From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755307AbZBSSLy (ORCPT ); Thu, 19 Feb 2009 13:11:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752414AbZBSSLq (ORCPT ); Thu, 19 Feb 2009 13:11:46 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:46669 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752015AbZBSSLp (ORCPT ); Thu, 19 Feb 2009 13:11:45 -0500 Date: Thu, 19 Feb 2009 19:11:32 +0100 From: Ingo Molnar To: Alok Kataria Cc: the arch/x86 maintainers , LKML , Zach Amsden Subject: Re: x86, vmi: TSC going backwards check in vmi clocksource Message-ID: <20090219181132.GA11477@elte.hu> References: <1234989235.7991.2.camel@alok-dev1> <20090219111822.GN2354@elte.hu> <1235066638.23293.7.camel@alok-dev1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1235066638.23293.7.camel@alok-dev1> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Alok Kataria wrote: > On Thu, 2009-02-19 at 03:18 -0800, Ingo Molnar wrote: > > * Alok Kataria wrote: > > > > > From: Alok N Kataria > > > > > > Similar to the check for TSC going backwards in the TSC > > > clocksource, we also need this check for VMI clocksource. > > > > ok. Precisely what kind of bug/symptoms does this fix? > > If the read CYCLES_REAL counter value is less than the cycle_last value, > it may result in time jumps. > I also saw some messages about process being stuck for more than > 120sec, which was traced back to this. Applied to tip:x86/urgent, thanks Alok! Ingo