linux-kernel - Re: [PATCH 2/2] watchdog: dw_wdt: keepalive the watchdog at write time

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Message-ID: <554C15C2.60802@roeck-us.net>
Date:	Thu, 07 May 2015 18:47:46 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Doug Anderson <dianders@...omium.org>, wim@...ana.be
CC:	jszhang@...vell.com, linux-watchdog@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] watchdog: dw_wdt: keepalive the watchdog at write
 time

On 05/07/2015 03:09 PM, Doug Anderson wrote:
> If you've got code that does this in a tight loop
>    1. Open watchdog
>    2. Send 'expect close'
>    3. Close watchdog
> ...you'll eventually trigger a watchdog reset.  You can reproduce this
> by using daisydog (1) and running:
>    while true; do daisydog -c > /dev/null; done
>
> The problem is that each time you write to the watchdog for 'expect
> close' it moves the timer .5 seconds out.  The timer thus never fires
> and never pats the watchdog for you.
>
> 1: http://git.chromium.org/gitweb/?p=chromiumos/third_party/daisydog.git
>
> Signed-off-by: Doug Anderson <dianders@...omium.org>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>


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