mcs/class/corlib/System.Threading/ManualResetEventSlim.cs

   1 // ManualResetEventSlim.cs
   2 //
   3 // Authors:
   4 //    Marek Safar  <marek.safar@gmail.com>
   5 //
   6 // Copyright (c) 2008 Jérémie "Garuma" Laval
   7 // Copyright 2011 Xamarin Inc (http://www.xamarin.com).
   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 //
  28
  29 #if NET_4_0
  30
  31 namespace System.Threading
  32 {
  33         [System.Diagnostics.DebuggerDisplayAttribute ("Set = {IsSet}")]
  34         public class ManualResetEventSlim : IDisposable
  35         {
  36                 readonly int spinCount;
  37
  38                 ManualResetEvent handle;
  39                 internal AtomicBooleanValue disposed;
  40                 int used;
  41                 int state;
  42
  43                 public ManualResetEventSlim ()
  44                         : this (false, 10)
  45                 {
  46                 }
  47
  48                 public ManualResetEventSlim (bool initialState)
  49                         : this (initialState, 10)
  50                 {
  51                 }
  52
  53                 public ManualResetEventSlim (bool initialState, int spinCount)
  54                 {
  55                         if (spinCount < 0 || spinCount > 2047)
  56                                 throw new ArgumentOutOfRangeException ("spinCount");
  57
  58                         this.state = initialState ? 1 : 0;
  59                         this.spinCount = spinCount;
  60                 }
  61
  62                 public bool IsSet {
  63                         get {
  64                                 return (state & 1) == 1;
  65                         }
  66                 }
  67
  68                 public int SpinCount {
  69                         get {
  70                                 return spinCount;
  71                         }
  72                 }
  73
  74                 public void Reset ()
  75                 {
  76                         ThrowIfDisposed ();
  77
  78                         var stamp = UpdateStateWithOp (false);
  79                         if (handle != null)
  80                                 CommitChangeToHandle (stamp);
  81                 }
  82
  83                 public void Set ()
  84                 {
  85                         var stamp = UpdateStateWithOp (true);
  86                         if (handle != null)
  87                                 CommitChangeToHandle (stamp);
  88                 }
  89
  90                 long UpdateStateWithOp (bool set)
  91                 {
  92                         int oldValue, newValue;
  93                         do {
  94                                 oldValue = state;
  95                                 newValue = (int)(((oldValue >> 1) + 1) << 1) | (set ? 1 : 0);
  96                         } while (Interlocked.CompareExchange (ref state, newValue, oldValue) != oldValue);
  97                         return newValue;
  98                 }
  99
 100                 void CommitChangeToHandle (long stamp)
 101                 {
 102                         Interlocked.Increment (ref used);
 103                         var tmpHandle = handle;
 104                         if (tmpHandle != null) {
 105                                 // First in all case we carry the operation we were called for
 106                                 if ((stamp & 1) == 1)
 107                                         tmpHandle.Set ();
 108                                 else
 109                                         tmpHandle.Reset ();
 110
 111                                 /* Then what may happen is that the two suboperations (state change and handle change)
 112                                  * overlapped with others. In our case it doesn't matter if the two suboperations aren't
 113                                  * executed together at the same time, the only thing we have to make sure of is that both
 114                                  * state and handle are synchronized on the last visible state change.
 115                                  *
 116                                  * For instance if S is state change and H is handle change, for 3 concurrent operations
 117                                  * we may have the following serialized timeline: S1 S2 H2 S3 H3 H1
 118                                  * Which is perfectly fine (all S were converted to H at some stage) but in that case
 119                                  * we have a mismatch between S and H at the end because the last operations done were
 120                                  * S3/H1. We thus need to repeat H3 to get to the desired final state.
