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

From: Marc Herbert
Date: Wed Jun 21 2017 - 17:03:10 EST

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:

>> 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.