Re: [PATCH nf-next v2 3/3] netfilter: nft_set_pipapo: Use nested-BH locking for nft_pipapo_scratch

[Florian Westphal <fw@strlen.de>]

Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
> > Not sure this is correct.  If RT allows to migrate in BH before
> > the local lock is taken, then the if (unlikely(!irq_fpu_usable()))
> > check needs to be done after the local lock was taken, no?
> 
> Looking at this again, that irq_fpu_usable() itself looks slightly
> placed at the wrong spot. It should be
> |	if (!irq_fpu_usable())
> |		return fallback_variant(); 
> |	local_bh_disable();
> 
> The reason is that if you expect calls from hardirq context then you
> shouldn't disable BH. Lockdep enabled kernels should complain in this
> case. But then this is networking and I would expect everything here
> should be injected via NAPI/ softirq (either via driver's NAPI or
> backlog's).

This is never called from hardirq context, its always process context
or softirq.  Are you saying that the irq_fpu_usable() is bogus
and can be axed?

> I've just started rebasing this patch on top of the testing branch. I
> see that you moved that code a bit around. I can't acquire the
> local_lock_t within kernel_fpu_begin(). I would need to move this back
> to pipapo_get_avx2().

Sure, I don't see why it can't be moved back to pipapo_get_avx2().

You can also just resubmit vs. nf-next main and I can rebase my
patches on top of the local_lock changes, up to you.