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

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Message-Id: <20191002144946.176976-1-thierry.reding@gmail.com>
Date:   Wed,  2 Oct 2019 16:49:46 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     Jose Abreu <joabreu@...opsys.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Bitan Biswas <bbiswas@...dia.com>, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH net] net: stmmac: Avoid deadlock on suspend/resume

From: Thierry Reding <treding@...dia.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 <bbiswas@...dia.com>
Signed-off-by: Thierry Reding <treding@...dia.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