But barriers force a flush of *everything* in scope,
Nonsense, whatever "flush" is supposed to mean here.
If you really, *really* distrust the compiler that much, you shouldn't be using barrier, since that uses volatile under the hood too. You should just go ahead and implement the atomic operations in assembler, like Segher Boessenkool did for powerpc in response to my previous patchset.
Puh-lease. I DO NOT DISTRUST THE COMPILER, I just don't assume it will do whatever I would like it to do without telling it. It's a machine you know, and it is very well documented. (And most barriers don't (need to) use volatile). Implementing the atomic ops in asm loses exactly *no* semantics, and it doesn't add restrictions either; it does allow you however to access an atomic_t with normal loads/stores independently, if you so choose. The only valid issue brought up so far is Russell King's comment that GCC cannot schedule the machine instructions in and around an asm() perfectly, it doesn't look inside the asm() after all; but the situation isn't quite as sever as he suggests (GCC _does_ know you are performing loads/stores, etc.); more about that later, when I've finished researching the current state of that stuff. Segher - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
