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

   1 //
   2 // Task.cs
   3 //
   4 // Authors:
   5 //    Marek Safar  <marek.safar@gmail.com>
   6 //
   7 // Copyright (c) 2008 Jérémie "Garuma" Laval
   8 // Copyright 2011 Xamarin Inc (http://www.xamarin.com).
   9 //
  10 // Permission is hereby granted, free of charge, to any person obtaining a copy
  11 // of this software and associated documentation files (the "Software"), to deal
  12 // in the Software without restriction, including without limitation the rights
  13 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  14 // copies of the Software, and to permit persons to whom the Software is
  15 // furnished to do so, subject to the following conditions:
  16 //
  17 // The above copyright notice and this permission notice shall be included in
  18 // all copies or substantial portions of the Software.
  19 //
  20 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  21 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  22 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  23 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  24 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  25 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  26 // THE SOFTWARE.
  27 //
  28 //
  29
  30 #if NET_4_0 || MOBILE
  31
  32 using System;
  33 using System.Threading;
  34 using System.Collections.Concurrent;
  35 using System.Collections.Generic;
  36 using System.Runtime.CompilerServices;
  37
  38 namespace System.Threading.Tasks
  39 {
  40         [System.Diagnostics.DebuggerDisplay ("Id = {Id}, Status = {Status}")]
  41         [System.Diagnostics.DebuggerTypeProxy (typeof (TaskDebuggerView))]
  42         public class Task : IDisposable, IAsyncResult
  43         {
  44                 // With this attribute each thread has its own value so that it's correct for our Schedule code
  45                 // and for Parent property.
  46                 [System.ThreadStatic]
  47                 static Task         current;
  48                 [System.ThreadStatic]
  49                 static Action<Task> childWorkAdder;
  50
  51                 Task parent;
  52
  53                 static int          id = -1;
  54                 static readonly TaskFactory defaultFactory = new TaskFactory ();
  55                 static readonly Watch watch = Watch.StartNew ();
  56
  57                 CountdownEvent childTasks;
  58
  59                 int                 taskId;
  60                 TaskCreationOptions taskCreationOptions;
  61
  62                 TaskScheduler       scheduler;
  63
  64                 ManualResetEventSlim schedWait = new ManualResetEventSlim (false);
  65
  66                 volatile AggregateException  exception;
  67                 volatile bool                exceptionObserved;
  68                 ConcurrentQueue<AggregateException> childExceptions;
  69
  70                 TaskStatus          status;
  71
  72                 Action<object> action;
  73                 Action         simpleAction;
  74                 object         state;
  75                 AtomicBooleanValue executing;
  76
  77                 TaskCompletionQueue<Task> completed;
  78                 TaskCompletionQueue<ManualResetEventSlim> registeredEvts;
  79                 // If this task is a continuation, this stuff gets filled
  80                 CompletionSlot Slot;
  81
  82                 CancellationToken token;
  83                 CancellationTokenRegistration? cancellationRegistration;
  84
  85                 internal const TaskCreationOptions WorkerTaskNotSupportedOptions = TaskCreationOptions.LongRunning | TaskCreationOptions.PreferFairness;
  86
  87                 const TaskCreationOptions MaxTaskCreationOptions =
  88 #if NET_4_5
  89                         TaskCreationOptions.DenyChildAttach | TaskCreationOptions.HideScheduler |
  90 #endif
  91                         TaskCreationOptions.PreferFairness | TaskCreationOptions.LongRunning | TaskCreationOptions.AttachedToParent;
  92
  93                 public Task (Action action) : this (action, TaskCreationOptions.None)
  94                 {
  95
  96                 }
  97
  98                 public Task (Action action, TaskCreationOptions creationOptions) : this (action, CancellationToken.None, creationOptions)
  99                 {
 100
 101                 }
 102
 103                 public Task (Action action, CancellationToken cancellationToken) : this (action, cancellationToken, TaskCreationOptions.None)
 104                 {
 105
 106                 }
 107
 108                 public Task (Action action, CancellationToken cancellationToken, TaskCreationOptions creationOptions)
 109                         : this (null, null, cancellationToken, creationOptions, current)
 110                 {
 111                         if (action == null)
 112                                 throw new ArgumentNullException ("action");
 113                         if (creationOptions > MaxTaskCreationOptions || creationOptions < TaskCreationOptions.None)
 114                                 throw new ArgumentOutOfRangeException ("creationOptions");
 115                         this.simpleAction = action;
 116                 }
 117
 118                 public Task (Action<object> action, object state) : this (action, state, TaskCreationOptions.None)
 119                 {
 120                 }
 121
 122                 public Task (Action<object> action, object state, TaskCreationOptions creationOptions)
 123                         : this (action, state, CancellationToken.None, creationOptions)
 124                 {
 125                 }
 126
 127                 public Task (Action<object> action, object state, CancellationToken cancellationToken)
 128                         : this (action, state, cancellationToken, TaskCreationOptions.None)
 129                 {
 130                 }
 131
 132                 public Task (Action<object> action, object state, CancellationToken cancellationToken, TaskCreationOptions creationOptions)
 133                         : this (action, state, cancellationToken, creationOptions, current)
 134                 {
 135                         if (action == null)
 136                                 throw new ArgumentNullException ("action");
 137                         if (creationOptions > MaxTaskCreationOptions || creationOptions < TaskCreationOptions.None)
 138                                 throw new ArgumentOutOfRangeException ("creationOptions");
 139                 }
 140
 141                 internal Task (Action<object> action,
 142                                object state,
