--- x/kernel/rcu/tree.c +++ y/kernel/rcu/tree.c @@ -3071,6 +3071,7 @@ __call_rcu_common(struct rcu_head *head, /* Misaligned rcu_head! */ WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1)); + BUG_ON(!func); if (debug_rcu_head_queue(head)) { /*