(defclass metalock (c2mop:standard-class)
  ((locks :type list :accessor locks)))

(defmethod c2mop:validate-superclass ((class metalock) (metaclass standard-class))
  t)
(defmethod c2mop:validate-superclass ((class standard-class) (metaclass metalock))
  t)

(defclass locked-object ()
  ((arr :initform "oof"
        :accessor arr-access))
  (:metaclass metalock))

(defparameter *lock* (bt:make-lock))


;; (defmethod c2mop:slot-value-using-class :around ((class metalock) object slotd)
;;   (bt:with-lock-held (*lock*)
;;     (print "lock held")
;;     (let ((val (call-next-method)))
;;       (print "lock dropped")
;;       val)))

(defun slot-names-to-lock-alist (slot-names)
  (check-type slot-names list)
  (mapcar (lambda (name)
            (cons name (bt:make-lock)))
          slot-names))

(defmethod c2mop:compute-slots ((class metalock))
  (let* ((normal-slots (call-next-method))
         (slot-names (mapcar #'c2mop:slot-definition-name normal-slots))
         (slot-names-lock-alist (slot-names-to-lock-alist slot-names)))
    (cons
     (make-instance 'c2mop:effective-slot-definition
                    :name 'slot-locks
                    :initform `',slot-names-lock-alist
                    :initfunction #'(lambda () slot-names-lock-alist)
                    :class (find-class 'c2mop:standard-slot-definition))
     normal-slots)))

;;;;error

There is no applicable method for the generic function
  #<STANDARD-GENERIC-FUNCTION SB-MOP:SLOT-DEFINITION-ALLOCATION (3)>
when called with arguments
  (#<SB-MOP:EFFECTIVE-SLOT-DEFINITION METALOCK::SLOT-LOCKS>).
   [Condition of type SB-PCL::NO-APPLICABLE-METHOD-ERROR]

Restarts:
 0: [RETRY] Retry calling the generic function.
 1: [RETRY] Retry SLY mREPL evaluation request.
 2: [*ABORT] Return to SLY's top level.
 3: [ABORT] abort thread (#<THREAD "sly-channel-1-mrepl-remote-1" RUNNING {1004D04BD3}>)

Backtrace:
 0: ((:METHOD NO-APPLICABLE-METHOD (T)) #<STANDARD-GENERIC-FUNCTION SB-MOP:SLOT-DEFINITION-ALLOCATION (3)> #<SB-MOP:EFFECTIVE-SLOT-DEFINITION METALOCK::SLOT-LOCKS>) [fast-method]
 1: ((LAMBDA (SB-PCL::.ARG0. SB-INT:&MORE SB-PCL::.MORE-CONTEXT. SB-PCL::.MORE-COUNT.)) #<STANDARD-GENERIC-FUNCTION SB-MOP:SLOT-DEFINITION-ALLOCATION (3)> #<SB-MOP:EFFECTIVE-SLOT-DEFINITION METALOCK::SLOT..
 2: (SB-PCL::CALL-NO-APPLICABLE-METHOD #<STANDARD-GENERIC-FUNCTION SB-MOP:SLOT-DEFINITION-ALLOCATION (3)> (#<SB-MOP:EFFECTIVE-SLOT-DEFINITION METALOCK::SLOT-LOCKS>))
 3: (SB-PCL::STD-COMPUTE-SLOTS-AROUND #<METALOCK METALOCK::LOCKED-OBJECT> (#<SB-MOP:EFFECTIVE-SLOT-DEFINITION METALOCK::SLOT-LOCKS> #<SB-MOP:STANDARD-EFFECTIVE-SLOT-DEFINITION METALOCK::ARR>))
 4: ((FLET SB-THREAD::WITH-RECURSIVE-LOCK-THUNK :IN SB-PCL::UPDATE-CLASS))
 5: ((FLET "WITHOUT-INTERRUPTS-BODY-29" :IN SB-THREAD::CALL-WITH-RECURSIVE-LOCK))
 6: (SB-THREAD::CALL-WITH-RECURSIVE-LOCK #<CLOSURE (FLET SB-THREAD::WITH-RECURSIVE-LOCK-THUNK :IN SB-PCL::UPDATE-CLASS) {7F7C3D1BC9EB}> #<SB-THREAD:MUTEX "World Lock" owner: #<SB-THREAD:THREAD "sly-channe..
 7: ((LABELS SB-PCL::REC :IN SB-PCL::UPDATE-CLASS) #<METALOCK METALOCK::LOCKED-OBJECT> T NIL)
 8: ((:METHOD MAKE-INSTANCE (CLASS)) #<METALOCK METALOCK::LOCKED-OBJECT>) [fast-method]
 9: (SB-INT:SIMPLE-EVAL-IN-LEXENV (MAKE-INSTANCE (QUOTE LOCKED-OBJECT)) #<NULL-LEXENV>)
10: (EVAL (MAKE-INSTANCE (QUOTE LOCKED-OBJECT)))
11: ((LAMBDA NIL :IN SLYNK-MREPL::MREPL-EVAL-1))
 --more--