linux-kernel - Re: [BUG] perf and kmemcheck : fatal combination

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Message-ID: <BANLkTikTq+V28wi_zujeJK+OksDTdjiUcg@mail.gmail.com>
Date:	Tue, 26 Apr 2011 10:43:47 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Eric Dumazet <eric.dumazet@...il.com>, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Paul Mackerras <paulus@...ba.org>,
	Vegard Nossum <vegardno@....uio.no>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [BUG] perf and kmemcheck : fatal combination

On Tue, Apr 26, 2011 at 10:38 AM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> On Mon, 2011-04-25 at 18:08 +0200, Eric Dumazet wrote:
>> Hi guys
>>
>> Just got a panic on a kmemcheck kernel, latest linux-2.6 tree.
>>
>> I forgot I had kmemcheck enabled, and started "perf top" just because my
>> machine was damn slow... Oh well...
>>
>> Crash in do_nmi -> nmi_enter() -> BUG_ON(in_nmi());
>
> Hmm,. I bet because kmemcheck triggers faults from nmi context because
> it messes about with the page protection bits a lot to track things.
>
> Can't really think of anything except not making perf available on
> kmemcheck kernels.
>
> ---
>  init/Kconfig |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/init/Kconfig b/init/Kconfig
> index 32745bf..94735b4 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1125,6 +1125,7 @@ config PERF_EVENTS
>        bool "Kernel performance events and counters"
>        default y if (PROFILING || PERF_COUNTERS)
>        depends on HAVE_PERF_EVENTS
> +       depends on !KMEMCHECK
>        select ANON_INODES
>        select IRQ_WORK
>        help

Acked-by: Pekka Enberg <penberg@...nel.org>
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