r8169: prevent potential deadlock in rtl8169_close

ndo_stop() is RTNL-protected by net core, and the worker function takes
RTNL as well. Therefore we will deadlock when trying to execute a
pending work synchronously. To fix this execute any pending work
asynchronously. This will do no harm because netif_running() is false
in ndo_stop(), and therefore the work function is effectively a no-op.
However we have to ensure that no task is running or pending after
rtl_remove_one(), therefore add a call to cancel_work_sync().

Fixes: abe5fc4 ("r8169: use RTNL to protect critical sections")
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/12395867-1d17-4cac-aa7d-c691938fcddf@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: hkallweit

drivers/net/ethernet/realtek/r8169_main.c

@@ -4694,7 +4694,7 @@ static int rtl8169_close(struct net_device *dev)
 	rtl8169_down(tp);
 	rtl8169_rx_clear(tp);
 
-	cancel_work_sync(&tp->wk.work);
+	cancel_work(&tp->wk.work);
 
 	free_irq(tp->irq, tp);
 
@@ -4928,6 +4928,8 @@ static void rtl_remove_one(struct pci_dev *pdev)
 	if (pci_dev_run_wake(pdev))
 		pm_runtime_get_noresume(&pdev->dev);
 
+	cancel_work_sync(&tp->wk.work);
+
 	unregister_netdev(tp->dev);
 
 	if (tp->dash_type != RTL_DASH_NONE)