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

   1 //
   2 // TaskScheduler.cs
   3 //
   4 // Author:
   5 //       Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
   6 //
   7 // Copyright (c) 2009 Jérémie "Garuma" Laval
   8 //
   9 // Permission is hereby granted, free of charge, to any person obtaining a copy
  10 // of this software and associated documentation files (the "Software"), to deal
  11 // in the Software without restriction, including without limitation the rights
  12 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  13 // copies of the Software, and to permit persons to whom the Software is
  14 // furnished to do so, subject to the following conditions:
  15 //
  16 // The above copyright notice and this permission notice shall be included in
  17 // all copies or substantial portions of the Software.
  18 //
  19 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  22 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  23 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  24 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  25 // THE SOFTWARE.
  26
  27 #if NET_4_0 || MOBILE
  28 using System;
  29 using System.Threading;
  30 using System.Collections.Generic;
  31
  32 namespace System.Threading.Tasks
  33 {
  34         [System.Diagnostics.DebuggerDisplay ("Id={Id}")]
  35         [System.Diagnostics.DebuggerTypeProxy ("System.Threading.Tasks.TaskScheduler+SystemThreadingTasks_TaskSchedulerDebugView")]
  36         public abstract class TaskScheduler
  37         {
  38                 static TaskScheduler defaultScheduler = new TpScheduler ();
  39
  40                 [ThreadStatic]
  41                 static TaskScheduler currentScheduler;
  42
  43                 int id;
  44                 static int lastId = int.MinValue;
  45
  46                 public static event EventHandler<UnobservedTaskExceptionEventArgs> UnobservedTaskException;
  47
  48                 protected TaskScheduler ()
  49                 {
  50                         this.id = Interlocked.Increment (ref lastId);
  51                 }
  52
  53                 ~TaskScheduler ()
  54                 {
  55                 }
  56
  57                 public static TaskScheduler FromCurrentSynchronizationContext ()
  58                 {
  59                         var syncCtx = SynchronizationContext.Current;
  60                         return new SynchronizationContextScheduler (syncCtx);
  61                 }
  62
  63                 public static TaskScheduler Default  {
  64                         get {
  65                                 return defaultScheduler;
  66                         }
  67                 }
  68
  69                 public static TaskScheduler Current  {
  70                         get {
  71                                 if (currentScheduler != null)
  72                                         return currentScheduler;
  73
  74                                 return defaultScheduler;
  75                         }
  76                         internal set {
  77                                 currentScheduler = value;
  78                         }
  79                 }
  80
  81                 public int Id {
  82                         get {
  83                                 return id;
  84                         }
  85                 }
  86
  87                 public virtual int MaximumConcurrencyLevel {
  88                         get {
  89                                 return Environment.ProcessorCount;
  90                         }
  91                 }
  92
  93                 protected abstract IEnumerable<Task> GetScheduledTasks ();
  94                 protected internal abstract void QueueTask (Task task);
  95                 protected internal virtual bool TryDequeue (Task task)
  96                 {
  97                         throw new NotSupportedException ();
  98                 }
  99
 100                 internal protected bool TryExecuteTask (Task task)
 101                 {
 102                         if (task.IsCompleted)
 103                                 return false;
 104
 105                         if (task.Status == TaskStatus.WaitingToRun) {
 106                                 task.Execute (null);
 107                                 return true;
 108                         }
 109
 110                         return false;
 111                 }
 112
 113                 protected abstract bool TryExecuteTaskInline (Task task, bool taskWasPreviouslyQueued);
 114
 115                 internal bool RunInline (Task task)
 116                 {
 117                         if (!TryExecuteTaskInline (task, false))
 118                                 return false;
 119
 120                         if (!task.IsCompleted)
 121                                 throw new InvalidOperationException ("The TryExecuteTaskInline call to the underlying scheduler succeeded, but the task body was not invoked");
 122                         return true;
 123                 }
 124
 125                 internal UnobservedTaskExceptionEventArgs FireUnobservedEvent (AggregateException e)
 126                 {
 127                         UnobservedTaskExceptionEventArgs args = new UnobservedTaskExceptionEventArgs (e);
 128
 129                         EventHandler<UnobservedTaskExceptionEventArgs> temp = UnobservedTaskException;
 130                         if (temp == null)
 131                                 return args;
 132
 133                         temp (this, args);
 134
 135                         return args;
 136                 }
 137         }
 138 }
 139 #endif