Re: [PATCH net] igc: Fix LED-related deadlock on driver unbind

[Kurt Kanzenbach <kurt@linutronix.de>]

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On Mon Apr 15 2024, Lukas Wunner wrote:
> Roman reports a deadlock on unplug of a Thunderbolt docking station
> containing an Intel I225 Ethernet adapter.
>
> The root cause is that led_classdev's for LEDs on the adapter are
> registered such that they're device-managed by the netdev.  That
> results in recursive acquisition of the rtnl_lock() mutex on unplug:
>
> When the driver calls unregister_netdev(), it acquires rtnl_lock(),
> then frees the device-managed resources.  Upon unregistering the LEDs,
> netdev_trig_deactivate() invokes unregister_netdevice_notifier(),
> which tries to acquire rtnl_lock() again.
>
> Avoid by using non-device-managed LED registration.
>
> Stack trace for posterity:
>
>   schedule+0x6e/0xf0
>   schedule_preempt_disabled+0x15/0x20
>   __mutex_lock+0x2a0/0x750
>   unregister_netdevice_notifier+0x40/0x150
>   netdev_trig_deactivate+0x1f/0x60 [ledtrig_netdev]
>   led_trigger_set+0x102/0x330
>   led_classdev_unregister+0x4b/0x110
>   release_nodes+0x3d/0xb0
>   devres_release_all+0x8b/0xc0
>   device_del+0x34f/0x3c0
>   unregister_netdevice_many_notify+0x80b/0xaf0
>   unregister_netdev+0x7c/0xd0
>   igc_remove+0xd8/0x1e0 [igc]
>   pci_device_remove+0x3f/0xb0
>
> Fixes: ea578703b03d ("igc: Add support for LEDs on i225/i226")
> Reported-by: Roman Lozko <lozko.roma@gmail.com>
> Closes: https://lore.kernel.org/r/CAEhC_B=ksywxCG_+aQqXUrGEgKq+4mqnSV8EBHOKbC3-Obj9+Q@mail.gmail.com/
> Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>

I think, the first SoB has to be yours, because you are the patch
author. In fact, my SoB is not required at all.

However, feel free to add:

Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
Tested-by: Kurt Kanzenbach <kurt@linutronix.de> # Intel i225

Thanks,
Kurt

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