px4_autopilot/nuttx/sched/sem_destroy.c

/****************************************************************************
 * lib/semaphore/sem_destroy.c
 *
 *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <semaphore.h>
#include <errno.h>

#include "sem_internal.h"

/****************************************************************************
 * Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Type Declarations
 ****************************************************************************/

/****************************************************************************
 * Global Variables
 ****************************************************************************/

/****************************************************************************
 * Private Variables
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: sem_destroy
 *
 * Description:
 *   This function is used to destroy the un-named semaphore indicated by
 *   'sem'.  Only a semaphore that was created using sem_init() may be
 *   destroyed using sem_destroy(); the effect of calling sem_destroy() with
 *   a named semaphore is undefined.  The effect of subsequent use of the
 *   semaphore sem is undefined until sem is re-initialized by another call
 *   to sem_init().
 *
 *   The effect of destroying a semaphore upon which other processes are
 *   currently blocked is undefined.
 *
 * Parameters:
 *   sem - Semaphore to be destroyed.
 *
 * Return Value:
 *   0 (OK), or -1 (ERROR) if unsuccessful.
 *
 * Assumptions:
 *
 ****************************************************************************/

int sem_destroy (FAR sem_t *sem)
{
  /* Assure a valid semaphore is specified */

  if (sem)
    {
      /* There is really no particular action that we need
       * take to destroy a semaphore.  We will just reset
       * the count to some reasonable value (1) and release
       * ownership.
       *
       * Check if other threads are waiting on the semaphore.
       * In this case, the behavior is undefined.  We will:
       * leave the count unchanged but still return OK.
       */

      if (sem->semcount >= 0)
        {
          sem->semcount = 1;
        }

      /* Release holders of the semaphore */

      sem_destroyholder(sem);
      return OK;
    }
  else
    {
      errno = -EINVAL;
      return ERROR;
    }
}