Fix deadlocks due to activation: db.activate() uses the db.lock(), so

we cannot use that for transaction-locking anymore since we have no
clear locking order policy for activate() - we now use our own
transaction lock.

src/plugins/WebOfTrust/Configuration.java

@@ -52,7 +52,7 @@ protected Configuration(WebOfTrust myWebOfTrust) {
 	 * because the user interface will usually change many values at once.
 	 */
 	public synchronized void storeAndCommit() {
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 			try {
 				checkedActivate(4);
 

src/plugins/WebOfTrust/Identity.java

@@ -780,7 +780,7 @@ protected void storeWithoutCommit() {
 	 */
 	public final void storeAndCommit() {
 		synchronized(mWebOfTrust) {
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 			try {
 				storeWithoutCommit();
 				checkedCommit(this);

src/plugins/WebOfTrust/IdentityFetcher.java

@@ -200,7 +200,7 @@ private ObjectSet<IdentityFetcherCommand> getCommands(final Class<? extends Iden
 	}
 
 	private synchronized void deleteAllCommands() {
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 			try {
 				if(logDEBUG) Logger.debug(this, "Deleting all identity fetcher commands ...");
 
@@ -302,7 +302,7 @@ public int getPriority() {
 	public void run() {
 		synchronized(mWoT) { // Lock needed because we do getIdentityByID() in fetch()
 		synchronized(this) {
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 			try  {
 				if(logDEBUG) Logger.debug(this, "Processing identity fetcher commands ...");
 

src/plugins/WebOfTrust/Persistent.java

@@ -53,6 +53,12 @@ public abstract class Persistent {
 	 */
 	protected final Date mCreationDate = CurrentTimeUTC.get();
 
+	/**
+	 * The object used for locking transactions.
+	 * Since we only support one open database at a moment there is only one.
+	 */
+	private static transient final Object mTransactionLock = new Object();
+
 	/* These booleans are used for preventing the construction of log-strings if logging is disabled (for saving some cpu cycles) */
 
 	protected static transient volatile boolean logDEBUG = false;
@@ -108,6 +114,18 @@ public final void initializeTransient(final WebOfTrust myWebOfTrust) {
 		mWebOfTrust = myWebOfTrust;
 		mDB = mWebOfTrust.getDatabase();
 	}
+
+	/**
+	 * Returns the lock for creating a transaction.
+	 * A proper transaction typically looks like this:
+	 * synchronized(Persistent.transactionLock(db)) { try { ... do stuff ... Persistent.checkedCommit() } catch(RuntimeException e) { Persistent.checkedRollback(); } }
+	 * 
+	 * The db parameter is currently ignored - the same lock will be returned for all databases!
+	 * We don't need multi-database support in Freetalk yet.
+	 */
+	public static final Object transactionLock(ExtObjectContainer db) {
+		return mTransactionLock;
+	}
 
