I'm doubtful that this early exit is entirely safe. None of the preceding operations imply a memory barrier. The buffer could previously have been marked dirty, but cleaned since. It's pretty critical that we re-set the dirty bit (there's no danger of loosing it with a barrier, because we hold an exclusive content lock).
Oh, I get it.
Practically the risk seems fairly low, because acquiring the exclusive content lock will have implied a barrier. But it seems unlikely to have a measurable performance effect to me, so I'd rather not add the early exit.
