net: fec: improve safety of suspend/resume/transmit timeout paths

We should hold the rtnl lock while suspending, resuming or processing
the transmit timeout to ensure that nothing will interfere while we
bring up, take down or restart the hardware.  The transmit timeout
could run if we're preempted during suspend.

Acked-by: Fugang Duan <B38611@freescale.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/fec_main.c

@@ -1068,8 +1068,10 @@ static void fec_enet_work(struct work_struct *work)
 
 	if (fep->delay_work.timeout) {
 		fep->delay_work.timeout = false;
+		rtnl_lock();
 		fec_restart(fep->netdev, fep->full_duplex);
 		netif_wake_queue(fep->netdev);
+		rtnl_unlock();
 	}
 
 	if (fep->delay_work.trig_tx) {
@@ -2680,11 +2682,14 @@ fec_suspend(struct device *dev)
 	struct net_device *ndev = dev_get_drvdata(dev);
 	struct fec_enet_private *fep = netdev_priv(ndev);
 
+	rtnl_lock();
 	if (netif_running(ndev)) {
 		phy_stop(fep->phy_dev);
 		fec_stop(ndev);
 		netif_device_detach(ndev);
 	}
+	rtnl_unlock();
+
 	fec_enet_clk_enable(ndev, false);
 	pinctrl_pm_select_sleep_state(&fep->pdev->dev);
 
@@ -2712,11 +2717,13 @@ fec_resume(struct device *dev)
 	if (ret)
 		goto failed_clk;
 
+	rtnl_lock();
 	if (netif_running(ndev)) {
 		fec_restart(ndev, fep->full_duplex);
 		netif_device_attach(ndev);
 		phy_start(fep->phy_dev);
 	}
+	rtnl_unlock();
 
 	return 0;