+extern int RTS_VAR(context_switch);
+extern rtsBool RTS_VAR(interrupted);
+
+/*
+ * flag that tracks whether we have done any execution in this time slice.
+ */
+#define ACTIVITY_YES 0 /* there has been activity in the current slice */
+#define ACTIVITY_MAYBE_NO 1 /* no activity in the current slice */
+#define ACTIVITY_INACTIVE 2 /* a complete slice has passed with no activity */
+#define ACTIVITY_DONE_GC 3 /* like 2, but we've done a GC too */
+extern nat recent_activity;