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

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Date:	Mon, 29 Feb 2016 11:00:09 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Jiri Kosina <jikos@...nel.org>
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

Jiri Kosina <jikos@...nel.org> writes:
> 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.

Sorry Jiri, I am on paternity leave.  Am happy with all these patches;
please use your best judgement:

Acked-by: Rusty Russell <rusty@...tcorp.com.au>

Thanks,
Rusty.