Re: Locking model for NAPI drivers

[Andi Kleen <ak@xxxxxx>]

"David S. Miller" <davem@xxxxxxxxxxxxx> writes:

Stupid question, but...

> I was doing some brainstorming to try and fix a nagging problem in
> the tg3 driver which suggested that doing the SMP locking differently
> might be the best and cleanest solution.
>
> The tg3 problem is that it can do an skb_copy() in HW IRQ disabled
> context which is illegal.

That is because of the kmap_atomic it does right? At least in the i386
highmem implementation I don't see any code that would be less safe in
hard interrupt context compared to BHs.  And FRV and mips look like they
allow it too.

> This fixes the skb_copy() we were doing with hw
> IRQs disabled (which is illegal and triggers a
> BUG() with HIGHMEM enabled).  

Which BUG did it trigger?

-Andi