Tweak locks to hopefully avoid deadlocks a bit

1 files changed, 52 insertions, 37 deletions

diff --git a/src/main/java/com/c2kernel/persistency/TransactionManager.java b/src/main/java/com/c2kernel/persistency/TransactionManager.java
index 86e8199..d966eec 100644
--- a/src/main/java/com/c2kernel/persistency/TransactionManager.java
+++ b/src/main/java/com/c2kernel/persistency/TransactionManager.java
@@ -63,16 +63,14 @@ public class TransactionManager {
 

         Integer sysKeyIntObj = new Integer(sysKey);

         // check to see if the locker has been modifying this cluster

-        synchronized(locks) {

-            if (locks.containsKey(sysKeyIntObj) && locks.get(sysKeyIntObj).equals(locker)) {

-                ArrayList<TransactionEntry> lockerTransaction = pendingTransactions.get(locker);

-                for (TransactionEntry thisEntry : lockerTransaction) {

-                    if (sysKey == thisEntry.sysKey.intValue() && path.equals(thisEntry.getPath())) {

-                        if (thisEntry.obj == null)

-                            throw new ClusterStorageException("ClusterStorageManager.get() - Cluster " + path + " has been deleted in " + sysKey +

-                                " but not yet committed");

-                        return thisEntry.obj;

-                    }

+        if (locks.containsKey(sysKeyIntObj) && locks.get(sysKeyIntObj).equals(locker)) {

+            ArrayList<TransactionEntry> lockerTransaction = pendingTransactions.get(locker);

+            for (TransactionEntry thisEntry : lockerTransaction) {

+                if (sysKey == thisEntry.sysKey.intValue() && path.equals(thisEntry.getPath())) {

+                    if (thisEntry.obj == null)

+                        throw new ClusterStorageException("ClusterStorageManager.get() - Cluster " + path + " has been deleted in " + sysKey +

+                            " but not yet committed");

+                    return thisEntry.obj;

                 }

             }

         }

@@ -85,6 +83,7 @@ public class TransactionManager {
      */

     public void put(int sysKey, C2KLocalObject obj, Object locker) throws ClusterStorageException {

         Integer sysKeyIntObj = new Integer(sysKey);

+        Object tempLocker = null;

         ArrayList<TransactionEntry> lockerTransaction;

         String path = ClusterStorage.getPath(obj);

 

@@ -99,28 +98,35 @@ public class TransactionManager {
                         throw new ClusterStorageException("ClusterStorageManager.get() - Access denied: Object " + sysKeyIntObj +

                         " has been locked for writing by " + thisLocker);

             }

-            else { // either we are the locker, or there is no locker

-                if (locker == null) { // non-locking put/delete

-                    storage.put(sysKeyIntObj, obj);

-                    return;

+            else { // no locks for this item

+                if (locker == null) { // lock the item until the non-transactional put is complete :/

+                	tempLocker = new Object();

+                	locks.put(sysKeyIntObj, tempLocker);

+                	lockerTransaction = null;

                 }

-                else {// initialise the transaction

+                else { // initialise the transaction

                     locks.put(sysKeyIntObj, locker);

                     lockerTransaction = new ArrayList<TransactionEntry>();

                     pendingTransactions.put(locker, lockerTransaction);

                 }

             }

-

-            // create the new entry in the transaction table

-            TransactionEntry newEntry = new TransactionEntry(sysKeyIntObj, path, obj);

-            /* equals() in TransactionEntry only compares sysKey and path, so we can use

-             * contains() in ArrayList to looks for preexisting entries for this cluster

-             * and overwrite them.

-             */

-            if (lockerTransaction.contains(newEntry))

-                lockerTransaction.remove(newEntry);

-            lockerTransaction.add(newEntry);

         }

+        

+        if (tempLocker != null) { // non-locking put/delete

+            storage.put(sysKeyIntObj, obj);

+            locks.remove(sysKeyIntObj);

+            return;

+        }

+

+        // create the new entry in the transaction table

+        TransactionEntry newEntry = new TransactionEntry(sysKeyIntObj, path, obj);

+        /* equals() in TransactionEntry only compares sysKey and path, so we can use

+         * contains() in ArrayList to looks for preexisting entries for this cluster

+         * and overwrite them.

+         */

+        if (lockerTransaction.contains(newEntry))

+            lockerTransaction.remove(newEntry);

+        lockerTransaction.add(newEntry);

     }

 

     /** Public delete method. Uses the put method, with null as the object value.

@@ -128,6 +134,7 @@ public class TransactionManager {
     public void remove(int sysKey, String path, Object locker) throws ClusterStorageException {

 		Integer sysKeyIntObj = new Integer(sysKey);

 		ArrayList<TransactionEntry> lockerTransaction;

+		Object tempLocker = null;

 		synchronized(locks) {

 			// look to see if this object is already locked

 			if (locks.containsKey(sysKeyIntObj)) {

@@ -141,8 +148,9 @@ public class TransactionManager {
 			}

 			else { // either we are the locker, or there is no locker

 				if (locker == null) { // non-locking put/delete

-						storage.remove(sysKeyIntObj, path);

-						return;

+                	tempLocker = new Object();

+                	locks.put(sysKeyIntObj, tempLocker);

+                	lockerTransaction = null;

 				}

 				else {// initialise the transaction

 					locks.put(sysKeyIntObj, locker);

@@ -150,17 +158,24 @@ public class TransactionManager {
 					pendingTransactions.put(locker, lockerTransaction);

 				}

 			}

-

-			// create the new entry in the transaction table

-			TransactionEntry newEntry = new TransactionEntry(sysKeyIntObj, path, null);

-			/* equals() in TransactionEntry only compares sysKey and path, so we can use

-			 * contains() in ArrayList to looks for preexisting entries for this cluster

-			 * and overwrite them.

-			 */

-			if (lockerTransaction.contains(newEntry))

-				lockerTransaction.remove(newEntry);

-			lockerTransaction.add(newEntry);

 		}

+		

+		if (tempLocker != null) {

+			storage.remove(sysKeyIntObj, path);

+			locks.remove(sysKeyIntObj);

+			return;

+    	}

+		

+		// create the new entry in the transaction table

+		TransactionEntry newEntry = new TransactionEntry(sysKeyIntObj, path, null);

+		/* equals() in TransactionEntry only compares sysKey and path, so we can use

+		 * contains() in ArrayList to looks for preexisting entries for this cluster

+		 * and overwrite them.

+		 */

+		if (lockerTransaction.contains(newEntry))

+			lockerTransaction.remove(newEntry);

+		lockerTransaction.add(newEntry);

+		

     }

 

     /**