Update lock_acquire to disable interrupts to eliminate race-conditions, w/ T

src/threads/synch.c

@@ -248,15 +248,16 @@ lock_acquire (struct lock *lock)
   ASSERT (!lock_held_by_current_thread (lock));
 
   struct thread *t = thread_current ();
+  enum intr_level old_level = intr_disable ();
 
-  /* TODO: If a high-priority thread holding a lock sleeps, this may cause a
-     race condition here or break the assumption that donation must occur. */
   if (lock->holder != NULL)
     {
       t->waiting_lock = lock;
       donate_priority (lock->holder);
     }
 
+  intr_set_level (old_level);
+
   sema_down (&lock->semaphore);
   lock->holder = thread_current ();
   t->waiting_lock = NULL;