 143                                CancellationToken cancellationToken,
 144                                TaskCreationOptions creationOptions,
 145                                Task parent)
 146                 {
 147                         this.taskCreationOptions = creationOptions;
 148                         this.action              = action;
 149                         this.state               = state;
 150                         this.taskId              = Interlocked.Increment (ref id);
 151                         this.status              = cancellationToken.IsCancellationRequested ? TaskStatus.Canceled : TaskStatus.Created;
 152                         this.token               = cancellationToken;
 153                         this.parent              = parent;
 154
 155                         // Process taskCreationOptions
 156                         if (CheckTaskOptions (taskCreationOptions, TaskCreationOptions.AttachedToParent) && parent != null)
 157                                 parent.AddChild ();
 158
 159                         if (token.CanBeCanceled)
 160                                 cancellationRegistration = token.Register (l => ((Task) l).CancelReal (), this);
 161                 }
 162
 163                 ~Task ()
 164                 {
 165                         if (exception != null && !exceptionObserved)
 166                                 throw exception;
 167                 }
 168
 169                 bool CheckTaskOptions (TaskCreationOptions opt, TaskCreationOptions member)
 170                 {
 171                         return (opt & member) == member;
 172                 }
 173
 174                 #region Start
 175                 public void Start ()
 176                 {
 177                         Start (TaskScheduler.Current);
 178                 }
 179
 180                 public void Start (TaskScheduler scheduler)
 181                 {
 182                         if (scheduler == null)
 183                                 throw new ArgumentNullException ("scheduler");
 184
 185                         if (status >= TaskStatus.WaitingToRun)
 186                                 throw new InvalidOperationException ("The Task is not in a valid state to be started.");
 187
 188                         if (Slot.Initialized)
 189                                 throw new InvalidOperationException ("Start may not be called on a continuation task");
 190
 191                         SetupScheduler (scheduler);
 192                         Schedule ();
 193                 }
 194
 195                 internal void SetupScheduler (TaskScheduler scheduler)
 196                 {
 197                         this.scheduler = scheduler;
 198                         status = TaskStatus.WaitingForActivation;
 199                         schedWait.Set ();
 200                 }
 201
 202                 public void RunSynchronously ()
 203                 {
 204                         RunSynchronously (TaskScheduler.Current);
 205                 }
 206
 207                 public void RunSynchronously (TaskScheduler scheduler)
 208                 {
 209                         if (scheduler == null)
 210                                 throw new ArgumentNullException ("scheduler");
 211
 212                         if (Status > TaskStatus.WaitingForActivation)
 213                                 throw new InvalidOperationException ("The task is not in a valid state to be started");
 214
 215                         SetupScheduler (scheduler);
 216                         var saveStatus = status;
 217                         status = TaskStatus.WaitingToRun;
 218
 219                         try {
 220                                 if (scheduler.RunInline (this))
 221                                         return;
 222                         } catch (Exception inner) {
 223                                 throw new TaskSchedulerException (inner);
 224                         }
 225
 226                         status = saveStatus;
 227                         Start (scheduler);
 228                         Wait ();
 229                 }
 230                 #endregion
 231
 232                 #region ContinueWith
 233                 public Task ContinueWith (Action<Task> continuationAction)
 234                 {
 235                         return ContinueWith (continuationAction, TaskContinuationOptions.None);
 236                 }
 237
 238                 public Task ContinueWith (Action<Task> continuationAction, TaskContinuationOptions continuationOptions)
 239                 {
 240                         return ContinueWith (continuationAction, CancellationToken.None, continuationOptions, TaskScheduler.Current);
 241                 }
 242
 243                 public Task ContinueWith (Action<Task> continuationAction, CancellationToken cancellationToken)
 244                 {
 245                         return ContinueWith (continuationAction, cancellationToken, TaskContinuationOptions.None, TaskScheduler.Current);
 246                 }
 247
 248                 public Task ContinueWith (Action<Task> continuationAction, TaskScheduler scheduler)
 249                 {
 250                         return ContinueWith (continuationAction, CancellationToken.None, TaskContinuationOptions.None, scheduler);
 251                 }
 252
 253                 public Task ContinueWith (Action<Task> continuationAction, CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
 254                 {
 255                         if (continuationAction == null)
 256                                 throw new ArgumentNullException ("continuationAction");
 257                         if (scheduler == null)
 258                                 throw new ArgumentNullException ("scheduler");
 259
 260                         Task continuation = new Task (l => continuationAction ((Task)l),
 261                                                       this,
 262                                                       cancellationToken,
 263                                                       GetCreationOptions (continuationOptions),
 264                                                       this);
 265                         ContinueWithCore (continuation, continuationOptions, scheduler);
 266
 267                         return continuation;
 268                 }
 269
 270                 public Task<TResult> ContinueWith<TResult> (Func<Task, TResult> continuationFunction)
 271                 {
 272                         return ContinueWith<TResult> (continuationFunction, TaskContinuationOptions.None);
 273                 }
 274
