Updated SocketConnection internal locking to fix potential deadlock

CryptoExchange.Net/Sockets/Default/SocketConnection.cs

@@ -8,7 +8,9 @@ using CryptoExchange.Net.Sockets.Default.Interfaces;
 using CryptoExchange.Net.Sockets.Interfaces;
 using Microsoft.Extensions.Logging;
 using System;
+using System.Collections;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Diagnostics;
 using System.Linq;
 using System.Net.WebSockets;
@@ -122,17 +124,9 @@ namespace CryptoExchange.Net.Sockets.Default
         public int UserSubscriptionCount
         {
             get
-            {
-                _listenersLock.EnterReadLock();
-                try
             {
                 return _listeners.OfType<Subscription>().Count(h => h.UserSubscription);
             }
-                finally
-                {
-                    _listenersLock.ExitReadLock();
-                }
-            }
         }
 
         /// <summary>
@@ -141,17 +135,8 @@ namespace CryptoExchange.Net.Sockets.Default
         public Subscription[] Subscriptions
         {
             get
-            {
-                _listenersLock.EnterReadLock();
-                try
             {
                 return _listeners.OfType<Subscription>().Where(h => h.UserSubscription).ToArray();
-
-                }
-                finally
-                {
-                    _listenersLock.ExitReadLock();
-                }
             }
         }
 
@@ -254,17 +239,9 @@ namespace CryptoExchange.Net.Sockets.Default
         public string[] Topics
         {
             get
-            {
-                _listenersLock.EnterReadLock();
-                try
             {
                 return _listeners.OfType<Subscription>().Select(x => x.Topic).Where(t => t != null).ToArray()!;
             }
-                finally
-                {
-                    _listenersLock.ExitReadLock();
-                }
-            }
         }
 
         /// <summary>
@@ -273,23 +250,19 @@ namespace CryptoExchange.Net.Sockets.Default
         public int PendingRequests
         {
             get
-            {
-                _listenersLock.EnterReadLock();
-                try
             {
                 return _listeners.OfType<Query>().Where(x => !x.Completed).Count();
             }
-                finally
-                {
-                    _listenersLock.ExitReadLock();
-                }
-            }
         }
 
 
         private bool _pausedActivity;
-        private readonly ReaderWriterLockSlim _listenersLock = new ReaderWriterLockSlim();
+#if NET9_0_OR_GREATER
-        private readonly List<IMessageProcessor> _listeners;
+        private readonly Lock _listenersLock = new Lock();
+#else
+        private readonly object _listenersLock = new object();
+#endif
+        private ReadOnlyCollection<IMessageProcessor> _listeners;
         private readonly ILogger _logger;
         private SocketStatus _status;
 
@@ -338,7 +311,7 @@ namespace CryptoExchange.Net.Sockets.Default
             _socket.OnError += HandleErrorAsync;
             _socket.GetReconnectionUrl = GetReconnectionUrlAsync;
 
-            _listeners = new List<IMessageProcessor>();
+            _listeners = new ReadOnlyCollection<IMessageProcessor>([]);
 
             _serializer = apiClient.CreateSerializer();
         }
@@ -365,25 +338,17 @@ namespace CryptoExchange.Net.Sockets.Default
             if (ApiClient._socketConnections.ContainsKey(SocketId))
                 ApiClient._socketConnections.TryRemove(SocketId, out _);
 
-            _listenersLock.EnterWriteLock();
-            try
-            {
             foreach (var subscription in _listeners.OfType<Subscription>().Where(l => l.UserSubscription && !l.IsClosingConnection))
             {
                 subscription.IsClosingConnection = true;
                 subscription.Reset();
             }
 
-                foreach (var query in _listeners.OfType<Query>().ToList())
+            var queryList = _listeners.OfType<Query>().ToList();
-                {
+            foreach (var query in queryList)            
                 query.Fail(new WebError("Connection interrupted"));            
-                    _listeners.Remove(query);
+
-                }
+            RemoveMessageProcessors(queryList);
-            }
-            finally
-            {
-                _listenersLock.ExitWriteLock();
-            }
 
             _ = Task.Run(() => ConnectionClosed?.Invoke());
             return Task.CompletedTask;
@@ -399,22 +364,14 @@ namespace CryptoExchange.Net.Sockets.Default
             Authenticated = false;
             _lastSequenceNumber = 0;
 
-            _listenersLock.EnterWriteLock();
-            try
-            {
             foreach (var subscription in _listeners.OfType<Subscription>().Where(l => l.UserSubscription))
                 subscription.Reset();
 
