linux-kernel - Re: [PATCH 1/3] panic: Disable crash_kexec_post

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Message-ID: <55A46C3D.7000208@hitachi.com>
Date:	Tue, 14 Jul 2015 10:56:13 +0900
From:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
To:	dwalker@...o99.com, "Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Vivek Goyal <vgoyal@...hat.com>, linux-mips@...ux-mips.org,
	Baoquan He <bhe@...hat.com>, linux-sh@...r.kernel.org,
	linux-s390@...r.kernel.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linuxppc-dev@...ts.ozlabs.org, linux-metag@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/3] panic: Disable crash_kexec_post_notifiers if kdump
 is not available

Hello Eric and Daniel,

(2015/07/14 5:26), dwalker@...o99.com wrote:
> On Fri, Jul 10, 2015 at 08:41:28AM -0500, Eric W. Biederman wrote:
>> Hidehiro Kawai <hidehiro.kawai.ez@...achi.com> writes:
>>
>>> You can call panic notifiers and kmsg dumpers before kdump by
>>> specifying "crash_kexec_post_notifiers" as a boot parameter.
>>> However, it doesn't make sense if kdump is not available.  In that
>>> case, disable "crash_kexec_post_notifiers" boot parameter so that
>>> you can't change the value of the parameter.
>>
>> Nacked-by: "Eric W. Biederman" <ebiederm@...ssion.com>
>>
>> You are confusing kexec on panic and CONFIG_CRASH_DUMP
>> which is about the tools for reading the state of the previous kernel.

You are right.  I mistook the meaning of CONFIG_CRASH_DUMP.

> I think it would make sense if he just replaced "kdump" with "kexec".

If a user specified crash_kexec_post_notifiers option with kexec
being totally disabled, it just disables notifier and kmsg dumper calls
(please see PATCH 3/3). So as Daniel said, I also think it makes sense
to hide crash_kexec_post_notifiers option if kexec is disabled.

Regards,

-- 
Hidehiro Kawai
Hitachi, Ltd. Research & Development Group


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