From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754086Ab1FBSNF (ORCPT ); Thu, 2 Jun 2011 14:13:05 -0400 Received: from usmamail.tilera.com ([206.83.70.75]:31782 "EHLO USMAMAIL.TILERA.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753916Ab1FBSNE (ORCPT ); Thu, 2 Jun 2011 14:13:04 -0400 Message-ID: <4DE7D2AC.1070503@tilera.com> Date: Thu, 2 Jun 2011 14:13:00 -0400 From: Chris Metcalf User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.17) Gecko/20110414 Lightning/1.0b2 Thunderbird/3.1.10 MIME-Version: 1.0 To: David Rientjes CC: Tejun Heo , Christoph Lameter , Pekka Enberg , Matt Mackall , , Subject: Re: [PATCH] slub: always align cpu_slab to honor cmpxchg_double requirement References: <201106021424.p52EO91O006974@lab-17.internal.tilera.com> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Thanks! >> > 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". Now it's not. I suppose we could take the comment change in percpu.h for 2.6.39, but it probably doesn't merit churning the stable tree. -- Chris Metcalf, Tilera Corp. http://www.tilera.com