Index: sys/kern/kern_cpuset.c
===================================================================
--- sys/kern/kern_cpuset.c
+++ sys/kern/kern_cpuset.c
@@ -160,8 +160,10 @@
 cpuset_getroot(struct cpuset *set)
 {
 
-	while ((set->cs_flags & CPU_SET_ROOT) == 0 && set->cs_parent != NULL)
-		set = set->cs_parent;
+	if (set->cs_parent != NULL)
+		do {
+			set = set->cs_parent;
+		} while ((set->cs_flags & CPU_SET_ROOT) == 0 && set->cs_parent != NULL);
 	return (set);
 }