Lockless uidinfo.

[Alfred Perlstein]

* Pawel Jakub Dawidek <pjd at FreeBSD.org> [070818 07:59] wrote:
> On Sat, Aug 18, 2007 at 07:23:37AM -0700, Alfred Perlstein wrote:
> > * Pawel Jakub Dawidek <pjd at FreeBSD.org> [070818 05:31] wrote:
> > > Hi.
> > > 
> > > The patch below remove per-uidinfo locks:
> > > 
> > > 	http://people.freebsd.org/~pjd/patches/uidinfo_lockless.patch
> > 
> > In uifree() is it ok to manually check the refcount for 0?
> > 
> > I'm gussing the hashmtx is used as a barrier?
> 
> Yes, to lookup uidinfo you need to hold uihashtbl_mtx mutex, so once you
> hold it and ui_ref is 0, noone will be able to reference it, because it
> has to wait to look it up.

And the field doesn't need to be volatile to prevent cached/opportunitic
reads?


-- 
- Alfred Perlstein