From 0bfcb0a36c9dbfc8b7a8ab8ade100cad4d7628b4 Mon Sep 17 00:00:00 2001 From: Shiji Yang Date: Sun, 22 Feb 2026 10:52:20 +0800 Subject: [PATCH] kernel: net: fix deadlock caused by phy led trigger Register phy led_triggers earlier to avoid AB-BA deadlock. Fixes: https://github.com/openwrt/openwrt/issues/18472 Signed-off-by: Shiji Yang Link: https://github.com/openwrt/openwrt/pull/22136 Signed-off-by: Robert Marko --- ...-phy-led_triggers-during-probe-to-av.patch | 116 ++++++++++++++++++ 1 file changed, 116 insertions(+) create mode 100644 target/linux/generic/pending-6.12/704-net-phy-register-phy-led_triggers-during-probe-to-av.patch diff --git a/target/linux/generic/pending-6.12/704-net-phy-register-phy-led_triggers-during-probe-to-av.patch b/target/linux/generic/pending-6.12/704-net-phy-register-phy-led_triggers-during-probe-to-av.patch new file mode 100644 index 00000000000..126275c7ecb --- /dev/null +++ b/target/linux/generic/pending-6.12/704-net-phy-register-phy-led_triggers-during-probe-to-av.patch @@ -0,0 +1,116 @@ +From 5225349f1e750dfd107a4c5dc97d91fa212dc1ed Mon Sep 17 00:00:00 2001 +From: Andrew Lunn +Date: Sat, 21 Feb 2026 14:51:54 -0600 +Subject: [PATCH] net: phy: register phy led_triggers during probe to avoid + AB-BA deadlock + +There is an AB-BA deadlock when both LEDS_TRIGGER_NETDEV and +LED_TRIGGER_PHY are enabled: + +[ 1362.049207] [<8054e4b8>] led_trigger_register+0x5c/0x1fc <-- Trying to get lock "triggers_list_lock" via down_write(&triggers_list_lock); +[ 1362.054536] [<80662830>] phy_led_triggers_register+0xd0/0x234 +[ 1362.060329] [<8065e200>] phy_attach_direct+0x33c/0x40c +[ 1362.065489] [<80651fc4>] phylink_fwnode_phy_connect+0x15c/0x23c +[ 1362.071480] [<8066ee18>] mtk_open+0x7c/0xba0 +[ 1362.075849] [<806d714c>] __dev_open+0x280/0x2b0 +[ 1362.080384] [<806d7668>] __dev_change_flags+0x244/0x24c +[ 1362.085598] [<806d7698>] dev_change_flags+0x28/0x78 +[ 1362.090528] [<807150e4>] dev_ioctl+0x4c0/0x654 <-- Hold lock "rtnl_mutex" by calling rtnl_lock(); +[ 1362.094985] [<80694360>] sock_ioctl+0x2f4/0x4e0 +[ 1362.099567] [<802e9c4c>] sys_ioctl+0x32c/0xd8c +[ 1362.104022] [<80014504>] syscall_common+0x34/0x58 + +Here LED_TRIGGER_PHY is registering LED triggers during phy_attach +while holding RTNL and then taking triggers_list_lock. + +[ 1362.191101] [<806c2640>] register_netdevice_notifier+0x60/0x168 <-- Trying to get lock "rtnl_mutex" via rtnl_lock(); +[ 1362.197073] [<805504ac>] netdev_trig_activate+0x194/0x1e4 +[ 1362.202490] [<8054e28c>] led_trigger_set+0x1d4/0x360 <-- Hold lock "triggers_list_lock" by down_read(&triggers_list_lock); +[ 1362.207511] [<8054eb38>] led_trigger_write+0xd8/0x14c +[ 1362.212566] [<80381d98>] sysfs_kf_bin_write+0x80/0xbc +[ 1362.217688] [<8037fcd8>] kernfs_fop_write_iter+0x17c/0x28c +[ 1362.223174] [<802cbd70>] vfs_write+0x21c/0x3c4 +[ 1362.227712] [<802cc0c4>] ksys_write+0x78/0x12c +[ 1362.232164] [<80014504>] syscall_common+0x34/0x58 + +Here LEDS_TRIGGER_NETDEV is being enabled on an LED. It first takes +triggers_list_lock and then RTNL. A classical AB-BA deadlock. + +phy_led_triggers_registers() does not require the RTNL, it does not +make any calls into the network stack which require protection. There +is also no requirement the PHY has been attached to a MAC, the +triggers only make use of phydev state. This allows the call to +phy_led_triggers_registers() to be placed elsewhere. PHY probe() and +release() don't hold RTNL, so solving the AB-BA deadlock. + +Reported-by: Shiji Yang +Closes: https://lore.kernel.org/all/OS7PR01MB13602B128BA1AD3FA38B6D1FFBC69A@OS7PR01MB13602.jpnprd01.prod.outlook.com/ +Fixes: 06f502f57d0d ("leds: trigger: Introduce a NETDEV trigger") +Signed-off-by: Andrew Lunn +--- + drivers/net/phy/phy_device.c | 25 +++++++++++++++++-------- + 1 file changed, 17 insertions(+), 8 deletions(-) + +--- a/drivers/net/phy/phy_device.c ++++ b/drivers/net/phy/phy_device.c +@@ -1684,8 +1684,6 @@ int phy_attach_direct(struct net_device + goto error; + + phy_resume(phydev); +- if (!phydev->is_on_sfp_module) +- phy_led_triggers_register(phydev); + + /** + * If the external phy used by current mac interface is managed by +@@ -2058,9 +2056,6 @@ void phy_detach(struct phy_device *phyde + } + phydev->phylink = NULL; + +- if (!phydev->is_on_sfp_module) +- phy_led_triggers_unregister(phydev); +- + if (phydev->mdio.dev.driver) + module_put(phydev->mdio.dev.driver->owner); + +@@ -3691,17 +3686,28 @@ static int phy_probe(struct device *dev) + /* Set the state to READY by default */ + phydev->state = PHY_READY; + ++ /* Register the PHY LED triggers */ ++ if (!phydev->is_on_sfp_module) ++ phy_led_triggers_register(phydev); ++ + /* Get the LEDs from the device tree, and instantiate standard + * LEDs for them. + */ + if (IS_ENABLED(CONFIG_PHYLIB_LEDS) && !phy_driver_is_genphy(phydev) && +- !phy_driver_is_genphy_10g(phydev)) ++ !phy_driver_is_genphy_10g(phydev)) { + err = of_phy_leds(phydev); ++ if (err) ++ goto out; ++ } ++ ++ return 0; + + out: ++ if (!phydev->is_on_sfp_module) ++ phy_led_triggers_unregister(phydev); ++ + /* Re-assert the reset signal on error */ +- if (err) +- phy_device_reset(phydev, 1); ++ phy_device_reset(phydev, 1); + + return err; + } +@@ -3716,6 +3722,9 @@ static int phy_remove(struct device *dev + !phy_driver_is_genphy_10g(phydev)) + phy_leds_unregister(phydev); + ++ if (!phydev->is_on_sfp_module) ++ phy_led_triggers_unregister(phydev); ++ + phydev->state = PHY_DOWN; + + sfp_bus_del_upstream(phydev->sfp_bus); -- 2.47.3