linux-kernel - Re: [PATCH v4 4/4] livepatch/module: remove livepatch module notifier

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Message-ID: <alpine.LNX.2.00.1602101115420.22727@cbobk.fhfr.pm>
Date:	Wed, 10 Feb 2016 11:18:58 +0100 (CET)
From:	Jiri Kosina <jikos@...nel.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
cc:	Jessica Yu <jeyu@...hat.com>, Josh Poimboeuf <jpoimboe@...hat.com>,
	Seth Jennings <sjenning@...hat.com>,
	Vojtech Pavlik <vojtech@...e.com>,
	Miroslav Benes <mbenes@...e.cz>,
	Petr Mladek <pmladek@...e.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>, live-patching@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/4] livepatch/module: remove livepatch module
 notifier

On Wed, 10 Feb 2016, Rusty Russell wrote:

> > Remove the livepatch module notifier in favor of directly enabling and
> > disabling patches to modules in the module loader. Hard-coding the
> > function calls ensures that ftrace_module_enable() is run before
> > klp_module_coming() during module load, and that klp_module_going() is
> > run before ftrace_release_mod() during module unload. This way, ftrace
> > and livepatch code is run in the correct order during the module
> > load/unload sequence without dependence on the module notifier call chain.
> >
> > This fixes a notifier ordering issue in which the ftrace module notifier
> > (and hence ftrace_module_enable()) for coming modules was being called
> > after klp_module_notify(), which caused livepatch modules to initialize
> > incorrectly.
> 
> Without a Fixes: line, it's not absolutely clear whether this needs
> CC:stable, needs to go to Linus now, or can wait for the next merge
> window.
> 
> I *think* you want all four merged this merge window, and 3 and 4 are
> required to fix a regression introduced since 4.4...

Your understanding is correct; #3 and #4 are needed to fix a 4.4 
regression. It makes sense for the whole lot go to together, but for #1 
and #2 I absolutely need your Ack before I take it to my tree, as I don't 
want to be merging this behind your back.

Once you Ack #1 and #2, I plan to take this to Linus immediately so that 
we avoid doing these changes as very last minute.

Thanks!

-- 
Jiri Kosina
SUSE Labs