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Subject[PATCH 4.18 121/150] virtio_net: avoid using netif_tx_disable() for serializing tx routine
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ake Koomsin <ake@igel.co.jp>

[ Upstream commit 05c998b738fdd3e5d6a257bcacc8f34b6284d795 ]

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() in case 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_bh()/netif_tx_unlock_bh() 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>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/virtio_net.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2162,8 +2162,9 @@ static void virtnet_freeze_down(struct v
/* Make sure no work handler is accessing the device */
flush_work(&vi->config_work);

+ netif_tx_lock_bh(vi->dev);
netif_device_detach(vi->dev);
- netif_tx_disable(vi->dev);
+ netif_tx_unlock_bh(vi->dev);
cancel_delayed_work_sync(&vi->refill);

if (netif_running(vi->dev)) {
@@ -2199,7 +2200,9 @@ static int virtnet_restore_up(struct vir
}
}

+ netif_tx_lock_bh(vi->dev);
netif_device_attach(vi->dev);
+ netif_tx_unlock_bh(vi->dev);
return err;
}


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