OpenMPI with MXM 32bit issue

We have the problem that after 2.147 billion messages, which is the range of an int32_t, we cannot receive any more messages.

Compiling OpenMPI with the flag "--with-mxm=/path/to/mxm" causes this problem while without this flag everything is fine. The Problem is reproducible with the attached example code, by compiling and running it with the follwing commands:

$ /path/to/openmpi/bin/mpic++ openmpi_mxm_freeze.cxx -o openmpi_mxm_freeze

$ /path/to/openmpi/bin/mpirun -np 2 openmpi_mxm_freeze

Maybe the issue is connected with the following lines from "mxm_def.h":

The problem occurs with the newest Mellanox firmware, OFED package and OpenMPI version.