1  /* Copyright (C) 2005-2023 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