From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754462AbbBJXra (ORCPT ); Tue, 10 Feb 2015 18:47:30 -0500 Received: from mail-qa0-f52.google.com ([209.85.216.52]:33510 "EHLO mail-qa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751511AbbBJXr3 (ORCPT ); Tue, 10 Feb 2015 18:47:29 -0500 MIME-Version: 1.0 In-Reply-To: <1423333779-9857-1-git-send-email-prarit@redhat.com> References: <1423333779-9857-1-git-send-email-prarit@redhat.com> Date: Wed, 11 Feb 2015 07:47:28 +0800 Message-ID: Subject: Re: [PATCH] time, ntp: Do not update time_state in middle of leap second From: John Stultz To: Prarit Bhargava Cc: lkml , Thomas Gleixner , Miroslav Lichvar Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Feb 8, 2015 at 2:29 AM, Prarit Bhargava wrote: > During leap second insertion testing it was noticed that a small window > exists where the time_state could be reset such that > time_state = TIME_OK, which then causes the leap second to not occur, or > causes the entire leap second state machine to fail. I think this description is fairly opaque, and probably needs the specific example of the state change transitions that motivates this patch. > While this is highly unlikely to ever happen in the real world it is > still something we should protect against, as breaking the state machine > is obviously bad. In this case it was a test-case bug where uninitialized data being passed to adjtimex (when the test intended to only read the time state) was causing an unexpected state change transition. So its not immediately obvious that resetting the state machine when the root called adjtimex is invalid, so it would be good to make this more clear and explicit (ie: show the expected state transitions and the command that caused the strange transition you saw). Sorry for the slow response here, I've been on the fence as to if this is the right thing or not, and have needed to get some time to stare at this a bit more to see if I can convince myself its the right thing, so improving the commit message might make it more obvious to me and others. :) thanks -john