libgomp/config/posix/bar.c

   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
  36 void
  37 gomp_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
  49 void
  50 gomp_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
  64 void
  65 gomp_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
  72 void
  73 gomp_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
 107 void
 108 gomp_barrier_wait (gomp_barrier_t *barrier)
 109 {
 110   gomp_barrier_wait_end (barrier, gomp_barrier_wait_start (barrier));
 111 }