IB/qib, staging/rdma/hfi1: add s_hlock for use in post send

This patch adds an additional lock to reduce contention on the s_lock.

This lock is used in post_send() so that the post_send is not
serialized with the send engine and other send related processing.

To do this the s_next_psn is now maintained on post_send() while
post_send() related fields are moved to a new cache line.  There is
an s_avail maintained for the post_send() to mitigate trading cache
lines with the send engine.  The lock is released/acquired around
releasing the just built packet to the egress mechanism.

Reviewed-by: Jubin John <jubin.john@intel.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Dean Luick <dean.luick@intel.com>
Signed-off-by: Harish Chegondi <harish.chegondi@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

1 files changed, 9 insertions, 13 deletions

diff --git a/drivers/infiniband/hw/qib/qib_uc.c b/drivers/infiniband/hw/qib/qib_uc.c
index 1b2fc69855b2..7bdbc79ceaa3 100644
--- a/drivers/infiniband/hw/qib/qib_uc.c
+++ b/drivers/infiniband/hw/qib/qib_uc.c
@@ -41,6 +41,8 @@
  * qib_make_uc_req - construct a request packet (SEND, RDMA write)
  * @qp: a pointer to the QP
  *
+ * Assumes the s_lock is held.
+ *
  * Return 1 if constructed; otherwise, return 0.
  */
 int qib_make_uc_req(struct rvt_qp *qp)
@@ -48,20 +50,18 @@ int qib_make_uc_req(struct rvt_qp *qp)
 	struct qib_qp_priv *priv = qp->priv;
 	struct qib_other_headers *ohdr;
 	struct rvt_swqe *wqe;
-	unsigned long flags;
 	u32 hwords;
 	u32 bth0;
 	u32 len;
 	u32 pmtu = qp->pmtu;
 	int ret = 0;
 
-	spin_lock_irqsave(&qp->s_lock, flags);
-
 	if (!(ib_rvt_state_ops[qp->state] & RVT_PROCESS_SEND_OK)) {
 		if (!(ib_rvt_state_ops[qp->state] & RVT_FLUSH_SEND))
 			goto bail;
 		/* We are in the error state, flush the work request. */
-		if (qp->s_last == qp->s_head)
+		smp_read_barrier_depends(); /* see post_one_send() */
+		if (qp->s_last == ACCESS_ONCE(qp->s_head))
 			goto bail;
 		/* If DMAs are in progress, we can't flush immediately. */
 		if (atomic_read(&priv->s_dma_busy)) {
@@ -90,13 +90,13 @@ int qib_make_uc_req(struct rvt_qp *qp)
 		    RVT_PROCESS_NEXT_SEND_OK))
 			goto bail;
 		/* Check if send work queue is empty. */
-		if (qp->s_cur == qp->s_head)
+		smp_read_barrier_depends(); /* see post_one_send() */
+		if (qp->s_cur == ACCESS_ONCE(qp->s_head))
 			goto bail;
 		/*
 		 * Start a new request.
 		 */
-		wqe->psn = qp->s_next_psn;
-		qp->s_psn = qp->s_next_psn;
+		qp->s_psn = wqe->psn;
 		qp->s_sge.sge = wqe->sg_list[0];
 		qp->s_sge.sg_list = wqe->sg_list + 1;
 		qp->s_sge.num_sge = wqe->wr.num_sge;
@@ -215,15 +215,11 @@ int qib_make_uc_req(struct rvt_qp *qp)
 	qp->s_cur_sge = &qp->s_sge;
 	qp->s_cur_size = len;
 	qib_make_ruc_header(qp, ohdr, bth0 | (qp->s_state << 24),
-			    qp->s_next_psn++ & QIB_PSN_MASK);
+			    qp->s_psn++ & QIB_PSN_MASK);
 done:
-	ret = 1;
-	goto unlock;
-
+	return 1;
 bail:
 	qp->s_flags &= ~RVT_S_BUSY;
-unlock:
-	spin_unlock_irqrestore(&qp->s_lock, flags);
 	return ret;
 }