Last patch was a disaster... reset terrain whenever bug occurred. Trying again with some modifications on Mutex.

OpenSim/Framework/Data.MySQL/MySQLDataStore.cs

@@ -50,6 +50,7 @@ namespace OpenSim.Framework.Data.MySQL
         private const string m_landAccessListSelect = "select * from landaccesslist";
 
         private DataSet m_dataSet;
+        private static object DBAccessLock = new object(); // Trying to use a static object because there might be other regions that keep modifying table
         private MySqlDataAdapter m_primDataAdapter;
         private MySqlDataAdapter m_shapeDataAdapter;
         private MySqlDataAdapter m_itemsDataAdapter;
@@ -103,7 +104,7 @@ namespace OpenSim.Framework.Data.MySQL
 
             TestTables(m_connection);
 
-            lock (m_dataSet)
+            lock (DBAccessLock)
             {
                 m_primTable = createPrimTable();
                 m_dataSet.Tables.Add(m_primTable);
@@ -142,7 +143,7 @@ namespace OpenSim.Framework.Data.MySQL
 
         public void StoreObject(SceneObjectGroup obj, LLUUID regionUUID)
         {
-            lock (m_dataSet)
+            lock (DBAccessLock)
             {
                 foreach (SceneObjectPart prim in obj.Children.Values)
                 {
@@ -169,7 +170,7 @@ namespace OpenSim.Framework.Data.MySQL
             DataTable shapes = m_shapeTable;
 
             string selectExp = "SceneGroupID = '" + Util.ToRawUuidString(obj) + "'";
-            lock (m_dataSet)
+            lock (DBAccessLock)
             {
                 DataRow[] primRows = prims.Select(selectExp);
                 foreach (DataRow row in primRows)
@@ -225,7 +226,7 @@ namespace OpenSim.Framework.Data.MySQL
             string byRegion = "RegionUUID = '" + Util.ToRawUuidString(regionUUID) + "'";
             string orderByParent = "ParentID ASC";
 
-            lock (m_dataSet)
+            lock (DBAccessLock)
             {
                 DataRow[] primsForRegion = prims.Select(byRegion, orderByParent);
                 MainLog.Instance.Verbose("DATASTORE",
@@ -335,7 +336,7 @@ namespace OpenSim.Framework.Data.MySQL
             MainLog.Instance.Verbose("DATASTORE", "Storing terrain revision r" + revision.ToString());
 
             DataTable terrain = m_dataSet.Tables["terrain"];
-            lock (m_dataSet)
+            lock (DBAccessLock)
             {
                 MySqlCommand cmd = new MySqlCommand("insert into terrain(RegionUUID, Revision, Heightfield)" +
                                                     " values(?RegionUUID, ?Revision, ?Heightfield)", m_connection);
@@ -396,7 +397,7 @@ namespace OpenSim.Framework.Data.MySQL
 
         public void RemoveLandObject(LLUUID globalID)
         {
-            lock (m_dataSet)
+            lock (DBAccessLock)
             {
                 using (MySqlCommand cmd = new MySqlCommand("delete from land where UUID=?UUID", m_connection))
                 {
@@ -419,13 +420,7 @@ namespace OpenSim.Framework.Data.MySQL
             MainLog.Instance.Verbose("DATASTORE", "Tedds temp fix: Waiting 3 seconds for stuff to catch up. (Someone please fix! :))");
             System.Threading.Thread.Sleep(3000);
             
-            int loopCount = 0;
+            lock (DBAccessLock)
-            while (true)
-            {
-                loopCount++;
-                try
-                {
-                    lock (m_dataSet)
             {
                 DataTable land = m_landTable;
                 DataTable landaccesslist = m_landAccessListTable;
@@ -446,8 +441,7 @@ namespace OpenSim.Framework.Data.MySQL
                     MySqlCommand cmd =
                         new MySqlCommand("delete from landaccesslist where LandUUID=?LandUUID", m_connection))
                 {
-                            cmd.Parameters.Add(
+                    cmd.Parameters.Add(new MySqlParameter("?LandUUID", Util.ToRawUuidString(parcel.landData.globalID)));
-                                new MySqlParameter("?LandUUID", Util.ToRawUuidString(parcel.landData.globalID)));
                     cmd.ExecuteNonQuery();
                 }
 
@@ -457,23 +451,15 @@ namespace OpenSim.Framework.Data.MySQL
                     fillLandAccessRow(newAccessRow, entry, parcel.landData.globalID);
                     landaccesslist.Rows.Add(newAccessRow);
                 }
-                    }
+
-                    Commit();
+            Commit_NoLock();
-                    break;
-                }
-                catch (Exception ex)
-                {
-                    System.Console.WriteLine("Tedds temp fix exception, will repeat taks: " + ex.ToString());
-                    if (loopCount > 3)
-                        throw (ex);
-                }
             }
         }
 
         public List<LandData> LoadLandObjects(LLUUID regionUUID)
         {
             List<LandData> landDataForRegion = new List<LandData>();
-            lock (m_dataSet)
+            lock (DBAccessLock)
             {
                 DataTable land = m_landTable;
                 DataTable landaccesslist = m_landAccessListTable;
@@ -535,7 +521,21 @@ namespace OpenSim.Framework.Data.MySQL
                 m_connection.Open();
             }
 
-            lock (m_dataSet)
+            lock (DBAccessLock)
+            {
+                // Moved code to own sub that can be called directly by "StoreLandObject".
+                // Problem is that:
+                // - StoreLandObject locks
+                // - Some other function waits for lock
+                // - StoreLandObject releases lock
+                // - Other function obtains lock
+                // - StoreLandObject calls Commit that tries to take lock back
+                // - When StoreLandObject's Commit finally gets lock the table has been changed and we crash
+                Commit_NoLock();
+            }
+        }
+
+        private void Commit_NoLock()
         {
             // DisplayDataSet(m_dataSet, "Region DataSet");
 
@@ -553,7 +553,6 @@ namespace OpenSim.Framework.Data.MySQL
 
             m_dataSet.AcceptChanges();
         }
-        }
 
         public void Shutdown()
         {
@@ -1230,7 +1229,7 @@ namespace OpenSim.Framework.Data.MySQL
             
             // For now, we're just going to crudely remove all the previous inventory items 
             // no matter whether they have changed or not, and replace them with the current set.
-            lock (m_dataSet)
+            lock (DBAccessLock)
             {                              
                 RemoveItems(primID);