Memory transaction instructions

[David Howells]

Hi Linus,

I'm not sure how relevant it is to the topic, but I seem to remember you
having a go at implementing spinlocks with x86_64 memory transaction
instructions a while back.  Do you have any thoughts on whether these
instructions are ever likely to become something we can use?

I was looking specifically at the skbuff queue stuff which does {
spin_lock_irq, add to list, inc count, spin_unlock_irq } and thinking that
might be a good place to use such a thing.

David