Work around a race condition in the TCP BTL's proc setup code.
The Cisco MTT results have been failing on TCP tests due to a
"dropped connection" message some percentage of the time.
Some digging shows that the issue happens in a combination of
multiple NICs and multiple threads. The race is detailed in
https://github.com/open-mpi/ompi/issues/3035#issuecomment-429500032.
This patch doesn't fix the race, but avoids it by forcing
the MPI layer to complete all calls to add_procs across the
entire job before any process leaves MPI_INIT. It also
reduces the scalability of the TCP BTL by increasing start-up
time, but better than hanging.
The long term fix is to do all endpoint setup in the first
call to add_procs for a given remote proc, removing the
race. THis patch is a work around until that patch can
be developed.
Signed-off-by: Brian Barrett <bbarrett@amazon.com>
2acc4b7e7f