static struct ath_buf *ath_tx_get_buffer(struct ath_softc *sc)
{
	struct ath_buf *bf = NULL;

	spin_lock_bh(&sc->tx.txbuflock);

	if (unlikely(list_empty(&sc->tx.txbuf))) {
		spin_unlock_bh(&sc->tx.txbuflock);
		return NULL;
	}

	bf = list_first_entry(&sc->tx.txbuf, struct ath_buf, list);
	list_del(&bf->list);

	spin_unlock_bh(&sc->tx.txbuflock);

	return bf;
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.