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/* Post a semaphore. Generic version.
Copyright (C) 2005-2020 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 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
<https://www.gnu.org/licenses/>. */
#include <semaphore.h>
#include <assert.h>
#include <pt-internal.h>
int
__sem_post (sem_t *sem)
{
struct __pthread *wakeup;
__pthread_spin_wait (&sem->__lock);
if (sem->__value > 0)
/* Do a quick up. */
{
if (sem->__value == SEM_VALUE_MAX)
{
__pthread_spin_unlock (&sem->__lock);
errno = EOVERFLOW;
return -1;
}
assert (sem->__queue == NULL);
sem->__value++;
__pthread_spin_unlock (&sem->__lock);
return 0;
}
if (sem->__queue == NULL)
/* 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;
}
libpthread_hidden_def (__sem_post)
strong_alias (__sem_post, sem_post);
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