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