8328611: Thread safety issue in com.sun.tools.jdi.ReferenceTypeImpl::…

…classObject

Reviewed-by: amenkov, sspitsyn

src/jdk.jdi/share/classes/com/sun/tools/jdi/ReferenceTypeImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -182,8 +182,7 @@ public int compareTo(ReferenceType object) {
 
     public String signature() {
         if (signature == null) {
-            // Does not need synchronization, since worst-case
-            // static info is fetched twice
+            // Does not need synchronization. Worst case is static info is fetched twice.
             if (vm.canGet1_5LanguageFeatures()) {
                 /*
                  * we might as well get both the signature and the
@@ -205,8 +204,7 @@ public String signature() {
     public String genericSignature() {
         // This gets both the signature and the generic signature
         if (vm.canGet1_5LanguageFeatures() && !genericSignatureGotten) {
-            // Does not need synchronization, since worst-case
-            // static info is fetched twice
+            // Does not need synchronization. Worst case is static info is fetched twice.
             JDWP.ReferenceType.SignatureWithGeneric result;
             try {
                 result = JDWP.ReferenceType.SignatureWithGeneric.
@@ -222,8 +220,7 @@ public String genericSignature() {
 
     public ClassLoaderReference classLoader() {
         if (!isClassLoaderCached) {
-            // Does not need synchronization, since worst-case
-            // static info is fetched twice
+            // Does not need synchronization. Worst case is static info is fetched twice.
             try {
                 classLoader = JDWP.ReferenceType.ClassLoader.
                     process(vm, this).classLoader;
@@ -239,9 +236,8 @@ public ModuleReference module() {
         if (module != null) {
             return module;
         }
-        // Does not need synchronization, since worst-case
-        // static info is fetched twice
         try {
+            // Does not need synchronization. Worst case is static info is fetched twice.
             ModuleReferenceImpl m = JDWP.ReferenceType.Module.
                 process(vm, this).module;
             module = vm.getModule(m.ref());
@@ -694,17 +690,12 @@ public Map<Field,Value> getValues(List<? extends Field> theFields) {
 
     public ClassObjectReference classObject() {
         if (classObject == null) {
-            // Are classObjects unique for an Object, or
-            // created each time? Is this spec'ed?
-            synchronized(this) {
-                if (classObject == null) {
-                    try {
-                        classObject = JDWP.ReferenceType.ClassObject.
-                            process(vm, this).classObject;
-                    } catch (JDWPException exc) {
-                        throw exc.toJDIException();
-                    }
-                }
+            // Does not need synchronization. Worst case is static info is fetched twice.
+            try {
+                classObject = JDWP.ReferenceType.ClassObject.
+                    process(vm, this).classObject;
+            } catch (JDWPException exc) {
+                throw exc.toJDIException();
             }
         }
         return classObject;
@@ -747,8 +738,7 @@ public List<String> sourcePaths(String stratumID)
     String baseSourceName() throws AbsentInformationException {
         String bsn = baseSourceName;
         if (bsn == null) {
-            // Does not need synchronization, since worst-case
-            // static info is fetched twice
+            // Does not need synchronization. Worst case is static info is fetched twice.
             try {
                 bsn = JDWP.ReferenceType.SourceFile.
                     process(vm, this).sourceFile;
@@ -1065,13 +1055,12 @@ public byte[] constantPool() {
         }
     }
 
-    // Does not need synchronization, since worst-case
-    // static info is fetched twice
     void getModifiers() {
         if (modifiers != -1) {
             return;
         }
         try {
+            // Does not need synchronization. Worst case is static info is fetched twice.
             modifiers = JDWP.ReferenceType.Modifiers.
                                   process(vm, this).modBits;
         } catch (JDWPException exc) {