diff --git a/kernel/pid.c b/kernel/pid.c
index e432057..8cafe7e 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -418,7 +418,9 @@
  */
 struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
 {
-	rcu_lockdep_assert(rcu_read_lock_held());
+	rcu_lockdep_assert(rcu_read_lock_held(),
+			   "find_task_by_pid_ns() needs rcu_read_lock()"
+			   " protection");
 	return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
 }