diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 09a53e7..400433c 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -45,6 +45,14 @@
 #include "hcd.h"
 #include "hub.h"
 
+#ifdef DEBUG
+const char *_urb_list_holder = "NONE";
+#define URB_LIST_HOLDER(n) _urb_list_holder = #n;
+#define URB_LIST_RELEASE   _urb_list_holder = "FREE";
+#else
+#define URB_LIST_HOLDER(n)
+#define URB_LIST_RELEASE
+#endif  
 
 /*-------------------------------------------------------------------------*/
 
@@ -1001,7 +1009,12 @@ int usb_hcd_link_urb_to_ep(struct usb_hcd *hcd, struct urb *urb)
 {
 	int		rc = 0;
 
+#ifdef DEBUG
+	if (!raw_irqs_disabled()) dump_stack();
+#endif
+
 	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)) {
@@ -1034,6 +1047,7 @@ int usb_hcd_link_urb_to_ep(struct usb_hcd *hcd, struct urb *urb)
 		goto done;
 	}
  done:
+	URB_LIST_RELEASE
 	spin_unlock(&hcd_urb_list_lock);
 	return rc;
 }
@@ -1107,9 +1121,33 @@ 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 0
+        if (!spin_trylock(&hcd_urb_list_lock)) {
+	  int i;
+	  printk(KERN_CRIT "HCD URB list locked by %s!\n", _urb_list_holder);
+	  dump_stack();
+	  for (int i = 0; i < 100; i++) schedule();
+	}
+#endif
+	unsigned int flags;
+
+        if (!raw_irqs_disabled()) {
+	  printk(KERN_CRIT "usb_hcd_unlink_urb_from_ep called with interrupts enabled!\n");
+	  dump_stack();
+	}
+	spin_lock_irqsave(&hcd_urb_list_lock, flags);
+#else
 	spin_lock(&hcd_urb_list_lock);
+#endif
+	URB_LIST_HOLDER(usb_hcd_unlink_urb_from_ep)
 	list_del_init(&urb->urb_list);
+	URB_LIST_RELEASE
+#ifdef DEBUG
+	spin_unlock_irqrestore(&hcd_urb_list_lock, flags);
+#else
 	spin_unlock(&hcd_urb_list_lock);
+#endif
 }
 EXPORT_SYMBOL_GPL(usb_hcd_unlink_urb_from_ep);
 
@@ -1448,6 +1486,7 @@ 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;
@@ -1456,6 +1495,7 @@ rescan:
 			continue;
 		usb_get_urb (urb);
 		is_in = usb_urb_dir_in(urb);
+		URB_LIST_RELEASE
 		spin_unlock(&hcd_urb_list_lock);
 
 		/* kick hcd */
@@ -1482,13 +1522,16 @@ rescan:
 
 		/* list contents may have changed */
 		spin_lock(&hcd_urb_list_lock);
+		URB_LIST_HOLDER(usb_hcd_flush_endpoint_RESCAN)
 		goto rescan;
 	}
+	URB_LIST_RELEASE
 	spin_unlock_irq(&hcd_urb_list_lock);
 
 	/* 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;
@@ -1497,6 +1540,7 @@ rescan:
 					urb_list);
 			usb_get_urb (urb);
 		}
+		URB_LIST_RELEASE
 		spin_unlock_irq(&hcd_urb_list_lock);
 
 		if (urb) {