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

From: Simon Horman <[email-masked]>
Date: Tue, 16 Apr 2024 14:51:29 +0100

On Mon, Apr 15, 2024 at 12:59:37PM +0200, Kurt Kanzenbach wrote:
> From: Lukas Wunner <[email-masked]>
> 
> 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=[email-masked]/
> Link: https://lore.kernel.org/r/ZhRD3cOtz5i-61PB@mail-itl/
> Reported-by: Roman Lozko <[email-masked]>
> Reported-by: "Marek Marczykowski-Górecki" <[email-masked]>
> Fixes: ea578703b03d ("igc: Add support for LEDs on i225/i226")
> Signed-off-by: Lukas Wunner <[email-masked]>
> [Kurt: Wrote commit message and tested on i225]
> Signed-off-by: Kurt Kanzenbach <[email-masked]>

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/[email-masked]/