/****************************************************************************
* sched/sem_waitirq.c
*
* Copyright (C) 2007-2010 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 <sched.h>
#include <errno.h>
#include <nuttx/arch.h>
#include "sem_internal.h"
/****************************************************************************
* Definitions
****************************************************************************/
/****************************************************************************
* Private Type Declarations
****************************************************************************/
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: sem_waitirq
*
* Description:
* This function is called when a signal is received by a task that is
* waiting on a semaphore. According to the POSIX spec, "...the calling
* thread shall not return from the call to [sem_wait] until it either
* locks the semaphore or the call is interrupted by a signal."
*
* Parameters:
* wtcb - A pointer to the TCB of the task that is waiting on a
* semphaphore, but has received a signal or timeout instead.
* errcode - EINTR if the semaphore wait was awakened by a signal;
* ETIMEDOUT if awakened by a timeout
*
* Return Value:
* None
*
* Assumptions:
*
****************************************************************************/
void sem_waitirq(FAR _TCB *wtcb, int errcode)
{
irqstate_t saved_state;
/* Disable interrupts. This is necessary (unfortunately) because an
* interrupt handler may attempt to post the semaphore while we are
* doing this.
*/
saved_state = irqsave();
/* It is possible that an interrupt/context switch beat us to the punch
* and already changed the task's state.
*/
if (wtcb->task_state == TSTATE_WAIT_SEM)
{
sem_t *sem = wtcb->waitsem;
DEBUGASSERT(sem != NULL && sem->semcount < 0);
/* Restore the correct priority of all threads that hold references
* to this semaphore.
*/
sem_canceled(wtcb, sem);
/* And increment the count on the semaphore. This releases the count
* that was taken by sem_post(). This count decremented the semaphore
* count to negative and caused the thread to be blocked in the first
* place.
*/
sem->semcount++;
/* Indicate that the semaphore wait is over. */
wtcb->waitsem = NULL;
/* Mark the errno value for the thread. */
wtcb->pterrno = errcode;
/* Restart the task. */
up_unblock_task(wtcb);
}
/* Interrupts may now be enabled. */
irqrestore(saved_state);
}
