[ 060/171 ] IPoIB: Fix send lockup due to missed TX completion

[Steven Rostedt]

3.6.11.2 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Mike Marciniszyn <mike.marciniszyn@xxxxxxxxx>

[ Upstream commit 1ee9e2aa7b31427303466776f455d43e5e3c9275 ]

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@xxxxxxxxxxxxxxx>
Reviewed-by: Dean Luick <dean.luick@xxxxxxxxx>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@xxxxxxxxx>
Signed-off-by: Roland Dreier <roland@xxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 drivers/infiniband/ulp/ipoib/ipoib_cm.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_cm.c b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
index 24683fd..2ad27ce 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
@@ -755,9 +755,13 @@ 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);
 		}
 	}
 }
-- 
1.7.10.4


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/