Mercurial > pub > ImplabNet
annotate Implab/AbstractEvent.cs @ 160:5802131432e4 v2
fixed regression: race condition in Promise
DFA refactoring
| author | cin |
|---|---|
| date | Thu, 18 Feb 2016 19:38:54 +0300 |
| parents | 97fbbf816844 |
| children | 822aab37b107 |
| rev | line source |
|---|---|
| 144 | 1 using System; |
| 2 using Implab.Parallels; | |
| 3 using System.Threading; | |
| 4 using System.Reflection; | |
| 5 | |
| 6 namespace Implab { | |
| 145 | 7 public abstract class AbstractEvent<THandler> : ICancellationToken, ICancellable { |
| 144 | 8 |
| 9 const int UNRESOLVED_SATE = 0; | |
| 10 const int TRANSITIONAL_STATE = 1; | |
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11 protected const int SUCCEEDED_STATE = 2; |
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12 protected const int REJECTED_STATE = 3; |
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13 protected const int CANCELLED_STATE = 4; |
| 144 | 14 |
| 15 const int CANCEL_NOT_REQUESTED = 0; | |
| 16 const int CANCEL_REQUESTING = 1; | |
| 17 const int CANCEL_REQUESTED = 2; | |
| 18 | |
| 19 const int RESERVED_HANDLERS_COUNT = 4; | |
| 20 | |
| 21 int m_state; | |
| 22 Exception m_error; | |
| 23 int m_handlersCount; | |
| 24 | |
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25 //readonly THandler[] m_handlers = new THandler[RESERVED_HANDLERS_COUNT]; |
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26 THandler[] m_handlers; |
| 144 | 27 MTQueue<THandler> m_extraHandlers; |
| 28 int m_handlerPointer = -1; | |
| 29 int m_handlersCommited; | |
| 30 | |
| 31 int m_cancelRequest; | |
| 32 Exception m_cancelationReason; | |
| 33 MTQueue<Action<Exception>> m_cancelationHandlers; | |
| 34 | |
| 35 | |
| 36 #region state managment | |
| 37 bool BeginTransit() { | |
| 38 return UNRESOLVED_SATE == Interlocked.CompareExchange(ref m_state, TRANSITIONAL_STATE, UNRESOLVED_SATE); | |
| 39 } | |
| 40 | |
| 41 void CompleteTransit(int state) { | |
| 42 if (TRANSITIONAL_STATE != Interlocked.CompareExchange(ref m_state, state, TRANSITIONAL_STATE)) | |
| 43 throw new InvalidOperationException("Can't complete transition when the object isn't in the transitional state"); | |
| 44 } | |
| 45 | |
| 46 void WaitTransition() { | |
| 47 while (m_state == TRANSITIONAL_STATE) { | |
| 48 Thread.MemoryBarrier(); | |
| 49 } | |
| 50 } | |
| 51 | |
| 52 protected bool BeginSetResult() { | |
| 53 if (!BeginTransit()) { | |
| 54 WaitTransition(); | |
| 55 if (m_state != CANCELLED_STATE) | |
| 56 throw new InvalidOperationException("The promise is already resolved"); | |
| 57 return false; | |
| 58 } | |
| 59 return true; | |
| 60 } | |
| 61 | |
| 62 protected void EndSetResult() { | |
| 63 CompleteTransit(SUCCEEDED_STATE); | |
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64 Signal(); |
| 144 | 65 } |
| 66 | |
| 67 | |
| 68 | |
| 69 /// <summary> | |
| 70 /// Выполняет обещание, сообщая об ошибке | |
| 71 /// </summary> | |
| 72 /// <remarks> | |
| 73 /// Поскольку обещание должно работать в многопточной среде, при его выполнении сразу несколько потоков | |
| 74 /// могу вернуть ошибку, при этом только первая будет использована в качестве результата, остальные | |
| 75 /// будут проигнорированы. | |
| 76 /// </remarks> | |
| 77 /// <param name="error">Исключение возникшее при выполнении операции</param> | |
| 78 /// <exception cref="InvalidOperationException">Данное обещание уже выполнено</exception> | |
| 79 protected void SetError(Exception error) { | |
| 80 if (BeginTransit()) { | |
| 81 if (error is OperationCanceledException) { | |
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82 m_error = error.InnerException; |
| 144 | 83 CompleteTransit(CANCELLED_STATE); |
| 84 } else { | |
