Disconnect() hangs with openmp3.1 / Python 3.8

Hello,

I keep failing at disconnecting spawned processes in a program that, otherwise, seems to work. The OS is canonical ubuntu 20.04.
I figured out the deb packaged mpi4py actually failed at runtests.py. I thus uninstalled and compiled latest master (70333ef76db05).

The compiled one passes the tests, but it still hangs on disconnect. I use for a testscript the code Lisandro posted in another thread. It is reproduced at the end of this message.

Any hint on how to workaround this?

Best regards

Bruno

export OMPI_MCA_rmaps_base_oversubscribe=yes
python3 test/runtests.py
Python 3.8 (/usr/bin/python3)
MPI 3.1 (Open MPI 4.0.3)
mpi4py 3.1.0a0 (build/lib.linux-x86_64-3.8/mpi4py)
--------------------------------------------------------------------------
The OSC pt2pt component does not support MPI_THREAD_MULTIPLE in this release.
Workarounds are to run on a single node, or to use a system with an RDMA
capable network such as Infiniband.
...

Ran 1239 tests in 53.792s

OK (skipped=186)

‌

python3 testDisonnect.py
Hello from: 0 over population of 3
Hello from: 2 over population of 3
Hello from: 1 over population of 3

_________

#!/usr/bin/python3
import sys
from mpi4py import MPI

def execute(nproc=6,**kwargs):
    comm_slave = MPI.COMM_SELF.Spawn(sys.executable, args=[__file__,"slave"], maxprocs=nproc-1)
    comm_world = comm_slave.Merge()
    common_job(comm_world)
    comm_world.Disconnect()
    comm_slave.Disconnect()

def slave_job():
    comm_slave = MPI.Comm.Get_parent()
    comm_world = comm_slave.Merge()
    common_job(comm_world)
    comm_world.Disconnect()
    comm_slave.Disconnect()

def common_job(comm):
    comm.Barrier()
    print("Hello from: {} over population of {}".format(comm.rank,comm.size))
    comm.Barrier()

if (__name__=="__main__"):
    if ("slave" in sys.argv):
        slave_job()
    else:
        execute()

‌

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