 121                                  */
 122                                 int currentState;
 123                                 do {
 124                                         currentState = state;
 125                                         if (currentState != stamp && (stamp & 1) != (currentState & 1)) {
 126                                                 if ((currentState & 1) == 1)
 127                                                         tmpHandle.Set ();
 128                                                 else
 129                                                         tmpHandle.Reset ();
 130                                         }
 131                                 } while (currentState != state);
 132                         }
 133                         Interlocked.Decrement (ref used);
 134                 }
 135
 136                 public void Wait ()
 137                 {
 138                         Wait (CancellationToken.None);
 139                 }
 140
 141                 public bool Wait (int millisecondsTimeout)
 142                 {
 143                         return Wait (millisecondsTimeout, CancellationToken.None);
 144                 }
 145
 146                 public bool Wait (TimeSpan timeout)
 147                 {
 148                         return Wait (CheckTimeout (timeout), CancellationToken.None);
 149                 }
 150
 151                 public void Wait (CancellationToken cancellationToken)
 152                 {
 153                         Wait (Timeout.Infinite, cancellationToken);
 154                 }
 155
 156                 public bool Wait (int millisecondsTimeout, CancellationToken cancellationToken)
 157                 {
 158                         if (millisecondsTimeout < -1)
 159                                 throw new ArgumentOutOfRangeException ("millisecondsTimeout");
 160
 161                         ThrowIfDisposed ();
 162
 163                         if (!IsSet) {
 164                                 SpinWait wait = new SpinWait ();
 165
 166                                 while (!IsSet) {
 167                                         if (wait.Count < spinCount) {
 168                                                 wait.SpinOnce ();
 169                                                 continue;
 170                                         }
 171
 172                                         break;
 173                                 }
 174
 175                                 cancellationToken.ThrowIfCancellationRequested ();
 176
 177                                 if (IsSet)
 178                                         return true;
 179
 180                                 WaitHandle handle = WaitHandle;
 181
 182                                 if (cancellationToken.CanBeCanceled) {
 183                                         var result = WaitHandle.WaitAny (new[] { handle, cancellationToken.WaitHandle }, millisecondsTimeout, false);
 184                                         if (result == 1)
 185                                                 throw new OperationCanceledException (cancellationToken);
 186                                         if (result == WaitHandle.WaitTimeout)
 187                                                 return false;
 188                                 } else {
 189                                         if (!handle.WaitOne (millisecondsTimeout, false))
 190                                                 return false;
 191                                 }
 192                         }
 193
 194                         return true;
 195                 }
 196
 197                 public bool Wait (TimeSpan timeout, CancellationToken cancellationToken)
 198                 {
 199                         return Wait (CheckTimeout (timeout), cancellationToken);
 200                 }
 201
 202                 public WaitHandle WaitHandle {
 203                         get {
 204                                 ThrowIfDisposed ();
 205
 206                                 if (handle != null)
 207                                         return handle;
 208
 209                                 var isSet = IsSet;
 210                                 var mre = new ManualResetEvent (IsSet);
 211                                 if (Interlocked.CompareExchange (ref handle, mre, null) == null) {
 212                                         //
 213                                         // Ensure the Set has not ran meantime
 214                                         //
 215                                         if (isSet != IsSet) {
 216                                                 if (IsSet) {
 217                                                         mre.Set ();
 218                                                 } else {
 219                                                         mre.Reset ();
 220                                                 }
 221                                         }
 222                                 } else {
 223                                         //
 224                                         // Release the event when other thread was faster
 225                                         //
 226                                         mre.Dispose ();
 227                                 }
 228
 229                                 return handle;
 230                         }
 231                 }
 232
 233                 public void Dispose ()
 234                 {
 235                         Dispose (true);
 236                 }
 237
 238                 protected virtual void Dispose (bool disposing)
 239                 {
 240                         if (!disposed.TryRelaxedSet ())
 241                                 return;
 242
 243                         if (handle != null) {
 244                                 var tmpHandle = Interlocked.Exchange (ref handle, null);
 245                                 if (used > 0) {
 246                                         // A tiny wait (just a few cycles normally) before releasing
 247                                         SpinWait wait = new SpinWait ();
 248                                         while (used > 0)
 249                                                 wait.SpinOnce ();
 250                                 }
 251                                 tmpHandle.Dispose ();
 252                         }
 253                 }
 254
 255                 void ThrowIfDisposed ()
 256                 {
 257                         if (disposed.Value)
 258                                 throw new ObjectDisposedException ("ManualResetEventSlim");
 259                 }
 260
 261                 static int CheckTimeout (TimeSpan timeout)
 262                 {
 263                         try {
 264                                 return checked ((int)timeout.TotalMilliseconds);
 265                         } catch (System.OverflowException) {
 266                                 throw new ArgumentOutOfRangeException ("timeout");
 267                         }
 268                 }
 269         }
 270 }
 271 #endif