diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 2c7787b997e9..46c8ccd9f2a3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3991,7 +3991,7 @@ struct workqueue_struct *rcu_par_gp_wq;
 
 void __init rcu_init(void)
 {
-	int cpu;
+	int cpu = smp_processor_id();
 
 	rcu_early_boot_tests();
 
@@ -4008,11 +4008,10 @@ void __init rcu_init(void)
 	 * or the scheduler are operational.
 	 */
 	pm_notifier(rcu_pm_notify, 0);
-	for_each_online_cpu(cpu) {
-		rcutree_prepare_cpu(cpu);
-		rcu_cpu_starting(cpu);
-		rcutree_online_cpu(cpu);
-	}
+	WARN_ON(num_online_cpus() > 1); // Only one CPU this early in boot.
+	rcutree_prepare_cpu(cpu);
+	rcu_cpu_starting(cpu);
+	rcutree_online_cpu(cpu);
 
 	/* Create workqueue for expedited GPs and for Tree SRCU. */
 	rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_POWER_EFFICIENT | WQ_MEM_RECLAIM, 0);