[ofa-general] [PATCH 1/8] IB/ipath - add barrier before updating WC head in shared memory

[Arthur Jones]

From: Ralph Campbell <ralph.campbell at qlogic.com>

Add a barrier to make sure the CPU doesn't reorder writes
to memory since user programs can be polling on the head index
update and the entry should be written before that.

Signed-off-by: Ralph Campbell <ralph.campbell at qlogic.com>
---

 drivers/infiniband/hw/ipath/ipath_cq.c    |    5 ++++-
 drivers/infiniband/hw/ipath/ipath_ruc.c   |    2 ++
 drivers/infiniband/hw/ipath/ipath_srq.c   |    2 ++
 drivers/infiniband/hw/ipath/ipath_ud.c    |    2 ++
 drivers/infiniband/hw/ipath/ipath_verbs.c |    2 ++
 5 files changed, 12 insertions(+), 1 deletions(-)

diff --git a/drivers/infiniband/hw/ipath/ipath_cq.c b/drivers/infiniband/hw/ipath/ipath_cq.c
index 9014ef6..a6f04d2 100644
--- a/drivers/infiniband/hw/ipath/ipath_cq.c
+++ b/drivers/infiniband/hw/ipath/ipath_cq.c
@@ -90,6 +90,8 @@ void ipath_cq_enter(struct ipath_cq *cq, struct ib_wc *entry, int solicited)
 	wc->queue[head].sl = entry->sl;
 	wc->queue[head].dlid_path_bits = entry->dlid_path_bits;
 	wc->queue[head].port_num = entry->port_num;
+	/* Make sure queue entry is written before the head index. */
+	smp_wmb();
 	wc->head = next;
 
 	if (cq->notify == IB_CQ_NEXT_COMP ||
@@ -139,7 +141,8 @@ int ipath_poll_cq(struct ib_cq *ibcq, int num_entries, struct ib_wc *entry)
 
 		if (tail == wc->head)
 			break;
-
+		/* Make sure entry is read after head index is read. */
+		smp_rmb();
 		qp = ipath_lookup_qpn(&to_idev(cq->ibcq.device)->qp_table,
 				      wc->queue[tail].qp_num);
 		entry->qp = &qp->ibqp;
diff --git a/drivers/infiniband/hw/ipath/ipath_ruc.c b/drivers/infiniband/hw/ipath/ipath_ruc.c
index 854deb5..8525674 100644
--- a/drivers/infiniband/hw/ipath/ipath_ruc.c
+++ b/drivers/infiniband/hw/ipath/ipath_ruc.c
@@ -194,6 +194,8 @@ int ipath_get_rwqe(struct ipath_qp *qp, int wr_id_only)
 			ret = 0;
 			goto bail;
 		}
+		/* Make sure entry is read after head index is read. */
+		smp_rmb();
 		wqe = get_rwqe_ptr(rq, tail);
 		if (++tail >= rq->size)
 			tail = 0;
diff --git a/drivers/infiniband/hw/ipath/ipath_srq.c b/drivers/infiniband/hw/ipath/ipath_srq.c
index 14cbbd6..40c36ec 100644
--- a/drivers/infiniband/hw/ipath/ipath_srq.c
+++ b/drivers/infiniband/hw/ipath/ipath_srq.c
@@ -80,6 +80,8 @@ int ipath_post_srq_receive(struct ib_srq *ibsrq, struct ib_recv_wr *wr,
 		wqe->num_sge = wr->num_sge;
 		for (i = 0; i < wr->num_sge; i++)
 			wqe->sg_list[i] = wr->sg_list[i];
+		/* Make sure queue entry is written before the head index. */
+		smp_wmb();
 		wq->head = next;
 		spin_unlock_irqrestore(&srq->rq.lock, flags);
 	}
diff --git a/drivers/infiniband/hw/ipath/ipath_ud.c b/drivers/infiniband/hw/ipath/ipath_ud.c
index 38ba771..f9a3338 100644
--- a/drivers/infiniband/hw/ipath/ipath_ud.c
+++ b/drivers/infiniband/hw/ipath/ipath_ud.c
@@ -176,6 +176,8 @@ static void ipath_ud_loopback(struct ipath_qp *sqp,
 			dev->n_pkt_drops++;
 			goto bail_sge;
 		}
+		/* Make sure entry is read after head index is read. */
+		smp_rmb();
 		wqe = get_rwqe_ptr(rq, tail);
 		if (++tail >= rq->size)
 			tail = 0;
diff --git a/drivers/infiniband/hw/ipath/ipath_verbs.c b/drivers/infiniband/hw/ipath/ipath_verbs.c
index 5aa8866..65f7181 100644
--- a/drivers/infiniband/hw/ipath/ipath_verbs.c
+++ b/drivers/infiniband/hw/ipath/ipath_verbs.c
@@ -327,6 +327,8 @@ static int ipath_post_receive(struct ib_qp *ibqp, struct ib_recv_wr *wr,
 		wqe->num_sge = wr->num_sge;
 		for (i = 0; i < wr->num_sge; i++)
 			wqe->sg_list[i] = wr->sg_list[i];
+		/* Make sure queue entry is written before the head index. */
+		smp_wmb();
 		wq->head = next;
 		spin_unlock_irqrestore(&qp->r_rq.lock, flags);
 	}