Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752173Ab2H3Jth (ORCPT ); Thu, 30 Aug 2012 05:49:37 -0400 Received: from e28smtp02.in.ibm.com ([122.248.162.2]:41281 "EHLO e28smtp02.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751103Ab2H3Jtf (ORCPT ); Thu, 30 Aug 2012 05:49:35 -0400 Message-ID: <503F36C4.50004@linux.vnet.ibm.com> Date: Thu, 30 Aug 2012 15:17:48 +0530 From: "Naveen N. Rao" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 MIME-Version: 1.0 To: "Luck, Tony" , Borislav Petkov CC: "andi@firstfloor.org" , "ananth@in.ibm.com" , "x86@kernel.org" , "linux-kernel@vger.kernel.org" , "mingo@redhat.com" , "hpa@zytor.com" , "tglx@linutronix.de" , "linux-edac@vger.kernel.org" Subject: Re: [PATCH RFC] x86/mce: Move MCE sysfs attributes out of the per-cpu location References: <20120829074154.6755.98941.stgit@localhost.localdomain> <20120829101302.GA26977@aftab.osrc.amd.com> <3908561D78D1C84285E8C5FCA982C28F193989D6@ORSMSX104.amr.corp.intel.com> In-Reply-To: <3908561D78D1C84285E8C5FCA982C28F193989D6@ORSMSX104.amr.corp.intel.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit x-cbid: 12083009-5816-0000-0000-000004379573 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1549 Lines: 41 On 08/29/2012 08:13 PM, Luck, Tony wrote: >> Note: I'm not sure if it's ok to change sysfs entries and this does break >> userspace tools that depend on the current path for some of these attributes. >> So, they will need to be updated to use the new path. However, if we ever get >> to a point where cpu0 can be offlined, these tools will need to be updated >> anyway (as they mostly hardcode machinecheck0 currently) > > Linus' clarified his "never break user space" edict at the kernel summit > on Monday. Paraphrasing: > > If nobody notices, or nobody complains, then we can make changes. But > if anyone does complain, then the patch gets reverted. > > So if you want to do this, the right approach would be to change the > utilities that use this to look in the new location for these sysfs files > first, and fall back to looking in the old per-cpu place. > > Next (or in parallel) have the kernel provide both interfaces. > > Wait a long[1] time so that most people have updated utilities. > > Delete the per-cpu interfaces from the kernel. > > Delete the per-cpu references from the utilities. > > -Tony > > [1] Long enough that there are no complaints. At least a year, probably two or more. > Makes sense. Thanks for the explanation. I will send a new patch for this. Thanks, Naveen -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/