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Commit 54e8e5fc authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
Browse files

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: default avatarPeter Hurley <peter@hurleysoftware.com>
Reviewed-by: default avatarAlan Cox <alan@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6054c16e

drivers/tty/n_tty.c

+2 −2
Original line number Diff line number Diff line
@@ -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);

}



/**

drivers/tty/pty.c

+4 −4
Original line number Diff line number Diff line
@@ -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);

}



/**