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SubjectRe: perf: perf_fuzzer crashes on Pentium 4 systems
On Thu, Apr 04, 2019 at 12:37:18PM -0400, Vince Weaver wrote:
> On Thu, 4 Apr 2019, Cyrill Gorcunov wrote:
>
> > On Thu, Apr 04, 2019 at 09:25:47AM -0400, Vince Weaver wrote:
> > >
> > > It looks like there are at least two bugs here, one that's a full
> > > hardlockup with nothing on serial console. The other is the NULL
> > > dereference.
>
> OK, it turns out the hard-lock and the null pointer dereference might be
> the same, I have a random seed for the fuzzer from a hard-lock crash that
> reproduces and it generated the null pointer crash. (This is with your
> patch applied).

I see. My patch simply eliminates wrong event for unimplemented general
events, but it definitely won't help with nil deref, so it mostly to
eliminate some potential side effects.

> I can try to see if I can bisect down to a specific event sequence that
> triggers this, but that can be tricky sometimes if things lock up so fast
> that the event log doesn't get written out before the crash.

Oh, Vince, I suspect such kind of bisection might consume a lot of your
time :( Maybe we could update perf fuzzer so that it would send events
to some net-storage first then write them to the counters, iow to automatize
this all stuff somehow?

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