From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from vps0.lunn.ch (vps0.lunn.ch [156.67.10.101]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3CFAB246BC5; Sat, 21 Feb 2026 23:48:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=156.67.10.101 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771717703; cv=none; b=ArGj5eR9seC4F14MLVHHF3lBlESPJeNerv46PXE7gR8pc7PdrkRFHKTBYHqLI/d4RslOKWs5IbXC4JSGz06C1r7TY0QUg3AbF9JANiuuIyHn9lVwicl/djUJjE8ElwDDcHDNOsLbqGNklFySgLMBUOmyE4SXJ4OpXdQyJ7YBbqw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771717703; c=relaxed/simple; bh=r/1igpAeLfqEQf9V6lp5MskObr/YMh4Ed/3c48G7YUA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=UROLCZYwdYCXhDBSk58Lyiy/PrHxufV2OxYCRJzwHPzenQxxUvB1d8bK+QUmC0kmouvR3bc6XxhXI0iNwsAEb9TTMZmNajy4SFvSXaV5L/rV9W679VnJQjTrdmcy/5vPXYt1dGZ5Dx40Ojz7EqFK3mHBZoipzoeTd9iQ7mCvu0g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lunn.ch; spf=pass smtp.mailfrom=lunn.ch; dkim=pass (1024-bit key) header.d=lunn.ch header.i=@lunn.ch header.b=3P/6g61S; arc=none smtp.client-ip=156.67.10.101 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lunn.ch Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lunn.ch Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=lunn.ch header.i=@lunn.ch header.b="3P/6g61S" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch; s=20171124; h=In-Reply-To:Content-Disposition:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:From:Sender:Reply-To:Subject: Date:Message-ID:To:Cc:MIME-Version:Content-Type:Content-Transfer-Encoding: Content-ID:Content-Description:Content-Disposition:In-Reply-To:References; bh=881Fec93wJCf42xpIv7Iov5yx2p1EBID71tnMJjcPzc=; b=3P/6g61SFTnwtuzCUQwElYcibr t7+/c6lZ4uMzBYjfN3WzUIFDTJKZ0CBF7+qpTZyzbm1M7LxqHeOHX7ICi7RxhLUS03QXpsBU5UeOP KWCfs0sTak4bZGpM3pe/IzBfERkiZcrQCDlV++2zYDoejktgWn5rt8Up1iLTMli2EOpM=; Received: from andrew by vps0.lunn.ch with local (Exim 4.94.2) (envelope-from ) id 1vtwho-008DSp-9s; Sun, 22 Feb 2026 00:48:12 +0100 Date: Sun, 22 Feb 2026 00:48:12 +0100 From: Andrew Lunn To: Shiji Yang Cc: linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Lee Jones , Pavel Machek , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Subject: Re: [BUG] AB-BA deadlock between net and led-trigger module Message-ID: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Sat, Feb 21, 2026 at 06:01:46PM +0800, Shiji Yang wrote: > The OpenWrt community reports that sometimes devices fail to start[1] > on 5.15 kernel. After further tracking, this is caused by a AB-BA > deadlock which can be reproduced in at least 5.15, 6.6, 6.12 and latest > 6.18 LTS kenrel. Hi Shiji Please could you test this patch. It is based on the net tree, but with a bit of fuzz will probably apply to older trees. Thanks Andrew >From bf4d66187585a1893d558cb9357f1ef63437b898 Mon Sep 17 00:00:00 2001 From: Andrew Lunn Date: Sat, 21 Feb 2026 14:51:54 -0600 Subject: [PATCH net] 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(-) diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c index 9b8eaac63b90..cbb4af604aa5 100644 --- a/drivers/net/phy/phy_device.c +++ b/drivers/net/phy/phy_device.c @@ -1866,8 +1866,6 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev, 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 @@ -1982,9 +1980,6 @@ void phy_detach(struct phy_device *phydev) phydev->phy_link_change = NULL; 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); @@ -3778,16 +3773,27 @@ 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)) + if (IS_ENABLED(CONFIG_PHYLIB_LEDS) && !phy_driver_is_genphy(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; } @@ -3801,6 +3807,9 @@ static int phy_remove(struct device *dev) if (IS_ENABLED(CONFIG_PHYLIB_LEDS) && !phy_driver_is_genphy(phydev)) phy_leds_unregister(phydev); + if (!phydev->is_on_sfp_module) + phy_led_triggers_unregister(phydev); + phydev->state = PHY_DOWN; phy_cleanup_ports(phydev); -- 2.51.0