libgomp/critical.c

   1 /* Copyright (C) 2005-2021 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 #if !GOMP_MUTEX_INIT_0
 119 static void __attribute__((constructor))
 120 initialize_critical (void)
 121 {
 122   gomp_mutex_init (&default_lock);
 123 #ifndef HAVE_SYNC_BUILTINS
 124   gomp_mutex_init (&create_lock_lock);
 125 #endif
 126 }
 127 #endif