tsnep: Fix XDP_RING_NEED_WAKEUP for empty fill ring

[ Upstream commit 9a91c05 ]

The fill ring of the XDP socket may contain not enough buffers to
completey fill the RX queue during socket creation. In this case the
flag XDP_RING_NEED_WAKEUP is not set as this flag is only set if the RX
queue is not completely filled during polling.

Set XDP_RING_NEED_WAKEUP flag also if RX queue is not completely filled
during XDP socket creation.

Fixes: 3fc2333 ("tsnep: Add XDP socket zero-copy RX support")
Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/ethernet/engleder/tsnep_main.c

@@ -1711,6 +1711,19 @@ static void tsnep_rx_reopen_xsk(struct tsnep_rx *rx)
 			allocated--;
 		}
 	}
+
+	/* set need wakeup flag immediately if ring is not filled completely,
+	 * first polling would be too late as need wakeup signalisation would
+	 * be delayed for an indefinite time
+	 */
+	if (xsk_uses_need_wakeup(rx->xsk_pool)) {
+		int desc_available = tsnep_rx_desc_available(rx);
+
+		if (desc_available)
+			xsk_set_rx_need_wakeup(rx->xsk_pool);
+		else
+			xsk_clear_rx_need_wakeup(rx->xsk_pool);
+	}
 }
 
 static bool tsnep_pending(struct tsnep_queue *queue)