Revert "IPoIB: Make the carrier_on_task race aware"

This reverts commit 67d7209e.

The series of IPoIB bug fixes that went into 3.19-rc1 introduce
regressions, and after trying to sort things out, we decided to revert
to 3.18's IPoIB driver and get things right for 3.20.
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/ulp/ipoib/ipoib_multicast.c

@@ -353,27 +353,18 @@ void ipoib_mcast_carrier_on_task(struct work_struct *work)
 						   carrier_on_task);
 	struct ib_port_attr attr;
 
+	/*
+	 * Take rtnl_lock to avoid racing with ipoib_stop() and
+	 * turning the carrier back on while a device is being
+	 * removed.
+	 */
 	if (ib_query_port(priv->ca, priv->port, &attr) ||
 	    attr.state != IB_PORT_ACTIVE) {
 		ipoib_dbg(priv, "Keeping carrier off until IB port is active\n");
 		return;
 	}
 
-	/*
-	 * Take rtnl_lock to avoid racing with ipoib_stop() and
-	 * turning the carrier back on while a device is being
-	 * removed.  However, ipoib_stop() will attempt to flush
-	 * the workqueue while holding the rtnl lock, so loop
-	 * on trylock until either we get the lock or we see
-	 * FLAG_ADMIN_UP go away as that signals that we are bailing
-	 * and can safely ignore the carrier on work
-	 */
-	while (!rtnl_trylock()) {
-		if (!test_bit(IPOIB_FLAG_ADMIN_UP, &priv->flags))
-			return;
-		else
-			msleep(20);
-	}
+	rtnl_lock();
 	if (!ipoib_cm_admin_enabled(priv->dev))
 		dev_set_mtu(priv->dev, min(priv->mcast_mtu, priv->admin_mtu));
 	netif_carrier_on(priv->dev);