linux-kernel - Re: [PATCH, RFC] panic-note: Annotation from user space for panics

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Message-Id: <1258532794.27437.124.camel@localhost>
Date:	Wed, 18 Nov 2009 10:26:34 +0200
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Marco Stornelli <marco.stornelli@...il.com>,
	Simon Kagstrom <simon.kagstrom@...insight.net>,
	David VomLehn <dvomlehn@...co.com>,
	linux-embedded@...r.kernel.org, akpm@...ux-foundation.org,
	dwm2@...radead.org, linux-kernel@...r.kernel.org, mpm@...enic.com,
	paul.gortmaker@...driver.com
Subject: Re: [PATCH, RFC] panic-note: Annotation from user space for panics

On Tue, 2009-11-17 at 07:45 -0800, Eric W. Biederman wrote:
> Artem Bityutskiy <dedekind1@...il.com> writes:
> 
> > On Tue, 2009-11-17 at 13:45 +0100, Marco Stornelli wrote:
> >> 2009/11/17 Artem Bityutskiy <dedekind1@...il.com>:
> >> > Take a look at my mails where I describe different complications we have
> >> > in our system. We really want to have an OOPS/panic + our environment
> >> > stuff to go together, at once. This makes things so much simpler.
> >> >
> >> > Really, what is the problem providing this trivial panic-note
> >> > capability, where user-space can give the kernel a small buffer, and ask
> >> > the kernel to print this buffer at the oops/panic time. Very simple and
> >> > elegant, and just solves the problem.
> >> >
> >> > Why perversions with time-stamps, separate storages are needed?
> >> >
> >> > IOW, you suggest a complicated approach, and demand explaining why we do
> >> > not go for it. Simply because it is unnecessarily complex.
> >> 
> >> I don't think it's a complicated approach we are talking of a system
> >> log like syslog with a temporal information, nothing more.
> >
> > We need to store this information of NAND flash. Implementing logs on
> > NAND flash is about handling bad blocks, choosing format of records, and
> > may be even handling wear-levelling. This is not that simple.
> >
> > And then I have match oops to the userspace environment prints, using I
> > guess timestamps, which is also about complications in userspace.
> >
> >> > This patch solves the problem gracefully, and I'd rather demand you to point what
> >> > is the technical problem with the patches.
> >> >
> >> 
> >> Simply because I think that we should avoid to include in the kernel
> >> things we can do in a simply way at user space level.
> >
> > If it is much easier to have in the kernel, then this argument does not
> > work, IMHO.
> >
> >>  I think this
> >> patch is well done but it's one of the patches that are solutions "for
> >> embedded only", but it's only my opinion.
> >
> > Also IMHO, but having embedded-only things is not bad at all.
> 
> Why not use the kdump hook?  If you handle a kernel panic that way
> you get enhanced reliability and full user space support.  All in a hook
> that is already present and already works.

For some reasons kdump does not work on ARM out of the box. We need to
investigate this.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)

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