Re: [PATCH] kernel/watchdog: fix spurious hard lockups

[Don Zickus]

On Wed, Jun 21, 2017 at 12:40:28PM +0000, Liang, Kan wrote:
> 
> > >
> > > The right fix for mainline can be found here.
> > > perf/x86/intel: enable CPU ref_cycles for GP counter perf/x86/intel,
> > > watchdog: Switch NMI watchdog to ref cycles on x86
> > > https://patchwork.kernel.org/patch/9779087/
> > > https://patchwork.kernel.org/patch/9779089/
> > 
> > Presumably the "right fix" will later be altered to revert this one-line
> > workaround?
> 
> The "right fix" itself will not touch the watchdog rate. I will modify the
> changelog to notify the people who want to do the backport.
> 
> As my understanding, it's not harmful even if we don't revert the
> workaround. It can still detect the hardlockup, only takes
> a tiny bit longer.

It depends on you perspective of harmful. :-) There are folks that would
like that sampling rate to be more accurate, so they can detect problems
soon than later.  You just took an input of 'watchdog_thresh' and blindly
multiplied it by 3, which can confuse an end user who thought they setup a 5
second threshold but instead it turned into a 15 second one. :-(

Cheers,
Don