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/*
* Ouroboros - Copyright (C) 2016
*
* Read/Write locks
*
* Dimitri Staessens <dimitri.staessens@intec.ugent.be>
*
* 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 2 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, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <ouroboros/rw_lock.h>
int rw_lock_init(rw_lock_t * lock)
{
if (lock == NULL)
return -1;
pthread_mutex_init(&lock->lock, NULL);
pthread_mutex_init(&lock->i_lock, NULL);
lock->i = 0;
return 0;
}
void rw_lock_destroy(rw_lock_t * lock)
{
if (lock == NULL)
return;
pthread_mutex_destroy(&lock->lock);
pthread_mutex_destroy(&lock->i_lock);
lock->i = -1;
}
int rw_lock_rdlock(rw_lock_t * lock)
{
int ret = 0;
if (lock == NULL)
return -1;
pthread_mutex_lock(&lock->i_lock);
if (lock->i < 0) {
pthread_mutex_unlock(&lock->i_lock);
return -1;
}
if (lock->i == 0)
ret = pthread_mutex_lock(&lock->lock);
++(lock->i);
pthread_mutex_unlock(&lock->i_lock);
return ret;
}
int rw_lock_wrlock(rw_lock_t * lock)
{
if (lock == NULL)
return -1;
pthread_mutex_lock(&lock->i_lock);
if (lock->i < 0) {
pthread_mutex_unlock(&lock->i_lock);
return -1;
}
pthread_mutex_unlock(&lock->i_lock);
while (1) {
pthread_mutex_lock(&lock->i_lock);
if (lock->i == 0) {
pthread_mutex_unlock(&lock->i_lock);
break;
}
pthread_mutex_unlock(&lock->i_lock);
sched_yield();
}
++(lock->i);
return pthread_mutex_lock(&lock->lock);
}
int rw_lock_unlock(rw_lock_t * lock)
{
int ret = 0;
if (lock == NULL)
return -1;
pthread_mutex_lock(&lock->i_lock);
if (lock->i < 0) {
pthread_mutex_unlock(&lock->i_lock);
return -1;
}
--(lock->i);
if (lock->i == 0)
ret = pthread_mutex_unlock(&lock->lock);
pthread_mutex_unlock(&lock->i_lock);
return ret;
}
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