Remove long running option from MARS (#28627)

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNIHandle.cs

@@ -56,7 +56,7 @@ internal abstract class SNIHandle
         /// </summary>
         /// <param name="packet">SNI packet</param>
         /// <returns>SNI error code</returns>
-        public abstract uint ReceiveAsync(ref SNIPacket packet, bool isMars = false);
+        public abstract uint ReceiveAsync(ref SNIPacket packet);
 
         /// <summary>
         /// Enable SSL

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNIMarsConnection.cs

@@ -108,7 +108,7 @@ public uint ReceiveAsync(ref SNIPacket packet)
         {
             lock (this)
             {
-                return _lowerHandle.ReceiveAsync(ref packet, isMars: true);
+                return _lowerHandle.ReceiveAsync(ref packet);
             }
         }
 

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNIMarsHandle.cs

@@ -272,7 +272,7 @@ public override uint SendAsync(SNIPacket packet, bool disposePacketAfterSendAsyn
         /// </summary>
         /// <param name="packet">SNI packet</param>
         /// <returns>SNI error code</returns>
-        public override uint ReceiveAsync(ref SNIPacket packet, bool isMars = true)
+        public override uint ReceiveAsync(ref SNIPacket packet)
         {
             lock (_receivedPacketQueue)
             {

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNINpHandle.cs

@@ -172,13 +172,13 @@ public override uint Receive(out SNIPacket packet, int timeout)
             }
         }
 
-        public override uint ReceiveAsync(ref SNIPacket packet, bool isMars = false)
+        public override uint ReceiveAsync(ref SNIPacket packet)
         {
             packet = new SNIPacket(_bufferSize);
 
             try
             {
-                packet.ReadFromStreamAsync(_stream, _receiveCallback, isMars);
+                packet.ReadFromStreamAsync(_stream, _receiveCallback);
                 return TdsEnums.SNI_SUCCESS_IO_PENDING;
             }
             catch (ObjectDisposedException ode)

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNIPacket.cs

@@ -245,22 +245,13 @@ public void Reset()
         /// </summary>
         /// <param name="stream">Stream to read from</param>
         /// <param name="callback">Completion callback</param>
-        public void ReadFromStreamAsync(Stream stream, SNIAsyncCallback callback, bool isMars)
+        public void ReadFromStreamAsync(Stream stream, SNIAsyncCallback callback)
         {
             bool error = false;
-            TaskContinuationOptions options = TaskContinuationOptions.DenyChildAttach;
-            // MARS operations during Sync ADO.Net API calls are Sync over Async. Each API call can request 
-            // threads to execute the async reads. MARS operations do not get the threads quickly enough leading to timeout
-            // To fix the MARS thread exhaustion issue LongRunning continuation option is a temporary solution with its own drawbacks, 
-            // and should be removed after evaluating how to fix MARS threading issues efficiently
-            if (isMars)
-            {
-                options |= TaskContinuationOptions.LongRunning;
-            }
-
+
             stream.ReadAsync(_data, 0, _capacity, CancellationToken.None).ContinueWith(t =>
             {
-                Exception e = t.Exception != null ? t.Exception.InnerException : null;
+                Exception e = t.Exception?.InnerException;
                 if (e != null)
                 {
                     SNILoadHandle.SingletonInstance.LastError = new SNIError(SNIProviders.TCP_PROV, SNICommon.InternalExceptionError, e);
@@ -285,7 +276,7 @@ public void ReadFromStreamAsync(Stream stream, SNIAsyncCallback callback, bool i
                 callback(this, error ? TdsEnums.SNI_ERROR : TdsEnums.SNI_SUCCESS);
             },
             CancellationToken.None,
-            options,
+            TaskContinuationOptions.DenyChildAttach,
             TaskScheduler.Default);
         }
 

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNIProxy.cs

@@ -443,7 +443,7 @@ private SNINpHandle CreateNpHandle(DataSource details, long timerExpire, object
         /// <param name="handle">SNI handle</param>
         /// <param name="packet">Packet</param>
         /// <returns>SNI error status</returns>
-        public uint ReadAsync(SNIHandle handle, out SNIPacket packet, bool isMars = false)
+        public uint ReadAsync(SNIHandle handle, out SNIPacket packet)
         {
             packet = null;
             return handle.ReceiveAsync(ref packet);

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNITcpHandle.cs

@@ -537,13 +537,13 @@ public override uint SendAsync(SNIPacket packet, bool disposePacketAfterSendAsyn
         /// </summary>
         /// <param name="packet">SNI packet</param>
         /// <returns>SNI error code</returns>
-        public override uint ReceiveAsync(ref SNIPacket packet, bool isMars = false)
+        public override uint ReceiveAsync(ref SNIPacket packet)
         {
             packet = new SNIPacket(_bufferSize);
 
             try
             {
-                packet.ReadFromStreamAsync(_stream, _receiveCallback, isMars);
+                packet.ReadFromStreamAsync(_stream, _receiveCallback);
                 return TdsEnums.SNI_SUCCESS_IO_PENDING;
             }
             catch (Exception e) when (e is ObjectDisposedException || e is SocketException || e is IOException)

src/System.Data.SqlClient/src/System/Data/SqlClient/TdsParserStateObjectManaged.cs

@@ -156,7 +156,7 @@ internal override uint CheckConnection()
         internal override object ReadAsync(out uint error, ref object handle)
         {
             SNIPacket packet;
-            error = SNIProxy.Singleton.ReadAsync((SNIHandle)handle, out packet, isMars: _parser.MARSOn);
+            error = SNIProxy.Singleton.ReadAsync((SNIHandle)handle, out packet);
             return packet;
         }