Update donate priority to add an assertion that intrrupts are disabled, w/ T

src/threads/synch.c

@@ -196,9 +196,12 @@ lock_init (struct lock *lock)
 
 /* Current thread donates its priority to donee, iteratively
    propagating the donation in the case of chains in the wait-for graph.
-   Also keeps track of the donation by updating the donors list. */
+   Also keeps track of the donation by updating the donors list. Expects
+   interrupts to be disabled. */
 static void
 donate_priority (struct thread *donee) {
+  ASSERT (intr_get_level () == INTR_OFF);
+
   struct thread *donor = thread_current ();
   list_push_back (&donee->donors_list, &donor->donor_elem);