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

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Message-ID: <fbbd0a8d-2ef4-4a39-4b75-354918e85778@igalia.com>
Date:   Wed, 18 May 2022 10:16:20 -0300
From:   "Guilherme G. Piccoli" <gpiccoli@...lia.com>
To:     Petr Mladek <pmladek@...e.com>
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Subject: Re: [PATCH 19/30] panic: Add the panic hypervisor notifier list

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.

Makes sense to you ?
Cheers!