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>

2 files changed, 25 insertions, 0 deletions

diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
index 9d7e63292c01..1d3ed1322fbe 100644
--- a/drivers/usb/core/urb.c
+++ b/drivers/usb/core/urb.c
@@ -590,6 +590,30 @@ 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
  * @timeout: how long you are willing to wait in milliseconds
diff --git a/include/linux/usb.h b/include/linux/usb.h
index dd9733cc0ac2..52c449e4bdcd 100644
--- a/include/linux/usb.h
+++ b/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,