Date: Tue, 20 Jun 2017 16:00:02 -0700
From: Andi Kleen <ak@linux.intel.com>
To: Prarit Bhargava <prarit@redhat.com>
Cc: kan.liang@intel.com, linux-kernel@vger.kernel.org, dzickus@redhat.com,
        mingo@kernel.org, akpm@linux-foundation.org, babu.moger@oracle.com,
        atomlin@redhat.com, torvalds@linux-foundation.org,
        peterz@infradead.org, tglx@linutronix.de, eranian@google.com,
        acme@redhat.com, stable@vger.kernel.org
Subject: Re: [PATCH] kernel/watchdog: fix spurious hard lockups
Message-ID: <20170620230002.GE23705@tassilo.jf.intel.com>
References: <20170620213309.30051-1-kan.liang@intel.com>
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On Tue, Jun 20, 2017 at 06:34:23PM -0400, Prarit Bhargava wrote:
> 
> 
> On 06/20/2017 05:33 PM, kan.liang@intel.com wrote:
> > From: Kan Liang <Kan.liang@intel.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