src/code/thread.lisp

   1 (in-package "SB!THREAD")
   2
   3 (sb!xc:defmacro with-recursive-lock ((mutex) &body body)
   4   #!+sb-thread
   5   (with-unique-names (cfp)
   6     `(let ((,cfp (sb!kernel:current-fp)))
   7       (unless (and (mutex-value ,mutex)
   8                    (sb!vm:control-stack-pointer-valid-p
   9                     (sb!sys:int-sap
  10                      (sb!kernel:get-lisp-obj-address (mutex-value ,mutex)))))
  11         ;; this punning with MAKE-LISP-OBJ depends for its safety on
  12         ;; the frame pointer being a lispobj-aligned integer.  While
  13         ;; it is, then MAKE-LISP-OBJ will always return a FIXNUM, so
  14         ;; we're safe to do that.  Should this ever change, this
  15         ;; MAKE-LISP-OBJ could return something that looks like a
  16         ;; pointer, but pointing into neverneverland, which will
  17         ;; confuse GC completely.  -- CSR, 2003-06-03
  18         (get-mutex ,mutex (sb!kernel:make-lisp-obj (sb!sys:sap-int ,cfp))))
  19       (unwind-protect
  20            (progn ,@body)
  21         (when (sb!sys:sap= (sb!sys:int-sap
  22                             (sb!kernel:get-lisp-obj-address
  23                              (mutex-value ,mutex)))
  24                            ,cfp)
  25           (release-mutex ,mutex)))))
  26   #!-sb-thread
  27   `(progn ,@body))
  28