From 9af743fe0e8c7aa7a25a6805a64d499aab3032af Mon Sep 17 00:00:00 2001
From: ko1 <ko1@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Mon, 12 Aug 2013 06:19:15 +0000
Subject: [PATCH] * class.c (rb_prepend_module): make T_ICLASS object shady
 because   this T_ICLASS object seems to share method table with other class  
 objects. It was causes WB miss.   TODO: need to know the data structure. *
 test/ruby/test_module.rb: add a test for WB miss.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42534 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 ChangeLog                |  9 +++++++++
 class.c                  |  1 +
 test/ruby/test_module.rb | 16 ++++++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index a3bdf46883..1526d1150c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Mon Aug 12 15:16:58 2013  Koichi Sasada  <ko1@atdot.net>
+
+	* class.c (rb_prepend_module): make T_ICLASS object shady because
+	  this T_ICLASS object seems to share method table with other class
+	  objects. It was causes WB miss.
+	  TODO: need to know the data structure.
+
+	* test/ruby/test_module.rb: add a test for WB miss.
+
 Mon Aug 12 13:47:54 2013  Zachary Scott  <e@zzak.io>
 
 	* process.c: [DOC] RDoc formatting of Process.clock_gettime
diff --git a/class.c b/class.c
index 04e9dcbc2c..f87d2bdcca 100644
--- a/class.c
+++ b/class.c
@@ -826,6 +826,7 @@ rb_prepend_module(VALUE klass, VALUE module)
     origin = RCLASS_ORIGIN(klass);
     if (origin == klass) {
 	origin = class_alloc(T_ICLASS, klass);
+	OBJ_WB_UNPROTECT(origin); /* TODO: conservertive shading. Need more survery. */
 	RCLASS_SET_SUPER(origin, RCLASS_SUPER(klass));
 	RCLASS_SET_SUPER(klass, origin);
 	RCLASS_ORIGIN(klass) = origin;
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index 361a6fe993..b0a33c8609 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -1760,4 +1760,20 @@ class TestModule < Test::Unit::TestCase
       self.#{method}
     INPUT
   end
+
+  def test_prepend_gc
+    assert_separately [], %{
+      module Foo
+      end
+      class Object
+        prepend Foo
+      end
+      GC.start     # make created T_ICLASS old (or remembered shady)
+      class Object # add methods into T_ICLASS (need WB if it is old)
+        def foo; end
+        attr_reader :bar
+      end
+      1_000_000.times{''} # cause GC
+    }
+  end
 end