Unit test mt_membar fails intermittently in Ubuntu 24.04

[markbrown314]

On kernel 6.8.0-53-generic

Using:
hpc/xpmem commit: 3bcab554
Sandia-OpenSHMEM/SOS commit: 767fe2a

Lock test unit/mt_membar fails if you do the following.

./autogen.sh
./configure --with-xpmem --enable-shr-atomics --enable-error-checking --enable-pmi-simple
make -j
make check TESTS= -j
cd modules/tests-sos/test/unit
while [ 1 ]; do mpirun -n 2 ./mt_membar; if [ "$?" != "0" ]; then break; fi; done
Starting multi-threaded test on 2 PEs, 2 threads/PE
Starting multi-threaded test on 2 PEs, 2 threads/PE
Starting multi-threaded test on 2 PEs, 2 threads/PE
...
ERROR in LOCK test from 0 : result = 97, expected = 200

Found in CI test: XPMEM_Only/transport_none

[markbrown314]

Reproduced with ofi as well (configuration --enable-pmi-simple --with-ofi)
Seems to happen less often in this configuration.