linux-kernel - Re: [PATCH v10 5/5] Watchdog: ARM SBSA Generic Watchdog half timeout panic support

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Message-ID: <56B3631F.6090304@roeck-us.net>
Date:	Thu, 4 Feb 2016 06:41:35 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Timur Tabi <timur@...eaurora.org>, Fu Wei <fu.wei@...aro.org>
Cc:	Rob Herring <robh+dt@...nel.org>,
	Paweł Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Wim Van Sebroeck <wim@...ana.be>,
	Jon Corbet <corbet@....net>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-watchdog@...r.kernel.org, linux-doc@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Linaro ACPI Mailman List <linaro-acpi@...ts.linaro.org>,
	rruigrok@...eaurora.org, "Abdulhamid, Harb" <harba@...eaurora.org>,
	Christopher Covington <cov@...eaurora.org>,
	Dave Young <dyoung@...hat.com>,
	Pratyush Anand <panand@...hat.com>,
	G Gregory <graeme.gregory@...aro.org>,
	Al Stone <al.stone@...aro.org>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Jon Masters <jcm@...hat.com>, Arnd Bergmann <arnd@...db.de>,
	Leo Duran <leo.duran@....com>,
	Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v10 5/5] Watchdog: ARM SBSA Generic Watchdog half timeout
 panic support

On 02/04/2016 05:48 AM, Timur Tabi wrote:
> Guenter Roeck wrote:
>> Also, if panic is enabled, the timeout needs to be adjusted accordingly
>> (to only panic after the entire timeout period has expired, not after
>> half of it). We can not panic the system after timeout / 2.
>
> It's a debugging feature, not an actual watchdog timeout panic.  That's why it's disabled by default.
>

"* When the first stage(the half timeout) is reached, WS0 interrupt is
  * triggered, at this moment the second watch period starts;
  * In the WS0 interrupt routine, panic will be triggered for saving the
  * system context.
  * If the system is getting into trouble and cannot be reset by panic or
  * restart properly by the kdump kernel(if supported), then the second
  * stage (the timeout) will be reached, system will be reset by WS1."

That doesn't sound like debugging to me.

Guenter