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b6f2729730
This puts the mutex support fully inside nxsem, allowing locking the mutex and setting the holder with single atomic operation. This enables fast mutex locking from userspace, avoiding taking critical_sections, which may be heavy in SMP and cleanup of nxmutex library in the future. Signed-off-by: Jukka Laitinen <jukka.laitinen@tii.ae>
96 lines
3.3 KiB
C
96 lines
3.3 KiB
C
/****************************************************************************
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* sched/semaphore/sem_destroy.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 <errno.h>
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#include "semaphore/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_destroy
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*
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* Description:
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* This function is used to destroy the un-named semaphore indicated by
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* 'sem'. Only a semaphore that was created using nxsem_init() may be
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* destroyed using nxsem_destroy(); the effect of calling nxsem_destroy()
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* with a named semaphore is undefined. The effect of subsequent use of
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* the semaphore sem is undefined until sem is re-initialized by another
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* call to nxsem_init().
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*
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* The effect of destroying a semaphore upon which other processes are
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* currently blocked is undefined.
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*
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* Input Parameters:
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* sem - Semaphore to be destroyed.
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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_destroy(FAR sem_t *sem)
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{
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int32_t old;
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bool mutex = NXSEM_IS_MUTEX(sem);
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FAR atomic_t *val = mutex ? NXSEM_MHOLDER(sem) : NXSEM_COUNT(sem);
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int32_t new = mutex ? NXSEM_NO_MHOLDER : 1;
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DEBUGASSERT(sem != NULL);
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/* There is really no particular action that we need
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* take to destroy a semaphore. We will just reset
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* the count to some reasonable value (0) and release
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* ownership.
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*
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* Check if other threads are waiting on the semaphore.
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* In this case, the behavior is undefined. We will:
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* leave the count unchanged but still return OK.
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*/
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old = atomic_read(val);
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do
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{
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if ((mutex && NXSEM_MBLOCKING(old)) ||
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(!mutex && old < 0))
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{
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break;
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}
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}
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while (!atomic_try_cmpxchg_release(val, &old, new));
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/* Release holders of the semaphore */
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nxsem_destroyholder(sem);
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return OK;
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}
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