tty: Remove ASYNC_CLOSING checks in open()/hangup() methods

Since at least before 2.6.30, tty drivers that do not drop the tty lock
while closing cannot observe ASYNC_CLOSING set while holding the
tty lock; this includes the tty driver's open() and hangup() methods,
since the tty core calls these methods holding the tty lock.

For these drivers, waiting for ASYNC_CLOSING to clear while opening
is not required, since this condition cannot occur. Similarly, even
when the open() method drops and reacquires the tty lock after
blocking, ASYNC_CLOSING cannot be set (again, for drivers that
do not drop the tty lock while closing).

Now that tty port drivers no longer drop the tty lock while closing
(since 'tty: Remove tty_wait_until_sent_from_close()'), the same
conditions apply: waiting for ASYNC_CLOSING to clear while opening
is not required, nor is re-checking ASYNC_CLOSING after dropping and
reacquiring the tty lock while blocking (eg., in *_block_til_ready()).

Note: The ASYNC_CLOSING flag state is still maintained since several
bitrotting drivers use it for (dubious) other purposes.

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

1 files changed, 1 insertions, 12 deletions

diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index d7d9f9cde964..0e1cf0495fb9 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -363,16 +363,6 @@ int tty_port_block_til_ready(struct tty_port *port,
 	unsigned long flags;
 	DEFINE_WAIT(wait);
 
-	/* block if port is in the process of being closed */
-	if (port->flags & ASYNC_CLOSING) {
-		wait_event_interruptible_tty(tty, port->close_wait,
-				!(port->flags & ASYNC_CLOSING));
-		if (port->flags & ASYNC_HUP_NOTIFY)
-			return -EAGAIN;
-		else
-			return -ERESTARTSYS;
-	}
-
 	/* if non-blocking mode is set we can pass directly to open unless
 	   the port has just hung up or is in another error state */
 	if (tty->flags & (1 << TTY_IO_ERROR)) {
@@ -423,8 +413,7 @@ int tty_port_block_til_ready(struct tty_port *port,
 		 * Never ask drivers if CLOCAL is set, this causes troubles
 		 * on some hardware.
 		 */
-		if (!(port->flags & ASYNC_CLOSING) &&
-				(do_clocal || tty_port_carrier_raised(port)))
+		if (do_clocal || tty_port_carrier_raised(port))
 			break;
 		if (signal_pending(current)) {
 			retval = -ERESTARTSYS;