Hello,
It seems that a return value is not updated during the setup of
process affinity in function ompi_mpi_init()
ompi/runtime/ompi_mpi_init.c:459
The problem is in the following piece of code:
[... here ret == OPAL_SUCCESS ...]
phys_cpu = opal_paffinity_base_get_physical_processor_id(nrank);
if (0 > phys_cpu) {
error = "Could not get physical processor id - cannot set processor
affinity";
goto error;
}
[...]
If opal_paffinity_base_get_physical_processor_id() failed ret is not
updated and we will reach the "error:" label while ret == OPAL_SUCCESS.
As a result MPI_Init() will return without having initialized the
MPI_COMM_WORLD struct leading to a segmentation fault on calls like
MPI_Comm_size().
I got the bug recently with new westmere processors for which the
function opal_paffinity_base_get_physical_processor_id() failed if we
are using the mca parameter "opal_paffinity_alone 1" during the
execution.
I'm not sure that it's the right way to fix the problem but here is a
patch tested with v1.5. This patch allows to report the problem instead
of generating a segmentation fault.
With the patch, the output is:
--------------------------------------------------------------------------
It looks like MPI_INIT failed for some reason; your parallel process is
likely to abort. There are many reasons that a parallel process can
fail during MPI_INIT; some of which are due to configuration or environment
problems. This failure appears to be an internal failure; here's some
additional information (which may only be relevant to an Open MPI
developer):
Could not get physical processor id - cannot set processor affinity
--> Returned "Not found" (-5) instead of "Success" (0)
--------------------------------------------------------------------------
Without the patch, the output was:
*** Process received signal ***
Signal: Segmentation fault (11)
Signal code: Address not mapped (1)
Failing at address: 0x10
[ 0] /lib64/libpthread.so.0 [0x3d4e20ee90]
[ 1] /home_nfs/thouveng/dev/openmpi-v1.5/lib/libmpi.so.0(MPI_Comm_size+0x9c)
[0x7fce74468dfc]
[ 2] ./IMB-MPI1(IMB_init_pointers+0x2f) [0x40629f]
[ 3] ./IMB-MPI1(main+0x65) [0x4035c5]
[ 4] /lib64/libc.so.6(__libc_start_main+0xfd) [0x3d4da1ea2d]
[ 5] ./IMB-MPI1 [0x403499]
Regards,
Guillaume
---
diff --git a/ompi/runtime/ompi_mpi_init.c b/ompi/runtime/ompi_mpi_init.c
--- a/ompi/runtime/ompi_mpi_init.c
+++ b/ompi/runtime/ompi_mpi_init.c
@@ -459,6 +459,7 @@ int ompi_mpi_init(int argc, char **argv,
OPAL_PAFFINITY_CPU_ZERO(mask);
phys_cpu =
opal_paffinity_base_get_physical_processor_id(nrank);
if (0 > phys_cpu) {
+ ret = phys_cpu;
error = "Could not get physical processor id - cannot set
processor affinity";
goto error;
}
