[PATCH v2 04/14] NTB: ntb_transport: Publish link state after QP setup

[Koichiro Den]

ntb_transport_link_work() marks the transport link up before setting
up the QPs' MW and peer MSI state. A concurrent ntb_transport_link_up()
can then queue QP link work, which may enable RX and notify the client
before setup finishes.

Publish link_is_up with a release store after setting up all QPs,
and use acquire loads before queuing QP link work.

Fixes: fce8a7bb5b4b ("PCI-Express Non-Transparent Bridge Support")
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/anyKbq3mpLG4y7rb@SMW015318
Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
---
Changes in v2:
  - No changes.

 drivers/ntb/ntb_transport.c | 40 +++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
index c77b173dca01..75d4a2e021f4 100644
--- a/drivers/ntb/ntb_transport.c
+++ b/drivers/ntb/ntb_transport.c
@@ -922,6 +922,16 @@ static void ntb_qp_link_down_reset(struct ntb_transport_qp *qp)
 		qp->remote_rx_info->entry = qp->rx_max_entry - 1;
 }
 
+static void ntb_transport_schedule_qp_link(struct ntb_transport_qp *qp,
+					   unsigned long delay)
+{
+	struct ntb_transport_ctx *nt = qp->transport;
+
+	/* Pair with the link publication in ntb_transport_link_work(). */
+	if (smp_load_acquire(&nt->link_is_up))
+		schedule_delayed_work(&qp->link_work, delay);
+}
+
 static void ntb_qp_link_cleanup(struct ntb_transport_qp *qp)
 {
 	struct ntb_transport_ctx *nt = qp->transport;
@@ -941,13 +951,10 @@ static void ntb_qp_link_cleanup_work(struct work_struct *work)
 	struct ntb_transport_qp *qp = container_of(work,
 						   struct ntb_transport_qp,
 						   link_cleanup);
-	struct ntb_transport_ctx *nt = qp->transport;
 
 	ntb_qp_link_cleanup(qp);
-
-	if (nt->link_is_up)
-		schedule_delayed_work(&qp->link_work,
-				      msecs_to_jiffies(NTB_LINK_DOWN_TIMEOUT));
+	ntb_transport_schedule_qp_link(qp,
+				       msecs_to_jiffies(NTB_LINK_DOWN_TIMEOUT));
 }
 
 static void ntb_qp_link_down(struct ntb_transport_qp *qp)
@@ -1089,16 +1096,19 @@ static void ntb_transport_link_work(struct work_struct *work)
 			goto out1;
 	}
 
-	nt->link_is_up = true;
-
 	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);
+	}
+
+	/* Publish the link only after every QP has been set up. */
+	smp_store_release(&nt->link_is_up, true);
+
+	for (i = 0; i < nt->qp_count; i++) {
+		struct ntb_transport_qp *qp = &nt->qp_vec[i];
 
 		if (qp->client_ready)
-			schedule_delayed_work(&qp->link_work, 0);
+			ntb_transport_schedule_qp_link(qp, 0);
 	}
 
 	return;
@@ -1146,9 +1156,10 @@ static void ntb_qp_link_work(struct work_struct *work)
 
 		if (qp->active)
 			tasklet_schedule(&qp->rxc_db_work);
-	} else if (nt->link_is_up)
-		schedule_delayed_work(&qp->link_work,
-				      msecs_to_jiffies(NTB_LINK_DOWN_TIMEOUT));
+	} else {
+		ntb_transport_schedule_qp_link(qp,
+					       msecs_to_jiffies(NTB_LINK_DOWN_TIMEOUT));
+	}
 }
 
 static int ntb_transport_init_queue(struct ntb_transport_ctx *nt,
@@ -2392,8 +2403,7 @@ void ntb_transport_link_up(struct ntb_transport_qp *qp)
 
 	qp->client_ready = true;
 
-	if (qp->transport->link_is_up)
-		schedule_delayed_work(&qp->link_work, 0);
+	ntb_transport_schedule_qp_link(qp, 0);
 }
 EXPORT_SYMBOL_GPL(ntb_transport_link_up);
 
-- 
2.51.0