linux-kernel - Re: SLUB: simplify re on_each

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Message-ID: <84144f020807170526x6f013357i29280595f65a67f4@mail.gmail.com>
Date:	Thu, 17 Jul 2008 15:26:46 +0300
From:	"Pekka Enberg" <penberg@...helsinki.fi>
To:	"Robin Holt" <holt@....com>
Cc:	"Alexey Dobriyan" <adobriyan@...il.com>, cl@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: SLUB: simplify re on_each_cpu()

Hi Robin,

On Wed, Jul 16, 2008 at 09:29:02PM +0400, Alexey Dobriyan wrote:
>> on_each_cpu() expands to function call on UP, too.

On Thu, Jul 17, 2008 at 2:38 PM, Robin Holt <holt@....com> wrote:
> It looks to me like on_each_cpu is a #define for !SMP.  Are you certain
> of the need for this change?  Are you looking at a different tree than
> Linus'?

I think it's actually you who is looking at an older tree.

However, while double-checking this, I noticed that for UP,
on_each_cpu() enables interrupts unconditionally with
local_irq_enable() whereas the call while the old code in SLUB did a
local_irq_restore() that preserves the irq mask. Looking at the
callers of flush_all() in mm/slub.c, the change looks okay, but it's
still bit strange on_each_cpu() works that way on UP.

                          Pekka
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