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

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Message-ID: <m1pr7hf93s.fsf@fess.ebiederm.org>
Date:	Tue, 17 Nov 2009 07:45:43 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	dedekind1@...il.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

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.

Eric

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