- * The pre_select function gets called from the driving application
- * before entering its select loop. The receiver may use this hook to
- * add any file descriptors to the sets of file descriptors given by \a
- * s.
+ * If this is not NULL, the function is called in each iteration of the
+ * scheduler's select loop. The receiver may define it to add file
+ * descriptors to the file descriptor sets given by s. Those will be
+ * monitored in the subsequent call to select(2). The function may also
+ * lower the timeout value of s to make select(2) return earlier if no
+ * file descriptors are ready for I/O.