netdev - Re: [PATCH 11/30] um: Improve panic notifiers consistency and ordering

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Message-ID: <4b003501-f5c3-cd66-d222-88d98c93e141@igalia.com>
Date:   Wed, 11 May 2022 17:22:22 -0300
From:   "Guilherme G. Piccoli" <gpiccoli@...lia.com>
To:     Petr Mladek <pmladek@...e.com>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        Richard Weinberger <richard@....at>
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Subject: Re: [PATCH 11/30] um: Improve panic notifiers consistency and
 ordering

On 10/05/2022 11:28, Petr Mladek wrote:
> [...]
> It is not clear to me why user mode linux should not care about
> the other notifiers. It might be because I do not know much
> about the user mode linux.
> 
> Is the because they always create core dump or are never running
> in a hypervisor or ...?
> 
> AFAIK, the notifiers do many different things. For example, there
> is a notifier that disables RCU watchdog, print some extra
> information. Why none of them make sense here?
>

Hi Petr, my understanding is that UML is a form of running Linux as a
regular userspace process for testing purposes. With that said, as soon
as we exit in the error path, less "pollution" would happen, so users
can use GDB to debug the core dump for example.

In later patches of this series (when we split the panic notifiers in 3
lists) these UML notifiers run in the pre-reboot list, so they run after
the informational notifiers for example (in the default level).
But without the list split we cannot order properly, so my gut feeling
is that makes sense to run them rather earlier than later in the panic
process...

Maybe Anton / Johannes / Richard could give their opinions - appreciate
that, I'm not attached to the priority here, it's more about users'
common usage of UML I can think of...

Cheers,


Guilherme