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SubjectRe: [PATCH 0/24] make atomic_read() behave consistently across all architectures
On Tue, Aug 21, 2007 at 01:02:01AM +0200, Segher Boessenkool wrote:
> >>And no, RMW on MMIO isn't "problematic" at all, either.
> >>
> >>An RMW op is a read op, a modify op, and a write op, all rolled
> >>into one opcode. But three actual operations.
> >
> >Maybe for some CPUs, but not all. ARM for instance can't use the
> >load exclusive and store exclusive instructions to MMIO space.
>
> Sure, your CPU doesn't have RMW instructions -- how to emulate
> those if you don't have them is a totally different thing.

Let me say it more clearly: On ARM, it is impossible to perform atomic
operations on MMIO space.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of:
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