/****************************************************************************
* sched/sem_timedwait.c
*
* Copyright (C) 2011, 2013 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 <stdint.h>
#include <unistd.h>
#include <semaphore.h>
#include <time.h>
#include <errno.h>
#include <wdog.h>
#include <debug.h>
#include <nuttx/arch.h>
#include "os_internal.h"
#include "clock_internal.h"
#include "sem_internal.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Type Declarations
****************************************************************************/
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: sem_timeout
*
* Description:
* This function is called if the timeout elapses before the message queue
* becomes non-empty.
*
* Parameters:
* argc - the number of arguments (should be 1)
* pid - the task ID of the task to wakeup
*
* Return Value:
* None
*
* Assumptions:
*
****************************************************************************/
static void sem_timeout(int argc, uint32_t pid)
{
FAR struct tcb_s *wtcb;
irqstate_t flags;
/* Disable interrupts to avoid race conditions */
flags = irqsave();
/* Get the TCB associated with this pid. It is possible that
* task may no longer be active when this watchdog goes off.
*/
wtcb = sched_gettcb((pid_t)pid);
/* It is also possible that an interrupt/context switch beat us to the
* punch and already changed the task's state.
*/
if (wtcb && wtcb->task_state == TSTATE_WAIT_SEM)
{
/* Cancel the semaphore wait */
sem_waitirq(wtcb, ETIMEDOUT);
}
/* Interrupts may now be enabled. */
irqrestore(flags);
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: sem_timedwait
*
* Description:
* This function will lock the semaphore referenced by sem as in the
* sem_wait() function. However, if the semaphore cannot be locked without
* waiting for another process or thread to unlock the semaphore by
* performing a sem_post() function, this wait will be terminated when the
* specified timeout expires.
*
* The timeout will expire when the absolute time specified by abstime
* passes, as measured by the clock on which timeouts are based (that is,
* when the value of that clock equals or exceeds abstime), or if the
* absolute time specified by abstime has already been passed at the
* time of the call.
*
* Parameters:
* sem - Semaphore object
* abstime - The absolute time to wait until a timeout is declared.
*
* Return Value:
* One success, the length of the selected message in bytes.is
* returned. On failure, -1 (ERROR) is returned and the errno
* is set appropriately:
*
* EINVAL The sem argument does not refer to a valid semaphore. Or the
* thread would have blocked, and the abstime parameter specified
* a nanoseconds field value less than zero or greater than or
* equal to 1000 million.
* ETIMEDOUT The semaphore could not be locked before the specified timeout
* expired.
* EDEADLK A deadlock condition was detected.
* EINTR A signal interrupted this function.
*
****************************************************************************/
int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime)
{
FAR struct tcb_s *rtcb = (FAR struct tcb_s *)g_readytorun.head;
irqstate_t flags;
int ticks;
int err;
int ret = ERROR;
DEBUGASSERT(up_interrupt_context() == false && rtcb->waitdog == NULL);
/* Verify the input parameters and, in case of an error, set
* errno appropriately.
*/
#ifdef CONFIG_DEBUG
if (!abstime || !sem)
{
err = EINVAL;
goto errout;
}
#endif
/* Create a watchdog. We will not actually need this watchdog
* unless the the semaphore is unavailable, but we will reserve it up
* front before we enter the following critical section.
*/
rtcb->waitdog = wd_create();
if (!rtcb->waitdog)
{
err = ENOMEM;
goto errout;
}
/* We will disable interrupts until we have completed the semaphore
* wait. We need to do this (as opposed to just disabling pre-emption)
* because there could be interrupt handlers that are asynchronoulsy
* posting semaphores and to prevent race conditions with watchdog
* timeout. This is not too bad because interrupts will be re-
* enabled while we are blocked waiting for the semaphore.
*/
flags = irqsave();
/* Try to take the semaphore without waiting. */
ret = sem_trywait(sem);
if (ret == 0)
{
/* We got it! */
irqrestore(flags);
wd_delete(rtcb->waitdog);
rtcb->waitdog = NULL;
return OK;
}
/* We will have to wait for the semphore. Make sure that we were provided
* with a valid timeout.
*/
if (abstime->tv_sec < 0 || abstime->tv_nsec > 1000000000)
{
err = EINVAL;
goto errout_disabled;
}
/* Convert the timespec to clock ticks. We must have interrupts
* disabled here so that this time stays valid until the wait begins.
*/
err = clock_abstime2ticks(CLOCK_REALTIME, abstime, &ticks);
/* If the time has already expired return immediately. */
if (err == OK && ticks <= 0)
{
err = ETIMEDOUT;
goto errout_disabled;
}
/* Handle any time-related errors */
if (err != OK)
{
goto errout_disabled;
}
/* Start the watchdog */
err = OK;
wd_start(rtcb->waitdog, ticks, (wdentry_t)sem_timeout, 1, getpid());
/* Now perform the blocking wait */
ret = sem_wait(sem);
/* Stop the watchdog timer */
wd_cancel(rtcb->waitdog);
/* We can now restore interrupts and delete the watchdog */
irqrestore(flags);
wd_delete(rtcb->waitdog);
rtcb->waitdog = NULL;
/* We are either returning success or an error detected by sem_wait()
* or the timeout detected by sem_timeout(). The 'errno' value has
* been set appropriately by sem_wait() or sem_timeout() in those
* cases.
*/
return ret;
/* Error exits */
errout_disabled:
irqrestore(flags);
wd_delete(rtcb->waitdog);
rtcb->waitdog = NULL;
errout:
set_errno(err);
return ERROR;
}
