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