tty: usb-serial krefs

Use kref in the USB serial drivers so that we don't free tty structures
from under the URB receive handlers as has historically been the case if
you were unlucky. This also gives us a framework for general tty drivers to
use tty_port objects and refcount.

Contains two err->dev_err changes merged together to fix clashes in the
-next tree.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 6 deletions

diff --git a/drivers/usb/serial/digi_acceleport.c b/drivers/usb/serial/digi_acceleport.c
index 240aad1acaab..5756ac6d6c92 100644
--- a/drivers/usb/serial/digi_acceleport.c
+++ b/drivers/usb/serial/digi_acceleport.c
@@ -604,7 +604,9 @@ static void digi_wakeup_write_lock(struct work_struct *work)
 
 static void digi_wakeup_write(struct usb_serial_port *port)
 {
-        tty_wakeup(port->port.tty);
+        struct tty_struct *tty = tty_port_tty_get(&port->port);
+        tty_wakeup(tty);
+        tty_kref_put(tty);
 }
 
 
@@ -1668,7 +1670,7 @@ static int digi_read_inb_callback(struct urb *urb)
 {
 
         struct usb_serial_port *port = urb->context;
-        struct tty_struct *tty = port->port.tty;
+        struct tty_struct *tty;
         struct digi_port *priv = usb_get_serial_port_data(port);
         int opcode = ((unsigned char *)urb->transfer_buffer)[0];
         int len = ((unsigned char *)urb->transfer_buffer)[1];
@@ -1692,6 +1694,7 @@ static int digi_read_inb_callback(struct urb *urb)
                 return -1;
         }
 
+        tty = tty_port_tty_get(&port->port);
         spin_lock(&priv->dp_port_lock);
 
         /* check for throttle; if set, do not resubmit read urb */
@@ -1735,6 +1738,7 @@ static int digi_read_inb_callback(struct urb *urb)
                 }
         }
         spin_unlock(&priv->dp_port_lock);
+        tty_kref_put(tty);
 
         if (opcode == DIGI_CMD_RECEIVE_DISABLE)
                 dbg("%s: got RECEIVE_DISABLE", __func__);
@@ -1760,6 +1764,7 @@ static int digi_read_oob_callback(struct urb *urb)
 
         struct usb_serial_port *port = urb->context;
         struct usb_serial *serial = port->serial;
+        struct tty_struct *tty;
         struct digi_port *priv = usb_get_serial_port_data(port);
         int opcode, line, status, val;
         int i;
@@ -1787,10 +1792,11 @@ static int digi_read_oob_callback(struct urb *urb)
                 if (priv == NULL)
                         return -1;
 
+                tty = tty_port_tty_get(&port->port);
                 rts = 0;
                 if (port->port.count)
-                        rts = port->port.tty->termios->c_cflag & CRTSCTS;
-
+                        rts = tty->termios->c_cflag & CRTSCTS;
+                
                 if (opcode == DIGI_CMD_READ_INPUT_SIGNALS) {
                         spin_lock(&priv->dp_port_lock);
                         /* convert from digi flags to termiox flags */
@@ -1798,14 +1804,14 @@ static int digi_read_oob_callback(struct urb *urb)
                                 priv->dp_modem_signals |= TIOCM_CTS;
                                 /* port must be open to use tty struct */
                                 if (rts) {
-                                        port->port.tty->hw_stopped = 0;
+                                        tty->hw_stopped = 0;
                                         digi_wakeup_write(port);
                                 }
                         } else {
                                 priv->dp_modem_signals &= ~TIOCM_CTS;
                                 /* port must be open to use tty struct */
                                 if (rts)
-                                        port->port.tty->hw_stopped = 1;
+                                        tty->hw_stopped = 1;
                         }
                         if (val & DIGI_READ_INPUT_SIGNALS_DSR)
                                 priv->dp_modem_signals |= TIOCM_DSR;
@@ -1830,6 +1836,7 @@ static int digi_read_oob_callback(struct urb *urb)
                 } else if (opcode == DIGI_CMD_IFLUSH_FIFO) {
                         wake_up_interruptible(&priv->dp_flush_wait);
                 }
+                tty_kref_put(tty);
         }
         return 0;