barrier.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2002 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
/*
* This file implements a barrier, a synchronization primitive designed to allow
* threads to wait for each other at given points. Barriers are initialized
* with a given number of threads, n, using barrier_init(). When a thread calls
* barrier_wait(), that thread blocks until n - 1 other threads reach the
* barrier_wait() call using the same barrier_t. When n threads have reached
* the barrier, they are all awakened and sent on their way. One of the threads
* returns from barrier_wait() with a return code of 1; the remaining threads
* get a return code of 0.
*/
#include <pthread.h>
#include <synch.h>
#include <stdio.h>
#include "barrier.h"
void
barrier_init(barrier_t *bar, int nthreads)
{
pthread_mutex_init(&bar->bar_lock, NULL);
sema_init(&bar->bar_sem, 0, USYNC_THREAD, NULL);
bar->bar_numin = 0;
bar->bar_nthr = nthreads;
}
int
barrier_wait(barrier_t *bar)
{
pthread_mutex_lock(&bar->bar_lock);
if (++bar->bar_numin < bar->bar_nthr) {
pthread_mutex_unlock(&bar->bar_lock);
sema_wait(&bar->bar_sem);
return (0);
} else {
int i;
/* reset for next use */
bar->bar_numin = 0;
for (i = 1; i < bar->bar_nthr; i++)
sema_post(&bar->bar_sem);
pthread_mutex_unlock(&bar->bar_lock);
return (1);
}
}