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From: Jack F Vogel <jfv@FreeBSD.org>
Date: Thu, 15 Aug 2013 21:24:44 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-stable@freebsd.org, svn-src-stable-9@freebsd.org
Subject: svn commit: r254385 - stable/9/sys/dev/e1000
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Author: jfv
Date: Thu Aug 15 21:24:43 2013
New Revision: 254385
URL: http://svnweb.freebsd.org/changeset/base/254385

Log:
  MFC r254264  Make the igb_mq_start() routine use TRYLOCK rather than simple
               queuing, there were latency and other problems with the latter.

Modified:
  stable/9/sys/dev/e1000/if_igb.c
Directory Properties:
  stable/9/sys/   (props changed)
  stable/9/sys/dev/   (props changed)
  stable/9/sys/dev/e1000/   (props changed)

Modified: stable/9/sys/dev/e1000/if_igb.c
==============================================================================
--- stable/9/sys/dev/e1000/if_igb.c	Thu Aug 15 21:09:05 2013	(r254384)
+++ stable/9/sys/dev/e1000/if_igb.c	Thu Aug 15 21:24:43 2013	(r254385)
@@ -972,7 +972,13 @@ igb_mq_start(struct ifnet *ifp, struct m
 	que = &adapter->queues[i];
 
 	err = drbr_enqueue(ifp, txr->br, m);
-	taskqueue_enqueue(que->tq, &txr->txq_task);
+	if (err)
+		return (err);
+	if (IGB_TX_TRYLOCK(txr)) {
+		err = igb_mq_start_locked(ifp, txr);
+		IGB_TX_UNLOCK(txr);
+	} else
+		taskqueue_enqueue(que->tq, &txr->txq_task);
 
 	return (err);
 }