usr/src/tools/ctf/cvt/barrier.c

   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 }