Re: DYNAMIC-WIND before and after procedures are not protected from interruption

   Date: Thu, 24 Dec 2009 00:50:28 -0800
   From: Robert Ransom <[email protected]>

   You don't need to interrupt that code snippet during the after thunk to
   keep it from releasing its lock:

   > ,open debug-messages threads
   > (define (make-print-thunk . xs) (lambda () (apply debug-message xs)))
   ; no values returned
   > (dynamic-wind (make-print-thunk "<in>") (lambda () (sleep 10000)) (make-print-thunk "<out>"))
   <in>
   ^C
   interrupt: keyboard interrupt [command-level-event-handler]
              keyboard
   1> ,pop
   <out>
   ; no values returned
   > 

I don't understand.  Both before and after procedures were executed,
as the output demonstrates.  How would the lock not be released?