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132
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1 /**
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2 * The condition module provides a primitive for synchronized condition
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3 * checking.
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4 *
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5 * Copyright: Copyright (C) 2005-2006 Sean Kelly. All rights reserved.
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6 * License: BSD style: $(LICENSE)
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7 * Authors: Sean Kelly
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8 */
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9 module tango.core.sync.Condition;
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10
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11
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12 public import tango.core.Exception : SyncException;
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13 public import tango.core.sync.Mutex;
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14
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15 version( Win32 )
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16 {
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17 private import tango.core.sync.Semaphore;
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18 private import tango.sys.win32.UserGdi;
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19 }
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20 else version( Posix )
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21 {
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22 private import tango.core.sync.Config;
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23 private import tango.stdc.errno;
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24 private import tango.stdc.posix.pthread;
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25 private import tango.stdc.posix.time;
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26 }
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27
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28
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29 ////////////////////////////////////////////////////////////////////////////////
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30 // Condition
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31 //
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32 // void wait();
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33 // void notify();
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34 // void notifyAll();
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35 ////////////////////////////////////////////////////////////////////////////////
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36
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37
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38 /**
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39 * This class represents a condition variable as concieved by C.A.R. Hoare. As
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40 * per Mesa type monitors however, "signal" has been replaced with "notify" to
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41 * indicate that control is not transferred to the waiter when a notification
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42 * is sent.
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43 */
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44 class Condition
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45 {
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46 ////////////////////////////////////////////////////////////////////////////
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47 // Initialization
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48 ////////////////////////////////////////////////////////////////////////////
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49
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50
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51 /**
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52 * Initializes a condition object which is associated with the supplied
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53 * mutex object.
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54 *
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55 * Params:
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56 * m = The mutex with which this condition will be associated.
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57 *
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58 * Throws:
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59 * SyncException on error.
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60 */
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61 this( Mutex m )
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62 {
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63 version( Win32 )
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64 {
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65 m_blockLock = CreateSemaphoreA( null, 1, 1, null );
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66 if( m_blockLock == m_blockLock.init )
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67 throw new SyncException( "Unable to initialize condition" );
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68 scope(failure) CloseHandle( m_blockLock );
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69
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70 m_blockQueue = CreateSemaphoreA( null, 0, int.max, null );
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71 if( m_blockQueue == m_blockQueue.init )
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72 throw new SyncException( "Unable to initialize condition" );
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73 scope(failure) CloseHandle( m_blockQueue );
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74
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75 InitializeCriticalSection( &m_unblockLock );
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76 m_assocMutex = m;
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77 }
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78 else version( Posix )
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79 {
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80 m_mutexAddr = m.handleAddr();
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81
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82 int rc = pthread_cond_init( &m_hndl, null );
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83 if( rc )
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84 throw new SyncException( "Unable to initialize condition" );
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85 }
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86 }
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87
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88
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89 ~this()
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90 {
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91 version( Win32 )
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92 {
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93 BOOL rc = CloseHandle( m_blockLock );
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94 assert( rc, "Unable to destroy condition" );
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95 rc = CloseHandle( m_blockQueue );
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96 assert( rc, "Unable to destroy condition" );
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97 DeleteCriticalSection( &m_unblockLock );
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98 }
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99 else version( Posix )
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100 {
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101 int rc = pthread_cond_destroy( &m_hndl );
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102 assert( !rc, "Unable to destroy condition" );
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103 }
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104 }
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105
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106
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107 ////////////////////////////////////////////////////////////////////////////
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108 // General Actions
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109 ////////////////////////////////////////////////////////////////////////////
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110
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111
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112 /**
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113 * Wait until notified.
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114 *
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115 * Throws:
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116 * SyncException on error.
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117 */
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118 void wait()
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119 {
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120 version( Win32 )
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121 {
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122 timedWait( INFINITE );
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123 }
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124 else version( Posix )
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125 {
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126 int rc = pthread_cond_wait( &m_hndl, m_mutexAddr );
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127 if( rc )
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128 throw new SyncException( "Unable to wait for condition" );
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129 }
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130 }
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131
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132
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133 /**
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134 * Suspends the calling thread until a notification occurs or until the
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135 * supplied time period has elapsed. The supplied period may be up to a
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136 * maximum of (uint.max - 1) milliseconds.
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137 *
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138 * Params:
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139 * period = The time to wait, in seconds (fractional values are accepted).
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140 *
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141 * In:
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142 * period must be less than (uint.max - 1) milliseconds.
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143 *
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144 * Returns:
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145 * true if notified before the timeout and false if not.
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146 *
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147 * Throws:
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148 * SyncException on error.
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149 */
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150 bool wait( double period )
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151 in
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152 {
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153 // NOTE: The fractional value added to period is to correct fp error.
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154 assert( period * 1000 + 0.1 < uint.max - 1 );
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155 }
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156 body
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157 {
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158 version( Win32 )
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159 {
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160 return timedWait( cast(uint)(period * 1000 + 0.1) );
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161 }
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162 else version( Posix )
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163 {
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164 timespec t;
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165
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166 getTimespec( t );
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167 adjTimespec( t, period );
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168 int rc = pthread_cond_timedwait( &m_hndl, m_mutexAddr, &t );
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169 if( !rc )
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170 return true;
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171 if( rc == ETIMEDOUT )
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172 return false;
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173 throw new SyncException( "Unable to wait for condition" );
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174 }
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175 }
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176
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177 /**
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178 * Notifies one waiter.
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179 *
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180 * Throws:
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181 * SyncException on error.
