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, 9 insertions, 6 deletions

diff --git a/drivers/usb/serial/aircable.c b/drivers/usb/serial/aircable.c
index 79ea98c66fa8..99fb7dc59c45 100644
--- a/drivers/usb/serial/aircable.c
+++ b/drivers/usb/serial/aircable.c
@@ -272,7 +272,7 @@ static void aircable_read(struct work_struct *work)
          * 64 bytes, to ensure I do not get throttled.
          * Ask USB mailing list for better aproach.
          */
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
 
         if (!tty) {
                 schedule_work(&priv->rx_work);
@@ -283,12 +283,13 @@ static void aircable_read(struct work_struct *work)
         count = min(64, serial_buf_data_avail(priv->rx_buf));
 
         if (count <= 0)
-                return; /* We have finished sending everything. */
+                goto out; /* We have finished sending everything. */
 
         tty_prepare_flip_string(tty, &data, count);
         if (!data) {
-                err("%s- kzalloc(%d) failed.", __func__, count);
-                return;
+                dev_err(&port->dev, "%s- kzalloc(%d) failed.",
+                                                        __func__, count);
+                goto out;
         }
 
         serial_buf_get(priv->rx_buf, data, count);
@@ -297,7 +298,8 @@ static void aircable_read(struct work_struct *work)
 
         if (serial_buf_data_avail(priv->rx_buf))
                 schedule_work(&priv->rx_work);
-
+out:            
+        tty_kref_put(tty);
         return;
 }
 /* End of private methods */
@@ -495,7 +497,7 @@ static void aircable_read_bulk_callback(struct urb *urb)
         usb_serial_debug_data(debug, &port->dev, __func__,
                                 urb->actual_length, urb->transfer_buffer);
 
-        tty = port->port.tty;
+        tty = tty_port_tty_get(&port->port);
         if (tty && urb->actual_length) {
                 if (urb->actual_length <= 2) {
                         /* This is an incomplete package */
@@ -527,6 +529,7 @@ static void aircable_read_bulk_callback(struct urb *urb)
                 }
                 aircable_read(&priv->rx_work);
         }
+        tty_kref_put(tty);
 
         /* Schedule the next read _if_ we are still open */
         if (port->port.count) {