linux-kernel - Re: [PATCH v3] watchdog: touch_nmi_watchdog should only touch local cpu not every one

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Message-ID: <20101110074941.GD29493@elte.hu>
Date:	Wed, 10 Nov 2010 08:49:41 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Don Zickus <dzickus@...hat.com>
Cc:	fweisbec@...il.com, Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>, akpm@...ux-foundation.org,
	sergey.senozhatsky@...il.com
Subject: Re: [PATCH v3] watchdog:  touch_nmi_watchdog should only touch local
 cpu not every one


* Don Zickus <dzickus@...hat.com> wrote:

> I ran into a scenario where while one cpu was stuck and should have panic'd 
> because of the NMI watchdog, it didn't.  The reason was another cpu was spewing 
> stack dumps on to the console.  Upon investigation, I noticed that when writing to 
> the console and also when dumping the stack, the watchdog is touched.
> 
> This causes all the cpus to reset their NMI watchdog flags and the 'stuck' cpu 
> just spins forever.

Hm, the flip side is that if a CPU is stuck spewing backtraces, we will now make all 
the other CPUs a lot more noisy - which might only 'lock up' because this CPU is 
stuck spewing oopses, right?

Andrew, what would be your preference?

Thanks,

	Ingo
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