linux-kernel - Re: [PATCH] kernel/panic: Add "late_kdump" option for kdump in unstable condition

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Date:	Fri, 18 Apr 2014 12:09:22 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Satoru MORIYA <satoru.moriya.br@...achi.com>,
	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>,
	Takenori Nagano <t-nagano@...jp.nec.com>,
	Eric Biederman <ebiederm@...ssion.com>,
	Motohiro Kosaki <Motohiro.Kosaki@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] kernel/panic: Add "late_kdump" option for kdump in unstable
 condition

(2014/04/17 22:43), Vivek Goyal wrote:
> On Thu, Apr 17, 2014 at 10:59:14AM +0900, Masami Hiramatsu wrote:
> 
> [..]
>>>> @@ -112,9 +113,14 @@ void panic(const char *fmt, ...)
>>>>  	/*
>>>>  	 * If we have crashed and we have a crash kernel loaded let it handle
>>>>  	 * everything else.
>>>> -	 * Do we want to call this before we try to display a message?
>>>> +	 * If we want to call this after we try to display a message, pass
>>>> +	 * the "late_kdump" option to the kernel.
>>>>  	 */
>>>> -	crash_kexec(NULL);
>>>> +	if (!late_kdump)
>>>> +		crash_kexec(NULL);
>>>> +	else
>>>> +		pr_emerg("Warning: late_kdump option is set. Please DO NOT "
>>>> +			"report bugs about kdump failure with this option.\n");
>>>
>>> I think above message about DO NOT report bugs seems unnecessary. 
>>
>> OK, so I just notify the option is set as below.
>> "Warning: crash_kexec_post_notifiers is set.\n"
> 
> I would say for the time being don't put any extra message. User will
> think what this warning is supposed to mean. We can introduce one if
> we run into many issues.

Ah, I see.

> For the time being we can just look at kernel logs and look at command
> line options and see whether crash_kexec_post_notifiers was set or not.

Yeah, I know. However since the kernel command line is shown in very early
part of kernel logs, I worried about the case that it is pushed out from
kmsg buffer. And usually users will send a bug report with the very last
of the kernel logs because it becomes too long.

Thank you,

-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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