On Tue, 15 Aug 2023 17:43:00 -0700 Tony Nguyen wrote:

+	netif_stop_subqueue(tx_q->vport->netdev, tx_q->idx);
+
+	/* Memory barrier before checking head and tail */
+	smp_mb();
+
+	/* Check again in a case another CPU has just made room available. */
+	if (likely(IDPF_DESC_UNUSED(tx_q) < size))
+		return -EBUSY;
+
+	/* A reprieve! - use start_subqueue because it doesn't call schedule */
+	netif_start_subqueue(tx_q->vport->netdev, tx_q->idx);

Please use the helpers from include/net/netdev_queues.h.