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

   1 #if 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                 #region Sleep related fields
  52                 readonly SpinWait wait = new SpinWait ();
  53                 const int sleepThreshold = 100000;
  54                 #endregion
  55
  56                 Action threadInitializer;
  57
  58                 public ThreadWorker (IScheduler sched, ThreadWorker[] others, IProducerConsumerCollection<Task> sharedWorkQueue,
  59                                      int maxStackSize, ThreadPriority priority)
  60                         : this (sched, others, sharedWorkQueue, true, maxStackSize, priority)
  61                 {
  62                 }
  63
  64                 public ThreadWorker (IScheduler sched, ThreadWorker[] others, IProducerConsumerCollection<Task> sharedWorkQueue,
  65                                      bool createThread, int maxStackSize, ThreadPriority priority)
  66                 {
  67                         this.others          = others;
  68
  69                         this.dDeque = new CyclicDeque<Task> ();
  70
  71                         this.sharedWorkQueue = sharedWorkQueue;
  72                         this.workerLength    = others.Length;
  73                         this.isLocal         = !createThread;
  74
  75                         this.childWorkAdder = delegate (Task t) {
  76                                 dDeque.PushBottom (t);
  77                                 sched.PulseAll ();
  78                         };
  79
  80                         // Find the stealing start index randomly (then the traversal
  81                         // will be done in Round-Robin fashion)
  82                         do {
  83                                 this.stealingStart = r.Next(0, workerLength);
  84                         } while (others[stealingStart] == this);
  85
  86                         InitializeUnderlyingThread (maxStackSize, priority);
  87                 }
  88
  89                 void InitializeUnderlyingThread (int maxStackSize, ThreadPriority priority)
  90                 {
  91                         threadInitializer = delegate {
  92                                 // Special case of the participant ThreadWorker
  93                                 if (isLocal) {
  94                                         this.workerThread = Thread.CurrentThread;
  95                                         return;
  96                                 }
  97
  98                                 this.workerThread = (maxStackSize == 0) ? new Thread (WorkerMethodWrapper) :
  99                                         new Thread (WorkerMethodWrapper, maxStackSize);
 100
 101                                 this.workerThread.IsBackground = true;
 102                                 this.workerThread.Priority = priority;
 103                         };
 104                         threadInitializer ();
 105                 }
 106
 107                 public void Dispose ()
 108                 {
 109                         Stop ();
 110                         if (!isLocal && workerThread.ThreadState != ThreadState.Stopped)
 111                                 workerThread.Abort ();
 112                 }
 113
 114                 public void Pulse ()
 115                 {
 116                         // If the thread was stopped then set it in use and restart it
 117                         int result = Interlocked.Exchange (ref started, 1);
 118                         if (result != 0)
 119                                 return;
 120                         if (!isLocal) {
 121                                 if (this.workerThread.ThreadState != ThreadState.Unstarted) {
 122                                         threadInitializer ();
 123                                 }
 124                                 workerThread.Start ();
 125                         }
 126                 }
 127
 128                 public void Stop ()
 129                 {
 130                         // Set the flag to stop so that the while in the thread will stop
 131                         // doing its infinite loop.
 132                         started = 0;
 133                 }
 134
 135                 // This is the actual method called in the Thread
 136                 void WorkerMethodWrapper ()
 137                 {
 138                         int sleepTime = 0;
 139
 140                         // Main loop
 141                         while (started == 1) {
 142                                 bool result = false;
 143                                 try {
 144                                         result = WorkerMethod ();
 145                                 } catch (Exception e) {
 146                                         Console.WriteLine (e.ToString ());
 147                                 }
 148
 149                                 // Wait a little and if the Thread has been more sleeping than working shut it down
 150                                 wait.SpinOnce ();
 151                                 if (result)
 152                                         sleepTime = 0;
 153                                 if (sleepTime++ > sleepThreshold)
 154                                         break;
 155                         }
 156
 157                         started = 0;
 158                 }
 159
 160                 // Main method, used to do all the logic of retrieving, processing and stealing work.
