Commit dd753d87 authored Nov 23, 2016 by Andrew Boyer Committed by Doug Ledford Dec 12, 2016

IB/rxe: Advance the consumer pointer before posting the CQE



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>
Signed-off-by: Doug Ledford <dledford@redhat.com>

parent 6e9bb530

drivers/infiniband/sw/rxe/rxe_comp.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -420,10 +420,11 @@ 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);
		}

		/*
		* we completed something so let req run again