linux-kernel - Re: [PATCH v2 10/13] EDAC/altera: Skip the panic notifier if kdump is loaded

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Date:   Wed, 17 Aug 2022 15:45:30 -0300
From:   "Guilherme G. Piccoli" <gpiccoli@...lia.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     akpm@...ux-foundation.org, bhe@...hat.com, pmladek@...e.com,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org, netdev@...r.kernel.org,
        x86@...nel.org, kernel-dev@...lia.com, kernel@...ccoli.net,
        halves@...onical.com, fabiomirmar@...il.com,
        alejandro.j.jimenez@...cle.com, andriy.shevchenko@...ux.intel.com,
        arnd@...db.de, corbet@....net, d.hatayama@...fujitsu.com,
        dave.hansen@...ux.intel.com, dyoung@...hat.com,
        feng.tang@...el.com, gregkh@...uxfoundation.org,
        mikelley@...rosoft.com, hidehiro.kawai.ez@...achi.com,
        jgross@...e.com, john.ogness@...utronix.de, keescook@...omium.org,
        luto@...nel.org, mhiramat@...nel.org, mingo@...hat.com,
        paulmck@...nel.org, peterz@...radead.org, rostedt@...dmis.org,
        senozhatsky@...omium.org, stern@...land.harvard.edu,
        tglx@...utronix.de, vgoyal@...hat.com, vkuznets@...hat.com,
        will@...nel.org, linux-edac@...r.kernel.org,
        Dinh Nguyen <dinguyen@...nel.org>,
        Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH v2 10/13] EDAC/altera: Skip the panic notifier if kdump is
 loaded

On 17/08/2022 14:31, Borislav Petkov wrote:
> [...]
> 
> How does the fact that kdump is loaded, obviate the need to print
> information about the errors?
> 
> Are you suggesting that people who have the whole vmcore would be able
> to piece together the error information?
> 

Hi Boris, thanks for chiming in.

So, this is part of an effort to clean-up the panic path. Currently, if
a kdump happens, *all* the panic notifiers are skipped by default,
including this one. In this scenario, this patch seems like a no-op.

But happens that in the refactor we are proposing [0], some notifiers
should run before the kdump. We are basically putting some ordering in
the way notifiers are executed, while documenting this properly and with
the goal of not increasing the failure risk for kdump.

This patch is useful so we can bring the altera EDAC notifier to run
earlier while not increasing the risk on kdump - this operation is a bit
"delicate" to happen in the panic scenario. The origin of this patch was
a discussion with Tony/Peter [1], guess we can call it a "compromise
solution".

Let me know if you disagree or have more questions, and in case you'd
like to check/participate in the whole panic notifiers refactor
discussion, it would be great =)
Cheers,


Guilherme


[0]
https://lore.kernel.org/lkml/20220427224924.592546-1-gpiccoli@igalia.com/

[1]
https://lore.kernel.org/lkml/62a63fc2-346f-f375-043a-fa21385279df@igalia.com/