linux-kernel - Re: [PATCH] lockdep fix incorrect percpu usage

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Message-ID: <20100330150551.GA22312@Krystal>
Date:	Tue, 30 Mar 2010 11:05:51 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Eric Dumazet <dada1@...mosbay.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Tejun Heo <tj@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	stable <stable@...nel.org>
Subject: Re: [PATCH] lockdep fix incorrect percpu usage

* Peter Zijlstra (peterz@...radead.org) wrote:
> On Tue, 2010-03-30 at 09:45 -0400, Mathieu Desnoyers wrote:
> > * Peter Zijlstra (peterz@...radead.org) wrote:
> > > On Mon, 2010-03-29 at 23:34 -0400, Mathieu Desnoyers wrote:
> > > > Should use per_cpu_ptr() to obfuscate the per cpu pointers (RELOC_HIDE is needed
> > > > for per cpu pointers).
> > > > 
> > > > git blame points to commit:
> > > > 
> > > > lockdep.c: commit 8e18257d29238311e82085152741f0c3aa18b74d
> > > > 
> > > > But it's really just moving the code around. But it's enough to say that the
> > > > problems appeared before Jul 19 01:48:54 2007, which brings us back to 2.6.23.
> > > > 
> > > > So it should be applied to stable 2.6.23.x to 2.6.33.x (or whichever of these
> > > > stable branches are still maintained) and to mainline 2.6.34-rc2.
> > > 
> > > well, definately not to mainline, since that code is utterly busted in
> > > mainline due to recent per-cpu changes.
> > 
> > How recent ? I'm based on 
> > 
> > commit f57d4e859a8acd63f878cd0534ec4b990b1710dc
> > Merge: 0528faa... eed6351...
> > Author: Ingo Molnar <mingo@...e.hu>
> > Date:   Mon Mar 29 18:56:00 2010 +0200
> > 
> > from -tip and I see the problem there, both in module.c and lockdep.c.
> 
> Yeah, its basically been busted since the early merge window period,
> hopefully Tejun's patches will make it in soon:
> 
>   http://lkml.org/lkml/2010/3/10/79

I see. These patches are "on their way" to mainline, so it's better not to
create conflicts. So the lockdep patch should only be applied to -stable, but
separate module.c patch should apply to both -stable and mainline. Am I
correct ?

Thanks,

Mathieu


> 
> 
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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