linux-kernel - [PATCH] RDMA/siw: Reuse value read using READ

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Date: Sat,  9 Mar 2024 20:27:16 +0800
From: linke li <lilinke99@...com>
To: 
Cc: lilinke99@...com,
	Bernard Metzler <bmt@...ich.ibm.com>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Leon Romanovsky <leon@...nel.org>,
	linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] RDMA/siw: Reuse value read using READ_ONCE instead of re-reading it

In siw_orqe_start_rx, the orqe's flag in the if condition is read using
READ_ONCE, checked, and then re-read, voiding all guarantees of the
checks. Reuse the value that was read by READ_ONCE to ensure the
consistency of the flags throughout the function.

Signed-off-by: linke li <lilinke99@...com>
---
 drivers/infiniband/sw/siw/siw_qp_rx.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/sw/siw/siw_qp_rx.c b/drivers/infiniband/sw/siw/siw_qp_rx.c
index ed4fc39718b4..f5f69de56882 100644
--- a/drivers/infiniband/sw/siw/siw_qp_rx.c
+++ b/drivers/infiniband/sw/siw/siw_qp_rx.c
@@ -740,6 +740,7 @@ static int siw_orqe_start_rx(struct siw_qp *qp)
 {
 	struct siw_sqe *orqe;
 	struct siw_wqe *wqe = NULL;
+	u16 orqe_flags;
 
 	if (unlikely(!qp->attrs.orq_size))
 		return -EPROTO;
@@ -748,7 +749,8 @@ static int siw_orqe_start_rx(struct siw_qp *qp)
 	smp_mb();
 
 	orqe = orq_get_current(qp);
-	if (READ_ONCE(orqe->flags) & SIW_WQE_VALID) {
+	orqe_flags = READ_ONCE(orqe->flags);
+	if (orqe_flags & SIW_WQE_VALID) {
 		/* RRESP is a TAGGED RDMAP operation */
 		wqe = rx_wqe(&qp->rx_tagged);
 		wqe->sqe.id = orqe->id;
@@ -756,7 +758,7 @@ static int siw_orqe_start_rx(struct siw_qp *qp)
 		wqe->sqe.sge[0].laddr = orqe->sge[0].laddr;
 		wqe->sqe.sge[0].lkey = orqe->sge[0].lkey;
 		wqe->sqe.sge[0].length = orqe->sge[0].length;
-		wqe->sqe.flags = orqe->flags;
+		wqe->sqe.flags = orqe_flags;
 		wqe->sqe.num_sge = 1;
 		wqe->bytes = orqe->sge[0].length;
 		wqe->processed = 0;
-- 
2.39.3 (Apple Git-146)