didn't do a while

kern/thread/synch.c

@@ -189,7 +189,7 @@ void lock_acquire(struct lock * lock)
   
   spinlock_acquire(&(lock->spin));
   
-  if (lock->owner)
+  while (lock->owner)
   {
     wchan_lock(lock->wc);
     spinlock_release(&(lock->spin));