linux-kernel - Re: [PATCH] watchdog: Make sure the watchdog thread gets CPU on loaded system

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Message-ID: <20120315143549.GC3941@redhat.com>
Date:	Thu, 15 Mar 2012 10:35:49 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Mandeep Singh Baines <msb@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Michal Hocko <mhocko@...e.cz>
Subject: Re: [PATCH] watchdog: Make sure the watchdog thread gets CPU on
 loaded system

On Thu, Mar 15, 2012 at 03:00:51PM +0100, Peter Zijlstra wrote:
> On Thu, 2012-03-15 at 13:42 +0100, Ingo Molnar wrote:
> > So unless there's concensus to remove everything but the hard 
> > lockup detection facilities, lets solve the technical problem at 
> > hand, ok? 
> 
> Well, at least make it possible to disable the silly soft thing.
> 
> And I really wouldn't know how the soft thing could possible help,
> except when not actually having a NMI watchdog. What case does it
> trigger where the NMI one doesn't?

I think softlockup really boils down to a pre-emption disabled detector
much like how the hardlockup really is a interrupts disabled detector.

The amount of code preventing the scheduler from running is most likely a
lot lower than the code the prevents interrrupts from happening.

Cheers,
Don

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