request for review: backport of sx and rwlocks from 7.0 to 6-stable

[Kris Kennaway]

Alfred Perlstein wrote:
> Hi guys,
> 
> Some work here at work was approved for sharing with community so
> I'm posting it here in hope of a review.
> 
> We run some pretty good stress testing on our code, so I think it's
> pretty solid.
> 
> My only concern is that I've tried my best to preserve kernel source
> API, but not binary compat though a few simple #defines.
> 
> I can make binary compat, in albeit a somewhat confusing manner, but
> that will require some rototilling and weird renaming of calls to
> the sleepq and turnstile code.  In short, I'd rather not, but I will
> if you think it's something that should be done.
> 
> There's also a few placeholders for lock profiling which I will
> very likely be backporting shortly as well.
> 
> Patch is attached.
> 
> Comments/questions?

Hmm, I would be happy to see this but I think binary compatibility is 
actually important here since this is -stable and low-level primitives 
like sx are probably used all over the place in existing third party 
modules.

Kris