On Tue, Jul 16, 2013 at 1:49 AM, Linus Torvalds
<torva...@linux-foundation.org> wrote:
> On Mon, Jul 15, 2013 at 10:28 AM, Geert Uytterhoeven
> <ge...@linux-m68k.org> wrote:
>>
>> but the first one is non-trivial: using xchg() on atomic_t is a bit gross...
>
> It's also broken. There's no guarantee that an "atomic_t" is just a
> value. Now, the old sparc32 stuff (which hid lock bits in atomic_t)
> may be gone, but it's still the case that atomic_t may not actually
> work with xchg.
>
> (In *practice* it works on normal architectures, so I'm not saying
> that we don't have it, but it's a bug if we do).
>
> There are "atomic_xchg()" and "atomic_xchg64()" functions that are supported.
I'll send a patch to fix it.
>
> Linus
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