On Tue, Jul 04, 2017 at 07:49:11PM +0100, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" <dgilb...@redhat.com> > > Fix a race where the destination might try and send the source a > WRID_READY before the source has done a post-recv for it. > > rdma_post_recv has to happen after the qp exists, and we're > OK since we've already called qemu_rdma_source_init that calls > qemu_alloc_qp.
Though I am not very familiar with the whole RDMA path, this makes sense to me. > > This corresponds to: > https://bugzilla.redhat.com/show_bug.cgi?id=1285044 > > The race can be triggered by adding a few ms wait before this > post_recv_control (which was originally due to me turning on loads of > debug). > > Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com> Reviewed-by: Peter Xu <pet...@redhat.com> > --- > migration/rdma.c | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/migration/rdma.c b/migration/rdma.c > index c6bc607a03..6111e10c70 100644 > --- a/migration/rdma.c > +++ b/migration/rdma.c > @@ -2365,6 +2365,12 @@ static int qemu_rdma_connect(RDMAContext *rdma, Error > **errp) > > caps_to_network(&cap); > > + ret = qemu_rdma_post_recv_control(rdma, RDMA_WRID_READY); > + if (ret) { > + ERROR(errp, "posting second control recv"); > + goto err_rdma_source_connect; > + } > + > ret = rdma_connect(rdma->cm_id, &conn_param); > if (ret) { > perror("rdma_connect"); > @@ -2405,12 +2411,6 @@ static int qemu_rdma_connect(RDMAContext *rdma, Error > **errp) > > rdma_ack_cm_event(cm_event); > > - ret = qemu_rdma_post_recv_control(rdma, RDMA_WRID_READY); > - if (ret) { > - ERROR(errp, "posting second control recv!"); > - goto err_rdma_source_connect; > - } > - > rdma->control_ready_expected = 1; > rdma->nb_sent = 0; > return 0; > -- > 2.13.0 > -- Peter Xu
