Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761631Ab3IDXU6 (ORCPT ); Wed, 4 Sep 2013 19:20:58 -0400 Received: from mail-pd0-f176.google.com ([209.85.192.176]:46121 "EHLO mail-pd0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752525Ab3IDXU4 (ORCPT ); Wed, 4 Sep 2013 19:20:56 -0400 Message-ID: <5227C056.1020604@linaro.org> Date: Wed, 04 Sep 2013 16:20:54 -0700 From: John Stultz User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130803 Thunderbird/17.0.8 MIME-Version: 1.0 To: "H. Peter Anvin" CC: Andy Lutomirski , Arun Sharma , LKML , Kumar Sundararajan Subject: Re: clock_gettime_ns References: <5226FAE1.5070201@fb.com> <52279E1D.3060907@linaro.org> <5227B432.8070205@zytor.com> <5227BB50.7000301@linaro.org> <5227BC71.6000907@zytor.com> In-Reply-To: <5227BC71.6000907@zytor.com> X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1572 Lines: 34 On 09/04/2013 04:04 PM, H. Peter Anvin wrote: > On 09/04/2013 03:59 PM, John Stultz wrote: >> Also, there's been talk of a slewed-leap-second clockid, basically UTC >> but around the leapsecond it slows down to absorb the extra second. This >> means that clockid would have a subsecond offset from TAI. >> > Most of what I have heard seem to center around abolishing leap seconds > entirely. Now, I know that some users do slewed leap seconds as a > unofficial policy to avoid rare events. Well, Google does their own slewed leap-seconds internally (using a modified ntp server to slow CLOCK_REALTIME on clients), and I believe AIX also provides similar behavior w/ their CLOCK_REALTIME clockid (they also provide CLOCK_UTC for those who have the need for UTC/leapseconds). And there's also some occasional talk of trying to standardizing a leap-second free UTC. I suspect we have to have an all-of-the-above policy with the kernel. So we now (as of 3.10) support CLOCK_TAI, as well as the UTC-based CLOCK_REALTIME. If we can get some agreement on what the slewed-leapsecond adjustment should look like (have to decide what the slewing rate/range is: do we absorb the second over the last-hour, half-hour, 15-minutes before and after?), then we can add such a clockid (CLOCK_UTC_SLS?) to the kernel as well. thanks -john -- 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/