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

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Date:	Tue, 16 Feb 2016 14:51:58 -0500
From:	Jessica Yu <jeyu@...hat.com>
To:	Miroslav Benes <mbenes@...e.cz>
Cc:	Jiri Kosina <jikos@...nel.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Seth Jennings <sjenning@...hat.com>,
	Vojtech Pavlik <vojtech@...e.com>,
	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

+++ Miroslav Benes [16/02/16 09:41 +0100]:
>On Mon, 15 Feb 2016, Jessica Yu wrote:
>
>> +++ Jiri Kosina [16/02/16 00:42 +0100]:
>> > On Mon, 15 Feb 2016, Josh Poimboeuf wrote:
>> >
>> > > So I think the commit causing the regression is 5156dca34a3e, which
>> > > occurred in the 4.5 cycle, *not* in 4.4.
>> >
>> > Agreed, by "4.4 regresion" I mean "regression compared to 4.4"; i.e.
>> > regression that will become real issue once 4.5 is released.
>> >
>> > > Also it's my understanding that only the third patch ("remove ftrace
>> > > module notifier") is needed to fix the regression, and the other patches
>> > > are just general improvements.  So if needed I think we can just rebase
>> > > that patch (which already has Rusty's ack I believe) and send it to
>> > > Linus now.
>> >
>> > 3/4 and 4/4 are be sufficient, yes (although I'd like to have this
>> > confimed by Jessica, as she apparently already has a reliable testcase).
>>
>> Yes, so Josh is right; technically only patch 3/4 "ftrace/module:
>> remove ftrace module notifier" is sufficient enough to fix the bug,
>> and patch 4/4 is just a natural extension of that change. Since I'm
>> going to be sending out another patchset anyway without the module.c
>> cleanups, I'll just keep them together.
>
>Yes, 3/4 should be sufficient to fix the bug. However if you take 4/4 too,
>you need 1/4 as well. Otherwise we would introduce a bug in error handling
>as Petr pointed out.
>

Hm. I am just realizing that patch 4/4 will still need new ACK's for
the error handling portion. What I'll do is, after testing, send out
patch 3/4 ("ftrace/module: remove ftrace module notifier") as a
standalone patch to be merged immediately, since it fixes an actual
bug. The rest of this patchset will follow separately and can be
reviewed at its own pace.

Jessica