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

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Message-ID: <alpine.LNX.2.00.1602160938310.17594@pobox.suse.cz>
Date:	Tue, 16 Feb 2016 09:41:26 +0100 (CET)
From:	Miroslav Benes <mbenes@...e.cz>
To:	Jessica Yu <jeyu@...hat.com>
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

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.

Cheers,
Miroslav