coroutines with bordeaux-threads (broken)

gistfile1.cl

(defmacro make-coroutine ((&key (coroutine-done-value :done)) &body body)
  (alexandria:with-gensyms ((yield-cv "can we yield?")
			    (run-cv "can we run?")
			    (run-lck "lock for the runner thread")
			    (val "yielding value")
			    (thrfn "thread body"))
    `(let* ((,yield-cv (bordeaux-threads:make-condition-variable
			 :name "yield"))
	    (,run-cv (bordeaux-threads:make-condition-variable
		      :name "run"))
	    (,run-lck (bordeaux-threads:make-lock "run lock"))
	    ,val
	    (,thrfn (lambda ()	  
		      (flet ((yield (&optional n)
			       (setf ,val n)
			       ;; tell interested parties a value is ready
			       (bordeaux-threads:condition-notify ,yield-cv)
			       ;;wait for a chance to run
			       (bordeaux-threads:condition-wait ,run-cv ,run-lck)
			       ,val))
			(bordeaux-threads:acquire-lock ,run-lck)
			,@body
			(yield ,coroutine-done-value)))))

       ;;function to pull values from the coroutine
       (let ((alive-p T)
	     thr)
	 (lambda ()
	   (unless thr
	       (setf thr (bordeaux-threads:make-thread
			  ,thrfn :name "coroutine")))

	   (when (and alive-p (bordeaux-threads:thread-alive-p thr))
	     ;; tell the coroutine to run
	     (bordeaux-threads:with-lock-held (,run-lck)
	       (bordeaux-threads:condition-notify ,run-cv) 
	       (bordeaux-threads:condition-wait ,yield-cv ,run-lck))
	     (when (eql ,coroutine-done-value ,val)
	       (bordeaux-threads:destroy-thread thr)
	       (setf alive-p nil)))
	   ,val)))))