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

   1 #if NET_4_0 || BOOTSTRAP_NET_4_0
   2 // ThreadWorker.cs
   3 //
   4 // Copyright (c) 2008 Jérémie "Garuma" Laval
   5 //
   6 // Permission is hereby granted, free of charge, to any person obtaining a copy
   7 // of this software and associated documentation files (the "Software"), to deal
   8 // in the Software without restriction, including without limitation the rights
   9 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10 // copies of the Software, and to permit persons to whom the Software is
  11 // furnished to do so, subject to the following conditions:
  12 //
  13 // The above copyright notice and this permission notice shall be included in
  14 // all copies or substantial portions of the Software.
  15 //
  16 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22 // THE SOFTWARE.
  23 //
  24 //
  25
  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                 static Random r = new Random ();
  35
  36                 Thread workerThread;
  37
  38                 readonly          ThreadWorker[]        others;
  39                 internal readonly IDequeOperations<Task>    dDeque;
  40                 readonly          IProducerConsumerCollection<Task> sharedWorkQueue;
  41                 readonly          Action<Task>          childWorkAdder;
  42
  43                 // Flag to tell if workerThread is running
  44                 int started = 0;
  45
  46                 readonly bool isLocal;
  47                 readonly int  workerLength;
  48                 readonly int  stealingStart;
  49                 const    int  maxRetry = 5;
  50
  51                 const int sleepThreshold = 100000;
  52
  53                 Action threadInitializer;
  54
  55                 public ThreadWorker (IScheduler sched, ThreadWorker[] others, IProducerConsumerCollection<Task> sharedWorkQueue,
  56                                      int maxStackSize, ThreadPriority priority)
  57                         : this (sched, others, sharedWorkQueue, true, maxStackSize, priority)
  58                 {
  59                 }
  60
  61                 public ThreadWorker (IScheduler sched, ThreadWorker[] others, IProducerConsumerCollection<Task> sharedWorkQueue,
  62                                      bool createThread, int maxStackSize, ThreadPriority priority)
  63                 {
  64                         this.others          = others;
  65
  66                         this.dDeque = new CyclicDeque<Task> ();
  67
  68                         this.sharedWorkQueue = sharedWorkQueue;
  69                         this.workerLength    = others.Length;
  70                         this.isLocal         = !createThread;
  71
  72                         this.childWorkAdder = delegate (Task t) {
  73                                 dDeque.PushBottom (t);
  74                                 sched.PulseAll ();
  75                         };
  76
  77                         // Find the stealing start index randomly (then the traversal
  78                         // will be done in Round-Robin fashion)
  79                         do {
  80                                 this.stealingStart = r.Next(0, workerLength);
  81                         } while (others[stealingStart] == this);
  82
  83                         InitializeUnderlyingThread (maxStackSize, priority);
  84                 }
  85
  86                 void InitializeUnderlyingThread (int maxStackSize, ThreadPriority priority)
  87                 {
  88                         threadInitializer = delegate {
  89                                 // Special case of the participant ThreadWorker
  90                                 if (isLocal) {
  91                                         this.workerThread = Thread.CurrentThread;
  92                                         return;
  93                                 }
  94
  95                                 this.workerThread = (maxStackSize == 0) ? new Thread (WorkerMethodWrapper) :
  96                                         new Thread (WorkerMethodWrapper, maxStackSize);
  97
  98                                 this.workerThread.IsBackground = true;
  99                                 this.workerThread.Priority = priority;
 100                                 this.workerThread.Name = "ParallelFxThreadWorker";
 101                         };
 102                         threadInitializer ();
 103                 }
 104
 105                 public void Dispose ()
 106                 {
 107                         Stop ();
 108                         if (!isLocal && workerThread.ThreadState != ThreadState.Stopped)
 109                                 workerThread.Abort ();
 110                 }
 111
 112                 public void Pulse ()
 113                 {
 114                         // If the thread was stopped then set it in use and restart it
 115                         int result = Interlocked.Exchange (ref started, 1);
 116                         if (result != 0)
 117                                 return;
 118                         if (!isLocal) {
 119                                 if (this.workerThread.ThreadState != ThreadState.Unstarted) {
 120                                         threadInitializer ();
 121                                 }
 122                                 workerThread.Start ();
 123                         }
 124                 }
 125
 126                 public void Stop ()
 127                 {
 128                         // Set the flag to stop so that the while in the thread will stop
 129                         // doing its infinite loop.
 130                         started = 0;
 131                 }
 132
 133                 // This is the actual method called in the Thread
 134                 void WorkerMethodWrapper ()
 135                 {
 136                         int sleepTime = 0;
 137                         SpinWait wait = new SpinWait ();
 138
 139                         // Main loop
 140                         while (started == 1) {
 141                                 bool result = false;
 142
 143                                 result = WorkerMethod ();
 144
 145                                 // Wait a little and if the Thread has been more sleeping than working shut it down
 146                                 wait.SpinOnce ();
 147                                 if (result)
 148                                         sleepTime = 0;
 149                                 if (sleepTime++ > sleepThreshold)
 150                                         break;
 151                         }
 152
 153                         started = 0;
 154                 }
 155
 156                 // Main method, used to do all the logic of retrieving, processing and stealing work.
