From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753894AbZBSSEQ (ORCPT ); Thu, 19 Feb 2009 13:04:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752379AbZBSSD7 (ORCPT ); Thu, 19 Feb 2009 13:03:59 -0500 Received: from smtp-outbound-2.vmware.com ([65.115.85.73]:33079 "EHLO smtp-outbound-2.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752263AbZBSSD7 (ORCPT ); Thu, 19 Feb 2009 13:03:59 -0500 Subject: Re: x86, vmi: TSC going backwards check in vmi clocksource From: Alok Kataria Reply-To: akataria@vmware.com To: Ingo Molnar Cc: the arch/x86 maintainers , LKML , Zach Amsden In-Reply-To: <20090219111822.GN2354@elte.hu> References: <1234989235.7991.2.camel@alok-dev1> <20090219111822.GN2354@elte.hu> Content-Type: text/plain Organization: VMware INC. Date: Thu, 19 Feb 2009 10:03:58 -0800 Message-Id: <1235066638.23293.7.camel@alok-dev1> Mime-Version: 1.0 X-Mailer: Evolution 2.8.0 (2.8.0-40.el5_1.1) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Thanks, Alok > > Ingo