/* Post a semaphore.  Generic version.

   Copyright (C) 2005-2018 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

   <http://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_lock (&sem->__lock);

  if (sem->__value > 0)

    /* Do a quick up.  */

    {

      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;

}

strong_alias (__sem_post, sem_post);