diff --git a/arch/sim/src/up_simsmp.c b/arch/sim/src/up_simsmp.c
index c54144678d5..306cab05efe 100644
--- a/arch/sim/src/up_simsmp.c
+++ b/arch/sim/src/up_simsmp.c
@@ -251,3 +251,52 @@ errout_with_mutex:
   (void)pthread_mutex_destroy(&cpuinfo.mutex);
   return ret;
 }
+
+/****************************************************************************
+ * Name: up_cpustop
+ *
+ * Description:
+ *   Save the state of the current task at the head of the
+ *   g_assignedtasks[cpu] task list and then stop the CPU.
+ *
+ *   This function is called by the OS when the logic executing on one CPU
+ *   needs to modify the state of the g_assignedtasks[cpu] list for another
+ *   CPU.
+ *
+ * Input Parameters:
+ *   cpu - The index of the CPU to be stopped/
+ *
+ * Returned Value:
+ *   Zero on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int up_cpustop(int cpu)
+{
+#warning Missing SMP logic
+  return 0;
+}
+
+/****************************************************************************
+ * Name: up_cpurestart
+ *
+ * Description:
+ *   Restart the cpu, restoring the state of the task at the head of the
+ *   g_assignedtasks[cpu] list.
+ *
+ *   This function is called after up_cpustop in order resume operation of
+ *   the CPU after modifying its g_assignedtasks[cpu] list.
+ *
+ * Input Parameters:
+ *   cpu - The index of the CPU being re-started.
+ *
+ * Returned Value:
+ *   Zero on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int up_cpurestart(int cpu)
+{
+#warning Missing SMP logic
+  return 0;
+}