netdev - Re: NPD in phy_led_set

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Date: Wed, 7 Jun 2023 23:32:52 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Florian Fainelli <f.fainelli@...il.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Christian Marangi <ansuelsmth@...il.com>,
	Vladimir Oltean <olteanv@...il.com>, Pavel Machek <pavel@....cz>,
	Lee Jones <lee@...nel.org>,
	"linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>
Subject: Re: NPD in phy_led_set_brightness+0x3c

> There is no trigger being configured for either LED therefore it is not
> clear to me why the workqueue is being kicked in the first place?

Since setting LEDs is a sleepable action, it gets offloaded to a
workqueue.

My guess is, something in led_classdev_unregister() is triggering it,
maybe to put the LED into a known state before pulling the
plug. However, i don't see what.

I'm also wondering about ordering. The LED is registered with
devm_led_classdev_register_ext(). So maybe led_classdev_unregister()
is getting called too late? So maybe we need to replace devm_ with
manual cleanup.

However, i've done lots of reboots while developing this code, so its
interesting you can trigger this, and i've not seen it.

	    Andrew