linux-kernel - Re: [PATCH] slub: change cmpxchg_double_slab in get_freelist() to __cmpxchg_double

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Message-ID: <alpine.LFD.2.02.1206010934460.2163@tux.localdomain>
Date:	Fri, 1 Jun 2012 09:39:20 +0300 (EEST)
From:	Pekka Enberg <penberg@...nel.org>
To:	David Rientjes <rientjes@...gle.com>
cc:	Joonsoo Kim <js1304@...il.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	torvalds@...ux-foundation.org
Subject: Re: [PATCH] slub: change cmpxchg_double_slab in get_freelist() to
 __cmpxchg_double_slab

On Mon, 14 May 2012, David Rientjes wrote:
> > On Fri, 11 May 2012, Joonsoo Kim wrote:
> > 
> > > get_freelist() is only called by __slab_alloc with interrupt disabled,
> > > so __cmpxchg_double_slab is suitable.
> > > 
> > > Signed-off-by: Joonsoo Kim <js1304@...il.com>
> > 
> > Acked-by: David Rientjes <rientjes@...gle.com>

On Thu, 31 May 2012, David Rientjes wrote:
> Pekka, did you want to pick this up so it can get into linux-next?

We now made get_freelist() *require* interrupts to be disabled which 
deserves a comment, no?

Also, what do we gain from patches like this? It's somewhat 
counterintuitive that we have a function with "cmpxchg" in it which is not 
always atomic (i.e. you need to have interrupts disabled).

IIRC, there was even a long rant about this by Linus but I'm unable to 
find it in my email archives.

			Pekka
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