145 lines
4.9 KiB
C
145 lines
4.9 KiB
C
/****************************************************************************
|
|
* sched/sem_trywait.c
|
|
*
|
|
* Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
|
|
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
|
|
*
|
|
* 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 <stdbool.h>
|
|
#include <semaphore.h>
|
|
#include <sched.h>
|
|
#include <errno.h>
|
|
#include <nuttx/arch.h>
|
|
|
|
#include "os_internal.h"
|
|
#include "sem_internal.h"
|
|
|
|
/****************************************************************************
|
|
* Pre-processor Definitions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Private Type Declarations
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Global Variables
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Private Variables
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Private Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Function: sem_trywait
|
|
*
|
|
* Description:
|
|
* This function locks the specified semaphore only if the
|
|
* semaphore is currently not locked. Otherwise, it locks
|
|
* the semaphore. In either case, the call returns without
|
|
* blocking.
|
|
*
|
|
* Parameters:
|
|
* sem - the semaphore descriptor
|
|
*
|
|
* Return Value:
|
|
* 0 (OK) or -1 (ERROR) if unsuccessful
|
|
* If this function returns -1 (ERROR), then the cause
|
|
* of the failure will be reported in "errno" as:
|
|
* - EINVAL: Invalid attempt to get the semaphore
|
|
* - EAGAIN: The semaphore is not available.
|
|
*
|
|
* Assumptions:
|
|
*
|
|
****************************************************************************/
|
|
|
|
int sem_trywait(FAR sem_t *sem)
|
|
{
|
|
FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
|
|
irqstate_t saved_state;
|
|
int ret = ERROR;
|
|
|
|
/* This API should not be called from interrupt handlers */
|
|
|
|
DEBUGASSERT(up_interrupt_context() == false)
|
|
|
|
/* Assume any errors reported are due to invalid arguments. */
|
|
|
|
*get_errno_ptr() = EINVAL;
|
|
|
|
if (sem)
|
|
{
|
|
/* The following operations must be performed with interrupts
|
|
* disabled because sem_post() may be called from an interrupt
|
|
* handler.
|
|
*/
|
|
|
|
saved_state = irqsave();
|
|
|
|
/* Any further errors could only be occurred because the semaphore
|
|
* is not available.
|
|
*/
|
|
|
|
*get_errno_ptr() = EAGAIN;
|
|
|
|
/* If the semaphore is available, give it to the requesting task */
|
|
|
|
if (sem->semcount > 0)
|
|
{
|
|
/* It is, let the task take the semaphore */
|
|
|
|
sem->semcount--;
|
|
rtcb->waitsem = NULL;
|
|
ret = OK;
|
|
}
|
|
|
|
/* Interrupts may now be enabled. */
|
|
|
|
irqrestore(saved_state);
|
|
}
|
|
|
|
return ret;
|
|
}
|