Re: [PATCH net-next v1 1/1] net: usb: lan78xx: fix WARN in __netif_napi_del_locked on disconnect

[Oleksij Rempel]

On Mon, Jun 23, 2025 at 04:55:37PM -0700, Jakub Kicinski wrote:
> On Fri, 20 Jun 2025 10:51:44 +0200 Oleksij Rempel wrote:
> > A WARN may be triggered in __netif_napi_del_locked() during USB device
> > disconnect:
> > 
> >   WARNING: CPU: 0 PID: 11 at net/core/dev.c:7417 __netif_napi_del_locked+0x2b4/0x350
> > 
> > This occurs because NAPI remains enabled when the device is unplugged and
> > teardown begins. While `napi_disable()` was previously called in the
> > `lan78xx_stop()` path, that function is not invoked on disconnect. Instead,
> > when using PHYLINK, the `mac_link_down()` callback is guaranteed to run
> > during disconnect, making it the correct place to disable NAPI.
> > 
> > Similarly, move `napi_enable()` to `mac_link_up()` to pair the lifecycle
> > with actual MAC state.
> 
> Stopping and starting NAPI on link events is pretty unusual.
> The problem is the disconnect handling, unregistering netdev
> removes the NAPIs automatically, I think all you need is to
> remove the explicit netif_napi_del() in lan78xx_disconnect().
> Core will call _stop (which disables the NAPI), and then
> it will del the NAPI.

ack.

> > This patch is intended for `net-next` since the issue existed before the
> > PHYLINK migration, but is more naturally and cleanly addressed now that
> > PHYLINK manages link state transitions.
> 
> And repost that for net, please.. :)

It will be not compatible with the PHYlink migration patch in the
net-next. Should i wait until PHYlink patch goes to the net and then
send different patch variants for stable before PHYlink migration and
after?

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