MVStore: avoid deadlocks

h2/src/main/org/h2/mvstore/MVStore.java

@@ -169,7 +169,8 @@ public class MVStore {
      * is the unsaved version, the value is the map of chunks. The maps contains
      * the number of freed entries per chunk. Access is synchronized.
      */
-    private final HashMap<Long, HashMap<Integer, Chunk>> freedPageSpace = New.hashMap();
+    private final ConcurrentHashMap<Long, HashMap<Integer, Chunk>> freedPageSpace = 
+            new ConcurrentHashMap<Long, HashMap<Integer, Chunk>>();
 
     /**
      * The metadata map.
@@ -1056,10 +1057,10 @@ public class MVStore {
      */
     private Set<Chunk> applyFreedSpace(long storeVersion, long time) {
         Set<Chunk> removedChunks = New.hashSet();
-        synchronized (freedPageSpace) {
         while (true) {
             ArrayList<Chunk> modified = New.arrayList();
-                for (Iterator<Long> it = freedPageSpace.keySet().iterator(); it.hasNext();) {
+            ArrayList<Long> keys = new ArrayList<Long>(freedPageSpace.keySet());
+            for (Iterator<Long> it = keys.iterator(); it.hasNext();) {
                 long v = it.next();
                 if (v > storeVersion) {
                     continue;
@@ -1090,7 +1091,7 @@ public class MVStore {
                     }
                     modified.add(c);
                 }
-                    it.remove();
+                freedPageSpace.remove(v);
             }
             for (Chunk c : modified) {
                 if (c.maxLengthLive == 0) {
@@ -1110,7 +1111,6 @@ public class MVStore {
                 break;
             }
         }
-        }
         return removedChunks;
     }
 
@@ -1501,7 +1501,6 @@ public class MVStore {
     }
 
     private void registerFreePage(long version, int chunkId, long maxLengthLive, int pageCount) {
-        synchronized (freedPageSpace) {
         HashMap<Integer, Chunk>freed = freedPageSpace.get(version);
         if (freed == null) {
             freed = New.hashMap();
@@ -1515,7 +1514,6 @@ public class MVStore {
         f.maxLengthLive -= maxLengthLive;
         f.pageCountLive -= pageCount;
     }
-    }
 
     Compressor getCompressor() {
         return compressor;
@@ -1741,9 +1739,7 @@ public class MVStore {
                 fileStore.clear();
             }
             maps.clear();
-            synchronized (freedPageSpace) {
             freedPageSpace.clear();
-            }
             currentVersion = version;
             setWriteVersion(version);
             lastCommittedVersion = version;
@@ -1831,7 +1827,6 @@ public class MVStore {
     }
 
     private void revertTemp(long storeVersion) {
-        synchronized (freedPageSpace) {
         for (Iterator<Long> it = freedPageSpace.keySet().iterator(); it.hasNext();) {
             long v = it.next();
             if (v > storeVersion) {
@@ -1839,7 +1834,6 @@ public class MVStore {
             }
             it.remove();
         }
-        }
         for (MVMap<?, ?> m : maps.values()) {
             m.removeUnusedOldVersions();
         }