From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757999AbXKZA0n (ORCPT ); Sun, 25 Nov 2007 19:26:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756976AbXKZA0e (ORCPT ); Sun, 25 Nov 2007 19:26:34 -0500 Received: from vms173001pub.verizon.net ([206.46.173.1]:51011 "EHLO vms173001pub.verizon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756648AbXKZA0d (ORCPT ); Sun, 25 Nov 2007 19:26:33 -0500 X-Greylist: delayed 3599 seconds by postgrey-1.27 at vger.kernel.org; Sun, 25 Nov 2007 19:26:33 EST Date: Sun, 25 Nov 2007 17:26:27 -0600 From: Corey Minyard Subject: Re: ipmi_watchdog can not reset the kernel panic machine In-reply-to: <20071124223920.212b36e3.akpm@linux-foundation.org> To: youquan_song@linux.intel.com Cc: Andrew Morton , linux-kernel@vger.kernel.org, Wim Van Sebroeck Message-id: <474A04A3.8030702@acm.org> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit References: <2097.172.16.96.111.1195878521.squirrel@linux.intel.com> <20071124223920.212b36e3.akpm@linux-foundation.org> User-Agent: Icedove 1.5.0.14pre (X11/20071018) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org The watchdog is "off" by default, meaning that you have to have something actually start resetting the watchdog before it will start running. That's why you are seeing this behavior. There is a start_now option that will start the watchdog when it is loaded, but then it will reset the system unless something resets the watchdog periodically, and you have a limited time to start this operation. On a panic, the IPMI driver attempts to preserve the state of the watchdog and (if running) increase the timeout time to allow a kdump or something like that to occur. That's the purpose of the code you reference. It is not to start a reset operation on any panic. It used to start a reset on every panic, but that cause problems for many users. -corey Andrew Morton wrote: > (cc's added) > > On Fri, 23 Nov 2007 20:28:41 -0800 (PST) youquan_song@linux.intel.com wrote: > > >> Build kernel-2.6.24-rc3. pmi_watchdog can not reset the kernel panic >> machine. The watchdog can never to record panic information to IPMI SEL. >> >> 1. I disable auto reset when kernel panic by echo "0" > >> /proc/sys/kernel/panic >> >> 2. modprobe ipmi_watchdog timeout=120 action=reset >> >> 3. Load a driver, the driver will call panic() when ioctl to call into >> the driver. >> >> 4. By ioctl call into the driver, panic the system. >> >> in wdog_panic_handler, I printk "ipmi_watchdog_state=WDOG_TIMEOUT_NONE" >> so, the watchdog can never to record panic information to IPMI SEL. >> >> >> static int wdog_panic_handler(struct notifier_block *this, >> unsigned long event, >> void *unused) >> { >> static int panic_event_handled = 0; >> >> /* On a panic, if we have a panic timeout, make sure to extend >> the watchdog timer to a reasonable value to complete the >> panic, if the watchdog timer is running. Plus the >> pretimeout is meaningless at panic time. */ >> if (watchdog_user && !panic_event_handled && >> ipmi_watchdog_state != WDOG_TIMEOUT_NONE) { >> /* Make sure we do this only once. */ >> panic_event_handled = 1; >> >> timeout = 255; >> pretimeout = 0; >> panic_halt_ipmi_set_timeout(); >> } >> >> return NOTIFY_OK; >> } >>