/****************************************************************************
* sched/pthread_mutexunlock.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 <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_unlock
*
* Description:
* The pthread_mutex_unlock() function releases the mutex object referenced
* by mutex. The manner in which a mutex is released is dependent upon the
* mutex's type attribute. If there are threads blocked on the mutex object
* referenced by mutex when pthread_mutex_unlock() is called, resulting in
* the mutex becoming available, the scheduling policy is used to determine
* which thread shall acquire the mutex. (In the case of PTHREAD_MUTEX_RECURSIVE
* mutexes, the mutex becomes available when the count reaches zero and the
* calling thread no longer has any locks on this mutex).
*
* 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:
* None
*
* Return Value:
* None
*
* Assumptions:
*
****************************************************************************/
int pthread_mutex_unlock(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();
/* Does the calling thread own the semaphore? */
if (mutex->pid != (int)getpid())
{
/* No... return an error (default behavior is like PTHREAD_MUTEX_ERRORCHECK) */
sdbg("Holder=%d returning EPERM\n", mutex->pid);
ret = EPERM;
}
/* Yes, the caller owns the semaphore.. Is this a recursive mutex? */
#ifdef CONFIG_MUTEX_TYPES
else if (mutex->type == PTHREAD_MUTEX_RECURSIVE && mutex->nlocks > 1)
{
/* This is a recursive mutex and we there are multiple locks held. Retain
* the mutex lock, just decrement the count of locks held, and return
* success.
*/
mutex->nlocks--;
}
#endif
/* This is either a non-recursive mutex or is the outermost unlock of
* a recursive mutex.
*/
else
{
/* Nullify the pid and lock count then post the semaphore */
mutex->pid = 0;
#ifdef CONFIG_MUTEX_TYPES
mutex->nlocks = 0;
#endif
ret = pthread_givesemaphore((sem_t*)&mutex->sem);
}
sched_unlock();
}
sdbg("Returning %d\n", ret);
return ret;
}
