diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 09a53e7..20db659 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -45,6 +45,12 @@
 #include "hcd.h"
 #include "hub.h"
 
+#ifdef DEBUG
+const char *_urb_list_holder = "NONE";
+#define URB_LIST_HOLDER(n) _urb_list_holder = #n;
+#else
+#define URB_LIST_HOLDER(n)
+#endif  
 
 /*-------------------------------------------------------------------------*/
 
@@ -1002,6 +1008,7 @@ int usb_hcd_link_urb_to_ep(struct usb_hcd *hcd, struct urb *urb)
 	int		rc = 0;
 
 	spin_lock(&hcd_urb_list_lock);
+	URB_LIST_HOLDER(usb_hcd_link_urb_to_ep)
 
 	/* Check that the URB isn't being killed */
 	if (unlikely(urb->reject)) {
@@ -1107,7 +1114,15 @@ EXPORT_SYMBOL_GPL(usb_hcd_check_unlink_urb);
 void usb_hcd_unlink_urb_from_ep(struct usb_hcd *hcd, struct urb *urb)
 {
 	/* clear all state linking urb to this dev (and hcd) */
+#ifdef DEBUG
+        if (!spin_trylock(&hcd_urb_list_lock)) {
+	  printk(KERN_CRIT "HCD URB list locked by %s!\n", _urb_list_holder);
+#endif
 	spin_lock(&hcd_urb_list_lock);
+	URB_LIST_HOLDER(usb_hcd_unlink_urb_from_ep)
+#ifdef DEBUG
+	}
+#endif
 	list_del_init(&urb->urb_list);
 	spin_unlock(&hcd_urb_list_lock);
 }
@@ -1448,6 +1463,7 @@ void usb_hcd_flush_endpoint(struct usb_device *udev,
 
 	/* No more submits can occur */
 	spin_lock_irq(&hcd_urb_list_lock);
+	URB_LIST_HOLDER(usb_hcd_flush_endpoint_INITIAL)
 rescan:
 	list_for_each_entry (urb, &ep->urb_list, urb_list) {
 		int	is_in;
@@ -1482,6 +1498,7 @@ rescan:
 
 		/* list contents may have changed */
 		spin_lock(&hcd_urb_list_lock);
+		URB_LIST_HOLDER(usb_hcd_flush_endpoint_RESCAN)
 		goto rescan;
 	}
 	spin_unlock_irq(&hcd_urb_list_lock);
@@ -1489,6 +1506,7 @@ rescan:
 	/* Wait until the endpoint queue is completely empty */
 	while (!list_empty (&ep->urb_list)) {
 		spin_lock_irq(&hcd_urb_list_lock);
+		URB_LIST_HOLDER(usb_hcd_flush_endpoint_LIST)
 
 		/* The list may have changed while we acquired the spinlock */
 		urb = NULL;