linux-kernel - Re: [PATCH V2] Documentation: Improve crash_kexec_post

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Message-ID: <d954da78-87cf-d7d9-a620-0c2fae5dd242@igalia.com>
Date: Wed, 11 Sep 2024 17:09:11 +0200
From: "Guilherme G. Piccoli" <gpiccoli@...lia.com>
To: Baoquan He <bhe@...hat.com>
Cc: kexec@...ts.infradead.org, linux-doc@...r.kernel.org, vgoyal@...hat.com,
 dyoung@...hat.com, corbet@....net, linux-kernel@...r.kernel.org,
 linux-debuggers@...r.kernel.org, stephen.s.brennan@...cle.com,
 kernel@...ccoli.net, kernel-dev@...lia.com
Subject: Re: [PATCH V2] Documentation: Improve crash_kexec_post_notifiers
 description

On 02/09/2024 05:05, Baoquan He wrote:
> On 08/30/24 at 03:21pm, Guilherme G. Piccoli wrote:
>> Be more clear about the downsides, the upsides (yes, there are some!)
>> and about code that unconditionally sets that.
>>
>> Reviewed-by: Stephen Brennan <stephen.s.brennan@...cle.com>
>> Signed-off-by: Guilherme G. Piccoli <gpiccoli@...lia.com>
>>
>> ---
>>
>> V2: Some wording improvements from Stephen, thanks!
>> Also added his review tag.
>>
>> V1 link: https://lore.kernel.org/r/20240830140401.458542-1-gpiccoli@igalia.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..351730108c58 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. In the
>> +			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.
>                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> I know Hyper-V enable panic-notifiers by default, but don't remember how
> PowerPC and AMD SEC behave in this aspect. While at it, can you add a
> little more words to state them in log so that people can learn it?
> Thanks.
> 
Hi Baoquan, tnx for the suggestion! You mean mention that in the commit
message? If so, I can certainly do - will sent a new version soon(tm)
and include it =)

Cheers,


Guilherme