problem with rtnetlink 'reference' count

[Peter Zijlstra]

Hi,

I just ran across commit:

  019a316992ee ("rtnetlink: add reference counting to prevent module unload 
while dump is in progress")

And that commit is _completely_ broken.

 1) it not in fact a refcount, so using refcount_t is silly
 2) there is a distinct lack of memory barriers, so we can easily
    observe the decrement while the msg_handler is still in progress.
 3) waiting with a schedule()/yield() loop is complete crap and subject
    life-locks, imagine doing that rtnl_unregister_all() from a RT task.

Please fix..