Re: 6.12-rc1: Lockdep regression bissected (virtio-net/console/scheduler)

[Breno Leitao]

On Thu, Oct 03, 2024 at 07:51:20AM -0700, Breno Leitao wrote:
> Upstream kernel (6.12-rc1) has a new lockdep splat, that I am sharing to
> get more visibility:
> 
> 	WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
> 
> This is happening because the HARDIRQ-irq-unsafe "_xmit_ETHER#2" lock is
> acquired in virtnet_poll_tx() while holding the HARDIRQ-irq-safe, and
> lockdep doesn't like it much.
> 
> I've bisected the problem, and weirdly enough, this problem started to
> show up after a unrelated(?) change in the scheduler:
> 
> 	52e11f6df293e816a ("sched/fair: Implement delayed dequeue")

Errata. The commit is missing the first number. The right one is:

	152e11f6df293e816a ("sched/fair: Implement delayed dequeue")