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