| 85 m_error = error is PromiseTransientException ? error.InnerException : error; | |
| 86 CompleteTransit(REJECTED_STATE); | |
| 87 } | |
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88 Signal(); |
| 144 | 89 } else { |
| 90 WaitTransition(); | |
| 91 if (m_state == SUCCEEDED_STATE) | |
| 92 throw new InvalidOperationException("The promise is already resolved"); | |
| 93 } | |
| 94 } | |
| 95 | |
| 96 /// <summary> | |
| 97 /// Отменяет операцию, если это возможно. | |
| 98 /// </summary> | |
| 99 /// <remarks>Для определения была ли операция отменена следует использовать свойство <see cref="IsCancelled"/>.</remarks> | |
| 100 protected void SetCancelled(Exception reason) { | |
| 101 if (BeginTransit()) { | |
| 102 m_error = reason; | |
| 103 CompleteTransit(CANCELLED_STATE); | |
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104 Signal(); |
| 144 | 105 } |
| 106 } | |
| 107 | |
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108 protected abstract void SignalHandler(THandler handler, int signal); |
| 144 | 109 |
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110 void Signal() { |
| 144 | 111 var hp = m_handlerPointer; |
| 112 var slot = hp +1 ; | |
| 113 while (slot < m_handlersCommited) { | |
| 114 if (Interlocked.CompareExchange(ref m_handlerPointer, slot, hp) == hp) { | |
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115 SignalHandler(m_handlers[slot], m_state); |
| 144 | 116 } |
| 117 hp = m_handlerPointer; | |
| 118 slot = hp +1 ; | |
| 119 } | |
| 120 | |
| 121 | |
| 122 if (m_extraHandlers != null) { | |
| 123 THandler handler; | |
| 124 while (m_extraHandlers.TryDequeue(out handler)) | |
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125 SignalHandler(handler, m_state); |
| 144 | 126 } |
| 127 } | |
| 128 | |
| 129 #endregion | |
| 130 | |
| 131 protected abstract Signal GetResolveSignal(); | |
| 132 | |
| 133 #region synchronization traits | |
| 134 protected void WaitResult(int timeout) { | |
| 148 | 135 if (!(IsResolved || GetResolveSignal().Wait(timeout))) |
| 136 throw new TimeoutException(); | |
| 144 | 137 |
| 138 switch (m_state) { | |
| 139 case SUCCEEDED_STATE: | |
| 140 return; | |
| 141 case CANCELLED_STATE: | |
| 142 throw new OperationCanceledException(); | |
| 143 case REJECTED_STATE: | |
| 144 throw new TargetInvocationException(m_error); | |
| 145 default: | |
| 146 throw new ApplicationException(String.Format("Invalid promise state {0}", m_state)); | |
| 147 } | |
| 148 } | |
| 149 #endregion | |
| 150 | |
| 151 #region handlers managment | |
| 152 | |
| 153 protected void AddHandler(THandler handler) { | |
| 154 | |
| 155 if (m_state > 1) { | |
| 156 // the promise is in the resolved state, just invoke the handler | |
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157 SignalHandler(handler, m_state); |
| 144 | 158 } else { |
| 159 var slot = Interlocked.Increment(ref m_handlersCount) - 1; | |
| 160 | |
| 161 if (slot < RESERVED_HANDLERS_COUNT) { | |
| 162 | |
| 160 | 163 if (slot == 0) { |
| 164 m_handlers = new THandler[RESERVED_HANDLERS_COUNT]; | |
| 165 } else { | |
| 166 while (m_handlers == null) | |
| 167 Thread.MemoryBarrier(); | |
| 168 } | |
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169 |
| 144 | 170 m_handlers[slot] = handler; |
| 171 | |
| 172 while (slot != Interlocked.CompareExchange(ref m_handlersCommited, slot + 1, slot)) { | |
| 173 } | |
| 174 | |
| 175 if (m_state > 1) { | |
| 176 do { | |
| 177 var hp = m_handlerPointer; | |
| 178 slot = hp + 1; | |
| 179 if (slot < m_handlersCommited) { | |
| 180 if (Interlocked.CompareExchange(ref m_handlerPointer, slot, hp) != hp) | |
| 181 continue; | |
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182 SignalHandler(m_handlers[slot], m_state); |
| 144 | 183 } |
