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

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Date:	Sun, 14 Feb 2016 23:59:00 +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, Jiri Kosina 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.

Rusty, friendly ping? :)

I know that this is quite tight timing, but I'd like to have the 4.4 
regression fixed, and we are quite late in the -rc phase already.

Thanks in advance,

-- 
Jiri Kosina
SUSE Labs