diff mbox

[v2,2/8] IB/rxe: Advance the consumer pointer before posting the CQE

Message ID 1479922764-13091-3-git-send-email-andrew.boyer@dell.com (mailing list archive)
State Accepted
Headers show

Commit Message

Andrew Boyer Nov. 23, 2016, 5:39 p.m. UTC 
A simple userspace application might poll the CQ, find a completion,
and then attempt to post a new WQE to the SQ. A spurious error can
occur if the userspace application detects a full SQ in the instant
before the kernel is able to advance the SQ consumer pointer.

This is noticeable when using single-entry SQs with ibv_rc_pingpong
if lots of kernel and userspace library debugging is enabled.

Signed-off-by: Andrew Boyer <andrew.boyer@dell.com>
Reviewed-by: Yonatan Cohen <yonatanc@mellanox.com>
---
 drivers/infiniband/sw/rxe/rxe_comp.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
diff mbox

Patch

diff --git a/drivers/infiniband/sw/rxe/rxe_comp.c b/drivers/infiniband/sw/rxe/rxe_comp.c
index 6c5e29d..d46c49b 100644
--- a/drivers/infiniband/sw/rxe/rxe_comp.c
+++ b/drivers/infiniband/sw/rxe/rxe_comp.c
@@ -420,11 +420,12 @@  static void do_complete(struct rxe_qp *qp, struct rxe_send_wqe *wqe)
 	    (wqe->wr.send_flags & IB_SEND_SIGNALED) ||
 	    (qp->req.state == QP_STATE_ERROR)) {
 		make_send_cqe(qp, wqe, &cqe);
+		advance_consumer(qp->sq.queue);
 		rxe_cq_post(qp->scq, &cqe, 0);
+	} else {
+		advance_consumer(qp->sq.queue);
 	}
 
-	advance_consumer(qp->sq.queue);
-
 	/*
 	 * we completed something so let req run again
 	 * if it is trying to fence