RE: [PATCH v2] NMI: fix NMI period is not correct when cpufrequency changes issue.

[Pan, Zhenjie]

> I believe it mattered to the Chrome folks. They want the watchdog to be as
> tight as possible so the user experience isn't a hang but a quick reboot
> instead.  They like setting the watchdog to something like 2 seconds.
> 
> There was a patch a few months ago that tried to hack around this issue and I
> suggested this approach as a better solution.  I forgot what the original
> problem was.  Perhaps someone can jump in and explain the problem being
> solved (other than the watchdog isn't always 10 seconds)?
> 
> Cheers,
> Don

Yes, I also think the period is important sometimes.
As I mentioned before, the case I meet is:
When the system hang with interrupt disabled, we use NMI to detect.
Then it will find hard lockup and cause a panic.
Panic is very important for debug these kind of issues.

But if cpu frequency change, the period will be 2 times, 3 times even more.(if cpu can down from 2.0GHz to 200MHz, will be 10 times, it's a very big deviation)
This make watchdog reset happen before hard lockup detect.

Thanks
Pan Zhenjie
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