Re: [patch] i386: make bitops safe

[Andi Kleen <ak@suse.de>]

On Tuesday 28 February 2006 00:06, Linus Torvalds wrote:
> On Mon, 27 Feb 2006, Chuck Ebbert wrote:
> > Make i386 bitops safe.  Currently they can be fooled, even on
> > uniprocessor, by code that uses regions of the bitmap before
> > invoking the bitop.  The least costly way to make them safe
> > is to add a memory clobber and tag all of them as volatile.
>
> Actually, the least costly way should be to make the "ADDR" define work
> right again.
>
> It used to do something magic like

I remember asking rth about this at some point and IIRC
he expressed doubts if it would actually do what expected. Richard?

-Andi

>
> 	struct fake_area {
> 		unsigned long members[1000];
> 	};
>
> 	#define ADDR (*(volatile struct fake_area *)addr)
>
> which was correct. I forget why it got broken into using just a "long *"
> (it happened a long long time ago).
>
> 		Linus