anchor.diff:  
   (defvar *pager-waiting-threads*)
   (defvar *pager-current-thread*)
  -(defvar *pager-cvar*)
   (defvar *pager-lock*)
   
   (defvar *disks*)
  
positive.code:           (thread-wait-item self) address
            (thread-%next self) *pager-waiting-threads*
            *pager-waiting-threads* self)
      (condition-notify *pager-cvar*)
      (release-mutex *pager-lock*)
      (%reschedule-via-interrupt interrupt-frame)))
  
  
negative.code:   (when (not (boundp '*pager-waiting-threads*))
      (setf *pager-waiting-threads* '()
            *pager-current-thread* nil
            *pager-lock* (make-mutex "Pager lock" :spin)))
    (when *pager-current-thread*
      ;; Push any current thread back on the waiting threads list.
  