 275                 public Task<TResult> ContinueWith<TResult> (Func<Task, TResult> continuationFunction, TaskContinuationOptions continuationOptions)
 276                 {
 277                         return ContinueWith<TResult> (continuationFunction, CancellationToken.None, continuationOptions, TaskScheduler.Current);
 278                 }
 279
 280                 public Task<TResult> ContinueWith<TResult> (Func<Task, TResult> continuationFunction, CancellationToken cancellationToken)
 281                 {
 282                         return ContinueWith<TResult> (continuationFunction, cancellationToken, TaskContinuationOptions.None, TaskScheduler.Current);
 283                 }
 284
 285                 public Task<TResult> ContinueWith<TResult> (Func<Task, TResult> continuationFunction, TaskScheduler scheduler)
 286                 {
 287                         return ContinueWith<TResult> (continuationFunction, CancellationToken.None, TaskContinuationOptions.None, scheduler);
 288                 }
 289
 290                 public Task<TResult> ContinueWith<TResult> (Func<Task, TResult> continuationFunction, CancellationToken cancellationToken,
 291                                                             TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
 292                 {
 293                         if (continuationFunction == null)
 294                                 throw new ArgumentNullException ("continuationFunction");
 295                         if (scheduler == null)
 296                                 throw new ArgumentNullException ("scheduler");
 297
 298                         Task<TResult> t = new Task<TResult> ((o) => continuationFunction ((Task)o),
 299                                                              this,
 300                                                              cancellationToken,
 301                                                              GetCreationOptions (continuationOptions),
 302                                                              this);
 303
 304                         ContinueWithCore (t, continuationOptions, scheduler);
 305
 306                         return t;
 307                 }
 308
 309                 internal void ContinueWithCore (Task continuation, TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
 310                 {
 311                         ContinueWithCore (continuation, continuationOptions, scheduler, null);
 312                 }
 313
 314                 internal void ContinueWithCore (Task continuation, TaskContinuationOptions kind,
 315                                                 TaskScheduler scheduler, Func<bool> predicate)
 316                 {
 317                         // Already set the scheduler so that user can call Wait and that sort of stuff
 318                         continuation.scheduler = scheduler;
 319                         continuation.schedWait.Set ();
 320                         continuation.status = TaskStatus.WaitingForActivation;
 321                         continuation.Slot = new CompletionSlot (kind, predicate);
 322
 323                         if (IsCompleted) {
 324                                 CompletionExecutor (continuation);
 325                                 return;
 326                         }
 327
 328                         completed.Add (continuation);
 329
 330                         // Retry in case completion was achieved but event adding was too late
 331                         if (IsCompleted)
 332                                 CompletionExecutor (continuation);
 333                 }
 334
 335                 bool ContinuationStatusCheck (TaskContinuationOptions kind)
 336                 {
 337                         if (kind == TaskContinuationOptions.None)
 338                                 return true;
 339
 340                         int kindCode = (int)kind;
 341
 342                         if (kindCode >= ((int)TaskContinuationOptions.NotOnRanToCompletion)) {
 343                                 // Remove other options
 344                                 kind &= ~(TaskContinuationOptions.PreferFairness
 345                                           | TaskContinuationOptions.LongRunning
 346                                           | TaskContinuationOptions.AttachedToParent
 347                                           | TaskContinuationOptions.ExecuteSynchronously);
 348
 349                                 if (status == TaskStatus.Canceled) {
 350                                         if (kind == TaskContinuationOptions.NotOnCanceled)
 351                                                 return false;
 352                                         if (kind == TaskContinuationOptions.OnlyOnFaulted)
 353                                                 return false;
 354                                         if (kind == TaskContinuationOptions.OnlyOnRanToCompletion)
 355                                                 return false;
 356                                 } else if (status == TaskStatus.Faulted) {
 357                                         if (kind == TaskContinuationOptions.NotOnFaulted)
 358                                                 return false;
 359                                         if (kind == TaskContinuationOptions.OnlyOnCanceled)
 360                                                 return false;
 361                                         if (kind == TaskContinuationOptions.OnlyOnRanToCompletion)
 362                                                 return false;
 363                                 } else if (status == TaskStatus.RanToCompletion) {
 364                                         if (kind == TaskContinuationOptions.NotOnRanToCompletion)
 365                                                 return false;
 366                                         if (kind == TaskContinuationOptions.OnlyOnFaulted)
 367                                                 return false;
 368                                         if (kind == TaskContinuationOptions.OnlyOnCanceled)
 369                                                 return false;
 370                                 }
 371                         }
 372
 373                         return true;
 374                 }
 375
 376                 static internal TaskCreationOptions GetCreationOptions (TaskContinuationOptions kind)
 377                 {
 378                         TaskCreationOptions options = TaskCreationOptions.None;
 379                         if ((kind & TaskContinuationOptions.AttachedToParent) > 0)
 380                                 options |= TaskCreationOptions.AttachedToParent;
 381                         if ((kind & TaskContinuationOptions.PreferFairness) > 0)
