text: /****************************************************************************
   * 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
  
  /****************************************************************************
   * Pre-processor Definitions
   ****************************************************************************/
  
  /****************************************************************************
   * Private Type Declarations
   ****************************************************************************/
  
  /****************************************************************************
   * Global Variables
   ****************************************************************************/
  
  /****************************************************************************
   * Private Variables
   ****************************************************************************/
  
  /****************************************************************************
   * Private Functions
   ****************************************************************************/
  
  /****************************************************************************
   * 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 */
  