From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 2 Jan 2014 14:47:44 -0800

You could use spin_lock_bh(), but if it's true that it's all in a
softirq context, I think it should be safe to just do "spin_lock()".
Afaik, there is nothing that actually does anything in real hardirq
context in there. I *think* all the network _rcv() functions are
called from softirqs, right?

I'm worried that mixing hardIRQ locking (via the direct calls to
skb_dequeue() et al.) with explicit softIRQ locking will make lockdep
complain.