 382                                 options |= TaskCreationOptions.PreferFairness;
 383                         if ((kind & TaskContinuationOptions.LongRunning) > 0)
 384                                 options |= TaskCreationOptions.LongRunning;
 385
 386                         return options;
 387                 }
 388
 389                 internal void RegisterWaitEvent (ManualResetEventSlim evt)
 390                 {
 391                         if (IsCompleted) {
 392                                 evt.Set ();
 393                                 return;
 394                         }
 395
 396                         registeredEvts.Add (evt);
 397                         if (IsCompleted)
 398                                 evt.Set ();
 399                 }
 400                 #endregion
 401
 402                 #region Internal and protected thingies
 403                 internal void Schedule ()
 404                 {
 405                         status = TaskStatus.WaitingToRun;
 406
 407                         // If worker is null it means it is a local one, revert to the old behavior
 408                         // If TaskScheduler.Current is not being used, the scheduler was explicitly provided, so we must use that
 409                         if (scheduler != TaskScheduler.Current || childWorkAdder == null || CheckTaskOptions (taskCreationOptions, TaskCreationOptions.PreferFairness)) {
 410                                 scheduler.QueueTask (this);
 411                         } else {
 412                                 /* Like the semantic of the ABP paper describe it, we add ourselves to the bottom
 413                                  * of our Parent Task's ThreadWorker deque. It's ok to do that since we are in
 414                                  * the correct Thread during the creation
 415                                  */
 416                                 childWorkAdder (this);
 417                         }
 418                 }
 419
 420                 void ThreadStart ()
 421                 {
 422                         /* Allow scheduler to break fairness of deque ordering without
 423                          * breaking its semantic (the task can be executed twice but the
 424                          * second time it will return immediately
 425                          */
 426                         if (!executing.TryRelaxedSet ())
 427                                 return;
 428
 429                         // Disable CancellationToken direct cancellation
 430                         if (cancellationRegistration != null) {
 431                                 cancellationRegistration.Value.Dispose ();
 432                                 cancellationRegistration = null;
 433                         }
 434                         current = this;
 435                         TaskScheduler.Current = scheduler;
 436
 437                         if (!token.IsCancellationRequested) {
 438
 439                                 status = TaskStatus.Running;
 440
 441                                 try {
 442                                         InnerInvoke ();
 443                                 } catch (OperationCanceledException oce) {
 444                                         if (token != CancellationToken.None && oce.CancellationToken == token)
 445                                                 CancelReal ();
 446                                         else
 447                                                 HandleGenericException (oce);
 448                                 } catch (Exception e) {
 449                                         HandleGenericException (e);
 450                                 }
 451                         } else {
 452                                 CancelReal ();
 453                         }
 454
 455                         Finish ();
 456                 }
 457
 458                 internal void Execute (Action<Task> childAdder)
 459                 {
 460                         childWorkAdder = childAdder;
 461                         ThreadStart ();
 462                 }
 463
 464                 internal void AddChild ()
 465                 {
 466                         if (childTasks == null)
 467                                 Interlocked.CompareExchange (ref childTasks, new CountdownEvent (1), null);
 468                         childTasks.AddCount ();
 469                 }
 470
 471                 internal void ChildCompleted (AggregateException childEx)
 472                 {
 473                         if (childEx != null) {
 474                                 if (childExceptions == null)
 475                                         Interlocked.CompareExchange (ref childExceptions, new ConcurrentQueue<AggregateException> (), null);
 476                                 childExceptions.Enqueue (childEx);
 477                         }
 478
 479                         if (childTasks.Signal () && status == TaskStatus.WaitingForChildrenToComplete) {
 480                                 status = TaskStatus.RanToCompletion;
 481                                 ProcessChildExceptions ();
 482                                 ProcessCompleteDelegates ();
 483                         }
 484                 }
 485
 486                 internal virtual void InnerInvoke ()
 487                 {
 488                         if (action == null && simpleAction != null)
 489                                 simpleAction ();
 490                         else if (action != null)
 491                                 action (state);
 492                         // Set action to null so that the GC can collect the delegate and thus
 493                         // any big object references that the user might have captured in an anonymous method
 494                         action = null;
 495                         simpleAction = null;
 496                         state = null;
 497                 }
 498
 499                 internal void Finish ()
 500                 {
 501                         // If there was children created and they all finished, we set the countdown
 502                         if (childTasks != null)
 503                                 childTasks.Signal ();
 504
 505                         // Don't override Canceled or Faulted
 506                         if (status == TaskStatus.Running) {
 507                                 if (childTasks == null || childTasks.IsSet)
 508                                         status = TaskStatus.RanToCompletion;
 509                                 else
 510                                         status = TaskStatus.WaitingForChildrenToComplete;
