Re: gcc 4.5 and TLS
On Sun, Jun 06, 2010 at 10:42:40AM +0200, Andreas Schwab wrote:
> Brad Boyer <flar@allandria.com> writes:
>
> > I may be missing something obvious, but why don't we just change the
> > kernel to allow 2-byte alignment for m68k? The comment in futex.c
> > just says "natural" alignment but is then hard-coded for sizeof(u32).
>
> Natural alignment *is* sizeof.
OK, then I guess my real question is "why does it need alignment"? I
obviously don't have a good understanding of the futex code, but this
seems like something that could have pretty significant effects. It
looks like the need for natural alignment is to avoid alignment
exceptions in the kernel or something like that, but m68k doesn't
have such a thing since the hardware always does it. Please let
me know what I missing here. I even looked at the 68040 UM to see
if the CAS instruction does anything odd, since I know some other
chips have some weird limits on atomic instructions.
Brad Boyer
flar@allandria.com
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