linux-kernel - Re: [PATCH] slub: always align cpu_slab to honor cmpxchg

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Message-ID: <alpine.DEB.2.00.1106021015220.18350@chino.kir.corp.google.com>
Date:	Thu, 2 Jun 2011 10:16:31 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Chris Metcalf <cmetcalf@...era.com>
cc:	Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH] slub: always align cpu_slab to honor cmpxchg_double
 requirement

On Thu, 2 Jun 2011, Chris Metcalf wrote:

> On an architecture without CMPXCHG_LOCAL but with DEBUG_VM enabled,
> the VM_BUG_ON() in __pcpu_double_call_return_bool() will cause an early
> panic during boot unless we always align cpu_slab properly.
> 
> In principle we could remove the alignment-testing VM_BUG_ON() for
> architectures that don't have CMPXCHG_LOCAL, but leaving it in means
> that new code will tend not to break x86 even if it is introduced
> on another platform, and it's low cost to require alignment.
> 
> Signed-off-by: Chris Metcalf <cmetcalf@...era.com>

Acked-by: David Rientjes <rientjes@...gle.com>

> ---
> This needs to be pushed for 3.0 to allow arch/tile to boot.
> I'm happy to push it but I assume it would be better coming
> from an mm or percpu tree.  Thanks!
> 

Should also be marked for stable for 2.6.39.x, right?
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