Subject: [PATCH 19/39] virtio_net: avoid using netif_tx_disable() for serializing tx routine

From: Ake Koomsin <[email-masked]>
Date: Wed, 17 Oct 2018 19:44:12 +0900

[ 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 <[email-masked]>
Acked-by: Jason Wang <[email-masked]>
Acked-by: Michael S. Tsirkin <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 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 2b6ec927809e..500e2d8f10bc 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2162,8 +2162,9 @@ 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_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 virtio_device *vdev)
 		}
 	}
 
+	netif_tx_lock_bh(vi->dev);
 	netif_device_attach(vi->dev);
+	netif_tx_unlock_bh(vi->dev);
 	return err;
 }
 
-- 
2.19.1