linux-kernel - Re: [RFC PATCH 0/2] kpatch: dynamic kernel patching

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Message-ID: <53696327.9010806@hitachi.com>
Date:	Wed, 07 May 2014 07:33:11 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Seth Jennings <sjenning@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, Jiri Slaby <jslaby@...e.cz>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH 0/2] kpatch: dynamic kernel patching

(2014/05/06 21:26), Steven Rostedt wrote:
> On Tue, 06 May 2014 20:45:50 +0900
> Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:
> 
> 
>> However, I also think if users can accept such freezing wait-time,
>> it means they can also accept kexec based "checkpoint-restart" patching.
>> So, I think the final goal of the kpatch will be live patching without
>> stopping the machine. I'm discussing the issue on github #138, but that is
>> off-topic. :)
>>
> 
> I agree with Ingo too. Being conservative at first is the right
> approach here. We should start out with a stop_machine making sure that
> everything is sane before we continue. Sure, that's not much different
> than a kexec, but lets take things one step at a time.

Agreed. that is a correct way to move things forward.
Anyway, my stop_machine-less approach still has many implementation
issues. It should be solved in upstream, not out-of-tree. So, this
topic is off-topic at this stage. :) We need to focus on how to
merge live-patch into upstream kernel.

> ftrace did the stop_machine (and still does for some archs), and slowly
> moved to a more efficient method. kpatch/kgraft should follow suit.

Sure, that's a best story of how things should be evolved on the kernel :)

Thank you,

-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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