The driver did not update its view of the available device buffer space until write() was called in task context. This meant that write_room() would return 0 even after the device had sent a write-unthrottle notification, something which could lead to blocked writers not being woken up (e.g. when using OPOST).
Note that we must also request an unthrottle notification is case a write() request fills the device buffer exactly.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable stable@vger.kernel.org Signed-off-by: Johan Hovold johan@kernel.org --- drivers/usb/serial/keyspan_pda.c | 29 ++++++++++++++++++++--------- 1 file changed, 20 insertions(+), 9 deletions(-)
diff --git a/drivers/usb/serial/keyspan_pda.c b/drivers/usb/serial/keyspan_pda.c index 781b6723379f..39ed3ad32365 100644 --- a/drivers/usb/serial/keyspan_pda.c +++ b/drivers/usb/serial/keyspan_pda.c @@ -40,6 +40,8 @@ #define DRIVER_AUTHOR "Brian Warner warner@lothar.com" #define DRIVER_DESC "USB Keyspan PDA Converter driver"
+#define KEYSPAN_TX_THRESHOLD 16 + struct keyspan_pda_private { int tx_room; int tx_throttled; @@ -110,7 +112,7 @@ static void keyspan_pda_request_unthrottle(struct work_struct *work) 7, /* request_unthrottle */ USB_TYPE_VENDOR | USB_RECIP_INTERFACE | USB_DIR_OUT, - 16, /* value: threshold */ + KEYSPAN_TX_THRESHOLD, 0, /* index */ NULL, 0, @@ -129,6 +131,8 @@ static void keyspan_pda_rx_interrupt(struct urb *urb) int retval; int status = urb->status; struct keyspan_pda_private *priv; + unsigned long flags; + priv = usb_get_serial_port_data(port);
switch (status) { @@ -171,7 +175,10 @@ static void keyspan_pda_rx_interrupt(struct urb *urb) case 1: /* modemline change */ break; case 2: /* tx unthrottle interrupt */ + spin_lock_irqsave(&port->lock, flags); priv->tx_throttled = 0; + priv->tx_room = max(priv->tx_room, KEYSPAN_TX_THRESHOLD); + spin_unlock_irqrestore(&port->lock, flags); /* queue up a wakeup at scheduler time */ usb_serial_port_softint(port); break; @@ -505,7 +512,8 @@ static int keyspan_pda_write(struct tty_struct *tty, goto exit; } } - if (count > priv->tx_room) { + + if (count >= priv->tx_room) { /* we're about to completely fill the Tx buffer, so we'll be throttled afterwards. */ count = priv->tx_room; @@ -560,14 +568,17 @@ static void keyspan_pda_write_bulk_callback(struct urb *urb) static int keyspan_pda_write_room(struct tty_struct *tty) { struct usb_serial_port *port = tty->driver_data; - struct keyspan_pda_private *priv; - priv = usb_get_serial_port_data(port); - /* used by n_tty.c for processing of tabs and such. Giving it our - conservative guess is probably good enough, but needs testing by - running a console through the device. */ - return priv->tx_room; -} + struct keyspan_pda_private *priv = usb_get_serial_port_data(port); + unsigned long flags; + int room = 0; + + spin_lock_irqsave(&port->lock, flags); + if (test_bit(0, &port->write_urbs_free) && !priv->tx_throttled) + room = priv->tx_room; + spin_unlock_irqrestore(&port->lock, flags);
+ return room; +}
static int keyspan_pda_chars_in_buffer(struct tty_struct *tty) {