141 lines
5.0 KiB
C
141 lines
5.0 KiB
C
/****************************************************************************
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* sched/sem_close.c
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*
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* Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <errno.h>
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#include <semaphore.h>
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#include <sched.h>
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#include "os_internal.h"
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#include "sem_internal.h"
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/****************************************************************************
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* Definitions
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****************************************************************************/
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/****************************************************************************
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* Private Type Declarations
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****************************************************************************/
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/****************************************************************************
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* Global Variables
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****************************************************************************/
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/****************************************************************************
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* Private Variables
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****************************************************************************/
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: sem_close
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*
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* Description:
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* This function is called to indicate that the calling task is finished
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* with the specified named semaphore, 'sem'. The sem_close() deallocates
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* any system resources allocated by the system for this named semaphore.
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*
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* If the semaphore has not been removed with a call to sem_unlink(), then
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* sem_close() has no effect on the named semaphore. However, when the
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* named semaphore has been fully unlinked, the semaphore will vanish when
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* the last task closes it.
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*
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* Parameters:
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* sem - semaphore descriptor
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*
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* Return Value:
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* 0 (OK), or -1 (ERROR) if unsuccessful.
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*
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* Assumptions:
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* - Care must be taken to avoid risking the deletion of a semaphore that
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* another calling task has already locked.
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* - sem_close must not be called for an un-named semaphore
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*
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****************************************************************************/
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int sem_close(FAR sem_t *sem)
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{
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FAR nsem_t *psem;
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int ret = ERROR;
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/* Verify the inputs */
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if (sem)
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{
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sched_lock();
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/* Search the list of named semaphores */
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for (psem = (FAR nsem_t*)g_nsems.head;
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((psem) && (sem != &psem->sem));
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psem = psem->flink);
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/* Check if we found it */
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if (psem)
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{
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/* Decrement the count of sem_open connections to this semaphore */
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if (psem->nconnect) psem->nconnect--;
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/* If the semaphore is no long connected to any processes AND the
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* semaphore was previously unlinked, then deallocate it.
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*/
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if (!psem->nconnect && psem->unlinked)
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{
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dq_rem((FAR dq_entry_t*)psem, &g_nsems);
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sched_free(psem);
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}
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ret = OK;
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}
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sched_unlock();
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}
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return ret;
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}
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