svn commit: r261167 - head/sys/dev/virtio/network

[Bryan Venteicher]

Author: bryanv
Date: Sat Jan 25 19:57:30 2014
New Revision: 261167
URL: http://svnweb.freebsd.org/changeset/base/261167

Log:
  Avoid queue unlock followed by relock when the enable interrupt race is lost
  
  This already happens infrequently, and the hold time is still bounded since
  we defer to a taskqueue after a few tries.

Modified:
  head/sys/dev/virtio/network/if_vtnet.c

Modified: head/sys/dev/virtio/network/if_vtnet.c
==============================================================================
--- head/sys/dev/virtio/network/if_vtnet.c	Sat Jan 25 19:55:42 2014	(r261166)
+++ head/sys/dev/virtio/network/if_vtnet.c	Sat Jan 25 19:57:30 2014	(r261167)
@@ -1821,9 +1821,9 @@ vtnet_rx_vq_intr(void *xrxq)
 		return;
 	}
 
-again:
 	VTNET_RXQ_LOCK(rxq);
 
+again:
 	if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0) {
 		VTNET_RXQ_UNLOCK(rxq);
 		return;
@@ -1837,10 +1837,11 @@ again:
 		 * This is an occasional condition or race (when !more),
 		 * so retry a few times before scheduling the taskqueue.
 		 */
-		rxq->vtnrx_stats.vrxs_rescheduled++;
-		VTNET_RXQ_UNLOCK(rxq);
 		if (tries++ < VTNET_INTR_DISABLE_RETRIES)
 			goto again;
+
+		VTNET_RXQ_UNLOCK(rxq);
+		rxq->vtnrx_stats.vrxs_rescheduled++;
 		taskqueue_enqueue(rxq->vtnrx_tq, &rxq->vtnrx_intrtask);
 	} else
 		VTNET_RXQ_UNLOCK(rxq);
@@ -2408,9 +2409,9 @@ vtnet_tx_vq_intr(void *xtxq)
 		return;
 	}
 
-again:
 	VTNET_TXQ_LOCK(txq);
 
+again:
 	if ((ifp->if_drv_flags & IFF_DRV_RUNNING) == 0) {
 		VTNET_TXQ_UNLOCK(txq);
 		return;
@@ -2426,9 +2427,10 @@ again:
 		 * This is an occasional race, so retry a few times
 		 * before scheduling the taskqueue.
 		 */
-		VTNET_TXQ_UNLOCK(txq);
 		if (tries++ < VTNET_INTR_DISABLE_RETRIES)
 			goto again;
+
+		VTNET_TXQ_UNLOCK(txq);
 		txq->vtntx_stats.vtxs_rescheduled++;
 		taskqueue_enqueue(txq->vtntx_tq, &txq->vtntx_intrtask);
 	} else