146 lines
4.9 KiB
C
146 lines
4.9 KiB
C
/****************************************************************************
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* sched/pthread_mutextrylock.c
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*
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* Copyright (C) 2007, 2008 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
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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 <sys/types.h>
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#include <unistd.h>
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#include <pthread.h>
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#include <semaphore.h>
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#include <sched.h>
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#include <errno.h>
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#include <debug.h>
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#include "pthread_internal.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: pthread_mutex_trylock
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*
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* Description:
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* The function pthread_mutex_trylock() is identical to pthread_mutex_lock()
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* except that if the mutex object referenced by mutex is currently locked
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* (by any thread, including the current thread), the call returns immediately
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* with the errno EBUSY.
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*
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* If a signal is delivered to a thread waiting for a mutex, upon return from
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* the signal handler the thread resumes waiting for the mutex as if it was
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* not interrupted.
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*
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* Parameters:
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* mutex - A reference to the mutex to be locked.
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*
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* Return Value:
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* 0 on success or an errno value on failure. Note that the errno EINTR
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* is never returned by pthread_mutex_lock().
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*
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* Assumptions:
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*
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****************************************************************************/
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int pthread_mutex_trylock(FAR pthread_mutex_t *mutex)
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{
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int ret = OK;
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sdbg("mutex=0x%p\n", mutex);
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if (!mutex)
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{
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ret = EINVAL;
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}
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else
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{
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/* Make sure the semaphore is stable while we make the following
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* checks. This all needs to be one atomic action.
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*/
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sched_lock();
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/* Try to get the semaphore. */
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if (sem_trywait((sem_t*)&mutex->sem) == OK)
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{
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/* If we succussfully obtained the semaphore, then indicate
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* that we own it.
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*/
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mutex->pid = (int)getpid();
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}
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/* Was it not available? */
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else if (*get_errno_ptr() == EAGAIN)
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{
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ret = EBUSY;
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}
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else
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{
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ret = EINVAL;
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}
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sched_unlock();
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}
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sdbg("Returning %d\n", ret);
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return ret;
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}
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