/****************************************************************************
* sched/pthread_mutextrylock.c
*
* Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <unistd.h>
#include <pthread.h>
#include <semaphore.h>
#include <sched.h>
#include <errno.h>
#include <debug.h>
#include "pthread_internal.h"
/****************************************************************************
* Definitions
****************************************************************************/
/****************************************************************************
* Private Type Declarations
****************************************************************************/
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: pthread_mutex_trylock
*
* Description:
* The function pthread_mutex_trylock() is identical to pthread_mutex_lock()
* except that if the mutex object referenced by mutex is currently locked
* (by any thread, including the current thread), the call returns immediately
* with the errno EBUSY.
*
* If a signal is delivered to a thread waiting for a mutex, upon return from
* the signal handler the thread resumes waiting for the mutex as if it was
* not interrupted.
*
* Parameters:
* mutex - A reference to the mutex to be locked.
*
* Return Value:
* 0 on success or an errno value on failure. Note that the errno EINTR
* is never returned by pthread_mutex_lock().
*
* Assumptions:
*
****************************************************************************/
int pthread_mutex_trylock(FAR pthread_mutex_t *mutex)
{
int ret = OK;
sdbg("mutex=0x%p\n", mutex);
if (!mutex)
{
ret = EINVAL;
}
else
{
/* Make sure the semaphore is stable while we make the following
* checks. This all needs to be one atomic action.
*/
sched_lock();
/* Try to get the semaphore. */
if (sem_trywait((sem_t*)&mutex->sem) == OK)
{
/* If we succussfully obtained the semaphore, then indicate
* that we own it.
*/
mutex->pid = (int)getpid();
}
/* Was it not available? */
else if (get_errno() == EAGAIN)
{
ret = EBUSY;
}
else
{
ret = EINVAL;
}
sched_unlock();
}
sdbg("Returning %d\n", ret);
return ret;
}
