libgomp/critical.c

   1 /* Copyright (C) 2005, 2009 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 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 file handles the CRITICAL construct.  */
  26
  27 #include "libgomp.h"
  28 #include <stdlib.h>
  29
  30
  31 static gomp_mutex_t default_lock;
  32
  33 void
  34 GOMP_critical_start (void)
  35 {
  36   gomp_mutex_lock (&default_lock);
  37 }
  38
  39 void
  40 GOMP_critical_end (void)
  41 {
  42   gomp_mutex_unlock (&default_lock);
  43 }
  44
  45 #ifndef HAVE_SYNC_BUILTINS
  46 static gomp_mutex_t create_lock_lock;
  47 #endif
  48
  49 void
  50 GOMP_critical_name_start (void **pptr)
  51 {
  52   gomp_mutex_t *plock;
  53
  54   /* If a mutex fits within the space for a pointer, and is zero initialized,
  55      then use the pointer space directly.  */
  56   if (GOMP_MUTEX_INIT_0
  57       && sizeof (gomp_mutex_t) <= sizeof (void *)
  58       && __alignof (gomp_mutex_t) <= sizeof (void *))
  59     plock = (gomp_mutex_t *)pptr;
  60
  61   /* Otherwise we have to be prepared to malloc storage.  */
  62   else
  63     {
  64       plock = *pptr;
  65
  66       if (plock == NULL)
  67         {
  68 #ifdef HAVE_SYNC_BUILTINS
  69           gomp_mutex_t *nlock = gomp_malloc (sizeof (gomp_mutex_t));
  70           gomp_mutex_init (nlock);
  71
  72           plock = __sync_val_compare_and_swap (pptr, NULL, nlock);
  73           if (plock != NULL)
  74             {
  75               gomp_mutex_destroy (nlock);
  76               free (nlock);
  77             }
  78           else
  79             plock = nlock;
  80 #else
  81           gomp_mutex_lock (&create_lock_lock);
  82           plock = *pptr;
  83           if (plock == NULL)
  84             {
  85               plock = gomp_malloc (sizeof (gomp_mutex_t));
  86               gomp_mutex_init (plock);
  87               __sync_synchronize ();
  88               *pptr = plock;
  89             }
  90           gomp_mutex_unlock (&create_lock_lock);
  91 #endif
  92         }
  93     }
  94
  95   gomp_mutex_lock (plock);
  96 }
  97
  98 void
  99 GOMP_critical_name_end (void **pptr)
 100 {
 101   gomp_mutex_t *plock;
 102
 103   /* If a mutex fits within the space for a pointer, and is zero initialized,
 104      then use the pointer space directly.  */
 105   if (GOMP_MUTEX_INIT_0
 106       && sizeof (gomp_mutex_t) <= sizeof (void *)
 107       && __alignof (gomp_mutex_t) <= sizeof (void *))
 108     plock = (gomp_mutex_t *)pptr;
 109   else
 110     plock = *pptr;
 111
 112   gomp_mutex_unlock (plock);
 113 }
 114
 115 /* This mutex is used when atomic operations don't exist for the target
 116    in the mode requested.  The result is not globally atomic, but works so
 117    long as all parallel references are within #pragma omp atomic directives.
 118    According to responses received from omp@openmp.org, appears to be within
 119    spec.  Which makes sense, since that's how several other compilers
 120    handle this situation as well.  */
 121
 122 static gomp_mutex_t atomic_lock;
 123
 124 void
 125 GOMP_atomic_start (void)
 126 {
 127   gomp_mutex_lock (&atomic_lock);
 128 }
 129
 130 void
 131 GOMP_atomic_end (void)
 132 {
 133   gomp_mutex_unlock (&atomic_lock);
 134 }
 135
 136 #if !GOMP_MUTEX_INIT_0
 137 static void __attribute__((constructor))
 138 initialize_critical (void)
 139 {
 140   gomp_mutex_init (&default_lock);
 141   gomp_mutex_init (&atomic_lock);
 142 #ifndef HAVE_SYNC_BUILTINS
 143   gomp_mutex_init (&create_lock_lock);
 144 #endif
 145 }
 146 #endif