Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753543AbZAEXD5 (ORCPT ); Mon, 5 Jan 2009 18:03:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750889AbZAEXDt (ORCPT ); Mon, 5 Jan 2009 18:03:49 -0500 Received: from yw-out-2324.google.com ([74.125.46.31]:18782 "EHLO yw-out-2324.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750823AbZAEXDs (ORCPT ); Mon, 5 Jan 2009 18:03:48 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:reply-to:to:subject:cc:in-reply-to :mime-version:content-type:content-transfer-encoding :content-disposition:references; b=nNlmCRc2l4+qG8zEiWwzx6wINlAR9JkIEKvf9MULqHzWLfo+0nhCzeDbu5OIV3GAov uW0NNa5rT1mA095LCwPcrusC79mta46dr1DcXD3/bQfKoINbSm4YzsOqgYTgcszJpg12 ZHzvyIF2dII4Tv7EjZ3Jfhn3Yl61Kd1ykfZvY= Message-ID: <3ae3aa420901051503s129c3cc0kb022d42f21550099@mail.gmail.com> Date: Mon, 5 Jan 2009 17:03:45 -0600 From: "Linas Vepstas" Reply-To: linasvepstas@gmail.com To: "David Newall" Subject: Re: Bug: Status/Summary of slashdot leap-second crash on new years 2008-2009 Cc: "Ben Goodger" , david@lang.hm, "Kyle Moffett" , "Robert Hancock" , linux-kernel@vger.kernel.org, "Jeffrey J. Kosowsky" , MentalMooMan , "Travis Crump" , burdell@iruntheinter.net In-Reply-To: <4961A9E2.9060601@davidnewall.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <3ae3aa420901021125n1153053fsdf2378e7d11abbc0@mail.gmail.com> <4960897D.5030603@davidnewall.com> <4961432A.80509@davidnewall.com> <49614835.7000505@davidnewall.com> <496150DF.2070501@davidnewall.com> <8752a8760901041621o51380e91x9ef8414b22c40ffc@mail.gmail.com> <4961A9E2.9060601@davidnewall.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1843 Lines: 47 2009/1/5 David Newall : > Zoneinfo files cater for leap seconds. As has been (repeatedly) pointed out, the leap seconds only apply to UTC, so there is no way, given UTC, to use a zoneinfo file to twiddle UTC. Your argument *might* work if the kernel maintained TEI instead of UTC. Then there could, in principle, be a zoneinfo file that converted from TEI to UTC (by adding 24 seconds to TEI). However, this requires converting the kernel to track TEI instead of UTC, and reviewing all sorts of code in the kernel, glibc, ntp, and myriads of other libraries to figure out what's affected and whats not. As well as figuring out how to twiddle zoneinfo files so that they're backwards/forwards compatible with the timekeeping change, so that users aren't screwed when they put new kernels on old distros, or new zonefiles on old kernels. This is a fairly big chunk of work, requiring coordination between lots of different parties. > If you know in advance, you can update zoneinfo files with multiple leap > seconds. Heh. You miss the point. The whole point of leap seconds is that they're unknowable in advance. You only know if they already happened, or seem likely to happen real soon now. The previously cited wikipedia article reviews this nicely. --linas p.s. Yes, you could say I'm coming around to your point of view. If you had said, from the begining, something like "the kernel should keep TEI instead of UTC, and compute UTC in user-space from the TEI time", then you might have met a lot less resistance. But that's not how your argument came across. -- 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/