 511                         }
 512
 513                         if (status != TaskStatus.WaitingForChildrenToComplete)
 514                                 ProcessCompleteDelegates ();
 515
 516                         // Reset the current thingies
 517                         current = null;
 518                         TaskScheduler.Current = null;
 519
 520                         if (cancellationRegistration.HasValue)
 521                                 cancellationRegistration.Value.Dispose ();
 522
 523                         // Tell parent that we are finished
 524                         if (CheckTaskOptions (taskCreationOptions, TaskCreationOptions.AttachedToParent) && parent != null) {
 525                                 parent.ChildCompleted (this.Exception);
 526                         }
 527                 }
 528
 529                 void CompletionExecutor (Task cont)
 530                 {
 531                         if (cont.Slot.Predicate != null && !cont.Slot.Predicate ())
 532                                 return;
 533
 534                         if (!cont.Slot.Launched.TryRelaxedSet ())
 535                                 return;
 536
 537                         if (!ContinuationStatusCheck (cont.Slot.Kind)) {
 538                                 cont.CancelReal ();
 539                                 cont.Dispose ();
 540
 541                                 return;
 542                         }
 543
 544                         if ((cont.Slot.Kind & TaskContinuationOptions.ExecuteSynchronously) != 0)
 545                                 cont.RunSynchronously (cont.scheduler);
 546                         else
 547                                 cont.Schedule ();
 548                 }
 549
 550                 void ProcessCompleteDelegates ()
 551                 {
 552                         if (completed.HasElements) {
 553                                 Task continuation;
 554                                 while (completed.TryGetNextCompletion (out continuation))
 555                                         CompletionExecutor (continuation);
 556                         }
 557                         if (registeredEvts.HasElements) {
 558                                 ManualResetEventSlim evt;
 559                                 while (registeredEvts.TryGetNextCompletion (out evt))
 560                                         evt.Set ();
 561                         }
 562                 }
 563
 564                 void ProcessChildExceptions ()
 565                 {
 566                         if (childExceptions == null)
 567                                 return;
 568
 569                         if (exception == null)
 570                                 exception = new AggregateException ();
 571
 572                         AggregateException childEx;
 573                         while (childExceptions.TryDequeue (out childEx))
 574                                 exception.AddChildException (childEx);
 575                 }
 576                 #endregion
 577
 578                 #region Cancel and Wait related method
 579
 580                 internal void CancelReal ()
 581                 {
 582                         status = TaskStatus.Canceled;
 583                         ProcessCompleteDelegates ();
 584                 }
 585
 586                 internal void HandleGenericException (Exception e)
 587                 {
 588                         HandleGenericException (new AggregateException (e));
 589                 }
 590
 591                 internal void HandleGenericException (AggregateException e)
 592                 {
 593                         exception = e;
 594                         Thread.MemoryBarrier ();
 595                         status = TaskStatus.Faulted;
 596                         if (scheduler != null && scheduler.FireUnobservedEvent (exception).Observed)
 597                                 exceptionObserved = true;
 598                 }
 599
 600                 public void Wait ()
 601                 {
 602                         Wait (Timeout.Infinite, CancellationToken.None);
 603                 }
 604
 605                 public void Wait (CancellationToken cancellationToken)
 606                 {
 607                         Wait (Timeout.Infinite, cancellationToken);
 608                 }
 609
 610                 public bool Wait (TimeSpan timeout)
 611                 {
 612                         return Wait (CheckTimeout (timeout), CancellationToken.None);
 613                 }
 614
 615                 public bool Wait (int millisecondsTimeout)
 616                 {
 617                         return Wait (millisecondsTimeout, CancellationToken.None);
 618                 }
 619
 620                 public bool Wait (int millisecondsTimeout, CancellationToken cancellationToken)
 621                 {
 622                         if (millisecondsTimeout < -1)
 623                                 throw new ArgumentOutOfRangeException ("millisecondsTimeout");
 624
 625                         bool result = true;
 626
 627                         if (!IsCompleted) {
 628                                 // If the task is ready to be run and we were supposed to wait on it indefinitely, just run it
 629                                 if (Status == TaskStatus.WaitingToRun && millisecondsTimeout == -1 && scheduler != null)
 630                                         Execute (null);
 631
 632                                 if (!IsCompleted) {
 633                                         // Free heavy ressources used by the event automatically but without removing
 634                                         // it from the queue since Set () doesn't trigger ObjectDisposedException
 635                                         using (var evt = new ManualResetEventSlim ()) {
 636                                                 RegisterWaitEvent (evt);
 637                                                 result = evt.Wait (millisecondsTimeout, cancellationToken);
 638                                         }
 639                                 }
 640                         }
 641
 642                         if (IsCanceled)
 643                                 throw new AggregateException (new TaskCanceledException (this));
 644
 645                         if (exception != null)
 646                                 throw exception;
 647
 648                         return result;
 649                 }
 650
 651                 public static void WaitAll (params Task[] tasks)
 652                 {
 653                         WaitAll (tasks, Timeout.Infinite, CancellationToken.None);
 654                 }
