Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751818AbbHEHuc (ORCPT ); Wed, 5 Aug 2015 03:50:32 -0400 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 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0 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: 8bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: linux@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1992 Lines: 44 Hi Uwe, On 08/05/2015 12:36 AM, Uwe Kleine-K?nig wrote: > Hello P?draig, > > On Wed, Aug 05, 2015 at 12:43:39AM +0100, P?draig 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 versa. >>> >>> Since watchdog hardware tends to have its own quirks, this can result >>> in quite complex watchdog drivers. A number of scanarios are especially common. >>> >>> - A watchdog is always active and can not be disabled, or can not be disabled >>> once enabled. To support such hardware, watchdog drivers have to implement >>> their own timers and use those timers to trigger watchdog keepalives while >>> the watchdog device is not or not yet opened. >>> - A variant of this is the desire to enable a watchdog as soon as its driver >>> has been instantiated, to protect the system while it is still booting 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 driver, >> which is especially true if PXE loaded across the net for example. >> Also this tends to be better spaced between boot start and user space 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-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/