Agreed. In that case, the threads are just racing to observe a mutating value while it's in the "expected" state.
I will add my voice to the chorus calling for either making roles into closures, or producing a compile-time warning or error. It's tempting to use roles to "monkey patch", and would be good to be warned if it isn't a safe thing to do. I'm fine with closing this as a duplicate. > On Aug 29, 2017, at 7:32 AM, Sam S. via RT <perl6-bugs-follo...@perl.org> > wrote: > > @David > > I think this is not a thread safety issue, but rather a result of `role`s > (intentionally) not being closures. > > I.e. a duplicate of this RT: This is a duplicate of > https://rt.perl.org/Ticket/Display.html?id=130965
