Per MPI-3.1:8.7.1 p361:11-13, it's valid for MPI_FINALIZED to be
invoked during an attribute destruction callback (e.g., during the
destruction of keyvals on MPI_COMM_SELF during the very beginning of
MPI_FINALIZE). In such cases, MPI_FINALIZED must return "false".
Prior to this commit, we hung in FINALIZED if it were invoked during
a COMM_SELF attribute destruction callback in FINALIZE. See
https://github.com/open-mpi/ompi/issues/5084.
This commit converts the MPI_INITIALIZED / MPI_FINALIZED
infrastructure to use a single enum (ompi_mpi_state, set atomically)
to represent the state of MPI:
- not initialized
- init started
- init completed
- finalize started
- finalize past COMM_SELF destruction
- finalize completed
The "finalize past COMM_SELF destruction" state is what allows us to
return "false" from MPI_FINALIZED before COMM_SELF has been fully
destroyed / all attribute callbacks have been invoked.
Since this state is checked at nearly every MPI API call (to see if
we're outside of the INIT/FINALIZE epoch), care was taken to use
atomics to *set* the ompi_mpi_state value in ompi_mpi_init() and
ompi_mpi_finalize(), but performance-critical code paths can simply
read the variable without needing to use a slow call to an
opal_atomic_*() function.
Thanks to @AndrewGaspar for reporting the issue.
Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
35438ae9b5