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

   1 // ThreadWorker.cs
   2 //
   3 // Copyright (c) 2008 Jérémie "Garuma" Laval
   4 //
   5 // Permission is hereby granted, free of charge, to any person obtaining a copy
   6 // of this software and associated documentation files (the "Software"), to deal
   7 // in the Software without restriction, including without limitation the rights
   8 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   9 // copies of the Software, and to permit persons to whom the Software is
  10 // furnished to do so, subject to the following conditions:
  11 //
  12 // The above copyright notice and this permission notice shall be included in
  13 // all copies or substantial portions of the Software.
  14 //
  15 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  18 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  21 // THE SOFTWARE.
  22 //
  23 //
  24
  25 #if NET_4_0 || BOOTSTRAP_NET_4_0
  26 using System;
  27 using System.Threading;
  28 using System.Collections.Concurrent;
  29
  30 namespace System.Threading.Tasks
  31 {
  32         internal class ThreadWorker : IDisposable
  33         {
  34                 Thread workerThread;
  35
  36                 readonly IDequeOperations<Task> dDeque;
  37                 readonly ThreadWorker[]         others;
  38                 readonly EventWaitHandle        waitHandle;
  39                 readonly IProducerConsumerCollection<Task> sharedWorkQueue;
  40                 readonly IScheduler             sched;
  41                 readonly ThreadPriority         threadPriority;
  42
  43                 // Flag to tell if workerThread is running
  44                 int started = 0;
  45
  46                 readonly int  workerLength;
  47                 readonly int  workerPosition;
  48                 const    int  maxRetry = 5;
  49
  50                 const int sleepThreshold = 100;
  51                 const int deepSleepTime = 10;
  52
  53                 public ThreadWorker (IScheduler sched,
  54                                      ThreadWorker[] others,
  55                                      int workerPosition,
  56                                      IProducerConsumerCollection<Task> sharedWorkQueue,
  57                                      ThreadPriority priority,
  58                                      EventWaitHandle handle)
  59                 {
  60                         this.others          = others;
  61                         this.dDeque          = new CyclicDeque<Task> ();
  62                         this.sched           = sched;
  63                         this.sharedWorkQueue = sharedWorkQueue;
  64                         this.workerLength    = others.Length;
  65                         this.workerPosition  = workerPosition;
  66                         this.waitHandle      = handle;
  67                         this.threadPriority  = priority;
  68
  69                         InitializeUnderlyingThread ();
  70                 }
  71
  72                 void InitializeUnderlyingThread ()
  73                 {
  74                         this.workerThread = new Thread (WorkerMethodWrapper);
  75
  76                         this.workerThread.IsBackground = true;
  77                         this.workerThread.Priority = threadPriority;
  78                         this.workerThread.Name = "ParallelFxThreadWorker";
  79                 }
  80
  81                 public void Dispose ()
  82                 {
  83                         Stop ();
  84                         if (workerThread.ThreadState != ThreadState.Stopped)
  85                                 workerThread.Abort ();
  86                 }
  87
  88                 public void Pulse ()
  89                 {
  90                         if (started == 1)
  91                                 return;
  92
  93                         // If the thread was stopped then set it in use and restart it
  94                         int result = Interlocked.Exchange (ref started, 1);
  95                         if (result != 0)
  96                                 return;
  97
  98                         if (this.workerThread.ThreadState != ThreadState.Unstarted) {
  99                                 InitializeUnderlyingThread ();
 100                         }
 101
 102                         workerThread.Start ();
 103                 }
 104
 105                 public void Stop ()
 106                 {
 107                         // Set the flag to stop so that the while in the thread will stop
 108                         // doing its infinite loop.
 109                         started = 0;
 110                 }
 111
 112                 // This is the actual method called in the Thread
 113                 void WorkerMethodWrapper ()
 114                 {
 115                         int sleepTime = 0;
 116                         SpinWait wait = new SpinWait ();
 117
 118                         // Main loop
 119                         while (started == 1) {
 120                                 bool result = false;
 121
 122                                 result = WorkerMethod ();
 123
 124                                 if (result) {
 125                                         sleepTime = 0;
 126                                         wait = new SpinWait ();
 127                                 }
 128
 129                                 // Wait a little and if the Thread has been more sleeping than working shut it down
 130                                 wait.SpinOnce ();
 131
 132                                 // If we are spinning too much, have a deeper sleep
 133                                 if (sleepTime++ > sleepThreshold)
 134                                         waitHandle.WaitOne (deepSleepTime);
 135                         }
 136
 137                         started = 0;
 138                 }
 139
 140                 // Main method, used to do all the logic of retrieving, processing and stealing work.
