static void ath_tx_return_buffer(struct ath_softc *sc, struct ath_buf *bf)
{
	spin_lock_bh(&sc->tx.txbuflock);
	list_add_tail(&bf->list, &sc->tx.txbuf);
	spin_unlock_bh(&sc->tx.txbuflock);
}

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.