 161                 bool WorkerMethod ()
 162                 {
 163                         bool result = false;
 164                         bool hasStolenFromOther;
 165                         do {
 166                                 hasStolenFromOther = false;
 167
 168                                 Task value;
 169
 170                                 // We fill up our work deque concurrently with other ThreadWorker
 171                                 while (sharedWorkQueue.Count > 0) {
 172                                         while (sharedWorkQueue.TryTake (out value)) {
 173                                                 dDeque.PushBottom (value);
 174                                         }
 175
 176                                         // Now we process our work
 177                                         while (dDeque.PopBottom (out value) == PopResult.Succeed) {
 178                                                 if (value != null) {
 179                                                         value.Execute (childWorkAdder);
 180                                                         result = true;
 181                                                 }
 182                                         }
 183                                 }
 184
 185                                 // When we have finished, steal from other worker
 186                                 ThreadWorker other;
 187
 188                                 // Repeat the operation a little so that we can let other things process.
 189                                 for (int j = 0; j < maxRetry; j++) {
 190                                         // Start stealing with the ThreadWorker at our right to minimize contention
 191                                         for (int it = stealingStart; it < stealingStart + workerLength; it++) {
 192                                                 int i = it % workerLength;
 193                                                 if ((other = others [i]) == null || other == this)
 194                                                         continue;
 195
 196                                                 // Maybe make this steal more than one item at a time, see TODO.
 197                                                 if (other.dDeque.PopTop (out value) == PopResult.Succeed) {
 198                                                         hasStolenFromOther = true;
 199                                                         if (value != null) {
 200                                                                 value.Execute (childWorkAdder);
 201                                                                 result = true;
 202                                                         }
 203                                                 }
 204                                         }
 205                                 }
 206                         } while (sharedWorkQueue.Count > 0 || hasStolenFromOther);
 207
 208                         return result;
 209                 }
 210
 211                 // Almost same as above but with an added predicate and treating one item at a time.
 212                 // It's used by Scheduler Participate(...) method for special waiting case like
 213                 // Task.WaitAll(someTasks) or Task.WaitAny(someTasks)
 214                 // Predicate should be really fast and not blocking as it is called a good deal of time
 215                 // Also, the method skip tasks that are LongRunning to avoid blocking (Task are not LongRunning by default)
 216                 public static void WorkerMethod (Func<bool> predicate, IProducerConsumerCollection<Task> sharedWorkQueue,
 217                                                  ThreadWorker[] others)
 218                 {
 219                         while (!predicate ()) {
 220                                 Task value;
 221
 222                                 // Dequeue only one item as we have restriction
 223                                 if (sharedWorkQueue.TryTake (out value)) {
 224                                         if (value != null) {
 225                                                 if (CheckTaskFitness (value))
 226                                                         value.Execute (null);
 227                                                 else
 228                                                         sharedWorkQueue.TryAdd (value);
 229                                         }
 230                                 }
 231
 232                                 // First check to see if we comply to predicate
 233                                 if (predicate ()) {
 234                                         return;
 235                                 }
 236
 237                                 // Try to complete other work by stealing since our desired tasks may be in other worker
 238                                 ThreadWorker other;
 239                                 for (int i = 0; i < others.Length; i++) {
 240                                         if ((other = others [i]) == null)
 241                                                 continue;
 242
 243                                         if (other.dDeque.PopTop (out value) == PopResult.Succeed) {
 244                                                 if (value != null) {
 245                                                         if (CheckTaskFitness (value))
 246                                                                 value.Execute (null);
 247                                                         else
 248                                                                 sharedWorkQueue.TryAdd (value);
 249                                                 }
 250                                         }
 251
 252                                         if (predicate ()) {
 253                                                 return;
 254                                         }
 255                                 }
 256                         }
 257                 }
 258
 259                 static bool CheckTaskFitness (Task t)
 260                 {
 261                         return (t.CreationOptions | TaskCreationOptions.LongRunning) > 0;
 262                 }
 263
 264                 public bool Finished {
 265                         get {
 266                                 return started == 0;
 267                         }
 268                 }
 269
 270                 public bool IsLocal {
 271                         get {
 272                                 return isLocal;
 273                         }
 274                 }
 275
 276                 public int Id {
 277                         get {
 278                                 return workerThread.ManagedThreadId;
 279                         }
 280                 }
 281
 282                 public bool Equals (ThreadWorker other)
 283                 {
 284                         return (other == null) ? false : object.ReferenceEquals (this.dDeque, other.dDeque);
 285                 }
 286
 287                 public override bool Equals (object obj)
 288                 {
 289                         ThreadWorker temp = obj as ThreadWorker;
 290                         return temp == null ? false : Equals (temp);
 291                 }
 292
 293                 public override int GetHashCode ()
 294                 {
 295                         return workerThread.ManagedThreadId.GetHashCode ();
 296                 }
 297         }
 298 }
 299 #endif