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Subject: Re: [OMPI devel] Segmentation fault on x86_64 on heterogeneous environment
From: Timur Magomedov (timur.magomedov_at_[hidden])
Date: 2010-04-23 03:43:37


Thank you, George!
I checked out trunk version 1.7a1r23028 and got the same errors as on
1.4.*. Then I applied your patch, fixed one more file

Index: pml_ob1_recvreq.c
===================================================================
--- pml_ob1_recvreq.c (revision 23028)
+++ pml_ob1_recvreq.c (working copy)
@@ -331,7 +331,7 @@
 
     mca_pml_ob1_send_fin(recvreq->req_recv.req_base.req_proc,
                          bml_btl,
- frag->rdma_hdr.hdr_rget.hdr_des.pval,
+ frag->rdma_hdr.hdr_rget.hdr_des,
                          des->order, 0);
 
     /* is receive request complete */

and the problem disappeared.

В Птн, 23/04/2010 в 01:38 -0400, George Bosilca пишет:
> Timur,
>
> Thanks for the very detailed analysis of the problem. Based on your observations, I was able to track down the issue pretty quickly. In few words, the 64 bits machine sent a pointer to the 32 bits one, and expected that it will get it back untouched. Unfortunately, on the 32 bits machine this pointer was translated into a void* and the upper 32 bits were lost.
>
> I don't have a heterogeneous environment available right away to test my patch. I would really appreciate it if you can test it and let us know if it solve this problem.
>
> Thanks,
> george.
>
> PS: In order to apply it, please go in the ompi/mca/pml/ob1 directory and do the "patch -p0" from there.
>
> On Apr 22, 2010, at 09:08 , Timur Magomedov wrote:
>
> > Hello, list.
> >
> > I have a strange segmentation fault on x86_64 machine running together
> > with x86.
> > I am running attached program that sends some bytes from process 0 to
> > process 1. My configuration is:
> > Machine #1: (process 0)
> > arch: x86
> > hostname: magomedov-desktop
> > linux distro: Ubuntu 9.10
> > Open MPI: v1.4 configured with --enable-heterogeneous --enable-debug
> > Machine #2: (process 1)
> > arch: x86_64
> > hostname: linuxtche
> > linux distro: Fedora 12
> > Open MPI: v1.4 configured with --enable-heterogeneous
> > --prefix=/home/magomedov/openmpi/ --enable-debug
> >
> > They are connected by ethernet.
> > My user environment on second (x86_64) machine is set up to use Open MPI
> > from /home/magomedov/openmpi/.
> >
> > Then I compile attached program on both machines (at the same path) and
> > run it. Process 0 from x86 machine should send data to process 1 on
> > x86_64 machine.
> >
> > First, let's send 65530 bytes:
> >
> > mpirun -host timur,linuxtche -np
> > 2 /home/magomedov/workspace/mpi-test/mpi-send-test 65530
> > magomedov_at_linuxtche's password:
> > *** processor magomedov-desktop, comm size is 2, my rank is 0, pid 21875
> > ***
> > *** processor linuxtche, comm size is 2, my rank is 1, pid 11357 ***
> > Received 65530 bytes
> >
> > It's OK. Then let's send 65537 bytes:
> >
> > magomedov_at_magomedov-desktop:~/workspace/mpi-test$ mpirun -host
> > timur,linuxtche -np 2 /home/magomedov/workspace/mpi-test/mpi-send-test
> > 65537
> > magomedov_at_linuxtche's password:
> > *** processor magomedov-desktop, comm size is 2, my rank is 0, pid 9205
> > ***
> > *** processor linuxtche, comm size is 2, my rank is 1, pid 28858 ***
> > [linuxtche:28858] *** Process received signal ***
