I wrote a new communication layer that we are evaluating for use in mesh management and PDE solvers, but it is based on MPI-2 one-sided operations (and will eventually benefit from some of the MPI-3 one-sided proposals, especially MPI_Fetch_and_op() and dynamic windows). All the basic functionality works well with MPICH2, but I have run into some Open MPI bugs regarding one-sided operations with composite data types. This email provides a reduced test case for two such bugs. I see that there are also some existing serious-looking bug reports regarding one-sided operations, but they are getting pretty old now and haven't seen action in a while.
https://svn.open-mpi.org/trac/ompi/ticket/2656 https://svn.open-mpi.org/trac/ompi/ticket/1905 Is there a plan for resolving these in the near future? Is anyone using Open MPI for serious work with one-sided operations? Bugs I am reporting: *1.* If an MPI_Win is used with an MPI_Datatype, even if the MPI_Win operation has completed, I get an invalid free when MPI_Type_free() is called before MPI_Win_free(). Since MPI_Type_free() is only supposed to mark the datatype for deletion, the implementation should properly manage reference counting. If you run the attached code with $ mpiexec -n 2 ./a.out 1 (which only does part of the comm described for the second bug, below), you can see the invalid free on rank 1 with stack still in MPI_Win_fence() (gdb) bt #0 0x00007ffff7288905 in raise () from /lib/libc.so.6 #1 0x00007ffff7289d7b in abort () from /lib/libc.so.6 #2 0x00007ffff72c147e in __libc_message () from /lib/libc.so.6 #3 0x00007ffff72c7396 in malloc_printerr () from /lib/libc.so.6 #4 0x00007ffff72cb26c in free () from /lib/libc.so.6 #5 0x00007ffff7a5aaa8 in ompi_datatype_release_args (pData=0x845010) at ompi_datatype_args.c:414 #6 0x00007ffff7a5b0ea in __ompi_datatype_release (datatype=0x845010) at ompi_datatype_create.c:47 #7 0x00007ffff218e772 in opal_obj_run_destructors (object=0x845010) at ../../../../opal/class/opal_object.h:448 #8 ompi_osc_rdma_replyreq_free (replyreq=0x680a80) at osc_rdma_replyreq.h:136 #9 ompi_osc_rdma_replyreq_send_cb (btl=0x7ffff3680ce0, endpoint=<optimized out>, descriptor=0x837b00, status=<optimized out>) at osc_rdma_data_move.c:691 #10 0x00007ffff347f38f in mca_btl_sm_component_progress () at btl_sm_component.c:645 #11 0x00007ffff7b1f80a in opal_progress () at runtime/opal_progress.c:207 #12 0x00007ffff21977c5 in opal_condition_wait (m=<optimized out>, c=0x842ee0) at ../../../../opal/threads/condition.h:99 #13 ompi_osc_rdma_module_fence (assert=0, win=0x842270) at osc_rdma_sync.c:207 #14 0x00007ffff7a89db5 in PMPI_Win_fence (assert=0, win=0x842270) at pwin_fence.c:60 #15 0x00000000004010d8 in main (argc=2, argv=0x7fffffffd508) at win.c:60 meanwhile, rank 0 has already freed the datatype and is waiting in MPI_Win_free(). (gdb) bt #0 0x00007ffff7312107 in sched_yield () from /lib/libc.so.6 #1 0x00007ffff7b1f82b in opal_progress () at runtime/opal_progress.c:220 #2 0x00007ffff7a53fe4 in opal_condition_wait (m=<optimized out>, c=<optimized out>) at ../opal/threads/condition.h:99 #3 ompi_request_default_wait_all (count=2, requests=0x7fffffffd210, statuses=0x7fffffffd1e0) at request/req_wait.c:263 #4 0x00007ffff25b8d71 in ompi_coll_tuned_sendrecv_actual (sendbuf=0x0, scount=0, sdatatype=0x7ffff7dba840, dest=1, stag=-16, recvbuf=<optimized out>, rcount=0, rdatatype=0x7ffff7dba840, source=1, rtag=-16, comm=0x8431a0, status=0x0) at coll_tuned_util.c:54 #5 0x00007ffff25c2de2 in ompi_coll_tuned_barrier_intra_two_procs (comm=<optimized out>, module=<optimized out>) at coll_tuned_barrier.c:256 #6 0x00007ffff25b92ab in ompi_coll_tuned_barrier_intra_dec_fixed (comm=0x8431a0, module=0x844980) at coll_tuned_decision_fixed.c:190 #7 0x00007ffff2186248 in ompi_osc_rdma_module_free (win=0x842170) at osc_rdma.c:46 #8 0x00007ffff7a58a44 in ompi_win_free (win=0x842170) at win/win.c:150 #9 0x00007ffff7a8a0dd in PMPI_Win_free (win=0x7fffffffd408) at pwin_free.c:56 #10 0x0000000000401195 in main (argc=2, argv=0x7fffffffd508) at win.c:69 *2.