 655
 656                 public static void WaitAll (Task[] tasks, CancellationToken cancellationToken)
 657                 {
 658                         WaitAll (tasks, Timeout.Infinite, cancellationToken);
 659                 }
 660
 661                 public static bool WaitAll (Task[] tasks, TimeSpan timeout)
 662                 {
 663                         return WaitAll (tasks, CheckTimeout (timeout), CancellationToken.None);
 664                 }
 665
 666                 public static bool WaitAll (Task[] tasks, int millisecondsTimeout)
 667                 {
 668                         return WaitAll (tasks, millisecondsTimeout, CancellationToken.None);
 669                 }
 670
 671                 public static bool WaitAll (Task[] tasks, int millisecondsTimeout, CancellationToken cancellationToken)
 672                 {
 673                         if (tasks == null)
 674                                 throw new ArgumentNullException ("tasks");
 675                         CheckForNullTasks (tasks);
 676
 677                         bool result = true;
 678                         List<Exception> exceptions = null;
 679                         long start = watch.ElapsedMilliseconds;
 680
 681                         foreach (var t in tasks) {
 682                                 try {
 683                                         result &= t.Wait (millisecondsTimeout, cancellationToken);
 684                                 } catch (AggregateException e) {
 685                                         if (exceptions == null)
 686                                                 exceptions = new List<Exception> ();
 687
 688                                         exceptions.AddRange (e.InnerExceptions);
 689                                 }
 690                                 if (!ComputeTimeout (ref millisecondsTimeout, start, watch))
 691                                         result = false;
 692                                 if (!result)
 693                                         break;
 694                         }
 695
 696                         if (exceptions != null)
 697                                 throw new AggregateException (exceptions);
 698
 699                         return result;
 700                 }
 701
 702                 public static int WaitAny (params Task[] tasks)
 703                 {
 704                         return WaitAny (tasks, Timeout.Infinite, CancellationToken.None);
 705                 }
 706
 707                 public static int WaitAny (Task[] tasks, TimeSpan timeout)
 708                 {
 709                         return WaitAny (tasks, CheckTimeout (timeout));
 710                 }
 711
 712                 public static int WaitAny (Task[] tasks, int millisecondsTimeout)
 713                 {
 714                         return WaitAny (tasks, millisecondsTimeout, CancellationToken.None);
 715                 }
 716
 717                 public static int WaitAny (Task[] tasks, CancellationToken cancellationToken)
 718                 {
 719                         return WaitAny (tasks, Timeout.Infinite, cancellationToken);
 720                 }
 721
 722                 public static int WaitAny (Task[] tasks, int millisecondsTimeout, CancellationToken cancellationToken)
 723                 {
 724                         if (tasks == null)
 725                                 throw new ArgumentNullException ("tasks");
 726                         if (millisecondsTimeout < -1)
 727                                 throw new ArgumentOutOfRangeException ("millisecondsTimeout");
 728                         CheckForNullTasks (tasks);
 729
 730                         if (tasks.Length > 0) {
 731                                 using (var evt = new ManualResetEventSlim ()) {
 732                                         for (int i = 0; i < tasks.Length; i++) {
 733                                                 var t = tasks[i];
 734                                                 if (t.IsCompleted)
 735                                                         return i;
 736                                                 t.RegisterWaitEvent (evt);
 737                                         }
 738
 739                                         if (!evt.Wait (millisecondsTimeout, cancellationToken))
 740                                                 return -1;
 741                                 }
 742                         }
 743
 744                         int firstFinished = -1;
 745                         for (int i = 0; i < tasks.Length; i++) {
 746                                 var t = tasks[i];
 747                                 if (t.IsCompleted) {
 748                                         firstFinished = i;
 749                                         break;
 750                                 }
 751                         }
 752
 753                         return firstFinished;
 754                 }
 755
 756                 static int CheckTimeout (TimeSpan timeout)
 757                 {
 758                         try {
 759                                 return checked ((int)timeout.TotalMilliseconds);
 760                         } catch (System.OverflowException) {
 761                                 throw new ArgumentOutOfRangeException ("timeout");
 762                         }
 763                 }
 764
 765                 static bool ComputeTimeout (ref int millisecondsTimeout, long start, Watch watch)
 766                 {
 767                         if (millisecondsTimeout == -1)
 768                                 return true;
 769
 770                         return (millisecondsTimeout = millisecondsTimeout - (int)(watch.ElapsedMilliseconds - start)) >= 1;
 771                 }
 772
 773                 static void CheckForNullTasks (Task[] tasks)
 774                 {
 775                         foreach (var t in tasks)
 776                                 if (t == null)
 777                                         throw new ArgumentNullException ("tasks", "the tasks argument contains a null element");
 778                 }
 779                 #endregion
 780
 781                 #region Dispose
 782                 public void Dispose ()
 783                 {
 784                         Dispose (true);
 785                 }
 786
 787                 protected virtual void Dispose (bool disposing)
 788                 {
 789                         if (!IsCompleted)
 790                                 throw new InvalidOperationException ("A task may only be disposed if it is in a completion state");
 791
 792                         // Set action to null so that the GC can collect the delegate and thus
