incubator-nuttx/fs/semaphore/sem_close.c

/****************************************************************************
 * fs/semaphore/sem_close.c
 *
 *   Copyright (C) 2014 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 <sched.h>
#include <errno.h>

#include <nuttx/kmalloc.h>
#include <nuttx/semaphore.h>
#include <nuttx/fs/fs.h>

#include "inode/inode.h"

#ifdef CONFIG_FS_NAMED_SEMAPHORES

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

/****************************************************************************
 * Name:  sem_close
 *
 * Description:
 *   This function is called to indicate that the calling task is finished
 *   with the specified named semaphore, 'sem'.  The sem_close() deallocates
 *   any system resources allocated by the system for this named semaphore.
 *
 *   If the semaphore has not been removed with a call to sem_unlink(), then
 *   sem_close() has no effect on the named semaphore.  However, when the
 *   named semaphore has been fully unlinked, the semaphore will vanish when
 *   the last task closes it.
 *
 * Parameters:
 *  sem - semaphore descriptor
 *
 * Return Value:
 *  0 (OK), or -1 (ERROR) if unsuccessful.
 *
 * Assumptions:
 *   - Care must be taken to avoid risking the deletion of a semaphore that
 *     another calling task has already locked.
 *   - sem_close must not be called for an un-named semaphore
 *
 ****************************************************************************/

int sem_close(FAR sem_t *sem)
{
  FAR struct nsem_inode_s *nsem;
  struct inode *inode ;

  DEBUGASSERT(sem);

  /* Upcast to get back to out internal representation */

  nsem = (FAR struct nsem_inode_s *)sem;
  DEBUGASSERT(nsem->ns_inode);
  inode = nsem->ns_inode;

  /* Decrement the reference count on the inode */

  inode_semtake();
  if (inode->i_crefs > 0)
    {
      inode->i_crefs--;
    }

  /* If the semaphore was previously unlinked and the reference count has
   * decremented to zero, then release the semaphore and delete the inode
   * now.
   */

  if (inode->i_crefs <= 0 && (inode->i_flags & FSNODEFLAG_DELETED) != 0)
    {
      /* Destroy the semaphore and free the container */

      sem_destroy(&nsem->ns_sem);
      group_free(NULL, nsem);

      /* Release and free the inode container.  If it has been properly
       * unlinked, then the peer pointer should be NULL.
       */

      inode_semgive();

      DEBUGASSERT(inode->i_peer == NULL);
      inode_free(inode);
      return OK;
    }

  inode_semgive();
  return OK;
}

#endif /* CONFIG_FS_NAMED_SEMAPHORES */