My point still stands: to fix this, you have to realize that (a) v could be shared here and (b) that sharing could be a problem. I suspect the first time most

My point still stands: to fix this, you have to realize that (a) v could be shared here and (b) that sharing could be a problem. I suspect the first time most newbies get hit with a race condition here they're going to be beyond baffled.