[PATCH v2 tty-next 6/8] n_tty: Only perform wakeups for waiters

[Peter Hurley]

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

Signed-off-by: Peter Hurley <pe...@hurleysoftware.com>
---
 drivers/tty/n_tty.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index aae171e..5254082 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -275,7 +275,8 @@ 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;
        }
 
@@ -350,7 +351,8 @@ 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);
 }
@@ -1158,7 +1160,8 @@ 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);
 }
 
 /**
@@ -1216,7 +1219,8 @@ 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
@@ -1811,8 +1815,10 @@ 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);
 }
 
 /**
-- 
1.8.1.2

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