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

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Date:	Tue, 26 Apr 2011 09:38:45 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Paul Mackerras <paulus@...ba.org>,
	Pekka Enberg <penberg@...nel.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 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

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