linux-kernel - Re: [PATCH 1/2] oprofile: fix race condition in event

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Date:	Fri, 9 Oct 2009 21:50:16 +0200
From:	Robert Richter <robert.richter@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	LKML <linux-kernel@...r.kernel.org>,
	oprofile-list <oprofile-list@...ts.sourceforge.net>,
	David Rientjes <rientjes@...gle.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 1/2] oprofile: fix race condition in event_buffer free

On 09.10.09 21:33:29, Robert Richter wrote:
> From: David Rientjes <rientjes@...gle.com>
> 
> Looking at the 2.6.31-rc9 code, it appears there is a race condition
> in the event_buffer cleanup code path (shutdown). This could lead to
> kernel panic as some CPUs may be operating on the event buffer AFTER
> it has been freed. The attached patch solves the problem and makes
> sure CPUs check if the buffer is not NULL before they access it as
> some may have been spinning on the mutex while the buffer was being
> freed.
> 
> The race may happen if the buffer is freed during pending reads. But
> it is not clear why there are races in add_event_entry() since all
> workqueues or handlers are canceled or flushed before the event buffer
> is freed.
> 
> Signed-off-by: David Rientjes <rientjes@...gle.com>
> Signed-off-by: Stephane Eranian <eranian@...gle.com>
> Signed-off-by: Robert Richter <robert.richter@....com>

Ingo,

you can also pull the patches from here:

 git://git.kernel.org/pub/scm/linux/kernel/git/rric/oprofile.git urgent

Thanks.

-Robert

-- 
Advanced Micro Devices, Inc.
Operating System Research Center
email: robert.richter@....com

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