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Subject: Re: [OMPI users] Segfault on any MPI communication on head node
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2011-09-27 07:28:35

Hmm. It's not immediately clear to me what's going wrong here.

I hate to ask, but could you install a debugging version of Open MPI and capture a proper stack trace of the segv?

Also, could you try the 1.4.4 rc and see if that magically fixes the problem? (I'm about to post a new 1.4.4 rc later this morning, but either the current one or the one from later today would be a good datapoint)

On Sep 26, 2011, at 5:09 PM, Phillip Vassenkov wrote:

> Yep, Fedora Core 14 and OpenMPI 1.4.3
> On 9/24/11 7:02 AM, Jeff Squyres wrote:
>> Are you running the same OS version and Open MPI version between the head node and regular nodes?
>> On Sep 23, 2011, at 5:27 PM, Vassenkov, Phillip wrote:
>>> Hey all,
>>> I’ve been racking my brains over this for several days and was hoping anyone could enlighten me. I’ll describe only the relevant parts of the network/computer systems. There is one head node and a multitude of regular nodes. The regular nodes are all identical to each other. If I run an mpi program from one of the regular nodes to any other regular nodes, everything works. If I include the head node in the hosts file, I get segfaults which I’ll paste below along with sample code. The machines are all networked via infiniband and Ethernet. The issue only arises when mpi communication occurs. By this I mean, MPi_Init might succeed but the segfault always occurs on MPI_Barrier or MPI_send/recv. I found a work around by disabling the openib btl and enforcing that communications go over infiniband(if I don’t force infiniband, it’ll go over Ethernet). This command works when the head node is included in the hosts file:
>>> mpirun --hostfile hostfile --mca btl ^openib --mca btl_tcp_if_include ib0 -np 2 ./b.out
>>> Sample Code:
>>> #include "mpi.h"
>>> #include<stdio.h>
>>> int main(int argc, char *argv[])
>>> {
>>> int rank, nprocs;
>>> char* name[20];
>>> int maxlen = 20;
>>> MPI_Init(&argc,&argv);
>>> MPI_Comm_size(MPI_COMM_WORLD,&nprocs);
>>> MPI_Comm_rank(MPI_COMM_WORLD,&rank);
>>> MPI_Barrier(MPI_COMM_WORLD);
>>> gethostname(name,maxlen);
>>> printf("Hello, world. I am %d of %d and host %s \n", rank, nprocs,name);
>>> fflush(stdout);
>>> MPI_Finalize();
>>> return 0;
>>> }
>>> Segfault:
>>> [pastec:19917] *** Process received signal ***
>>> [pastec:19917] Signal: Segmentation fault (11)
>>> [pastec:19917] Signal code: Address not mapped (1)
>>> [pastec:19917] Failing at address: 0x8
>>> [pastec:19917] [ 0] /lib64/ [0x34a880eeb0]
>>> [pastec:19917] [ 1] /usr/lib64/ [0x7eff6430b6aa]
>>> [pastec:19917] [ 2] /usr/lib64/openmpi/lib/openmpi/ [0x7eff66a163c9]
>>> [pastec:19917] [ 3] /usr/lib64/openmpi/lib/openmpi/ [0x7eff66a21b70]
>>> [pastec:19917] [ 4] /usr/lib64/openmpi/lib/openmpi/ [0x7eff66a21c89]
>>> [pastec:19917] [ 5] /usr/lib64/openmpi/lib/openmpi/ [0x7eff66a1703d]
>>> [pastec:19917] [ 6] /usr/lib64/openmpi/lib/openmpi/ [0x7eff676670e6]
>>> [pastec:19917] [ 7] /usr/lib64/openmpi/lib/openmpi/ [0x7eff6765b273]
>>> [pastec:19917] [ 8] /usr/lib64/openmpi/lib/openmpi/ [0x7eff65539b2f]
>>> [pastec:19917] [ 9] /usr/lib64/openmpi/lib/openmpi/ [0x7eff655425cf]
>>> [pastec:19917] [10] /usr/lib64/openmpi/lib/ [0x3a54c4c94e]
>>> [pastec:19917] [11] ./b.out(main+0x6e) [0x400a42]
>>> [pastec:19917] [12] /lib64/ [0x34a841ee5d]
>>> [pastec:19917] [13] ./b.out() [0x400919]
>>> [pastec:19917] *** End of error message ***
>>> [] [[18526,0],0]-[[18526,1],1] mca_oob_tcp_msg_recv: readv failed: Connection reset by peer (104)
>>> --------------------------------------------------------------------------
>>> mpirun noticed that process rank 1 with PID 19917 on node exited on signal 11 (Segmentation fault).
>>> --------------------------------------------------------------------------
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>>> users_at_[hidden]
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Jeff Squyres
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