| 184 break; | |
| 185 } while(true); | |
| 186 } | |
| 187 } else { | |
| 188 if (slot == RESERVED_HANDLERS_COUNT) { | |
| 189 m_extraHandlers = new MTQueue<THandler>(); | |
| 190 } else { | |
| 191 while (m_extraHandlers == null) | |
| 192 Thread.MemoryBarrier(); | |
| 193 } | |
| 194 | |
| 195 m_extraHandlers.Enqueue(handler); | |
| 196 | |
| 197 if (m_state > 1 && m_extraHandlers.TryDequeue(out handler)) | |
| 198 // if the promise have been resolved while we was adding the handler to the queue | |
| 199 // we can't guarantee that someone is still processing it | |
| 200 // therefore we need to fetch a handler from the queue and execute it | |
| 201 // note that fetched handler may be not the one that we have added | |
| 202 // even we can fetch no handlers at all :) | |
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203 SignalHandler(handler, m_state); |
| 144 | 204 } |
| 205 } | |
| 206 } | |
| 207 | |
| 208 #endregion | |
| 209 | |
| 210 #region IPromise implementation | |
| 211 | |
| 212 public bool IsResolved { | |
| 213 get { | |
| 214 Thread.MemoryBarrier(); | |
| 215 return m_state > 1; | |
| 216 } | |
| 217 } | |
| 218 | |
| 219 public bool IsCancelled { | |
| 220 get { | |
| 221 Thread.MemoryBarrier(); | |
| 222 return m_state == CANCELLED_STATE; | |
| 223 } | |
| 224 } | |
| 225 | |
| 226 #endregion | |
| 227 | |
| 228 public Exception Error { | |
| 229 get { | |
| 230 return m_error; | |
| 231 } | |
| 232 } | |
| 233 | |
| 145 | 234 public bool CancelOperationIfRequested() { |
| 235 if (IsCancellationRequested) { | |
| 236 CancelOperation(CancellationReason); | |
| 237 return true; | |
| 238 } | |
| 239 return false; | |
| 144 | 240 } |
| 241 | |
| 242 public virtual void CancelOperation(Exception reason) { | |
| 243 SetCancelled(reason); | |
| 244 } | |
| 245 | |
| 145 | 246 public void CancellationRequested(Action<Exception> handler) { |
| 144 | 247 Safe.ArgumentNotNull(handler, "handler"); |
| 145 | 248 if (IsCancellationRequested) |
| 249 handler(CancellationReason); | |
| 144 | 250 |
| 251 if (m_cancelationHandlers == null) | |
| 252 Interlocked.CompareExchange(ref m_cancelationHandlers, new MTQueue<Action<Exception>>(), null); | |
| 253 | |
| 254 m_cancelationHandlers.Enqueue(handler); | |
| 255 | |
| 145 | 256 if (IsCancellationRequested && m_cancelationHandlers.TryDequeue(out handler)) |
| 144 | 257 // TryDeque implies MemoryBarrier() |
| 258 handler(m_cancelationReason); | |
| 259 } | |
| 260 | |
| 145 | 261 public bool IsCancellationRequested { |
| 144 | 262 get { |
| 263 do { | |
| 264 if (m_cancelRequest == CANCEL_NOT_REQUESTED) | |
| 265 return false; | |
| 266 if (m_cancelRequest == CANCEL_REQUESTED) | |
| 267 return true; | |
| 268 Thread.MemoryBarrier(); | |
| 269 } while(true); | |
| 270 } | |
| 271 } | |
| 272 | |
| 145 | 273 public Exception CancellationReason { |
| 144 | 274 get { |
| 275 do { | |
| 276 Thread.MemoryBarrier(); | |
| 277 } while(m_cancelRequest == CANCEL_REQUESTING); | |
| 278 | |
| 279 return m_cancelationReason; | |
| 280 } | |
| 281 } | |
| 282 | |
| 283 #region ICancellable implementation | |
| 284 | |
| 285 public void Cancel() { | |
| 286 Cancel(null); | |
| 287 } | |
| 288 | |
| 289 public void Cancel(Exception reason) { | |
| 145 | 290 if (CANCEL_NOT_REQUESTED == Interlocked.CompareExchange(ref m_cancelRequest, CANCEL_REQUESTING, CANCEL_NOT_REQUESTED)) { |
| 144 | 291 m_cancelationReason = reason; |
| 292 m_cancelRequest = CANCEL_REQUESTED; | |
| 293 if (m_cancelationHandlers != null) { | |
| 294 Action<Exception> handler; | |
| 295 while (m_cancelationHandlers.TryDequeue(out handler)) | |
| 296 handler(m_cancelationReason); | |
| 297 } | |
| 298 } | |
| 299 } | |
| 300 | |
| 301 #endregion | |
| 302 } | |
| 303 } | |
| 304 |