Subject: Re: [PATCH 3/3] panic: Allow printing extra panic information on
 kdump
To:     Dave Young <dyoung@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-doc@vger.kernel.org, mcgrof@kernel.org,
        keescook@chromium.org, yzaikin@google.com,
        akpm@linux-foundation.org, feng.tang@intel.com,
        siglesias@igalia.com, kernel@gpiccoli.net,
        kexec@lists.infradead.org
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From:   "Guilherme G. Piccoli" <gpiccoli@igalia.com>
Message-ID: <5b817a4f-0bba-7d79-8aab-33c58e922293@igalia.com>
Date:   Sat, 25 Dec 2021 16:21:17 -0300
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On 23/12/2021 22:35, Dave Young wrote:
> Hi Guilherme,
> [...]
> If only the doc update, I think it is fine to be another follup-up
> patch.
> 
> About your 1st option in patch log, there is crash_kexec_post_notifiers
> kernel param which can be used to switch on panic notifiers before kdump
> bootup.   Another way probably you can try to move panic print to be
> panic notifier. Have this been discussed before? 
> 

Hey Dave, thanks for the suggestion. I've considered that but didn't
like the idea. My reasoning was: allowing post notifiers on kdump will
highly compromise the reliability, whereas the panic_print is a solo
option, and not very invasive.

To mix it with all panic notifiers would just increase a lot the risk of
a kdump failure. Put in other words: if I'm a kdump user and in order to
have this panic_print setting I'd also need to enable post notifiers,
certainly I'll not use the feature, 'cause I don't wanna risk kdump too
much.

One other option I've considered however, and I'd appreciate your
opinion here, would be a new option on crash_kexec_post_notifiers that
allows the users to select *which few notifiers* they want to enable.
Currently it's all or nothing, and this approach is too heavy/risky I
believe. Allowing customization on which post notifiers the user wants
would be much better and in this case, having a post notifier for
panic_print makes a lot of sense. What do you think?

Thanks!