From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261802AbULBXak (ORCPT ); Thu, 2 Dec 2004 18:30:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261803AbULBXak (ORCPT ); Thu, 2 Dec 2004 18:30:40 -0500 Received: from ozlabs.org ([203.10.76.45]:54245 "EHLO ozlabs.org") by vger.kernel.org with ESMTP id S261802AbULBXae (ORCPT ); Thu, 2 Dec 2004 18:30:34 -0500 Date: Fri, 3 Dec 2004 10:28:03 +1100 From: Anton Blanchard To: john stultz Cc: David Vrabel , Linux Kernel , mann@vmware.com Subject: Re: Jiffy based timers/timeouts can expire too soon. Message-ID: <20041202232803.GA6387@krispykreme.ozlabs.ibm.com> References: <41AF3D50.4090707@arcom.com> <1102013246.13294.19.camel@cog.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1102013246.13294.19.camel@cog.beaverton.ibm.com> User-Agent: Mutt/1.5.6+20040907i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > Well, hopefully the lost tick detection code won't over compensate, so > it shouldn't be an issue. However, as Tim Mann pointed out it, due to > interrupt delay and queuing, it is seen on virtualized systems. We saw this on ppc64 on earlier 2.6 kernels. There were some bugs with the VM where interrupts would get disabled for a long time (we saw 20+ second periods). A SCSI timeout would occur on another CPU and at that time irqs would get reenabled and 20 seconds of time would get replayed. A bunch of timers would go off early and the SCSI adapter would explode. Anton