[ofa-general] lock dependency in ib_user_mad

[Sean Hefty]

> This should be fine (and comes from an earlier set of changes to fix
> deadlocks): ib_umad_close() does a downgrade_write() before calling
> ib_unregister_mad_agent(), so it only holds the mutex with a read
> lock, which means that queue_packet() should be able to take another
> read lock.

I'll see if I can reproduce and get more info.  I thought the mutex was 
contributing to the hang, but you're right.

> Unless there's something that prevents one thread from taking a read
> lock twice?  What kernel are you seeing these problems with?

I'm running 2.6.24-rc3.

I'm out on vacation through the end of the year, so I'm not sure if I'll 
be able to debug this further for a couple of weeks.

- Sean