pty: Don't claim slave's ctrl_lock for master's packet mode

The slave's ctrl_lock serializes updates to the ctrl_status field
only, whereas the master's ctrl_lock serializes updates to the
packet mode enable (ie., the master does not have ctrl_status and
the slave does not have packet mode). Thus, claiming the slave's
ctrl_lock to access ->packet is useless.

Unlocked reads of ->packet are already smp-safe.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Alan Cox <alan@linux.intel.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 d521058ee55a98236fc69ee520ca1eed5dfaae9f..cd725cc6e21e0b340a79d5780ec9de31c5ed6b39 100644 (file)
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -351,13 +351,13 @@ static void n_tty_packet_mode_flush(struct tty_struct *tty)
 {
        unsigned long flags;
 
-       spin_lock_irqsave(&tty->ctrl_lock, flags);
        if (tty->link->packet) {
+               spin_lock_irqsave(&tty->ctrl_lock, flags);
                tty->ctrl_status |= TIOCPKT_FLUSHREAD;
+               spin_unlock_irqrestore(&tty->ctrl_lock, flags);
                if (waitqueue_active(&tty->link->read_wait))
                        wake_up_interruptible(&tty->link->read_wait);
        }
-       spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 }
 
 /**

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 29b5eeb018560e6f763cd68a6d28e987d5bcebcd..e554393d5551192997dc1048194b76bcc70b62e4 100644 (file)
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -339,26 +339,26 @@ static void pty_start(struct tty_struct *tty)
 {
        unsigned long flags;
 
-       spin_lock_irqsave(&tty->ctrl_lock, flags);
        if (tty->link && tty->link->packet) {
+               spin_lock_irqsave(&tty->ctrl_lock, flags);
                tty->ctrl_status &= ~TIOCPKT_STOP;
                tty->ctrl_status |= TIOCPKT_START;
+               spin_unlock_irqrestore(&tty->ctrl_lock, flags);
                wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
        }
-       spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 }
 
 static void pty_stop(struct tty_struct *tty)
 {
        unsigned long flags;
 
-       spin_lock_irqsave(&tty->ctrl_lock, flags);
        if (tty->link && tty->link->packet) {
+               spin_lock_irqsave(&tty->ctrl_lock, flags);
                tty->ctrl_status &= ~TIOCPKT_START;
                tty->ctrl_status |= TIOCPKT_STOP;
+               spin_unlock_irqrestore(&tty->ctrl_lock, flags);
                wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
        }
-       spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 }
 
 /**