4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License, Version 1.0 only
6 * (the "License"). You may not use this file except in compliance
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://www.opensolaris.org/os/licensing.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
23 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
27 #pragma ident "%Z%%M% %I% %E% SMI"
30 * This file implements a barrier, a synchronization primitive designed to allow
31 * threads to wait for each other at given points. Barriers are initialized
32 * with a given number of threads, n, using barrier_init(). When a thread calls
33 * barrier_wait(), that thread blocks until n - 1 other threads reach the
34 * barrier_wait() call using the same barrier_t. When n threads have reached
35 * the barrier, they are all awakened and sent on their way. One of the threads
36 * returns from barrier_wait() with a return code of 1; the remaining threads
37 * get a return code of 0.
49 barrier_init(barrier_t *bar, int nthreads)
51 pthread_mutex_init(&bar->bar_lock, NULL);
53 sema_init(&bar->bar_sem, 0, USYNC_THREAD, NULL);
55 sem_init(&bar->bar_sem, 0, 0);
59 bar->bar_nthr = nthreads;
63 barrier_wait(barrier_t *bar)
65 pthread_mutex_lock(&bar->bar_lock);
67 if (++bar->bar_numin < bar->bar_nthr) {
68 pthread_mutex_unlock(&bar->bar_lock);
70 sema_wait(&bar->bar_sem);
72 sem_wait(&bar->bar_sem);
80 /* reset for next use */
82 for (i = 1; i < bar->bar_nthr; i++)
84 sema_post(&bar->bar_sem);
86 sem_post(&bar->bar_sem);
88 pthread_mutex_unlock(&bar->bar_lock);