8368500: ContextClassLoader cannot be reset on threads in ForkJoinPool.commonPool()

Reviewed-by: vklang, alanb

Author: johnyjose30

src/java.base/share/classes/java/util/concurrent/ForkJoinWorkerThread.java

@@ -267,10 +267,8 @@ public void setUncaughtExceptionHandler(UncaughtExceptionHandler x) { }
 
         @Override // to record changes
         public void setContextClassLoader(ClassLoader cl) {
-            if (ClassLoader.getSystemClassLoader() != cl) {
-                resetCCL = true;
-                super.setContextClassLoader(cl);
-            }
+            resetCCL = ClassLoader.getSystemClassLoader() != cl;
+            super.setContextClassLoader(cl);
         }
 
         @Override // to re-establish CCL if necessary

test/jdk/java/util/concurrent/forkjoin/ContextClassLoaderTest.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2025, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8368500
+ * @run junit/othervm ContextClassLoaderTest
+ * @summary Check the context classloader is reset
+ */
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.util.concurrent.Future;
+import java.util.concurrent.ForkJoinPool;
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+class ContextClassLoaderTest {
+
+    @Test
+    void testContextClassLoaderIsSetAndRestored() throws Exception {
+        Future<?> future = ForkJoinPool.commonPool().submit(() -> {
+            Thread thread = Thread.currentThread();
+            ClassLoader originalCCL = thread.getContextClassLoader();
+            ClassLoader customCCL = new URLClassLoader(new URL[0], originalCCL);
+            // Set custom context classloader and verify it
+            thread.setContextClassLoader(customCCL);
+            assertSame(customCCL, thread.getContextClassLoader(), "Custom context class loader not set");
+
+            // Reset to original and verify restoration
+            thread.setContextClassLoader(originalCCL);
+            assertSame(originalCCL, thread.getContextClassLoader(), "Original context class loader not restored");
+        });
+        future.get();
+    }
+}
+