Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754540AbaJUIXs (ORCPT ); Tue, 21 Oct 2014 04:23:48 -0400 Received: from www.linutronix.de ([62.245.132.108]:57526 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754482AbaJUIXp (ORCPT ); Tue, 21 Oct 2014 04:23:45 -0400 Date: Tue, 21 Oct 2014 10:23:40 +0200 (CEST) From: Thomas Gleixner To: Thomas Shao cc: John Stultz , "gregkh@linuxfoundation.org" , LKML , "devel@linuxdriverproject.org" , "olaf@aepfle.de" , "apw@canonical.com" , "jasowang@redhat.com" , KY Srinivasan , Richard Cochran Subject: RE: [PATCH v2 1/2] timekeeping: add EXPORT_SYMBOL_GPL for do_adjtimex() In-Reply-To: Message-ID: References: <1413362372-16236-1-git-send-email-huishao@microsoft.com> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 21 Oct 2014, Thomas Shao wrote: > I didn't find a way to detect whether NTPd is running in the hyper-v module. And you better do not try at all. > In http://doc.ntp.org/4.1.0/ntpd.htm, it mentioned: Normally, the > time is slewed if the offset is less than the step threshold, which > is 128 ms by default, and stepped if above the threshold. > > In my implementation, I use 100ms as the threshold (maybe I should > change to 128?). If the time difference is less than 100ms, I just > do nothing. So, if NTPd is running, ideally it could keep the time > drift less than 128, so the adjustment in my patch will not get > triggered. Your implementation has nothing to do with NTP at all. It's not even close to NTP. It's a random hack to inject host time or slew into timekeeping with the precision of a random number generator. > And moreover, by default, the guest-host time sync is turn > off. There is a module parameter to control it. We'll also document > customer that do not turn on this if NTP is configured. Pretty well thought out mechanism to ensure that people will get it wrong in the first place. Thanks, tglx -- 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/