Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932311AbVINSyp (ORCPT ); Wed, 14 Sep 2005 14:54:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932495AbVINSyp (ORCPT ); Wed, 14 Sep 2005 14:54:45 -0400 Received: from e33.co.us.ibm.com ([32.97.110.131]:22736 "EHLO e33.co.us.ibm.com") by vger.kernel.org with ESMTP id S932311AbVINSyo (ORCPT ); Wed, 14 Sep 2005 14:54:44 -0400 Subject: Re: NTP leap second question From: john stultz To: george@mvista.com Cc: lkml , yoshfuji@linux-ipv6.org, Roman Zippel , Ulrich Windl , joe-lkml@rameria.de In-Reply-To: <43286E4B.1070809@mvista.com> References: <1126720091.3455.56.camel@cog.beaverton.ibm.com> <1126720398.3455.58.camel@cog.beaverton.ibm.com> <43286E4B.1070809@mvista.com> Content-Type: text/plain Date: Wed, 14 Sep 2005 11:54:12 -0700 Message-Id: <1126724052.3455.80.camel@cog.beaverton.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1526 Lines: 32 On Wed, 2005-09-14 at 11:39 -0700, George Anzinger wrote: > It appears that a leap second is scheduled. One of our customers is > concerened about his application around this. Could one of you NTP > wizards help me to understand NTP a bit better. First: I'm not an NTP wizard by any means, but I'll see if I can't help. > First, I wonder if we suppressed the leap second insert and time then > became out of sync by a second, would NTP "creap" the time back in sync > or would the one second out of sync cause it to quit? The ntpd's slew-bound is .125s I believe, so a second offset would cause ntpd to adjust the time using stime()/settimeofday(). You could run ntpd with the -x option which forces it to always slew the clock. This however could cause the initial sync to take quite some time. > Assuming NTP would do the "creap" thing, is there a way to tell NTP not > to insert the leap second? If I recall, leapsecond implementations are a pretty contentious issue. Some folks have suggested having the kernels note the leapsecond and slew the clock internally. This sounds nicer then just adding or removing a second, but I do not know how that would affect synchronizing between a number of systems. So I'll defer the larger discussion to the real NTP wizards. - 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/