> It's a point in time write barrier no That's the only way it makes sense. The caller controls when they start the sync, so they can make sure that all writes

> It's a point in time write barrier no That's the only way it makes sense. The caller controls when they start the sync, so they can make sure that all writes they care about have been issued by then. But it's impossible to define a temporal ordering between writes and the time the sync completes. That's not a well-defined point in time. There's always a non-zero delay between the time the sync proper completes and the caller gets back control.