From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from bh-25.webhostbox.net ([208.91.199.152]:52043 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750738AbbHEHua (ORCPT ); Wed, 5 Aug 2015 03:50:30 -0400 Message-ID: <55C1C041.3080504@roeck-us.net> Date: Wed, 05 Aug 2015 00:50:25 -0700 From: Guenter Roeck MIME-Version: 1.0 To: =?windows-1252?Q?Uwe_Kleine-K=F6nig?= , =?windows-1252?Q?P=E1draig_Brady?= CC: linux-watchdog@vger.kernel.org, Wim Van Sebroeck , linux-kernel@vger.kernel.org, Timo Kokkonen , linux-doc@vger.kernel.org, Jonathan Corbet Subject: Re: [PATCH 0/8] watchdog: Add support for keepalives triggered by infrastructure References: <1438654414-29259-1-git-send-email-linux@roeck-us.net> <55C14E2B.1080904@draigBrady.com> <20150805073605.GW9999@pengutronix.de> In-Reply-To: <20150805073605.GW9999@pengutronix.de> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Sender: linux-watchdog-owner@vger.kernel.org List-Id: linux-watchdog@vger.kernel.org Hi Uwe, On 08/05/2015 12:36 AM, Uwe Kleine-K=F6nig wrote: > Hello P=E1draig, > > On Wed, Aug 05, 2015 at 12:43:39AM +0100, P=E1draig Brady wrote: >> On 04/08/15 03:13, Guenter Roeck wrote: >>> The watchdog infrastructure is currently purely passive, meaning >>> it only passes information from user space to drivers and vice vers= a. >>> >>> Since watchdog hardware tends to have its own quirks, this can resu= lt >>> in quite complex watchdog drivers. A number of scanarios are especi= ally common. >>> >>> - A watchdog is always active and can not be disabled, or can not b= e disabled >>> once enabled. To support such hardware, watchdog drivers have to= implement >>> their own timers and use those timers to trigger watchdog keepal= ives while >>> the watchdog device is not or not yet opened. >>> - A variant of this is the desire to enable a watchdog as soon as i= ts driver >>> has been instantiated, to protect the system while it is still b= ooting up, >>> but the watchdog daemon is not yet running. >> >> Just mentioning that patting the watchdog in the boot loader >> (by patching grub etc.) can be a more general solution here as it >> avoids hangs if the kernel crashes before it runs the watchdog drive= r, >> which is especially true if PXE loaded across the net for example. >> Also this tends to be better spaced between boot start and user spac= e loading. > > the watchdog I'm currently working with on a powerpc platform has a > unchangable timeout of ~1 s. To make the machine boot I patched the > bootloader and need some automatic pinging in the kernel before > userspace takes over. > Does using arch_initcall in the watchdog driver help here, or is that still too slow and you really need to hack the kernel ? Thanks, Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-watchdo= g" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html