Re: [PATCH] 2.5.1-pre5: per-cpu areas

[Rusty Russell]

In message <[e-mail]> you write:
> On Sun, Mar 17, 2002 at 06:17:32PM +1100, Rusty Russell wrote:
> > On Fri, 15 Mar 2002 10:13:09 +0100
> > Andi Kleen <[e-mail]> wrote:
> > 
> > > On Fri, Mar 15, 2002 at 03:07:27PM +1100, Rusty Russell wrote:
> > > > They must return an lvalue, otherwise they're useless for 50% of cases
> > > > (ie. assignment).  x86_64 can still use its own mechanism for
> > > > arch-specific per-cpu data, of course.
> > > 
> > > Assignment should use an own macro (set_this_cpu()) or use per_cpu().
> > 
> > So, we'd have "get_this_cpu(x)" and "set_this_cpu(x, y)".  So far, so good.
> > 
> > 	struct myinfo
> > 	{
> > 		int x;
> > 		int y;
> > 	};
> > 
> > 	static struct myinfo mystuff __per_cpu_data;
> > 
> > Now how do we set mystuff.x on this CPU?
> 
> set_this_cpu(mystuff.x, y) could be eventually supported properly, it just
> needs compiler work (and before that can use address calculation & reference)

I think the effort would be better spent on teaching the compiler
about these special variables, and how to do efficient assignments on
them.

Rusty.
--
  Anyone who quotes me in their sig is an idiot. -- Rusty Russell.