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

Don Zickus
2010-08-26T15:23:34Z

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