- * taken off the global childw queue iff this is the last child for
- * that parent. If there is no error detected in the callback, then
- * it should call adns__query_done if and only if there are no more
- * children (by checking parent->children.head). If an error is
- * detected in the callback it should call adns__query_fail and any
- * remaining children will automatically be cancelled.
+ * taken off the global childw queue.
+ *
+ * The callback should either call adns__query_done, if it is
+ * complete, or adns__query_fail, if an error has occurred, in which
+ * case the other children (if any) will be cancelled. If the parent
+ * has more unfinished children (or has just submitted more) then the
+ * callback may choose to wait for them - it must then put the parent
+ * back on the childw queue.