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bar.c revision 1.1 
      1 /* Copyright (C) 2005, 2008, 2009 Free Software Foundation, Inc.
      2    Contributed by Richard Henderson <rth (at) 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 General Public License as published by
      8    the Free Software Foundation; either version 3, or (at your option)
      9    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 General Public License for
     14    more details.
     15 
     16    Under Section 7 of GPL version 3, you are granted additional
     17    permissions described in the GCC Runtime Library Exception, version
     18    3.1, as published by the Free Software Foundation.
     19 
     20    You should have received a copy of the GNU General Public License and
     21    a copy of the GCC Runtime Library Exception along with this program;
     22    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
     23    <http://www.gnu.org/licenses/>.  */
     24 
     25 /* This is the default implementation of a barrier synchronization mechanism
     26    for libgomp.  This type is private to the library.  Note that we rely on
     27    being able to adjust the barrier count while threads are blocked, so the
     28    POSIX pthread_barrier_t won't work.  */
     29 
     30 #include "libgomp.h"
     31 
     32 
     33 void
     34 gomp_barrier_init (gomp_barrier_t *bar, unsigned count)
     35 {
     36   gomp_mutex_init (&bar->mutex1);
     37 #ifndef HAVE_SYNC_BUILTINS
     38   gomp_mutex_init (&bar->mutex2);
     39 #endif
     40   gomp_sem_init (&bar->sem1, 0);
     41   gomp_sem_init (&bar->sem2, 0);
     42   bar->total = count;
     43   bar->arrived = 0;
     44   bar->generation = 0;
     45 }
     46 
     47 void
     48 gomp_barrier_destroy (gomp_barrier_t *bar)
     49 {
     50   /* Before destroying, make sure all threads have left the barrier.  */
     51   gomp_mutex_lock (&bar->mutex1);
     52   gomp_mutex_unlock (&bar->mutex1);
     53 
     54   gomp_mutex_destroy (&bar->mutex1);
     55 #ifndef HAVE_SYNC_BUILTINS
     56   gomp_mutex_destroy (&bar->mutex2);
     57 #endif
     58   gomp_sem_destroy (&bar->sem1);
     59   gomp_sem_destroy (&bar->sem2);
     60 }
     61 
     62 void
     63 gomp_barrier_reinit (gomp_barrier_t *bar, unsigned count)
     64 {
     65   gomp_mutex_lock (&bar->mutex1);
     66   bar->total = count;
     67   gomp_mutex_unlock (&bar->mutex1);
     68 }
     69 
     70 void
     71 gomp_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
     72 {
     73   unsigned int n;
     74 
     75   if (state & 1)
     76     {
     77       n = --bar->arrived;
     78       if (n > 0)
     79 	{
     80 	  do
     81 	    gomp_sem_post (&bar->sem1);
     82 	  while (--n != 0);
     83 	  gomp_sem_wait (&bar->sem2);
     84 	}
     85       gomp_mutex_unlock (&bar->mutex1);
     86     }
     87   else
     88     {
     89       gomp_mutex_unlock (&bar->mutex1);
     90       gomp_sem_wait (&bar->sem1);
     91 
     92 #ifdef HAVE_SYNC_BUILTINS
     93       n = __sync_add_and_fetch (&bar->arrived, -1);
     94 #else
     95       gomp_mutex_lock (&bar->mutex2);
     96       n = --bar->arrived;
     97       gomp_mutex_unlock (&bar->mutex2);
     98 #endif
     99 
    100       if (n == 0)
    101 	gomp_sem_post (&bar->sem2);
    102     }
    103 }
    104 
    105 void
    106 gomp_barrier_wait (gomp_barrier_t *barrier)
    107 {
    108   gomp_barrier_wait_end (barrier, gomp_barrier_wait_start (barrier));
    109 }
    110 
    111 void
    112 gomp_team_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state)
    113 {
    114   unsigned int n;
    115 
    116   if (state & 1)
    117     {
    118       n = --bar->arrived;
    119       struct gomp_thread *thr = gomp_thread ();
    120       struct gomp_team *team = thr->ts.team;
    121 
    122       if (team->task_count)
    123 	{
    124 	  gomp_barrier_handle_tasks (state);
    125 	  if (n > 0)
    126 	    gomp_sem_wait (&bar->sem2);
    127 	  gomp_mutex_unlock (&bar->mutex1);
    128 	  return;
    129 	}
    130 
    131       bar->generation = state + 3;
    132       if (n > 0)
    133 	{
    134 	  do
    135 	    gomp_sem_post (&bar->sem1);
    136 	  while (--n != 0);
    137 	  gomp_sem_wait (&bar->sem2);
    138 	}
    139       gomp_mutex_unlock (&bar->mutex1);
    140     }
    141   else
    142     {
    143       gomp_mutex_unlock (&bar->mutex1);
    144       do
    145 	{
    146 	  gomp_sem_wait (&bar->sem1);
    147 	  if (bar->generation & 1)
    148 	    gomp_barrier_handle_tasks (state);
    149 	}
    150       while (bar->generation != state + 4);
    151 
    152 #ifdef HAVE_SYNC_BUILTINS
    153       n = __sync_add_and_fetch (&bar->arrived, -1);
    154 #else
    155       gomp_mutex_lock (&bar->mutex2);
    156       n = --bar->arrived;
    157       gomp_mutex_unlock (&bar->mutex2);
    158 #endif
    159 
    160       if (n == 0)
    161 	gomp_sem_post (&bar->sem2);
    162     }
    163 }
    164 
    165 void
    166 gomp_team_barrier_wait (gomp_barrier_t *barrier)
    167 {
    168   gomp_team_barrier_wait_end (barrier, gomp_barrier_wait_start (barrier));
    169 }
    170 
    171 void
    172 gomp_team_barrier_wake (gomp_barrier_t *bar, int count)
    173 {
    174   if (count == 0)
    175     count = bar->total - 1;
    176   while (count-- > 0)
    177     gomp_sem_post (&bar->sem1);
    178 }
    179