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sched: Stop the sched timer when possible to save the power in tickless mode

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Remove KEEP_ALIVE_HACK to avoid waking up the device periodly.
The workaround it's added by:
    commit 6546fa39c7
    Author: Gregory Nutt <gnutt@nuttx.org>
    Date:   Tue Aug 12 11:12:00 2014 -0600

    Tickless Stuff:  Back out the risky timer operations when the ready-to-run
    list is modified. That is unsafe.  An ugly workaround is just to keep an
    interval timer going all of the time with a minimum duration equal to the
    timeslice interval.
But look like it doesn't needed anymore.

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
This commit is contained in:
Xiang Xiao 2022-07-26 00:07:12 +08:00 committed by patacongo
parent 17458c7dba
commit 50e2269642
1 changed files with 0 additions and 34 deletions
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34
sched/sched/sched_timerexpiration.c
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@ -45,31 +45,6 @@
#ifdef CONFIG_SCHED_TICKLESS
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* In the original design, it was planned that nxsched_reassess_timer() be
* called whenever there was a change at the head of the ready-to-run
* list. That call was intended to establish a new time-slice or to
* stop an old time-slice timer. However, it turns out that that
* solution is too fragile: The system is too vulnerable at the time
* that the ready-to-run list is modified in order to muck with timers.
*
* The kludge/work-around is simple to keep the timer running all of the
* time with an interval of no more than the timeslice interval. If we
* do this, then there is really no need to do anything when on context
* switches.
*/
#define KEEP_ALIVE_HACK 1
#if CONFIG_RR_INTERVAL > 0
# define KEEP_ALIVE_TICKS MSEC2TICK(CONFIG_RR_INTERVAL)
#else
# define KEEP_ALIVE_TICKS MSEC2TICK(80)
#endif
/****************************************************************************
* Public Data
****************************************************************************/
@ -272,15 +247,6 @@ static uint32_t nxsched_cpu_scheduler(int cpu, uint32_t ticks,
/* Returning zero means that there is no interesting event to be timed */
#ifdef KEEP_ALIVE_HACK
if (ret == 0)
{
/* Apply the keep alive hack */
return KEEP_ALIVE_TICKS;
}
#endif
return ret;
}
#endif