libgomp/critical.c

   1 /* Copyright (C) 2005-2016 Free Software Foundation, Inc.
   2    Contributed by Richard Henderson <rth@redhat.com>.
   3
   4    This file is part of the GNU Offloading and Multi Processing Library
   5    (libgomp).
   6
   7    Libgomp is free software; you can redistribute it and/or modify it
   8    under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3, or (at your option)
  10    any later version.
  11
  12    Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
  13    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  14    FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  15    more details.
  16
  17    Under Section 7 of GPL version 3, you are granted additional
  18    permissions described in the GCC Runtime Library Exception, version
  19    3.1, as published by the Free Software Foundation.
  20
  21    You should have received a copy of the GNU General Public License and
  22    a copy of the GCC Runtime Library Exception along with this program;
  23    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24    <http://www.gnu.org/licenses/>.  */
  25
  26 /* This file handles the CRITICAL construct.  */
  27
  28 #include "libgomp.h"
  29 #include <stdlib.h>
  30
  31
  32 static gomp_mutex_t default_lock;
  33
  34 void
  35 GOMP_critical_start (void)
  36 {
  37   /* There is an implicit flush on entry to a critical region. */
  38   __atomic_thread_fence (MEMMODEL_RELEASE);
  39   gomp_mutex_lock (&default_lock);
  40 }
  41
  42 void
  43 GOMP_critical_end (void)
  44 {
  45   gomp_mutex_unlock (&default_lock);
  46 }
  47
  48 #ifndef HAVE_SYNC_BUILTINS
  49 static gomp_mutex_t create_lock_lock;
  50 #endif
  51
  52 void
  53 GOMP_critical_name_start (void **pptr)
  54 {
  55   gomp_mutex_t *plock;
  56
  57   /* If a mutex fits within the space for a pointer, and is zero initialized,
  58      then use the pointer space directly.  */
  59   if (GOMP_MUTEX_INIT_0
  60       && sizeof (gomp_mutex_t) <= sizeof (void *)
  61       && __alignof (gomp_mutex_t) <= sizeof (void *))
  62     plock = (gomp_mutex_t *)pptr;
  63
  64   /* Otherwise we have to be prepared to malloc storage.  */
  65   else
  66     {
  67       plock = *pptr;
  68
  69       if (plock == NULL)
  70         {
  71 #ifdef HAVE_SYNC_BUILTINS
  72           gomp_mutex_t *nlock = gomp_malloc (sizeof (gomp_mutex_t));
  73           gomp_mutex_init (nlock);
  74
  75           plock = __sync_val_compare_and_swap (pptr, NULL, nlock);
  76           if (plock != NULL)
  77             {
  78               gomp_mutex_destroy (nlock);
  79               free (nlock);
  80             }
  81           else
  82             plock = nlock;
  83 #else
  84           gomp_mutex_lock (&create_lock_lock);
  85           plock = *pptr;
  86           if (plock == NULL)
  87             {
  88               plock = gomp_malloc (sizeof (gomp_mutex_t));
  89               gomp_mutex_init (plock);
  90               __sync_synchronize ();
  91               *pptr = plock;
  92             }
  93           gomp_mutex_unlock (&create_lock_lock);
  94 #endif
  95         }
  96     }
  97
  98   gomp_mutex_lock (plock);
  99 }
 100
 101 void
 102 GOMP_critical_name_end (void **pptr)
 103 {
 104   gomp_mutex_t *plock;
 105
 106   /* If a mutex fits within the space for a pointer, and is zero initialized,
 107      then use the pointer space directly.  */
 108   if (GOMP_MUTEX_INIT_0
 109       && sizeof (gomp_mutex_t) <= sizeof (void *)
 110       && __alignof (gomp_mutex_t) <= sizeof (void *))
 111     plock = (gomp_mutex_t *)pptr;
 112   else
 113     plock = *pptr;
 114
 115   gomp_mutex_unlock (plock);
 116 }
 117
 118 /* This mutex is used when atomic operations don't exist for the target
 119    in the mode requested.  The result is not globally atomic, but works so
 120    long as all parallel references are within #pragma omp atomic directives.
 121    According to responses received from omp@openmp.org, appears to be within
 122    spec.  Which makes sense, since that's how several other compilers
 123    handle this situation as well.  */
 124
 125 static gomp_mutex_t atomic_lock;
 126
 127 void
 128 GOMP_atomic_start (void)
 129 {
 130   gomp_mutex_lock (&atomic_lock);
 131 }
 132
 133 void
 134 GOMP_atomic_end (void)
 135 {
 136   gomp_mutex_unlock (&atomic_lock);
 137 }
 138
 139 #if !GOMP_MUTEX_INIT_0
 140 static void __attribute__((constructor))
 141 initialize_critical (void)
 142 {
 143   gomp_mutex_init (&default_lock);
 144   gomp_mutex_init (&atomic_lock);
 145 #ifndef HAVE_SYNC_BUILTINS
 146   gomp_mutex_init (&create_lock_lock);
 147 #endif
 148 }
 149 #endif