From: "Eric W. Biederman" <redacted>
Date: Sun, 29 Nov 2009 17:45:58 -0800

Additionally it appears that we moved the route cache flush after
the final synchronize_net, which seems wrong and there was no
explanation.  So I have restored the original location of the final
synchronize_net.

I think the idea was that it's important for all pending stale
RCU references to the device to be gone before we send out the
notifier.  And that's why the synchronize_net() comes first.

This needs more thought.