From: Jiri Slaby <jirislaby@gmail.com>

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

 drivers/char/n_hdlc.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletion(-)

diff -puN drivers/char/n_hdlc.c~char-n_hdlc-allow-restartsys-retval-of-tty-write drivers/char/n_hdlc.c
--- a/drivers/char/n_hdlc.c~char-n_hdlc-allow-restartsys-retval-of-tty-write
+++ a/drivers/char/n_hdlc.c
@@ -400,7 +400,12 @@ static void n_hdlc_send_frames(struct n_
 		/* Send the next block of data to device */
 		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)
_