From 1a854f667303476530358acd336911d5dc3bf501 Mon Sep 17 00:00:00 2001
From: vlivanov <unknown>
Date: Tue, 3 Jun 2014 16:38:14 +0400
Subject: [PATCH] 8005873: JRuby test_respond_to.rb asserts with: MT-unsafe
 modification of inline cache Reviewed-by: vlivanov, jrose, psandoz
 Contributed-by: tobias.hartmann@oracle.com

---
 src/share/classes/java/lang/invoke/LambdaForm.java       | 2 +-
 src/share/classes/java/lang/invoke/MethodHandleImpl.java | 3 +--
 src/share/classes/java/lang/invoke/MethodTypeForm.java   | 6 ++++--
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/share/classes/java/lang/invoke/LambdaForm.java b/src/share/classes/java/lang/invoke/LambdaForm.java
index a5e40ed52..a8291e273 100644
--- a/src/share/classes/java/lang/invoke/LambdaForm.java
+++ b/src/share/classes/java/lang/invoke/LambdaForm.java
@@ -482,7 +482,7 @@ class LambdaForm {
                 assert(m.getName().equals("interpret" + sig.substring(sig.indexOf('_'))));
                 LambdaForm form = new LambdaForm(sig);
                 form.vmentry = m;
-                mt.form().setCachedLambdaForm(MethodTypeForm.LF_COUNTER, form);
+                form = mt.form().setCachedLambdaForm(MethodTypeForm.LF_COUNTER, form);
                 // FIXME: get rid of PREPARED_FORMS; use MethodTypeForm cache only
                 forms.put(sig, form);
             }
diff --git a/src/share/classes/java/lang/invoke/MethodHandleImpl.java b/src/share/classes/java/lang/invoke/MethodHandleImpl.java
index cdf6e5a75..ee1584f80 100644
--- a/src/share/classes/java/lang/invoke/MethodHandleImpl.java
+++ b/src/share/classes/java/lang/invoke/MethodHandleImpl.java
@@ -692,8 +692,7 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
 
         lform = new LambdaForm("guardWithCatch", lambdaType.parameterCount(), names);
 
-        basicType.form().setCachedLambdaForm(MethodTypeForm.LF_GWC, lform);
-        return lform;
+        return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_GWC, lform);
     }
 
     static
diff --git a/src/share/classes/java/lang/invoke/MethodTypeForm.java b/src/share/classes/java/lang/invoke/MethodTypeForm.java
index ee5e6221b..d34a2998c 100644
--- a/src/share/classes/java/lang/invoke/MethodTypeForm.java
+++ b/src/share/classes/java/lang/invoke/MethodTypeForm.java
@@ -91,8 +91,10 @@ final class MethodTypeForm {
         return lambdaForms[which];
     }
 
-    public LambdaForm setCachedLambdaForm(int which, LambdaForm form) {
-        // Should we perform some sort of CAS, to avoid racy duplication?
+    synchronized public LambdaForm setCachedLambdaForm(int which, LambdaForm form) {
+        // Simulate a CAS, to avoid racy duplication of results.
+        LambdaForm prev = lambdaForms[which];
+        if (prev != null) return prev;
         return lambdaForms[which] = form;
     }
 
-- 
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