From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753575AbYDGGdp (ORCPT ); Mon, 7 Apr 2008 02:33:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751566AbYDGGdg (ORCPT ); Mon, 7 Apr 2008 02:33:36 -0400 Received: from www.tglx.de ([62.245.132.106]:41489 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751493AbYDGGdf (ORCPT ); Mon, 7 Apr 2008 02:33:35 -0400 Date: Mon, 7 Apr 2008 08:27:55 +0200 (CEST) From: Thomas Gleixner To: Roman Zippel cc: john stultz , Paul Mackerras , Tony Luck , Ingo Molnar , lkml Subject: Re: [PATCH] Close small window for vsyscall time inconsistencies In-Reply-To: <200804070255.22516.zippel@linux-m68k.org> Message-ID: References: <1207340264.6222.17.camel@localhost.localdomain> <200804070255.22516.zippel@linux-m68k.org> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 7 Apr 2008, Roman Zippel wrote: > Hi, > > On Friday 4. April 2008, john stultz wrote: > > > So Thomas and Ingo pointed out to me that they were occasionally seeing > > small 1ns inconsistencies from clock_gettime() (and more rarely, 1us > > inconsistencies from gettimeofday() when the 1ns inconsistency occurred > > on a us boundary) > > What does inconsistency mean? Time is going backwards by 1us/1nsec. > So instead of shooting in the dark, I'd suggest to collect some > numbers first, That's what we did and John's analysis of the problem is pretty correct. Thanks, tglx