[Intel-gfx] [PATCH] drm/vblank: Fixup and document timestamp update/read barriers

[Daniel Vetter]

On Thu, Apr 16, 2015 at 05:00:02AM -0400, Peter Hurley wrote:
> On 04/16/2015 02:39 AM, Mario Kleiner wrote:
> > I think i'm still not getting something about why the compiler would
> > be allowed to reorder in this way in absence of the additional
> > smp_rmb? Or is that barrier required for other archs which are less
> > strongly ordered?
> 
> Apologies for the confusion; I missed that it was data-dependent load.

Oh right missed that too. Well, alpha can do anything, we'd need at least
a read_barrier_depends(); here. Tbh not sure that's worth it since with
the plain smp_rmb() we match the seqlock code exactly.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch