+ /* Due to a glib bug, removing the last reference to a source
+ * inside a finalize callback causes recursive locking (and a
+ * deadlock). This is not a problem inside other callbacks,
+ * including dispatch callbacks, so we call io_remove_watch_poll
+ * to remove this source. At this point, iwp->src must
+ * be NULL, or we would leak it.
+ *
+ * This would be solved much more elegantly by child sources,
+ * but we support older glib versions that do not have them.
+ */