Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Workflow.Runtime/ExecutorLocksHeldException.cs

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+// ****************************************************************************
+// Copyright (C) 2000-2001 Microsoft Corporation.  All rights reserved.
+//
+// CONTENTS
+//     Workflow Base exception class
+// 
+// DESCRIPTION
+//     Base class for WINOE Runtime engine exception
+//
+// REVISIONS
+// Date          Ver     By           Remarks
+// ~~~~~~~~~~    ~~~     ~~~~~~~~     ~~~~~~~~~~~~~~
+// 03/08/01      1.0     [....]       Created.
+// ****************************************************************************
+using System;
+using System.Runtime.Serialization;
+using System.Security.Permissions;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Threading;
+using System.Workflow;
+using System.Workflow.Runtime;
+using System.Workflow.ComponentModel;
+
+namespace System.Workflow.Runtime
+{
+    /*
+     * The Unload() method has been changed so that
+     * any Unload requests made while in the middle of an atomic
+     * transaction wait for the atomic transaction to complete.
+     * This makes use of an ManualResetEvent. Unload() waits on the event:
+     *      theEvent.WaitOne()
+     * But waiting with the executor and scheduler locks held
+     * will block everything else.
+     * 
+     * The solution is to have a custom internal exception class that has the
+     * ManualResetEvent as an internal property. If Unload() finds itself in the middle
+     * of an atomic transaction, it throws the Exception. The Exception is propogated upwards
+     * until we reach the method that was the first to grab the executor lock. 
+     *
+     * We then drop that lock and wait on the event handle. As soon as the handle is
+     * Set() by DisposeTransaction(), we grab the executor lock and do everything all over.
+     */
+
+    internal class ExecutorLocksHeldException : Exception
+    {
+        private ManualResetEvent handle;
+
+        public ExecutorLocksHeldException(ManualResetEvent handle)
+        {
+            this.handle = handle;
+        }
+
+        internal ManualResetEvent Handle
+        {
+            get
+            {
+                return handle;
+            }
+        }
+    }
+}