-;;; This lock is seized in the compiler, and related areas: the
-;;; compiler is not presently thread-safe
-(defvar *big-compiler-lock*
- (sb!thread:make-mutex :name "big compiler lock"))
+(!begin-collecting-cold-init-forms)
+;;; This lock is seized in the compiler, and related areas -- like the
+;;; classoid/layout/class system.
+(defglobal **world-lock** nil)
+(!cold-init-forms
+ (setf **world-lock** (sb!thread:make-mutex :name "World Lock")))
+(!defun-from-collected-cold-init-forms !world-lock-cold-init)
+
+(defmacro with-world-lock (() &body body)
+ `(sb!thread:with-recursive-lock (**world-lock**)
+ ,@body))