On Thu, 16 Sep 2021 09:35:47 -0700 Paul E. McKenney wrote:

quoted

quoted

How did you pick v5.13?  force_disable_hpet() was added by
62187910b0fc ("x86/intel: Add quirk to disable HPET for the Baytrail
platform"), which appeared in v3.15.  

Erm, good question, it started happening for me (and others with the
same laptop) with v5.13. I just sort of assumed it was 2e27e793e280
("clocksource: Reduce clocksource-skew threshold"). 

It usually takes  a day to repro (4 hours was the quickest repro I've
seen) so bisection was kind of out of question.  

OK, so this is an intermittent condition where HPET is sometimes slow to
access for a short period of time?  If that is the case, my thought is
to set the clocksource to be reinitialized (without a splat and without
marking the clocksource unstable), and to splat (and mark the clocksource
unstable) if it is not get a good read after 100 subsequent attempts.

So as long as the period of slowness lasts for less than 50 seconds,
things would work fine.

Seem reasonable?

Could well be. Initially I thought it was suspend/resume related, then
I looked closer and it did happen mostly after resume... but anywhere
between 20 minutes to few hours after the resume.

I'm here to test less crude patches but since that may take some time
I'd hope we can get this merged and into stable ASAP. Hopefully it can
make it to 5.13 while that branch is alive and into Fedora. It really
makes Coffee Lake machines pretty much unusable.