linux-kernel - Re: [PATCH v4 5/7] Watchdog: introduce ARM SBSA watchdog driver

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Date:	Tue, 9 Jun 2015 00:10:42 +0800
From:	Fu Wei <fu.wei@...aro.org>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Timur Tabi <timur@...eaurora.org>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Linaro ACPI Mailman List <linaro-acpi@...ts.linaro.org>,
	linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	Wei Fu <tekkamanninja@...il.com>,
	G Gregory <graeme.gregory@...aro.org>,
	Al Stone <al.stone@...aro.org>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Ashwin Chaugule <ashwin.chaugule@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, vgandhi@...eaurora.org,
	wim@...ana.be, Jon Masters <jcm@...hat.com>,
	Leo Duran <leo.duran@....com>, Jon Corbet <corbet@....net>,
	Mark Rutland <mark.rutland@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>, rjw@...ysocki.net
Subject: Re: [PATCH v4 5/7] Watchdog: introduce ARM SBSA watchdog driver

Hi Guenter,


On 4 June 2015 at 02:25, Guenter Roeck <linux@...ck-us.net> wrote:
> On Wed, Jun 03, 2015 at 01:16:41PM -0500, Timur Tabi wrote:
>> On 06/01/2015 11:05 PM, fu.wei@...aro.org wrote:
>> >+    if (wdd->pretimeout)
>> >+            /* The pretimeout is valid, go panic */
>> >+            panic("SBSA Watchdog pre-timeout");
>>
>> The problem with this is that WS1 will still occur.  So a few seconds after
>> the panic() call, the hardware will reset.  There won't be any time to debug
>> or log anything.
>>
>
> In general the idea here would be to use a crashdump kernel, which,
> when loaded, would reset the watchdog before it fires. This kernel
> would then write a core dump to a specified location.
>
> If arm64 doesn't support a crashdump kernel, it might still be possible
> to log the backtrace somewhere (eg in nvram using pstore if that is
> supported via acpi or efi).

yes, you are right , thanks for explaining this.

>
> Is there reason to believe that this all won't work on arm64 ?

I don't think there is a reason.

>
> Thanks,
> Guenter



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat Software (Beijing) Co.,Ltd.Shanghai Branch
Ph: +86 21 61221326(direct)
Ph: +86 186 2020 4684 (mobile)
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