linux-kernel - Re: [PATCH] Documentation: Improve crash_kexec_post

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Message-ID: <87ed66q6d5.fsf@oracle.com>
Date: Fri, 30 Aug 2024 10:15:50 -0700
From: Stephen Brennan <stephen.s.brennan@...cle.com>
To: "Guilherme G. Piccoli" <gpiccoli@...lia.com>, kexec@...ts.infradead.org,
        linux-doc@...r.kernel.org
Cc: bhe@...hat.com, vgoyal@...hat.com, dyoung@...hat.com, corbet@....net,
        linux-kernel@...r.kernel.org, linux-debuggers@...r.kernel.org,
        kernel@...ccoli.net, kernel-dev@...lia.com,
        "Guilherme G. Piccoli"
 <gpiccoli@...lia.com>
Subject: Re: [PATCH] Documentation: Improve crash_kexec_post_notifiers
 description

"Guilherme G. Piccoli" <gpiccoli@...lia.com> writes:
> Be more clear about the downsides, the upsides (yes, there are some!)
> and about code that unconditionally sets that.
>
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@...lia.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index efc52ddc6864..cb25dc5cbe9a 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -913,12 +913,16 @@
>  			the parameter has no effect.
>  
>  	crash_kexec_post_notifiers
> -			Run kdump after running panic-notifiers and dumping
> -			kmsg. This only for the users who doubt kdump always
> -			succeeds in any situation.
> -			Note that this also increases risks of kdump failure,
> -			because some panic notifiers can make the crashed
> -			kernel more unstable.
> +			Only jump to kdump kernel after running the panic
> +			notifiers and dumping kmsg. This option increases the
> +			risks of a kdump failure, since some panic notifiers
> +			can make the crashed kernel more unstable. As a bright
> +			side, it might allow to collect more data on dmesg like
> +			stack traces from other CPUs or extra data dumped by
> +			panic_print. This is usually only for users who doubt
> +			kdump will succeed every time.

This is definitely clearer and an improvement! But I didn't (and still
don't) love the phrase "users who doubt kdump will succeed" because I
think that implies user error or silly beliefs.

What if these two sentences read something like:

In configurations where kdump may not be reliable, running the panic
notifiers can allow collecting more data on dmesg, like stack traces
from other CPUS or extra data dumped by panic_print.

> Notice that some code
> +			enables this option unconditionally, like Hyper-V,
> +			PowerPC (fadump) and AMD SEV.

Yes, great addition.

With or without my suggestions it's an improvement, so:

Reviewed-by: Stephen Brennan <stephen.s.brennan@...cle.com>