nuttx/sched/sched_processtimer.c

/************************************************************************
 * sched/sched_processtimer.c
 *
 *   Copyright (C) 2007, 2009 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 <nuttx/compiler.h>

#if CONFIG_RR_INTERVAL > 0
# include <sched.h>
# include <nuttx/arch.h>
#endif

#include "os_internal.h"
#include "wd_internal.h"
#include "clock_internal.h"

/************************************************************************
 * Definitions
 ************************************************************************/

/************************************************************************
 * Private Type Declarations
 ************************************************************************/

/************************************************************************
 * Global Variables
 ************************************************************************/

/************************************************************************
 * Private Variables
 ************************************************************************/

/************************************************************************
 * Private Functions
 ************************************************************************/

static void sched_process_timeslice(void)
{
#if CONFIG_RR_INTERVAL > 0
  _TCB *rtcb;

  /* Check if the currently executing task uses round robin
   * scheduling.
   */

  rtcb = (_TCB*)g_readytorun.head;
  if ((rtcb->flags & TCB_FLAG_ROUND_ROBIN) != 0)
    {
      /* Yes, check if decrementing the timeslice counter
       * would cause the timeslice to expire
       */

      if (rtcb->timeslice <= 1)
        {
          /* Yes, Now check if the task has pre-emption disabled.
           * If so, then we will freeze the timeslice count at
           * the value until the next tick after pre-emption
           * has been enabled.
           */

          if (!rtcb->lockcount)
            {
              /* Reset the timeslice in any case. */

              rtcb->timeslice = CONFIG_RR_INTERVAL / MSEC_PER_TICK;

              /* We know we are at the head of the ready to run
               * prioritized list.  We must be the highest priority
               * task eligible for execution.  Check the next task
               * in the ready to run list.  If it is the same
               * priority, then we need to relinquish the CPU and
               * give that task a shot.
               */

              if (rtcb->flink &&
                  rtcb->flink->sched_priority >= rtcb->sched_priority)
                {
                  /* Just resetting the task priority to its current
                   * value.  This this will cause the task to be
                   * rescheduled behind any other tasks at the same
                   * priority.
                   */

                  up_reprioritize_rtr(rtcb, rtcb->sched_priority);
                }
            }
        }
      else
        {
          /* Decrement the timeslice counter */

          rtcb->timeslice--;
        }
    }
#endif
}

/************************************************************************
 * Public Functions
 ************************************************************************/

/************************************************************************
 * System Timer Hooks
 *
 * These are standard interfaces that are exported by the OS
 * for use by the architecture specific logic
 *
 ************************************************************************/

/************************************************************************
 * Name:  sched_process_timer
 *
 * Description:
 *   This function handles system timer events.
 *   The timer interrupt logic itself is implemented in the
 *   architecture specific code, but must call the following OS
 *   function periodically -- the calling interval must be
 *   MSEC_PER_TICK
 *
 * Inputs:
 *   None
 *
 * Return Value:
 *   None
 *
 ************************************************************************/

void sched_process_timer(void)
{
  /* Increment the system time (if in the link) */

#ifndef CONFIG_DISABLE_CLOCK
#ifdef CONFIG_HAVE_WEAKFUNCTIONS
  if (clock_timer != NULL)
#endif
    {
      clock_timer();
    }
#endif

  /* Process watchdogs (if in the link) */

#ifdef CONFIG_HAVE_WEAKFUNCTIONS
  if (wd_timer != NULL)
#endif
    {
      wd_timer();
    }

  /* Check if the currently executing task has exceeded its
   * timeslice.
   */

  sched_process_timeslice();
}