Merge "n_tty: Fix unsafe update of available buffer space"

}

/**

 *	n_tty_set__room	-	receive space

 *	n_tty_set_room	-	receive space

 *	@tty: terminal

 *

 *	Called by the driver to find out how much data it is

 *	permitted to feed to the line discipline without any being lost

 *	and thus to manage flow control. Not serialized. Answers for the

 *	"instant".

 *	Sets tty->receive_room to reflect the currently available space

 *	in the input buffer, and re-schedules the flip buffer work if space

 *	just became available.

 *

 *	Locks: Concurrent update is protected with read_lock

 */

static void n_tty_set_room(struct tty_struct *tty)

	struct n_tty_data *ldata = tty->disc_data;

	int left;

	int old_left;

	unsigned long flags;

	raw_spin_lock_irqsave(&ldata->read_lock, flags);

	/* ldata->read_cnt is not read locked ? */

	if (I_PARMRK(tty)) {

		/* Multiply read_cnt by 3, since each byte might take up to

		 * three times as many spaces when PARMRK is set (depending on

	old_left = tty->receive_room;

	tty->receive_room = left;

	raw_spin_unlock_irqrestore(&ldata->read_lock, flags);

	/* Did this open up the receive buffer? We may need to flip */

	if (left && !old_left) {

		WARN_RATELIMIT(tty->port->itty == NULL,

				retval = -ERESTARTSYS;

				break;

			}

			/* FIXME: does n_tty_set_room need locking ? */

			n_tty_set_room(tty);

			timeout = schedule_timeout(timeout);

			continue;