USB: add extension of anchor API, usb_unlink_anchored_urbs

This adds the ability to trigger asynchronous unlinks of anchored URBs. This
is needed for error handling in the comntext of completion handlers, which
cannot sleep.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/urb.c

@@ -589,6 +589,30 @@ void usb_kill_anchored_urbs(struct usb_anchor *anchor)
 }
 EXPORT_SYMBOL_GPL(usb_kill_anchored_urbs);
 
+/**
+ * usb_unlink_anchored_urbs - asynchronously cancel transfer requests en masse
+ * @anchor: anchor the requests are bound to
+ *
+ * this allows all outstanding URBs to be unlinked starting
+ * from the back of the queue. This function is asynchronous.
+ * The unlinking is just tiggered. It may happen after this
+ * function has returned.
+ */
+void usb_unlink_anchored_urbs(struct usb_anchor *anchor)
+{
+	struct urb *victim;
+
+	spin_lock_irq(&anchor->lock);
+	while (!list_empty(&anchor->urb_list)) {
+		victim = list_entry(anchor->urb_list.prev, struct urb,
+				    anchor_list);
+		/* this will unanchor the URB */
+		usb_unlink_urb(victim);
+	}
+	spin_unlock_irq(&anchor->lock);
+}
+EXPORT_SYMBOL_GPL(usb_unlink_anchored_urbs);
+
 /**
  * usb_wait_anchor_empty_timeout - wait for an anchor to be unused
  * @anchor: the anchor you want to become unused

include/linux/usb.h

@@ -1451,6 +1451,7 @@ extern int usb_submit_urb(struct urb *urb, gfp_t mem_flags);
 extern int usb_unlink_urb(struct urb *urb);
 extern void usb_kill_urb(struct urb *urb);
 extern void usb_kill_anchored_urbs(struct usb_anchor *anchor);
+extern void usb_unlink_anchored_urbs(struct usb_anchor *anchor);
 extern void usb_anchor_urb(struct urb *urb, struct usb_anchor *anchor);
 extern void usb_unanchor_urb(struct urb *urb);
 extern int usb_wait_anchor_empty_timeout(struct usb_anchor *anchor,