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

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Date:   Wed, 24 Aug 2016 06:44:12 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Vince Weaver <vince@...ter.net>
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Arnaldo Carvalho de Melo <acme@...radead.org>
Subject: Re: [PATCH 0/3] perf, bts: Fallout from the fuzzer for perf/urgent

Thanks! I'll get back to you with something better.

On 23 August 2016 at 23:55, Vince Weaver <vince@...ter.net> wrote:
> On Tue, 23 Aug 2016, Alexander Shishkin wrote:
>
>> 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.
>
> Just wanted to say that when I backed out these patches the NMI errors
> went away, so they do seem to be a result of this patch series.
>
> Vince