linux-kernel - Re: [PATCH v2 0/5] perf, bts: Fallout from the fuzzer for perf/urgent

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Date:   Thu, 8 Sep 2016 08:54:13 -0400 (EDT)
From:   Vince Weaver <vincent.weaver@...ne.edu>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>
cc:     Vince Weaver <vincent.weaver@...ne.edu>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        eranian@...gle.com, Arnaldo Carvalho de Melo <acme@...radead.org>
Subject: Re: [PATCH v2 0/5] perf, bts: Fallout from the fuzzer for
 perf/urgent

On Thu, 8 Sep 2016, Alexander Shishkin wrote:

> Vince Weaver <vincent.weaver@...ne.edu> writes:
> 
> > On the skylake machine with the original 5 patches I got this after 
> > continuing to fuzz.  Sorry about the lack of frame pointer, next
x> > compile will have it enabled.
> >
> > If it matters, prior to this I hit the unrelated
> > [25510.278199] WARNING: CPU: 1 PID: 25405 at kernel/events/core.c:3554 perf_event_read+0x18f/0x1a0
> >
> >
> > [28682.174684] WARNING: CPU: 7 PID: 31992 at kernel/events/core.c:4961 perf_mmap_close+0x2e1/0x2f0
> 
> It just keeps on giving, doesn't it. I've got the same thing here during
> the night, looking at it again. Did you capture the seed by any chance?

It was triggered by

	Seeding random number generator with 1473284719
        /proc/sys/kernel/perf_event_max_sample_rate currently: 1000/s
        /proc/sys/kernel/perf_event_paranoid currently: 0
        To reproduce, try: ./perf_fuzzer -s 30000 -r 1473284719

but in my experience these things don't always reproduce deterministically.  

I can try reproducing it but I can't right now because overnight the 
machine locked hard (even sysrq isn't helping) with just the unhelpful 
message of

[70953.494637] ------------[ cut here ]------------

not sure if I have the serial console configured wrong or if it just locks 
up before it can send anything.

Anyway I'll head to the lab after my class and reboot things.

Vince