David Laight reports that sometimes reads on a serial port will

attempt to block, and hence return EAGAIN/EWOULDBLOCK, in spite of
the port having been reported readable by select(2). Don't treat
those errors as fatal.

[originally from svn r9020]

unix/uxser.c

@@ -342,6 +342,14 @@ static int serial_select_result(int fd, int event)
 	     */
 	    finished = TRUE;
 	} else if (ret < 0) {
+#ifdef EAGAIN
+	    if (errno == EAGAIN)
+		return 1;	       /* spurious */
+#endif
+#ifdef EWOULDBLOCK
+	    if (errno == EWOULDBLOCK)
+		return 1;	       /* spurious */
+#endif
 	    perror("read serial port");
 	    exit(1);
 	} else if (ret > 0) {