 793                         // any big object references that the user might have captured in a anonymous method
 794                         if (disposing) {
 795                                 action = null;
 796                                 state = null;
 797                                 if (cancellationRegistration != null)
 798                                         cancellationRegistration.Value.Dispose ();
 799                         }
 800                 }
 801                 #endregion
 802
 803 #if NET_4_5
 804
 805                 public ConfiguredTaskAwaitable ConfigureAwait (bool continueOnCapturedContext)
 806                 {
 807                         return new ConfiguredTaskAwaitable (this, continueOnCapturedContext);
 808                 }
 809
 810                 public Task ContinueWith (Action<Task, object> continuationAction, object state)
 811                 {
 812                         return ContinueWith (continuationAction, state, CancellationToken.None, TaskContinuationOptions.None, TaskScheduler.Current);
 813                 }
 814
 815                 public Task ContinueWith (Action<Task, object> continuationAction, object state, CancellationToken cancellationToken)
 816                 {
 817                         return ContinueWith (continuationAction, state, cancellationToken, TaskContinuationOptions.None, TaskScheduler.Current);
 818                 }
 819
 820                 public Task ContinueWith (Action<Task, object> continuationAction, object state, TaskContinuationOptions continuationOptions)
 821                 {
 822                         return ContinueWith (continuationAction, state, CancellationToken.None, continuationOptions, TaskScheduler.Current);
 823                 }
 824
 825                 public Task ContinueWith (Action<Task, object> continuationAction, object state, TaskScheduler scheduler)
 826                 {
 827                         return ContinueWith (continuationAction, state, CancellationToken.None, TaskContinuationOptions.None, scheduler);
 828                 }
 829
 830                 public Task ContinueWith (Action<Task, object> continuationAction, object state, CancellationToken cancellationToken,
 831                                                                   TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
 832                 {
 833                         if (continuationAction == null)
 834                                 throw new ArgumentNullException ("continuationAction");
 835                         if (scheduler == null)
 836                                 throw new ArgumentNullException ("scheduler");
 837
 838                         Task continuation = new Task (l => continuationAction (this, l), state,
 839                                                                                   cancellationToken,
 840                                                                                   GetCreationOptions (continuationOptions),
 841                                                                                   this);
 842                         ContinueWithCore (continuation, continuationOptions, scheduler);
 843
 844                         return continuation;
 845                 }
 846
 847                 public Task<TResult> ContinueWith<TResult> (Func<Task, object, TResult> continuationFunction, object state)
 848                 {
 849                         return ContinueWith<TResult> (continuationFunction, state, CancellationToken.None, TaskContinuationOptions.None, TaskScheduler.Current);
 850                 }
 851
 852                 public Task<TResult> ContinueWith<TResult> (Func<Task, object, TResult> continuationFunction, object state, TaskContinuationOptions continuationOptions)
 853                 {
 854                         return ContinueWith<TResult> (continuationFunction, state, CancellationToken.None, continuationOptions, TaskScheduler.Current);
 855                 }
 856
 857                 public Task<TResult> ContinueWith<TResult> (Func<Task, object, TResult> continuationFunction, object state, CancellationToken cancellationToken)
 858                 {
 859                         return ContinueWith<TResult> (continuationFunction, state, cancellationToken, TaskContinuationOptions.None, TaskScheduler.Current);
 860                 }
 861
 862                 public Task<TResult> ContinueWith<TResult> (Func<Task, object, TResult> continuationFunction, object state, TaskScheduler scheduler)
 863                 {
 864                         return ContinueWith<TResult> (continuationFunction, state, CancellationToken.None, TaskContinuationOptions.None, scheduler);
 865                 }
 866
 867                 public Task<TResult> ContinueWith<TResult> (Func<Task, object, TResult> continuationFunction, object state, CancellationToken cancellationToken,
 868                                                                                                         TaskContinuationOptions continuationOptions, TaskScheduler scheduler)
 869                 {
 870                         if (continuationFunction == null)
 871                                 throw new ArgumentNullException ("continuationFunction");
 872                         if (scheduler == null)
 873                                 throw new ArgumentNullException ("scheduler");
 874
 875                         var t = new Task<TResult> (l => continuationFunction (this, l),
 876                                                                                                  state,
 877                                                                                                  cancellationToken,
 878                                                                                                  GetCreationOptions (continuationOptions),
 879                                                                                                  this);
 880
 881                         ContinueWithCore (t, continuationOptions, scheduler);
 882
 883                         return t;
 884                 }
 885
 886                 public static Task<TResult> FromResult<TResult> (TResult result)
 887                 {
 888                         var tcs = new TaskCompletionSource<TResult> ();
 889                         tcs.SetResult (result);
 890                         return tcs.Task;
 891                 }
 892
 893                 public TaskAwaiter GetAwaiter ()
 894                 {
 895                         return new TaskAwaiter (this);
 896                 }
 897
 898                 public static Task Run (Action action)
 899                 {
