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/*
* Copyright (c) 2013-2018 Richard Braun.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*
* Condition variables.
*
* A condition variable is a synchronization primitive used to wait
* until a predicate becomes true. Multiple threads can be waiting
* for this condition. In order to synchronize changes on the predicate
* with waiting and signalling, a condition variable must be associated
* with a mutex.
*/
#ifndef KERN_CONDITION_H
#define KERN_CONDITION_H
#include <stdint.h>
#include <kern/condition_types.h>
#include <kern/mutex_types.h>
struct condition;
/*
* Initialize a condition variable.
*/
#define condition_init(c) ((void)(c))
/*
* Wait for a signal on the given condition variable.
*
* The associated mutex must be locked when calling this function.
* It is unlocked before waiting and relocked before returning.
*
* When bounding the duration of the wait, the caller must pass an absolute
* time in ticks, and ETIMEDOUT is returned if that time is reached before
* the sleep queue is signalled.
*/
void condition_wait(struct condition *condition, struct mutex *mutex);
int condition_timedwait(struct condition *condition,
struct mutex *mutex, uint64_t ticks);
/*
* Wake up one (signal) or all (broadcast) threads waiting on a
* condition variable, if any.
*
* Although it is not necessary to hold the mutex associated to the
* condition variable when calling these functions, doing so guarantees
* that a wake-up done when changing the predicate cannot be missed by
* waiting threads.
*/
void condition_signal(struct condition *condition);
void condition_broadcast(struct condition *condition);
#endif /* KERN_CONDITION_H */
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