Hi Paul,
On Mon, Aug 22, 2016 at 9:54 PM, Paul E. McKenney
<[email protected]> wrote:
> On Mon, Aug 22, 2016 at 03:18:54PM -0400, Steven Rostedt wrote:
>> On Mon, 22 Aug 2016 20:56:09 +0200
>> Peter Zijlstra <[email protected]> wrote:
>>
>> > > Don't we have __alignof__(void *) to avoid #ifdef CONFIG_M68K and
>> > > other new macros ?
>
> Hmmm... Does __alignof__(void *) give two-byte alignment on m68k,
> allowing something like this? Heh!!! It is already there. ;-)
>
> struct callback_head {
> struct callback_head *next;
> void (*func)(struct callback_head *head);
> } __attribute__((aligned(sizeof(void *))));
No, it's aligning to sizeof(void *) (4 on m68k), not __alignof__(void *).
> #define rcu_head callback_head
>
> If so, that does sound quite attractive! Might need the WARN_ON()
> anyway, to flag wild pointers if nothing else.
>
> Adding Geert on CC for his thoughts.
__alignof__(void *) is indeed 2 on m68k, and h8300.
Note that it is 1 on crisv32!
It's 4 or 8 on anything else I have a cross-compiler for.
$ cat a.c
unsigned x = __alignof__(void *);
$ for i in /opt/cross/*/*/bin/*gcc; do echo +++ $i +++; $i -c -S a.c;
cat a.s; done | less
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
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
