From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gateway-1237.mvista.com (gateway-1237.mvista.com [63.81.120.158]) by ozlabs.org (Postfix) with ESMTP id 85F43DDE39 for ; Wed, 23 May 2007 10:29:15 +1000 (EST) Message-ID: <46538AE2.6010607@mvista.com> Date: Tue, 22 May 2007 17:29:22 -0700 From: Dave Jiang MIME-Version: 1.0 To: Geoff Levand Subject: Re: [RFC] BOOKE watchdog and kexec References: <46538264.2050000@mvista.com> <4653886A.30800@am.sony.com> In-Reply-To: <4653886A.30800@am.sony.com> Content-Type: text/plain; charset=UTF-8 Cc: linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Geoff Levand wrote: > Dave Jiang wrote: >> What would be the appropriate way to deal with the BOOKE watchdog in order to >> properly kexec? The BOOKE watchdog cannot be disabled. With the current >> implementation, a watchdog daemon in userland is required to poke the >> /dev/watchdog continously in order to keep it from going off. In the kexec >> situation, the watchdog daemon in userland goes away when the new kernel is >> executed. It is very possible that the new kernel can potentially timeout on a >> certain hardware device initialization (i.e. SCSI discovery/timeout) and causes >> the watchdog to go off and reset the hardware. The reset is of course not >> wanted in this situation. > > I would think the same situation exists when the bootloader loads the first > kernel. If that works, then you should be able to use the same mechanism to > get the second kernel up. > > -Geoff > Not really. The bootloader starts from a hardware reset. The watchdog is off from a hardware reset. The kernel driver has to specifically turn the watchdog on either via kernel command line or by opening the watchdog device /dev/watchdog right now. So technically this issue already exists even without kexec. If the watchdog is turned on via kernel parameter and we hit a device initialization timeout that takes too long, then we will get a watchdog reset. There is a period of uncertainty between the watchdog turning on and when the userland watchdog daemon is started with the current implementation. -- ------------------------------------------------------ Dave Jiang Software Engineer MontaVista Software, Inc. http://www.mvista.com ------------------------------------------------------