-                foreach (var query in _listeners.OfType<Query>().ToList())
+            var queryList = _listeners.OfType<Query>().ToList();
-                {
+            foreach (var query in queryList)
                 query.Fail(new WebError("Connection interrupted"));
-                    _listeners.Remove(query);
+
-                }
+            RemoveMessageProcessors(queryList);
-            }
-            finally
-            {
-                _listenersLock.ExitWriteLock();
-            }
 
             _ = Task.Run(() => ConnectionLost?.Invoke());
             return Task.CompletedTask;
@@ -436,19 +393,11 @@ namespace CryptoExchange.Net.Sockets.Default
         {
             Status = SocketStatus.Resubscribing;
 
-            _listenersLock.EnterWriteLock();
+            var queryList = _listeners.OfType<Query>().ToList();
-            try
+            foreach (var query in queryList)            
-            {
-                foreach (var query in _listeners.OfType<Query>().ToList())
-                {
                 query.Fail(new WebError("Connection interrupted"));
-                    _listeners.Remove(query);
+            
-                }
+            RemoveMessageProcessors(queryList);
-            }
-            finally
-            {
-                _listenersLock.ExitWriteLock();
-            }
 
             // Can't wait for this as it would cause a deadlock
             _ = Task.Run(async () =>
@@ -503,17 +452,7 @@ namespace CryptoExchange.Net.Sockets.Default
         /// <returns></returns>
         protected virtual Task HandleRequestRateLimitedAsync(int requestId)
         {
-            Query? query;
+            var query = _listeners.OfType<Query>().FirstOrDefault(x => x.Id == requestId);
-            _listenersLock.EnterReadLock();
-            try
-            {
-                query = _listeners.OfType<Query>().FirstOrDefault(x => x.Id == requestId);
-            }
-            finally
-            {
-                _listenersLock.ExitReadLock();
-            }
-
             if (query == null)
                 return Task.CompletedTask;
 
@@ -537,17 +476,7 @@ namespace CryptoExchange.Net.Sockets.Default
         /// <param name="requestId">Id of the request sent</param>
         protected virtual Task HandleRequestSentAsync(int requestId)
         {
-            Query? query;
+            var query = _listeners.OfType<Query>().FirstOrDefault(x => x.Id == requestId);
-            _listenersLock.EnterReadLock();
-            try
-            {
-                query = _listeners.OfType<Query>().FirstOrDefault(x => x.Id == requestId);
-            }
-            finally
-            {
-                _listenersLock.ExitReadLock();
-            }
-
             if (query == null)
                 return Task.CompletedTask;
 
@@ -593,9 +522,6 @@ namespace CryptoExchange.Net.Sockets.Default
             }
 
             Type? deserializationType = null;
-            _listenersLock.EnterReadLock();
-            try
-            {
             foreach (var subscription in _listeners)
             {
                 foreach (var route in subscription.MessageRouter.Routes)
@@ -610,11 +536,6 @@ namespace CryptoExchange.Net.Sockets.Default
                 if (deserializationType != null)
                     break;
             }
-            }
-            finally
-            {
-                _listenersLock.ExitReadLock();
-            }
 
             if (deserializationType == null)
             {
@@ -660,20 +581,8 @@ namespace CryptoExchange.Net.Sockets.Default
             var topicFilter = messageConverter.GetTopicFilter(result);
 
             bool processed = false;
-            _listenersLock.EnterReadLock();
+            foreach (var processor in _listeners)
-            try
             {
-                var currentCount = _listeners.Count;
-                for(var i = 0; i < _listeners.Count; i++)
-                {
-                    if (_listeners.Count != currentCount)
-                    {
-                        // Possible a query added or removed. If added it's not a problem, if removed it is
-                        if (_listeners.Count < currentCount)
-                            throw new Exception("Listeners list adjusted, can't continue processing");                            
-                    }
-
-                    var processor = _listeners[i];
                 bool isQuery = false;
                 Query? query = null;
                 if (processor is Query cquery)
@@ -725,18 +634,10 @@ namespace CryptoExchange.Net.Sockets.Default
                 if (complete)
                     break;
             }
-            }
-            finally
-            {
-                _listenersLock.ExitReadLock();
-            }
 
             if (!processed)
             {
                 if (!ApiClient.HandleUnhandledMessage(this, typeIdentifier, data))
-                {
-                    _listenersLock.EnterReadLock();
-                    try
                 {
                     _logger.ReceivedMessageNotMatchedToAnyListener(
                         SocketId,
@@ -744,11 +645,6 @@ namespace CryptoExchange.Net.Sockets.Default
                         topicFilter!,
                         string.Join(",", _listeners.Select(x => string.Join(",", x.MessageRouter.Routes.Where(x => x.TypeIdentifier == typeIdentifier).Select(x => x.TopicFilter != null ? string.Join(",", x.TopicFilter) : "[null]")))));
                 }
-                    finally
-                    {
-                        _listenersLock.ExitReadLock();
-                    }
-                }
             }
         }
 
