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