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SubjectRe: [PATCH v2] virtio_net: avoid using netif_tx_disable() for serializing tx routine
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On 2018/10/17 下午3:59, 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@igel.co.jp>
> ---
> 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 */
> flush_work(&vi->config_work);
>
> + netif_tx_lock(vi->dev);
> netif_device_detach(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.

Thanks


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

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