/* unlock interrupts with each step */
    last_select_cb_ctr = select_cb_ctr;
    SYS_ARCH_UNPROTECT(lev);
    /* this makes sure interrupt protection time is short */
    SYS_ARCH_PROTECT(lev);

	if (sock->select_waiting == 0) {
		/* noone is waiting for this socket, no need to check select_cb_list */
		SYS_ARCH_UNPROTECT(lev);
		return;
	}

    if (last_select_cb_ctr != select_cb_ctr) {
      /* someone has changed select_cb_list, restart at the beginning */
      goto again;
    }