The iSCSI server will now terminate a connection only after all running SCSI commands sent using that connection have been completed

ISCSI/Server/ISCSIServer.cs

@@ -176,12 +176,7 @@ namespace ISCSI.Server
                 clientSocket.Close();
                 Log("[ReceiveCallback] The initiator has closed the connection");
                 // Wait for pending I/O to complete.
-                if (state.Target != null)
-                {
-                    lock (state.Target.IOLock)
-                    {
-                    }
-                }
+                state.RunningSCSICommands.WaitUntilZero();
                 lock (m_activeConnections)
                 {
                     int connectionIndex = GetStateObjectIndex(m_activeConnections, state.SessionParameters.ISID, state.SessionParameters.TSIH, state.ConnectionParameters.CID);
@@ -347,12 +342,7 @@ namespace ISCSI.Server
                                 Log("[{0}][ProcessPDU] Initiating implicit logout", state.ConnectionIdentifier);
                                 StateObject existingConnection = m_activeConnections[existingConnectionIndex];
                                 // Wait for pending I/O to complete.
-                                if (existingConnection.Target != null)
-                                {
-                                    lock (existingConnection.Target.IOLock)
-                                    {
-                                    }
-                                }
+                                existingConnection.RunningSCSICommands.WaitUntilZero();
                                 SocketUtils.ReleaseSocket(existingConnection.ClientSocket);
                                 m_activeConnections.RemoveAt(existingConnectionIndex);
                                 Log("[{0}][ProcessPDU] Implicit logout completed", state.ConnectionIdentifier);
@@ -414,23 +404,13 @@ namespace ISCSI.Server
                             if (existingConnection != state)
                             {
                                 // Wait for pending I/O to complete.
-                                if (existingConnection.Target != null)
-                                {
-                                    lock (existingConnection.Target.IOLock)
-                                    {
-                                    }
-                                }
+                                existingConnection.RunningSCSICommands.WaitUntilZero();
                             }
                             m_activeConnections.RemoveAt(connectionIndex);
                         }
                     }
                     // Wait for pending I/O to complete.
-                    if (state.Target != null)
-                    {
-                        lock (state.Target.IOLock)
-                        {
-                        }
-                    }
+                    state.RunningSCSICommands.WaitUntilZero();
                     LogoutRequestPDU request = (LogoutRequestPDU)pdu;
                     LogoutResponsePDU response = ServerResponseHelper.GetLogoutResponsePDU(request);
                     TrySendPDU(state, response);
@@ -475,9 +455,11 @@ namespace ISCSI.Server
                         responseList = TargetResponseHelper.GetReadyToTransferPDUs(command, state.Target, state.SessionParameters, state.ConnectionParameters, out commandsToExecute);
                     }
 
+                    state.RunningSCSICommands.Add(commandsToExecute.Count);
                     foreach(SCSICommandPDU command in commandsToExecute)
                     {
                         List<ISCSIPDU> commandResponseList = TargetResponseHelper.GetSCSICommandResponse(command, state.Target, state.SessionParameters, state.ConnectionParameters);
+                        state.RunningSCSICommands.Decrement();
                         responseList.AddRange(commandResponseList);
                     }
 

ISCSI/Server/SCSITarget.cs

@@ -17,7 +17,7 @@ namespace ISCSI.Server
     public class SCSITarget
     {
         private List<Disk> m_disks;
-        public object IOLock = new object(); // "In multithreaded applications, a stream must be accessed in a thread-safe way"
+        private object m_ioLock = new object(); // "In multithreaded applications, a stream must be accessed in a thread-safe way"
 
         public SCSITarget(List<Disk> disks)
         {
@@ -378,7 +378,7 @@ namespace ISCSI.Server
             int sectorCount = (int)command.TransferLength;
             try
             {
-                lock (IOLock)
+                lock (m_ioLock)
                 {
                     response = disk.ReadSectors((long)command.LogicalBlockAddress64, sectorCount);
                 }
@@ -504,7 +504,7 @@ namespace ISCSI.Server
 
             try
             {
-                lock (IOLock)
+                lock (m_ioLock)
                 {
                     disk.WriteSectors((long)command.LogicalBlockAddress64, data);
                 }

ISCSI/Server/StateObject.cs

@@ -8,6 +8,7 @@ using System;
 using System.Collections.Generic;
 using System.Net.Sockets;
 using System.Text;
+using Utilities;
 
 namespace ISCSI.Server
 {
@@ -28,6 +29,8 @@ namespace ISCSI.Server
         public SessionParameters SessionParameters = new SessionParameters();
         public ConnectionParameters ConnectionParameters = new ConnectionParameters();
 
+        public CountdownLatch RunningSCSICommands = new CountdownLatch();
+
         public string ConnectionIdentifier
         {
             get

Utilities/Threading/CountdownLatch.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Threading;
+
+namespace Utilities
+{
+    public class CountdownLatch
+    {
+        private int m_count;
+        private EventWaitHandle m_waitHandle = new EventWaitHandle(true, EventResetMode.ManualReset);
+
+        public CountdownLatch()
+        {
+        }
+
+        public void Increment()
+        {
+            int count = Interlocked.Increment(ref m_count);
+            if (count == 1)
+            {
+                m_waitHandle.Reset();
+            }
+        }
+
+        public void Add(int value)
+        {
+            int count = Interlocked.Add(ref m_count, value);
+            if (count == value)
+            {
+                m_waitHandle.Reset();
+            }
+        }
+
+        public void Decrement()
+        {
+            int count = Interlocked.Decrement(ref m_count);
+            if (m_count == 0)
+            {
+                m_waitHandle.Set();
+            }
+            else if (count < 0)
+            {
+                throw new InvalidOperationException("Count must be greater than or equal to 0");
+            }
+        }
+
+        public void WaitUntilZero()
+        {
+            m_waitHandle.WaitOne();
+        }
+    }
+}

Utilities/Utilities.csproj

@@ -49,6 +49,7 @@
     <Compile Include="IFileSystem\IFileSystem.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Strings\QuotedStringUtils.cs" />
+    <Compile Include="Threading\CountdownLatch.cs" />
     <Compile Include="Threading\Parallel.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />