Re: [PATCH net] net: phy: Don't register LEDs for genphy

["Russell King (Oracle)" <linux@armlinux.org.uk>]

On Mon, Jul 07, 2025 at 03:58:03PM -0400, Sean Anderson wrote:
> If a PHY has no driver, the genphy driver is probed/removed directly in
> phy_attach/detach. If the PHY's ofnode has an "leds" subnode, then the
> LEDs will be (un)registered when probing/removing the genphy driver.

Maybe checking whether the PHY driver supports LEDs would be more
sensible than checking whether it's one of the genphy drivers?

> This could occur if the leds are for a non-generic driver that isn't
> loaded for whatever reason. Synchronously removing the PHY device in
> phy_detach leads to the following deadlock:
> 
> rtnl_lock()
> ndo_close()
>     ...
>     phy_detach()
>         phy_remove()
>             phy_leds_unregister()
>                 led_classdev_unregister()
>                     led_trigger_set()
>                         netdev_trigger_deactivate()
>                             unregister_netdevice_notifier()
>                                 rtnl_lock()
> 
> There is a corresponding deadlock on the open/register side of things
> (and that one is reported by lockdep), but it requires a race while this
> one is deterministic.

Doesn't this deadlock exist irrespective of whether the genphy driver(s)
are being used, and whether or not the PHY driver supports LEDs?

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