From ea197f483ede1a9216e93a500c0ef01aef0d91f3 Mon Sep 17 00:00:00 2001
From: Chris Dennis <chris.w.dennis@ibm.com>
Date: Mon, 14 Jul 2025 11:06:09 -0400
Subject: [PATCH] 8362123: ClassLoader Leak via
 Executors.newSingleThreadExecutor(...)

Executors shutdown via `shutdownNow()` should have their cleanables cleaned to
prevent a classloader leak. This can happen if a classloader exists that both
references the wrapped executor and is referenced by the delegate executor.
---
 .../java/util/concurrent/Executors.java       |  7 +++
 .../concurrent/Executors/AutoShutdown.java    | 48 ++++++++++++++++++-
 2 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/src/java.base/share/classes/java/util/concurrent/Executors.java b/src/java.base/share/classes/java/util/concurrent/Executors.java
index ef3d634801090..8b339cf83ef3d 100644
--- a/src/java.base/share/classes/java/util/concurrent/Executors.java
+++ b/src/java.base/share/classes/java/util/concurrent/Executors.java
@@ -755,6 +755,13 @@ public void shutdown() {
             super.shutdown();
             cleanable.clean();  // unregisters the cleanable
         }
+
+        @Override
+        public List<Runnable> shutdownNow() {
+            List<Runnable> unexecuted = super.shutdownNow();
+            cleanable.clean();  // unregisters the cleanable
+            return unexecuted;
+        }
     }
 
     /**
diff --git a/test/jdk/java/util/concurrent/Executors/AutoShutdown.java b/test/jdk/java/util/concurrent/Executors/AutoShutdown.java
index 2b7fa7b883fa5..9ef73128a2c92 100644
--- a/test/jdk/java/util/concurrent/Executors/AutoShutdown.java
+++ b/test/jdk/java/util/concurrent/Executors/AutoShutdown.java
@@ -23,23 +23,32 @@
 
 /*
  * @test
- * @bug 6399443 8302899
+ * @bug 6399443 8302899 8362123
  * @summary Test that Executors.newSingleThreadExecutor wraps an ExecutorService that
  *    automatically shuts down and terminates when the wrapper is GC'ed
+ * @library /test/lib/
  * @modules java.base/java.util.concurrent:+open
  * @run junit AutoShutdown
  */
 
+import java.lang.ref.PhantomReference;
+import java.lang.ref.Reference;
+import java.lang.ref.ReferenceQueue;
 import java.lang.reflect.Field;
 import java.time.Duration;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Consumer;
 import java.util.function.Supplier;
 import java.util.stream.Stream;
 import java.util.stream.IntStream;
 
+import jdk.test.lib.Utils;
+import jdk.test.lib.util.ForceGC;
+
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.MethodSource;
@@ -61,6 +70,10 @@ private static Stream<Arguments> executorAndQueuedTaskCounts() {
                 .mapToObj(i -> Arguments.of(s, i)));
     }
 
+    private static Stream<Arguments> shutdownMethods() {
+        return Stream.<Consumer<ExecutorService>>of(e -> e.shutdown(), e -> e.shutdownNow()).map(Arguments::of);
+    }
+
     /**
      * SingleThreadExecutor with no worker threads.
      */
@@ -110,6 +123,21 @@ void testActiveWorker(Supplier<ExecutorService> supplier,int queuedTaskCount) th
         assertEquals(ntasks, completedTaskCount.get());
     }
 
+    @ParameterizedTest
+    @MethodSource("shutdownMethods")
+    void testShutdownUnlinksCleaner(Consumer<ExecutorService> shutdown) throws Exception {
+        ClassLoader classLoader = Utils.getTestClassPathURLClassLoader(ClassLoader.getPlatformClassLoader());
+
+        ReferenceQueue<?> queue = new ReferenceQueue<>();
+        Reference<?> reference = new PhantomReference(classLoader, queue);
+
+        classLoader.loadClass("AutoShutdown$IsolatedClass").getDeclaredMethod("shutdown", Consumer.class).invoke(null, shutdown);
+        classLoader = null;
+
+        assertTrue(ForceGC.wait(() -> queue.poll() != null));
+        Reference.reachabilityFence(reference);
+    }
+
     /**
      * Returns the delegate for the given ExecutorService. The given ExecutorService
      * must be a Executors$DelegatedExecutorService.
@@ -132,5 +160,21 @@ private void gcAndAwaitTermination(ExecutorService executor) throws Exception {
             terminated = executor.awaitTermination(100, TimeUnit.MILLISECONDS);
         }
     }
-}
 
+    public static class IsolatedClass {
+
+        private static final ExecutorService executor = Executors.newSingleThreadExecutor(new IsolatedThreadFactory());
+
+        public static void shutdown(Consumer<ExecutorService> shutdown) {
+            shutdown.accept(executor);
+        }
+    }
+
+    public static class IsolatedThreadFactory implements ThreadFactory {
+
+        @Override
+        public Thread newThread(Runnable r) {
+            return new Thread(r);
+        }
+    }
+}