From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 14ACD6B004A for ; Fri, 3 Jun 2011 01:49:11 -0400 (EDT) Received: by gwaa12 with SMTP id a12so789936gwa.14 for ; Thu, 02 Jun 2011 22:49:10 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <4DE7D2AC.1070503@tilera.com> References: <201106021424.p52EO91O006974@lab-17.internal.tilera.com> <4DE7D2AC.1070503@tilera.com> Date: Fri, 3 Jun 2011 08:49:10 +0300 Message-ID: Subject: Re: [PATCH] slub: always align cpu_slab to honor cmpxchg_double requirement From: Pekka Enberg Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Chris Metcalf Cc: David Rientjes , Tejun Heo , Christoph Lameter , Matt Mackall , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Thu, Jun 2, 2011 at 9:13 PM, Chris Metcalf wrote: > On 6/2/2011 1:16 PM, David Rientjes wrote: >> On Thu, 2 Jun 2011, Chris Metcalf wrote: >>> On an architecture without CMPXCHG_LOCAL but with DEBUG_VM enabled, >>> the VM_BUG_ON() in __pcpu_double_call_return_bool() will cause an early >>> panic during boot unless we always align cpu_slab properly. >>> >>> In principle we could remove the alignment-testing VM_BUG_ON() for >>> architectures that don't have CMPXCHG_LOCAL, but leaving it in means >>> that new code will tend not to break x86 even if it is introduced >>> on another platform, and it's low cost to require alignment. >>> >>> Signed-off-by: Chris Metcalf >> Acked-by: David Rientjes >> >>> --- >>> This needs to be pushed for 3.0 to allow arch/tile to boot. >>> I'm happy to push it but I assume it would be better coming >>> from an mm or percpu tree. =A0Thanks! >>> >> Should also be marked for stable for 2.6.39.x, right? > > No, in 2.6.39 the irqsafe_cpu_cmpxchg_double() was guarded under "#ifdef > CONFIG_CMPXCHG_LOCAL". =A0Now it's not. =A0I suppose we could take the co= mment > change in percpu.h for 2.6.39, but it probably doesn't merit churning the > stable tree. Yup. Looks good. Christoph? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org