+ /* agg_instance_list_head only holds data, after the "write" callback has
+ * been called with a matching value list at least once. So on startup,
+ * there's a race between the aggregations read() and write() callback. If
+ * the read() callback is called first, agg_instance_list_head is NULL and
+ * "success" may be zero. This is expected and should not result in an error.
+ * Therefore we need to handle this case separately. */
+ if (agg_instance_list_head == NULL)
+ {
+ pthread_mutex_unlock (&agg_instance_list_lock);
+ return (0);
+ }
+