nuttx/fs/semaphore/sem_close.c

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/****************************************************************************
* 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
*
* Returned 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();
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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 */
nxsem_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();
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DEBUGASSERT(inode->i_peer == NULL);
inode_free(inode);
return OK;
}
inode_semgive();
return OK;
}
#endif /* CONFIG_FS_NAMED_SEMAPHORES */