net: stmmac: Avoid deadlock on suspend/resume

The stmmac driver will try to acquire its private mutex during suspend
via phylink_resolve() -> stmmac_mac_link_down() -> stmmac_eee_init().
However, the phylink configuration is updated with the private mutex
held already, which causes a deadlock during suspend.

Fix this by moving the phylink configuration updates out of the region
of code protected by the private mutex.

Fixes: 19e13cb ("net: stmmac: Hold rtnl lock in suspend/resume callbacks")
Suggested-by: Bitan Biswas <bbiswas@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: thierryreding

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -4716,10 +4716,10 @@ int stmmac_suspend(struct device *dev)
 	if (!ndev || !netif_running(ndev))
 		return 0;
 
-	mutex_lock(&priv->lock);
-
 	phylink_mac_change(priv->phylink, false);
 
+	mutex_lock(&priv->lock);
+
 	netif_device_detach(ndev);
 	stmmac_stop_all_queues(priv);
 
@@ -4733,9 +4733,11 @@ int stmmac_suspend(struct device *dev)
 		stmmac_pmt(priv, priv->hw, priv->wolopts);
 		priv->irq_wake = 1;
 	} else {
+		mutex_unlock(&priv->lock);
 		rtnl_lock();
 		phylink_stop(priv->phylink);
 		rtnl_unlock();
+		mutex_lock(&priv->lock);
 
 		stmmac_mac_set(priv, priv->ioaddr, false);
 		pinctrl_pm_select_sleep_state(priv->device);
@@ -4827,6 +4829,8 @@ int stmmac_resume(struct device *dev)
 
 	stmmac_start_all_queues(priv);
 
+	mutex_unlock(&priv->lock);
+
 	if (!device_may_wakeup(priv->device)) {
 		rtnl_lock();
 		phylink_start(priv->phylink);
@@ -4835,8 +4839,6 @@ int stmmac_resume(struct device *dev)
 
 	phylink_mac_change(priv->phylink, true);
 
-	mutex_unlock(&priv->lock);
-
 	return 0;
 }
 EXPORT_SYMBOL_GPL(stmmac_resume);