Refactor ready_list_reinsert to require being called with interrupts disabled

src/threads/synch.c

@@ -220,7 +220,9 @@ donate_priority (struct thread *donee) {
           /* Only the sink node of the WFG isn't waiting for a lock and
              could be on the ready list. Thus, as its priority changed,
              it must be reinserted into the list. */
+          enum intr_level old_level = intr_disable ();
           ready_list_reinsert (donee);
+          intr_set_level (old_level);
           donee = NULL;
         }
       else

src/threads/thread.c

@@ -467,22 +467,20 @@ thread_get_recent_cpu (void)
 
 /* Reinsert thread t into the ready list at its correct position
    in descending order of priority. Used when this thread's priority
-   may have changed. */
+   may have changed. Must be called with interrupts disabled. */
 void
 ready_list_reinsert (struct thread *t)
 {
-  enum intr_level old_level = intr_disable ();
+  ASSERT (intr_get_level () == INTR_OFF);
 
   /* If the thread isn't ready to run, do nothing. */
-  if (t->status == THREAD_READY)
-    {
+  if (t->status != THREAD_READY)
+    return;
+
   list_remove (&t->elem);
   list_insert_ordered (&ready_list, &t->elem, priority_more, NULL);
 }
 
-  intr_set_level (old_level);
-}
-
 /* Idle thread.  Executes when no other thread is ready to run.
 
    The idle thread is initially put on the ready list by