--- x/kernel/rcu/tree.c
+++ y/kernel/rcu/tree.c
@@ -2957,7 +2957,8 @@ krc_this_cpu_lock(unsigned long *flags)
 
 	local_irq_save(*flags);	// For safely calling this_cpu_ptr().
 	krcp = this_cpu_ptr(&krc);
-	raw_spin_lock(&krcp->lock);
+	while (!raw_spin_trylock(&krcp->lock))
+		;
 
 	return krcp;
 }