static void
close_files (struct thread *t)
{
  struct list_elem *cur;
  while (!list_empty (&t->open_files))
    {
      cur = list_pop_back (&t->open_files);
      struct open_file *file_data = list_entry (cur, struct open_file, elem);
      file_close (file_data->file);
      free (file_data);
    }
}