Don't capture AsyncLocals into SQL global timers

src/Common/src/System/Data/Common/AdapterUtil.Drivers.cs

@@ -0,0 +1,35 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Threading;
+
+namespace System.Data.Common
+{
+    internal static partial class ADP
+    {
+
+        internal static Timer UnsafeCreateTimer(TimerCallback callback, object state, int dueTime, int period)
+        {
+            // Don't capture the current ExecutionContext and its AsyncLocals onto 
+            // a global timer causing them to live forever
+            bool restoreFlow = false;
+            try
+            {
+                if (!ExecutionContext.IsFlowSuppressed())
+                {
+                    ExecutionContext.SuppressFlow();
+                    restoreFlow = true;
+                }
+
+                return new Timer(callback, state, dueTime, period);
+            }
+            finally
+            {
+                // Restore the current ExecutionContext
+                if (restoreFlow)
+                    ExecutionContext.RestoreFlow();
+            }
+        }
+    }
+}

src/System.Data.SqlClient/src/System.Data.SqlClient.csproj

@@ -55,6 +55,9 @@
     <Compile Include="$(CommonPath)\System\Data\Common\AdapterUtil.cs">
       <Link>System\Data\Common\AdapterUtil.cs</Link>
     </Compile>
+    <Compile Include="$(CommonPath)\System\Data\Common\AdapterUtil.Drivers.cs">
+      <Link>System\Data\Common\AdapterUtil.Drivers.cs</Link>
+    </Compile>
     <Compile Include="System\Data\Common\AdapterUtil.SqlClient.cs" />
     <Compile Include="System\Data\Common\SR.cs" />
     <Compile Include="System\Data\Common\DbConnectionOptions.cs" />

src/System.Data.SqlClient/src/System/Data/ProviderBase/DbConnectionFactory.cs

@@ -123,11 +123,12 @@ virtual internal DbConnectionPoolGroupProviderInfo CreateConnectionPoolGroupProv
             return null;
         }
 
-        private Timer CreatePruningTimer()
-        {
-            TimerCallback callback = new TimerCallback(PruneConnectionPoolGroups);
-            return new Timer(callback, null, PruningDueTime, PruningPeriod);
-        }
+        private Timer CreatePruningTimer() => 
+            ADP.UnsafeCreateTimer(
+                new TimerCallback(PruneConnectionPoolGroups),
+                null,
+                PruningDueTime,
+                PruningPeriod);
 
         protected DbConnectionOptions FindConnectionOptions(DbConnectionPoolKey key)
         {

src/System.Data.SqlClient/src/System/Data/ProviderBase/DbConnectionPool.cs

@@ -664,10 +664,12 @@ internal void Clear()
             ReclaimEmancipatedObjects();
         }
 
-        private Timer CreateCleanupTimer()
-        {
-            return (new Timer(new TimerCallback(this.CleanupCallback), null, _cleanupWait, _cleanupWait));
-        }
+        private Timer CreateCleanupTimer() =>
+            ADP.UnsafeCreateTimer(
+                new TimerCallback(CleanupCallback),
+                null,
+                _cleanupWait,
+                _cleanupWait);
 
         private DbConnectionInternal CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
         {
@@ -728,6 +730,7 @@ private DbConnectionInternal CreateObject(DbConnection owningObject, DbConnectio
 
                 // timer allocation has to be done out of CER block
                 Timer t = new Timer(new TimerCallback(this.ErrorCallback), null, Timeout.Infinite, Timeout.Infinite);
+
                 bool timerIsNotDisposed;
                 try { }
                 finally

src/System.Data.SqlClient/src/System/Data/SqlClient/SqlDependencyListener.cs

@@ -612,7 +612,12 @@ private void Restart(object unused)
                         _timeoutParam.Value = _defaultWaitforTimeout; // If success, reset to default for re-queue.
                         AsynchronouslyQueryServiceBrokerQueue();
                         _errorState = false;
-                        _retryTimer = null;
+                        Timer retryTimer = _retryTimer;
+                        if (retryTimer != null)
+                        {
+                            _retryTimer = null;
+                            retryTimer.Dispose();
+                        }
                     }
                 }
 
@@ -1470,4 +1475,4 @@ internal bool Stop(
 
          return stopped;
     }
-}
+}

src/System.Data.SqlClient/src/System/Data/SqlClient/SqlDependencyUtils.cs

@@ -80,7 +80,11 @@ private SqlDependencyPerAppDomainDispatcher()
             _notificationIdToDependenciesHash = new Dictionary<string, DependencyList>();
             _commandHashToNotificationId = new Dictionary<string, string>();
 
-            _timeoutTimer = new Timer(new TimerCallback(TimeoutTimerCallback), null, Timeout.Infinite, Timeout.Infinite);
+            _timeoutTimer = ADP.UnsafeCreateTimer(
+                new TimerCallback(TimeoutTimerCallback),
+                null,
+                Timeout.Infinite,
+                Timeout.Infinite);
 
             SubscribeToAppDomainUnload();
         }

src/System.Data.SqlClient/src/System/Data/SqlClient/TdsParserStateObject.cs

@@ -2295,7 +2295,11 @@ internal void ReadSni(TaskCompletionSource<object> completion)
 
                 if (_networkPacketTimeout == null)
                 {
-                    _networkPacketTimeout = new Timer(OnTimeout, null, Timeout.Infinite, Timeout.Infinite);
+                    _networkPacketTimeout = ADP.UnsafeCreateTimer(
+                        new TimerCallback(OnTimeout),
+                        null,
+                        Timeout.Infinite,
+                        Timeout.Infinite);
                 }
 
                 // -1 == Infinite