It can also break if the read implementation has mutable side effects, e.g. rebalancing. Java HashMap used to have this causing an infinite loop. I haven’t look

It can also break if the read implementation has mutable side effects, e.g. rebalancing. Java HashMap used to have this causing an infinite loop. I haven’t looked recently but my guess is it still does. https://mailinator.blogspot.com/2009/06/beautiful-race-condition.html https://mailinator.blogspot.com/2009/06/beautiful-race-condi... ‘Not thread safe’ really means ‘not thread safe’.