Hello,
Sorry, I forgot the attached test case in my previous message... :(
Best regards,
Yvan Fournier
----- Mail transferred -----
From: "yvan fournier" <yvan.fourn...@free.fr>
To: users@lists.open-mpi.org
Sent: Sunday January 7 2018 01:43:16
Object: False positives with OpenMPI and memchecker
Hello,
I obtain false positives with OpenMPI when memcheck is enabled, using OpenMPI
3.0.0
This is similar to an issue I had reported and had been fixed in Nov. 2016, but
affects MPI_Isend/MPI_Irecv instead of MPI_Send/MPI_Recv.
I had not done much additional testing on my application using memchecker
since, so probably may have missed remaining issues at the time.
In the attached test (which has 2 optional variants relating to whether the
send and receive buffers are allocated on the stack or heap, but exhibit the
same basic issue), I have (running "mpicc vg_ompi_isend_irecv.c && -g mpiexec
-n 2 ./a.out"):
==19651== Memcheck, a memory error detector
==19651== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==19651== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==19651== Command: ./a.out
==19651==
==19650== Thread 3:
==19650== Syscall param epoll_pwait(sigmask) points to unaddressable byte(s)
==19650== at 0x5470596: epoll_pwait (in /usr/lib/libc-2.26.so)
==19650== by 0x5A5A9FA: epoll_dispatch (epoll.c:407)
==19650== by 0x5A5EA9A: opal_libevent2022_event_base_loop (event.c:1630)
==19650== by 0x94C96ED: progress_engine (in
/home/yvan/opt/openmpi-3.0/lib/openmpi/mca_pmix_pmix2x.so)
==19650== by 0x5163089: start_thread (in /usr/lib/libpthread-2.26.so)
==19650== by 0x547042E: clone (in /usr/lib/libc-2.26.so)
==19650== Address 0x0 is not stack'd, malloc'd or (recently) free'd
==19650==
==19651== Thread 3:
==19651== Syscall param epoll_pwait(sigmask) points to unaddressable byte(s)
==19651== at 0x5470596: epoll_pwait (in /usr/lib/libc-2.26.so)
==19651== by 0x5A5A9FA: epoll_dispatch (epoll.c:407)
==19651== by 0x5A5EA9A: opal_libevent2022_event_base_loop (event.c:1630)
==19651== by 0x94C96ED: progress_engine (in
/home/yvan/opt/openmpi-3.0/lib/openmpi/mca_pmix_pmix2x.so)
==19651== by 0x5163089: start_thread (in /usr/lib/libpthread-2.26.so)
==19651== by 0x547042E: clone (in /usr/lib/libc-2.26.so)
==19651== Address 0x0 is not stack'd, malloc'd or (recently) free'd
==19651==
==19650== Thread 1:
==19650== Invalid read of size 2
==19650== at 0x4C33BA0: memmove (in
/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==19650== by 0x5A27C85: opal_convertor_pack (in
/home/yvan/opt/openmpi-3.0/lib/libopen-pal.so.40.0.0)
==19650== by 0xD177EF1: mca_btl_vader_sendi (in
/home/yvan/opt/openmpi-3.0/lib/openmpi/mca_btl_vader.so)
==19650== by 0xE1A7F31: mca_pml_ob1_send_inline.constprop.4 (in
/home/yvan/opt/openmpi-3.0/lib/openmpi/mca_pml_ob1.so)
==19650== by 0xE1A8711: mca_pml_ob1_isend (in
/home/yvan/opt/openmpi-3.0/lib/openmpi/mca_pml_ob1.so)
==19650== by 0x4EB4C83: PMPI_Isend (in
/home/yvan/opt/openmpi-3.0/lib/libmpi.so.40.0.0)
==19650== by 0x108B24: main (vg_ompi_isend_irecv.c:63)
==19650== Address 0x1ffefffcc4 is on thread 1's stack
==19650== in frame #6, created by main (vg_ompi_isend_irecv.c:7)
The first 2 warnings seem to relate to initialization, so are not a big issue,
but the last one occurs whenever I use MPI_Isend, so they are a more important
issue.
Using a version built without --enable-memchecker, I also have the two
initialization warnings, but not the warning from MPI_Isend...
Best regards,
Yvan Fournier
#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
int main(int argc, char *argv[])
{
MPI_Request request[2];
MPI_Status status[2];
int l = 5, l_prev = 0;
int rank_next = MPI_PROC_NULL, rank_prev = MPI_PROC_NULL;
int rank_id = 0, n_ranks = 1, tag = 1;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &rank_id);
MPI_Comm_size(MPI_COMM_WORLD, &n_ranks);
if (rank_id > 0)
rank_prev = rank_id -1;
if (rank_id + 1 < n_ranks)
rank_next = rank_id + 1;
#if defined(VARIANT_1)
int sendbuf[1] = {l};
int recvbuf[1] = {0};
if (rank_id %2 == 0) {
MPI_Isend(sendbuf, 1, MPI_INT, rank_next, tag, MPI_COMM_WORLD, &(request[0]));
MPI_Irecv(recvbuf, 1, MPI_INT, rank_prev, tag, MPI_COMM_WORLD, &(request[1]));
}
else {
MPI_Irecv(recvbuf, 1, MPI_INT, rank_prev, tag, MPI_COMM_WORLD, &(request[0]));
MPI_Isend(sendbuf, 1, MPI_INT, rank_next, tag, MPI_COMM_WORLD, &(request[1]));
}
MPI_Waitall(2, request, status);
l_prev = recvbuf[0];
#elif defined(VARIANT_2)
int *sendbuf = malloc(sizeof(int));
int *recvbuf = malloc(sizeof(int));
sendbuf[0] = l;
if (rank_id %2 == 0) {
MPI_Isend(sendbuf, 1, MPI_INT, rank_next, tag, MPI_COMM_WORLD, &(request[0]));
MPI_Irecv(recvbuf, 1, MPI_INT, rank_prev, tag, MPI_COMM_WORLD, &(request[1]));
}
else {
MPI_Irecv(recvbuf, 1, MPI_INT, rank_prev, tag, MPI_COMM_WORLD, &(request[0]));
MPI_Isend(sendbuf, 1, MPI_INT, rank_next, tag, MPI_COMM_WORLD, &(request[1]));
}
MPI_Waitall(2, request, status);
l_prev = recvbuf[0];
#else
if (rank_id %2 == 0) {
MPI_Isend(&l, 1, MPI_INT, rank_next, tag, MPI_COMM_WORLD, &(request[0]));
MPI_Irecv(&l_prev, 1, MPI_INT, rank_prev, tag, MPI_COMM_WORLD, &(request[1]));
}
else {
MPI_Irecv(&l_prev, 1, MPI_INT, rank_prev, tag, MPI_COMM_WORLD, &(request[0]));
MPI_Isend(&l, 1, MPI_INT, rank_next, tag, MPI_COMM_WORLD, &(request[1]));
}
MPI_Waitall(2, request, status);
#endif
printf("r%d, l=%d\n");
MPI_Finalize();
exit(0);
}
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