Revert "replace Cleaner API with a local Thread"

This reverts commit 6e877ff.

Author: headius

core/src/main/java/org/jruby/embed/internal/ThreadLocalContext.java

@@ -29,9 +29,8 @@
  */
 package org.jruby.embed.internal;
 
-import java.lang.ref.PhantomReference;
-import java.lang.ref.Reference;
-import java.lang.ref.ReferenceQueue;
+import java.lang.ref.Cleaner;
+import java.lang.ref.Cleaner.Cleanable;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Supplier;
@@ -44,8 +43,8 @@
  */
 class ThreadLocalContext {
 	private final ConcurrentHashMap<LocalContextCleaningAction, Object> contextRefs = new ConcurrentHashMap<>();
+	private final Cleaner cleaner = Cleaner.create();
 	private final Supplier<LocalContext> localContextFactory;
-	private final Cleaner cleaner = new Cleaner();
 
 	public ThreadLocalContext(final Supplier<LocalContext> localContextFactory) {
 		this.localContextFactory = localContextFactory;
@@ -62,13 +61,13 @@ protected AtomicReference<LocalContextCleaningAction> initialValue() {
 			// GC'd (i.e. when this class gets GC'd because terminate() was never called).
 			// see ThreadLocal JavaDoc: ref will stay reachable "as long as the thread is
 			// alive and the ThreadLocal instance is accessible"
-			ctx.register(ref, cleaner);
+			final Cleanable cleanable = cleaner.register(ref, ctx);
 			if (contextHolder == null)
 				// boundary case if we're already terminating: clean up immediately, because
 				// there is no more cleanup thread to do that later
 				// the returned context will be null, but that's to be expected when operating
 				// on an object that has been terminated
-				ctx.run();
+				cleanable.clean();
 			return ref;
 		}
 	};
@@ -78,7 +77,6 @@ public LocalContext get() {
 	}
 
 	public void terminate() {
-		cleaner.interrupt();
 		contextHolder = null;
 		for (final LocalContextCleaningAction ref : contextRefs.keySet())
 			ref.run();
@@ -90,14 +88,11 @@ public void terminate() {
 	 * everything that is GC-reachable from them will stay reachable until the
 	 * cleaning action has been run.
 	 */
-	static class LocalContextCleaningAction extends AtomicReference<LocalContext> implements Runnable {
+	private static class LocalContextCleaningAction extends AtomicReference<LocalContext> implements Runnable {
 		private static final long serialVersionUID = 1L;
 
 		private final ConcurrentHashMap<LocalContextCleaningAction, Object> contextRefs;
 
-		@SuppressWarnings("unused") // only used to make sure the PhantomReference doesn't get GC'd
-		private CleanerReference phantomReference;
-
 		private LocalContextCleaningAction(final ConcurrentHashMap<LocalContextCleaningAction, Object> contextRefs,
 				final LocalContext context) {
 			super(context);
@@ -116,42 +111,5 @@ public void run() {
 				lc.remove();
 			contextRefs.remove(this);
 		}
-
-		private void register(final AtomicReference<LocalContextCleaningAction> ref, final Cleaner cleaner) {
-			phantomReference = new CleanerReference(ref, cleaner.q, this);
-		}
-	}
-
-	private static class CleanerReference extends PhantomReference<AtomicReference<LocalContextCleaningAction>> {
-		private Runnable cleanup;
-
-		public CleanerReference(final AtomicReference<LocalContextCleaningAction> referent,
-				final ReferenceQueue<AtomicReference<LocalContextCleaningAction>> q, final Runnable cleanup) {
-			super(referent, q);
-			this.cleanup = cleanup;
-		}
-	}
-
-	private static class Cleaner extends Thread {
-		private final ReferenceQueue<AtomicReference<LocalContextCleaningAction>> q = new ReferenceQueue<>();
-
-		public Cleaner() {
-			setName("JRuby-ThreadLocalContext-Cleaner-" + getId());
-			setDaemon(true);
-			start();
-		}
-
-		@Override
-		public void run() {
-			while (!interrupted()) {
-				final Reference<?> cleanable;
-				try {
-					cleanable = q.remove();
-				} catch (InterruptedException e) {
-					break;
-				}
-				((CleanerReference) cleanable).cleanup.run();
-			}
-		}
 	}
 }