+
+/**
+ * usb_anchor_urb - anchors an URB while it is processed
+ * @urb: pointer to the urb to anchor
+ * @anchor: pointer to the anchor
+ *
+ * This can be called to have access to URBs which are to be executed
+ * without bothering to track them
+ */
+void usb_anchor_urb(struct urb *urb, struct usb_anchor *anchor)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&anchor->lock, flags);
+ usb_get_urb(urb);
+ list_add_tail(&urb->anchor_list, &anchor->urb_list);
+ urb->anchor = anchor;
+ spin_unlock_irqrestore(&anchor->lock, flags);
+}
+EXPORT_SYMBOL_GPL(usb_anchor_urb);
+
+/**
+ * usb_unanchor_urb - unanchors an URB
+ * @urb: pointer to the urb to anchor
+ *
+ * Call this to stop the system keeping track of this URB
+ */
+void usb_unanchor_urb(struct urb *urb)
+{
+ unsigned long flags;
+ struct usb_anchor *anchor;
+
+ if (!urb)
+ return;
+
+ anchor = urb->anchor;
+ if (!anchor)
+ return;
+
+ spin_lock_irqsave(&anchor->lock, flags);
+ if (unlikely(anchor != urb->anchor)) {
+ /* we've lost the race to another thread */
+ spin_unlock_irqrestore(&anchor->lock, flags);
+ return;
+ }
+ urb->anchor = NULL;
+ list_del(&urb->anchor_list);
+ spin_unlock_irqrestore(&anchor->lock, flags);
+ usb_put_urb(urb);
+ if (list_empty(&anchor->urb_list))
+ wake_up(&anchor->wait);
+}
+EXPORT_SYMBOL_GPL(usb_unanchor_urb);
+