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 =
  39                         Environment.GetEnvironmentVariable ("USE_OLD_TASK_SCHED") != null ? (TaskScheduler)new Scheduler () : (TaskScheduler)new TpScheduler ();
  40                 SchedulerProxy proxy;
  41
  42                 [ThreadStatic]
  43                 static TaskScheduler currentScheduler;
  44
  45                 int id;
  46                 static int lastId = int.MinValue;
  47
  48                 public static event EventHandler<UnobservedTaskExceptionEventArgs> UnobservedTaskException;
  49
  50                 protected TaskScheduler ()
  51                 {
  52                         this.id = Interlocked.Increment (ref lastId);
  53                         this.proxy = new SchedulerProxy (this);
  54                 }
  55
  56                 public static TaskScheduler FromCurrentSynchronizationContext ()
  57                 {
  58                         var syncCtx = SynchronizationContext.Current;
  59                         return new SynchronizationContextScheduler (syncCtx);
  60                 }
  61
  62                 public static TaskScheduler Default  {
  63                         get {
  64                                 return defaultScheduler;
  65                         }
  66                 }
  67
  68                 public static TaskScheduler Current  {
  69                         get {
  70                                 if (currentScheduler != null)
  71                                         return currentScheduler;
  72
  73                                 return defaultScheduler;
  74                         }
  75                         internal set {
  76                                 currentScheduler = value;
  77                         }
  78                 }
  79
  80                 public int Id {
  81                         get {
  82                                 return id;
  83                         }
  84                 }
  85
  86                 public virtual int MaximumConcurrencyLevel {
  87                         get {
  88                                 return Environment.ProcessorCount;
  89                         }
  90                 }
  91
  92                 internal virtual void ParticipateUntil (Task task)
  93                 {
  94                         proxy.ParticipateUntil (task);
  95                 }
  96
  97                 internal virtual bool ParticipateUntil (Task task, ManualResetEventSlim predicateEvt, int millisecondsTimeout)
  98                 {
  99                         return proxy.ParticipateUntil (task, predicateEvt, millisecondsTimeout);
 100                 }
 101
 102                 internal virtual void PulseAll ()
 103                 {
 104                         proxy.PulseAll ();
 105                 }
 106
 107                 protected abstract IEnumerable<Task> GetScheduledTasks ();
 108                 protected internal abstract void QueueTask (Task task);
 109                 protected internal virtual bool TryDequeue (Task task)
 110                 {
 111                         throw new NotSupportedException ();
 112                 }
 113
 114                 internal protected bool TryExecuteTask (Task task)
 115                 {
 116                         return TryExecuteTaskInline (task, false);
 117                 }
 118
 119                 protected abstract bool TryExecuteTaskInline (Task task, bool taskWasPreviouslyQueued);
 120
 121                 internal UnobservedTaskExceptionEventArgs FireUnobservedEvent (AggregateException e)
 122                 {
 123                         UnobservedTaskExceptionEventArgs args = new UnobservedTaskExceptionEventArgs (e);
 124
 125                         EventHandler<UnobservedTaskExceptionEventArgs> temp = UnobservedTaskException;
 126                         if (temp == null)
 127                                 return args;
 128
 129                         temp (this, args);
 130
 131                         return args;
 132                 }
 133         }
 134 }
 135 #endif