[PATCH] linux-2.5.41/drivers/usb/core/hub.c called down() from interrupt context

	On second thought after reading Oliver Neukum's question about
"shaving off a cycle or two", here is version of my fix for down()
being called from interrupt context that uses unlikely() to get the
speed advantage that would be available from BUG_ON(), while still
ensuring that the condition is executed even if assertions are
compiled out.

drivers/usb/core/hub.c

@@ -943,7 +943,9 @@ static void usb_hub_events(void)
 
 		list_del_init(tmp);
 
-		down(&hub->khubd_sem); /* never blocks, we were on list */
+		if (unlikely(down_trylock(&hub->khubd_sem)))
+			BUG();	/* never blocks, we were on list */
+
 		spin_unlock_irqrestore(&hub_event_lock, flags);
 
 		if (hub->error) {