 	/**
 	 * Only to be used by the extending classes, not to be called from the outside.
@@ -215,7 +233,7 @@ public final void throwIfNotStored() {
 	/**
 	 * This is one of the only functions which outside classes should use.  Rolls back the current transaction, logs the passed exception and throws it.
 	 * The call to this function must be embedded in a transaction, that is a block of:<br />
-	 * synchronized(mDB.lock()) {<br />
+	 * synchronized(Persistent.transactionLock(mDB)) {<br />
 	 * 	try { object.storeWithoutCommit(); object.checkedCommit(this); }<br />
 	 * 	catch(RuntimeException e) { Persistent.checkedRollback(mDB, this, e); }<br />
 	 * } 
@@ -233,7 +251,7 @@ public static final void checkedRollback(final ExtObjectContainer db, final Obje
 	/**
 	 * This is one of the only functions which outside classes should use.  Rolls back the current transaction, logs the passed exception and throws it.
 	 * The call to this function must be embedded in a transaction, that is a block of:<br />
-	 * synchronized(mDB.lock()) {<br />
+	 * synchronized(Persistent.transactionLock(mDB)) {<br />
 	 * 	try { object.storeWithoutCommit(); object.checkedCommit(this); }<br />
 	 * 	catch(RuntimeException e) { Persistent.checkedRollbackAndThrow(mDB, this, e); }<br />
 	 * } 
@@ -275,7 +293,7 @@ protected void storeWithoutCommit(final int activationDepth) {
 	/**
 	 * This is one of the only functions which outside classes should use. It is used for storing the object.
 	 * The call to this function must be embedded in a transaction, that is a block of:<br />
-	 * synchronized(mDB.lock()) {<br />
+	 * synchronized(Persistent.transactionLock(mDB)) {<br />
 	 * 	try { object.storeWithoutCommit(); object.checkedCommit(this); }<br />
 	 * 	catch(RuntimeException e) { Persistent.checkedRollbackAndThrow(mDB, this, e); }<br />
 	 * } 
@@ -307,7 +325,7 @@ protected void deleteWithoutCommit(final int activationDepth) {
 	/**
 	 * This is one of the only functions which outside classes should use. It is used for deleting the object.
 	 * The call to this function must be embedded in a transaction, that is a block of:<br />
-	 * synchronized(mDB.lock()) {<br />
+	 * synchronized(Persistent.transactionLock(mDB)) {<br />
 	 * 	try { object.storeWithoutCommit(); object.checkedCommit(this); }<br />
 	 * 	catch(RuntimeException e) { Persistent.checkedRollbackAndThrow(mDB, this, e); }<br />
 	 * } 
@@ -320,7 +338,7 @@ protected void deleteWithoutCommit() {
 	/**
 	 * This is one of the only functions which outside classes should use. It is used for committing the transaction. 
 	 * The call to this function must be embedded in a transaction, that is a block of:<br />
-	 * synchronized(mDB.lock()) {<br />
+	 * synchronized(Persistent.transactionLock(mDB)) {<br />
 	 * 	try { object.storeWithoutCommit(); Persistent.checkedCommit(mDB, this); }<br />
 	 * 	catch(RuntimeException e) { Persistent.checkedRollbackAndThrow(mDB, this, e); }<br />
 	 * } 
@@ -335,7 +353,7 @@ public static final void checkedCommit(final ExtObjectContainer db, final Object
 	/**
 	 * This is one of the only functions which outside classes should use. It is used for committing the transaction.
 	 * The call to this function must be embedded in a transaction, that is a block of:<br />
-	 * synchronized(mDB.lock()) {<br />
+	 * synchronized(Persistent.transactionLock(mDB)) {<br />
 	 * 	try { object.storeWithoutCommit(); object.checkedCommit(this); }<br />
 	 * 	catch(RuntimeException e) { Persistent.checkedRollbackAndThrow(mDB, this, e); }<br />
 	 * } 

src/plugins/WebOfTrust/WebOfTrust.java

@@ -202,7 +202,7 @@ public boolean realTimeFlag() {
 			// TODO: Don't do this as soon as we are sure that score computation works.
 			Logger.normal(this, "Veriying all stored scores ...");
 			synchronized(this) {
-			synchronized(mDB.lock()) {
+			synchronized(Persistent.transactionLock(mDB)) {
 				try {
 					computeAllScoresWithoutCommit();
 					Persistent.checkedCommit(mDB, this);
@@ -404,7 +404,7 @@ private synchronized void verifyDatabaseIntegrity() {
 	 * Debug function for deleting duplicate identities etc. which might have been created due to bugs :)
 	 */
 	private synchronized void deleteDuplicateObjects() {
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 		try {
 			HashSet<String> deleted = new HashSet<String>();
 
@@ -433,7 +433,7 @@ private synchronized void deleteDuplicateObjects() {
 		}
 		}
 
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 		try {
 		if(logDEBUG) Logger.debug(this, "Searching for duplicate Trust objects ...");
 
@@ -471,7 +471,7 @@ private synchronized void deleteDuplicateObjects() {
 	 * Debug function for deleting trusts or scores of which one of the involved partners is missing.
 	 */
 	private synchronized void deleteOrphanObjects() {
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 			try {
 				boolean orphanTrustFound = false;
 
@@ -502,7 +502,7 @@ private synchronized void deleteOrphanObjects() {
 			}
 		}
 
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 			try {
 				boolean orphanScoresFound = false;
 
