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

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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>
This commit is contained in:
Andrew Boyer 2016-11-23 12:39:18 -05:00 committed by Doug Ledford
parent 6e9bb530ff
commit dd753d8743
1 changed files with 3 additions and 2 deletions
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5
drivers/infiniband/sw/rxe/rxe_comp.c
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@ -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