From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754007AbbBFKuu (ORCPT ); Fri, 6 Feb 2015 05:50:50 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53878 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751179AbbBFKut (ORCPT ); Fri, 6 Feb 2015 05:50:49 -0500 Message-ID: <54D49C83.40706@redhat.com> Date: Fri, 06 Feb 2015 05:50:43 -0500 From: Prarit Bhargava User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131028 Thunderbird/17.0.10 MIME-Version: 1.0 To: Miroslav Lichvar CC: John Stultz , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: Re: [PATCH] time, ntp: Do not update time_state in middle of leap References: <20150204163005.GF26460@localhost> <54D36E08.1060400@redhat.com> <20150206103815.GB23998@localhost> In-Reply-To: <20150206103815.GB23998@localhost> 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 02/06/2015 05:38 AM, Miroslav Lichvar wrote: > On Thu, Feb 05, 2015 at 08:20:08AM -0500, Prarit Bhargava wrote: >> On 02/04/2015 11:30 AM, Miroslav Lichvar wrote: >>> If after that, adjtimex() will return with TIME_ERROR as expected, or >>> not? >> >> It is possible that an adjtimex() will set the time_state here back to TIME_OK >> and return TIME_OK to userspace. Again, and I want to stress this, this is >> extremely unlikely to happen. I only hit this due to a bug in a test program. >> But at the end of the day, it is possible that this happens and we should >> protect against it. > > Could it break any applications? I guess PLL is normally disabled only > when a time synchronization process ends. FWIW, the reference > nanokernel implementation has this too. Not that I saw. I did take a look with top, etc., to see if anything in userspace went bad, and I ran programs that were calling gettimeofday() and clock_gettime() to see if there were any problems. I didn't see anything. I also played around with a program to see if the timer expiry failed but again, didn't see anything. The outcome of TIME_INS->TIME_OOP->TIME_OK->TIME_INS, AFAICT was only that TIME_INS was left issued. Which could lead to another leap second insertion down the road unless ntp (or some other program) was left to reset the state. > >>>> - if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) { >>>> + if ((time_status & STA_PLL) && !(txc->status & STA_PLL) && >>>> + (time_state != TIME_OOP)) { >>>> time_state = TIME_OK; >>>> time_status = STA_UNSYNC; >>>> /* restart PPS frequency calibration */ >>> >>> Shouldn't be time_status reset and the PPS calibration restarted even >>> when state is TIME_OOP? >> >> No, this should only happen after the leap second is done IMO (which should be >> no more than 2 seconds later). > > But that will not happen automatically, the application would have to > enable and disable the PLL again. Interestingly, the "time_status = > STA_UNSYNC" assignment doesn't seem to do anything here, as the Hmmm ... good point. I didn't think of that. Let me go back and change the code to do the reset. > variable is always reset couple lines after that, STA_UNSYNC is not a > readonly flag. > P.