From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755399Ab0JRVoP (ORCPT ); Mon, 18 Oct 2010 17:44:15 -0400 Received: from terminus.zytor.com ([198.137.202.10]:60266 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754707Ab0JRVoO (ORCPT ); Mon, 18 Oct 2010 17:44:14 -0400 Message-ID: <4CBCBF9D.1060409@zytor.com> Date: Mon, 18 Oct 2010 14:43:57 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc13 Thunderbird/3.1.4 MIME-Version: 1.0 To: David Rientjes CC: Thomas Gleixner , Frederic Weisbecker , LKML , Ingo Molnar Subject: Re: [PATCH 1/2] x86: Cleanup TIF value gaps in shift range References: <1287434158-24362-1-git-send-regression-fweisbec@gmail.com> <4CBCBBFC.1090500@zytor.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 10/18/2010 02:36 PM, David Rientjes wrote: > On Mon, 18 Oct 2010, H. Peter Anvin wrote: > >> The problem is that someone exports something as debugging information, >> then someone else suddenly thinks it's an ABI. I believe the same >> complainant in the past has objected to changing of formatting in dmesg, >> which is equally insane. >> > > It's not insane if there is no other way to ascertain that information. > If it's available through sysfs or debugfs (and, even better, documented > as part of the API in Documentation/ABI), then I don't think anyone would > object to changing a log message. But I don't think all log messages > should be fair game under some general principle if they are being changed > (instead of just extending it) without a compelling reason, such as > technically being incorrect in its present form. YES IT IS. In fact, it is completely and totally bananas bonkers. By not pushing for a proper maintainable ABI, you will have an indefinite forward compatibility problem, and when predictably it breaks, you'll complain. This is, however, backwards -- the right thing would have been to say "I need this, this isn't available, I should add a maintainable API and push it upstream", and perhaps add log parsing as a backwards-compatibility solution. -hpa