Signal the closed wait handle to avoid a deadlock when a subscriber to the Closed event in turn closes or disposes the channel.

src/Renci.SshNet.Tests/Classes/Channels/ChannelSessionTest_Dispose_SessionIsConnectedAndChannelIsOpen_ChannelCloseAndChannelEofReceived_DisposeInEventHandler.cs

@@ -0,0 +1,136 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Moq;
+using Renci.SshNet.Channels;
+using Renci.SshNet.Common;
+using Renci.SshNet.Messages.Connection;
+using Renci.SshNet.Tests.Common;
+
+namespace Renci.SshNet.Tests.Classes.Channels
+{
+    [TestClass]
+    public class ChannelSessionTest_Dispose_SessionIsConnectedAndChannelIsOpen_ChannelCloseAndChannelEofReceived_DisposeInEventHandler
+    {
+        private Mock<ISession> _sessionMock;
+        private uint _localChannelNumber;
+        private uint _localWindowSize;
+        private uint _localPacketSize;
+        private uint _remoteChannelNumber;
+        private uint _remoteWindowSize;
+        private uint _remotePacketSize;
+        private IList<ChannelEventArgs> _channelClosedRegister;
+        private List<ExceptionEventArgs> _channelExceptionRegister;
+        private ChannelSession _channel;
+        private Mock<IConnectionInfo> _connectionInfoMock;
+        private MockSequence _sequence;
+        private SemaphoreLight _sessionSemaphore;
+        private int _initialSessionSemaphoreCount;
+
+        [TestInitialize]
+        public void Initialize()
+        {
+            Arrange();
+            Act();
+        }
+
+        private void Arrange()
+        {
+            var random = new Random();
+            _localChannelNumber = (uint)random.Next(0, int.MaxValue);
+            _localWindowSize = (uint)random.Next(0, int.MaxValue);
+            _localPacketSize = (uint)random.Next(0, int.MaxValue);
+            _remoteChannelNumber = (uint)random.Next(0, int.MaxValue);
+            _remoteWindowSize = (uint)random.Next(0, int.MaxValue);
+            _remotePacketSize = (uint)random.Next(0, int.MaxValue);
+            _channelClosedRegister = new List<ChannelEventArgs>();
+            _channelExceptionRegister = new List<ExceptionEventArgs>();
+            _initialSessionSemaphoreCount = random.Next(10, 20);
+            _sessionSemaphore = new SemaphoreLight(_initialSessionSemaphoreCount);
+
+            _sessionMock = new Mock<ISession>(MockBehavior.Strict);
+            _connectionInfoMock = new Mock<IConnectionInfo>(MockBehavior.Strict);
+
+            _sequence = new MockSequence();
+            _sessionMock.InSequence(_sequence).Setup(p => p.ConnectionInfo).Returns(_connectionInfoMock.Object);
+            _connectionInfoMock.InSequence(_sequence).Setup(p => p.RetryAttempts).Returns(1);
+            _sessionMock.Setup(p => p.SessionSemaphore).Returns(_sessionSemaphore);
+            _sessionMock.InSequence(_sequence)
+                        .Setup(
+                            p =>
+                                p.SendMessage(
+                                    It.Is<ChannelOpenMessage>(
+                                        m =>
+                                            m.LocalChannelNumber == _localChannelNumber &&
+                                            m.InitialWindowSize == _localWindowSize && m.MaximumPacketSize == _localPacketSize &&
+                                            m.Info is SessionChannelOpenInfo)));
+            _sessionMock.InSequence(_sequence)
+                        .Setup(p => p.WaitOnHandle(It.IsNotNull<WaitHandle>()))
+                        .Callback<WaitHandle>(
+                            w =>
+                            {
+                                _sessionMock.Raise(
+                                    s => s.ChannelOpenConfirmationReceived += null,
+                                    new MessageEventArgs<ChannelOpenConfirmationMessage>(
+                                        new ChannelOpenConfirmationMessage(
+                                            _localChannelNumber,
+                                            _remoteWindowSize,
+                                            _remotePacketSize,
+                                            _remoteChannelNumber)));
+                                w.WaitOne();
+                            });
+            _sessionMock.InSequence(_sequence).Setup(p => p.IsConnected).Returns(true);
+            _sessionMock.InSequence(_sequence)
+                        .Setup(p => p.TrySendMessage(It.Is<ChannelCloseMessage>(c => c.LocalChannelNumber == _remoteChannelNumber)))
+                        .Returns(true);
+            _sessionMock.InSequence(_sequence)
+                        .Setup(s => s.WaitOnHandle(It.IsNotNull<EventWaitHandle>()))
+                        .Callback<WaitHandle>(w => w.WaitOne());
+
+            _channel = new ChannelSession(_sessionMock.Object, _localChannelNumber, _localWindowSize, _localPacketSize);
+            _channel.Closed += (sender, args) =>
+                {
+                    _channelClosedRegister.Add(args);
+                    _channel.Dispose();
+                };
+            _channel.Exception += (sender, args) => _channelExceptionRegister.Add(args);
+            _channel.Open();
+
+            _sessionMock.Raise(p => p.ChannelEofReceived += null,
+                               new MessageEventArgs<ChannelEofMessage>(new ChannelEofMessage(_localChannelNumber)));
+            _sessionMock.Raise(p => p.ChannelCloseReceived += null,
+                               new MessageEventArgs<ChannelCloseMessage>(new ChannelCloseMessage(_localChannelNumber)));
+        }
+
+        private void Act()
+        {
+            _channel.Dispose();
+        }
+
+        [TestMethod]
+        public void CurrentCountOfSessionSemaphoreShouldBeEqualToInitialCount()
+        {
+            Assert.AreEqual(_initialSessionSemaphoreCount, _sessionSemaphore.CurrentCount);
+        }
+
+        [TestMethod]
+        public void ExceptionShouldNeverHaveFired()
+        {
+            Assert.AreEqual(0, _channelExceptionRegister.Count, _channelExceptionRegister.AsString());
+        }
+
+        [TestMethod]
+        public void ClosedEventShouldHaveFiredOnce()
+        {
+            Assert.AreEqual(1, _channelClosedRegister.Count);
+            Assert.AreEqual(_localChannelNumber, _channelClosedRegister[0].ChannelNumber);
+        }
+
+        [TestMethod]
+        public void IsOpenShouldReturnFalse()
+        {
+            Assert.IsFalse(_channel.IsOpen);
+        }
+    }
+}

