Hi,

I have a specific issue that arises with MPICH (I use 3.1.1 built with

gcc) + MPI_THREAD_MULTIPLE + per-object critical sections on BG/Q.

A deadlock happens in the attached hybrid MPI+OpenMP example code with
2 

processes and more than one thread per process.

Debugging shows that one process is stuck in MPI_Allreduce while the 

other is blocked in MPI_Finalize.

A similar communication pattern happens in my application, but in this

case both processes are stuck in MPI_Allreduce.

Note that the problem disappears when removing MPI_Allreduce, or 

avoiding request cancellation (cancel+wait+test_cancelled). Both 

Allreduce and cancellation operations can be avoided in this test while

ensuring a correct result. But in my application, both operations are 

necessary.

In addition, using a global critical section (default) results in a 

correct execution.

My configure line is as follows:

./configure --prefix=/home/aamer/usr --host=powerpc64-bgq-linux 

--with-device=pamid --with-file-system=gpfs:BGQ 

--with-file-system=bg+bglockless --with-atomic-primitives 

--enable-handle-allocation=tls --enable-refcount=lock-free 

-disable-predefined-refcount --disable-error-checking --without-timing

--without-mpit-pvars --enable-fast=O3,ndebug --enable-thread-cs=per-object

I appreciate any advice to solve this issue?

Regards,

--Halim

[attachment "allred_cancel.c" deleted by Michael Blocksome/Rochester/IBM]
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