// SPDX-License-Identifier: GPL-2.0 /* * Generic wait-for-completion handler; * * It differs from semaphores in that their default case is the opposite, * wait_for_completion default blocks whereas semaphore default non-block. The * interface also makes it easy to 'complete' multiple waiting threads, * something which isn't entirely natural for semaphores. * * But more importantly, the primitive documents the usage. Semaphores would * typically be used for exclusion which gives rise to priority inversion. * Waiting for completion is a typically sync point, but not an exclusion point. */ #include <linux/linkage.h>#include <linux/sched/debug.h>#include <linux/completion.h>#include "sched.h" static void complete_with_flags(struct completion *x, int wake_flags){	unsigned long flags; 	raw_spin_lock_irqsave(&x->wait.lock, flags); 	if (x->done != UINT_MAX)		x->done++;	swake_up_locked(&x->wait, wake_flags);	raw_spin_unlock_irqrestore(&x->wait.lock, flags);} void complete_on_current_cpu(struct completion *x){	return complete_with_flags(x, WF_CURRENT_CPU);} /** * complete: - signals a single thread waiting on this completion * @x:  holds the state of this particular completion * * This will wake up a single thread waiting on this completion. Threads will be * awakened in the same order in which they were queued. * * See also complete_all(), wait_for_completion() and related routines. * * If this function wakes up a task, it executes a full memory barrier before * accessing the task state. */void complete(struct completion *x){	complete_with_flags(x, 0);}EXPORT_SYMBOL(complete); /** * complete_all: - signals all threads waiting on this completion * @x:  holds the state of this particular completion * * This will wake up all threads waiting on this particular completion event. * * If this function wakes up a task, it executes a full memory barrier before * accessing the task state. * * Since complete_all() sets the completion of @x permanently to done * to allow multiple waiters to finish, a call to reinit_completion() * must be used on @x if @x is to be used again. The code must make * sure that all waiters have woken and finished before reinitializing * @x. Also note that the function completion_done() can not be used * to know if there are still waiters after complete_all() has been called. */void complete_all(struct completion *x){	unsigned long flags; 	lockdep_assert_RT_in_threaded_ctx(); 	raw_spin_lock_irqsave(&x->wait.lock, flags);	x->done = UINT_MAX;	swake_up_all_locked(&x->wait);	raw_spin_unlock_irqrestore(&x->wait.lock, flags);}EXPORT_SYMBOL(complete_all); static inline long __scheddo_wait_for_common(struct completion *x,		   long (*action)(long), long timeout, int state){	if (!x->done) {		DECLARE_SWAITQUEUE(wait); 		do {			if (signal_pending_state(state, current)) {				timeout = -ERESTARTSYS;				break;			}			__prepare_to_swait(&x->wait, &wait);			__set_current_state(state);			raw_spin_unlock_irq(&x->wait.lock);			timeout = action(timeout);			raw_spin_lock_irq(&x->wait.lock);		} while (!x->done && timeout);		__finish_swait(&x->wait, &wait);		if (!x->done)			return timeout;	}	if (x->done != UINT_MAX)		x->done--;	return timeout ?: 1;} static inline long __sched__wait_for_common(struct completion *x,		  long (*action)(long), long timeout, int state){	might_sleep(); 	complete_acquire(x); 	raw_spin_lock_irq(&x->wait.lock);	timeout = do_wait_for_common(x, action, timeout, state);	raw_spin_unlock_irq(&x->wait.lock); 	complete_release(x); 	return timeout;} static long __schedwait_for_common(struct completion *x, long timeout, int state){	return __wait_for_common(x, schedule_timeout, timeout, state);} static long __schedwait_for_common_io(struct completion *x, long timeout, int state){	return __wait_for_common(x, io_schedule_timeout, timeout, state);} /** * wait_for_completion: - waits for completion of a task * @x:  holds the state of this particular completion * * This waits to be signaled for completion of a specific task. It is NOT * interruptible and there is no timeout. * * See also similar routines (i.e. wait_for_completion_timeout()) with timeout * and interrupt capability. Also see complete(). */void __sched wait_for_completion(struct completion *x){	wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);}EXPORT_SYMBOL(wait_for_completion); /** * wait_for_completion_timeout: - waits for completion of a task (w/timeout) * @x:  holds the state of this particular completion * @timeout:  timeout value in jiffies * * This waits for either a completion of a specific task to be signaled or for a * specified timeout to expire. The timeout is in jiffies. It is not * interruptible. * * Return: 0 if timed out, and positive (at least 1, or number of jiffies left * till timeout) if completed. */unsigned long __schedwait_for_completion_timeout(struct completion *x, unsigned long timeout){	return wait_for_common(x, timeout, TASK_UNINTERRUPTIBLE);}EXPORT_SYMBOL(wait_for_completion_timeout); /** * wait_for_completion_io: - waits for completion of a task * @x:  holds the state of this particular completion * * This waits to be signaled for completion of a specific task. It is NOT * interruptible and there is no timeout. The caller is accounted as waiting * for IO (which traditionally means blkio only). */void __sched wait_for_completion_io(struct completion *x){	wait_for_common_io(x, MAX_SCHEDULE_TIMEOUT, TASK_UNINTERRUPTIBLE);}EXPORT_SYMBOL(wait_for_completion_io); /** * wait_for_completion_io_timeout: - waits for completion of a task (w/timeout) * @x:  holds the state of this particular completion * @timeout:  timeout value in jiffies * * This waits for either a completion of a specific task to be signaled or for a * specified timeout to expire. The timeout is in jiffies. It is not * interruptible. The caller is accounted as waiting for IO (which traditionally * means blkio only). * * Return: 0 if timed out, and positive (at least 1, or number of jiffies left * till timeout) if completed. */unsigned long __schedwait_for_completion_io_timeout(struct completion *x, unsigned long timeout){	return wait_for_common_io(x, timeout, TASK_UNINTERRUPTIBLE);}EXPORT_SYMBOL(wait_for_completion_io_timeout); /** * wait_for_completion_interruptible: - waits for completion of a task (w/intr) * @x:  holds the state of this particular completion * * This waits for completion of a specific task to be signaled. It is * interruptible. * * Return: -ERESTARTSYS if interrupted, 0 if completed. */int __sched wait_for_completion_interruptible(struct completion *x){	long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE); 	if (t == -ERESTARTSYS)		return t;	return 0;}EXPORT_SYMBOL(wait_for_completion_interruptible); /** * wait_for_completion_interruptible_timeout: - waits for completion (w/(to,intr)) * @x:  holds the state of this particular completion * @timeout:  timeout value in jiffies * * This waits for either a completion of a specific task to be signaled or for a * specified timeout to expire. It is interruptible. The timeout is in jiffies. * * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1, * or number of jiffies left till timeout) if completed. */long __schedwait_for_completion_interruptible_timeout(struct completion *x,					  unsigned long timeout){	return wait_for_common(x, timeout, TASK_INTERRUPTIBLE);}EXPORT_SYMBOL(wait_for_completion_interruptible_timeout); /** * wait_for_completion_killable: - waits for completion of a task (killable) * @x:  holds the state of this particular completion * * This waits to be signaled for completion of a specific task. It can be * interrupted by a kill signal. * * Return: -ERESTARTSYS if interrupted, 0 if completed. */int __sched wait_for_completion_killable(struct completion *x){	long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, TASK_KILLABLE); 	if (t == -ERESTARTSYS)		return t;	return 0;}EXPORT_SYMBOL(wait_for_completion_killable); int __sched wait_for_completion_state(struct completion *x, unsigned int state){	long t = wait_for_common(x, MAX_SCHEDULE_TIMEOUT, state); 	if (t == -ERESTARTSYS)		return t;	return 0;}EXPORT_SYMBOL(wait_for_completion_state); /** * wait_for_completion_killable_timeout: - waits for completion of a task (w/(to,killable)) * @x:  holds the state of this particular completion * @timeout:  timeout value in jiffies * * This waits for either a completion of a specific task to be * signaled or for a specified timeout to expire. It can be * interrupted by a kill signal. The timeout is in jiffies. * * Return: -ERESTARTSYS if interrupted, 0 if timed out, positive (at least 1, * or number of jiffies left till timeout) if completed. */long __schedwait_for_completion_killable_timeout(struct completion *x,				     unsigned long timeout){	return wait_for_common(x, timeout, TASK_KILLABLE);}EXPORT_SYMBOL(wait_for_completion_killable_timeout); /** *	try_wait_for_completion - try to decrement a completion without blocking *	@x:	completion structure * *	Return: 0 if a decrement cannot be done without blocking *		 1 if a decrement succeeded. * *	If a completion is being used as a counting completion, *	attempt to decrement the counter without blocking. This *	enables us to avoid waiting if the resource the completion *	is protecting is not available. */bool try_wait_for_completion(struct completion *x){	unsigned long flags;	bool ret = true; 	/*	 * Since x->done will need to be locked only	 * in the non-blocking case, we check x->done	 * first without taking the lock so we can	 * return early in the blocking case.	 */	if (!READ_ONCE(x->done))		return false; 	raw_spin_lock_irqsave(&x->wait.lock, flags);	if (!x->done)		ret = false;	else if (x->done != UINT_MAX)		x->done--;	raw_spin_unlock_irqrestore(&x->wait.lock, flags);	return ret;}EXPORT_SYMBOL(try_wait_for_completion); /** *	completion_done - Test to see if a completion has any waiters *	@x:	completion structure * *	Return: 0 if there are waiters (wait_for_completion() in progress) *		 1 if there are no waiters. * *	Note, this will always return true if complete_all() was called on @X. */bool completion_done(struct completion *x){	unsigned long flags; 	if (!READ_ONCE(x->done))		return false; 	/*	 * If ->done, we need to wait for complete() to release ->wait.lock	 * otherwise we can end up freeing the completion before complete()	 * is done referencing it.	 */	raw_spin_lock_irqsave(&x->wait.lock, flags);	raw_spin_unlock_irqrestore(&x->wait.lock, flags);	return true;}EXPORT_SYMBOL(completion_done);