Recently people reported the NIC stops working after
"ifdown eth0; ifup eth0". It turns out in this case the TX queues are not
enabled, after the refactoring of the common detach logic. The patch fixes
the regression.

Fixes: 7b2ee50c0cd5 ("hv_netvsc: common detach logic")
Signed-off-by: Dexuan Cui <de...@microsoft.com>
Cc: sta...@vger.kernel.org
Cc: Stephen Hemminger <sthem...@microsoft.com>
Cc: K. Y. Srinivasan <k...@microsoft.com>
Cc: Haiyang Zhang <haiya...@microsoft.com>
---
 drivers/net/hyperv/netvsc_drv.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index da07ccd..4461e16 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -126,9 +126,20 @@ static int netvsc_open(struct net_device *net)
        }
 
        rdev = nvdev->extension;
-       if (!rdev->link_state)
+       if (!rdev->link_state) {
                netif_carrier_on(net);
 
+               /* When the NIC has sub-channels, usually we enable all the
+                * TX queues after all sub-channels are set up: see
+                * rndis_set_subchannel() -> netif_device_attach(), but in
+                * the case of "ifdown eth0; ifup eth0" where the number of
+                * channels doesn't change, we also must make sure the
+                * TX queues are enabled.
+                */
+               if (atomic_read(&nvdev->open_chn) == nvdev->num_chn)
+                       netif_tx_wake_all_queues(net);
+       }
+
        if (vf_netdev) {
                /* Setting synthetic device up transparently sets
                 * slave as up. If open fails, then slave will be
-- 
2.7.4

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