[mvapich-discuss] MPI_File_read_at_all external32 bug in MV2-2.1

[Hari Subramoni]

Hi Adam,

Thanks a lot for the report. We will take a look at this and get back to
you.

Thx,
Hari.
On Oct 30, 2015 2:49 PM, "Adam T. Moody" <moody20 at llnl.gov> wrote:

> Hello MVAPICH team,
> I've hit a bug in MPI_File_read_at_all in MVAPICH2-2.1.  I have an
> application that reads and writes files in external32 format.  It writes
> the file just fine, but it throws the following error when reading the file
> back:
>
> internal ABORT - process 0
> srun: error: rzmerl2: task 0: Exited with exit code 1
> Assertion failed in file src/mpid/common/datatype/mpid_ext32_segment.c at
> line 277: FALSE
> memcpy argument memory ranges overlap, dst_=0x2aaab5c160a8
> src_=0x2aaab5c160a8 len_=176
>
> Above, MPI is trying to do a memcpy where the source and destination
> buffer are the same address.  Looking through the code for MVAPICH2-2.1,
> the problem seems to be at line 132 in src/mpi/romio/mpi-io/read_all.c:
>
>    if (e32_buf != NULL) {
>        error_code = MPIU_read_external32_conversion_fn(xbuf, datatype,
>                count, e32_buf);
>    ADIOI_Free(e32_buf);
>    }
>
> I think the fix is to change "xbuf" above to "buf" as it is in read.c
> below:
>
>    if (e32_buf != NULL) {
>        error_code = MPIU_read_external32_conversion_fn(buf, datatype,
>                count, e32_buf);
>    ADIOI_Free(e32_buf);
>    }
>
> When in external32 mode, xbuf == e32_buf, which acts as a temporary buffer
> in which to read the data.  The code is then meant to unpack and convert
> the data from the temporary buffer into the user buffer at buf.
>
> It's probably worth checking the other external32 code paths to look for
> similar bugs.
> Thanks,
> -Adam
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