Switch to AtomicIntegerFieldUpdater and volatile int, instead of AtomicBoolean

Author: jbripley

rxjava-core/src/main/java/rx/schedulers/CachedThreadScheduler.java

@@ -23,7 +23,7 @@
 
 import java.util.Iterator;
 import java.util.concurrent.*;
-import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
 
 /* package */class CachedThreadScheduler extends Scheduler {
     private static final String WORKER_THREAD_NAME_PREFIX = "RxCachedThreadScheduler-";
@@ -109,15 +109,17 @@ public Worker createWorker() {
     private static class EventLoopWorker extends Scheduler.Worker {
         private final CompositeSubscription innerSubscription = new CompositeSubscription();
         private final PoolWorker poolWorker;
-        private final AtomicBoolean releasePoolWorkerOnce = new AtomicBoolean(false);
+        volatile int once;
+        static final AtomicIntegerFieldUpdater<EventLoopWorker> ONCE_UPDATER
+                = AtomicIntegerFieldUpdater.newUpdater(EventLoopWorker.class, "once");
 
         EventLoopWorker(PoolWorker poolWorker) {
             this.poolWorker = poolWorker;
         }
 
         @Override
         public void unsubscribe() {
-            if (releasePoolWorkerOnce.compareAndSet(false, true)) {
+            if (ONCE_UPDATER.compareAndSet(this, 0, 1)) {
                 // unsubscribe should be idempotent, so only do this once
                 CachedWorkerPool.INSTANCE.release(poolWorker);
             }