avoid deadlocks by letting TrackBasedEstimationWindTrackImpl's getEstimatedWind be unsynchronized

java/com.sap.sailing.domain/src/com/sap/sailing/domain/tracking/TrackedRace.java

@@ -214,7 +214,10 @@ public interface TrackedRace {
     
     /**
      * Determines whether the <code>competitor</code> is sailing on port or starboard tack at the
-     * <code>timePoint</code> requested.
+     * <code>timePoint</code> requested. Note that this will have to retrieve information about the wind.
+     * This, in turn, can lead to the current thread obtaining the monitor of the various wind tracks,
+     * and, if the {@link WindSource#TRACK_BASED_ESTIMATION} source is used, also the monitors of the
+     * competitors' GPS tracks.
      */
     Tack getTack(Competitor competitor, TimePoint timePoint);
 

java/com.sap.sailing.domain/src/com/sap/sailing/domain/tracking/impl/TrackBasedEstimationWindTrackImpl.java

@@ -63,7 +63,7 @@ public class TrackBasedEstimationWindTrackImpl extends WindTrackImpl {
      * time point is used instead. If both time points are not known, <code>null</code> is returned immediately.
      */
     @Override
-    public synchronized Wind getEstimatedWind(Position p, TimePoint at) {
+    public Wind getEstimatedWind(Position p, TimePoint at) {
         Wind result = null;
         TimePoint adjustedAt;
         TimePoint raceStartTimePoint = trackedRace.getStart();
@@ -88,7 +88,9 @@ public class TrackBasedEstimationWindTrackImpl extends WindTrackImpl {
             }
         }
         if (adjustedAt != null) {
-            result = super.getEstimatedWind(p, adjustedAt);
+            // we can use the unsynchronized version here because our getInternalFixes() method operates
+            // only on a virtual sequence of wind fixes where no concurrency issues have to be observed
+            result = getEstimatedWindUnsynchronized(p, adjustedAt);
         }
         return result;
     }

java/com.sap.sailing.domain/src/com/sap/sailing/domain/tracking/impl/WindTrackImpl.java

@@ -107,6 +107,16 @@ public class WindTrackImpl extends TrackImpl<Wind> implements WindTrack {
      */
     @Override
     public synchronized Wind getEstimatedWind(Position p, TimePoint at) {
+        return getEstimatedWindUnsynchronized(p, at);
+    }
+    
+    /**
+     * This method implements the functionality of the {@link #getEstimatedWind(Position, TimePoint)} interface
+     * method. However, not being <code>synchronized</code>, it does not obtain this object's monitor. Subclasses
+     * may use this carefully if they can guarantee there are no concurrency issues with the internal fixes
+     * while iterating over the result of {@link #getInternalFixes()}.
+     */
+    protected Wind getEstimatedWindUnsynchronized(Position p, TimePoint at) {
         DummyWind atTimed = new DummyWind(at);
         NavigableSet<Wind> beforeSet = getInternalFixes().headSet(atTimed, /* inclusive */ true);
         NavigableSet<Wind> afterSet = getInternalFixes().tailSet(atTimed, /* inclusive */ true);