Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures

[Russell King]

On Tue, Aug 21, 2007 at 12:04:17AM +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.

This means placing atomic_t or bitops into MMIO space is a definite
no-go on ARM.  It breaks.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/