* This appears to be more fundamental and perhaps much harder to fix. The attached code sets up the following graph rank 0: 0 -> (1,0) 1 -> nothing 2 -> (1,1) rank 1: 0 -> (0,0) 1 -> (0,2) 2 -> (0,1) We pull over this graph using two calls to MPI_Get(), each with composite data types defining what to pull into the first two slots, and what to put into the third slot. It is Valgrind-clean with MPICH2, and produces the following: $ mpiexec.hydra -n 2 ./a.out 2 [0] provided [100,101,102] got [200, -2,201] [1] provided [200,201,202] got [100,102,101] With Open MPI, I see a.out: malloc.c:3096: sYSMALLOc: Assertion `(old_top == (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) >= (unsigned long)((((__builtin_offsetof (struct malloc_chunk, fd_nextsize))+((2 * (sizeof(size_t))) - 1)) & ~((2 * (sizeof(size_t))) - 1))) && ((old_top)->size & 0x1) && ((unsigned long)old_end & pagemask) == 0)' failed. on both ranks, with rank 0 at (gdb) bt #0 0x00007ffff7288905 in raise () from /lib/libc.so.6 #1 0x00007ffff7289d7b in abort () from /lib/libc.so.6 #2 0x00007ffff72c675d in __malloc_assert () from /lib/libc.so.6 #3 0x00007ffff72c96d3 in _int_malloc () from /lib/libc.so.6 #4 0x00007ffff72cad5d in malloc () from /lib/libc.so.6 #5 0x00007ffff7b46c46 in opal_free_list_grow (flist=0x7ffff239f150, num_elements=1) at class/opal_free_list.c:93 #6 0x00007ffff2196152 in ompi_osc_rdma_replyreq_alloc (replyreq=0x7fffffffd0f8, origin_rank=1, module=0x842d10) at osc_rdma_replyreq.h:82 #7 ompi_osc_rdma_replyreq_alloc_init (module=0x842d10, origin=1, origin_request=..., target_displacement=0, target_count=1, datatype=0x8455b0, replyreq=0x7fffffffd0f8) at osc_rdma_replyreq.c:40 #8 0x00007ffff218c051 in component_fragment_cb (btl=0x7ffff3680ce0, tag=<optimized out>, descriptor=<optimized out>, cbdata=<optimized out>) at osc_rdma_component.c:633 #9 0x00007ffff347f25f in mca_btl_sm_component_progress () at btl_sm_component.c:623 #10 0x00007ffff7b1f80a in opal_progress () at runtime/opal_progress.c:207 #11 0x00007ffff21977c5 in opal_condition_wait (m=<optimized out>, c=0x842de0) at ../../../../opal/threads/condition.h:99 #12 ompi_osc_rdma_module_fence (assert=0, win=0x842170) at osc_rdma_sync.c:207 #13 0x00007ffff7a89db5 in PMPI_Win_fence (assert=0, win=0x842170) at pwin_fence.c:60 #14 0x00000000004010d8 in main (argc=2, argv=0x7fffffffd508) at win.c:60 and rank 1 at (gdb) bt #0 0x00007ffff7288905 in raise () from /lib/libc.so.6 #1 0x00007ffff7289d7b in abort () from /lib/libc.so.6 #2 0x00007ffff72c675d in __malloc_assert () from /lib/libc.so.6 #3 0x00007ffff72c96d3 in _int_malloc () from /lib/libc.so.6 #4 0x00007ffff72cad5d in malloc () from /lib/libc.so.6 #5 0x00007ffff7a5b3ce in opal_obj_new (cls=0x7ffff7db2060) at ../../opal/class/opal_object.h:469 #6 opal_obj_new_debug (line=71, file=0x7ffff7b60323 "ompi_datatype_create.c", type=0x7ffff7db2060) at ../../opal/class/opal_object.h:251 #7 ompi_datatype_create (expectedSize=3) at ompi_datatype_create.c:71 #8 0x00007ffff7a5b7e9 in ompi_datatype_create_indexed_block (count=1, bLength=1, pDisp=0x7fffee18a834, oldType=0x7ffff7db3640, newType=0x7fffffffd070) at ompi_datatype_create_indexed.c:124 #9 0x00007ffff7a5a349 in __ompi_datatype_create_from_args (type=9, d=0x844f40, a=0x7fffee18a828, i=0x7fffee18a82c) at ompi_datatype_args.c:691 #10 __ompi_datatype_create_from_packed_description (packed_buffer=0x7fffffffd108, remote_processor=0x652b90) at ompi_datatype_args.c:626 #11 0x00007ffff7a5b045 in ompi_datatype_create_from_packed_description (packed_buffer=<optimized out>, remote_processor=<optimized out>) at ompi_datatype_args.c:779 #12 0x00007ffff218bf60 in ompi_osc_base_datatype_create (payload=0x7fffffffd108, remote_proc=<optimized out>) at ../../../../ompi/mca/osc/base/osc_base_obj_convert.h:52 #13 component_fragment_cb (btl=0x7ffff3680ce0, tag=<optimized out>, descriptor=<optimized out>, cbdata=<optimized out>) at osc_rdma_component.c:624 #14 0x00007ffff347f25f in mca_btl_sm_component_progress () at btl_sm_component.c:623 #15 0x00007ffff7b1f80a in opal_progress () at runtime/opal_progress.c:207 #16 0x00007ffff21977c5 in opal_condition_wait (m=<optimized out>, c=0x842ee0) at ../../../../opal/threads/condition.h:99 #17 ompi_osc_rdma_module_fence (assert=0, win=0x842270) at osc_rdma_sync.c:207 #18 0x00007ffff7a89db5 in PMPI_Win_fence (assert=0, win=0x842270) at pwin_fence.c:60 #19 0x00000000004010d8 in main (argc=2, argv=0x7fffffffd508) at win.c:60 This looks like memory corruption, but Open MPI internals are too noisy under valgrind for it to be obvious where to look. This is with Open MPI 1.5.4, but I observed the same thing with trunk. If I run with three processes, the graph is slightly different and only ranks 1 and 2 error (rank 0 hangs).
