Messages in this thread | | | Date | Mon, 22 Apr 2013 14:59:29 -0400 | From | Don Zickus <> | Subject | Re: [PATCH v2] NMI: fix NMI period is not correct when cpu frequency changes issue. |
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On Mon, Apr 22, 2013 at 12:50:34AM +0000, Pan, Zhenjie wrote: > > 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.
So you are saying with the longer hard lockup delay, the iTCO_wdt is firing before the hard lockup detector?
Cheers, Don
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