linux-kernel - Re: [170/197] lockdep: fix incorrect percpu usage

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Date:	Wed, 28 Apr 2010 13:46:54 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Greg KH <gregkh@...e.de>, Tejun Heo <tj@...nel.org>
Cc:	linux-kernel@...r.kernel.org, stable@...nel.org,
	Greg KH <greg@...ah.com>, stable-review@...nel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Randy Dunlap <randy.dunlap@...cle.com>,
	Eric Dumazet <dada1@...mosbay.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [170/197] lockdep: fix incorrect percpu usage

* Greg KH (gregkh@...e.de) wrote:
> 2.6.32-stable review patch.  If anyone has any objections, please let us know.
> 
> ------------------
> 
> From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> 
> The mainline kernel as of 2.6.34-rc5 is not affected by this problem because
> commit 10fad5e46f6c7bdfb01b1a012380a38e3c6ab346 fixed it by refactoring.
> 
> lockdep fix incorrect percpu usage
> 
> 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.
> 
> It should be applied to stable 2.6.23.x to 2.6.33.x (or whichever of these
> stable branches are still maintained).

Tejun, (same as module.c patch) should this patch be applied to 2.6.32.x, or
will it cause problems on ia64 ?

Thanks,

Mathieu

> 
> (tested on 2.6.33.1 x86_64)
> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> CC: Randy Dunlap <randy.dunlap@...cle.com>
> CC: Eric Dumazet <dada1@...mosbay.com>
> CC: Rusty Russell <rusty@...tcorp.com.au>
> CC: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> CC: Tejun Heo <tj@...nel.org>
> CC: Ingo Molnar <mingo@...e.hu>
> CC: Andrew Morton <akpm@...ux-foundation.org>
> CC: Linus Torvalds <torvalds@...ux-foundation.org>
> CC: Greg Kroah-Hartman <gregkh@...e.de>
> CC: Steven Rostedt <rostedt@...dmis.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
> 
> ---
>  kernel/lockdep.c |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> --- a/kernel/lockdep.c
> +++ b/kernel/lockdep.c
> @@ -591,9 +591,9 @@ static int static_obj(void *obj)
>  	 * percpu var?
>  	 */
>  	for_each_possible_cpu(i) {
> -		start = (unsigned long) &__per_cpu_start + per_cpu_offset(i);
> -		end   = (unsigned long) &__per_cpu_start + PERCPU_ENOUGH_ROOM
> -					+ per_cpu_offset(i);
> +		start = (unsigned long) per_cpu_ptr(&__per_cpu_start, i);
> +		end   = (unsigned long) per_cpu_ptr(&__per_cpu_start
> +						    + PERCPU_ENOUGH_ROOM, i);
>  
>  		if ((addr >= start) && (addr < end))
>  			return 1;
> 
> 

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