1 files changed, 51 insertions, 37 deletions

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 6c7fe90ad72d..4bf0fc0843d7 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -89,6 +89,7 @@ struct n_tty_data {
 	int read_head;
 	int read_tail;
 	int read_cnt;
+	int minimum_to_wake;
 
 	unsigned char *echo_buf;
 	unsigned int echo_pos;
@@ -114,22 +115,25 @@ static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
 }
 
 /**
- *	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".
+ *	Updates 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)
+static int 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
@@ -149,8 +153,15 @@ static void n_tty_set_room(struct tty_struct *tty)
 	old_left = tty->receive_room;
 	tty->receive_room = left;
 
+	raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
+
+	return left && !old_left;
+}
+
+static void n_tty_set_room(struct tty_struct *tty)
+{
 	/* Did this open up the receive buffer? We may need to flip */
-	if (left && !old_left) {
+	if (set_room(tty)) {
 		WARN_RATELIMIT(tty->port->itty == NULL,
 				"scheduling with invalid itty\n");
 		/* see if ldisc has been killed - if so, this means that
@@ -647,8 +658,7 @@ static void process_echoes(struct tty_struct *tty)
 			if (no_space_left)
 				break;
 		} else {
-			if (O_OPOST(tty) &&
-			    !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
+			if (O_OPOST(tty)) {
 				int retval = do_output_char(c, tty, space);
 				if (retval < 0)
 					break;
@@ -1454,9 +1464,9 @@ static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
 			tty->ops->flush_chars(tty);
 	}
 
-	n_tty_set_room(tty);
+	set_room(tty);
 
-	if ((!ldata->icanon && (ldata->read_cnt >= tty->minimum_to_wake)) ||
+	if ((!ldata->icanon && (ldata->read_cnt >= ldata->minimum_to_wake)) ||
 		L_EXTPROC(tty)) {
 		kill_fasync(&tty->fasync, SIGIO, POLL_IN);
 		if (waitqueue_active(&tty->read_wait))
@@ -1516,12 +1526,7 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
 		wake_up_interruptible(&tty->read_wait);
 
 	ldata->icanon = (L_ICANON(tty) != 0);
-	if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
-		ldata->raw = 1;
-		ldata->real_raw = 1;
-		n_tty_set_room(tty);
-		return;
-	}
+
 	if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
 	    I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
 	    I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
@@ -1642,7 +1647,7 @@ static int n_tty_open(struct tty_struct *tty)
 	tty->disc_data = ldata;
 	reset_buffer_flags(tty->disc_data);
 	ldata->column = 0;
-	tty->minimum_to_wake = 1;
+	ldata->minimum_to_wake = 1;
 	tty->closing = 0;
 	/* indicate buffer work may resume */
 	clear_bit(TTY_LDISC_HALTED, &tty->flags);
@@ -1806,21 +1811,17 @@ do_it_again:
 	minimum = time = 0;
 	timeout = MAX_SCHEDULE_TIMEOUT;
 	if (!ldata->icanon) {
-		time = (HZ / 10) * TIME_CHAR(tty);
 		minimum = MIN_CHAR(tty);
 		if (minimum) {
+			time = (HZ / 10) * TIME_CHAR(tty);
 			if (time)
-				tty->minimum_to_wake = 1;
+				ldata->minimum_to_wake = 1;
 			else if (!waitqueue_active(&tty->read_wait) ||
-				 (tty->minimum_to_wake > minimum))
-				tty->minimum_to_wake = minimum;
+				 (ldata->minimum_to_wake > minimum))
+				ldata->minimum_to_wake = minimum;
 		} else {
-			timeout = 0;
-			if (time) {
-				timeout = time;
-				time = 0;
-			}
-			tty->minimum_to_wake = minimum = 1;
+			timeout = (HZ / 10) * TIME_CHAR(tty);
+			ldata->minimum_to_wake = minimum = 1;
 		}
 	}
 
@@ -1860,9 +1861,9 @@ do_it_again:
 		   TASK_RUNNING. */
 		set_current_state(TASK_INTERRUPTIBLE);
 
-		if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
+		if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
 		    ((minimum - (b - buf)) >= 1))
-			tty->minimum_to_wake = (minimum - (b - buf));
+			ldata->minimum_to_wake = (minimum - (b - buf));
 
 		if (!input_available_p(tty, 0)) {
 			if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
@@ -1881,7 +1882,6 @@ do_it_again:
 				retval = -ERESTARTSYS;
 				break;
 			}
-			/* FIXME: does n_tty_set_room need locking ? */
 			n_tty_set_room(tty);
 			timeout = schedule_timeout(timeout);
 			continue;
@@ -1979,7 +1979,7 @@ do_it_again:
 	remove_wait_queue(&tty->read_wait, &wait);
 
 	if (!waitqueue_active(&tty->read_wait))
-		tty->minimum_to_wake = minimum;
+		ldata->minimum_to_wake = minimum;
 
 	__set_current_state(TASK_RUNNING);
 	size = b - buf;
@@ -2045,7 +2045,7 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
 			retval = -EIO;
 			break;
 		}
-		if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
+		if (O_OPOST(tty)) {
 			while (nr > 0) {
 				ssize_t num = process_output_block(tty, b, nr);
 				if (num < 0) {
@@ -2111,6 +2111,7 @@ break_out:
 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
 							poll_table *wait)
 {
+	struct n_tty_data *ldata = tty->disc_data;
 	unsigned int mask = 0;
 
 	poll_wait(file, &tty->read_wait, wait);
@@ -2125,9 +2126,9 @@ static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
 		mask |= POLLHUP;
 	if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
 		if (MIN_CHAR(tty) && !TIME_CHAR(tty))
-			tty->minimum_to_wake = MIN_CHAR(tty);
+			ldata->minimum_to_wake = MIN_CHAR(tty);
 		else
-			tty->minimum_to_wake = 1;
+			ldata->minimum_to_wake = 1;
 	}
 	if (tty->ops->write && !tty_is_writelocked(tty) &&
 			tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
@@ -2175,6 +2176,18 @@ static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
 	}
 }
 
+static void n_tty_fasync(struct tty_struct *tty, int on)
+{
+	struct n_tty_data *ldata = tty->disc_data;
+
+	if (!waitqueue_active(&tty->read_wait)) {
+		if (on)
+			ldata->minimum_to_wake = 1;
+		else if (!tty->fasync)
+			ldata->minimum_to_wake = N_TTY_BUF_SIZE;
+	}
+}
+
 struct tty_ldisc_ops tty_ldisc_N_TTY = {
 	.magic           = TTY_LDISC_MAGIC,
 	.name            = "n_tty",
@@ -2188,7 +2201,8 @@ struct tty_ldisc_ops tty_ldisc_N_TTY = {
 	.set_termios     = n_tty_set_termios,
 	.poll            = n_tty_poll,
 	.receive_buf     = n_tty_receive_buf,
-	.write_wakeup    = n_tty_write_wakeup
+	.write_wakeup    = n_tty_write_wakeup,
+	.fasync		 = n_tty_fasync,
 };
 
 /**