Devendar literally just reproduced here at the developer meeting, too.
Sweet -- ok, so we understand what is going on.
Devendar/Mellanox is going to talk about this internally and get back to us.
> On Jun 25, 2015, at 2:59 PM, Gilles Gouaillardet
> <gilles.gouaillar...@gmail.com> wrote:
>
> Jeff,
>
> this is exactly what happens.
>
> I will send a stack trace later
>
> Cheers,
>
> Gilles
>
> On Thursday, June 25, 2015, Jeff Squyres (jsquyres) <jsquy...@cisco.com>
> wrote:
> Gilles --
>
> Can you send a stack trace from one of these crashes?
>
> I am *guessing* that the following is happening:
>
> 1. coll selection begins
> 2. coll ml is queried, and disqualifies itself (but is not dlclosed yet)
> 3. coll hcol is queried, which ends up calling down into libhcol. libhcol
> calls a coll_ml_* symbol (which is apparently in a different .o file in the
> library), but the linker has already resolved that coll_ml_* symbol in the
> coll ml DSO. So the execution transfers back up into the coll ml DSO, and
> ... kaboom.
>
> A simple stack trace will confirm this -- it should show execution going down
> into libhcol and then back up into coll ml.
>
>
>
>
> > On Jun 25, 2015, at 1:03 AM, Gilles Gouaillardet <gil...@rist.or.jp> wrote:
> >
> > Folks,
> >
> > this is a followup on an issue reported by Daniel on the users mailing list
> > :
> > OpenMPI is built with hcoll from Mellanox.
> > the coll ml module has default priority zero.
> >
> > on my cluster, it works just fine
> > on Daniel's cluster, it crashes.
> >
> > i was able to reproduce the crash by tweaking mca_base_component_path and
> > ensure
> > the coll ml module is loaded first.
> >
> > basically, i found two issues :
> > 1) libhcoll.so (vendor lib provided by Mellanox, i tested
> > hpcx-v1.3.336-gcc-OFED-1.5.4.1-redhat6.2-x86_64) seems to include its own
> > coll ml, since there are some *public* symbols that are common to this
> > module (ml_open, ml_coll_hier_barrier_setup, ...)
> > 2) coll ml priority is zero, and even if the library is dlclose'd, it seems
> > this is uneffective
> > (nothing changed in /proc/xxx/maps before and after dlclose)
> >
> >
> > there are two workarounds :
> > mpirun --mca coll ^ml
> > or
> > mpirun --mca coll ^hcoll ... (probably not what is needed though ...)
> >
> > is it expected the library is not unloaded after dlclose ?
> >
> > Mellanox folks,
> > can you please double check how libhcoll is built ?
> > i guess it would work if the ml_ symbols were private to the library.
> > if not, the only workaround is to mpirun --mca coll ^ml
> > otherwise, it might crash (if coll_ml is loaded before coll_hcoll, which is
> > really system dependent)
> >
> > Cheers,
> >
> > Gilles
> > On 6/25/2015 10:46 AM, Gilles Gouaillardet wrote:
> >> Daniel,
> >>
> >> thanks for the logs.
> >>
> >> an other workaround is to
> >> mpirun --mca coll ^hcoll ...
> >>
> >> i was able to reproduce the issue, and it surprisingly occurs only if the
> >> coll_ml module is loaded *before* the hcoll module.
> >> /* this is not the case on my system, so i had to hack my
> >> mca_base_component_path in order to reproduce the issue */
> >>
> >> as far as i understand, libhcoll is a proprietary software, so i cannot
> >> dig into it.
> >> that being said, i noticed libhcoll defines some symbols (such as
> >> ml_coll_hier_barrier_setup) that are also defined by the coll_ml module,
> >> so it is likely hcoll coll_ml and openmpi coll_ml are not binary
> >> compatible hence the error.
> >>
> >> i will dig a bit more and see if this is even supposed to happen (since
> >> coll_ml_priority is zero, why is the module still loaded ?)
> >>
> >> as far as i am concerned, you *have to* mpirun --mca coll ^ml or update
> >> your user/system wide config file to blacklist the coll_ml module to
> >> ensure this is working.
> >>
> >> Mike and Mellanox folks, could you please comment on that ?
> >>
> >> Cheers,
> >>
> >> Gilles
> >>
> >>
> >>
> >> On 6/24/2015 5:23 PM, Daniel Letai wrote:
> >>> Gilles,
> >>>
> >>> Attached the two output logs.
> >>>
> >>> Thanks,
> >>> Daniel
> >>>
> >>> On 06/22/2015 08:08 AM, Gilles Gouaillardet wrote:
> >>>> Daniel,
> >>>>
> >>>> i double checked this and i cannot make any sense with these logs.
> >>>>
> >>>> if coll_ml_priority is zero, then i do not any way how
> >>>> ml_coll_hier_barrier_setup can be invoked.
> >>>>
> >>>> could you please run again with --mca coll_base_verbose 100
> >>>> with and without --mca coll ^ml
> >>>>
> >>>> Cheers,
> >>>>
> >>>> Gilles
> >>>>
> >>>> On 6/22/2015 12:08 AM, Gilles Gouaillardet wrote:
> >>>>> Daniel,
> >>>>>
> >>>>> ok, thanks
> >>>>>
> >>>>> it seems that even if priority is zero, some code gets executed
> >>>>> I will confirm this tomorrow and send you a patch to work around the
> >>>>> issue if that if my guess is proven right
> >>>>>
> >>>>> Cheers,
> >>>>>
> >>>>> Gilles
> >>>>>
> >>>>> On Sunday, June 21, 2015, Daniel Letai <d...@letai.org.il> wrote:
> >>>>> MCA coll: parameter "coll_ml_priority" (current value: "0", data
> >>>>> source: default, level: 9 dev/all, type: int)
> >>>>>
> >>>>> Not sure how to read this, but for any n>1 mpirun only works with --mca
> >>>>> coll ^ml
> >>>>>
> >>>>> Thanks for helping
> >>>>>
> >>>>> On 06/18/2015 04:36 PM, Gilles Gouaillardet wrote:
> >>>>>> This is really odd...
