-;;;; SCRUB-CONTROL-STACK
-
-(defconstant bytes-per-scrub-unit 2048)
-
-;;; Zero the unused portion of the control stack so that old objects
-;;; are not kept alive because of uninitialized stack variables.
-
-;;; "To summarize the problem, since not all allocated stack frame
-;;; slots are guaranteed to be written by the time you call an another
-;;; function or GC, there may be garbage pointers retained in your
-;;; dead stack locations. The stack scrubbing only affects the part
-;;; of the stack from the SP to the end of the allocated stack."
-;;; - ram, on cmucl-imp, Tue, 25 Sep 2001
-
-;;; So, as an (admittedly lame) workaround, from time to time we call
-;;; scrub-control-stack to zero out all the unused portion. This is
-;;; supposed to happen when the stack is mostly empty, so that we have
-;;; a chance of clearing more of it: callers are currently (2002.07.18)
-;;; REPL and SUB-GC
-
-(defun scrub-control-stack ()
- (declare (optimize (speed 3) (safety 0))
- (values (unsigned-byte 20))) ; FIXME: DECLARE VALUES?
-
- #!-stack-grows-downward-not-upward
- (let* ((csp (sap-int (sb!c::control-stack-pointer-sap)))
- (initial-offset (logand csp (1- bytes-per-scrub-unit)))
- (end-of-stack
- (- sb!vm:control-stack-end sb!c:*backend-page-size*)))
- (labels
- ((scrub (ptr offset count)
- (declare (type system-area-pointer ptr)
- (type (unsigned-byte 16) offset)
- (type (unsigned-byte 20) count)
- (values (unsigned-byte 20)))
- (cond ((>= (sap-int ptr) end-of-stack) 0)
- ((= offset bytes-per-scrub-unit)
- (look (sap+ ptr bytes-per-scrub-unit) 0 count))
- (t
- (setf (sap-ref-32 ptr offset) 0)
- (scrub ptr (+ offset sb!vm:n-word-bytes) count))))
- (look (ptr offset count)
- (declare (type system-area-pointer ptr)
- (type (unsigned-byte 16) offset)
- (type (unsigned-byte 20) count)
- (values (unsigned-byte 20)))
- (cond ((>= (sap-int ptr) end-of-stack) 0)
- ((= offset bytes-per-scrub-unit)
- count)
- ((zerop (sap-ref-32 ptr offset))
- (look ptr (+ offset sb!vm:n-word-bytes) count))
- (t
- (scrub ptr offset (+ count sb!vm:n-word-bytes))))))
- (declare (type (unsigned-byte 32) csp))
- (scrub (int-sap (- csp initial-offset))
- (* (floor initial-offset sb!vm:n-word-bytes) sb!vm:n-word-bytes)
- 0)))
-
- #!+stack-grows-downward-not-upward
- (let* ((csp (sap-int (sb!c::control-stack-pointer-sap)))
- (end-of-stack (+ sb!vm:control-stack-start sb!c:*backend-page-size*))
- (initial-offset (logand csp (1- bytes-per-scrub-unit))))
- (labels
- ((scrub (ptr offset count)
- (declare (type system-area-pointer ptr)
- (type (unsigned-byte 16) offset)
- (type (unsigned-byte 20) count)
- (values (unsigned-byte 20)))
- (let ((loc (int-sap (- (sap-int ptr) (+ offset sb!vm:n-word-bytes)))))
- (cond ((< (sap-int loc) end-of-stack) 0)
- ((= offset bytes-per-scrub-unit)
- (look (int-sap (- (sap-int ptr) bytes-per-scrub-unit))
- 0 count))
- (t ;; need to fix bug in %SET-STACK-REF
- (setf (sap-ref-32 loc 0) 0)
- (scrub ptr (+ offset sb!vm:n-word-bytes) count)))))
- (look (ptr offset count)
- (declare (type system-area-pointer ptr)
- (type (unsigned-byte 16) offset)
- (type (unsigned-byte 20) count)
- (values (unsigned-byte 20)))
- (let ((loc (int-sap (- (sap-int ptr) offset))))
- (cond ((< (sap-int loc) end-of-stack) 0)
- ((= offset bytes-per-scrub-unit)
- count)
- ((zerop (sb!kernel::get-lisp-obj-address (stack-ref loc 0)))
- (look ptr (+ offset sb!vm:n-word-bytes) count))
- (t
- (scrub ptr offset (+ count sb!vm:n-word-bytes)))))))
- (declare (type (unsigned-byte 32) csp))
- (scrub (int-sap (+ csp initial-offset))
- (* (floor initial-offset sb!vm:n-word-bytes) sb!vm:n-word-bytes)
- 0))))
-\f