225 lines
6.8 KiB
C
225 lines
6.8 KiB
C
/****************************************************************************
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* sched/semaphore/sem_timedwait.c
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*
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* Copyright (C) 2011, 2013-2016 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdint.h>
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#include <unistd.h>
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#include <semaphore.h>
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#include <time.h>
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#include <errno.h>
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#include <debug.h>
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#include <nuttx/irq.h>
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#include <nuttx/arch.h>
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#include <nuttx/wdog.h>
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#include "sched/sched.h"
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#include "clock/clock.h"
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#include "semaphore/semaphore.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: sem_timedwait
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*
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* Description:
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* This function will lock the semaphore referenced by sem as in the
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* sem_wait() function. However, if the semaphore cannot be locked without
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* waiting for another process or thread to unlock the semaphore by
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* performing a sem_post() function, this wait will be terminated when the
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* specified timeout expires.
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*
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* The timeout will expire when the absolute time specified by abstime
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* passes, as measured by the clock on which timeouts are based (that is,
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* when the value of that clock equals or exceeds abstime), or if the
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* absolute time specified by abstime has already been passed at the
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* time of the call.
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*
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* Parameters:
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* sem - Semaphore object
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* abstime - The absolute time to wait until a timeout is declared.
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*
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* Return Value:
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* Zero (OK) is returned on success. On failure, -1 (ERROR) is returned
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* and the errno is set appropriately:
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*
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* EINVAL The sem argument does not refer to a valid semaphore. Or the
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* thread would have blocked, and the abstime parameter specified
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* a nanoseconds field value less than zero or greater than or
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* equal to 1000 million.
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* ETIMEDOUT The semaphore could not be locked before the specified timeout
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* expired.
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* EDEADLK A deadlock condition was detected.
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* EINTR A signal interrupted this function.
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*
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****************************************************************************/
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int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime)
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{
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FAR struct tcb_s *rtcb = this_task();
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irqstate_t flags;
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int ticks;
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int errcode;
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int ret = ERROR;
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DEBUGASSERT(up_interrupt_context() == false && rtcb->waitdog == NULL);
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/* Verify the input parameters and, in case of an error, set
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* errno appropriately.
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*/
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#ifdef CONFIG_DEBUG_FEATURES
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if (!abstime || !sem)
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{
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errcode = EINVAL;
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goto errout;
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}
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#endif
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/* Create a watchdog. We will not actually need this watchdog
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* unless the semaphore is unavailable, but we will reserve it up
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* front before we enter the following critical section.
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*/
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rtcb->waitdog = wd_create();
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if (!rtcb->waitdog)
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{
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errcode = ENOMEM;
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goto errout;
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}
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/* We will disable interrupts until we have completed the semaphore
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* wait. We need to do this (as opposed to just disabling pre-emption)
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* because there could be interrupt handlers that are asynchronously
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* posting semaphores and to prevent race conditions with watchdog
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* timeout. This is not too bad because interrupts will be re-
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* enabled while we are blocked waiting for the semaphore.
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*/
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flags = enter_critical_section();
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/* Try to take the semaphore without waiting. */
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ret = sem_trywait(sem);
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if (ret == OK)
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{
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/* We got it! */
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goto success_with_irqdisabled;
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}
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/* We will have to wait for the semaphore. Make sure that we were provided
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* with a valid timeout.
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*/
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if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
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{
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errcode = EINVAL;
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goto errout_with_irqdisabled;
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}
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/* Convert the timespec to clock ticks. We must have interrupts
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* disabled here so that this time stays valid until the wait begins.
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*/
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errcode = clock_abstime2ticks(CLOCK_REALTIME, abstime, &ticks);
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/* If the time has already expired return immediately. */
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if (errcode == OK && ticks <= 0)
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{
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errcode = ETIMEDOUT;
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goto errout_with_irqdisabled;
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}
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/* Handle any time-related errors */
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if (errcode != OK)
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{
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goto errout_with_irqdisabled;
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}
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/* Start the watchdog */
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(void)wd_start(rtcb->waitdog, ticks, (wdentry_t)sem_timeout, 1, getpid());
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/* Now perform the blocking wait */
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ret = sem_wait(sem);
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if (ret < 0)
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{
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/* sem_wait() failed. Save the errno value */
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errcode = get_errno();
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}
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/* Stop the watchdog timer */
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wd_cancel(rtcb->waitdog);
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if (errcode != OK)
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{
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goto errout_with_irqdisabled;
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}
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/* We can now restore interrupts and delete the watchdog */
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/* Success exits */
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success_with_irqdisabled:
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leave_critical_section(flags);
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wd_delete(rtcb->waitdog);
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rtcb->waitdog = NULL;
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return OK;
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/* Error exits */
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errout_with_irqdisabled:
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leave_critical_section(flags);
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wd_delete(rtcb->waitdog);
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rtcb->waitdog = NULL;
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errout:
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set_errno(errcode);
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return ERROR;
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}
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