Subject: Re: [RFC PATCH 22/23] watchdog/hardlockup/hpet: Only enable the HPET watchdog via a boot parameter

From: Ricardo Neri <[email-masked]>
Date: Wed, 13 Jun 2018 17:58:39 -0700

On Tue, Jun 12, 2018 at 10:26:57PM -0700, Randy Dunlap wrote:
> On 06/12/2018 05:57 PM, Ricardo Neri wrote:
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index f2040d4..a8833c7 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -2577,7 +2577,7 @@
> >  			Format: [state][,regs][,debounce][,die]
> >  
> >  	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
> > -			Format: [panic,][nopanic,][num]
> > +			Format: [panic,][nopanic,][num,][hpet]
> >  			Valid num: 0 or 1
> >  			0 - turn hardlockup detector in nmi_watchdog off
> >  			1 - turn hardlockup detector in nmi_watchdog on
> 
> This says that I can use "nmi_watchdog=hpet" without using 0 or 1.
> Is that correct?

Yes, this what I meant. In my view, if you set nmi_watchdog=hpet it
implies that you want to activate the NMI watchdog. In this case, perf.

I can see how this will be ambiguous for the case of perf and arch NMI
watchdogs.

Alternative, a new parameter could be added; such as nmi_watchdog_type. I
didn't want to add it in this patchset as I think that a single parameter
can handle the enablement and type of the NMI watchdog.

What do you think?

Thanks and BR,
Ricardo