linux-kernel - [PATCH 2/2] ftrace: Adjust priority of ftrace module notifier

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Date:	Fri, 29 Jan 2016 01:43:47 -0500
From:	Jessica Yu <jeyu@...hat.com>
To:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Seth Jennings <sjenning@...hat.com>,
	Jiri Kosina <jikos@...nel.org>,
	Vojtech Pavlik <vojtech@...e.com>,
	Miroslav Benes <mbenes@...e.cz>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>
Cc:	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jessica Yu <jeyu@...hat.com>
Subject: [PATCH 2/2] ftrace: Adjust priority of ftrace module notifier

Adjust the priority of the ftrace module notifier such that it will run
before the livepatch coming module notifier but after the livepatch going
module modifier.

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.

Signed-off-by: Jessica Yu <jeyu@...hat.com>
---
 kernel/trace/ftrace.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index eca592f..bdd7bfc 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5067,7 +5067,12 @@ static int ftrace_module_notify(struct notifier_block *self,
 
 struct notifier_block ftrace_module_nb = {
 	.notifier_call = ftrace_module_notify,
-	.priority = INT_MIN,	/* Run after anything that can remove kprobes */
+	/*
+	 * Run after anything that can remove kprobes and
+	 * after livepatch's going notifier, but run before
+	 * livepatch's coming notifier.
+	 */
+	.priority = INT_MIN+1,
 };
 
 void __init ftrace_init(void)
-- 
2.4.3