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

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Date:   Tue, 20 Jun 2017 16:00:02 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Prarit Bhargava <prarit@...hat.com>
Cc:     kan.liang@...el.com, linux-kernel@...r.kernel.org,
        dzickus@...hat.com, mingo@...nel.org, akpm@...ux-foundation.org,
        babu.moger@...cle.com, atomlin@...hat.com,
        torvalds@...ux-foundation.org, peterz@...radead.org,
        tglx@...utronix.de, eranian@...gle.com, acme@...hat.com,
        stable@...r.kernel.org
Subject: Re: [PATCH] kernel/watchdog: fix spurious hard lockups

On Tue, Jun 20, 2017 at 06:34:23PM -0400, Prarit Bhargava wrote:
> 
> 
> On 06/20/2017 05:33 PM, kan.liang@...el.com wrote:
> > From: Kan Liang <Kan.liang@...el.com>
> > 
> > Some users reported spurious NMI watchdog timeouts.
> > 
> > We now have more and more systems where the Turbo range is wide enough
> > that the NMI watchdog expires faster than the soft watchdog timer that
> > updates the interrupt tick the NMI watchdog relies on.
> > 
> 
> Hmm ... odd that I haven't seen this.  We're running a pretty wide
> variety of systems here.  Do you have a reproducer?  I'd like to see
> this occur on production HW.

It only happens on a few specific CPU SKUs with a very wide Turbo range.
Reproducer is typically some stress workload that turbos very high.

-Andi