linux-kernel - Re: livepatch/module: remove livepatch module notifier

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Date:	Mon, 29 Feb 2016 22:00:34 -0500
From:	Jessica Yu <jeyu@...hat.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Jiri Kosina <jikos@...nel.org>,
	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: livepatch/module: remove livepatch module notifier

+++ Rusty Russell [29/02/16 11:00 +1030]:
>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. No worries, we got the regression out of the way already. :-)

Jiri, I'll resend the remaining 3 patches in the series separately,
since we've merged the ftrace patch already.

Jessica