linux-kernel - [PATCH net] bcm63xx_enet: fix sporadic kernel panic

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Message-Id: <20210222013530.1356-1-liew.s.piaw@gmail.com>
Date:   Mon, 22 Feb 2021 09:35:30 +0800
From:   Sieng Piaw Liew <liew.s.piaw@...il.com>
To:     davem@...emloft.net, kuba@...nel.org, f.fainelli@...il.com
Cc:     bcm-kernel-feedback-list@...adcom.com, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Sieng Piaw Liew <liew.s.piaw@...il.com>
Subject: [PATCH net] bcm63xx_enet: fix sporadic kernel panic

In ndo_stop functions, netdev_completed_queue() is called during forced
tx reclaim, after netdev_reset_queue(). This may trigger kernel panic if
there is any tx skb left.

This patch moves netdev_reset_queue() to after tx reclaim, so BQL can
complete successfully then reset.

Signed-off-by: Sieng Piaw Liew <liew.s.piaw@...il.com>
---
 drivers/net/ethernet/broadcom/bcm63xx_enet.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bcm63xx_enet.c b/drivers/net/ethernet/broadcom/bcm63xx_enet.c
index fd8767213165..977f097fc7bf 100644
--- a/drivers/net/ethernet/broadcom/bcm63xx_enet.c
+++ b/drivers/net/ethernet/broadcom/bcm63xx_enet.c
@@ -1192,7 +1192,6 @@ static int bcm_enet_stop(struct net_device *dev)
 	kdev = &priv->pdev->dev;
 
 	netif_stop_queue(dev);
-	netdev_reset_queue(dev);
 	napi_disable(&priv->napi);
 	if (priv->has_phy)
 		phy_stop(dev->phydev);
@@ -1231,6 +1230,9 @@ static int bcm_enet_stop(struct net_device *dev)
 	if (priv->has_phy)
 		phy_disconnect(dev->phydev);
 
+	/* reset BQL after forced tx reclaim to prevent kernel panic */
+	netdev_reset_queue(dev);
+
 	return 0;
 }
 
@@ -2343,7 +2345,6 @@ static int bcm_enetsw_stop(struct net_device *dev)
 
 	del_timer_sync(&priv->swphy_poll);
 	netif_stop_queue(dev);
-	netdev_reset_queue(dev);
 	napi_disable(&priv->napi);
 	del_timer_sync(&priv->rx_timeout);
 
@@ -2371,6 +2372,9 @@ static int bcm_enetsw_stop(struct net_device *dev)
 		free_irq(priv->irq_tx, dev);
 	free_irq(priv->irq_rx, dev);
 
+	/* reset BQL after forced tx reclaim to prevent kernel panic */
+	netdev_reset_queue(dev);
+
 	return 0;
 }
 
-- 
2.17.1