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

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Message-ID: <20140506082604.31928cb9@gandalf.local.home>
Date:	Tue, 6 May 2014 08:26:04 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
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

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.

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

-- Steve
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