-#define preempt_disable() do { } while (0)
-#define preempt_enable_no_resched() do { } while (0)
-#define preempt_enable() do { } while (0)
+/*
+ * Even if we don't have any preemption, we need preempt disable/enable
+ * to be barriers, so that we don't have things like get_user/put_user
+ * that can cause faults and scheduling migrate into our preempt-protected
+ * region.
+ */
+#define preempt_disable() barrier()
+#define preempt_enable_no_resched() barrier()
+#define preempt_enable() barrier()