Messages in this thread | | | Date | Tue, 19 Mar 2002 01:15:34 +0100 | From | Andi Kleen <> | Subject | Re: [PATCH] 2.5.1-pre5: per-cpu areas |
| |
On Tue, Mar 19, 2002 at 11:02:09AM +1100, Rusty Russell wrote: > In message <20020318083511.A19810@wotan.suse.de> 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 <ak@suse.de> 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.
That would be the idea. gcc would learn how to use the %gs segment prefix (similar to the equivalent feature in Windows compilers). The only drawback is that it still cannot easily load the address except if you define some silly convention (like a pointer to the segment base being always stored at the segment base address)
But it is a lot of work to teach gcc about the multiple address spaces...
-Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |