linux-kernel - [PATCH 2/2] net: macb: Unregister nedev before MDIO bus in remove

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Message-Id: <20231126141046.3505343-3-claudiu.beznea@tuxon.dev>
Date:   Sun, 26 Nov 2023 16:10:46 +0200
From:   Claudiu Beznea <claudiu.beznea@...on.dev>
To:     nicolas.ferre@...rochip.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        andrew@...n.ch, hkallweit1@...il.com, linux@...linux.org.uk,
        jgarzik@...ox.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Claudiu Beznea <claudiu.beznea@...on.dev>
Subject: [PATCH 2/2] net: macb: Unregister nedev before MDIO bus in remove

unregister_netdev() calls the struct net_device_ops::ndo_stop function,
which in the case of the macb driver is macb_close(). macb_close() calls,
in turn, PHY-specific APIs (e.g., phy_detach()). The call trace is as
follows:

macb_close() ->
  phylink_disconnect_phy() ->
    phy_disconnect() ->
      phy_detach()

phy_detach() will remove associated sysfs files by calling
kernfs_remove_by_name_ns(), which will hit
"kernfs: cannot remove 'attached_dev', no directory" WARN(), which will
throw a stack trace too.

To avoid this, call unregiser_netdev() before mdiobus_unregister() and
mdiobus_free().

Fixes: 7897b071ac3b ("net: macb: convert to phylink")
Signed-off-by: Claudiu Beznea <claudiu.beznea@...on.dev>
---
 drivers/net/ethernet/cadence/macb_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index cebae0f418f2..73d041af3de1 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -5165,11 +5165,11 @@ static void macb_remove(struct platform_device *pdev)
 
 	if (dev) {
 		bp = netdev_priv(dev);
+		unregister_netdev(dev);
 		phy_exit(bp->sgmii_phy);
 		mdiobus_unregister(bp->mii_bus);
 		mdiobus_free(bp->mii_bus);
 
-		unregister_netdev(dev);
 		tasklet_kill(&bp->hresp_err_tasklet);
 		pm_runtime_disable(&pdev->dev);
 		pm_runtime_dont_use_autosuspend(&pdev->dev);
-- 
2.39.2