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

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.

"volatile" has nothing to do with reordering.  atomic_dec() writes
to memory, so it _does_ have "volatile semantics", implicitly, as
long as the compiler cannot optimise the atomic variable away
completely -- any store counts as a side effect.


Segher

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