libgomp/config/linux/mutex.c

   1 /* Copyright (C) 2005 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 Lesser General Public License as published by
   8    the Free Software Foundation; either version 2.1 of the License, or
   9    (at your option) 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 Lesser General Public License for
  14    more details.
  15
  16    You should have received a copy of the GNU Lesser General Public License
  17    along with libgomp; see the file COPYING.LIB.  If not, write to the
  18    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  19    MA 02110-1301, USA.  */
  20
  21 /* As a special exception, if you link this library with other files, some
  22    of which are compiled with GCC, to produce an executable, this library
  23    does not by itself cause the resulting executable to be covered by the
  24    GNU General Public License.  This exception does not however invalidate
  25    any other reasons why the executable file might be covered by the GNU
  26    General Public License.  */
  27
  28 /* This is a Linux specific implementation of a mutex synchronization
  29    mechanism for libgomp.  This type is private to the library.  This
  30    implementation uses atomic instructions and the futex syscall.  */
  31
  32 #include "libgomp.h"
  33 #include "futex.h"
  34
  35
  36 void
  37 gomp_mutex_lock_slow (gomp_mutex_t *mutex)
  38 {
  39   do
  40     {
  41       int oldval = __sync_val_compare_and_swap (mutex, 1, 2);
  42       if (oldval != 0)
  43         futex_wait (mutex, 2);
  44     }
  45   while (!__sync_bool_compare_and_swap (mutex, 0, 2));
  46 }
  47
  48 void
  49 gomp_mutex_unlock_slow (gomp_mutex_t *mutex)
  50 {
  51   futex_wake (mutex, 1);
  52 }