nuttx/libs/libc/semaphore/sem_init.c
2022-09-28 18:08:37 +08:00

134 lines
4.3 KiB
C

/****************************************************************************
* libs/libc/semaphore/sem_init.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <limits.h>
#include <errno.h>
#include <nuttx/semaphore.h>
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: nxsem_init
*
* Description:
* This function initializes the UNNAMED semaphore sem. Following a
* successful call to nxsem_init(), the semaphore may be used in subsequent
* calls to nxsem_wait(), nxsem_post(), and nxsem_trywait(). The semaphore
* remains usable until it is destroyed.
*
* Only sem itself may be used for performing synchronization. The result
* of referring to copies of sem in calls to nxsem_wait(), nxsem_trywait(),
* nxsem_post(), and nxsem_destroy() is undefined.
*
* Input Parameters:
* sem - Semaphore to be initialized
* pshared - Process sharing (not used)
* value - Semaphore initialization value
*
* Returned Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
*
****************************************************************************/
int nxsem_init(FAR sem_t *sem, int pshared, unsigned int value)
{
UNUSED(pshared);
/* Verify that a semaphore was provided and the count is within the valid
* range.
*/
if (sem != NULL && value <= SEM_VALUE_MAX)
{
/* Initialize the semaphore count */
sem->semcount = (int16_t)value;
/* Initialize semaphore wait list */
dq_init(&sem->waitlist);
/* Initialize to support priority inheritance */
#ifdef CONFIG_PRIORITY_INHERITANCE
sem->flags = 0;
# if CONFIG_SEM_PREALLOCHOLDERS > 0
sem->hhead = NULL;
# else
INITIALIZE_SEMHOLDER(&sem->holder[0]);
INITIALIZE_SEMHOLDER(&sem->holder[1]);
# endif
#endif
return OK;
}
return -EINVAL;
}
/****************************************************************************
* Name: sem_init
*
* Description:
* This function initializes the UNNAMED semaphore sem. Following a
* successful call to sem_init(), the semaphore may be used in subsequent
* calls to sem_wait(), sem_post(), and sem_trywait(). The semaphore
* remains usable until it is destroyed.
*
* Only sem itself may be used for performing synchronization. The result
* of referring to copies of sem in calls to sem_wait(), sem_trywait(),
* sem_post(), and sem_destroy() is undefined.
*
* Input Parameters:
* sem - Semaphore to be initialized
* pshared - Process sharing (not used)
* value - Semaphore initialization value
*
* Returned Value:
* This returns zero (OK) if successful. Otherwise, -1 (ERROR) is
* returned and the errno value is set appropriately.
*
****************************************************************************/
int sem_init(FAR sem_t *sem, int pshared, unsigned int value)
{
int ret;
ret = nxsem_init(sem, pshared, value);
if (ret < 0)
{
set_errno(-ret);
ret = ERROR;
}
return ret;
}