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The worker can then publish a QP > > > whose memory-window state is only partly initialized, and later work can > > > use stale or incomplete pointers. > > > > > > Set up every QP memory window before publishing the transport link. On > > > failure, clear the QP pointers before releasing its MW backing and leave > > > the link down. > > > > > > Fixes: a754a8fcaf38 ("NTB: allocate number transport entries depending on size of ring size") > > > Signed-off-by: Koichiro Den > > > --- > > > drivers/ntb/ntb_transport.c | 20 ++++++++++++++++---- > > > 1 file changed, 16 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c > > > index f59f926d4bfa..3efc50955253 100644 > > > --- a/drivers/ntb/ntb_transport.c > > > +++ b/drivers/ntb/ntb_transport.c > > > @@ -1084,14 +1084,19 @@ static void ntb_transport_link_work(struct work_struct *work) > > > goto out1; > > > } > > > > > > - nt->link_is_up = true; > > > + nt->link_is_up = false; > > > + for (i = 0; i < nt->qp_count; i++) { > > > + rc = ntb_transport_setup_qp_mw(nt, i); > > > + if (rc) > > > + goto out1; > > > + ntb_transport_setup_qp_peer_msi(nt, i); > > > + } > > > > > > + /* Publish the link only after every QP has been set up. */ > > > + nt->link_is_up = true; > > > > Not sure if need WRITE_ONCE() or other memory barrier to make sure > > ntb_transport_setup_qp_mw() and ntb_transport_setup_qp_peer_msi() actually > > complete before set this flag. > > In that sense, I think we need a compiler barrier + WRITE_ONCE to avoid > use_msi=true <-> nt->link_is_up=true reordering in case dev_info becomes no-op. > > But if we want this nt->link_is_up read/write more robust, here I would choose > smp_store_release(&nt->link_is_up, true), paired with smp_load_acquire() in > ntb_transport_link_up(), because another CPU can possibly observe > link_is_up=true there and queue the work. > > I'm not sure this compiler or memory barrier issue should be folded into this > small patch, but if preferred, I'll do so. It should be seperate patch to fix it. Frank > > Thanks for the review, > Koichiro > > > > > Frank > > > > > for (i = 0; i < nt->qp_count; i++) { > > > struct ntb_transport_qp *qp = &nt->qp_vec[i]; > > > > > > - ntb_transport_setup_qp_mw(nt, i); > > > - ntb_transport_setup_qp_peer_msi(nt, i); > > > - > > > if (qp->client_ready) > > > schedule_delayed_work(&qp->link_work, 0); > > > } > > > @@ -1099,6 +1104,13 @@ static void ntb_transport_link_work(struct work_struct *work) > > > return; > > > > > > out1: > > > + for (i = 0; i < nt->qp_count; i++) { > > > + struct ntb_transport_qp *qp = &nt->qp_vec[i]; > > > + > > > + qp->rx_buff = NULL; > > > + qp->remote_rx_info = NULL; > > > + } > > > + > > > for (i = 0; i < nt->mw_count; i++) > > > ntb_free_mw(nt, i); > > > > > > -- > > > 2.51.0 > > >