synchronization of access tracker to avoid java-internal loop in TreeMap during shutdown

see http://forum.yacy-websuche.de/viewtopic.php?p=1178#p1178

git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@4017 6c8d7289-2bf4-0310-a012-ef5d649a1542

source/de/anomic/server/serverAbstractSwitch.java

@@ -174,6 +174,7 @@ public abstract class serverAbstractSwitch implements serverSwitch {
         if (accessPath == null) accessPath="NULL";
         TreeMap access = (TreeMap) accessTracker.get(host);
         if (access == null) access = new TreeMap();
+        synchronized (access) {
             access.put(new Long(System.currentTimeMillis()), accessPath);
 
             // write back to tracker
@@ -181,13 +182,14 @@ public abstract class serverAbstractSwitch implements serverSwitch {
                 accessTracker.put(host, clearTooOldAccess(access));
             } catch (ConcurrentModificationException e) {};
         }
+    }
     
     public TreeMap accessTrack(String host) {
         // returns mapping from Long(accesstime) to path
         
         TreeMap access = (TreeMap) accessTracker.get(host);
         if (access == null) return null;
-
+        synchronized (access) {
             // clear too old entries
             int oldsize = access.size();
             if ((access = clearTooOldAccess(access)).size() != oldsize) {
@@ -201,6 +203,7 @@ public abstract class serverAbstractSwitch implements serverSwitch {
         
             return access;
         }
+    }
     
     private TreeMap clearTooOldAccess(TreeMap access) {
         return new TreeMap(access.tailMap(new Long(System.currentTimeMillis() - maxTrackingTime)));