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/* sem_post -- post to a POSIX semaphore. Generic futex-using version.
Copyright (C) 2003, 2004, 2007, 2008 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Jakub Jelinek <jakub@redhat.com>, 2003.
The GNU C Library 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.
The GNU C Library 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 the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <internaltypes.h>
#include <semaphore.h>
#include <tls.h>
int
sem_post (sem_t *sem)
{
struct new_sem *isem = (struct new_sem *) sem;
__typeof (isem->value) cur;
do
{
cur = isem->value;
if (isem->value == SEM_VALUE_MAX)
{
__set_errno (EOVERFLOW);
return -1;
}
}
while (atomic_compare_and_exchange_bool_acq (&isem->value, cur + 1, cur));
atomic_full_barrier ();
if (isem->nwaiters > 0)
{
int err = lll_futex_wake (&isem->value, 1,
isem->private ^ FUTEX_PRIVATE_FLAG);
if (__builtin_expect (err, 0) < 0)
{
__set_errno (-err);
return -1;
}
}
return 0;
}
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