n_tty: Only perform wakeups for waiters

Only wakeup the _waiting_ reader, polls and/or writer(s).

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 2caa2936d1b1be5ffc11dc4c6837c5fcda5c3879..c7f8f7bc14233d3bcaefe4e7496d6f312d8ecaca 100644 (file)
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -274,7 +274,8 @@ static void n_tty_check_unthrottle(struct tty_struct *tty)
                        return;
                n_tty_set_room(tty);
                n_tty_write_wakeup(tty->link);
-               wake_up_interruptible_poll(&tty->link->write_wait, POLLOUT);
+               if (waitqueue_active(&tty->link->write_wait))
+                       wake_up_interruptible_poll(&tty->link->write_wait, POLLOUT);
                return;
        }
 
@@ -349,7 +350,8 @@ static void n_tty_packet_mode_flush(struct tty_struct *tty)
        spin_lock_irqsave(&tty->ctrl_lock, flags);
        if (tty->link->packet) {
                tty->ctrl_status |= TIOCPKT_FLUSHREAD;
-               wake_up_interruptible(&tty->link->read_wait);
+               if (waitqueue_active(&tty->link->read_wait))
+                       wake_up_interruptible(&tty->link->read_wait);
        }
        spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 }
@@ -1155,7 +1157,8 @@ static void n_tty_receive_break(struct tty_struct *tty)
                put_tty_queue('\0', ldata);
        }
        put_tty_queue('\0', ldata);
-       wake_up_interruptible(&tty->read_wait);
+       if (waitqueue_active(&tty->read_wait))
+               wake_up_interruptible(&tty->read_wait);
 }
 
 /**
@@ -1213,7 +1216,8 @@ static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
                put_tty_queue('\0', ldata);
        else
                put_tty_queue(c, ldata);
-       wake_up_interruptible(&tty->read_wait);
+       if (waitqueue_active(&tty->read_wait))
+               wake_up_interruptible(&tty->read_wait);
 }
 
 static void
@@ -1802,8 +1806,10 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
                start_tty(tty);
 
        /* The termios change make the tty ready for I/O */
-       wake_up_interruptible(&tty->write_wait);
-       wake_up_interruptible(&tty->read_wait);
+       if (waitqueue_active(&tty->write_wait))
+               wake_up_interruptible(&tty->write_wait);
+       if (waitqueue_active(&tty->read_wait))
+               wake_up_interruptible(&tty->read_wait);
 }
 
 /**