anchor.diff:  
   (defmacro with-pseudo-atomic (&body body)
     `(call-with-pseudo-atomic (dx-lambda () ,@body)))
  +
  +;;; Higher-level locks and things.
   
   ;;; Common structure for sleepable things.
   (defstruct (wait-queue
  
positive.code:   (reg-field rsp                445)
    (reg-field ss                 446))
  
  (defun thread-frame-pointer (thread)
    (thread-state-rbp thread))
  
  
negative.code:                                    old (cons function old))
           (return)))))
  
  ;;; Stopping the world.
  ;;; WITH-WORLD-STOPPED and WITH-PSEUDO-ATOMIC work together as a sort-of global
  ;;; reader/writer lock over the whole system.
  
  