Michael S. Tsirkin
2021-Apr-13 05:47 UTC
[PATCH RFC v2 3/4] virtio_net: move tx vq operation under tx queue lock
It's unsafe to operate a vq from multiple threads. Unfortunately this is exactly what we do when invoking clean tx poll from rx napi. As a fix move everything that deals with the vq to under tx lock. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- drivers/net/virtio_net.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 16d5abed582c..460ccdbb840e 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1505,6 +1505,8 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) struct virtnet_info *vi = sq->vq->vdev->priv; unsigned int index = vq2txq(sq->vq); struct netdev_queue *txq; + int opaque; + bool done; if (unlikely(is_xdp_raw_buffer_queue(vi, index))) { /* We don't need to enable cb for XDP */ @@ -1514,10 +1516,28 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) txq = netdev_get_tx_queue(vi->dev, index); __netif_tx_lock(txq, raw_smp_processor_id()); + virtqueue_disable_cb(sq->vq); free_old_xmit_skbs(sq, true); + + opaque = virtqueue_enable_cb_prepare(sq->vq); + + done = napi_complete_done(napi, 0); + + if (!done) + virtqueue_disable_cb(sq->vq); + __netif_tx_unlock(txq); - virtqueue_napi_complete(napi, sq->vq, 0); + if (done) { + if (unlikely(virtqueue_poll(sq->vq, opaque))) { + if (napi_schedule_prep(napi)) { + __netif_tx_lock(txq, raw_smp_processor_id()); + virtqueue_disable_cb(sq->vq); + __netif_tx_unlock(txq); + __napi_schedule(napi); + } + } + } if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) netif_tx_wake_queue(txq); -- MST
Jason Wang
2021-Apr-13 08:54 UTC
[PATCH RFC v2 3/4] virtio_net: move tx vq operation under tx queue lock
? 2021/4/13 ??1:47, Michael S. Tsirkin ??:> It's unsafe to operate a vq from multiple threads. > Unfortunately this is exactly what we do when invoking > clean tx poll from rx napi. > As a fix move everything that deals with the vq to under tx lock. > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > --- > drivers/net/virtio_net.c | 22 +++++++++++++++++++++- > 1 file changed, 21 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 16d5abed582c..460ccdbb840e 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -1505,6 +1505,8 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) > struct virtnet_info *vi = sq->vq->vdev->priv; > unsigned int index = vq2txq(sq->vq); > struct netdev_queue *txq; > + int opaque; > + bool done; > > if (unlikely(is_xdp_raw_buffer_queue(vi, index))) { > /* We don't need to enable cb for XDP */ > @@ -1514,10 +1516,28 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget) > > txq = netdev_get_tx_queue(vi->dev, index); > __netif_tx_lock(txq, raw_smp_processor_id()); > + virtqueue_disable_cb(sq->vq); > free_old_xmit_skbs(sq, true); > + > + opaque = virtqueue_enable_cb_prepare(sq->vq); > + > + done = napi_complete_done(napi, 0); > + > + if (!done) > + virtqueue_disable_cb(sq->vq); > + > __netif_tx_unlock(txq); > > - virtqueue_napi_complete(napi, sq->vq, 0);So I wonder why not simply move __netif_tx_unlock() after virtqueue_napi_complete()? Thanks> + if (done) { > + if (unlikely(virtqueue_poll(sq->vq, opaque))) { > + if (napi_schedule_prep(napi)) { > + __netif_tx_lock(txq, raw_smp_processor_id()); > + virtqueue_disable_cb(sq->vq); > + __netif_tx_unlock(txq); > + __napi_schedule(napi); > + } > + } > + } > > if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS) > netif_tx_wake_queue(txq);