linux-kernel - Re: [PATCH 19/30] panic: Add the panic hypervisor notifier list

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Message-ID: <YoXr2AD+Jc/ukUhJ@alley>
Date:   Thu, 19 May 2022 09:03:52 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     "Guilherme G. Piccoli" <gpiccoli@...lia.com>
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Subject: Re: [PATCH 19/30] panic: Add the panic hypervisor notifier list

On Wed 2022-05-18 10:16:20, Guilherme G. Piccoli wrote:
> On 18/05/2022 04:58, Petr Mladek wrote:
> > [...]
> >> I does similar things like kmsg_dump() so it should be called in
> >> the same location (after info notifier list and before kdump).
> >>
> >> A solution might be to put it at these notifiers at the very
> >> end of the "info" list or make extra "dump" notifier list.
> > 
> > I just want to point out that the above idea has problems.
> > Notifiers storing kernel log need to be treated as kmsg_dump().
> > In particular, we would  need to know if there are any.
> > We do not need to call "info" notifier list before kdump
> > when there is no kernel log dumper registered.
> > 
> 
> Notifiers respect the priority concept, which is just a number that
> orders the list addition (and the list is called in order).
> 
> I've used the last position to panic_print() [in patch 25] - one idea
> here is to "reserve" the last position (represented by INT_MIN) for
> notifiers that act like kmsg_dump(). I couldn't find any IIRC, but that
> doesn't prevent us to save this position and comment about that.

I would ignore it for now. If anyone would want to safe the log
then they would need to read it. They will most likely use
the existing kmsg_dump() infastructure. In fact, they should
use it to avoid a code duplication.

Best Regards,
Petr