Re: [PATCH -v3] perf, x86: try to handle unknown nmis with running perfctrs

Cyrill Gorcunov
2010-08-26T15:34:18Z

On Thu, Aug 26, 2010 at 11:22:46AM -0400, Don Zickus wrote:
> On Thu, Aug 26, 2010 at 01:18:29PM +0400, Cyrill Gorcunov wrote:
> > On Thu, Aug 26, 2010 at 1:00 PM, Robert Richter <robert.richter@amd.com> wrote:
> > ...
> > >
> > > This could also be a race in the counter handling code, or we do not
> > > proper count the number of handled counters. Maybe 2 counters actually
> > > fired but we only noticed one counter and then accidentially cleared
> > > the 2nd without processing it.
> > >
> > > -Robert
> > >
> >
> > Any chance to get it tested on P4 machine since it has a bit
> > different design?
>
> Hmm, I take that back. I guess I can reproduce this on my i5 that I had
> using Ingo's config.
>
> Working on Robert's assumption, I added code to perf_event_intel.c that
> said if handled !=0 just add one to it (IOW always process handled as 0 or
> something >1). That seems to working good and catches the nmis that Ingo
> was seeing.
>
> I'll keep looking for the race condition to better fix it.
>
> Cheers,
> Don
>

Sounds promising, mind to post new inter-diff? Ie what you have
changed from Robert's patch.

-- Cyrill