@@ -958,7 +958,7 @@ public void terminate() {
 				/* TODO: At 2009-06-15, it does not seem possible to ask db4o for whether a transaction is pending.
 				 * If it becomes possible some day, we should check that here, and log an error if there is an uncommitted transaction. 
 				 * - All transactions should be committed after obtaining the lock() on the database. */
-				synchronized(mDB.lock()) {
+				synchronized(Persistent.transactionLock(mDB)) {
 					System.gc();
 					mDB.rollback();
 					System.gc(); 
@@ -1511,7 +1511,7 @@ public ObjectSet<Trust> getAllTrusts() {
 	 * It creates or updates an existing Trust object and make the trustee compute its {@link Score}.
 	 * 
 	 * This function does neither lock the database nor commit the transaction. You have to surround it with
-	 * synchronized(mDB.lock()) {
+	 * synchronized(Persistent.transactionLock(mDB)) {
 	 *     try { ... setTrustWithoutCommit(...); mDB.commit(); }
 	 *     catch(RuntimeException e) { System.gc(); mDB.rollback(); throw e; }
 	 * }
@@ -1555,7 +1555,7 @@ protected synchronized void setTrustWithoutCommit(Identity truster, Identity tru
 	synchronized void setTrust(OwnIdentity truster, Identity trustee, byte newValue, String newComment)
 		throws InvalidParameterException {
 
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 			try {
 				setTrustWithoutCommit(truster, trustee, newValue, newComment);
 				Persistent.checkedCommit(mDB, this);
@@ -1567,7 +1567,7 @@ synchronized void setTrust(OwnIdentity truster, Identity trustee, byte newValue,
 	}
 
 	protected synchronized void removeTrust(OwnIdentity truster, Identity trustee) {
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 			try  {
 				removeTrustWithoutCommit(truster, trustee);
 				Persistent.checkedCommit(mDB, this);
@@ -1582,7 +1582,7 @@ protected synchronized void removeTrust(OwnIdentity truster, Identity trustee) {
 	 * Deletes a trust object.
 	 * 
 	 * This function does neither lock the database nor commit the transaction. You have to surround it with
-	 * synchronized(mDB.lock()) {
+	 * synchronized(Persistent.transactionLock(mDB)) {
 	 *     try { ... removeTrustWithoutCommit(...); mDB.commit(); }
 	 *     catch(RuntimeException e) { System.gc(); mDB.rollback(); throw e; }
 	 * }
@@ -1607,7 +1607,7 @@ protected synchronized void removeTrustWithoutCommit(OwnIdentity truster, Identi
 	/**
 	 * 
 	 * This function does neither lock the database nor commit the transaction. You have to surround it with
-	 * synchronized(mDB.lock()) {
+	 * synchronized(Persistent.transactionLock(mDB)) {
 	 *     try { ... setTrustWithoutCommit(...); mDB.commit(); }
 	 *     catch(RuntimeException e) { System.gc(); mDB.rollback(); throw e; }
 	 * }
@@ -1625,7 +1625,7 @@ protected synchronized void removeTrustWithoutCommit(Trust trust) {
 	 * The score will have a rank of 0, a capacity of 100 (= 100 percent) and a score value of Integer.MAX_VALUE.
 	 * 
 	 * This function does neither lock the database nor commit the transaction. You have to surround it with
-	 * synchronized(mDB.lock()) {
+	 * synchronized(Persistent.transactionLock(mDB)) {
 	 *     try { ... initTrustTreeWithoutCommit(...); mDB.commit(); }
 	 *     catch(RuntimeException e) { System.gc(); mDB.rollback(); throw e; }
 	 * }
@@ -1742,7 +1742,7 @@ else if(rank == Integer.MAX_VALUE)
 	 * This speeds up setTrust/removeTrust as the score calculation is only performed when endTrustListImport is called.
 	 * 
 	 * You MUST synchronize on this WoT around beginTrustListImport, abortTrustListImport and finishTrustListImport!
-	 * You MUST create a database transaction by synchronizing on db.lock().
+	 * You MUST create a database transaction by synchronizing on Persistent.transactionLock(db).
 	 */
 	protected void beginTrustListImport() {
 		if(mTrustListImportInProgress) {
@@ -1799,7 +1799,7 @@ protected void finishTrustListImport() {
 	 * For understanding how score calculation works you should first read {@link computeAllScores
 	 * 
 	 * This function does neither lock the database nor commit the transaction. You have to surround it with
-	 * synchronized(mDB.lock()) {
+	 * synchronized(Persistent.transactionLock(mDB)) {
 	 *     try { ... updateScoreWithoutCommit(...); mDB.commit(); }
 	 *     catch(RuntimeException e) { System.gc(); mDB.rollback(); throw e; }
 	 * }
@@ -1994,7 +1994,7 @@ public synchronized Identity addIdentity(String requestURI) throws MalformedURLE
 
 	public synchronized void deleteIdentity(Identity identity) {
 		synchronized(mPuzzleStore) {
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 			try {
 				deleteWithoutCommit(identity);
 				Persistent.checkedCommit(mDB, this);
@@ -2023,7 +2023,7 @@ public OwnIdentity createOwnIdentity(String nickName, boolean publishTrustList,
 	public synchronized OwnIdentity createOwnIdentity(String insertURI, String requestURI, String nickName,
 			boolean publishTrustList, String context) throws MalformedURLException, InvalidParameterException {
 
