[PATCH] iseries_veth: Cleanup skbs to prevent unregister_netdevice() hanging

Hi Andrew, Jeff,

The iseries_veth driver is badly behaved in that it will keep TX packets
hanging around forever if they're not ACK'ed and the queue never fills up.

This causes the unregister_netdevice code to wait forever when we try to take
the device down, because there's still skbs around with references to our
struct net_device.

There's already code to cleanup any un-ACK'ed packets in veth_stop_connection()
but it's being called after we unregister the net_device, which is too late.

The fix is to rearrange the module exit function so that we cleanup any
outstanding skbs and then unregister the driver.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>

1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/net/iseries_veth.c b/drivers/net/iseries_veth.c
index 1edecb10993d..13ed8dc1e91d 100644
--- a/drivers/net/iseries_veth.c
+++ b/drivers/net/iseries_veth.c
@@ -1388,18 +1388,25 @@ void __exit veth_module_cleanup(void)
 {
         int i;
 
-        vio_unregister_driver(&veth_driver);
+        /* Stop the queues first to stop any new packets being sent. */
+        for (i = 0; i < HVMAXARCHITECTEDVIRTUALLANS; i++)
+                if (veth_dev[i])
+                        netif_stop_queue(veth_dev[i]);
 
+        /* Stop the connections before we unregister the driver. This
+         * ensures there's no skbs lying around holding the device open. */
         for (i = 0; i < HVMAXARCHITECTEDLPS; ++i)
                 veth_stop_connection(i);
 
         HvLpEvent_unregisterHandler(HvLpEvent_Type_VirtualLan);
 
         /* Hypervisor callbacks may have scheduled more work while we
-         * were destroying connections. Now that we've disconnected from
+         * were stoping connections. Now that we've disconnected from
          * the hypervisor make sure everything's finished. */
         flush_scheduled_work();
 
+        vio_unregister_driver(&veth_driver);
+
         for (i = 0; i < HVMAXARCHITECTEDLPS; ++i)
                 veth_destroy_connection(i);