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, 7 deletions

diff --git a/drivers/usb/serial/sierra.c b/drivers/usb/serial/sierra.c
index ea1a103c99be..8b9eaf383679 100644
--- a/drivers/usb/serial/sierra.c
+++ b/drivers/usb/serial/sierra.c
@@ -440,14 +440,14 @@ static void sierra_indat_callback(struct urb *urb)
                 dbg("%s: nonzero status: %d on endpoint %02x.",
                     __func__, status, endpoint);
         } else {
-                tty = port->port.tty;
                 if (urb->actual_length) {
+                tty = tty_port_tty_get(&port->port);
                         tty_buffer_request_room(tty, urb->actual_length);
                         tty_insert_flip_string(tty, data, urb->actual_length);
                         tty_flip_buffer_push(tty);
-                } else {
+                        tty_kref_put(tty);
+                } else
                         dbg("%s: empty read urb received", __func__);
-                }
 
                 /* Resubmit urb so we continue receiving */
                 if (port->port.count && status != -ESHUTDOWN) {
@@ -485,6 +485,7 @@ static void sierra_instat_callback(struct urb *urb)
                         unsigned char signals = *((unsigned char *)
                                         urb->transfer_buffer +
                                         sizeof(struct usb_ctrlrequest));
+                        struct tty_struct *tty;
 
                         dbg("%s: signal x%x", __func__, signals);
 
@@ -494,9 +495,11 @@ static void sierra_instat_callback(struct urb *urb)
                         portdata->dsr_state = ((signals & 0x02) ? 1 : 0);
                         portdata->ri_state = ((signals & 0x08) ? 1 : 0);
 
-                        if (port->port.tty && !C_CLOCAL(port->port.tty) &&
+                        tty = tty_port_tty_get(&port->port);
+                        if (tty && !C_CLOCAL(tty) &&
                                         old_dcd_state && !portdata->dcd_state)
-                                tty_hangup(port->port.tty);
+                                tty_hangup(tty);
+                        tty_kref_put(tty);
                 } else {
                         dbg("%s: type %x req %x", __func__,
                                 req_pkt->bRequestType, req_pkt->bRequest);
@@ -616,8 +619,7 @@ static void sierra_close(struct tty_struct *tty,
         }
 
         usb_kill_urb(port->interrupt_in_urb);
-
-        port->port.tty = NULL;  /* FIXME */
+        tty_port_tty_set(&port->port, NULL);
 }
 
 static int sierra_startup(struct usb_serial *serial)