From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tina Yang Subject: netconsole problems Date: Thu, 04 Oct 2007 10:59:38 -0700 Message-ID: <47052A0A.2080100@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: Matt Mackall , netdev@vger.kernel.org Return-path: Received: from agminet01.oracle.com ([141.146.126.228]:37145 "EHLO agminet01.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756500AbXJDSDq (ORCPT ); Thu, 4 Oct 2007 14:03:46 -0400 Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org We recently run into a few problems with netconsole in at least 2.6.9, 2.6.18 and 2.6.23. It either panicked at netdevice.h:890 or hung the system, and sometimes depending on which NIC we are using, the following console message, e1000: "e1000: eth0: e1000_clean_tx_irq: Detected Tx Unit Hang" tg3: "NETDEV WATCHDOG: eth4: transmit timed out" "tg3: eth4: transmit timed out, resetting" The postmortem vmcore analysis indicated race between normal network stack (net_rx_action) and netpoll, and disabling the following code segment cures all the problems. netpoll.c 178 /* Process pending work on NIC */ 179 np->dev->poll_controller(np->dev); 180 if (np->dev->poll) 181 poll_napi(np); Big or small, there seems to be several race windows in the code, and fixing them probably has consequence on overall system performance. Maybe this code should only run when the machine is single-threaded ? Suggestions ? Thanks.