hv_netvsc: Fix the order of num_sc_offered decrement

BugLink: http://bugs.launchpad.net/bugs/1583357

Reorder the code in netvsc_sc_open(), so num_sc_offered is only decremented
after vmbus_open() is called. This avoid pontential race of removing device
before all channels are setup.
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 3f735131)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/net/hyperv/rndis_filter.c

@@ -986,12 +986,6 @@ static void netvsc_sc_open(struct vmbus_channel *new_sc)
 
 	nvscdev = hv_get_drvdata(new_sc->primary_channel->device_obj);
 
-	spin_lock_irqsave(&nvscdev->sc_lock, flags);
-	nvscdev->num_sc_offered--;
-	spin_unlock_irqrestore(&nvscdev->sc_lock, flags);
-	if (nvscdev->num_sc_offered == 0)
-		complete(&nvscdev->channel_init_wait);
-
 	if (chn_index >= nvscdev->num_chn)
 		return;
 
@@ -1004,6 +998,12 @@ static void netvsc_sc_open(struct vmbus_channel *new_sc)
 
 	if (ret == 0)
 		nvscdev->chn_table[chn_index] = new_sc;
+
+	spin_lock_irqsave(&nvscdev->sc_lock, flags);
+	nvscdev->num_sc_offered--;
+	spin_unlock_irqrestore(&nvscdev->sc_lock, flags);
+	if (nvscdev->num_sc_offered == 0)
+		complete(&nvscdev->channel_init_wait);
 }
 
 int rndis_filter_device_add(struct hv_device *dev,