forked from Archive/PX4-Autopilot
125 lines
4.6 KiB
C
125 lines
4.6 KiB
C
/****************************************************************************
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* lib/sem/sem_init.c
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*
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* Copyright (C) 2007-2009, 2011-2012 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 <sys/types.h>
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#include <limits.h>
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#include <semaphore.h>
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#include <errno.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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* Function: sem_init
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*
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* Description:
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* This function initializes the UNAMED semaphore sem. Following a
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* successful call to sem_init(), the semaophore may be used in subsequent
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* calls to sem_wait(), sem_post(), and sem_trywait(). The semaphore
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* remains usable until it is destroyed.
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*
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* Only sem itself may be used for performing synchronization. The result
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* of referring to copies of sem in calls to sem_wait(), sem_trywait(),
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* sem_post(), and sem_destroy() is undefined.
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*
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* Parameters:
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* sem - Semaphore to be initialized
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* pshared - Process sharing (not used)
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* value - Semaphore initialization value
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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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*
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****************************************************************************/
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int sem_init(FAR sem_t *sem, int pshared, unsigned int value)
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{
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/* Verify that a semaphore was provided and the count is within the valid
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* range.
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*/
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if (sem && value <= SEM_VALUE_MAX)
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{
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/* Initialize the seamphore count */
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sem->semcount = (int16_t)value;
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/* Initialize to support priority inheritance */
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#ifdef CONFIG_PRIORITY_INHERITANCE
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# if CONFIG_SEM_PREALLOCHOLDERS > 0
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sem->hlist.flink = NULL;
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# endif
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sem->hlist.holder = NULL;
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sem->hlist.counts = 0;
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#endif
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return OK;
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}
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else
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{
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set_errno(EINVAL);
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return ERROR;
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}
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}
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