From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: Seth Jennings <sjenning@redhat.com>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
Steven Rostedt <rostedt@goodmis.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@redhat.com>, Jiri Slaby <jslaby@suse.cz>,
linux-kernel@vger.kernel.org,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [RFC PATCH 0/2] kpatch: dynamic kernel patching
Date: Mon, 5 May 2014 08:26:38 -0500 [thread overview]
Message-ID: <20140505132638.GA14432@treble.redhat.com> (raw)
In-Reply-To: <20140505085537.GA32196@gmail.com>
On Mon, May 05, 2014 at 10:55:37AM +0200, Ingo Molnar wrote:
>
> * Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
> > [...]
> >
> > kpatch checks the backtraces of all tasks in stop_machine() to
> > ensure that no instances of the old function are running when the
> > new function is applied. I think the biggest downside of this
> > approach is that stop_machine() has to idle all other CPUs during
> > the patching process, so it inserts a small amount of latency (a few
> > ms on an idle system).
>
> When live patching the kernel, how about achieving an even 'cleaner'
> state for all tasks in the system: to freeze all tasks, as the suspend
> and hibernation code (and kexec) does, via freeze_processes()?
>
> That means no tasks in the system have any real kernel execution
> state, and there's also no problem with long-sleeping tasks, as
> freeze_processes() is supposed to be fast as well.
>
> I.e. go for the most conservative live patching state first, and relax
> it only once the initial model is upstream and is working robustly.
I had considered doing this before, but the problem I found is that many
kernel threads are unfreezable. So we wouldn't be able to check whether
its safe to replace any functions in use by those kernel threads.
--
Josh
next prev parent reply other threads:[~2014-05-05 13:26 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-01 15:52 [RFC PATCH 0/2] kpatch: dynamic kernel patching Josh Poimboeuf
2014-05-01 15:52 ` [RFC PATCH 1/2] kpatch: add TAINT_KPATCH flag Josh Poimboeuf
2014-05-01 15:52 ` [RFC PATCH 2/2] kpatch: add kpatch core module Josh Poimboeuf
2014-05-01 20:45 ` [RFC PATCH 0/2] kpatch: dynamic kernel patching Andi Kleen
2014-05-01 21:01 ` Josh Poimboeuf
2014-05-01 21:06 ` Andi Kleen
2014-05-01 21:27 ` Josh Poimboeuf
2014-05-01 21:39 ` Josh Poimboeuf
2014-05-02 1:30 ` Masami Hiramatsu
2014-05-02 8:37 ` Jiri Kosina
2014-05-02 13:29 ` Josh Poimboeuf
2014-05-02 13:10 ` Jiri Kosina
2014-05-02 13:37 ` Josh Poimboeuf
2014-05-05 23:34 ` David Lang
2014-05-05 23:52 ` Jiri Kosina
2014-05-06 1:59 ` David Lang
2014-05-06 12:17 ` Josh Poimboeuf
2014-05-06 7:32 ` Ingo Molnar
2014-05-06 8:03 ` Jiri Kosina
2014-05-06 12:23 ` Josh Poimboeuf
2014-05-07 12:19 ` Ingo Molnar
2014-05-09 1:46 ` David Lang
2014-05-09 2:45 ` Steven Rostedt
2014-05-09 4:07 ` Masami Hiramatsu
2014-05-05 8:55 ` Ingo Molnar
2014-05-05 13:26 ` Josh Poimboeuf [this message]
2014-05-05 14:10 ` Frederic Weisbecker
2014-05-05 18:43 ` Ingo Molnar
2014-05-05 21:49 ` Frederic Weisbecker
2014-05-06 12:12 ` Josh Poimboeuf
2014-05-06 12:33 ` Steven Rostedt
2014-05-06 22:49 ` Masami Hiramatsu
2014-05-06 14:05 ` Frederic Weisbecker
2014-05-06 14:50 ` Josh Poimboeuf
2014-05-07 12:24 ` Ingo Molnar
2014-05-07 15:41 ` Josh Poimboeuf
2014-05-07 15:57 ` Ingo Molnar
2014-05-07 16:43 ` Josh Poimboeuf
2014-05-07 22:56 ` David Lang
2014-05-08 6:12 ` Ingo Molnar
2014-05-08 6:50 ` David Lang
2014-05-08 7:08 ` Ingo Molnar
2014-05-08 7:29 ` Masami Hiramatsu
2014-05-08 12:48 ` Josh Poimboeuf
2014-05-09 6:21 ` Masami Hiramatsu
2014-06-14 20:31 ` Pavel Machek
2014-06-15 6:57 ` Ingo Molnar
2014-05-06 11:45 ` Masami Hiramatsu
2014-05-06 12:26 ` Steven Rostedt
2014-05-06 22:33 ` Masami Hiramatsu
2014-05-16 16:27 ` Jiri Kosina
2014-05-16 17:14 ` Josh Poimboeuf
2014-05-20 9:37 ` Jiri Kosina
2014-05-20 12:59 ` Josh Poimboeuf
2014-05-16 18:09 ` Masami Hiramatsu
2014-05-17 22:46 ` Vojtech Pavlik
2014-05-16 18:55 ` Steven Rostedt
2014-05-16 22:32 ` Jiri Kosina
2014-05-17 0:27 ` Steven Rostedt
2014-05-17 7:10 ` Jiri Kosina
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