linux-kernel - [26/74] IPoIB: Fix send lockup due to missed TX completion

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Date:	Sun, 07 Apr 2013 23:45:42 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Roland Dreier" <roland@...estorage.com>,
	"Dean Luick" <dean.luick@...el.com>,
	"Mike Marciniszyn" <mike.marciniszyn@...el.com>
Subject: [26/74] IPoIB: Fix send lockup due to missed TX completion

3.2.43-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Mike Marciniszyn <mike.marciniszyn@...el.com>

commit 1ee9e2aa7b31427303466776f455d43e5e3c9275 upstream.

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.

Reviewed-by: Dean Luick <dean.luick@...el.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@...el.com>
Signed-off-by: Roland Dreier <roland@...estorage.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/infiniband/ulp/ipoib/ipoib_cm.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- 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 *de
 		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);
 		}
 	}
 }

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