[PATCH net] net: stmmac: Avoid deadlock on suspend/resume

[Thierry Reding]

From: Thierry Reding <tred...@nvidia.com>

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: 19e13cb27b99 ("net: stmmac: Hold rtnl lock in suspend/resume callbacks")
Suggested-by: Bitan Biswas <bbis...@nvidia.com>
Signed-off-by: Thierry Reding <tred...@nvidia.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c 
b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 843d53e084b7..c76a1336a451 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/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);
-- 
2.23.0