Data transferred by `MPI_BSEND` may corrupt if all of the following
conditions are met.
- The message size is less than the eager limit.
- The `btl_alloc` function in the BTL interface returns `NULL`
for some reason.
- The MPI program overwrites the send buffer after `MPI_BSEND`
returns.
The problem is in the way of pending a send request in ob1 PML.
The `mca_pml_ob1_send_request_start_copy` function retruns
`OMPI_ERR_OUT_OF_RESOURCE` if `mca_bml_base_alloc` function returns
`des = NULL`. In this case, the send request is added to the
`send_pending` list and `MPI_BSEND` returns immediately. Next time
the `mca_pml_ob1_send_request_start_copy` function tries sending,
the user buffer may have been overwritten by the MPI program.
Call hierarchy of `MPI_BSEND`:
```
MPI_Bsend
mca_pml_ob1_send
if (MCA_PML_BASE_SEND_BUFFERED == sendmode)
mca_pml_ob1_isend
MCA_PML_OB1_SEND_REQUEST_START_W_SEQ
mca_pml_ob1_send_request_start_seq
mca_pml_ob1_send_request_start_btl
if (size <= eager_limit)
if (req_send_mode == MCA_PML_BASE_SEND_BUFFERED)
mca_pml_ob1_send_request_start_copy
mca_bml_base_alloc
btl_alloc
if (OMPI_ERR_OUT_OF_RESOURCE == rc)
add_request_to_send_pending
ompi_request_free
```
To solve this problem, we should save the data to the buffer
attached by `MPI_BUFFER_ATTACH` before leaving `MPI_BSEND`.
This problem was introduced by ob1 optimization (commits 2b57f422
and a06e491c) in v1.8 series.
Signed-off-by: KAWASHIMA Takahiro <t-kawashima@jp.fujitsu.com>
0021616984