linux-kernel - Re: [PATCH] perf: powerpc: Disable pagefaults during callchain stack read

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Date:	Mon, 01 Aug 2011 06:44:36 -0600
From:	David Ahern <dsahern@...il.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC:	Peter Zijlstra <peterz@...radead.org>, anton@...ba.org,
	acme@...stprotocols.net, mingo@...e.hu, paulus@...ba.org,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: powerpc: Disable pagefaults during callchain stack
 read



On 08/01/2011 04:39 AM, Benjamin Herrenschmidt wrote:
> On Mon, 2011-08-01 at 11:59 +0200, Peter Zijlstra wrote:
>>> Signed-off-by: David Ahern <dsahern@...il.com>
>>> CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>>> CC: Anton Blanchard <anton@...ba.org> 
>>
>> Hmm, Paul, didn't you fix something like this early on? Anyway, I've
>> no
>> objections since I'm really not familiar enough with the PPC side of
>> things. 
> 
> I'm travelling so I haven't had a chance to review properly or even test
> but it looks like an ad-hoc fix for the immediate problem.
> 
> Ultimately, I want to rework that stuff to do a __gup_fast like x86 does
> (maybe as a fallback from an attempt at access first) so we work around
> access permissions blocked by lack of dirty/accessed bits but in the
> meantime, this should fix the immediate issue.

The problem goes back to all kernel releases with perf, so this patch
should get applied to the stable trains too.

David

> 
> Cheers,
> Ben.
> 
> 
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