On Wed, Sep 16, 2015 at 11:29:08AM +0100, Will Deacon wrote: > > Indeed, that is a hole in the definition, that I think we should close. > I'm struggling to understand the hole, but here's my intuition. If an > ACQUIRE on CPUx reads from a RELEASE by CPUy, then I'd expect CPUx to > observe all memory accessed performed by CPUy prior to the RELEASE > before it observes the RELEASE itself, regardless of this new barrier. > I think this matches what we currently have in memory-barriers.txt (i.e. > acquire/release are neither transitive or multi-copy atomic). Ah agreed. I seem to have gotten my brain in a tangle. Basically where a program order release+acquire relies on an address dependency, a cross cpu release+acquire relies on causality. If we observe the release, we must also observe everything prior to it etc. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
