(module key mzscheme
  (provide break-threads)
  (define super-cust (current-custodian))
  (define first-child (make-custodian))
  (current-custodian first-child)
  
  
  (define (break-threads)
    (parameterize ([current-custodian super-cust])
      (thread
       (λ ()
         (let loop ([super-cust super-cust]
                    [current-cust first-child])
           (for-each (λ (man)
                       (when (thread? man)
                         (break-thread man))
                       (when (custodian? man)
                         (loop current-cust man)))
                     (custodian-managed-list current-cust super-cust))))))))
