At Fri, 3 May 2013 11:56:02 -0400, Eli Barzilay wrote: > > A few minutes ago, Vincent St-Amour wrote: > > Sam, Asumu and I found and fixed the bug. Here's the problem in a > > nutshell. > > > > This is the implementation of `delay/thread' from racket/promise. > > > > (define (delay/thread thunk) > > (let () > > (define (run) > > (call-with-exception-handler > > (lambda (e) (pset! p (make-reraise e)) (kill-thread > > (current-thread))) > > (lambda () (pset! p (call-with-values thunk list))))) > > (define p > > (make-promise/thread > > (make-running-thread > > (object-name thunk) > > (thread run)))) > > p)) > > [...] > > Our solution is to have `run' block on a channel until `p' is fully > > initialized. I'll push the fix. > > I haven't looked at the code recently, but I think that something > along these lines can work instead of some explicit syncing: > > (define (delay/thread thunk) > (let () > (define p (make-promise/thread #f)) > (pset! p (make-running-thread (thread (λ() ...same...)))) > p))
I think that introduces another race condition. If the thread is forced before the `pset!', then `force' would return #f (line 107 of racket/promise.rkt), since the value inside the `promise/thread' is not a thread. Vincent _________________________ Racket Developers list: http://lists.racket-lang.org/dev
