118 lines
3.9 KiB
C
118 lines
3.9 KiB
C
/****************************************************************************
|
|
* sched/pthread/pthread_condsignal.c
|
|
*
|
|
* Copyright (C) 2007-2009, 2012 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 <pthread.h>
|
|
#include <errno.h>
|
|
#include <debug.h>
|
|
|
|
#include "pthread/pthread.h"
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: pthread_cond_signal
|
|
*
|
|
* Description:
|
|
* A thread can signal on a condition variable.
|
|
*
|
|
* Parameters:
|
|
* None
|
|
*
|
|
* Return Value:
|
|
* None
|
|
*
|
|
* Assumptions:
|
|
*
|
|
****************************************************************************/
|
|
|
|
int pthread_cond_signal(FAR pthread_cond_t *cond)
|
|
{
|
|
int ret = OK;
|
|
int sval;
|
|
|
|
sinfo("cond=0x%p\n", cond);
|
|
|
|
if (!cond)
|
|
{
|
|
ret = EINVAL;
|
|
}
|
|
else
|
|
{
|
|
/* Get the current value of the semaphore */
|
|
|
|
if (sem_getvalue((FAR sem_t *)&cond->sem, &sval) != OK)
|
|
{
|
|
ret = EINVAL;
|
|
}
|
|
|
|
/* If the value is less than zero (meaning that one or more
|
|
* thread is waiting), then post the condition semaphore.
|
|
* Only the highest priority waiting thread will get to execute
|
|
*/
|
|
|
|
else
|
|
{
|
|
/* One of my objectives in this design was to make pthread_cond_signal
|
|
* usable from interrupt handlers. However, from interrupt handlers,
|
|
* you cannot take the associated mutex before signaling the condition.
|
|
* As a result, I think that there could be a race condition with
|
|
* the following logic which assumes that the if sval < 0 then the
|
|
* thread is waiting. Without the mutex, there is no atomic, protected
|
|
* operation that will guarantee this to be so.
|
|
*/
|
|
|
|
sinfo("sval=%d\n", sval);
|
|
if (sval < 0)
|
|
{
|
|
sinfo("Signalling...\n");
|
|
ret = pthread_sem_give((FAR sem_t *)&cond->sem);
|
|
}
|
|
}
|
|
}
|
|
|
|
sinfo("Returning %d\n", ret);
|
|
return ret;
|
|
}
|
|
|
|
|