Add missing lock in `rb_gc_impl_undefine_finalizer`

The table is global so accesses must be synchronized.

1 files changed, 19 insertions, 0 deletions

diff --git a/test/objspace/test_ractor.rb b/test/objspace/test_ractor.rb
index 4901eeae2e..c5bb656da6 100644
--- a/test/objspace/test_ractor.rb
+++ b/test/objspace/test_ractor.rb
@@ -14,4 +14,23 @@ class TestObjSpaceRactor < Test::Unit::TestCase
       end
     RUBY
   end
+
+  def test_undefine_finalizer
+    assert_ractor(<<~'RUBY', require: 'objspace')
+      def fin
+        ->(id) { }
+      end
+      ractors = 5.times.map do
+        Ractor.new do
+          10_000.times do
+            o = Object.new
+            ObjectSpace.define_finalizer(o, fin)
+            ObjectSpace.undefine_finalizer(o)
+          end
+        end
+      end
+
+      ractors.each(&:take)
+    RUBY
+  end
 end