linux-kernel - Re: x86_pmu_start WARN

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 20 Feb 2014 07:47:23 -0800
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Vince Weaver <vincent.weaver@...ne.edu>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: x86_pmu_start WARN_ON.

Peter Zijlstra <peterz@...radead.org> writes:

> On Wed, Feb 19, 2014 at 05:34:49PM -0500, Vince Weaver wrote:
>> So where would the NMI counter event get disabled?  Would it never get 
>> disabled, just because it's always running and always gets the same fixed 
>> slot?  Why isn't this a problem all the time, not just with corner cases?
>
> Well it could get another counter assignment I suppose; there's no
> guarantee it always ends up in the fixed counter although that's rather
> likely.
>
>> Is somehow n_added getting confused?
>
> I'd expect worse than a warning if that happened, but who knows.
>
> You could try with the below; make sure you've got CONFIG_FUNCTION_TRACER=y.
>
> Then (assuming debugfs is mounted in /debug ; most modern distros have
> it at /sys/kernel/debug but they're wrong!):
>
> # echo 0 > /debug/tracing/tracing_on
> # echo function > /debug/tracing/current_tracer
> # echo nop > /debug/tracing/current_tracer
> # echo 0 > /debug/tracing/trace
> # echo 1 > /debug/tracing/tracing_on
>
> And make it go *BOOM*, then:
>
> # cat /debug/tracing/trace | bzip2 -9 > ~/trace.bz2

This won't work unless you apply this patch

http://lkml.org/lkml/2013/10/20/94

-Andi


-- 
ak@...ux.intel.com -- Speaking for myself only
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/