Commit 22bc63c5 authored by Michael S. Tsirkin's avatar Michael S. Tsirkin
Browse files

virtio_net: move txq wakeups under tx q lock 



We currently check num_free outside tx q lock
which is unsafe: new packets can arrive meanwhile
and there won't be space in the queue.
Thus a spurious queue wakeup causing overhead
and even packet drops.

Move the check under the lock to fix that.

Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 5a2f966d

drivers/net/virtio_net.c

+7 −6
Original line number Diff line number Diff line
@@ -1517,11 +1517,12 @@ static void virtnet_poll_cleantx(struct receive_queue *rq) 


	if (__netif_tx_trylock(txq)) {

		free_old_xmit_skbs(sq, true);

		__netif_tx_unlock(txq);

	}



		if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)

			netif_tx_wake_queue(txq);



		__netif_tx_unlock(txq);

	}

}



static int virtnet_poll(struct napi_struct *napi, int budget)
@@ -1606,6 +1607,9 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) 
	virtqueue_disable_cb(sq->vq);

	free_old_xmit_skbs(sq, true);



	if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)

		netif_tx_wake_queue(txq);



	opaque = virtqueue_enable_cb_prepare(sq->vq);



	done = napi_complete_done(napi, 0);
@@ -1626,9 +1630,6 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) 
		}

	}



	if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)

		netif_tx_wake_queue(txq);



	return 0;

}