mcs/class/corlib/System.Threading.Tasks/Task.cs

   1 //
   2 // Task.cs
   3 //
   4 // Authors:
   5 //    Marek Safar  <marek.safar@gmail.com>
   6 //    Jérémie Laval <jeremie dot laval at xamarin dot com>
   7 //
   8 // Copyright (c) 2008 Jérémie "Garuma" Laval
   9 // Copyright 2011-2013 Xamarin Inc (http://www.xamarin.com).
  10 //
  11 // Permission is hereby granted, free of charge, to any person obtaining a copy
  12 // of this software and associated documentation files (the "Software"), to deal
  13 // in the Software without restriction, including without limitation the rights
  14 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  15 // copies of the Software, and to permit persons to whom the Software is
  16 // furnished to do so, subject to the following conditions:
  17 //
  18 // The above copyright notice and this permission notice shall be included in
  19 // all copies or substantial portions of the Software.
  20 //
  21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  22 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  23 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  24 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  25 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  26 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  27 // THE SOFTWARE.
  28 //
  29 //
  30
  31 #if NET_4_0
  32
  33 using System;
  34 using System.Threading;
  35 using System.Collections.Concurrent;
  36 using System.Collections.Generic;
  37 using System.Runtime.CompilerServices;
  38
  39 namespace System.Threading.Tasks
  40 {
  41         [System.Diagnostics.DebuggerDisplay ("Id = {Id}, Status = {Status}")]
  42         [System.Diagnostics.DebuggerTypeProxy (typeof (TaskDebuggerView))]
  43         public class Task : IDisposable, IAsyncResult
  44         {
  45                 // With this attribute each thread has its own value so that it's correct for our Schedule code
  46                 // and for Parent property.
  47                 [System.ThreadStatic]
  48                 static Task current;
  49
  50                 // parent is the outer task in which this task is created
  51                 readonly Task parent;
  52                 // A reference to a Task on which this continuation is attached to
  53                 Task contAncestor;
  54
  55                 static int          id = -1;
  56                 static readonly TaskFactory defaultFactory = new TaskFactory ();
  57
  58                 CountdownEvent childTasks;
  59
  60                 int                 taskId;
  61                 TaskCreationOptions creationOptions;
  62
  63                 internal TaskScheduler       scheduler;
  64
  65                 TaskExceptionSlot exSlot;
  66                 ManualResetEvent wait_handle;
  67
  68                 TaskStatus          status;
  69
  70                 TaskActionInvoker invoker;
  71                 object         state;
  72                 internal AtomicBooleanValue executing;
  73
  74                 TaskCompletionQueue<IContinuation> continuations;
  75
  76                 CancellationToken token;
  77                 CancellationTokenRegistration? cancellationRegistration;
  78
  79                 internal const TaskCreationOptions WorkerTaskNotSupportedOptions = TaskCreationOptions.LongRunning | TaskCreationOptions.PreferFairness;
  80
  81                 const TaskCreationOptions MaxTaskCreationOptions =
  82 #if NET_4_5
  83                         TaskCreationOptions.DenyChildAttach | TaskCreationOptions.HideScheduler |
  84 #endif
  85                         TaskCreationOptions.PreferFairness | TaskCreationOptions.LongRunning | TaskCreationOptions.AttachedToParent;
  86
  87                 public Task (Action action)
  88                         : this (action, TaskCreationOptions.None)
  89                 {
  90
  91                 }
  92
  93                 public Task (Action action, TaskCreationOptions creationOptions)
  94                         : this (action, CancellationToken.None, creationOptions)
  95                 {
  96
  97                 }
  98
  99                 public Task (Action action, CancellationToken cancellationToken)
 100                         : this (action, cancellationToken, TaskCreationOptions.None)
 101                 {
 102
 103                 }
 104
 105                 public Task (Action action, CancellationToken cancellationToken, TaskCreationOptions creationOptions)
 106                         : this (TaskActionInvoker.Create (action), null, cancellationToken, creationOptions, current)
 107                 {
 108                         if (action == null)
 109                                 throw new ArgumentNullException ("action");
 110                         if (creationOptions > MaxTaskCreationOptions || creationOptions < TaskCreationOptions.None)
 111                                 throw new ArgumentOutOfRangeException ("creationOptions");
 112                 }
 113
 114                 public Task (Action<object> action, object state)
 115                         : this (action, state, TaskCreationOptions.None)
 116                 {
 117                 }
 118
 119                 public Task (Action<object> action, object state, TaskCreationOptions creationOptions)
 120                         : this (action, state, CancellationToken.None, creationOptions)
 121                 {
 122                 }
 123
 124                 public Task (Action<object> action, object state, CancellationToken cancellationToken)
 125                         : this (action, state, cancellationToken, TaskCreationOptions.None)
 126                 {
 127                 }
 128
 129                 public Task (Action<object> action, object state, CancellationToken cancellationToken, TaskCreationOptions creationOptions)
 130                         : this (TaskActionInvoker.Create (action), state, cancellationToken, creationOptions, current)
 131                 {
 132                         if (action == null)
 133                                 throw new ArgumentNullException ("action");
 134                         if (creationOptions > MaxTaskCreationOptions || creationOptions < TaskCreationOptions.None)
 135                                 throw new ArgumentOutOfRangeException ("creationOptions");
 136                 }
 137
 138                 internal Task (TaskActionInvoker invoker, object state, CancellationToken cancellationToken,
 139                                TaskCreationOptions creationOptions, Task parent = null, Task contAncestor = null, bool ignoreCancellation = false)
 140                 {
 141                         this.invoker         = invoker;
 142                         this.creationOptions = creationOptions;
 143                         this.state           = state;
 144                         this.taskId          = Interlocked.Increment (ref id);
 145                         this.token           = cancellationToken;
 146                         this.parent          = parent = parent == null ? current : parent;
 147                         this.contAncestor    = contAncestor;
 148                         this.status          = cancellationToken.IsCancellationRequested && !ignoreCancellation ? TaskStatus.Canceled : TaskStatus.Created;
 149
 150                         // Process creationOptions
 151 #if NET_4_5
 152                         if (parent != null && HasFlag (creationOptions, TaskCreationOptions.AttachedToParent)
 153                             && !HasFlag (parent.CreationOptions, TaskCreationOptions.DenyChildAttach))
 154 #else
 155                         if (parent != null && HasFlag (creationOptions, TaskCreationOptions.AttachedToParent))
 156 #endif
 157                                 parent.AddChild ();
 158
 159                         if (token.CanBeCanceled && !ignoreCancellation)
 160                                 cancellationRegistration = token.Register (l => ((Task) l).CancelReal (), this);
 161                 }
 162
 163                 static bool HasFlag (TaskCreationOptions opt, TaskCreationOptions member)
 164                 {
 165                         return (opt & member) == member;
 166                 }
 167
 168                 #region Start
 169                 public void Start ()
 170                 {
 171                         Start (TaskScheduler.Current);
 172                 }
 173
 174                 public void Start (TaskScheduler scheduler)
 175                 {
 176                         if (scheduler == null)
