[openib-general] atomic_read in ib_unregister_mad_agent()

[Roland Dreier]

    Shirley> It's better to use semaphore instead of atomic_read to
    Shirley> check the reference count 0 in wait_event() in
    Shirley> ib_unregister_mad_agent(). Agree?

I don't see how one uses a semaphore to wait for a reference count to
become zero (semaphores sleep until their count is non-zero).

 - R.