* sched/semaphore/sem_destroy.c
*
* SPDX-License-Identifier: Apache-2.0
*
* 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 <errno.h>
#include <assert.h>
#include "semaphore/semaphore.h"
* Public Functions
****************************************************************************/
* Name: nxsem_destroy
*
* Description:
* This function is used to destroy the un-named semaphore indicated by
* 'sem'. Only a semaphore that was created using nxsem_init() may be
* destroyed using nxsem_destroy(); the effect of calling nxsem_destroy()
* with a named semaphore is undefined. The effect of subsequent use of
* the semaphore sem is undefined until sem is re-initialized by another
* call to nxsem_init().
*
* The effect of destroying a semaphore upon which other processes are
* currently blocked is undefined.
*
* Input Parameters:
* sem - Semaphore to be destroyed.
*
* 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_destroy(FAR sem_t *sem)
{
int32_t old;
bool mutex = NXSEM_IS_MUTEX(sem);
FAR atomic_t *val = mutex ? NXSEM_MHOLDER(sem) : NXSEM_COUNT(sem);
int32_t new = mutex ? NXSEM_NO_MHOLDER : 1;
DEBUGASSERT(sem != NULL);
* take to destroy a semaphore. We will just reset
* the count to some reasonable value (0) and release
* ownership.
*
* Check if other threads are waiting on the semaphore.
* In this case, the behavior is undefined. We will:
* leave the count unchanged but still return OK.
*/
old = atomic_read(val);
do
{
if ((mutex && NXSEM_MBLOCKING(old)) ||
(!mutex && old < 0))
{
break;
}
}
while (!atomic_try_cmpxchg_release(val, &old, new));
nxsem_destroyholder(sem);
return OK;
}