staging: usbip: avoid deadlock in vhci_device_unlink_cleanup()

staging: usbip: avoid deadlock in vhci_device_unlink_cleanup()

Almost all of usbip assumes that the_controller->lock is acquired
before vdev->priv_lock. The exception is in
vhci_device_unlink_cleanup(), where locks are acquired in the
reverse order. This leads to occasional deadlocks.

Fixing this is a bit fiddly, as the_controller->lock can't be held
when calling usb_hcd_unlink_urb_from_ep() in the middle of the list
traversal. As I can't rule out concurrent callers to this function
(perhaps it is safe?), the code here becomes slightly uglier - when
locks are dropped in the middle so the list may have emptied itself
(not even list_for_each_entry_safe is safe here).

Signed-off-by: Bernard Blackham <b-linuxgit@largestprime.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>