 177                                 throw new ArgumentNullException ("scheduler");
 178
 179                         if (status >= TaskStatus.WaitingToRun)
 180                                 throw new InvalidOperationException ("The Task is not in a valid state to be started.");
 181
 182                         if (IsContinuation)
 183                                 throw new InvalidOperationException ("Start may not be called on a continuation task");
 184
 185                         if (IsPromise)
 186                                 throw new InvalidOperationException ("Start may not be called on a promise-style task");
 187
 188                         SetupScheduler (scheduler);
 189                         Schedule ();
 190                 }
 191
 192                 internal void SetupScheduler (TaskScheduler scheduler)
 193                 {
 194                         this.scheduler = scheduler;
 195                         Status = TaskStatus.WaitingForActivation;
 196                 }
 197
 198                 public void RunSynchronously ()
 199                 {
 200                         RunSynchronously (TaskScheduler.Current);
 201                 }
 202
 203                 public void RunSynchronously (TaskScheduler scheduler)
 204                 {
 205                         if (scheduler == null)
 206                                 throw new ArgumentNullException ("scheduler");
 207
 208                         if (Status > TaskStatus.WaitingForActivation)
 209                                 throw new InvalidOperationException ("The task is not in a valid state to be started");
 210
 211                         if (IsContinuation)
 212                                 throw new InvalidOperationException ("RunSynchronously may not be called on a continuation task");
 213
 214                         if (IsPromise)
 215                                 throw new InvalidOperationException ("RunSynchronously may not be called on a promise-style task");
 216
 217                         RunSynchronouslyCore (scheduler);
 218                 }
 219
 220                 internal void RunSynchronouslyCore (TaskScheduler scheduler)
 221                 {
 222                         SetupScheduler (scheduler);
 223                         Status = TaskStatus.WaitingToRun;
 224
 225                         try {
 226                                 if (scheduler.RunInline (this, false))
 227                                         return;
 228                         } catch (Exception inner) {
 229                                 throw new TaskSchedulerException (inner);
 230                         }
 231
 232                         Schedule ();
 233                         WaitCore (Timeout.Infinite, CancellationToken.None, false);
 234                 }
 235                 #endregion
 236
 237                 #region ContinueWith
 238                 public Task ContinueWith (Action<Task> continuationAction)
 239                 {
 240                         return ContinueWith (continuationAction, TaskContinuationOptions.None);
 241                 }
 242
 243                 public Task ContinueWith (Action<Task> continuationAction, TaskContinuationOptions continuationOptions)
 244                 {
 245                         return ContinueWith (continuationAction, CancellationToken.None, continuationOptions, TaskScheduler.Current);
 246                 }
 247
 248                 public Task ContinueWith (Action<Task> continuationAction, CancellationToken cancellationToken)
 249                 {
 250                         return ContinueWith (continuationAction, cancellationToken, TaskContinuationOptions.None, TaskScheduler.Current);
 251                 }
 252
 253                 public Task ContinueWith (Action<Task> continuationAction, TaskScheduler scheduler)
 254                 {
 255                         return ContinueWith (continuationAction, CancellationToken.None, TaskContinuationOptions.None, scheduler);
 256                 }
 257
 258                 public Task ContinueWith (Action<Task> continuationAction, CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
 259                 {
 260                         if (continuationAction == null)
 261                                 throw new ArgumentNullException ("continuationAction");
 262                         if (scheduler == null)
 263                                 throw new ArgumentNullException ("scheduler");
 264
 265                         return ContinueWith (TaskActionInvoker.Create (continuationAction), cancellationToken, continuationOptions, scheduler);
 266                 }
 267
 268                 internal Task ContinueWith (TaskActionInvoker invoker, CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
 269                 {
 270                         var lazyCancellation = false;
 271 #if NET_4_5
 272                         lazyCancellation = (continuationOptions & TaskContinuationOptions.LazyCancellation) > 0;
 273 #endif
 274                         var continuation = new Task (invoker, null, cancellationToken, GetCreationOptions (continuationOptions), null, this, lazyCancellation);
 275                         ContinueWithCore (continuation, continuationOptions, scheduler);
 276
 277                         return continuation;
 278                 }
 279
 280                 public Task<TResult> ContinueWith<TResult> (Func<Task, TResult> continuationFunction)
 281                 {
 282                         return ContinueWith<TResult> (continuationFunction, TaskContinuationOptions.None);
 283                 }
 284
 285                 public Task<TResult> ContinueWith<TResult> (Func<Task, TResult> continuationFunction, TaskContinuationOptions continuationOptions)
 286                 {
 287                         return ContinueWith<TResult> (continuationFunction, CancellationToken.None, continuationOptions, TaskScheduler.Current);
 288                 }
 289
 290                 public Task<TResult> ContinueWith<TResult> (Func<Task, TResult> continuationFunction, CancellationToken cancellationToken)
 291                 {
 292                         return ContinueWith<TResult> (continuationFunction, cancellationToken, TaskContinuationOptions.None, TaskScheduler.Current);
 293                 }
 294
 295                 public Task<TResult> ContinueWith<TResult> (Func<Task, TResult> continuationFunction, TaskScheduler scheduler)
 296                 {
 297                         return ContinueWith<TResult> (continuationFunction, CancellationToken.None, TaskContinuationOptions.None, scheduler);
 298                 }
 299
 300                 public Task<TResult> ContinueWith<TResult> (Func<Task, TResult> continuationFunction, CancellationToken cancellationToken,
 301                                                             TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
 302                 {
 303                         if (continuationFunction == null)
 304                                 throw new ArgumentNullException ("continuationFunction");
 305                         if (scheduler == null)
 306                                 throw new ArgumentNullException ("scheduler");
 307
 308                         return ContinueWith<TResult> (TaskActionInvoker.Create (continuationFunction), cancellationToken, continuationOptions, scheduler);
 309                 }
 310
 311                 internal Task<TResult> ContinueWith<TResult> (TaskActionInvoker invoker, CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
 312                 {
 313                         var lazyCancellation = false;
 314 #if NET_4_5
 315                         lazyCancellation = (continuationOptions & TaskContinuationOptions.LazyCancellation) > 0;
 316 #endif
 317                         var continuation = new Task<TResult> (invoker, null, cancellationToken, GetCreationOptions (continuationOptions), parent, this, lazyCancellation);
 318                         ContinueWithCore (continuation, continuationOptions, scheduler);
 319
 320                         return continuation;
 321                 }
 322
 323                 internal void ContinueWithCore (Task continuation, TaskContinuationOptions options, TaskScheduler scheduler)
 324                 {
 325                         const TaskContinuationOptions wrongRan = TaskContinuationOptions.NotOnRanToCompletion | TaskContinuationOptions.OnlyOnRanToCompletion;
 326                         const TaskContinuationOptions wrongCanceled = TaskContinuationOptions.NotOnCanceled | TaskContinuationOptions.OnlyOnCanceled;