 900                         return Run (action, CancellationToken.None);
 901                 }
 902
 903                 public static Task Run (Action action, CancellationToken cancellationToken)
 904                 {
 905                         if (cancellationToken.IsCancellationRequested)
 906                                 return TaskConstants.Canceled;
 907
 908                         var t = new Task (action, cancellationToken, TaskCreationOptions.DenyChildAttach);
 909                         t.Start ();
 910                         return t;
 911                 }
 912
 913                 public static Task Run (Func<Task> function)
 914                 {
 915                         return Run (function, CancellationToken.None);
 916                 }
 917
 918                 public static Task Run (Func<Task> function, CancellationToken cancellationToken)
 919                 {
 920                         if (cancellationToken.IsCancellationRequested)
 921                                 return TaskConstants.Canceled;
 922
 923                         var t = new Task<Task> (function, cancellationToken);
 924                         t.Start ();
 925                         return t;
 926                 }
 927
 928                 public static Task<TResult> Run<TResult> (Func<TResult> function)
 929                 {
 930                         return Run (function, CancellationToken.None);
 931                 }
 932
 933                 public static Task<TResult> Run<TResult> (Func<TResult> function, CancellationToken cancellationToken)
 934                 {
 935                         if (cancellationToken.IsCancellationRequested)
 936                                 return TaskConstants<TResult>.Canceled;
 937
 938                         var t = new Task<TResult> (function, cancellationToken, TaskCreationOptions.DenyChildAttach);
 939                         t.Start ();
 940                         return t;
 941                 }
 942
 943                 public static Task<TResult> Run<TResult> (Func<Task<TResult>> function)
 944                 {
 945                         return Run (function, CancellationToken.None);
 946                 }
 947
 948                 public static Task<TResult> Run<TResult> (Func<Task<TResult>> function, CancellationToken cancellationToken)
 949                 {
 950                         if (cancellationToken.IsCancellationRequested)
 951                                 return TaskConstants<TResult>.Canceled;
 952
 953                         var t = Task<Task<TResult>>.Factory.StartNew (function, cancellationToken, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default);
 954                         return GetTaskResult (t);
 955                 }
 956
 957                 async static Task<TResult> GetTaskResult<TResult> (Task<Task<TResult>> task)
 958                 {
 959                         var r = await task.ConfigureAwait (false);
 960                         return r.Result;
 961                 }
 962
 963                 public static YieldAwaitable Yield ()
 964                 {
 965                         return new YieldAwaitable ();
 966                 }
 967 #endif
 968
 969                 #region Properties
 970                 public static TaskFactory Factory {
 971                         get {
 972                                 return defaultFactory;
 973                         }
 974                 }
 975
 976                 public static int? CurrentId {
 977                         get {
 978                                 Task t = current;
 979                                 return t == null ? (int?)null : t.Id;
 980                         }
 981                 }
 982
 983                 public AggregateException Exception {
 984                         get {
 985                                 exceptionObserved = true;
 986
 987                                 return exception;
 988                         }
 989                         internal set {
 990                                 exception = value;
 991                         }
 992                 }
 993
 994                 public bool IsCanceled {
 995                         get {
 996                                 return status == TaskStatus.Canceled;
 997                         }
 998                 }
 999
1000                 public bool IsCompleted {
1001                         get {
1002                                 return status >= TaskStatus.RanToCompletion;
1003                         }
1004                 }
1005
1006                 public bool IsFaulted {
1007                         get {
1008                                 return status == TaskStatus.Faulted;
1009                         }
1010                 }
1011
1012                 public TaskCreationOptions CreationOptions {
1013                         get {
1014                                 return taskCreationOptions;
1015                         }
1016                 }
1017
1018                 public TaskStatus Status {
1019                         get {
1020                                 return status;
1021                         }
1022                         internal set {
1023                                 status = value;
1024                         }
1025                 }
1026
1027                 public object AsyncState {
1028                         get {
1029                                 return state;
1030                         }
1031                 }
1032
1033                 bool IAsyncResult.CompletedSynchronously {
1034                         get {
1035                                 return true;
1036                         }
1037                 }
1038
1039                 WaitHandle IAsyncResult.AsyncWaitHandle {
1040                         get {
1041                                 return null;
1042                         }
1043                 }
1044
1045                 public int Id {
1046                         get {
1047                                 return taskId;
1048                         }
1049                 }
1050
1051                 internal Task Parent {
1052                         get {
1053                                 return parent;
1054                         }
1055                 }
1056
1057                 internal string DisplayActionMethod {
1058                         get {
1059                                 Delegate d = simpleAction ?? (Delegate) action;
1060                                 return d == null ? "<none>" : d.Method.ToString ();
1061                         }
1062                 }
1063
1064                 #endregion
1065         }
1066 }
1067 #endif