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Message-ID: <6920d83c-19b9-9243-c6aa-0f21288a4006@intel.com>
Date: Wed, 21 Jun 2017 14:02:48 -0700
From: Marc Herbert <Marc.Herbert@...el.com>
To: Prarit Bhargava <prarit@...hat.com>,
Andi Kleen <ak@...ux.intel.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 20/06/17 17:12, Prarit Bhargava wrote:
>>> 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.
"Production" is where this patch was born and still lives right now:
https://chromium-review.googlesource.com/c/506327/
>> It only happens on a few specific CPU SKUs with a very wide Turbo range.
>
> Which ones?
>
The ones with turbo mode > 2.5 x TSC_MHz when you stress them hard and long
enough. Simple maths: just compare the soft and hard timers in the code.
The factor 3 moves the condition to: turbo > 7.5 x TSC_MHz.
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