src/Renci.SshNet.Tests/Renci.SshNet.Tests.csproj

@@ -94,6 +94,7 @@
     <Compile Include="Classes\Channels\ChannelSessionTest_Dispose_Disposed.cs" />
     <Compile Include="Classes\Channels\ChannelSessionTest_Dispose_SessionIsConnectedAndChannelIsOpen_ChannelCloseAndChannelEofReceived_SendChannelCloseMessageFailure.cs" />
     <Compile Include="Classes\Channels\ChannelSessionTest_Dispose_SessionIsConnectedAndChannelIsOpen_ChannelCloseAndChannelEofReceived_SendChannelCloseMessageSuccess.cs" />
+    <Compile Include="Classes\Channels\ChannelSessionTest_Dispose_SessionIsConnectedAndChannelIsOpen_ChannelCloseAndChannelEofReceived_DisposeInEventHandler.cs" />
     <Compile Include="Classes\Channels\ChannelSessionTest_Dispose_SessionIsConnectedAndChannelIsOpen_ChannelCloseReceived_SendChannelCloseMessageFailure.cs" />
     <Compile Include="Classes\Channels\ChannelSessionTest_Dispose_SessionIsConnectedAndChannelIsOpen_ChannelCloseReceived_SendChannelCloseMessageSuccess.cs" />
     <Compile Include="Classes\Channels\ChannelSessionTest_Dispose_SessionIsConnectedAndChannelIsOpen_ChannelEofReceived_SendChannelCloseMessageFailure.cs" />

src/Renci.SshNet/Channels/Channel.cs

@@ -400,6 +400,14 @@ namespace Renci.SshNet.Channels
         {
             _closeMessageReceived = true;
 
+            // signal that SSH_MSG_CHANNEL_CLOSE message was received from server
+            // we need to signal this before firing the Closed event, as a subscriber
+            // may very well react to the Closed event by closing or disposing the
+            // channel which in turn will wait for this handle to be signaled
+            var channelClosedWaitHandle = _channelClosedWaitHandle;
+            if (channelClosedWaitHandle != null)
+                channelClosedWaitHandle.Set();
+
             // raise event signaling that the server has closed its end of the channel
             var closed = Closed;
             if (closed != null)
@@ -407,11 +415,6 @@ namespace Renci.SshNet.Channels
                 closed(this, new ChannelEventArgs(LocalChannelNumber));
             }
 
-            // signal that SSH_MSG_CHANNEL_CLOSE message was received from server
-            var channelClosedWaitHandle = _channelClosedWaitHandle;
-            if (channelClosedWaitHandle != null)
-                channelClosedWaitHandle.Set();
-
             // close the channel
             Close();
         }