+Critical parts of PCL are protected by *world-lock* (particularly
+those dealing with class graph changes), and some with finer-grained locks.
+
+accesses locked with a nice granularity
+ SB-PCL::*CLASSOID-CELLS*
+
+read-only & safe:
+ SB-PCL::*BUILT-IN-TYPEP-COST*
+ SB-PCL::*CACHE-EXPAND-THRESHOLD*
+ SB-PCL::*CACHE-LOOKUP-COST*
+ SB-PCL::*CASE-TABLE-LIMIT*
+ SB-PCL::*CHECK-CACHE-P*
+ SB-PCL::*COMPUTE-STD-CPL-CLASS->ENTRY-TABLE-SIZE*
+ SB-PCL::*EQ-CASE-TABLE-LIMIT*
+ SB-PCL::*NON-BUILT-IN-TYPEP-COST*
+ SB-PCL::*NON-VAR-DECLARATIONS*
+ SB-PCL::*SECONDARY-DFUN-CALL-COST*
+ SB-PCL::*SGF-WRAPPER*
+ SB-PCL::*STRUCTURE-TYPEP-COST*
+ SB-PCL::*UNSPECIFIC-ARG*
+ SB-PCL::*VAR-DECLARATIONS-WITH-ARG*
+ SB-PCL::*WRAPPER-OF-COST*
+
+bound & safe:
+ SB-PCL::*ALLOW-FORWARD-REFERENCED-CLASSES-IN-CPL-P*
+ SB-PCL::*IN-OBSOLETE-INSTANCE-TRAP*
+ SB-PCL::*PRECOMPILING-LAP*
+ SB-PCL::*CACHE-MISS-VALUES-STACK*
+
+protected by PCL-LOCK:
+ SB-PCL::*PREVIOUS-NWRAPPERS*
+
+believed protected by the compiler-lock:
+ SB-PCL::*ALL-CTORS*
+ SB-PCL::*FGENS*
+ SB-PCL::*SGF-DFUN-STATE-INDEX*
+ SB-PCL::*VAR-DECLARATIONS-WITHOUT-ARG*
+
+potentially unsafe:
+ SB-PCL::*CLASS-EQ-SPECIALIZER-METHODS*
+ SB-PCL::*EFFECTIVE-METHOD-CACHE*
+ SB-PCL::*EQL-SPECIALIZER-METHODS*
+ SB-PCL::*METHOD-FUNCTION-PLIST*
+ SB-PCL::*PV-KEY-TO-PV-TABLE-TABLE*
+ SB-PCL::*PV-TABLE-CACHE-UPDATE-INFO*
+ SB-PCL::*PVS*
+ SB-PCL::*SLOT-NAME-LISTS-INNER*
+ SB-PCL::*SLOT-NAME-LISTS-OUTER*
+
+debugging / profiling -- low relevance:
+ SB-PCL::*DFUN-COUNT*
+ SB-PCL::*ALLOW-EMF-CALL-TRACING-P*
+
+build-options and bootstrap machinery -- irrelevant for user-code:
+ SB-PCL::*ALLOW-EXPERIMENTAL-SPECIALIZERS-P*
+ SB-PCL::*BOOT-STATE* ; pseudoconstant in finished lisp (not in bootstrap)
+ SB-PCL::*BUILT-IN-CLASS-SYMBOLS*
+ SB-PCL::*BUILT-IN-CLASSES*
+ SB-PCL::*BUILT-IN-WRAPPER-SYMBOLS*
+ SB-PCL::*CHECKING-OR-CACHING-LIST*