linux-kernel - Re: [GIT PULL] SLAB changes for v2.6.39-rc1

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Date:	Thu, 24 Mar 2011 14:05:51 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Pekka Enberg <penberg@...nel.org>
cc:	Ingo Molnar <mingo@...e.hu>, Eric Dumazet <eric.dumazet@...il.com>,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	tj@...nel.org, npiggin@...nel.dk, rientjes@...gle.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [GIT PULL] SLAB changes for v2.6.39-rc1

On Thu, 24 Mar 2011, Pekka Enberg wrote:

> It hanged here which is pretty much expected on this box if
> kmem_cache_init() oopses. I'm now trying to see if I'm able to find
> the config option that breaks things. CONFIG_PREEMPT_NONE is a
> suspect:
>
> penberg@...er:~/linux$ grep PREEMPT ../config-ingo
> # CONFIG_PREEMPT_RCU is not set
> CONFIG_PREEMPT_NONE=y
> # CONFIG_PREEMPT_VOLUNTARY is not set
> # CONFIG_PREEMPT is not set

The following patch should ensure that all percpu data is touched
before any emulation functions are called:

---
 mm/slub.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2011-03-24 14:03:10.000000000 -0500
+++ linux-2.6/mm/slub.c	2011-03-24 14:04:08.000000000 -0500
@@ -1604,7 +1604,7 @@ static inline void note_cmpxchg_failure(

 void init_kmem_cache_cpus(struct kmem_cache *s)
 {
-#if defined(CONFIG_CMPXCHG_LOCAL) && defined(CONFIG_PREEMPT)
+#ifdef CONFIG_CMPXCHG_LOCAL
 	int cpu;

 	for_each_possible_cpu(cpu)
--
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