Char: n_hdlc, allow RESTARTSYS retval of tty write

Acked-by: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/n_hdlc.c

@@ -401,6 +401,11 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
 		tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
 		actual = tty->driver->write(tty, tbuf->buf, tbuf->count);
 
+		/* rollback was possible and has been done */
+		if (actual == -ERESTARTSYS) {
+			n_hdlc->tbuf = tbuf;
+			break;
+		}
 		/* if transmit error, throw frame away by */
 		/* pretending it was accepted by driver */
 		if (actual < 0)