/************************************************************
* sem_close.c
*
* Copyright (C) 2007 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* 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 Gregory Nutt 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 <sys/types.h>
#include <errno.h>
#include <semaphore.h>
#include <sched.h>
#include "os_internal.h"
#include "sem_internal.h"
/************************************************************
* Compilation Switches
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/************************************************************
* Definitions
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/************************************************************
* Private Type Declarations
************************************************************/
/************************************************************
* Global Variables
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/************************************************************
* Private Variables
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/************************************************************
* Private Functions
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/************************************************************
* Public Functions
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/************************************************************
* Function: 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 nsem_t *psem;
int ret = ERROR;
/* Verify the inputs */
if (sem)
{
sched_lock();
/* Search the list of named semaphores */
for (psem = (FAR nsem_t*)g_nsems.head;
((psem) && (sem != &psem->sem));
psem = psem->flink);
/* Check if we found it */
if (psem)
{
/* Decrement the count of sem_open connections to this semaphore */
if (psem->nconnect) psem->nconnect--;
/* If the semaphore is no long connected to any processes AND the
* semaphore was previously unlinked, then deallocate it.
*/
if (!psem->nconnect && psem->unlinked)
{
dq_rem((FAR dq_entry_t*)psem, &g_nsems);
sched_free(psem);
}
ret = OK;
}
sched_unlock();
}
return ret;
}