@@ -792,19 +688,11 @@ namespace CryptoExchange.Net.Sockets.Default
             if (ApiClient._socketConnections.ContainsKey(SocketId))
                 ApiClient._socketConnections.TryRemove(SocketId, out _);
 
-            _listenersLock.EnterReadLock();
-            try
-            {
             foreach (var subscription in _listeners.OfType<Subscription>())
             {
                 if (subscription.CancellationTokenRegistration.HasValue)
                     subscription.CancellationTokenRegistration.Value.Dispose();
             }
-            }
-            finally
-            {
-                _listenersLock.ExitReadLock();
-            }
 
             await _socket.CloseAsync().ConfigureAwait(false);
             _socket.Dispose();
@@ -833,32 +721,12 @@ namespace CryptoExchange.Net.Sockets.Default
             if (subscription.CancellationTokenRegistration.HasValue)
                 subscription.CancellationTokenRegistration.Value.Dispose();
 
-            bool anyDuplicateSubscription;
+            bool anyDuplicateSubscription = _listeners.OfType<Subscription>().Any(x => x != subscription && x.MessageRouter.Routes.All(l => subscription.MessageRouter.ContainsCheck(l)));
-            bool shouldCloseConnection;
+            bool shouldCloseConnection = _listeners.OfType<Subscription>().All(r => !r.UserSubscription || r.Status == SubscriptionStatus.Closing || r.Status == SubscriptionStatus.Closed) && !DedicatedRequestConnection.IsDedicatedRequestConnection;
-            _listenersLock.EnterReadLock();
-            try
-            {
-                anyDuplicateSubscription = _listeners.OfType<Subscription>().Any(x => x != subscription && x.MessageRouter.Routes.All(l => subscription.MessageRouter.ContainsCheck(l)));
-                shouldCloseConnection = _listeners.OfType<Subscription>().All(r => !r.UserSubscription || r.Status == SubscriptionStatus.Closing || r.Status == SubscriptionStatus.Closed) && !DedicatedRequestConnection.IsDedicatedRequestConnection;
-            }
-            finally
-            {
-                _listenersLock.ExitReadLock();
-            }                
 
             if (!anyDuplicateSubscription)
             {
-                bool needUnsub;
+                var needUnsub = _listeners.Contains(subscription) && !shouldCloseConnection;
-                _listenersLock.EnterReadLock();
-                try
-                {
-                    needUnsub = _listeners.Contains(subscription) && !shouldCloseConnection;
-                }
-                finally
-                {
-                    _listenersLock.ExitReadLock();
-                }
-
                 if (needUnsub && _socket.IsOpen)
                     await UnsubscribeAsync(subscription).ConfigureAwait(false);
             }
@@ -882,15 +750,7 @@ namespace CryptoExchange.Net.Sockets.Default
                 await CloseAsync().ConfigureAwait(false);
             }
 
-            _listenersLock.EnterWriteLock();
+            RemoveMessageProcessor(subscription);
-            try
-            {
-                _listeners.Remove(subscription);
-            }
-            finally
-            {
-                _listenersLock.ExitWriteLock();
-            }
 
             subscription.Status = SubscriptionStatus.Closed;
         }
@@ -914,15 +774,7 @@ namespace CryptoExchange.Net.Sockets.Default
             if (Status != SocketStatus.None && Status != SocketStatus.Connected)
                 return false;
 
-            _listenersLock.EnterWriteLock();
+            AddMessageProcessor(subscription);
-            try
-            {
-                _listeners.Add(subscription);
-            }
-            finally
-            {
-                _listenersLock.ExitWriteLock();
-            }
 
             if (subscription.UserSubscription)
                 _logger.AddingNewSubscription(SocketId, subscription.Id, UserSubscriptionCount);
@@ -934,17 +786,9 @@ namespace CryptoExchange.Net.Sockets.Default
         /// </summary>
         /// <param name="id"></param>
         public Subscription? GetSubscription(int id)
-        {
-            _listenersLock.EnterReadLock();
-            try
         {
             return _listeners.OfType<Subscription>().SingleOrDefault(s => s.Id == id);
         }
-            finally
-            {
-                _listenersLock.ExitReadLock();
-            }
-        }
 
