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/* Post a semaphore. Generic version.
Copyright (C) 2005 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <semaphore.h>
#include <assert.h>
#include <pt-internal.h>
int
__sem_post (sem_t *sem)
{
struct __pthread *wakeup;
__pthread_spin_lock (&sem->__lock);
if (sem->__value > 0)
/* Do a quick up. */
{
assert (! sem->__queue);
sem->__value ++;
__pthread_spin_unlock (&sem->__lock);
return 0;
}
if (! sem->__queue)
/* No one waiting. */
{
sem->__value = 1;
__pthread_spin_unlock (&sem->__lock);
return 0;
}
/* Wake someone up. */
/* First dequeue someone. */
wakeup = sem->__queue;
__pthread_dequeue (wakeup);
/* Then drop the lock and transfer control. */
__pthread_spin_unlock (&sem->__lock);
__pthread_wakeup (wakeup);
return 0;
}
weak_alias (__sem_post, sem_post);
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