Replace SemaphoreLight with SemaphoreSlim (#1265)

This paves the way for asynchronous synchronisation via WaitAsync
(and eliminates a timing test which sometimes fails in CI)

Co-authored-by: Wojciech Nagórski <wojtpl2@gmail.com>

Author: Rob-Hague

src/Renci.SshNet/Channels/Channel.cs

@@ -285,7 +285,7 @@ protected IConnectionInfo ConnectionInfo
         /// Gets the session semaphore to control number of session channels.
         /// </summary>
         /// <value>The session semaphore.</value>
-        protected SemaphoreLight SessionSemaphore
+        protected SemaphoreSlim SessionSemaphore
         {
             get { return _session.SessionSemaphore; }
         }

src/Renci.SshNet/Common/SemaphoreLight.cs

@@ -36,7 +36,7 @@ internal interface ISession : IDisposable
         /// <value>
         /// The session semaphore.
         /// </value>
-        SemaphoreLight SessionSemaphore { get; }
+        SemaphoreSlim SessionSemaphore { get; }
 
         /// <summary>
         /// Gets a <see cref="WaitHandle"/> that can be used to wait for the message listener loop to complete.

src/Renci.SshNet/ISession.cs

@@ -87,7 +87,7 @@ public class Session : ISession
         /// <remarks>
         /// Some server may restrict number to prevent authentication attacks.
         /// </remarks>
-        private static readonly SemaphoreLight AuthenticationConnection = new SemaphoreLight(3);
+        private static readonly SemaphoreSlim AuthenticationConnection = new SemaphoreSlim(3);
 
         /// <summary>
         /// Holds the factory to use for creating new services.
@@ -196,7 +196,7 @@ public class Session : ISession
 
         private Compressor _clientCompression;
 
-        private SemaphoreLight _sessionSemaphore;
+        private SemaphoreSlim _sessionSemaphore;
 
         private bool _isDisconnectMessageSent;
 
@@ -213,15 +213,15 @@ public class Session : ISession
         /// <value>
         /// The session semaphore.
         /// </value>
-        public SemaphoreLight SessionSemaphore
+        public SemaphoreSlim SessionSemaphore
         {
             get
             {
                 if (_sessionSemaphore is null)
                 {
                     lock (_connectAndLazySemaphoreInitLock)
                     {
-                        _sessionSemaphore ??= new SemaphoreLight(ConnectionInfo.MaxSessions);
+                        _sessionSemaphore ??= new SemaphoreSlim(ConnectionInfo.MaxSessions);
                     }
                 }
 

src/Renci.SshNet/Session.cs

@@ -16,7 +16,7 @@ internal sealed class SftpFileReader : ISftpFileReader
         private readonly byte[] _handle;
         private readonly ISftpSession _sftpSession;
         private readonly uint _chunkSize;
-        private readonly SemaphoreLight _semaphore;
+        private readonly SemaphoreSlim _semaphore;
         private readonly object _readLock;
         private readonly ManualResetEvent _disposingWaitHandle;
         private readonly ManualResetEvent _readAheadCompleted;
@@ -62,7 +62,7 @@ public SftpFileReader(byte[] handle, ISftpSession sftpSession, uint chunkSize, i
             _sftpSession = sftpSession;
             _chunkSize = chunkSize;
             _fileSize = fileSize;
-            _semaphore = new SemaphoreLight(maxPendingReads);
+            _semaphore = new SemaphoreSlim(maxPendingReads);
             _queue = new Dictionary<int, BufferedRead>(maxPendingReads);
             _readLock = new object();
             _readAheadCompleted = new ManualResetEvent(initialState: false);

src/Renci.SshNet/Sftp/SftpFileReader.cs

@@ -23,7 +23,7 @@ public class ChannelSessionTest_Dispose_Disposed : ChannelSessionTestBase
         private uint _remotePacketSize;
         private uint _remoteChannelNumber;
         private TimeSpan _channelCloseTimeout;
-        private SemaphoreLight _sessionSemaphore;
+        private SemaphoreSlim _sessionSemaphore;
         private IList<ChannelEventArgs> _channelClosedRegister;
         private List<ExceptionEventArgs> _channelExceptionRegister;
 
@@ -38,7 +38,7 @@ protected override void SetupData()
             _remoteWindowSize = (uint)random.Next(0, int.MaxValue);
             _remotePacketSize = (uint)random.Next(100, 200);
             _channelCloseTimeout = TimeSpan.FromSeconds(random.Next(10, 20));
-            _sessionSemaphore = new SemaphoreLight(1);
+            _sessionSemaphore = new SemaphoreSlim(1);
             _channelClosedRegister = new List<ChannelEventArgs>();
             _channelExceptionRegister = new List<ExceptionEventArgs>();
         }

test/Renci.SshNet.Tests/Classes/Channels/ChannelSessionTest_Dispose_Disposed.cs

@@ -24,7 +24,7 @@ public class ChannelSessionTest_Dispose_SessionIsConnectedAndChannelIsOpen_Chann
         private List<ExceptionEventArgs> _channelExceptionRegister;
         private ChannelSession _channel;
         private MockSequence _sequence;
-        private SemaphoreLight _sessionSemaphore;
+        private SemaphoreSlim _sessionSemaphore;
         private int _initialSessionSemaphoreCount;
 
         protected override void SetupData()
@@ -41,7 +41,7 @@ protected override void SetupData()
             _channelClosedRegister = new List<ChannelEventArgs>();
             _channelExceptionRegister = new List<ExceptionEventArgs>();
             _initialSessionSemaphoreCount = random.Next(10, 20);
-            _sessionSemaphore = new SemaphoreLight(_initialSessionSemaphoreCount);
+            _sessionSemaphore = new SemaphoreSlim(_initialSessionSemaphoreCount);
         }
 
         protected override void SetupMocks()

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

@@ -22,7 +22,7 @@ public class ChannelSessionTest_Dispose_SessionIsConnectedAndChannelIsOpen_Chann
         private List<ExceptionEventArgs> _channelExceptionRegister;
         private ChannelSession _channel;
         private MockSequence _sequence;
-        private SemaphoreLight _sessionSemaphore;
+        private SemaphoreSlim _sessionSemaphore;
         private int _initialSessionSemaphoreCount;
 
         protected override void SetupData()
@@ -38,7 +38,7 @@ protected override void SetupData()
             _channelClosedRegister = new List<ChannelEventArgs>();
             _channelExceptionRegister = new List<ExceptionEventArgs>();
             _initialSessionSemaphoreCount = random.Next(10, 20);
-            _sessionSemaphore = new SemaphoreLight(_initialSessionSemaphoreCount);
+            _sessionSemaphore = new SemaphoreSlim(_initialSessionSemaphoreCount);
         }
 
         protected override void SetupMocks()
@@ -126,4 +126,4 @@ public void IsOpenShouldReturnFalse()
             Assert.IsFalse(_channel.IsOpen);
         }
     }
-}
+}