<li>Issue #255: ConcurrentModificationException with multiple threads in…

<li>Issue #255: ConcurrentModificationException with multiple threads in embedded mode and temporary LOBs

I think I've fixed this

h2/src/docsrc/html/changelog.html

@@ -21,6 +21,8 @@ Change Log
 
 <h2>Next Version (unreleased)</h2>
 <ul>
+<li>Issue #255: ConcurrentModificationException with multiple threads in embedded mode and temporary LOBs
+</li>
 <li>Issue #235: Anonymous SSL connections fail in many situations
 </li>
 <li>Fix race condition in FILE_LOCK=SOCKET, which could result in the watchdog thread not running  

h2/src/main/org/h2/engine/Engine.java

@@ -6,7 +6,6 @@
 package org.h2.engine;
 
 import java.util.HashMap;
-
 import org.h2.api.ErrorCode;
 import org.h2.command.CommandInterface;
 import org.h2.command.Parser;
@@ -189,46 +188,48 @@ public class Engine implements SessionFactory {
                 // ignore
             }
         }
-        session.setAllowLiterals(true);
-        DbSettings defaultSettings = DbSettings.getDefaultSettings();
-        for (String setting : ci.getKeys()) {
-            if (defaultSettings.containsKey(setting)) {
-                // database setting are only used when opening the database
-                continue;
-            }
-            String value = ci.getProperty(setting);
-            try {
-                CommandInterface command = session.prepareCommand(
-                        "SET " + Parser.quoteIdentifier(setting) + " " + value,
-                        Integer.MAX_VALUE);
-                command.executeUpdate();
-            } catch (DbException e) {
-                if (e.getErrorCode() == ErrorCode.ADMIN_RIGHTS_REQUIRED) {
-                    session.getTrace().error(e, "admin rights required; user: \"" +
-                            ci.getUserName() + "\"");
-                } else {
-                    session.getTrace().error(e, "");
+        synchronized (session) {
+            session.setAllowLiterals(true);
+            DbSettings defaultSettings = DbSettings.getDefaultSettings();
+            for (String setting : ci.getKeys()) {
+                if (defaultSettings.containsKey(setting)) {
+                    // database setting are only used when opening the database
+                    continue;
                 }
-                if (!ignoreUnknownSetting) {
-                    session.close();
-                    throw e;
+                String value = ci.getProperty(setting);
+                try {
+                    CommandInterface command = session.prepareCommand(
+                            "SET " + Parser.quoteIdentifier(setting) + " " + value,
+                            Integer.MAX_VALUE);
+                    command.executeUpdate();
+                } catch (DbException e) {
+                    if (e.getErrorCode() == ErrorCode.ADMIN_RIGHTS_REQUIRED) {
+                        session.getTrace().error(e, "admin rights required; user: \"" +
+                                ci.getUserName() + "\"");
+                    } else {
+                        session.getTrace().error(e, "");
+                    }
+                    if (!ignoreUnknownSetting) {
+                        session.close();
+                        throw e;
+                    }
                 }
             }
-        }
-        if (init != null) {
-            try {
-                CommandInterface command = session.prepareCommand(init,
-                        Integer.MAX_VALUE);
-                command.executeUpdate();
-            } catch (DbException e) {
-                if (!ignoreUnknownSetting) {
-                    session.close();
-                    throw e;
+            if (init != null) {
+                try {
+                    CommandInterface command = session.prepareCommand(init,
+                            Integer.MAX_VALUE);
+                    command.executeUpdate();
+                } catch (DbException e) {
+                    if (!ignoreUnknownSetting) {
+                        session.close();
+                        throw e;
+                    }
                 }
             }
+            session.setAllowLiterals(false);
+            session.commit(true);
         }
-        session.setAllowLiterals(false);
-        session.commit(true);
         return session;
     }
 

h2/src/main/org/h2/engine/Session.java

@@ -649,6 +649,11 @@ public class Session extends SessionWithState {
     }
 
     private void removeTemporaryLobs(boolean onTimeout) {
+        if (SysProperties.CHECK2) {
+            if (!Thread.holdsLock(this) && !Thread.holdsLock(getDatabase())) {
+                throw DbException.throwInternalError();
+            }
+        }
         if (temporaryLobs != null) {
             for (Value v : temporaryLobs) {
                 if (!v.isLinkedToTable()) {

h2/src/main/org/h2/engine/SessionRemote.java

@@ -581,7 +581,9 @@ public class SessionRemote extends SessionWithState implements DataHandler {
         }
         traceSystem.close();
         if (embedded != null) {
-            embedded.close();
+            synchronized (embedded) {
+                embedded.close();
+            }
             embedded = null;
         }
         if (closeError != null) {

h2/src/main/org/h2/server/TcpServerThread.java

@@ -14,7 +14,6 @@ import java.io.StringWriter;
 import java.net.Socket;
 import java.sql.SQLException;
 import java.util.ArrayList;
-
 import org.h2.api.ErrorCode;
 import org.h2.command.Command;
 import org.h2.engine.ConnectionInfo;
@@ -182,7 +181,9 @@ public class TcpServerThread implements Runnable {
                 server.traceError(e);
             }
             try {
-                session.close();
+                synchronized (session) {
+                    session.close();
+                }
                 server.removeConnection(threadId);
             } catch (RuntimeException e) {
                 if (closeError == null) {