 327                         const TaskContinuationOptions wrongFaulted = TaskContinuationOptions.NotOnFaulted | TaskContinuationOptions.OnlyOnFaulted;
 328
 329                         if (((options & wrongRan) == wrongRan) || ((options & wrongCanceled) == wrongCanceled) || ((options & wrongFaulted) == wrongFaulted))
 330                                 throw new ArgumentException ("continuationOptions", "Some options are mutually exclusive");
 331
 332                         // Already set the scheduler so that user can call Wait and that sort of stuff
 333                         continuation.scheduler = scheduler;
 334                         continuation.Status = TaskStatus.WaitingForActivation;
 335
 336                         ContinueWith (new TaskContinuation (continuation, options));
 337                 }
 338
 339                 internal bool ContinueWith (IContinuation continuation, bool canExecuteInline = true)
 340                 {
 341                         if (IsCompleted) {
 342                                 if (!canExecuteInline)
 343                                         return false;
 344
 345                                 continuation.Execute ();
 346                                 return true;
 347                         }
 348
 349                         continuations.Add (continuation);
 350
 351                         // Retry in case completion was achieved but event adding was too late
 352                         if (IsCompleted) {
 353                                 continuations.Remove (continuation);
 354                                 if (!canExecuteInline)
 355                                         return false;
 356
 357                                 continuation.Execute ();
 358                         }
 359
 360                         return true;
 361                 }
 362
 363                 internal void RemoveContinuation (IContinuation continuation)
 364                 {
 365                         continuations.Remove (continuation);
 366                 }
 367
 368                 static internal TaskCreationOptions GetCreationOptions (TaskContinuationOptions kind)
 369                 {
 370                         TaskCreationOptions options = TaskCreationOptions.None;
 371                         if ((kind & TaskContinuationOptions.AttachedToParent) > 0)
 372                                 options |= TaskCreationOptions.AttachedToParent;
 373                         if ((kind & TaskContinuationOptions.PreferFairness) > 0)
 374                                 options |= TaskCreationOptions.PreferFairness;
 375                         if ((kind & TaskContinuationOptions.LongRunning) > 0)
 376                                 options |= TaskCreationOptions.LongRunning;
 377
 378                         return options;
 379                 }
 380                 #endregion
 381
 382                 #region Internal and protected thingies
 383                 internal void Schedule ()
 384                 {
 385                         Status = TaskStatus.WaitingToRun;
 386                         scheduler.QueueTask (this);
 387                 }
 388
 389                 void ThreadStart ()
 390                 {
 391                         /* Allow scheduler to break fairness of deque ordering without
 392                          * breaking its semantic (the task can be executed twice but the
 393                          * second time it will return immediately
 394                          */
 395                         if (!executing.TryRelaxedSet ())
 396                                 return;
 397
 398                         // Disable CancellationToken direct cancellation
 399                         if (cancellationRegistration != null) {
 400                                 cancellationRegistration.Value.Dispose ();
 401                                 cancellationRegistration = null;
 402                         }
 403
 404                         // If Task are ran inline on the same thread we might trash these values
 405                         var saveCurrent = current;
 406                         var saveScheduler = TaskScheduler.Current;
 407
 408                         current = this;
 409 #if NET_4_5
 410                         TaskScheduler.Current = HasFlag (creationOptions, TaskCreationOptions.HideScheduler) ? TaskScheduler.Default : scheduler;
 411 #else
 412                         TaskScheduler.Current = scheduler;
 413 #endif
 414
 415                         if (!token.IsCancellationRequested) {
 416
 417                                 status = TaskStatus.Running;
 418
 419                                 try {
 420                                         InnerInvoke ();
 421                                 } catch (OperationCanceledException oce) {
 422                                         if (token != CancellationToken.None && oce.CancellationToken == token)
 423                                                 CancelReal ();
 424                                         else
 425                                                 HandleGenericException (oce);
 426                                 } catch (Exception e) {
 427                                         HandleGenericException (e);
 428                                 }
 429                         } else {
 430                                 CancelReal ();
 431                         }
 432
 433                         if (saveCurrent != null)
 434                                 current = saveCurrent;
 435                         if (saveScheduler != null)
 436                                 TaskScheduler.Current = saveScheduler;
 437                         Finish ();
 438                 }
 439
 440                 internal bool TrySetCanceled ()
 441                 {
 442                         if (IsCompleted)
 443                                 return false;
 444
 445                         if (!executing.TryRelaxedSet ()) {
 446                                 var sw = new SpinWait ();
 447                                 while (!IsCompleted)
 448                                         sw.SpinOnce ();
 449
 450                                 return false;
 451                         }
 452
 453                         CancelReal ();
 454                         return true;
 455                 }
 456
 457                 internal bool TrySetException (AggregateException aggregate, bool cancellation)
 458                 {
 459                         if (IsCompleted)
 460                                 return false;
 461
 462                         if (!executing.TryRelaxedSet ()) {
 463                                 var sw = new SpinWait ();
 464                                 while (!IsCompleted)
 465                                         sw.SpinOnce ();
 466
 467                                 return false;
 468                         }
 469
 470                         if (cancellation) {
 471                                 ExceptionSlot.Exception = aggregate;
 472                                 Thread.MemoryBarrier ();
 473
 474                                 CancelReal ();
 475                         } else {
 476                                 HandleGenericException (aggregate);
 477                         }
 478
 479                         return true;
 480                 }
 481
 482                 internal bool TrySetExceptionObserved ()
 483                 {
 484                         if (exSlot != null) {
 485                                 exSlot.Observed = true;
 486                                 return true;
 487                         }
 488                         return false;
 489                 }
 490
 491                 internal void Execute ()
 492                 {
 493                         ThreadStart ();
 494                 }
 495
 496                 internal void AddChild ()
 497                 {
 498                         if (childTasks == null)
 499                                 Interlocked.CompareExchange (ref childTasks, new CountdownEvent (1), null);
 500                         childTasks.AddCount ();
 501                 }
 502
 503                 internal void ChildCompleted (AggregateException childEx)
 504                 {
 505                         if (childEx != null) {
 506                                 if (ExceptionSlot.ChildExceptions == null)
 507                                         Interlocked.CompareExchange (ref ExceptionSlot.ChildExceptions, new ConcurrentQueue<AggregateException> (), null);
