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

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Date:	Wed, 10 Feb 2016 10:13:12 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Jessica Yu <jeyu@...hat.com>, Josh Poimboeuf <jpoimboe@...hat.com>,
	Seth Jennings <sjenning@...hat.com>,
	Jiri Kosina <jikos@...nel.org>,
	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>
Cc:	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jessica Yu <jeyu@...hat.com>
Subject: Re: [PATCH v4 4/4] livepatch/module: remove livepatch module notifier

Jessica Yu <jeyu@...hat.com> writes:
> 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...

Sorry for being obtuse!
Rusty.