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/* Copyright (C) 2005, 2008 Free Software Foundation, Inc.
Contributed by Richard Henderson <rth@redhat.com>.
This file is part of the GNU OpenMP Library (libgomp).
Libgomp is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
more details.
You should have received a copy of the GNU Lesser General Public License
along with libgomp; see the file COPYING.LIB. If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
MA 02110-1301, USA. */
/* As a special exception, if you link this library with other files, some
of which are compiled with GCC, to produce an executable, this library
does not by itself cause the resulting executable to be covered by the
GNU General Public License. This exception does not however invalidate
any other reasons why the executable file might be covered by the GNU
General Public License. */
/* This is a Linux specific implementation of a semaphore synchronization
mechanism for libgomp. This type is private to the library. This
implementation uses atomic instructions and the futex syscall. */
#include "wait.h"
void
gomp_sem_wait_slow (gomp_sem_t *sem)
{
while (1)
{
int val = __sync_val_compare_and_swap (sem, 0, -1);
if (val > 0)
{
if (__sync_bool_compare_and_swap (sem, val, val - 1))
return;
}
do_wait (sem, -1);
}
}
void
gomp_sem_post_slow (gomp_sem_t *sem)
{
int old, tmp = *sem, wake;
do
{
old = tmp;
wake = old > 0 ? old + 1 : 1;
tmp = __sync_val_compare_and_swap (sem, old, wake);
}
while (old != tmp);
futex_wake (sem, wake);
}
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