 508                                 ExceptionSlot.ChildExceptions.Enqueue (childEx);
 509                         }
 510
 511                         if (childTasks.Signal () && status == TaskStatus.WaitingForChildrenToComplete) {
 512                                 ProcessChildExceptions ();
 513                                 Status = exSlot == null ? TaskStatus.RanToCompletion : TaskStatus.Faulted;
 514                                 ProcessCompleteDelegates ();
 515                                 if (parent != null &&
 516 #if NET_4_5
 517                                     !HasFlag (parent.CreationOptions, TaskCreationOptions.DenyChildAttach) &&
 518 #endif
 519                                         HasFlag (creationOptions, TaskCreationOptions.AttachedToParent))
 520                                         parent.ChildCompleted (this.Exception);
 521                         }
 522                 }
 523
 524                 void InnerInvoke ()
 525                 {
 526                         if (IsContinuation) {
 527                                 var ancestor = contAncestor;
 528                                 contAncestor = null;
 529                                 invoker.Invoke (ancestor, state, this);
 530                         } else {
 531                                 invoker.Invoke (this, state, this);
 532                         }
 533                 }
 534
 535                 internal void Finish ()
 536                 {
 537                         // If there was children created and they all finished, we set the countdown
 538                         if (childTasks != null) {
 539                                 if (childTasks.Signal ())
 540                                         ProcessChildExceptions (true);
 541                         }
 542
 543                         // Don't override Canceled or Faulted
 544                         if (status == TaskStatus.Running) {
 545                                 if (childTasks == null || childTasks.IsSet)
 546                                         Status = TaskStatus.RanToCompletion;
 547                                 else
 548                                         Status = TaskStatus.WaitingForChildrenToComplete;
 549                         }
 550
 551                         if (wait_handle != null)
 552                                 wait_handle.Set ();
 553
 554                         // Tell parent that we are finished
 555                         if (parent != null && HasFlag (creationOptions, TaskCreationOptions.AttachedToParent) &&
 556 #if NET_4_5
 557                             !HasFlag (parent.CreationOptions, TaskCreationOptions.DenyChildAttach) &&
 558 #endif
 559                                 status != TaskStatus.WaitingForChildrenToComplete) {
 560                                 parent.ChildCompleted (this.Exception);
 561                         }
 562
 563                         // Completions are already processed when task is canceled or faulted
 564                         if (status == TaskStatus.RanToCompletion)
 565                                 ProcessCompleteDelegates ();
 566
 567                         // Reset the current thingies
 568                         if (current == this)
 569                                 current = null;
 570                         if (TaskScheduler.Current == scheduler)
 571                                 TaskScheduler.Current = null;
 572
 573                         if (cancellationRegistration.HasValue)
 574                                 cancellationRegistration.Value.Dispose ();
 575                 }
 576
 577                 void ProcessCompleteDelegates ()
 578                 {
 579                         if (continuations.HasElements) {
 580                                 IContinuation continuation;
 581                                 while (continuations.TryGetNextCompletion (out continuation))
 582                                         continuation.Execute ();
 583                         }
 584                 }
 585
 586                 void ProcessChildExceptions (bool isParent = false)
 587                 {
 588                         if (exSlot == null || exSlot.ChildExceptions == null)
 589                                 return;
 590
 591                         if (ExceptionSlot.Exception == null)
 592                                 exSlot.Exception = new AggregateException ();
 593
 594                         AggregateException childEx;
 595                         while (exSlot.ChildExceptions.TryDequeue (out childEx))
 596                                 exSlot.Exception.AddChildException (childEx);
 597
 598                         if (isParent) {
 599                                 Status = TaskStatus.Faulted;
 600                                 ProcessCompleteDelegates ();
 601                         }
 602                 }
 603                 #endregion
 604
 605                 #region Cancel and Wait related method
 606
 607                 internal void CancelReal ()
 608                 {
 609                         Status = TaskStatus.Canceled;
 610
 611                         if (wait_handle != null)
 612                                 wait_handle.Set ();
 613
 614                         ProcessCompleteDelegates ();
 615                 }
 616
 617                 void HandleGenericException (Exception e)
 618                 {
 619                         HandleGenericException (new AggregateException (e));
 620                 }
 621
 622                 void HandleGenericException (AggregateException e)
 623                 {
 624                         ExceptionSlot.Exception = e;
 625                         Thread.MemoryBarrier ();
 626                         Status = TaskStatus.Faulted;
 627
 628                         if (wait_handle != null)
 629                                 wait_handle.Set ();
 630
 631                         ProcessCompleteDelegates ();
 632                 }
 633
 634                 internal bool WaitOnChildren ()
 635                 {
 636                         if (Status == TaskStatus.WaitingForChildrenToComplete && childTasks != null) {
 637                                 childTasks.Wait ();
 638                                 return true;
 639                         }
 640                         return false;
 641                 }
 642
 643                 public void Wait ()
 644                 {
 645                         Wait (Timeout.Infinite, CancellationToken.None);
 646                 }
 647
 648                 public void Wait (CancellationToken cancellationToken)
 649                 {
 650                         Wait (Timeout.Infinite, cancellationToken);
 651                 }
 652
 653                 public bool Wait (TimeSpan timeout)
 654                 {
 655                         return Wait (CheckTimeout (timeout), CancellationToken.None);
 656                 }
 657
 658                 public bool Wait (int millisecondsTimeout)
 659                 {
 660                         return Wait (millisecondsTimeout, CancellationToken.None);
 661                 }
 662
 663                 public bool Wait (int millisecondsTimeout, CancellationToken cancellationToken)
 664                 {
 665                         if (millisecondsTimeout < -1)
 666                                 throw new ArgumentOutOfRangeException ("millisecondsTimeout");
 667
 668                         bool result = WaitCore (millisecondsTimeout, cancellationToken, true);
 669
 670                         if (IsCanceled)
 671                                 throw new AggregateException (new TaskCanceledException (this));
 672
 673                         var exception = Exception;
 674                         if (exception != null)
 675                                 throw exception;
 676
 677                         return result;
 678                 }
 679
 680                 internal bool WaitCore (int millisecondsTimeout, CancellationToken cancellationToken, bool runInline)
 681                 {
 682                         if (IsCompleted)
 683                                 return true;
 684
 685                         // If the task is ready to be run and we were supposed to wait on it indefinitely without cancellation, just run it
 686                         if (runInline && Status == TaskStatus.WaitingToRun && millisecondsTimeout == Timeout.Infinite && scheduler != null && !cancellationToken.CanBeCanceled)
