linux-kernel - Re: [PATCH] mtd: mtdoops: mtdoops works with kexec correctly

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Message-ID: <20091221153341.2bece1d3@marrow.netinsight.se>
Date:	Mon, 21 Dec 2009 15:33:41 +0100
From:	Simon Kagstrom <simon.kagstrom@...insight.net>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Anders Grafstrom <anders.grafstrom@...insight.net>,
	Artem Bityutskiy <Artem.Bityutskiy@...ia.com>,
	David Woodhouse <David.Woodhouse@...el.com>,
	kosaki.motohiro@...fujitsu.com, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mtd: mtdoops: mtdoops works with kexec correctly

On Mon, 21 Dec 2009 19:20:35 +0900 (JST)
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:

> commit 2e386e4ba(mtdoops: refactor as a kmsg_dumper) is very good patch.
> but unfortunately it doesn't works with kexec and few embedded user need
> to use kexec. there is no reason to don't implement it. it isn't so
> hard.
> 
> FAQ
> ---
>  Q. Why KMSG_DUMP_OOPS is insufficient?
>  A. Because crash_kexec() is called before KMSG_DUMP_OOPS if
>     panic_on_oops==1.
> 
>  Q. Why do you move KMSG_DUMP_PANIC call place?
>  A. Otherwise kmsg_dump() is called twice if kexec enabled.
>     it's annoy.

I think it would be better to describe these comments in text instead
of as FAQs. Because of the --- it's also removed from the git log.
Maybe something like

	kmsg_dump: Dump on crash_kexec as well

	crash_kexec gets called before kmsg_dump(KMSG_DUMP_OOPS) if
	panic_on_oops is set, so the kernel log buffer is not stored
	for this case.

	This patch adds a KMSG_DUMP_KEXEC dump type which gets called
	when crash_kexec() is invoked. To avoid getting double dumps,
	the old KMSG_DUMP_PANIC is moved below crash_kexec(). The
	mtdoops driver is modified to handle KMSG_DUMP_KEXEC in the
	same way as a panic.


Other than that, it looks fine to me. I've done basic testing against
2.6.33-rc1, but unfortunately without kexec support.

Acked-by: Simon Kagstrom <simon.kagstrom@...insight.net>

// Simon

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