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 			OwnIdentity identity;
 
 			try {
@@ -2077,7 +2077,7 @@ public synchronized OwnIdentity createOwnIdentity(String insertURI, String reque
 	public synchronized void restoreIdentity(String requestURI, String insertURI) throws MalformedURLException, InvalidParameterException {
 		OwnIdentity identity;
 		synchronized(mPuzzleStore) {
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 			try {
 				FreenetURI requestFreenetURI = new FreenetURI(requestURI);
 				FreenetURI insertFreenetURI = new FreenetURI(insertURI);

src/plugins/WebOfTrust/XMLTransformer.java

@@ -354,7 +354,7 @@ public void importIdentity(FreenetURI identityURI, InputStream xmlInputStream) t
 					throw xmlData.parseError;
 
 
-				synchronized(mDB.lock()) {
+				synchronized(Persistent.transactionLock(mDB)) {
 				try { // Transaction rollback block
 					identity.setEdition(newEdition); // The identity constructor only takes the edition number as a hint, so we must store it explicitly.
 					boolean didPublishTrustListPreviously = identity.doesPublishTrustList();
@@ -464,7 +464,7 @@ public void importIdentity(FreenetURI identityURI, InputStream xmlInputStream) t
 					mWoT.abortTrustListImport(e); // Does the rollback
 					throw e;
 				} // try
-				} // synchronized(db.lock())
+				} // synchronized(Persistent.transactionLock(db))
 
 			Logger.normal(this, "Finished XML import for " + identity);
 		} // synchronized(mWoT)
@@ -568,7 +568,7 @@ public Identity importIntroduction(OwnIdentity puzzleOwner, InputStream xmlInput
 			if(!puzzleOwner.hasContext(IntroductionPuzzle.INTRODUCTION_CONTEXT))
 				throw new InvalidParameterException("Trying to import an identity identroduction for an own identity which does not allow introduction.");
 
-			synchronized(mDB.lock()) {
+			synchronized(Persistent.transactionLock(mDB)) {
 				try {
 					try {
 						newIdentity = mWoT.getIdentityByURI(identityURI);

src/plugins/WebOfTrust/introduction/IntroductionPuzzleStore.java

@@ -108,7 +108,7 @@ protected synchronized void deleteExpiredPuzzles() {
 			int deleted = 0;
 
 			for(IntroductionPuzzle p : result) {
-				synchronized(mDB.lock()) {
+				synchronized(Persistent.transactionLock(mDB)) {
 				try {
 					if(logDEBUG) Logger.debug(this, "Deleting expired puzzle, was valid until " + p.getValidUntilDate());
 					p.deleteWithoutCommit();
@@ -149,7 +149,7 @@ protected synchronized void deleteOldestUnsolvedPuzzles(final int puzzlePoolSize
 			while(deleteCount > 0 && result.hasNext()) {
 				final IntroductionPuzzle puzzle = result.next();
 
-				synchronized(mDB.lock()) {
+				synchronized(Persistent.transactionLock(mDB)) {
 				try {
 					puzzle.deleteWithoutCommit();
 					Persistent.checkedCommit(mDB, this);
@@ -193,7 +193,7 @@ public synchronized void storeAndCommit(final IntroductionPuzzle puzzle) {
 		/* TODO: Convert to assert() maybe when we are sure that this does not happen. Duplicate puzzles will be deleted after they
 		 * expire anyway. Further, isn't there a db4o option which ensures that mID is a primary key and therefore no duplicates can exist? */
 		synchronized(puzzle) {
-		synchronized(mDB.lock()) {
+		synchronized(Persistent.transactionLock(mDB)) {
 			try {
 				final IntroductionPuzzle existingPuzzle = getByID(puzzle.getID());
 				if(existingPuzzle != puzzle)