From: Gleb Natapov <gleb@redhat.com>
Date: Tue, 18 Oct 2011 17:55:51 +0000 (+0200)
Subject: jump_label: jump_label_inc may return before the code is patched
X-Git-Tag: v3.1.5~18
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cf246087a19a4958fba3123d21f1359b6177ddb5;p=thirdparty%2Fkernel%2Fstable.git

jump_label: jump_label_inc may return before the code is patched

commit bbbf7af4bf8fc69bc751818cf30521080fa47dcb upstream.

If cpu A calls jump_label_inc() just after atomic_add_return() is
called by cpu B, atomic_inc_not_zero() will return value greater then
zero and jump_label_inc() will return to a caller before jump_label_update()
finishes its job on cpu B.

Link: http://lkml.kernel.org/r/20111018175551.GH17571@redhat.com

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index a8ce45097f3d2..e6f1f24ad5778 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -66,8 +66,9 @@ void jump_label_inc(struct jump_label_key *key)
 		return;
 
 	jump_label_lock();
-	if (atomic_add_return(1, &key->enabled) == 1)
+	if (atomic_read(&key->enabled) == 0)
 		jump_label_update(key, JUMP_LABEL_ENABLE);
+	atomic_inc(&key->enabled);
 	jump_label_unlock();
 }