Re: [PATCH v2] virtio_net: avoid using netif_tx_disable() for serializing tx routine

From: Jason Wang
Date: Wed Oct 17 2018 - 05:02:45 EST

On 2018/10/17 äå3:59, Ake Koomsin wrote:
Commit 713a98d90c5e ("virtio-net: serialize tx routine during reset")
introduces netif_tx_disable() after netif_device_detach() in order to
avoid use-after-free of tx queues. However, there are two issues.

1) Its operation is redundant with netif_device_detach() if the interface
is running.
2) In case of the interface is not running before suspending and
resuming, the tx does not get resumed by netif_device_attach().
This results in losing network connectivity.

It is better to use netif_tx_lock()/netif_tx_unlock() instead for
serializing tx routine during reset. This also preserves the symmetry
of netif_device_detach() and netif_device_attach().

Fixes commit 713a98d90c5e ("virtio-net: serialize tx routine during reset")
Signed-off-by: Ake Koomsin <ake@xxxxxxxxxx>
drivers/net/virtio_net.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 3f5aa59c37b7..41ccf9c994a4 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2267,8 +2267,9 @@ static void virtnet_freeze_down(struct virtio_device *vdev)
/* Make sure no work handler is accessing the device */
+ netif_tx_lock(vi->dev);
- netif_tx_disable(vi->dev);
+ netif_tx_unlock(vi->dev);

Sorry for not finding this earlier. I think we should use netif_tx_lock_bh() to prevent start_xmit() to run under bh.


if (netif_running(vi->dev)) {
@@ -2304,7 +2305,9 @@ static int virtnet_restore_up(struct virtio_device *vdev)
+ netif_tx_lock(vi->dev);
+ netif_tx_unlock(vi->dev);
return err;