+/**
+ * Unregister the fd from the fdset.
+ *
+ * If parameters are invalid, return directly -2.
+ * And check whether fd is busy, if yes, return -1.
+ * Otherwise, try to delete the fd from fdset and
+ * return true.
+ */
+int
+fdset_try_del(struct fdset *pfdset, int fd)
+{
+ int i;
+
+ if (pfdset == NULL || fd == -1)
+ return -2;
+
+ pthread_mutex_lock(&pfdset->fd_mutex);
+ i = fdset_find_fd(pfdset, fd);
+ if (i != -1 && pfdset->fd[i].busy) {
+ pthread_mutex_unlock(&pfdset->fd_mutex);
+ return -1;
+ }
+
+ if (i != -1) {
+ pfdset->fd[i].fd = -1;
+ pfdset->fd[i].rcb = pfdset->fd[i].wcb = NULL;
+ pfdset->fd[i].dat = NULL;
+ }
+
+ pthread_mutex_unlock(&pfdset->fd_mutex);
+ return 0;
+}