linux-kernel - Re: watchdog start on restart

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Message-ID: <e04bc12d-4520-89db-699c-ad89fcdbf76e@csgroup.eu>
Date:   Wed, 2 Sep 2020 15:19:56 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Ivan Mikhaylov <i.mikhaylov@...ro.com>
Cc:     Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: watchdog start on restart



Le 02/09/2020 à 15:02, Ivan Mikhaylov a écrit :
> Hello everyone. Currently, the watchdog interface only has "stop watchdog on
> restart" but lacks a "start watchdog on restart" one. Is there a way to achieve
> such functionality?
> 
> I'd like to know why "stop watchdog on restart" wasn't implemented via ioctl
> interface? It would be more convenient from user perspective and you can
> control that behavior whenever you want from application layer.
> 
> I have some thoughts on this problem that solve the aforementioned
> issue with "start watchdog on restart" but I don't think that my solution is
> correct.
> 


I don't understand why a "start watchdog on restart" would be needed. 
Isn't it the default expected behaviour for a watchdog ?

"stop watchdog on restart" is there to keep things under control during 
a wanted machine reboot/restart, while still having the watchdog do its 
job on an unexpected restart.

What would be the advantage of an ioctl() compared to the existing way ?

Christophe