1 /*
2 * CDDL HEADER START
3 *
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
7 * with the License.
8 *
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.
13 *
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]
19 *
20 * CDDL HEADER END
21 */
22 /*
23 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 #pragma ident "%Z%%M% %I% %E% SMI"
28
29 /*
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.
38 */
39
40 #include <pthread.h>
41 #if defined(sun)
42 #include <synch.h>
43 #else
44 #define USYNC_THREAD 1
45 #define sema_init(a, b, c, d) sem_init((a), (c) != USYNC_THREAD, (b))
46 #define sema_wait(a) sem_wait(a)
47 #define sema_post(a) sem_post(a)
48 #endif
49 #include <stdio.h>
50
51 #include "barrier.h"
52
53 void
barrier_init(barrier_t * bar,int nthreads)54 barrier_init(barrier_t *bar, int nthreads)
55 {
56 pthread_mutex_init(&bar->bar_lock, NULL);
57 sema_init(&bar->bar_sem, 0, USYNC_THREAD, NULL);
58 bar->bar_numin = 0;
59 bar->bar_nthr = nthreads;
60 }
61
62 int
barrier_wait(barrier_t * bar)63 barrier_wait(barrier_t *bar)
64 {
65 pthread_mutex_lock(&bar->bar_lock);
66
67 if (++bar->bar_numin < bar->bar_nthr) {
68 pthread_mutex_unlock(&bar->bar_lock);
69 sema_wait(&bar->bar_sem);
70 return (0);
71
72 } else {
73 int i;
74
75 /* reset for next use */
76 bar->bar_numin = 0;
77 for (i = 1; i < bar->bar_nthr; i++)
78 sema_post(&bar->bar_sem);
79 pthread_mutex_unlock(&bar->bar_lock);
80
81 return (1);
82 }
83 }
84