Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751616Ab3FEDJF (ORCPT ); Tue, 4 Jun 2013 23:09:05 -0400 Received: from mail-wi0-f173.google.com ([209.85.212.173]:41266 "EHLO mail-wi0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750791Ab3FEDJB (ORCPT ); Tue, 4 Jun 2013 23:09:01 -0400 MIME-Version: 1.0 In-Reply-To: References: <1370167987-14252-1-git-send-email-anish198519851985@gmail.com> <20130603152725.GA2644@roeck-us.net> <20130603222514.GA9082@roeck-us.net> Date: Wed, 5 Jun 2013 08:39:00 +0530 Message-ID: Subject: Re: [PATCH] [RFC]Watchdog:core: constant pinging until userspace timesout when delay very less From: anish singh To: Guenter Roeck , randy.dunlap@oracle.com, "alan@lxorguk.ukuu.org.uk" Cc: Wim Van Sebroeck , linux-watchdog@vger.kernel.org, linux-kernel-mail Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2765 Lines: 59 Hello Wim Van Sabroeck, Can I get your inputs on this? On Tue, Jun 4, 2013 at 8:39 AM, anish singh wrote: > On Tue, Jun 4, 2013 at 3:55 AM, Guenter Roeck wrote: >> On Mon, Jun 03, 2013 at 10:23:04PM +0530, anish singh wrote: >>> On Mon, Jun 3, 2013 at 8:57 PM, Guenter Roeck wrote: >>> > On Sun, Jun 02, 2013 at 03:43:07PM +0530, anish kumar wrote: >>> >> Certain watchdog drivers use a timer to keep kicking the watchdog at >>> >> a rate of 0.5s (HZ/2) untill userspace times out.They do this as >>> >> we can't guarantee that watchdog will be pinged fast enough >>> >> for all system loads, especially if timeout is configured for >>> >> less than or equal to 1 second(basically small values). >>> >> >>> >> As suggested by Wim Van Sebroeck & Guenter Roeck we should >>> >> add this functionality of individual watchdog drivers in the core >>> >> watchdog core. >>> >> >>> >> Signed-off-by: anish kumar >>> > >>> > Not exactly what I had in mind. My idea was to enable the softdog only if >>> > the hardware watchdog's maximum timeout was low (say, less than a couple >>> > of minutes), and if a timeout larger than its maximum value was configured. >>> >>> watchdog_timeout_invalid wouldn't this check will fail if the user space tries >>> to set maximum timeout more that what driver can support?It would work >>> for pika_wdt.c as it is old watchdog driver and doesn't register with watchdog >>> framwork but new drivers has to pass this api. >>> >>> OR >>> >>> Do you want to remove this check and go as explained by you?I would >>> favour this approach though. >>> >> One would still have a check, but the enforced limits would no longer be >> the driver limits, but larger limits implemented in the watchdog core. > How much larger would be the big question here?Should it be configurable > property(sysfs?) or some hardcoding based on existing drivers? > > Before going for next patch, it would be better for me to wait for some > more comments. >> >>> > In that case, I would have set the hardware watchdog to its maximum value >>> > and use the softdog to ping it at a rate of, say, 50% of this maximum. >>> > >>> > If userspace would not ping the watchdog within its configured value, >>> > I would stop pinging the hardware watchdog and let it time out. >>> >>> One more question.Why is the return value of watchdog_ping int? Anyway >>> we discard it. >> >> I can not answer that question. >> >> 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/