 687                                 scheduler.RunInline (this, true);
 688
 689                         bool result = true;
 690
 691                         if (!IsCompleted) {
 692                                 var continuation = new ManualResetContinuation ();
 693                                 try {
 694                                         ContinueWith (continuation);
 695                                         result = continuation.Event.Wait (millisecondsTimeout, cancellationToken);
 696                                 } finally {
 697                                         if (!result)
 698                                                 RemoveContinuation (continuation);
 699                                         continuation.Dispose ();
 700                                 }
 701                         }
 702
 703                         return result;
 704                 }
 705
 706                 public static void WaitAll (params Task[] tasks)
 707                 {
 708                         WaitAll (tasks, Timeout.Infinite, CancellationToken.None);
 709                 }
 710
 711                 public static void WaitAll (Task[] tasks, CancellationToken cancellationToken)
 712                 {
 713                         WaitAll (tasks, Timeout.Infinite, cancellationToken);
 714                 }
 715
 716                 public static bool WaitAll (Task[] tasks, TimeSpan timeout)
 717                 {
 718                         return WaitAll (tasks, CheckTimeout (timeout), CancellationToken.None);
 719                 }
 720
 721                 public static bool WaitAll (Task[] tasks, int millisecondsTimeout)
 722                 {
 723                         return WaitAll (tasks, millisecondsTimeout, CancellationToken.None);
 724                 }
 725
 726                 public static bool WaitAll (Task[] tasks, int millisecondsTimeout, CancellationToken cancellationToken)
 727                 {
 728                         if (tasks == null)
 729                                 throw new ArgumentNullException ("tasks");
 730
 731                         bool result = true;
 732                         foreach (var t in tasks) {
 733                                 if (t == null)
 734                                         throw new ArgumentException ("tasks", "the tasks argument contains a null element");
 735
 736                                 result &= t.Status == TaskStatus.RanToCompletion;
 737                         }
 738
 739                         if (!result) {
 740                                 var continuation = new CountdownContinuation (tasks.Length);
 741                                 try {
 742                                         foreach (var t in tasks)
 743                                                 t.ContinueWith (continuation);
 744
 745                                         result = continuation.Event.Wait (millisecondsTimeout, cancellationToken);
 746                                 } finally {
 747                                         List<Exception> exceptions = null;
 748
 749                                         foreach (var t in tasks) {
 750                                                 if (result) {
 751                                                         if (t.Status == TaskStatus.RanToCompletion)
 752                                                                 continue;
 753                                                         if (exceptions == null)
 754                                                                 exceptions = new List<Exception> ();
 755                                                         if (t.Exception != null)
 756                                                                 exceptions.AddRange (t.Exception.InnerExceptions);
 757                                                         else
 758                                                                 exceptions.Add (new TaskCanceledException (t));
 759                                                 } else {
 760                                                         t.RemoveContinuation (continuation);
 761                                                 }
 762                                         }
 763
 764                                         continuation.Dispose ();
 765
 766                                         if (exceptions != null)
 767                                                 throw new AggregateException (exceptions);
 768                                 }
 769                         }
 770
 771                         return result;
 772                 }
 773
 774                 public static int WaitAny (params Task[] tasks)
 775                 {
 776                         return WaitAny (tasks, Timeout.Infinite, CancellationToken.None);
 777                 }
 778
 779                 public static int WaitAny (Task[] tasks, TimeSpan timeout)
 780                 {
 781                         return WaitAny (tasks, CheckTimeout (timeout));
 782                 }
 783
 784                 public static int WaitAny (Task[] tasks, int millisecondsTimeout)
 785                 {
 786                         return WaitAny (tasks, millisecondsTimeout, CancellationToken.None);
 787                 }
 788
 789                 public static int WaitAny (Task[] tasks, CancellationToken cancellationToken)
 790                 {
 791                         return WaitAny (tasks, Timeout.Infinite, cancellationToken);
 792                 }
 793
 794                 public static int WaitAny (Task[] tasks, int millisecondsTimeout, CancellationToken cancellationToken)
 795                 {
 796                         if (tasks == null)
 797                                 throw new ArgumentNullException ("tasks");
 798                         if (millisecondsTimeout < -1)
 799                                 throw new ArgumentOutOfRangeException ("millisecondsTimeout");
 800                         CheckForNullTasks (tasks);
 801
 802                         if (tasks.Length > 0) {
 803                                 var continuation = new ManualResetContinuation ();
 804                                 bool result = false;
 805                                 try {
 806                                         for (int i = 0; i < tasks.Length; i++) {
 807                                                 var t = tasks[i];
 808                                                 if (t.IsCompleted)
 809                                                         return i;
 810                                                 t.ContinueWith (continuation);
 811                                         }
 812
 813                                         if (!(result = continuation.Event.Wait (millisecondsTimeout, cancellationToken)))
 814                                                 return -1;
 815                                 } finally {
 816                                         if (!result)
 817                                                 foreach (var t in tasks)
 818                                                         t.RemoveContinuation (continuation);
 819                                         continuation.Dispose ();
 820                                 }
 821                         }
 822
 823                         int firstFinished = -1;
 824                         for (int i = 0; i < tasks.Length; i++) {
 825                                 var t = tasks[i];
 826                                 if (t.IsCompleted) {
 827                                         firstFinished = i;
 828                                         break;
 829                                 }
 830                         }
 831
 832                         return firstFinished;
 833                 }
 834
 835                 static int CheckTimeout (TimeSpan timeout)
 836                 {
 837                         try {
 838                                 return checked ((int)timeout.TotalMilliseconds);
 839                         } catch (System.OverflowException) {
 840                                 throw new ArgumentOutOfRangeException ("timeout");
 841                         }
 842                 }
 843
 844                 static void CheckForNullTasks (Task[] tasks)
 845                 {
 846                         foreach (var t in tasks)
 847                                 if (t == null)
 848                                         throw new ArgumentException ("tasks", "the tasks argument contains a null element");
