From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751948AbXCYRCF (ORCPT ); Sun, 25 Mar 2007 13:02:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751941AbXCYRCF (ORCPT ); Sun, 25 Mar 2007 13:02:05 -0400 Received: from sj-iport-6.cisco.com ([171.71.176.117]:15392 "EHLO sj-iport-6.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751948AbXCYRCE (ORCPT ); Sun, 25 Mar 2007 13:02:04 -0400 To: Ingo Molnar Cc: linux-kernel@vger.kernel.org Subject: Re: Early hang with 2.6.21-rc4-rt1 X-Message-Flag: Warning: May contain useful information References: <20070325073146.GB10734@elte.hu> From: Roland Dreier Date: Sun, 25 Mar 2007 10:01:58 -0700 In-Reply-To: (Roland Dreier's message of "Sun, 25 Mar 2007 07:35:22 -0700") Message-ID: User-Agent: Gnus/5.1007 (Gnus v5.10.7) XEmacs/21.4.19 (linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-OriginalArrivalTime: 25 Mar 2007 17:01:58.0790 (UTC) FILETIME=[4CD21260:01C76EFF] Authentication-Results: sj-dkim-2; header.From=rdreier@cisco.com; dkim=pass ( sig from cisco.com/sjdkim2002 verified; ); Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > I finally got curious enough to want to debug why starting kvm with > tun/tap networking produces a bunch of > > rtc: lost some interrupts at 1024Hz. > > messages. So I'm assuming it's a ~millisecond irqs-off section > somewhere. And after everything, it's a heisenbug -- I repeatably get that lost interrupts message on stock 2.6.21-rc4 but never on -rt1 with CONFIG_LATENCY_TRACE. Any suggestion of where to look? My /proc/latency_trace stays stubbornly empty -- are there any sysctls I need to change from their default to get latency tracing? I'm a complete noob when it comes to the -rt patch, so I'm not sure what the right way to use the tracing infrastructure to track down this lost rtc interrupts issue is. Thanks, Roland