Revert "Allow reading cvars from non-main Ractors (ruby#16308)"

This reverts commit ab32c0e.

Author: Edouard-chin

bootstraptest/test_ractor.rb

@@ -1058,8 +1058,8 @@ def initialize
   values.join
 }
 
-# Reading non-shareable cvar from non-main Ractor is not allowed
-assert_equal 'can not read non-shareable class variable @@cv from non-main Ractors (C)', %q{
+# cvar in shareable-objects are not allowed to access from non-main Ractor
+assert_equal 'can not access class variables from non-main Ractors (@@cv from C)', %q{
   class C
     @@cv = 'str'
   end
@@ -1077,8 +1077,8 @@ class C
   end
 }
 
-# also cached non-shareable cvar read from non-main Ractor is not allowed
-assert_equal 'can not read non-shareable class variable @@cv from non-main Ractors (C)', %q{
+# also cached cvar in shareable-objects are not allowed to access from non-main Ractor
+assert_equal 'can not access class variables from non-main Ractors (@@cv from C)', %q{
   class C
     @@cv = 'str'
     def self.cv
@@ -1099,95 +1099,6 @@ def self.cv
   end
 }
 
-# Reading shareable cvar from non-main Ractor is allowed
-assert_equal 'shareable', %q{
-  class C
-    @@cv = 'shareable'.freeze
-    def self.cv
-      @@cv
-    end
-  end
-
-  Ractor.new { C.cv }.value
-}
-
-# Reading shareable cvar (integer) from non-main Ractor is allowed
-assert_equal '42', %q{
-  class C
-    @@cv = 42
-    def self.cv
-      @@cv
-    end
-  end
-
-  Ractor.new { C.cv }.value.to_s
-}
-
-# Reading shareable cvar via module include from non-main Ractor is allowed
-assert_equal 'hello', %q{
-  module M
-    @@cv = 'hello'.freeze
-    def self.cv
-      @@cv
-    end
-  end
-
-  class C
-    include M
-    def self.cv
-      @@cv
-    end
-  end
-
-  Ractor.new { C.cv }.value
-}
-
-# Writing cvar from non-main Ractor is not allowed
-assert_equal 'can not set class variables from non-main Ractors (@@cv from C)', %q{
-  class C
-    @@cv = 'str'
-    def self.cv=(v)
-      @@cv = v
-    end
-  end
-
-  r = Ractor.new do
-    C.cv = 'new'
-  end
-
-  begin
-    r.join
-  rescue Ractor::RemoteError => e
-    e.cause.message
-  end
-}
-
-# Reading cvar that was made shareable after initial assignment
-assert_equal 'made shareable', %q{
-  class C
-    @@cv = +'made shareable'
-    Ractor.make_shareable(@@cv)
-    def self.cv
-      @@cv
-    end
-  end
-
-  Ractor.new { C.cv }.value
-}
-
-# cvar_defined? works from non-main Ractor
-assert_equal 'true', %q{
-  class C
-    @@cv = 42
-    def self.cv?
-      defined?(@@cv)
-    end
-  end
-
-  r = Ractor.new { C.cv? ? 'true' : 'false' }
-  r.value
-}
-
 # Getting non-shareable objects via constants by other Ractors is not allowed
 assert_equal 'can not access non-shareable objects in constant C::CONST by non-main Ractor.', <<~'RUBY', frozen_string_literal: false
   class C

variable.c

@@ -1216,20 +1216,7 @@ CVAR_ACCESSOR_SHOULD_BE_MAIN_RACTOR(VALUE klass, ID id)
     if (UNLIKELY(rb_ractor_isolation_check_active())) {
         /* See comment on the instance-variable warning below for why we
          * pass rb_class_path() rather than the class itself. */
-        rb_ractor_isolation_violation("can not set class variables from non-main Ractors (%"PRIsVALUE" from %"PRIsVALUE")", rb_id2str(id), rb_class_path(klass));
-    }
-}
-
-static void
-cvar_read_ractor_check(VALUE klass, ID id, VALUE val)
-{
-    if (UNLIKELY(rb_ractor_isolation_check_active())) {
-        VALUE chain = Qnil;
-        if (!rb_ractor_shareable_p_continue(val, &chain)) {
-            rb_ractor_isolation_violation_with_chain(chain,
-                    "can not read non-shareable class variable %"PRIsVALUE" from non-main Ractors (%"PRIsVALUE")",
-                    rb_id2str(id), rb_class_path(klass));
-        }
+        rb_ractor_isolation_violation("can not access class variables from non-main Ractors (%"PRIsVALUE" from %"PRIsVALUE")", rb_id2str(id), rb_class_path(klass));
     }
 }
 
@@ -4330,6 +4317,7 @@ cvar_overtaken(VALUE front, VALUE target, ID id)
     }
 
 #define CVAR_LOOKUP(v,r) do {\
+    CVAR_ACCESSOR_SHOULD_BE_MAIN_RACTOR(klass, id); \
     if (cvar_lookup_at(klass, id, (v))) {r;}\
     CVAR_FOREACH_ANCESTORS(klass, v, r);\
 } while(0)
@@ -4351,8 +4339,6 @@ find_cvar(VALUE klass, VALUE * front, VALUE * target, ID id)
 void
 rb_cvar_set(VALUE klass, ID id, VALUE val)
 {
-    CVAR_ACCESSOR_SHOULD_BE_MAIN_RACTOR(klass, id);
-
     VALUE tmp, front = 0, target = 0;
 
     tmp = klass;
@@ -4427,7 +4413,6 @@ rb_cvar_find(VALUE klass, ID id, VALUE *front)
                           klass, ID2SYM(id));
     }
     cvar_overtaken(*front, target, id);
-    cvar_read_ractor_check(klass, id, value);
     return (VALUE)value;
 }