Synchronize calls to Autoload#resolve

Yorick Peterse · Yorick Peterse · commit b57399f8f44c · 2015-04-24T22:38:43.000+02:00
When multiple threads attempt to resolve an autoload definition there's nothing guarding the checks/sets for the "@loaded" and "@thread" instance variables. By using Rubinius.synchronize we can ensure that only 1 thread at a time can autoload a constant without having to worry about recursive locking.
diff --git a/kernel/common/autoload.rb b/kernel/common/autoload.rb
@@ -49,10 +49,12 @@ def call(under, honor_require=false)
   end
 
   def resolve
-    unless @loaded && @thread == Thread.current
-      @loaded = true
-      @thread = Thread.current
-      Rubinius::CodeLoader.require @path
+    Rubinius.synchronize(self) do
+      unless @loaded && @thread == Thread.current
+        @loaded = true
+        @thread = Thread.current
+        Rubinius::CodeLoader.require @path
+      end
     end
   end
 
