Re: [RESEND PATCH v2] devres: Really align data field to unsigned long long

[Geert Uytterhoeven]

On Mon, Jul 9, 2018 at 11:15 AM David Laight <David.Laight@xxxxxxxxxx> wrote:
> From: Alexey Brodkin
> > Sent: 09 July 2018 05:45
> > Depending on ABI "long long" type of a particular 32-bit CPU
> > might be aligned by either word (32-bits) or double word (64-bits).
> > Make sure "data" is really 64-bit aligned for any 32-bit CPU.
> >
> > At least for 32-bit ARC cores ABI requires "long long" types
> > to be aligned by normal 32-bit word. This makes "data" field aligned to
> > 12 bytes. Which is still OK as long as we use 32-bit data only.
> >
> > But once we want to use native atomic64_t type (i.e. when we use special
> > instructions LLOCKD/SCONDD for accessing 64-bit data) we easily hit
> > misaligned access exception.
>
> Shouldn't there be a typedef for the actual type.
> Perhaps it is even atomic64_t ?
> And have the __aligned(8) applied to that typedef ??

That indeed sounds like the best thing to do, as it will fix this issue in other
places, too.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds