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Default data QPs to infinite RNR retries #71

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Default data QPs to infinite RNR retries #71

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17 changes: 17 additions & 0 deletions kernel/ibdev.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2502,6 +2502,23 @@ static int tbv_create_qp(struct ib_qp *qp, struct ib_qp_init_attr *init_attr,
init_attr->qp_type != IB_QPT_UC &&
init_attr->qp_type != IB_QPT_GSI)
return -EOPNOTSUPP;
/*
* The transport cannot retransmit on its own: a SEND that arrives
* before the peer has posted its receive gets an RNR NAK. With the
* verbs defaults (rnr_retry = 0, retry_cnt = 0) that SEND completes
* immediately with RNR_RETRY_EXC_ERR and marks the QP in error,
* taking the whole connection down on a single scheduler-induced
* race between the sender's post_send and the receiver's
* post_recv. Default data QPs to infinite RNR retries and a retry
* count instead: the SEND then waits for the peer's advertised
* recv credits (see tbv_send_rnr_waits_for_recv_credit). Users can
* still override both through modify_qp (IB_QP_RNR_RETRY /
* IB_QP_RETRY_CNT).
*/
if (!gsi) {
tqp->attr.rnr_retry = 7; /* infinite, per the IB spec */
tqp->attr.retry_cnt = TBV_SEND_MAX_RETRIES;
}
tqp->backend = tbv_ibdev_backend(qp->device);
if (tbv_backend_is_apple(tqp->backend) &&
init_attr->qp_type != IB_QPT_UC)
Expand Down