> >>>>>>
> >>>>>> you can run
> >>>>>> ompi_info --all
> >>>>>> and search coll_ml_priority
> >>>>>>
> >>>>>> it will display the current value and the origin
> >>>>>> (e.g. default, system wide config, user config, cli, environment
> >>>>>> variable)
> >>>>>>
> >>>>>> Cheers,
> >>>>>>
> >>>>>> Gilles
> >>>>>>
> >>>>>> On Thursday, June 18, 2015, Daniel Letai <d...@letai.org.il> wrote:
> >>>>>> No, that's the issue.
> >>>>>> I had to disable it to get things working.
> >>>>>>
> >>>>>> That's why I included my config settings - I couldn't figure out which
> >>>>>> option enabled it, so I could remove it from the configuration...
> >>>>>>
> >>>>>> On 06/18/2015 02:43 PM, Gilles Gouaillardet wrote:
> >>>>>>> Daniel,
> >>>>>>>
> >>>>>>> ML module is not ready for production and is disabled by default.
> >>>>>>>
> >>>>>>> Did you explicitly enable this module ?
> >>>>>>> If yes, I encourage you to disable it
> >>>>>>>
> >>>>>>> Cheers,
> >>>>>>>
> >>>>>>> Gilles
> >>>>>>>
> >>>>>>> On Thursday, June 18, 2015, Daniel Letai <d...@letai.org.il> wrote:
> >>>>>>> given a simple hello.c:
> >>>>>>>
> >>>>>>> #include <stdio.h>
> >>>>>>> #include <mpi.h>
> >>>>>>>
> >>>>>>> int main(int argc, char* argv[])
> >>>>>>> {
> >>>>>>> int size, rank, len;
> >>>>>>> char name[MPI_MAX_PROCESSOR_NAME];
> >>>>>>>
> >>>>>>> MPI_Init(&argc, &argv);
> >>>>>>> MPI_Comm_size(MPI_COMM_WORLD, &size);
> >>>>>>> MPI_Comm_rank(MPI_COMM_WORLD, &rank);
> >>>>>>> MPI_Get_processor_name(name, &len);
> >>>>>>>
> >>>>>>> printf("%s: Process %d out of %d\n", name, rank, size);
> >>>>>>>
> >>>>>>> MPI_Finalize();ffff
> >>>>>>> }
> >>>>>>>
> >>>>>>> for n=1
> >>>>>>> mpirun -n 1 ./hello
> >>>>>>> it works correctly.
> >>>>>>>
> >>>>>>> for n>1 it segfaults with signal 11
> >>>>>>> used gdb to trace the problem to ml coll:
> >>>>>>>
> >>>>>>> Program received signal SIGSEGV, Segmentation fault.
> >>>>>>> 0x00007ffff6750845 in ml_coll_hier_barrier_setup()
> >>>>>>> from <path to openmpi 1.8.5>/lib/openmpi/mca_coll_ml.so
> >>>>>>>
> >>>>>>> running with
> >>>>>>> mpirun -n 2 --mca coll ^ml ./hello
> >>>>>>> works correctly
> >>>>>>>
> >>>>>>> using mellanox ofed 2.3-2.0.5-rhel6.4-x86_64, if it's at all relevant.
> >>>>>>> openmpi 1.8.5 was built with following options:
> >>>>>>> rpmbuild --rebuild --define 'configure_options --with-verbs=/usr
> >>>>>>> --with-verbs-libdir=/usr/lib64 CC=gcc
> >>>>>>> CXX=g++ FC=gfortran CFLAGS="-g -O3" --enable-mpirun-prefix-by-default
> >>>>>>> --enable-orterun-prefix-by-default --disable-debug
> >>>>>>> --with-knem=/opt/knem-1.1.1.90mlnx --with-platform=optimized
> >>>>>>> --without-mpi-param-check
> >>>>>>> --with-contrib-vt-flags=--disable-iotrace --enable-builtin-atomics
> >>>>>>> --enable-cxx-exceptions --enable-sparse-groups
> >>>>>>> --enable-mpi-thread-multiple --enable-memchecker
> >>>>>>> --enable-btl-openib-failover --with-hwloc=internal --with-verbs
> >>>>>>> --with-x --with-slurm --with-pmi=/opt/slurm
> >>>>>>> --with-fca=/opt/mellanox/fca --with-mxm=/opt/mellanox/mxm
> >>>>>>> --with-hcoll=/opt/mellanox/hcoll' openmpi-1.8.5-1.src.rpm
> >>>>>>>
> >>>>>>> gcc version 5.1.1
> >>>>>>>
> >>>>>>> Thanks in advance
> >>>>>>> _______________________________________________
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> >>>>>>> Link to this post:
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> >>>>>>>
> >>>>>>>
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> >>>>>>
> >>>>>>
> >>>>>>
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> >>>>>
> >>>>>
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> >>
> >>
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>
> --
> Jeff Squyres
> jsquy...@cisco.com
> For corporate legal information go to:
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jsquy...@cisco.com
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