[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>

diff --git a/drivers/net/iseries_veth.c b/drivers/net/iseries_veth.c
index 1edecb1..13ed8dc 100644 (file)
--- 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);