linux-kernel - [PATCH net v1] net: usbnet: Fix the wrong netif_carrier

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Message-Id: <20250801182044.39420-1-ammarfaizi2@gnuweeb.org>
Date: Sat,  2 Aug 2025 01:20:44 +0700
From: Ammar Faizi <ammarfaizi2@...weeb.org>
To: Oliver Neukum <oneukum@...e.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Ammar Faizi <ammarfaizi2@...weeb.org>,
	John Ernberg <john.ernberg@...ia.se>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linux Netdev Mailing List <netdev@...r.kernel.org>,
	Linux USB Mailing List <linux-usb@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Armando Budianto <sprite@...weeb.org>,
	gwml@...r.gnuweeb.org,
	stable@...r.kernel.org
Subject: [PATCH net v1] net: usbnet: Fix the wrong netif_carrier_on() call placement

The commit in the Fixes tag breaks my laptop (found by git bisect).
My home RJ45 LAN cable cannot connect after that commit.

The call to netif_carrier_on() should be done when netif_carrier_ok()
is false. Not when it's true. Because calling netif_carrier_on() when
__LINK_STATE_NOCARRIER is not set actually does nothing.

Cc: Armando Budianto <sprite@...weeb.org>
Cc: stable@...r.kernel.org
Closes: https://lore.kernel.org/netdev/0752dee6-43d6-4e1f-81d2-4248142cccd2@gnuweeb.org
Fixes: 0d9cfc9b8cb1 ("net: usbnet: Avoid potential RCU stall on LINK_CHANGE event")
Signed-off-by: Ammar Faizi <ammarfaizi2@...weeb.org>
---
 drivers/net/usb/usbnet.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index bc1d8631ffe0..1eb98eeb64f9 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1107,31 +1107,31 @@ static const struct ethtool_ops usbnet_ethtool_ops = {
 };
 
 /*-------------------------------------------------------------------------*/
 
 static void __handle_link_change(struct usbnet *dev)
 {
 	if (!test_bit(EVENT_DEV_OPEN, &dev->flags))
 		return;
 
 	if (!netif_carrier_ok(dev->net)) {
+		if (test_and_clear_bit(EVENT_LINK_CARRIER_ON, &dev->flags))
+			netif_carrier_on(dev->net);
+
 		/* kill URBs for reading packets to save bus bandwidth */
 		unlink_urbs(dev, &dev->rxq);
 
 		/*
 		 * tx_timeout will unlink URBs for sending packets and
 		 * tx queue is stopped by netcore after link becomes off
 		 */
 	} else {
-		if (test_and_clear_bit(EVENT_LINK_CARRIER_ON, &dev->flags))
-			netif_carrier_on(dev->net);
-
 		/* submitting URBs for reading packets */
 		tasklet_schedule(&dev->bh);
 	}
 
 	/* hard_mtu or rx_urb_size may change during link change */
 	usbnet_update_max_qlen(dev);
 
 	clear_bit(EVENT_LINK_CHANGE, &dev->flags);
 }
 
-- 
Ammar Faizi