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Message-ID: <20240416135129.GM2320920@kernel.org>
Date: Tue, 16 Apr 2024 14:51:29 +0100
From: Simon Horman <horms@...nel.org>
To: Lukas Wunner <lukas@...ner.de>
Cc: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Jesse Brandeburg <jesse.brandeburg@...el.com>,
Tony Nguyen <anthony.l.nguyen@...el.com>,
intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
Roman Lozko <lozko.roma@...il.com>,
Kurt Kanzenbach <kurt@...utronix.de>,
Heiner Kallweit <hkallweit1@...il.com>,
Andrew Lunn <andrew@...n.ch>, Sasha Neftin <sasha.neftin@...el.com>
Subject: Re: [PATCH net] igc: Fix LED-related deadlock on driver unbind
On Mon, Apr 15, 2024 at 03:48:48PM +0200, 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@...il.com>
> Closes: https://lore.kernel.org/r/CAEhC_B=ksywxCG_+aQqXUrGEgKq+4mqnSV8EBHOKbC3-Obj9+Q@mail.gmail.com/
> Signed-off-by: Kurt Kanzenbach <kurt@...utronix.de>
> Signed-off-by: Lukas Wunner <lukas@...ner.de>
> Cc: Heiner Kallweit <hkallweit1@...il.com>
I am aware that Kurt has submitted what appears to be the same patch [1,2],
which I'm inclined to put down to miscommunication (email based workflows
are like that sometimes).
FWIIW, it is my understanding is that the patch originated from
Lukas[3], and thus it seems most appropriate to take his submission.
As for the patch itself, I agree that it addresses the problem at hand.
For the record, I have not tested it.
Reviewed-by: Simon Horman <horms@...nel.org>
[1] [PATCH iwl-net] igc: Fix deadlock on module removal
https://lore.kernel.org/netdev/20240411-igc_led_deadlock-v1-1-0da98a3c68c5@linutronix.de/
[2] [PATCH iwl-net v2] igc: Fix deadlock on module removal
https://lore.kernel.org/netdev/20240411-igc_led_deadlock-v2-1-b758c0c88b2b@linutronix.de/
[3] Re: Deadlock in pciehp on dock disconnect
https://lore.kernel.org/all/ZhBN9p1yOyciXkzw@wunner.de/
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