1/* Copyright (C) 2005 Free Software Foundation, Inc.
2   Contributed by Richard Henderson <rth@redhat.com>.
3
4   This file is part of the GNU OpenMP Library (libgomp).
5
6   Libgomp is free software; you can redistribute it and/or modify it
7   under the terms of the GNU Lesser General Public License as published by
8   the Free Software Foundation; either version 2.1 of the License, or
9   (at your option) any later version.
10
11   Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
12   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
13   FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for
14   more details.
15
16   You should have received a copy of the GNU Lesser General Public License
17   along with libgomp; see the file COPYING.LIB.  If not, write to the
18   Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
19   MA 02110-1301, USA.  */
20
21/* As a special exception, if you link this library with other files, some
22   of which are compiled with GCC, to produce an executable, this library
23   does not by itself cause the resulting executable to be covered by the
24   GNU General Public License.  This exception does not however invalidate
25   any other reasons why the executable file might be covered by the GNU
26   General Public License.  */
27
28/* This is the default implementation of a barrier synchronization mechanism
29   for libgomp.  This type is private to the library.  Note that we rely on
30   being able to adjust the barrier count while threads are blocked, so the
31   POSIX pthread_barrier_t won't work.  */
32
33#include "libgomp.h"
34
35
36void
37gomp_barrier_init (gomp_barrier_t *bar, unsigned count)
38{
39  gomp_mutex_init (&bar->mutex1);
40#ifndef HAVE_SYNC_BUILTINS
41  gomp_mutex_init (&bar->mutex2);
42#endif
43  gomp_sem_init (&bar->sem1, 0);
44  gomp_sem_init (&bar->sem2, 0);
45  bar->total = count;
46  bar->arrived = 0;
47}
48
49void
50gomp_barrier_destroy (gomp_barrier_t *bar)
51{
52  /* Before destroying, make sure all threads have left the barrier.  */
53  gomp_mutex_lock (&bar->mutex1);
54  gomp_mutex_unlock (&bar->mutex1);
55
56  gomp_mutex_destroy (&bar->mutex1);
57#ifndef HAVE_SYNC_BUILTINS
58  gomp_mutex_destroy (&bar->mutex2);
59#endif
60  gomp_sem_destroy (&bar->sem1);
61  gomp_sem_destroy (&bar->sem2);
62}
63
64void
65gomp_barrier_reinit (gomp_barrier_t *bar, unsigned count)
66{
67  gomp_mutex_lock (&bar->mutex1);
68  bar->total = count;
69  gomp_mutex_unlock (&bar->mutex1);
70}
71
72void
73gomp_barrier_wait_end (gomp_barrier_t *bar, bool last)
74{
75  unsigned int n;
76
77  if (last)
78    {
79      n = --bar->arrived;
80      if (n > 0)
81	{
82	  do
83	    gomp_sem_post (&bar->sem1);
84	  while (--n != 0);
85	  gomp_sem_wait (&bar->sem2);
86	}
87      gomp_mutex_unlock (&bar->mutex1);
88    }
89  else
90    {
91      gomp_mutex_unlock (&bar->mutex1);
92      gomp_sem_wait (&bar->sem1);
93
94#ifdef HAVE_SYNC_BUILTINS
95      n = __sync_add_and_fetch (&bar->arrived, -1);
96#else
97      gomp_mutex_lock (&bar->mutex2);
98      n = --bar->arrived;
99      gomp_mutex_unlock (&bar->mutex2);
100#endif
101
102      if (n == 0)
103	gomp_sem_post (&bar->sem2);
104    }
105}
106
107void
108gomp_barrier_wait (gomp_barrier_t *barrier)
109{
110  gomp_barrier_wait_end (barrier, gomp_barrier_wait_start (barrier));
111}
112