[MPICH] Deadlock with multiple threads

[David Minor]

Hi Mpiers,

The following situtation leads me to deadlock, why?

I have three nodes and two threads on each node. 
There are two communicators, on each node thread 1 (t1) is using communicator 1 (c1)
and thread 2 is using communicator 2.

c1 is involved in a bcast on all three nodes on t1
c2 on all t2's is in a recv from any source, for which a send has not yet been issued.

Why does the bcast on c1 deadlock?  This seems to violate one of the rules for multi-threaded MPI.

When I run the above scenario on 2 nodes there is no deadlock.

Regards,
David
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