Fix a concurency problem when no tracer is enabled.

- Replace newDummyInstance() by a getDummyInstance in StatisticId
- Remove HashMap from DummyTracer to keep dummy instances

This HashMap has to be synchronized, but we want to have a very light
implementation of DummyTracer. So, we prefer to keep multiple instances
of dummy statistics than having a ConcurrentHashMap.

Change-Id: I4e8ec3aaf42ac6843626e4d2432db1212b03a0ed

2 files changed, 9 insertions, 18 deletions

diff --git a/sched/src/com/android/sched/util/log/DummyTracer.java b/sched/src/com/android/sched/util/log/DummyTracer.java
index 4d27c70..5851a6d 100644
--- a/sched/src/com/android/sched/util/log/DummyTracer.java
+++ b/sched/src/com/android/sched/util/log/DummyTracer.java
@@ -25,9 +25,7 @@ import com.android.sched.util.log.tracer.watcher.ObjectWatcher;
 
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
 
 import javax.annotation.Nonnegative;
 import javax.annotation.Nonnull;
@@ -44,10 +42,6 @@ public final class DummyTracer implements Tracer {
    * Represents event.
    */
   public static class DummyTracerEvent implements Event {
-    @Nonnull
-    private final Map<StatisticId<? extends Statistic>, Statistic> statisticsById =
-        new HashMap<StatisticId<? extends Statistic>, Statistic>();
-
     DummyTracerEvent() {
     }
 
@@ -98,15 +92,7 @@ public final class DummyTracer implements Tracer {
     @Override
     @Nonnull
     public <T extends Statistic> T getStatistic(@Nonnull StatisticId<T> id) {
-      @SuppressWarnings("unchecked")
-      T statistic = (T) statisticsById.get(id);
-
-      if (statistic == null) {
-        statistic = id.newDummyInstance();
-        statisticsById.put(id, statistic);
-      }
-
-      return statistic;
+      return id.getDummyInstance();
     }
   }
 
diff --git a/sched/src/com/android/sched/util/log/stats/StatisticId.java b/sched/src/com/android/sched/util/log/stats/StatisticId.java
index 597a5a3..30444c5 100644
--- a/sched/src/com/android/sched/util/log/stats/StatisticId.java
+++ b/sched/src/com/android/sched/util/log/stats/StatisticId.java
@@ -38,6 +38,9 @@ public class StatisticId<T extends Statistic> {
       new ConcurrentHashMap<Class<? extends Statistic>, Class<? extends Statistic>>();
 
   @Nonnull
+  private final T dummyInstance;
+
+  @Nonnull
   private final String name;
 
   @Nonnull
@@ -57,10 +60,12 @@ public class StatisticId<T extends Statistic> {
     regularFactory = new ReflectFactory<T>(regularClass, false, StatisticId.class);
     dummyFactory   = new ReflectFactory<T>(dummyClass,   false, StatisticId.class);
 
+    dummyInstance = dummyFactory.create(this);
+
     // Followings are deprecated, to be removed
 
     if (!dummies.containsKey(dummyClass)) {
-      dummies.put(dummyClass, newDummyInstance());
+      dummies.put(dummyClass, dummyInstance);
       regulars.put(dummyClass, regularClass);
     }
   }
@@ -81,8 +86,8 @@ public class StatisticId<T extends Statistic> {
   }
 
   @Nonnull
-  public T newDummyInstance() {
-    return dummyFactory.create(this);
+  public T getDummyInstance() {
+    return dummyInstance;
   }
 
   @Nonnull