IPoIB: Move ipoib_ib_dev_flush() to ipoib workqueue

Move ipoib_ib_dev_flush() to ipoib's workqueue.  This keeps it ordered
with respect to other work scheduled by the ipoib driver.  This fixes
problems with races, for example:
 - ipoib_ib_dev_flush() has started running because of an IB event
 - user does ifconfig ib0 down
 - ipoib_mcast_stop_thread() gets called twice and waits for the same
   completion twice

Signed-off-by: Jack Morgenstein <jackm@mellanox.co.il>
Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/ulp/ipoib/ipoib.h

@@ -259,7 +259,7 @@ void ipoib_ib_dev_cleanup(struct net_device *dev);
 
 int ipoib_ib_dev_open(struct net_device *dev);
 int ipoib_ib_dev_up(struct net_device *dev);
-int ipoib_ib_dev_down(struct net_device *dev);
+int ipoib_ib_dev_down(struct net_device *dev, int flush);
 int ipoib_ib_dev_stop(struct net_device *dev);
 
 int ipoib_dev_init(struct net_device *dev, struct ib_device *ca, int port);

drivers/infiniband/ulp/ipoib/ipoib_ib.c

@@ -435,7 +435,7 @@ int ipoib_ib_dev_up(struct net_device *dev)
 	return ipoib_mcast_start_thread(dev);
 }
 
-int ipoib_ib_dev_down(struct net_device *dev)
+int ipoib_ib_dev_down(struct net_device *dev, int flush)
 {
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
 
@@ -450,10 +450,11 @@ int ipoib_ib_dev_down(struct net_device *dev)
 		set_bit(IPOIB_PKEY_STOP, &priv->flags);
 		cancel_delayed_work(&priv->pkey_task);
 		mutex_unlock(&pkey_mutex);
-		flush_workqueue(ipoib_workqueue);
+		if (flush)
+			flush_workqueue(ipoib_workqueue);
 	}
 
-	ipoib_mcast_stop_thread(dev, 1);
+	ipoib_mcast_stop_thread(dev, flush);
 	ipoib_mcast_dev_flush(dev);
 
 	ipoib_flush_paths(dev);
@@ -591,7 +592,7 @@ void ipoib_ib_dev_flush(void *_dev)
 
 	ipoib_dbg(priv, "flushing\n");
 
-	ipoib_ib_dev_down(dev);
+	ipoib_ib_dev_down(dev, 0);
 
 	/*
 	 * The device could have been brought down between the start and when

drivers/infiniband/ulp/ipoib/ipoib_main.c

@@ -133,7 +133,13 @@ static int ipoib_stop(struct net_device *dev)
 
 	netif_stop_queue(dev);
 
-	ipoib_ib_dev_down(dev);
+	/*
+	 * Now flush workqueue to make sure a scheduled task doesn't
+	 * bring our internal state back up.
+	 */
+	flush_workqueue(ipoib_workqueue);
+
+	ipoib_ib_dev_down(dev, 1);
 	ipoib_ib_dev_stop(dev);
 
 	if (!test_bit(IPOIB_FLAG_SUBINTERFACE, &priv->flags)) {

drivers/infiniband/ulp/ipoib/ipoib_verbs.c

@@ -255,6 +255,6 @@ void ipoib_event(struct ib_event_handler *handler,
 	    record->event == IB_EVENT_LID_CHANGE  ||
 	    record->event == IB_EVENT_SM_CHANGE) {
 		ipoib_dbg(priv, "Port active event\n");
-		schedule_work(&priv->flush_task);
+		queue_work(ipoib_workqueue, &priv->flush_task);
 	}
 }