On Mon, Sep 10, 2007 at 11:59:29AM -0700, Christoph Lameter wrote: > On Fri, 17 Aug 2007, Segher Boessenkool wrote: > > > "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. > > Stores can be reordered. Only x86 has (mostly) implicit write ordering. So > no atomic_dec has no volatile semantics and may be reordered on a variety > of processors. Writes to memory may not follow code order on several > processors. The one exception to this being the case where process-level code is communicating to an interrupt handler running on that same CPU -- on all CPUs that I am aware of, a given CPU always sees its own writes in order. Thanx, Paul - 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/
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