[mpich-discuss] Spawned process hanging in MPI_Finalize

Mccall, Kurt E. (MSFC-EV41) kurt.e.mccall at nasa.gov
Tue Mar 2 18:54:12 CST 2021

I have a parent process that creates a child via MPI_Comm_spawn().     When the child decides it has to exit, it is hanging in MPI_Finalize().   It does the same if it calls MPI_Comm_disconnect() before MPI_Finalize.

Here is the stack trace in the child:

(gdb) where
#0  0x00007fc6f2fedde0 in __poll_nocancel () from /usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libc.so.6
#1  0x00007fc6f4dc840e in MPID_nem_tcp_connpoll () at src/mpid/ch3/channels/nemesis/netmod/tcp/socksm.c:1819
#2  0x00007fc6f4db857e in MPID_nem_network_poll () at src/mpid/ch3/channels/nemesis/src/mpid_nem_network_poll.c:16
#3  0x00007fc6f4dafc43 in MPIDI_CH3I_Progress () at src/mpid/ch3/channels/nemesis/src/ch3_progress.c:1019
#4  0x00007fc6f4d5094d in MPIDI_CH3U_VC_WaitForClose () at src/mpid/ch3/src/ch3u_handle_connection.c:383
#5  0x00007fc6f4d94efa in MPID_Finalize () at src/mpid/ch3/src/mpid_finalize.c:110
#6  0x00007fc6f4c432ca in PMPI_Finalize () at src/mpi/init/finalize.c:260
#7  0x0000000000408a85 in needles::MpiWorker::finalize () at src/MpiWorker.cpp:470

Maybe I have a communication that hasn't completed, or the child is waiting for the parent to call MPI_Finalize.   I believe that you (Ken, Hui) told me that it shouldn't do the latter.

Is there a way for the child to cleanly exit without hanging in MPI_Finalize?   I tried calling MPI_Cancel() in the child on the only possible communication request that I knew of, but it didn't help.
It just occurred to me that I haven't tried calling MPI_Cancel on the requests in the parent...

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