IPoIB: Fix send lockup due to missed TX completion

Commit f0dc117abdfa ("IPoIB: Fix TX queue lockup with mixed UD/CM
traffic") attempts to solve an issue where unprocessed UD send
completions can deadlock the netdev.

The patch doesn't fully resolve the issue because if more than half
the tx_outstanding's were UD and all of the destinations are RC
reachable, arming the CQ doesn't solve the issue.

This patch uses the IB_CQ_REPORT_MISSED_EVENTS on the
ib_req_notify_cq().  If the rc is above 0, the UD send cq completion
callback is called directly to re-arm the send completion timer.

This issue is seen in very large parallel filesystem deployments
and the patch has been shown to correct the issue.

Cc: <stable@vger.kernel.org>
Reviewed-by: Dean Luick <dean.luick@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_cm.c b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
index 67b0c1d23678..1ef880de3a41 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
@@ -758,9 +758,13 @@ void ipoib_cm_send(struct net_device *dev, struct sk_buff *skb, struct ipoib_cm_
                 if (++priv->tx_outstanding == ipoib_sendq_size) {
                         ipoib_dbg(priv, "TX ring 0x%x full, stopping kernel net queue\n",
                                   tx->qp->qp_num);
-                        if (ib_req_notify_cq(priv->send_cq, IB_CQ_NEXT_COMP))
-                                ipoib_warn(priv, "request notify on send CQ failed\n");
                         netif_stop_queue(dev);
+                        rc = ib_req_notify_cq(priv->send_cq,
+                                IB_CQ_NEXT_COMP | IB_CQ_REPORT_MISSED_EVENTS);
+                        if (rc < 0)
+                                ipoib_warn(priv, "request notify on send CQ failed\n");
+                        else if (rc)
+                                ipoib_send_comp_handler(priv->send_cq, dev);
                 }
         }
 }