On Tue, 3 Feb 2009, Adam Baker wrote:
If a device using the gspca framework is unplugged while it is still streaming
then the call that is used to free the URBs that have been allocated occurs
after the pointer it uses becomes invalid at the end of gspca_disconnect.
Make another cleanup call in gspca_disconnect while the pointer is still
valid (multiple calls are OK as destroy_urbs checks for pointers already
being NULL.
Signed-off-by: Adam Baker <[email protected]>
---
diff -r 4d0827823ebc linux/drivers/media/video/gspca/gspca.c
--- a/linux/drivers/media/video/gspca/gspca.c Tue Feb 03 10:42:28 2009 +0100
+++ b/linux/drivers/media/video/gspca/gspca.c Tue Feb 03 23:07:34 2009 +0000
@@ -434,6 +434,7 @@ static void destroy_urbs(struct gspca_de
if (urb == NULL)
break;
+ BUG_ON(!gspca_dev->dev);
gspca_dev->urb[i] = NULL;
if (gspca_dev->present)
usb_kill_urb(urb);
@@ -1953,8 +1954,12 @@ void gspca_disconnect(struct usb_interfa
{
struct gspca_dev *gspca_dev = usb_get_intfdata(intf);
+ mutex_lock(&gspca_dev->usb_lock);
gspca_dev->present = 0;
+ mutex_unlock(&gspca_dev->usb_lock);
+ destroy_urbs(gspca_dev);
+ gspca_dev->dev = NULL;
usb_set_intfdata(intf, NULL);
/* release the device */
Again, this solves the problem completely on the Pentium 4 Dual Core
machine. Again, on the K8 machine there is the error message
libv4l2: error dequeuing buf: Resource temporarily unavailable
which, I strongly suspect, has nothing at all to do with the issue at
hand.
I have at this point switched over to
create_singlethread_workqueue(MODULE_NAME)
on both boxes now. I think that your patch would run with this or without
it. So the question is, whether singlethread is in fact better, or not.
Me, I would tend to think it really makes no difference at all, because
that was not what the problem was.
So, the next question is whether this patch gets accepted or not. It
appears to solve *our* problem. Clearly, the big question is whether it
could break something else.
Theodore Kilgore
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