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nuttx/sched/sched_processtimer.c

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/************************************************************************
* sched/sched_processtimer.c
*
* Copyright (C) 2007, 2009, 2014 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>
#include <time.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"
/************************************************************************
* Pre-processor Definitions
************************************************************************/
#ifndef CONFIG_SCHED_CPULOAD_TIMECONSTANT
# define CONFIG_SCHED_CPULOAD_TIMECONSTANT 2
#endif
/************************************************************************
* Private Type Declarations
************************************************************************/
/************************************************************************
* Global Variables
************************************************************************/
/* This structure is used when CONFIG_SCHED_CPULOAD to sample CPU usage */
#ifdef CONFIG_SCHED_CPULOAD
volatile struct cpuload_s g_cpuload;
#endif
/************************************************************************
* Private Variables
************************************************************************/
/************************************************************************
* Private Functions
************************************************************************/
/************************************************************************
* Name: sched_process_timeslice
*
* Description:
* Check if the currently executing task has exceeded its time slice.
*
* Inputs:
* None
*
* Return Value:
* None
*
************************************************************************/
#if CONFIG_RR_INTERVAL > 0
static inline void sched_process_timeslice(void)
{
FAR struct tcb_s *rtcb = (FAR struct tcb_s*)g_readytorun.head;
/* Check if the currently executing task uses round robin
* scheduling.
*/
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--;
}
}
}
#else
# define sched_process_timeslice()
#endif
/************************************************************************
* Name: sched_process_cpuload
*
* Description:
* Collect data that can be used for CPU load measurements.
*
* Inputs:
* None
*
* Return Value:
* None
*
************************************************************************/
#if defined(CONFIG_SCHED_CPULOAD)
static inline void sched_process_cpuload(void)
{
FAR struct tcb_s *rtcb = (FAR struct tcb_s*)g_readytorun.head;
/* Gather stats for cpuload. cpuload is percent of time cpu is not idle. */
/* Is the idle task running */
if (rtcb->pid == 0)
{
++g_cpuload.idle;
}
/* Increment tick count. If the accumulated tick value exceed a time
* constant, then shift the accumulators.
*/
if (++g_cpuload.cnt > (CONFIG_SCHED_CPULOAD_TIMECONSTANT * CLOCKS_PER_SEC))
{
g_cpuload.cnt >>= 1;
g_cpuload.idle >>= 1;
}
}
#else
# define sched_process_cpuload()
#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
/* Perform CPU load measurements (before any timer-initiated context switches
* can occur)
*/
sched_process_cpuload();
/* 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();
}
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