xref: /titanic_50/usr/src/tools/ctf/cvt/barrier.c (revision e07d9cb85217949d497b02d7211de8a197d2f2eb)
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 #include <synch.h>
42 #include <stdio.h>
43 
44 #include "barrier.h"
45 
46 void
47 barrier_init(barrier_t *bar, int nthreads)
48 {
49 	pthread_mutex_init(&bar->bar_lock, NULL);
50 	sema_init(&bar->bar_sem, 0, USYNC_THREAD, NULL);
51 
52 	bar->bar_numin = 0;
53 	bar->bar_nthr = nthreads;
54 }
55 
56 int
57 barrier_wait(barrier_t *bar)
58 {
59 	pthread_mutex_lock(&bar->bar_lock);
60 
61 	if (++bar->bar_numin < bar->bar_nthr) {
62 		pthread_mutex_unlock(&bar->bar_lock);
63 		sema_wait(&bar->bar_sem);
64 
65 		return (0);
66 
67 	} else {
68 		int i;
69 
70 		/* reset for next use */
71 		bar->bar_numin = 0;
72 		for (i = 1; i < bar->bar_nthr; i++)
73 			sema_post(&bar->bar_sem);
74 		pthread_mutex_unlock(&bar->bar_lock);
75 
76 		return (1);
77 	}
78 }
79