rcu: Fix RCU lockdep splat on freezer_fork path

Add an RCU read-side critical section to suppress this false positive. Located-by: Eric Paris <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> Acked-by: Li Zefan <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] LKML-Reference: <[email protected]> Signed-off-by: Ingo Molnar <[email protected]>
kishon · Apr 30, 2010 · 8b46f88 · 8b46f88
1 parent 8b08ca5
commit 8b46f88
Showing 1 changed file with 4 additions and 1 deletion.
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
@@ -205,9 +205,12 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
 	 * No lock is needed, since the task isn't on tasklist yet,
 	 * so it can't be moved to another cgroup, which means the
 	 * freezer won't be removed and will be valid during this
-	 * function call.
+	 * function call.  Nevertheless, apply RCU read-side critical
+	 * section to suppress RCU lockdep false positives.
 	 */
+	rcu_read_lock();
 	freezer = task_freezer(task);
+	rcu_read_unlock();
 
 	/*
 	 * The root cgroup is non-freezable, so we can skip the