 849                 }
 850                 #endregion
 851
 852                 #region Dispose
 853                 public void Dispose ()
 854                 {
 855                         Dispose (true);
 856                 }
 857
 858                 protected virtual void Dispose (bool disposing)
 859                 {
 860                         if (!IsCompleted)
 861                                 throw new InvalidOperationException ("A task may only be disposed if it is in a completion state");
 862
 863                         // Set action to null so that the GC can collect the delegate and thus
 864                         // any big object references that the user might have captured in a anonymous method
 865                         if (disposing) {
 866                                 invoker = null;
 867                                 state = null;
 868                                 if (cancellationRegistration != null)
 869                                         cancellationRegistration.Value.Dispose ();
 870                                 if (wait_handle != null)
 871                                         wait_handle.Dispose ();
 872                         }
 873                 }
 874                 #endregion
 875
 876 #if NET_4_5
 877                 public
 878 #else
 879                 internal
 880 #endif
 881                 Task ContinueWith (Action<Task, object> continuationAction, object state, CancellationToken cancellationToken,
 882                                                                   TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
 883                 {
 884                         if (continuationAction == null)
 885                                 throw new ArgumentNullException ("continuationAction");
 886                         if (scheduler == null)
 887                                 throw new ArgumentNullException ("scheduler");
 888
 889                         Task continuation = new Task (TaskActionInvoker.Create (continuationAction),
 890                                                                                   state, cancellationToken,
 891                                                                                   GetCreationOptions (continuationOptions),
 892                                                       parent,
 893                                                       this);
 894                         ContinueWithCore (continuation, continuationOptions, scheduler);
 895
 896                         return continuation;
 897                 }
 898
 899 #if NET_4_5
 900
 901                 public ConfiguredTaskAwaitable ConfigureAwait (bool continueOnCapturedContext)
 902                 {
 903                         return new ConfiguredTaskAwaitable (this, continueOnCapturedContext);
 904                 }
 905
 906                 public Task ContinueWith (Action<Task, object> continuationAction, object state)
 907                 {
 908                         return ContinueWith (continuationAction, state, CancellationToken.None, TaskContinuationOptions.None, TaskScheduler.Current);
 909                 }
 910
 911                 public Task ContinueWith (Action<Task, object> continuationAction, object state, CancellationToken cancellationToken)
 912                 {
 913                         return ContinueWith (continuationAction, state, cancellationToken, TaskContinuationOptions.None, TaskScheduler.Current);
 914                 }
 915
 916                 public Task ContinueWith (Action<Task, object> continuationAction, object state, TaskContinuationOptions continuationOptions)
 917                 {
 918                         return ContinueWith (continuationAction, state, CancellationToken.None, continuationOptions, TaskScheduler.Current);
 919                 }
 920
 921                 public Task ContinueWith (Action<Task, object> continuationAction, object state, TaskScheduler scheduler)
 922                 {
 923                         return ContinueWith (continuationAction, state, CancellationToken.None, TaskContinuationOptions.None, scheduler);
 924                 }
 925
 926                 public Task<TResult> ContinueWith<TResult> (Func<Task, object, TResult> continuationFunction, object state)
 927                 {
 928                         return ContinueWith<TResult> (continuationFunction, state, CancellationToken.None, TaskContinuationOptions.None, TaskScheduler.Current);
 929                 }
 930
 931                 public Task<TResult> ContinueWith<TResult> (Func<Task, object, TResult> continuationFunction, object state, TaskContinuationOptions continuationOptions)
 932                 {
 933                         return ContinueWith<TResult> (continuationFunction, state, CancellationToken.None, continuationOptions, TaskScheduler.Current);
 934                 }
 935
 936                 public Task<TResult> ContinueWith<TResult> (Func<Task, object, TResult> continuationFunction, object state, CancellationToken cancellationToken)
 937                 {
 938                         return ContinueWith<TResult> (continuationFunction, state, cancellationToken, TaskContinuationOptions.None, TaskScheduler.Current);
 939                 }
 940
 941                 public Task<TResult> ContinueWith<TResult> (Func<Task, object, TResult> continuationFunction, object state, TaskScheduler scheduler)
 942                 {
 943                         return ContinueWith<TResult> (continuationFunction, state, CancellationToken.None, TaskContinuationOptions.None, scheduler);
 944                 }
 945
 946                 public Task<TResult> ContinueWith<TResult> (Func<Task, object, TResult> continuationFunction, object state, CancellationToken cancellationToken,
 947                                                                                                         TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
 948                 {
 949                         if (continuationFunction == null)
 950                                 throw new ArgumentNullException ("continuationFunction");
 951                         if (scheduler == null)
 952                                 throw new ArgumentNullException ("scheduler");
 953
 954                         var t = new Task<TResult> (TaskActionInvoker.Create (continuationFunction),
 955                                                    state,
 956                                                    cancellationToken,
 957                                                    GetCreationOptions (continuationOptions),
 958                                                    parent,
 959                                                    this);
 960
 961                         ContinueWithCore (t, continuationOptions, scheduler);
 962
 963                         return t;
 964                 }
 965
 966                 public static Task Delay (int millisecondsDelay)
 967                 {
 968                         return Delay (millisecondsDelay, CancellationToken.None);
 969                 }
 970
 971                 public static Task Delay (TimeSpan delay)
 972                 {
 973                         return Delay (CheckTimeout (delay), CancellationToken.None);
 974                 }
 975
 976                 public static Task Delay (TimeSpan delay, CancellationToken cancellationToken)
 977                 {
 978                         return Delay (CheckTimeout (delay), cancellationToken);
 979                 }
 980
 981                 public static Task Delay (int millisecondsDelay, CancellationToken cancellationToken)
 982                 {
 983                         if (millisecondsDelay < -1)
 984                                 throw new ArgumentOutOfRangeException ("millisecondsDelay");
 985
 986                         if (cancellationToken.IsCancellationRequested)
 987                                 return TaskConstants.Canceled;
 988
 989                         var task = new Task (TaskActionInvoker.Empty, null, cancellationToken, TaskCreationOptions.None, null, null);
 990                         task.SetupScheduler (TaskScheduler.Default);
 991
 992                         if (millisecondsDelay != Timeout.Infinite) {
 993                                 var timer = new Timer (delegate (object state) {
 994                                         var t = (Task) state;
 995                                         if (t.Status == TaskStatus.WaitingForActivation) {
 996                                                 t.Status = TaskStatus.Running;
