140 lines
4.4 KiB
C
140 lines
4.4 KiB
C
/****************************************************************************
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* libs/libc/semaphore/sem_init.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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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 <assert.h>
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#include <limits.h>
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#include <errno.h>
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#include <nuttx/semaphore.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: nxsem_init
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*
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* Description:
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* This function initializes the UNNAMED semaphore sem. Following a
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* successful call to nxsem_init(), the semaphore may be used in subsequent
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* calls to nxsem_wait(), nxsem_post(), and nxsem_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 nxsem_wait(), nxsem_trywait(),
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* nxsem_post(), and nxsem_destroy() is undefined.
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*
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* Input 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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* Returned Value:
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* This is an internal OS interface and should not be used by applications.
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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*
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****************************************************************************/
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int nxsem_init(FAR sem_t *sem, int pshared, unsigned int value)
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{
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UNUSED(pshared);
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DEBUGASSERT(sem != NULL && value <= SEM_VALUE_MAX);
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/* Initialize the semaphore count */
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sem->semcount = (int16_t)value;
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/* Initialize semaphore wait list */
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dq_init(&sem->waitlist);
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/* Initialize to support priority inheritance */
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sem->flags = 0;
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#ifdef CONFIG_PRIORITY_INHERITANCE
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# if CONFIG_SEM_PREALLOCHOLDERS > 0
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sem->hhead = NULL;
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# else
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INITIALIZE_SEMHOLDER(&sem->holder);
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# endif
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#endif
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return OK;
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}
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/****************************************************************************
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* Name: sem_init
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*
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* Description:
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* This function initializes the UNNAMED semaphore sem. Following a
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* successful call to sem_init(), the semaphore 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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* Input 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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* Returned Value:
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* This returns zero (OK) if successful. Otherwise, -1 (ERROR) is
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* returned and the errno value is set appropriately.
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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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int ret;
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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 == NULL || value > SEM_VALUE_MAX)
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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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ret = nxsem_init(sem, pshared, value);
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if (ret < 0)
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{
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set_errno(-ret);
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ret = ERROR;
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}
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return ret;
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}
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