I'm working on getting a build of mpich-4.1.2 ready to replace our old build of mpich-3.3.2. With older MPICH releases, we used the "nemesis" channel via ch3 to provide support for shared-memory configurations as well as TCP/IP. In ch4, I thought the nearest equivalent would be: --with-device=ch4:ofi:tcp,shm The "tcp" portion of this seems to work just fine, but "shm" hangs during (I think) MPI_Finalize, requiring a CTRL-C to kill it. For example, in the build area, $ ./src/pm/hydra/mpiexec.hydra -n 2 ./examples/cpi Process 0 of 2 is on uk-eellis-l Process 1 of 2 is on uk-eellis-l pi is approximately 3.1415926544231318, Error is 0.0000000008333387 wall clock time = 0.000019 ^C[mpiexec@uk-eellis-l] Sending Ctrl-C to processes as requested [mpiexec@uk-eellis-l] Press Ctrl-C again to force abort =================================================================================== = BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES = PID 829015 RUNNING AT uk-eellis-l = EXIT CODE: 2 = CLEANING UP REMAINING PROCESSES = YOU CAN IGNORE THE BELOW CLEANUP MESSAGES =================================================================================== YOUR APPLICATION TERMINATED WITH THE EXIT STRING: Interrupt (signal 2) This typically refers to a problem with your application. Please see the FAQ page for debugging suggestions Things work fine if I force FI_PROVIDER=tcp. Am I missing something? Here's the configure line I'm using: $ ./configure --prefix <prefix> --with-device=ch4:ofi:tcp,shm --enable-shared --with-libfabric=embedded --enable-fortran --enable-efa=no This is running on a Debian 11 system, gcc 10.3.0. Cheers, Edric.