Re: [Xen-devel] [PATCH LINUX v5] xen: event channel arrays are xen_ulong_t and not unsigned long

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Thu, 2013-03-07 at 03:17 +0000, Will Deacon wrote:
> > I looked and couldn't see an existing 64 bit xchg, was I looking in the
> > wrong place? Ah, wait, I see atomic64_xchg now. But that needs an
> > atomic64_t while I have a xen_ulong_t (which == 64 bits on ARM). This is
> > a kernel<->hypervisor ABI so I can't just change it to an atomic64_t. I
> > suppose I could cast (see below, untested) but that seems rather icky.
> 
> You can play some container_of tricks, like we do in cmpxchg64 to get this
> right. Alternatively, we could look at an xchg8 implementation which some
> other architectures have (although they seem to be 64-bit machines).

I went with the container of trick + appropriate Kconfig depends and
sent a patch out a couple of seconds ago.

Thanks for your help/advice!

Ian.


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