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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Wed, 01 May 2013 11:39:53 +1000

> I'm not even completely certain bytes are safe to be honest, though
> probably more than bitfields. I'll poke our compiler people.

Older Alpha only has 32-bit and 64-bit loads and stores, so byte sized
accesses are not atomic, and therefore use racey read-modify-write
sequences.