Re: USB4 thunderbolt device suspend/resume problems. Unplug during suspend.

[Lukas Wunner <lukas@wunner.de>]

On Sat, Mar 22, 2025 at 01:38:34PM +0000, James Dutton wrote:
> > On Mon, Feb 17, 2025 at 08:44:19PM +0000, James Dutton wrote:
> > > I have a thunderbolt / usb4 10Gbps ethernet adapter.
> > > While plugged in, it appears to handle suspend and resume OK.
> > > The problem is the following:
> > > 1) Thunderbolt device plugged in. Device appears in "lscpi".
> > > 2) Suspend Laptop
> > > 3) Unplug the device while it is asleep.
> > > 4) Resume the Laptop
> > > 5) Laptop locks up, no stack trace, nothing output.
> 
> I found something that worked for me.
> I found an infinite loop and adding a timeout to it fixed my problem:
> E.g.
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -6840,8 +6841,16 @@ void napi_disable(struct napi_struct *n)
>         do {
>                 while (val & (NAPIF_STATE_SCHED | NAPIF_STATE_NPSVC)) {
>                         usleep_range(20, 200);
> +                       loop_counter++;
> +                       if (loop_counter > 625) {
> +                               break;
> +                       }
>                         val = READ_ONCE(n->state);
>                 }
> +               if (loop_counter > 625) {
> +                       pr_warn("dev.c:napi_disable() timed out\n");
> +                       break;
> +               }
> 
>                 new = val | NAPIF_STATE_SCHED | NAPIF_STATE_NPSVC;
>                 new &= ~(NAPIF_STATE_THREADED | NAPIF_STATE_PREFER_BUSY_POLL);

I'm afraid that's a hack, not a proper fix.  You can insert a call
to "dump_stack();" before the "break;" to see where the call to
napi_disable() is coming from.

It seems the driver of the network adapter built into the dock
gets confused if the adapter is no longer present on resume.
It would be good if you could report this to the maintainers of that
driver and/or netdev maintainers, as well as netdev@vger.kernel.org.

Thanks,

Lukas