From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dale Swanston Subject: setting time in guest with ntpdate results in VM hang Date: Fri, 24 Aug 2012 09:57:35 -0600 Message-ID: <5037A46F.7050104@sedsystems.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: kvm@vger.kernel.org Return-path: Received: from sed198n136.SEDSystems.ca ([198.169.180.136]:1255 "EHLO sed198n136.sedsystems.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759856Ab2HXQaH (ORCPT ); Fri, 24 Aug 2012 12:30:07 -0400 Received: from barney.sedsystems.ca (barney [198.169.180.121]) by sed198n136.sedsystems.ca with ESMTP id q7OFvbMX008230 (version=TLSv1/SSLv3 cipher=DHE-DSS-AES256-SHA bits=256 verify=NOT) for ; Fri, 24 Aug 2012 09:57:37 -0600 (CST) Received: from [192.107.131.83] (sed192n83.SEDSystems.ca [192.107.131.83]) by barney.sedsystems.ca (8.13.1/8.13.1) with ESMTP id q7OFvZ4E004124 for ; Fri, 24 Aug 2012 09:57:35 -0600 Sender: kvm-owner@vger.kernel.org List-ID: Hello. We are running a guest OS of CentOS 4.4 (kernel 2.6.12) for legacy reasons, upgrading is not an option. NTP is running on the host and synching with a local GPS NTP server. But due to frequency drift in the guest it restarts itself periodically and upon start up performs an ntpdate to force a time jump on the guest. I have seen 2 occasions now (over 2 months) where the VM hangs right as the ntpdate command alters the guest clock (based on output in /var/log/messages). From the host's perspective the VM is still running but it appears to be using very high CPU percentage (more than typical). The only recovery option is to force shutdown of the VM and restart it. 1. Are there any known issues with ntpdate and VMs hanging? Any workarounds? 2. Are there any debugging tools further characterise the problem? Thanks in advance, Dale Further specifics, let me know if more details are needed: Host: # uname -a Linux s1pscu01host 2.6.32-220.el6.x86_64 #1 SMP Sat Dec 10 17:04:11 CST 2011 x86_64 x86_64 x86_64 GNU/Linux on Intel(R) Xeon(R) CPU E5620 @ 2.40GHz with qemu-kvm-0.12.1.2-2.209.el6.x86_64 Guest: I don't use any kernel time modifiers in the guest ... kernel /vmlinuz-2.6.12 ro root=/dev/VolGroup00/LogVol00 rhgb quiet CentOS 4.4