Re: "Dead loop on virtual device" error without softirq-BKL on PREEMPT_RT

[Sebastian Andrzej Siewior]

On 2026-04-02 09:50:35 [+0200], Daniel Vacek wrote:
> My idea was that the non-preemptible one can record `current` task
> instead of the CPU to detect the deadlock. And that would also work
> for the preemptible case (it would actually match the lock owner
> approach as you did for the PREEMPT_RT case).
> One code for both configurations, no special-casing. I'd argue that's
> a better result. Am I missing something?
> 
> The size of the netdev_queue structure would grow by 8 bytes for !RT
> case, but that's not a big deal, IMO. For RT case it would just fill
> the hole.

We have xmit_lock_owner as int. If you replace it with task_struct *
then on 64bit the size of the struct netdev_queue will remain unchanged
as it fills the hole before the following long.
Then you could record `current' as the lock owner in both cases. This
should work.

> --nX

Sebastian