linux-kernel - Re: [PATCH 0/3] perf, bts: Fallout from the fuzzer for perf/urgent

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Date:   Tue, 23 Aug 2016 20:10:34 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Vince Weaver <vince@...ter.net>
Cc:     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 0/3] perf, bts: Fallout from the fuzzer for perf/urgent

Vince Weaver <vince@...ter.net> writes:

> On Tue, 23 Aug 2016, Alexander Shishkin wrote:
>
>> Recently Vince has reported warnings and panics coming from the
>> general direction of AUX tracing. I found two bugs which manifest
>> similarly, one in intel_bts driver and one in AUX unmapping path.
>> 
>> Both are triggered by racing SET_OUTPUT against mmap_close while
>> running AUX tracing. I have a test case that set fire to the kernel
>> within a few seconds by doing this, which I can share if anyone
>> cares.
>
> I've applied these and am fuzzing on my Haswell machine and I'm getting 
> lots and lots of
>
> [  945.536374] Dazed and confused, but trying to continue
> [  945.542391] Uhhuh. NMI received for unknown reason 21 on CPU 2.
> [  945.549360] Do you have a strange power saving mode enabled?
> [  945.556701] Dazed and confused, but trying to continue
> [  945.563643] Uhhuh. NMI received for unknown reason 31 on CPU 2.
> [  945.571379] Do you have a strange power saving mode enabled?
> [  945.578754] Dazed and confused, but trying to continue
> [  945.630889] Uhhuh. NMI received for unknown reason 31 on CPU 2.
> [  945.638141] Do you have a strange power saving mode enabled?
> [  945.645523] Dazed and confused, but trying to continue
>
> messages that I wasn't getting before.  Of course, I updated from -rc2 to 
> -rc3 before applying the patch so it could also be related to that too, I 
> can try backing out the patches and see if it still happens.

Uhhuh, that's not cool, let me look some more. But it should stop dying
on bts/aux stuff at least.

Regards,
--
Alex