 997                                                 t.Finish ();
 998                                         }
 999                                 }, task, millisecondsDelay, -1);
1000
1001                                 task.ContinueWith (new DisposeContinuation (timer));
1002                         }
1003
1004                         return task;
1005                 }
1006
1007                 public static Task<TResult> FromResult<TResult> (TResult result)
1008                 {
1009                         var tcs = new TaskCompletionSource<TResult> ();
1010                         tcs.SetResult (result);
1011                         return tcs.Task;
1012                 }
1013
1014                 public TaskAwaiter GetAwaiter ()
1015                 {
1016                         return new TaskAwaiter (this);
1017                 }
1018
1019                 public static Task Run (Action action)
1020                 {
1021                         return Run (action, CancellationToken.None);
1022                 }
1023
1024                 public static Task Run (Action action, CancellationToken cancellationToken)
1025                 {
1026                         if (cancellationToken.IsCancellationRequested)
1027                                 return TaskConstants.Canceled;
1028
1029                         return Task.Factory.StartNew (action, cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
1030                 }
1031
1032                 public static Task Run (Func<Task> function)
1033                 {
1034                         return Run (function, CancellationToken.None);
1035                 }
1036
1037                 public static Task Run (Func<Task> function, CancellationToken cancellationToken)
1038                 {
1039                         if (cancellationToken.IsCancellationRequested)
1040                                 return TaskConstants.Canceled;
1041
1042                         return TaskExtensionsImpl.Unwrap (Task.Factory.StartNew (function, cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default));
1043                 }
1044
1045                 public static Task<TResult> Run<TResult> (Func<TResult> function)
1046                 {
1047                         return Run (function, CancellationToken.None);
1048                 }
1049
1050                 public static Task<TResult> Run<TResult> (Func<TResult> function, CancellationToken cancellationToken)
1051                 {
1052                         if (cancellationToken.IsCancellationRequested)
1053                                 return TaskConstants<TResult>.Canceled;
1054
1055                         return Task.Factory.StartNew (function, cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
1056                 }
1057
1058                 public static Task<TResult> Run<TResult> (Func<Task<TResult>> function)
1059                 {
1060                         return Run (function, CancellationToken.None);
1061                 }
1062
1063                 public static Task<TResult> Run<TResult> (Func<Task<TResult>> function, CancellationToken cancellationToken)
1064                 {
1065                         if (cancellationToken.IsCancellationRequested)
1066                                 return TaskConstants<TResult>.Canceled;
1067
1068                         return TaskExtensionsImpl.Unwrap (Task.Factory.StartNew (function, cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default));
1069                 }
1070
1071                 public static Task WhenAll (params Task[] tasks)
1072                 {
1073                         if (tasks == null)
1074                                 throw new ArgumentNullException ("tasks");
1075
1076                         return WhenAllCore (tasks);
1077                 }
1078
1079                 public static Task WhenAll (IEnumerable<Task> tasks)
1080                 {
1081                         if (tasks == null)
1082                                 throw new ArgumentNullException ("tasks");
1083
1084                         // Call ToList on input enumeration or we end up
1085                         // enumerating it more than once
1086                         return WhenAllCore (new List<Task> (tasks));
1087                 }
1088
1089                 public static Task<TResult[]> WhenAll<TResult> (params Task<TResult>[] tasks)
1090                 {
1091                         if (tasks == null)
1092                                 throw new ArgumentNullException ("tasks");
1093
1094                         return WhenAllCore<TResult> (tasks);
1095                 }
1096
1097                 public static Task<TResult[]> WhenAll<TResult> (IEnumerable<Task<TResult>> tasks)
1098                 {
1099                         if (tasks == null)
1100                                 throw new ArgumentNullException ("tasks");
1101
1102                         // Call ToList on input enumeration or we end up
1103                         // enumerating it more than once
1104                         return WhenAllCore<TResult> (new List<Task<TResult>> (tasks));
1105                 }
1106
1107                 internal static Task<TResult[]> WhenAllCore<TResult> (IList<Task<TResult>> tasks)
1108                 {
1109                         if (tasks.Count == 0)
1110                                 return FromResult(new TResult[0]);
1111
1112                         foreach (var t in tasks) {
1113                                 if (t == null)
1114                                         throw new ArgumentException ("tasks", "the tasks argument contains a null element");
1115                         }
1116
1117                         var task = new Task<TResult[]> (TaskActionInvoker.Empty, null, CancellationToken.None, TaskCreationOptions.None, null, TaskConstants.Finished);
1118                         task.SetupScheduler (TaskScheduler.Current);
1119
1120                         var continuation = new WhenAllContinuation<TResult> (task, tasks);
1121                         foreach (var t in tasks)
1122                                 t.ContinueWith (continuation);
1123
1124                         return task;
1125                 }
1126
1127                 public static Task<Task> WhenAny (params Task[] tasks)
1128                 {
1129                         if (tasks == null)
1130                                 throw new ArgumentNullException ("tasks");
1131
1132                         return WhenAnyCore (tasks);
1133                 }
1134
1135                 public static Task<Task> WhenAny (IEnumerable<Task> tasks)
1136                 {
1137                         if (tasks == null)
1138                                 throw new ArgumentNullException ("tasks");
1139
1140                         return WhenAnyCore (new List<Task> (tasks));
1141                 }
1142
1143                 public static Task<Task<TResult>> WhenAny<TResult> (params Task<TResult>[] tasks)
1144                 {
1145                         if (tasks == null)
1146                                 throw new ArgumentNullException ("tasks");
1147
1148                         return WhenAnyCore<TResult> (tasks);
1149                 }
1150
1151                 public static Task<Task<TResult>> WhenAny<TResult> (IEnumerable<Task<TResult>> tasks)
1152                 {
1153                         if (tasks == null)
1154                                 throw new ArgumentNullException ("tasks");
1155
1156                         return WhenAnyCore<TResult> (new List<Task<TResult>> (tasks));
1157                 }
1158
1159                 static Task<Task<TResult>> WhenAnyCore<TResult> (IList<Task<TResult>> tasks)
1160                 {
1161                         if (tasks.Count == 0)
1162                                 throw new ArgumentException ("The tasks argument contains no tasks", "tasks");
1163
1164                         int completed_index = -1;
1165                         for (int i = 0; i < tasks.Count; ++i) {
1166                                 var t = tasks[i];
1167                                 if (t == null)
1168                                         throw new ArgumentException ("tasks", "the tasks argument contains a null element");
1169
1170                                 if (t.IsCompleted && completed_index < 0)
1171                                         completed_index = i;
1172                         }
1173
1174                         var task = new Task<Task<TResult>> (TaskActionInvoker.Empty, null, CancellationToken.None, TaskCreationOptions.None, null, TaskConstants.Finished);
