thread bug on ARMCL RPI

;; (THREADTEST ..) launches some threads that generate garbage.
;; It crashes on latest rpi deb build  with:
;;   > Unhandled exception 4 at 0x1512acec, context->regs at #x74d64490

;; specifically, it
;; crashes on raspberri pi armcl dev version:
;;        * "Version 1.12-dev (v1.12-dev.4-3-gdd5622e9) LinuxARM32"
;; but does NOT crash on release version:
;;        * "Version 1.11.5/v1.11.5  (LinuxARM32)"


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; It also seems to expose a locking problem in Version 1.11.5 when
;; run as (threadtest :loop-count 10000 :exercise-locking) to force
;; allocations inside the threads to take place inside a
;; with-lock-grabbed, the error:
;;
;;  Current process #<PROCESS Reader 4(26) [Active] #x150D335E> does not own
;;  lock #<RECURSIVE-LOCK "glock" [ptr @ #x76105C60] #x150BB0D6>
;;
;; occurs in CCL::%UNLOCK-RECURSIVE-LOCK-OBJECT
;;
;; could this locking problem be the source of the threading bug here?
;; https://trac.clozure.com/ccl/ticket/1257


(defparameter *the-glock* nil) ;; allow us to look at lock while running

(defun threadtest (&key
             (thread-count 7)
             (loop-count 1000)
             (exercise-locking nil)
             (garbage-count 1000))
  (let ((done-flags (make-array thread-count :initial-element nil))
    (lock (ccl:make-lock "done-flags-lock"))
    (glock (when exercise-locking
         (ccl:make-lock "glock"))))
    (setf *the-glock* glock)
    (dotimes (i thread-count)
      (process-run-function
       (format nil "Reader ~d" i)
       (lambda (i)
     (unwind-protect
          (dotimes (j loop-count)
        #+nil ;; temporarily remove this additonal complication
        (setf (ccl:process-name ccl:*current-process*)
              (format nil "Reader ~d: ~d" i j))
        (garbagemaker garbage-count glock)
        ))
     (ccl:with-lock-grabbed (lock) (setf (elt done-flags i) t)))
       i))
    (loop do
         (unless
         (ccl:with-lock-grabbed (lock)
           (position nil done-flags))
       (return)))))


;; make some garbage, optionally grab a lock to exercise
;; locking in threads
(defun garbagemaker (garbage-count lock)
  (loop for i below garbage-count
     collect (if lock
           (ccl:with-lock-grabbed (lock)
         (make-string 10))
           (make-string 10))))