From mboxrd@z Thu Jan  1 00:00:00 1970
From: Segher Boessenkool <segher@kernel.crashing.org>
Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
Date: Tue, 21 Aug 2007 01:02:01 +0200
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To: Russell King <rmk+lkml@arm.linux.org.uk>
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>> 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.


Segher