Re: watchdog start on restart
From: Christophe Leroy
Date: Thu Sep 03 2020 - 07:18:08 EST
Le 03/09/2020 à 12:23, Ivan Mikhaylov a écrit :
On Wed, 2020-09-02 at 06:36 -0700, Guenter Roeck wrote:
On 9/2/20 6:02 AM, Ivan Mikhaylov wrote:
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.
Because it is and always was a driver level decision. The function was added
to replace lots of driver level code implementing this functionality.
Overriding it from userspace doesn't make sense because the driver is supposed
to have a reason for disabling it on reboot (for example due to clock issues
or power issues or becasue it has a short hardware timeout).
If it's only driver level decision then it makes sense.
That functionality doesn't make much sense. It can be accomplished by not
stopping the watchdog on reboot in the first place. And if the watchdog
wasn't running before, it can be started from userspace just before the
reboot.
I understand that it can be started from userspace. As example, I want the
watchdog trigger with guarantee that the userspace will be properly shut on
reboot, how can I get it with current interface? Just start before the reboot
doesn't guarantee that it will be triggered or will be triggered in middle
of reboot/restart.
I'm not sure I understand what you want to do.
You want to start the watchdog just before calling 'reboot' but want to
make sure that the watchdog will not reset the board before all
userspace has shut down correctly ?
But what is the purpose of the watchdog then, isn't it there to make
sure that the machine gets reboot within a given timeout anyway in case
some userspace takes too long to shut down ?
Christophe