[PATCH for-next] RDMA/rxe: Convert spinlock to memory barrier

[Bob Pearson <rpearsonhpe@gmail.com>]

Currently the rxe driver takes a spinlock to safely pass a
control variable from a verbs API to a tasklet. A release/acquire
memory barrier pair can accomplish the same thing with less effort.

Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
---
 drivers/infiniband/sw/rxe/rxe_cq.c | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_cq.c b/drivers/infiniband/sw/rxe/rxe_cq.c
index b1a0ab3cd4bd..76534bc66cb6 100644
--- a/drivers/infiniband/sw/rxe/rxe_cq.c
+++ b/drivers/infiniband/sw/rxe/rxe_cq.c
@@ -42,14 +42,10 @@ int rxe_cq_chk_attr(struct rxe_dev *rxe, struct rxe_cq *cq,
 static void rxe_send_complete(struct tasklet_struct *t)
 {
 	struct rxe_cq *cq = from_tasklet(cq, t, comp_task);
-	unsigned long flags;
 
-	spin_lock_irqsave(&cq->cq_lock, flags);
-	if (cq->is_dying) {
-		spin_unlock_irqrestore(&cq->cq_lock, flags);
+	/* pairs with rxe_cq_disable */
+	if (smp_load_acquire(&cq->is_dying))
 		return;
-	}
-	spin_unlock_irqrestore(&cq->cq_lock, flags);
 
 	cq->ibcq.comp_handler(&cq->ibcq, cq->ibcq.cq_context);
 }
@@ -143,11 +139,8 @@ int rxe_cq_post(struct rxe_cq *cq, struct rxe_cqe *cqe, int solicited)
 
 void rxe_cq_disable(struct rxe_cq *cq)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&cq->cq_lock, flags);
-	cq->is_dying = true;
-	spin_unlock_irqrestore(&cq->cq_lock, flags);
+	/* pairs with rxe_send_complete */
+	smp_store_release(&cq->is_dying, true);
 }
 
 void rxe_cq_cleanup(struct rxe_pool_elem *elem)

base-commit: cbdae01d8b517b81ed271981395fee8ebd08ba7d
-- 
2.34.1