Update thread_recalculate_priority to disable interrupts preventing race conditions for access to donors and priorities w/ S

src/threads/thread.c

@@ -417,6 +417,8 @@ void
 thread_recalculate_priority (void)
 {
   struct thread *t = thread_current ();
+  
+  enum intr_level old_level = intr_disable ();
   t->priority = t->base_priority;
 
   /* If there are no donors to the current thread, then the effective
@@ -432,6 +434,7 @@ thread_recalculate_priority (void)
       if (max_donated_priority > t->priority)
         t->priority = max_donated_priority;
     }
+  intr_set_level (old_level);
 }
 
 /* Sets the current thread's nice value to NICE. */