The following message occurs when running an AI application with TID RDMA
enabled:

hfi1 0000:7f:00.0: hfi1_0: [QP74] hfi1_tid_timeout 4084
hfi1 0000:7f:00.0: hfi1_0: [QP70] hfi1_tid_timeout 4084

The issue happens when TID RDMA WRITE request is followed by an
IB_WR_RDMA_WRITE_WITH_IMM request, the latter could be completed first on
the responder side. As a result, no ACK packet for the latter could be
sent because the TID RDMA WRITE request is still being processed on the
responder side.

When the TID RDMA WRITE request is eventually completed, the requester
will wait for the IB_WR_RDMA_WRITE_WITH_IMM request to be acknowledged.

If the next request is another TID RDMA WRITE request, no TID RDMA WRITE
DATA packet could be sent because the preceding IB_WR_RDMA_WRITE_WITH_IMM
request is not completed yet.

Consequently the IB_WR_RDMA_WRITE_WITH_IMM will be retried but it will be
ignored on the responder side because the responder thinks it has already
been completed. Eventually the retry will be exhausted and the qp will be
put into error state on the requester side. On the responder side, the TID
resource timer will eventually expire because no TID RDMA WRITE DATA
packets will be received for the second TID RDMA WRITE request.  There is
also risk of a write-after-write memory corruption due to the issue.

Fix by adding a requester side interlock to prevent any potential data
corruption and TID RDMA protocol error.

Fixes: a0b34f75 ("IB/hfi1: Add interlock between a TID RDMA request and other requests")
Link: https://lore.kernel.org/r/20200811174931.191210.84093.stgit@awfm-01.aw.intel.com
Cc: <stable@vger.kernel.org> # 5.4.x+
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>