netdev - Re: [PATCH iwl-net v2] igc: Fix deadlock on module removal

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Message-ID: <20240416135129.GA3769813@kernel.org>
Date: Tue, 16 Apr 2024 14:51:29 +0100
From: Simon Horman <horms@...nel.org>
To: Kurt Kanzenbach <kurt@...utronix.de>
Cc: Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Andrew Lunn <andrew@...n.ch>, Lukas Wunner <lukas@...ner.de>,
	Sasha Neftin <sasha.neftin@...el.com>,
	Roman Lozko <lozko.roma@...il.com>,
	Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>,
	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org
Subject: Re: [PATCH iwl-net v2] igc: Fix deadlock on module removal

On Mon, Apr 15, 2024 at 12:59:37PM +0200, Kurt Kanzenbach wrote:
> From: Lukas Wunner <lukas@...ner.de>
> 
> The removal of the igc module leads to a deadlock:
> 
> |[Mon Apr  8 17:38:55 2024]  __mutex_lock.constprop.0+0x3e5/0x7a0
> |[Mon Apr  8 17:38:55 2024]  ? preempt_count_add+0x85/0xd0
> |[Mon Apr  8 17:38:55 2024]  __mutex_lock_slowpath+0x13/0x20
> |[Mon Apr  8 17:38:55 2024]  mutex_lock+0x3b/0x50
> |[Mon Apr  8 17:38:55 2024]  rtnl_lock+0x19/0x20
> |[Mon Apr  8 17:38:55 2024]  unregister_netdevice_notifier+0x2a/0xc0
> |[Mon Apr  8 17:38:55 2024]  netdev_trig_deactivate+0x25/0x70
> |[Mon Apr  8 17:38:55 2024]  led_trigger_set+0xe2/0x2d0
> |[Mon Apr  8 17:38:55 2024]  led_classdev_unregister+0x4f/0x100
> |[Mon Apr  8 17:38:55 2024]  devm_led_classdev_release+0x15/0x20
> |[Mon Apr  8 17:38:55 2024]  release_nodes+0x47/0xc0
> |[Mon Apr  8 17:38:55 2024]  devres_release_all+0x9f/0xe0
> |[Mon Apr  8 17:38:55 2024]  device_del+0x272/0x3c0
> |[Mon Apr  8 17:38:55 2024]  netdev_unregister_kobject+0x8c/0xa0
> |[Mon Apr  8 17:38:55 2024]  unregister_netdevice_many_notify+0x530/0x7c0
> |[Mon Apr  8 17:38:55 2024]  unregister_netdevice_queue+0xad/0xf0
> |[Mon Apr  8 17:38:55 2024]  unregister_netdev+0x21/0x30
> |[Mon Apr  8 17:38:55 2024]  igc_remove+0xfb/0x1f0 [igc]
> |[Mon Apr  8 17:38:55 2024]  pci_device_remove+0x42/0xb0
> |[Mon Apr  8 17:38:55 2024]  device_remove+0x43/0x70
> 
> unregister_netdev() acquires the RNTL lock and releases the LEDs bound
> to that netdevice. However, netdev_trig_deactivate() and later
> unregister_netdevice_notifier() try to acquire the RTNL lock again.
> 
> Avoid this situation by not using the device-managed LED class
> functions.
> 
> Link: https://lore.kernel.org/r/CAEhC_B=ksywxCG_+aQqXUrGEgKq+4mqnSV8EBHOKbC3-Obj9+Q@mail.gmail.com/
> Link: https://lore.kernel.org/r/ZhRD3cOtz5i-61PB@mail-itl/
> Reported-by: Roman Lozko <lozko.roma@...il.com>
> Reported-by: "Marek Marczykowski-Górecki" <marmarek@...isiblethingslab.com>
> Fixes: ea578703b03d ("igc: Add support for LEDs on i225/i226")
> Signed-off-by: Lukas Wunner <lukas@...ner.de>
> [Kurt: Wrote commit message and tested on i225]
> Signed-off-by: Kurt Kanzenbach <kurt@...utronix.de>

I am aware that this patch seems to have also been submitted by Lucas
himself. I'd like to suggest that we focus on review of that submission.

https://lore.kernel.org/netdev/2f1be6b1cf2b3346929b0049f2ac7d7d79acb5c9.1713188539.git.lukas@wunner.de/