On Thu, 16 Aug 2007, Chris Snook wrote:

atomic_dec() already has volatile behavior everywhere, so this is semantically
okay, but this code (and any like it) should be calling cpu_relax() each
iteration through the loop, unless there's a compelling reason not to.  I'll
allow that for some hardware drivers (possibly this one) such a compelling
reason may exist, but hardware-independent core subsystems probably have no
excuse.

No it does not have any volatile semantics. atomic_dec() can be reordered 
at will by the compiler within the current basic unit if you do not add a 
barrier.