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Date: Fri, 18 Jan 2013 13:42:42 +0900
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [RFC][PATCH v2] slub: Keep page and object in sync in
 slab_alloc_node()
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To: Steven Rostedt <rostedt@goodmis.org>
Cc: Christoph Lameter <cl@linux.com>, LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>, Andrew Morton <akpm@linux-foundation.org>, Pekka Enberg <penberg@kernel.org>, Matt Mackall <mpm@selenic.com>, Thomas Gleixner <tglx@linutronix.de>, RT <linux-rt-users@vger.kernel.org>, Clark Williams <clark@redhat.com>, John Kacur <jkacur@gmail.com>, "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>

Hello, Steven.

On Thu, Jan 17, 2013 at 07:28:44PM -0500, Steven Rostedt wrote:
> In slab_alloc_node(), after the cpu_slab is assigned, if the task is
> preempted and moves to another CPU, there's nothing keeping the page and
> object in sync. The -rt kernel crashed because page was NULL and object
> was not, and the node_match() dereferences page. Even though the crash
> happened on -rt, there's nothing that's keeping this from happening on
> mainline.
> 
> The easiest fix is to disable interrupts for the entire time from
> acquiring the current CPU cpu_slab and assigning the object and page.
> After that, it's fine to allow preemption.

How about this?

It's based on v3.8-rc3.
I'm not test this patch, yet.
Just for sharing my idea to fix a problem.

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