Re: [PATCH] Clocksource: Avoid misjudgment of clocksource

[Paul E. McKenney]

On Thu, Dec 09, 2021 at 09:14:05PM +0800, Gang Li wrote:
> Hi all,
> 
> How about changing clocksource_watchdog from classical timer to hrtimer?
> hrtimer is more accurate and stable, and makes it much easier for us to deal
> with misjudgments.

To make hrtimer more accurate in the busy-system scenarios that are
under test, we would need to specify HRTIMER_MODE_HARD.  Otherwise,
hrtimer handlers execute in softirq, just like timers do.  So without
the HRTIMER_MODE_HARD, the hrtimers would be delayed just as badly as
we are seeing for the normal timers.

Unfortunately, use of HRTIMER_MODE_HARD has response-time consequences,
especially when the timer reads need to be retried.  So my guess is
that hrtimers are not a helpful path forward here.

							Thanx, Paul