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Subject[PING][PATCH] IBcore/CM: Issue DREQ when receiving REQ/REP for stale QP
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On 10/28/2016 01:14 PM, Hans Westgaard Ry wrote:
> from "InfiBand Architecture Specifications Volume 1":
>
> A QP is said to have a stale connection when only one side has
> connection information. A stale connection may result if the remote CM
> had dropped the connection and sent a DREQ but the DREQ was never
> received by the local CM. Alternatively the remote CM may have lost
> all record of past connections because its node crashed and rebooted,
> while the local CM did not become aware of the remote node's reboot
> and therefore did not clean up stale connections.
>
> and:
>
> A local CM may receive a REQ/REP for a stale connection. It shall
> abort the connection issuing REJ to the REQ/REP. It shall then issue
> DREQ with "DREQ:remote QPN” set to the remote QPN from the REQ/REP.
>
> This patch solves a problem with reuse of QPN. Current codebase, that
> is IPoIB, relies on a REAP-mechanism to do cleanup of the structures
> in CM. A problem with this is the timeconstants governing this
> mechanism; they are up to 768 seconds and the interface may look
> inresponsive in that period. Issuing a DREQ (and receiving a DREP)
> does the necessary cleanup and the interface comes up.
>
> Signed-off-by: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
> Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>
> ---
> drivers/infiniband/core/cm.c | 24 +++++++++++++++++++++++-
> 1 file changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
> index c995255..c97e4d5 100644
> --- a/drivers/infiniband/core/cm.c
> +++ b/drivers/infiniband/core/cm.c
> @@ -1519,6 +1519,7 @@ static struct cm_id_private * cm_match_req(struct cm_work *work,
> struct cm_id_private *listen_cm_id_priv, *cur_cm_id_priv;
> struct cm_timewait_info *timewait_info;
> struct cm_req_msg *req_msg;
> + struct ib_cm_id *cm_id;
>
> req_msg = (struct cm_req_msg *)work->mad_recv_wc->recv_buf.mad;
>
> @@ -1540,10 +1541,18 @@ static struct cm_id_private * cm_match_req(struct cm_work *work,
> timewait_info = cm_insert_remote_qpn(cm_id_priv->timewait_info);
> if (timewait_info) {
> cm_cleanup_timewait(cm_id_priv->timewait_info);
> + cur_cm_id_priv = cm_get_id(timewait_info->work.local_id,
> + timewait_info->work.remote_id);
> +
> spin_unlock_irq(&cm.lock);
> cm_issue_rej(work->port, work->mad_recv_wc,
> IB_CM_REJ_STALE_CONN, CM_MSG_RESPONSE_REQ,
> NULL, 0);
> + if (cur_cm_id_priv) {
> + cm_id = &cur_cm_id_priv->id;
> + ib_send_cm_dreq(cm_id, NULL, 0);
> + cm_deref_id(cur_cm_id_priv);
> + }
> return NULL;
> }
>
> @@ -1919,6 +1928,9 @@ static int cm_rep_handler(struct cm_work *work)
> struct cm_id_private *cm_id_priv;
> struct cm_rep_msg *rep_msg;
> int ret;
> + struct cm_id_private *cur_cm_id_priv;
> + struct ib_cm_id *cm_id;
> + struct cm_timewait_info *timewait_info;
>
> rep_msg = (struct cm_rep_msg *)work->mad_recv_wc->recv_buf.mad;
> cm_id_priv = cm_acquire_id(rep_msg->remote_comm_id, 0);
> @@ -1953,16 +1965,26 @@ static int cm_rep_handler(struct cm_work *work)
> goto error;
> }
> /* Check for a stale connection. */
> - if (cm_insert_remote_qpn(cm_id_priv->timewait_info)) {
> + timewait_info = cm_insert_remote_qpn(cm_id_priv->timewait_info);
> + if (timewait_info) {
> rb_erase(&cm_id_priv->timewait_info->remote_id_node,
> &cm.remote_id_table);
> cm_id_priv->timewait_info->inserted_remote_id = 0;
> + cur_cm_id_priv = cm_get_id(timewait_info->work.local_id,
> + timewait_info->work.remote_id);
> +
> spin_unlock(&cm.lock);
> spin_unlock_irq(&cm_id_priv->lock);
> cm_issue_rej(work->port, work->mad_recv_wc,
> IB_CM_REJ_STALE_CONN, CM_MSG_RESPONSE_REP,
> NULL, 0);
> ret = -EINVAL;
> + if (cur_cm_id_priv) {
> + cm_id = &cur_cm_id_priv->id;
> + ib_send_cm_dreq(cm_id, NULL, 0);
> + cm_deref_id(cur_cm_id_priv);
> + }
> +
> goto error;
> }
> spin_unlock(&cm.lock);

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