linux-kernel - Re: slub: use irqsafe_cpu_cmpxchg for put_cpu

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Message-ID: <1322064291.17693.54.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
Date:	Wed, 23 Nov 2011 17:04:51 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Pekka Enberg <penberg@...nel.org>,
	Christian Kujau <lists@...dbynature.de>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	"Alex,Shi" <alex.shi@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Matt Mackall <mpm@...enic.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>, David Rientjes <rientjes@...gle.com>
Subject: Re: slub: use irqsafe_cpu_cmpxchg for put_cpu_partial

Le mercredi 23 novembre 2011 à 09:14 -0600, Christoph Lameter a écrit :

> I think he only tested the patch that he showed us. Here is the patch
> cleaned up. Do you Want me to feed you the debug fixes patch by patch as
> well?
> 
> Subject: slub: use irqsafe_cpu_cmpxchg for put_cpu_partial
> 
> The cmpxchg must be irq safe. The fallback for this_cpu_cmpxchg only
> disables preemption which results in per cpu partial page operation
> potentially failing on non x86 platforms.
> 
> Signed-off-by: Christoph Lameter <cl@...ux.com>
> 
> ---
>  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	2011-11-23 09:10:48.000000000 -0600
> +++ linux-2.6/mm/slub.c	2011-11-23 09:10:57.000000000 -0600
> @@ -1969,7 +1969,7 @@ int put_cpu_partial(struct kmem_cache *s
>  		page->pobjects = pobjects;
>  		page->next = oldpage;
> 
> -	} while (this_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page) != oldpage);
> +	} while (irqsafe_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page) != oldpage);
>  	stat(s, CPU_PARTIAL_FREE);
>  	return pobjects;
>  }

Acked-by: Eric Dumazet <eric.dumazet@...il.com>

Thanks !


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