Remove another concurrency issue possibility

Author: fredericDelaporte

src/NHibernate/ISession.cs

@@ -243,8 +243,11 @@ public partial interface ISession : IDisposable
 		/// End the <c>ISession</c> by disconnecting from the ADO.NET connection and cleaning up.
 		/// </summary>
 		/// <remarks>
-		/// It is not strictly necessary to <c>Close()</c> the <c>ISession</c> but you must
-		/// at least <c>Disconnect()</c> it.
+		/// <para>It is not strictly necessary to <c>Close()</c> the <c>ISession</c> but you must
+		/// at least <c>Disconnect()</c> or <c>Dispose</c> it.</para>
+		/// <para>Do not call this method inside a transaction scope, use <c>Dispose</c> instead,
+		/// since <c>Close()</c> is not aware of system transactions: if the transaction completion
+		/// requires the session, it will fail.</para>
 		/// </remarks>
 		/// <returns>The connection provided by the application or <see langword="null" /></returns>
 		DbConnection Close();

src/NHibernate/Impl/SessionImpl.cs

@@ -264,16 +264,10 @@ public bool ShouldAutoClose
 			get { return IsAutoCloseSessionEnabled && !IsClosed; }
 		}
 
-		/// <summary>
-		/// Close the session and release all resources
-		/// <remarks>
-		/// Do not call this method inside a transaction scope, use <c>Dispose</c> instead, since
-		/// Close() is not aware of distributed transactions
-		/// </remarks>
-		/// </summary>
+		/// <inheritdoc />
 		public DbConnection Close()
 		{
-			using (BeginContext())
+			using (BeginProcess(true))
 			{
 				log.Debug("closing session");
 				if (IsClosed)
@@ -1498,7 +1492,8 @@ public void Dispose()
 				// a local variable for avoiding it, but that would turn a failure causing an exception
 				// into a failure causing a session and connection leak. So do not do it, better blow away
 				// with a null ref rather than silently leaking a session. And then fix the synchronization.
-				if (TransactionContext != null && TransactionContext.CanFlushOnSystemTransactionCompleted)
+				if (TransactionContext != null && TransactionContext.CanFlushOnSystemTransactionCompleted &&
+					TransactionContext.IsInActiveTransaction)
 				{
 					TransactionContext.ShouldCloseSessionOnSystemTransactionCompleted = true;
 					return;

src/NHibernate/Transaction/AdoNetWithSystemTransactionFactory.cs

@@ -299,8 +299,8 @@ protected virtual void Lock()
 			{
 				if (!_needCompletionLocking || _isDisposed)
 					return;
-				_needCompletionLocking = false;
 				_lock.Reset();
+				_needCompletionLocking = false;
 			}
 
 			/// <summary>
@@ -583,7 +583,7 @@ private static void Cleanup(ISessionImplementor session)
 				foreach (var dependentSession in session.ConnectionManager.DependentSessions.ToList())
 				{
 					var dependentContext = dependentSession.TransactionContext;
-					// Do not nullify TransactionContext here, could create a race condition with
+					// Do not nullify TransactionContext here, it could create a race condition with
 					// would be await-er on session for disposal (test cases cleanup checks by example).
 					if (dependentContext == null)
 						continue;