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/* Copyright (C) 2005, 2008, 2009 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 General Public License as published by
the Free Software Foundation; either version 3, 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 General Public License for
more details.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
/* 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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