linux-kernel - Re: [PATCH v5] ftrace/module: remove ftrace module notifier

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Message-ID: <alpine.LNX.2.00.1602172133240.22700@cbobk.fhfr.pm>
Date:	Wed, 17 Feb 2016 21:35:29 +0100 (CET)
From:	Jiri Kosina <jikos@...nel.org>
To:	Jessica Yu <jeyu@...hat.com>, Steven Rostedt <rostedt@...dmis.org>
cc:	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>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Ingo Molnar <mingo@...hat.com>, live-patching@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] ftrace/module: remove ftrace module notifier

On Tue, 16 Feb 2016, Jessica Yu wrote:

> Remove the ftrace module notifier in favor of directly calling
> ftrace_module_enable() and ftrace_release_mod() in the module loader.
> Hard-coding the function calls directly in the module loader removes
> dependence on the module notifier call chain and provides better
> visibility and control over what gets called when, which is important
> to kernel utilities such as livepatch.
> 
> 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. This patch removes dependence on the module notifier call
> chain in favor of hard coding the corresponding function calls in the
> module loader. This ensures that ftrace and livepatch code get called in
> the correct order on patch module load and unload.
> 
> Fixes: 5156dca34a3e ("ftrace: Fix the race between ftrace and insmod")
> Signed-off-by: Jessica Yu <jeyu@...hat.com>
> Reviewed-by: Steven Rostedt <rostedt@...dmis.org>

Steven, I am going to assume that your Reviewed-by: still holds for the 
patch even though it has been removed from the 4-patch series; if you 
don't agree, please speak up. Otherwise, I am going to apply it and push 
it to Linus for -rc5 still (as it fixes our regression).

Thanks,

-- 
Jiri Kosina
SUSE Labs