linux-kernel - Re: [PATCH 0/2] kmsg_dump: adding to reboot, halt, poweroff and emergency

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Message-Id: <20101117124518.6a0dd569.akpm@linux-foundation.org>
Date:	Wed, 17 Nov 2010 12:45:18 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Seiji Aguchi <seiji.aguchi@....com>
Cc:	"Artem.Bityutskiy@...ia.com" <Artem.Bityutskiy@...ia.com>,
	ext KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"simon.kagstrom@...insight.net" <simon.kagstrom@...insight.net>,
	"David.Woodhouse@...el.com" <David.Woodhouse@...el.com>,
	"anders.grafstrom@...insight.net" <anders.grafstrom@...insight.net>,
	"jason.wessel@...driver.com" <jason.wessel@...driver.com>,
	"jslaby@...e.cz" <jslaby@...e.cz>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"eparis@...hat.com" <eparis@...hat.com>, "hch@....de" <hch@....de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kyungmin.park@...sung.com" <kyungmin.park@...sung.com>,
	"marco.stornelli@...il.com" <marco.stornelli@...il.com>,
	"namhyung@...il.com" <namhyung@...il.com>,
	Aaron Durbin <adurbin@...gle.com>,
	"randy.dunlap@...cle.com" <randy.dunlap@...cle.com>,
	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Satoru Moriya <satoru.moriya@....com>
Subject: Re: [PATCH 0/2] kmsg_dump: adding to reboot, halt, poweroff and
 emergency_restart path

On Wed, 17 Nov 2010 09:58:18 -0500
Seiji Aguchi <seiji.aguchi@....com> wrote:

> Hi,
> 
> This series aims to develop logging facility for enterprise use.
> 
> It is important to save kernel messages reliably on enterprise system 
> because they are helpful for diagnosing system.
> 
> This series add kmsg_dump() to the paths loosing kernel messages.
> The use case is the following.
> 
> [Use case of reboot/poweroff/halt/emergency_restart]
> 
>  My company has often experienced the followings in our support service.
>  - Customer's system suddenly reboots.
>  - Customers ask us to investigate the reason of the reboot.
> 
>  We recognize the fact itself because boot messages remain in /var/log/messages.
>  However, we can't investigate the reason why the system rebooted,  because the last messages don't remain.
>  And off course we can't explain the reason.
>  
>  
>  We can solve above problem with this patch as follows.
>  Case1: reboot with command 
>    - We can see "Restarting system with command:" or ""Restarting system.".
> 
>  Case2: halt with command
>    - We can see "System halted.".
> 
>  Case3: poweroff with command
>    - We can see " Power down.".
> 
>  Case4: emergency_restart with sysrq.
>    - We can see "Sysrq:" outputted in __handle_sysrq().
> 
>  Case5: emergency_restart with softdog.
>    - We can see "Initiating system reboot" in watchdog_fire().
> 
>  So, we can distinguish the reason of reboot, poweroff, halt and emergency_restart.
> 
>  If customer executed reboot command, you may think the customer should know the fact.
>  However, they often claim they don't execute the command when they rebooted system by mistake.
> 
>  No evidential message remain on current Linux kernel, so we can't show the proof to the customer.
>  This patch improves this situation.
> 
> 
> The first patch alters mtdoops and ramoops to perform their actions only for KMSG_DUMP_PANIC,
> KMSG_DUMP_OOPS and KMSG_DUMP_KEXEC because they would like to log crashes only.
> 
> The latter patch adds kmsg_dump() to reboot, halt, poweroff and emergency_restart path.

Damn, that's a good changelog.  We can actually understand why you
wrote the patch, and see what its value is!

One thing: please don't send multiple patches with the same title. 
See Documentation/SubmittingPatches section 15.  I renamed these two
patches to

kmsg_dump: constrain mtdoops and ramoops to perform their actions only for KMSG_DUMP_PANIC

and

kmsg_dump: add kmsg_dump() calls to the reboot, halt, poweroff and emergency_restart paths

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