x15/kern/condition.h

/*
 * 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.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