 141                 bool WorkerMethod ()
 142                 {
 143                         bool result = false;
 144                         bool hasStolenFromOther;
 145                         do {
 146                                 hasStolenFromOther = false;
 147
 148                                 Task value;
 149
 150                                 // We fill up our work deque concurrently with other ThreadWorker
 151                                 while (sharedWorkQueue.Count > 0) {
 152                                         while (sharedWorkQueue.TryTake (out value)) {
 153                                                 dDeque.PushBottom (value);
 154                                         }
 155
 156                                         // Now we process our work
 157                                         while (dDeque.PopBottom (out value) == PopResult.Succeed) {
 158                                                 if (value != null) {
 159                                                         value.Execute (ChildWorkAdder);
 160                                                         result = true;
 161                                                 }
 162                                         }
 163                                 }
 164
 165                                 // When we have finished, steal from other worker
 166                                 ThreadWorker other;
 167
 168                                 // Repeat the operation a little so that we can let other things process.
 169                                 for (int j = 0; j < maxRetry; ++j) {
 170                                         int len = workerLength + workerPosition;
 171                                         // Start stealing with the ThreadWorker at our right to minimize contention
 172                                         for (int it = workerPosition + 1; it < len; ++it) {
 173                                                 int i = it % workerLength;
 174                                                 if ((other = others [i]) == null || other == this)
 175                                                         continue;
 176
 177                                                 // Maybe make this steal more than one item at a time, see TODO.
 178                                                 if (other.dDeque.PopTop (out value) == PopResult.Succeed) {
 179                                                         hasStolenFromOther = true;
 180                                                         if (value != null) {
 181                                                                 value.Execute (ChildWorkAdder);
 182                                                                 result = true;
 183                                                         }
 184                                                 }
 185                                         }
 186                                 }
 187                         } while (sharedWorkQueue.Count > 0 || hasStolenFromOther);
 188
 189                         return result;
 190                 }
 191
 192                 // Almost same as above but with an added predicate and treating one item at a time.
 193                 // It's used by Scheduler Participate(...) method for special waiting case like
 194                 // Task.WaitAll(someTasks) or Task.WaitAny(someTasks)
 195                 // Predicate should be really fast and not blocking as it is called a good deal of time
 196                 // Also, the method skip tasks that are LongRunning to avoid blocking (Task are not LongRunning by default)
 197                 public static void WorkerMethod (Func<bool> predicate, IProducerConsumerCollection<Task> sharedWorkQueue,
 198                                                  ThreadWorker[] others)
 199                 {
 200                         SpinWait wait = new SpinWait ();
 201
 202                         while (!predicate ()) {
 203                                 Task value;
 204
 205                                 // Dequeue only one item as we have restriction
 206                                 if (sharedWorkQueue.TryTake (out value)) {
 207                                         if (value != null) {
 208                                                 if (CheckTaskFitness (value))
 209                                                         value.Execute (null);
 210                                                 else
 211                                                         sharedWorkQueue.TryAdd (value);
 212                                         }
 213                                 }
 214
 215                                 // First check to see if we comply to predicate
 216                                 if (predicate ())
 217                                         return;
 218
 219                                 // Try to complete other work by stealing since our desired tasks may be in other worker
 220                                 ThreadWorker other;
 221                                 for (int i = 0; i < others.Length; i++) {
 222                                         if ((other = others [i]) == null)
 223                                                 continue;
 224
 225                                         if (other.dDeque.PopTop (out value) == PopResult.Succeed) {
 226                                                 if (value != null) {
 227                                                         if (CheckTaskFitness (value))
 228                                                                 value.Execute (null);
 229                                                         else
 230                                                                 sharedWorkQueue.TryAdd (value);
 231                                                 }
 232                                         }
 233
 234                                         if (predicate ())
 235                                                 return;
 236                                 }
 237
 238                                 wait.SpinOnce ();
 239                         }
 240                 }
 241
 242                 internal void ChildWorkAdder (Task t)
 243                 {
 244                         dDeque.PushBottom (t);
 245                         sched.PulseAll ();
 246                 }
 247
 248                 static bool CheckTaskFitness (Task t)
 249                 {
 250                         return (t.CreationOptions | TaskCreationOptions.LongRunning) > 0;
 251                 }
 252
 253                 public bool Finished {
 254                         get {
 255                                 return started == 0;
 256                         }
 257                 }
 258
 259                 public int Id {
 260                         get {
 261                                 return workerThread.ManagedThreadId;
 262                         }
 263                 }
 264
 265                 public bool Equals (ThreadWorker other)
 266                 {
 267                         return (other == null) ? false : object.ReferenceEquals (this.dDeque, other.dDeque);
 268                 }
 269
 270                 public override bool Equals (object obj)
 271                 {
 272                         ThreadWorker temp = obj as ThreadWorker;
 273                         return temp == null ? false : Equals (temp);
 274                 }
 275
 276                 public override int GetHashCode ()
 277                 {
 278                         return workerThread.ManagedThreadId.GetHashCode ();
 279                 }
 280         }
 281 }
 282 #endif