 157                 bool WorkerMethod ()
 158                 {
 159                         bool result = false;
 160                         bool hasStolenFromOther;
 161                         do {
 162                                 hasStolenFromOther = false;
 163
 164                                 Task value;
 165
 166                                 // We fill up our work deque concurrently with other ThreadWorker
 167                                 while (sharedWorkQueue.Count > 0) {
 168                                         while (sharedWorkQueue.TryTake (out value)) {
 169                                                 dDeque.PushBottom (value);
 170                                         }
 171
 172                                         // Now we process our work
 173                                         while (dDeque.PopBottom (out value) == PopResult.Succeed) {
 174                                                 if (value != null) {
 175                                                         value.Execute (childWorkAdder);
 176                                                         result = true;
 177                                                 }
 178                                         }
 179                                 }
 180
 181                                 // When we have finished, steal from other worker
 182                                 ThreadWorker other;
 183
 184                                 // Repeat the operation a little so that we can let other things process.
 185                                 for (int j = 0; j < maxRetry; j++) {
 186                                         // Start stealing with the ThreadWorker at our right to minimize contention
 187                                         for (int it = stealingStart; it < stealingStart + workerLength; it++) {
 188                                                 int i = it % workerLength;
 189                                                 if ((other = others [i]) == null || other == this)
 190                                                         continue;
 191
 192                                                 // Maybe make this steal more than one item at a time, see TODO.
 193                                                 if (other.dDeque.PopTop (out value) == PopResult.Succeed) {
 194                                                         hasStolenFromOther = true;
 195                                                         if (value != null) {
 196                                                                 value.Execute (childWorkAdder);
 197                                                                 result = true;
 198                                                         }
 199                                                 }
 200                                         }
 201                                 }
 202                         } while (sharedWorkQueue.Count > 0 || hasStolenFromOther);
 203
 204                         return result;
 205                 }
 206
 207                 // Almost same as above but with an added predicate and treating one item at a time.
 208                 // It's used by Scheduler Participate(...) method for special waiting case like
 209                 // Task.WaitAll(someTasks) or Task.WaitAny(someTasks)
 210                 // Predicate should be really fast and not blocking as it is called a good deal of time
 211                 // Also, the method skip tasks that are LongRunning to avoid blocking (Task are not LongRunning by default)
 212                 public static void WorkerMethod (Func<bool> predicate, IProducerConsumerCollection<Task> sharedWorkQueue,
 213                                                  ThreadWorker[] others)
 214                 {
 215                         while (!predicate ()) {
 216                                 Task value;
 217
 218                                 // Dequeue only one item as we have restriction
 219                                 if (sharedWorkQueue.TryTake (out value)) {
 220                                         if (value != null) {
 221                                                 if (CheckTaskFitness (value))
 222                                                         value.Execute (null);
 223                                                 else
 224                                                         sharedWorkQueue.TryAdd (value);
 225                                         }
 226                                 }
 227
 228                                 // First check to see if we comply to predicate
 229                                 if (predicate ()) {
 230                                         return;
 231                                 }
 232
 233                                 // Try to complete other work by stealing since our desired tasks may be in other worker
 234                                 ThreadWorker other;
 235                                 for (int i = 0; i < others.Length; i++) {
 236                                         if ((other = others [i]) == null)
 237                                                 continue;
 238
 239                                         if (other.dDeque.PopTop (out value) == PopResult.Succeed) {
 240                                                 if (value != null) {
 241                                                         if (CheckTaskFitness (value))
 242                                                                 value.Execute (null);
 243                                                         else
 244                                                                 sharedWorkQueue.TryAdd (value);
 245                                                 }
 246                                         }
 247
 248                                         if (predicate ()) {
 249                                                 return;
 250                                         }
 251                                 }
 252                         }
 253                 }
 254
 255                 static bool CheckTaskFitness (Task t)
 256                 {
 257                         return (t.CreationOptions | TaskCreationOptions.LongRunning) > 0;
 258                 }
 259
 260                 public bool Finished {
 261                         get {
 262                                 return started == 0;
 263                         }
 264                 }
 265
 266                 public bool IsLocal {
 267                         get {
 268                                 return isLocal;
 269                         }
 270                 }
 271
 272                 public int Id {
 273                         get {
 274                                 return workerThread.ManagedThreadId;
 275                         }
 276                 }
 277
 278                 public bool Equals (ThreadWorker other)
 279                 {
 280                         return (other == null) ? false : object.ReferenceEquals (this.dDeque, other.dDeque);
 281                 }
 282
 283                 public override bool Equals (object obj)
 284                 {
 285                         ThreadWorker temp = obj as ThreadWorker;
 286                         return temp == null ? false : Equals (temp);
 287                 }
 288
 289                 public override int GetHashCode ()
 290                 {
 291                         return workerThread.ManagedThreadId.GetHashCode ();
 292                 }
 293         }
 294 }
 295 #endif