unlock_irq(&x->wait.lock);
71 timeout = action(timeout);
72 spin_lock_irq(&x->wait.lock);
73 } while (!x->done && timeout);
74 __remove_wait_queue(&x->wait, &wait);
82 static inline long __sched
83 __wait_for_common(struct completion *x,
84 long (*action)(long), long timeout, int state)
88 spin_lock_irq(&x->wait.lock);
89 timeout = do_wait_for_common(x, action, timeout, state);
90 spin_unlock_irq(&x->wait.lock);
95 wait_for_common(struct completion *x, long timeout, int state)
97 return __wait_for_common(x, schedule_timeout, timeout, state);
101 wait_for_common_io(struct completion *x, long timeout, int state)
103 return __wait_for_common(x, io_schedule_timeout, timeout, state);
107 * wait_for_completion: - waits for completion of a task
108 * @x: holds the state of this particular completion
110 * This waits to be signaled for completion of a specific task. It is NOT
111 * interruptible and there is no timeout.
113 * See also similar routines (i.e. wait_for_completion_timeout()) with timeout
114 * and interrupt capability. Also see complete().
116 void __sched wait_for_completion(struct completion *x)
118 wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
120 EXPORT_SYMBOL(wait_for_completion);
123 * wait_for_completion_timeout: - waits for completion of a task (w/timeout)
124 * @x: holds the state of this particular completion
125 * @timeout: timeout value in jiffies
127 * This waits for either a completion of a specific task to be signaled or for a
128 * specified timeout to expire. The timeout is in jiffies. It is not
131 * Return: 0 if timed out, and positive (at least 1, or number of jiffies left
132 * till timeout) if completed.
134 unsigned long __sched
135 wait_for_completion_timeout(struct completion *x, unsigned long timeout)
137 return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE);
139 EXPORT_SYMBOL(wait_for_completion_timeout);
142 * wait_for_completion_io: - waits for completion of a task
143 * @x: holds the state of this particular completion
145 * This waits to be signaled for completion of a specific task. It is NOT
146 * interruptible and there is no timeout. The caller is accounted as waiting
147 * for IO (which traditionally means blkio only).
149 void __sched wait_for_completion_io(struct completion *x)
151 wait_for_common_io(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);
153 EXPORT_SYMBOL(wait_for_completion_io);
156 * wait_for_completion_io_timeout: - waits for completion of a task (w/timeout)
157 * @x: holds the state of this particular completion
158 * @timeout: timeout value in jiffies
160 * This waits for either a completion of a specific task to be signaled or for a
161 * specified timeout to expire. The timeout is in jiffies. It is not
162 * interruptible. The caller is accounted as waiting for IO (which traditionally
165 * Return: 0 if timed out, and positive (at least 1, or number of jiffies left
166 * till timeout) if completed.
168 unsigned long __sched
169 wait_for_completion_io_timeout(struct completion *x, unsigned long timeout)
171 return wait_for_common_io(x, timeout, TASK_UNINTERRUPTIBLE);
173 EXPORT_SYMBOL(wait_for_completion_io_timeout);
176 * wait_for_completion_interruptible: - waits for completion of a task (w/intr)
177 * @x: holds the state of this particular completion
179 * This waits for completion of a specific task to be signaled. It is
182 * Return: -ERESTARTSYS if interrupted, 0 if completed.
184 int __sched wait_for_completion_interruptible(struct completion *x)
186 wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE);
189 EXPORT_SYMBOL(wait_for_completion_interruptible);
192 * wait_for_completion_interruptible_timeout: - waits for completion (w/(to,intr))
193 * @x: holds the state of this particular completion
194 * @timeout: timeout value in jiffies
196 * This waits for either a completion of a specific task to be signaled or for a
197 * specified timeout to expire. It is interruptible. The timeout is in jiffies.
199 * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1,
200 * or number of jiffies left till timeout) if completed.
203 wait_for_completion_interruptible_timeout(struct completion *x,
204 unsigned long timeout)
206 return wait_for_common(x, timeout, TASK_INTERRUPTIBLE);
208 EXPORT_SYMBOL(wait_for_completion_interruptible_timeout);
211 * wait_for_completion_killable: - waits for completion of a task (killable)
212 * @x: holds the state of this particular completion
214 * This waits to be signaled for completion of a specific task. It can be
215 * interrupted by a kill signal.
217 * Return: -ERESTARTSYS if interrupted, 0 if completed.
219 int __sched wait_for_completion_killable(struct completion *x)
221 wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE);
224 EXPORT_SYMBOL(wait_for_completion_killable);
227 * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable))
228 * @x: holds the state of this particular completion
229 * @timeout: timeout value in jiffies
231 * This waits for either a completion of a specific task to be
232 * signaled or for a specified timeout to expire. It can be
233 * interrupted by a kill signal. The timeout is in jiffies.
235 * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1,
236 * or number of jiffies left till timeout) if completed.
239 wait_for_completion_killable_timeout(struct completion *x,
240 unsigned long timeout)
242 return wait_for_common(x, timeout, TASK_KILLABLE);
244 EXPORT_SYMBOL(wait_for_completion_killable_timeout);
247 * try_wait_for_completion - try to decrement a completion without blocking
248 * @x: completion structure
250 * Return: 0 if a decrement cannot be done without blocking
251 * 1 if a decrement succeeded.
253 * If a completion is being used as a counting completion,
254 * attempt to decrement the counter without blocking. This
255 * enables us to avoid waiting if the resource the completion
256 * is protecting is not available.
258 bool try_wait_for_completion(struct completion *x)
264 * Since x->done will need to be locked only
265 * in the non-blocking case, we check x->done
266 * first without taking the lock so we can
267 * return early in the blocking case.
269 if (!READ_ONCE(x->done))
272 spin_lock_irqsave(&x->wait.lock, flags);
277 spin_unlock_irqrestore(&x->wait.lock, flags);
280 EXPORT_SYMBOL(try_wait_for_completion);
283 * completion_done - Test to see if a completion has any waiters
284 * @x: completion structure
286 * Return: 0 if there are waiters (wait_for_completion() in progress)
287 * 1 if there are no waiters.
290 bool completion_done(struct completion *x)
292 if (!READ_ONCE(x->done))
296 * If ->done, we need to wait for complete() to release ->wait.lock
297 * otherwise we can end up freeing the completion before complete()
298 * is done referencing it.
300 * The RMB pairs with complete()'s RELEASE of ->wait.lock and orders
301 * the loads of ->done and ->wait.lock such that we cannot observe
302 * the lock before complete() acquires it while observing the ->done
303 * after it's acquired the lock.
306 //spin_unlock_wait(&x->wait.lock);
307 spin_lock(&x->wait.lock);
308 spin_unlock(&x->wait.lock);
311 EXPORT_SYMBOL(completion_done);