1175
1176                         if (completed_index > 0) {
1177                                 task.TrySetResult (tasks[completed_index]);
1178                                 return task;
1179                         }
1180
1181                         task.SetupScheduler (TaskScheduler.Current);
1182
1183                         var continuation = new WhenAnyContinuation<Task<TResult>> (task, tasks);
1184                         foreach (var t in tasks)
1185                                 t.ContinueWith (continuation);
1186
1187                         return task;
1188                 }
1189
1190                 public static YieldAwaitable Yield ()
1191                 {
1192                         return new YieldAwaitable ();
1193                 }
1194 #endif
1195
1196                 internal static Task WhenAllCore (IList<Task> tasks)
1197                 {
1198                         bool all_completed = true;
1199                         foreach (var t in tasks) {
1200                                 if (t == null)
1201                                         throw new ArgumentException ("tasks", "the tasks argument contains a null element");
1202
1203                                 all_completed &= t.Status == TaskStatus.RanToCompletion;
1204                         }
1205
1206                         if (all_completed)
1207                                 return TaskConstants.Finished;
1208
1209                         var task = new Task (TaskActionInvoker.Empty, null, CancellationToken.None, TaskCreationOptions.None, null, TaskConstants.Finished);
1210                         task.SetupScheduler (TaskScheduler.Current);
1211
1212                         var continuation = new WhenAllContinuation (task, tasks);
1213                         foreach (var t in tasks)
1214                                 t.ContinueWith (continuation);
1215
1216                         return task;
1217                 }
1218
1219                 internal static Task<Task> WhenAnyCore (IList<Task> tasks)
1220                 {
1221                         if (tasks.Count == 0)
1222                                 throw new ArgumentException ("The tasks argument contains no tasks", "tasks");
1223
1224                         int completed_index = -1;
1225                         for (int i = 0; i < tasks.Count; ++i) {
1226                                 var t = tasks [i];
1227                                 if (t == null)
1228                                         throw new ArgumentException ("tasks", "the tasks argument contains a null element");
1229
1230                                 if (t.IsCompleted && completed_index < 0)
1231                                         completed_index = i;
1232                         }
1233
1234                         var task = new Task<Task> (TaskActionInvoker.Empty, null, CancellationToken.None, TaskCreationOptions.None, null, TaskConstants.Finished);
1235
1236                         if (completed_index > 0) {
1237                                 task.TrySetResult (tasks[completed_index]);
1238                                 return task;
1239                         }
1240
1241                         task.SetupScheduler (TaskScheduler.Current);
1242
1243                         var continuation = new WhenAnyContinuation<Task> (task, tasks);
1244                         foreach (var t in tasks)
1245                                 t.ContinueWith (continuation);
1246
1247                         return task;
1248                 }
1249                 #region Properties
1250
1251                 internal CancellationToken CancellationToken {
1252                         get {
1253                                 return token;
1254                         }
1255                 }
1256
1257                 public static TaskFactory Factory {
1258                         get {
1259                                 return defaultFactory;
1260                         }
1261                 }
1262
1263                 public static int? CurrentId {
1264                         get {
1265                                 Task t = current;
1266                                 return t == null ? (int?)null : t.Id;
1267                         }
1268                 }
1269
1270                 public AggregateException Exception {
1271                         get {
1272                                 if (exSlot == null || !IsFaulted)
1273                                         return null;
1274                                 exSlot.Observed = true;
1275                                 return exSlot.Exception;
1276                         }
1277                 }
1278
1279                 public bool IsCanceled {
1280                         get {
1281                                 return status == TaskStatus.Canceled;
1282                         }
1283                 }
1284
1285                 public bool IsCompleted {
1286                         get {
1287                                 return status >= TaskStatus.RanToCompletion;
1288                         }
1289                 }
1290
1291                 public bool IsFaulted {
1292                         get {
1293                                 return status == TaskStatus.Faulted;
1294                         }
1295                 }
1296
1297                 public TaskCreationOptions CreationOptions {
1298                         get {
1299                                 return creationOptions & MaxTaskCreationOptions;
1300                         }
1301                 }
1302
1303                 public TaskStatus Status {
1304                         get {
1305                                 return status;
1306                         }
1307                         internal set {
1308                                 status = value;
1309                                 Thread.MemoryBarrier ();
1310                         }
1311                 }
1312
1313                 internal TaskExceptionSlot ExceptionSlot {
1314                         get {
1315                                 if (exSlot != null)
1316                                         return exSlot;
1317                                 Interlocked.CompareExchange (ref exSlot, new TaskExceptionSlot (this), null);
1318                                 return exSlot;
1319                         }
1320                 }
1321
1322                 public object AsyncState {
1323                         get {
1324                                 return state;
1325                         }
1326                 }
1327
1328                 bool IAsyncResult.CompletedSynchronously {
1329                         get {
1330                                 return true;
1331                         }
1332                 }
1333
1334                 WaitHandle IAsyncResult.AsyncWaitHandle {
1335                         get {
1336                                 if (invoker == null)
1337                                         throw new ObjectDisposedException (GetType ().ToString ());
1338
1339                                 if (wait_handle == null)
1340                                         Interlocked.CompareExchange (ref wait_handle, new ManualResetEvent (IsCompleted), null);
1341
1342                                 return wait_handle;
1343                         }
1344                 }
1345
1346                 public int Id {
1347                         get {
1348                                 return taskId;
1349                         }
1350                 }
1351
1352                 bool IsContinuation {
1353                         get {
1354                                 return contAncestor != null;
1355                         }
1356                 }
1357
1358                 bool IsPromise {
1359                         get {
1360                                 return invoker == TaskActionInvoker.Promise;
1361                         }
1362                 }
1363
1364                 internal Task ContinuationAncestor {
1365                         get {
1366                                 return contAncestor;
1367                         }
1368                 }
1369
1370                 internal string DisplayActionMethod {
1371                         get {
1372                                 Delegate d = invoker.Action;
1373                                 return d == null ? "<none>" : d.Method.ToString ();
1374                         }
1375                 }
1376
1377                 #endregion
1378         }
1379 }
1380 #endif