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

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Message-Id: <20091222085508.1410.A69D9226@jp.fujitsu.com>
Date:	Tue, 22 Dec 2009 09:03:01 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Simon Kagstrom <simon.kagstrom@...insight.net>
Cc:	kosaki.motohiro@...fujitsu.com,
	Anders Grafstrom <anders.grafstrom@...insight.net>,
	Artem Bityutskiy <Artem.Bityutskiy@...ia.com>,
	David Woodhouse <David.Woodhouse@...el.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>

Thanks. Your description is obviously better.



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