         /// <summary>
         /// Get the state of the connection
@@ -991,29 +835,12 @@ namespace CryptoExchange.Net.Sockets.Default
 
         private async Task SendAndWaitIntAsync(Query query, CancellationToken ct = default)
         {
-            _listenersLock.EnterWriteLock();
+            AddMessageProcessor(query);
-            try
-            {
-                _listeners.Add(query);
-            }
-            finally
-            {
-                _listenersLock.ExitWriteLock();
-            }
-
             var sendResult = await SendAsync(query.Id, query.Request, query.Weight).ConfigureAwait(false);
             if (!sendResult)
             {
                 query.Fail(sendResult.Error!);
-                _listenersLock.EnterWriteLock();
+                RemoveMessageProcessor(query);
-                try
-                {
-                    _listeners.Remove(query);
-                }
-                finally
-                {
-                    _listenersLock.ExitWriteLock();
-                }
                 return;
             }
 
@@ -1044,15 +871,7 @@ namespace CryptoExchange.Net.Sockets.Default
             }
             finally
             {
-                _listenersLock.EnterWriteLock();
+                RemoveMessageProcessor(query);
-                try
-                {
-                    _listeners.Remove(query);
-                }
-                finally
-                {
-                    _listenersLock.ExitWriteLock();
-                }
             }
         }
 
@@ -1158,17 +977,7 @@ namespace CryptoExchange.Net.Sockets.Default
 
             if (!DedicatedRequestConnection.IsDedicatedRequestConnection)
             {
-                bool anySubscriptions;
+                var anySubscriptions = _listeners.OfType<Subscription>().Any(s => s.UserSubscription);
-                _listenersLock.EnterReadLock();
-                try
-                {
-                    anySubscriptions = _listeners.OfType<Subscription>().Any(s => s.UserSubscription);
-                }
-                finally
-                {
-                    _listenersLock.ExitReadLock();
-                }
-
                 if (!anySubscriptions)
                 {
                     // No need to resubscribe anything
@@ -1178,18 +987,8 @@ namespace CryptoExchange.Net.Sockets.Default
                 }
             }
 
-            bool anyAuthenticated;
+            bool anyAuthenticated = _listeners.OfType<Subscription>().Any(s => s.Authenticated)
-            _listenersLock.EnterReadLock();
-            try
-            {
-                anyAuthenticated = _listeners.OfType<Subscription>().Any(s => s.Authenticated)
                     || DedicatedRequestConnection.IsDedicatedRequestConnection && DedicatedRequestConnection.Authenticated;
-            }
-            finally
-            {
-                _listenersLock.ExitReadLock();
-            }
-
             if (anyAuthenticated)
             {
                 // If we reconnected a authenticated connection we need to re-authenticate
@@ -1212,17 +1011,7 @@ namespace CryptoExchange.Net.Sockets.Default
                 if (!_socket.IsOpen)
                     return new CallResult(new WebError("Socket not connected"));
 
-                List<Subscription> subList;
+                var subList = _listeners.OfType<Subscription>().Where(x => x.Active).Skip(batch * batchSize).Take(batchSize).ToList();
-                _listenersLock.EnterReadLock();
-                try
-                {
-                    subList = _listeners.OfType<Subscription>().Where(x => x.Active).Skip(batch * batchSize).Take(batchSize).ToList();
-                }
-                finally
-                {
-                    _listenersLock.ExitReadLock();
-                }
-
                 if (subList.Count == 0)
                     break;
 
@@ -1404,6 +1193,37 @@ namespace CryptoExchange.Net.Sockets.Default
             });
         }
 
+        private void AddMessageProcessor(IMessageProcessor processor)
+        {
+            lock (_listenersLock)
+            {
+                var updatedList = new List<IMessageProcessor>(_listeners);
+                updatedList.Add(processor);
+                _listeners = updatedList.AsReadOnly();
+            }
+        }
+
+        private void RemoveMessageProcessor(IMessageProcessor processor)
+        {
+            lock (_listenersLock)
+            {
+                var updatedList = new List<IMessageProcessor>(_listeners);
+                updatedList.Remove(processor);
+                _listeners = updatedList.AsReadOnly();
+            }
+        }
+
+        private void RemoveMessageProcessors(IEnumerable<IMessageProcessor> processors)
+        {
+            lock (_listenersLock)
+            {
+                var updatedList = new List<IMessageProcessor>(_listeners);
+                foreach (var processor in processors)
+                    updatedList.Remove(processor);
+                _listeners = updatedList.AsReadOnly();
+            }
+        }
+
     }
 }