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                 SchedulerProxy proxy;
  40
  41                 [ThreadStatic]
  42                 static TaskScheduler currentScheduler;
  43
  44                 int id;
  45                 static int lastId = int.MinValue;
  46
  47                 public static event EventHandler<UnobservedTaskExceptionEventArgs> UnobservedTaskException;
  48
  49                 protected TaskScheduler ()
  50                 {
  51                         this.id = Interlocked.Increment (ref lastId);
  52                         this.proxy = new SchedulerProxy (this);
  53                 }
  54
  55                 ~TaskScheduler ()
  56                 {
  57                 }
  58
  59                 public static TaskScheduler FromCurrentSynchronizationContext ()
  60                 {
  61                         var syncCtx = SynchronizationContext.Current;
  62                         return new SynchronizationContextScheduler (syncCtx);
  63                 }
  64
  65                 public static TaskScheduler Default  {
  66                         get {
  67                                 return defaultScheduler;
  68                         }
  69                 }
  70
  71                 public static TaskScheduler Current  {
  72                         get {
  73                                 if (currentScheduler != null)
  74                                         return currentScheduler;
  75
  76                                 return defaultScheduler;
  77                         }
  78                         internal set {
  79                                 currentScheduler = value;
  80                         }
  81                 }
  82
  83                 public int Id {
  84                         get {
  85                                 return id;
  86                         }
  87                 }
  88
  89                 public virtual int MaximumConcurrencyLevel {
  90                         get {
  91                                 return Environment.ProcessorCount;
  92                         }
  93                 }
  94
  95                 internal virtual void ParticipateUntil (Task task)
  96                 {
  97                         proxy.ParticipateUntil (task);
  98                 }
  99
 100                 internal virtual bool ParticipateUntil (Task task, ManualResetEventSlim predicateEvt, int millisecondsTimeout)
 101                 {
 102                         return proxy.ParticipateUntil (task, predicateEvt, millisecondsTimeout);
 103                 }
 104
 105                 internal virtual void PulseAll ()
 106                 {
 107                         proxy.PulseAll ();
 108                 }
 109
 110                 protected abstract IEnumerable<Task> GetScheduledTasks ();
 111                 protected internal abstract void QueueTask (Task task);
 112                 protected internal virtual bool TryDequeue (Task task)
 113                 {
 114                         throw new NotSupportedException ();
 115                 }
 116
 117                 internal protected bool TryExecuteTask (Task task)
 118                 {
 119                         if (task.IsCompleted)
 120                                 return false;
 121
 122                         if (task.Status == TaskStatus.WaitingToRun) {
 123                                 task.Execute (null);
 124                                 return true;
 125                         }
 126
 127                         return false;
 128                 }
 129
 130                 protected abstract bool TryExecuteTaskInline (Task task, bool taskWasPreviouslyQueued);
 131
 132                 internal bool RunInline (Task task)
 133                 {
 134                         if (!TryExecuteTaskInline (task, false))
 135                                 return false;
 136
 137                         if (!task.IsCompleted)
 138                                 throw new InvalidOperationException ("The TryExecuteTaskInline call to the underlying scheduler succeeded, but the task body was not invoked");
 139                         return true;
 140                 }
 141
 142                 internal UnobservedTaskExceptionEventArgs FireUnobservedEvent (AggregateException e)
 143                 {
 144                         UnobservedTaskExceptionEventArgs args = new UnobservedTaskExceptionEventArgs (e);
 145
 146                         EventHandler<UnobservedTaskExceptionEventArgs> temp = UnobservedTaskException;
 147                         if (temp == null)
 148                                 return args;
 149
 150                         temp (this, args);
 151
 152                         return args;
 153                 }
 154         }
 155 }
 156 #endif