> > [linuxtche:28858] Signal: Segmentation fault (11)
> > [linuxtche:28858] Signal code: Address not mapped (1)
> > [linuxtche:28858] Failing at address: 0x201143bf8
> > [linuxtche:28858] [ 0] /lib64/libpthread.so.0() [0x3600c0f0f0]
> > [linuxtche:28858]
> > [ 1] /home/magomedov/openmpi/lib/openmpi/mca_pml_ob1.so(+0xfc27)
> > [0x7f5e94076c27]
> > [linuxtche:28858]
> > [ 2] /home/magomedov/openmpi/lib/openmpi/mca_btl_tcp.so(+0xadac)
> > [0x7f5e935c3dac]
> > [linuxtche:28858]
> > [ 3] /home/magomedov/openmpi/lib/libopen-pal.so.0(+0x27611)
> > [0x7f5e96575611]
> > [linuxtche:28858]
> > [ 4] /home/magomedov/openmpi/lib/libopen-pal.so.0(+0x27c57)
> > [0x7f5e96575c57]
> > [linuxtche:28858]
> > [ 5] /home/magomedov/openmpi/lib/libopen-pal.so.0(opal_event_loop+0x1f)
> > [0x7f5e96575848]
> > [linuxtche:28858]
> > [ 6] /home/magomedov/openmpi/lib/libopen-pal.so.0(opal_progress+0x89)
> > [0x7f5e965648dd]
> > [linuxtche:28858]
> > [ 7] /home/magomedov/openmpi/lib/openmpi/mca_pml_ob1.so(+0x762f)
> > [0x7f5e9406e62f]
> > [linuxtche:28858]
> > [ 8] /home/magomedov/openmpi/lib/openmpi/mca_pml_ob1.so(+0x777d)
> > [0x7f5e9406e77d]
> > [linuxtche:28858]
> > [ 9] /home/magomedov/openmpi/lib/openmpi/mca_pml_ob1.so(+0x8246)
> > [0x7f5e9406f246]
> > [linuxtche:28858] [10] /home/magomedov/openmpi/lib/libmpi.so.0(MPI_Recv
> > +0x2d2) [0x7f5e96af832c]
> > [linuxtche:28858]
> > [11] /home/magomedov/workspace/mpi-test/mpi-send-test(main+0x1e4)
> > [0x400ee8]
> > [linuxtche:28858] [12] /lib64/libc.so.6(__libc_start_main+0xfd)
> > [0x360001eb1d]
> > [linuxtche:28858]
> > [13] /home/magomedov/workspace/mpi-test/mpi-send-test() [0x400c49]
> > [linuxtche:28858] *** End of error message ***
> > --------------------------------------------------------------------------
> > mpirun noticed that process rank 1 with PID 28858 on node linuxtche
> > exited on signal 11 (Segmentation fault).
> > --------------------------------------------------------------------------
> >
> > If I am trying to send >= 65537 bytes from x86 I always get segfault on
> > x86_64.
> >
> > I made some investigations and found that "bad" pointer always has a
> > valid pointer actually in it's lower 32-bit word and "2" or "1" in it's
> > upper word. Program segfaults in pml_ob1_recvfrag.c, in function
> > mca_pml_ob1_recv_frag_callback_fin(), rdma pointer is broken. I inserted
> > rdma = (mca_btl_base_descriptor_t*)((unsigned long)rdma & 0xFFFFFFFF);
> > line which I believe truncates 64-bit pointer to 32 bits and segfaults
> > disappeared. However, this is not the solution.
> >
> > After some investigations with gdb it seems to me like this pointer was
> > sent to x86 machine and was received from it broken but I don't realize
> > what is going on enough to fix it...
> >
> > Can anyone reproduce it?
> > I got the same results on openmpi-1.4.2rc1 too.
> >
> > It looks like the same problem was described here
> > http://www.open-mpi.org/community/lists/users/2010/02/12182.php in
> > ompi-users list.
> >
> > --
> > Kind regards,
> > Timur Magomedov
> > Senior C++ Developer
> > DevelopOnBox LLC / Zodiac Interactive
> > http://www.zodiac.tv/
> > <mpi-send-test.c>_______________________________________________
> > devel mailing list
> > devel_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/devel
>

-- 
Kind regards,
Timur Magomedov
Senior C++ Developer
DevelopOnBox LLC / Zodiac Interactive
http://www.zodiac.tv/