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182 */
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183 void notify()
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184 {
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185 version( Win32 )
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186 {
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187 notify( false );
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188 }
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189 else version( Posix )
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190 {
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191 int rc = pthread_cond_signal( &m_hndl );
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192 if( rc )
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193 throw new SyncException( "Unable to notify condition" );
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194 }
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195 }
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196
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197
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198 /**
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199 * Notifies all waiters.
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200 *
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201 * Throws:
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202 * SyncException on error.
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203 */
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204 void notifyAll()
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205 {
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206 version( Win32 )
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207 {
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208 notify( true );
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209 }
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210 else version( Posix )
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211 {
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212 int rc = pthread_cond_broadcast( &m_hndl );
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213 if( rc )
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214 throw new SyncException( "Unable to notify condition" );
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215 }
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216 }
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217
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218
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219 private:
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220 version( Win32 )
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221 {
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222 bool timedWait( DWORD timeout )
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223 {
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224 int numSignalsLeft;
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225 int numWaitersGone;
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226 DWORD rc;
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227
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228 rc = WaitForSingleObject( m_blockLock, INFINITE );
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229 assert( rc == WAIT_OBJECT_0 );
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230
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231 m_numWaitersBlocked++;
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232
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233 rc = ReleaseSemaphore( m_blockLock, 1, null );
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234 assert( rc );
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235
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236 m_assocMutex.unlock();
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237 scope(failure) m_assocMutex.lock();
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238
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239 rc = WaitForSingleObject( m_blockQueue, timeout );
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240 assert( rc == WAIT_OBJECT_0 || rc == WAIT_TIMEOUT );
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241 bool timedOut = (rc == WAIT_TIMEOUT);
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242
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243 EnterCriticalSection( &m_unblockLock );
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244 scope(failure) LeaveCriticalSection( &m_unblockLock );
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245
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246 if( (numSignalsLeft = m_numWaitersToUnblock) != 0 )
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247 {
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248 if ( timedOut )
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249 {
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250 // timeout (or canceled)
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251 if( m_numWaitersBlocked != 0 )
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252 {
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253 m_numWaitersBlocked--;
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254 // do not unblock next waiter below (already unblocked)
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255 numSignalsLeft = 0;
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256 }
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257 else
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258 {
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259 // spurious wakeup pending!!
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260 m_numWaitersGone = 1;
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261 }
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262 }
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263 if( --m_numWaitersToUnblock == 0 )
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264 {
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265 if( m_numWaitersBlocked != 0 )
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266 {
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267 // open the gate
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268 rc = ReleaseSemaphore( m_blockLock, 1, null );
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269 assert( rc );
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270 // do not open the gate below again
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271 numSignalsLeft = 0;
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272 }
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273 else if( (numWaitersGone = m_numWaitersGone) != 0 )
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274 {
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275 m_numWaitersGone = 0;
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276 }
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277 }
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278 }
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279 else if( ++m_numWaitersGone == int.max / 2 )
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280 {
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281 // timeout/canceled or spurious event :-)
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282 rc = WaitForSingleObject( m_blockLock, INFINITE );
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283 assert( rc == WAIT_OBJECT_0 );
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284 // something is going on here - test of timeouts?
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285 m_numWaitersBlocked -= m_numWaitersGone;
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286 rc = ReleaseSemaphore( m_blockLock, 1, null );
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287 assert( rc == WAIT_OBJECT_0 );
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288 m_numWaitersGone = 0;
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289 }
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290
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291 LeaveCriticalSection( &m_unblockLock );
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292
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293 if( numSignalsLeft == 1 )
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294 {
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295 // better now than spurious later (same as ResetEvent)
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296 for( ; numWaitersGone > 0; --numWaitersGone )
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297 {
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298 rc = WaitForSingleObject( m_blockQueue, INFINITE );
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299 assert( rc == WAIT_OBJECT_0 );
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300 }
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301 // open the gate
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302 rc = ReleaseSemaphore( m_blockLock, 1, null );
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303 assert( rc );
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304 }
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305 else if( numSignalsLeft != 0 )
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306 {
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307 // unblock next waiter
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308 rc = ReleaseSemaphore( m_blockQueue, 1, null );
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309 assert( rc );
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310 }
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311 m_assocMutex.lock();
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312 return !timedOut;
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313 }
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314
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315
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316 void notify( bool all )
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317 {
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318 DWORD rc;
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319
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320 EnterCriticalSection( &m_unblockLock );
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321 scope(failure) LeaveCriticalSection( &m_unblockLock );
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322
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323 if( m_numWaitersToUnblock != 0 )
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324 {
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325 if( m_numWaitersBlocked == 0 )
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326 {
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327 LeaveCriticalSection( &m_unblockLock );
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328 return;
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329 }
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330 if( all )
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331 {
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332 m_numWaitersToUnblock += m_numWaitersBlocked;
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333 m_numWaitersBlocked = 0;
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334 }
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335 else
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336 {
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337 m_numWaitersToUnblock++;
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338 m_numWaitersBlocked--;
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339 }
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340 LeaveCriticalSection( &m_unblockLock );
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341 }
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342 else if( m_numWaitersBlocked > m_numWaitersGone )
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343 {
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344 rc = WaitForSingleObject( m_blockLock, INFINITE );
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345 assert( rc == WAIT_OBJECT_0 );
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346 if( 0 != m_numWaitersGone )
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347 {
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348 m_numWaitersBlocked -= m_numWaitersGone;
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349 m_numWaitersGone = 0;
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350 }
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351 if( all )
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352 {
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353 m_numWaitersToUnblock = m_numWaitersBlocked;
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354 m_numWaitersBlocked = 0;
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355 }
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356 else
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357 {
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358 m_numWaitersToUnblock = 1;
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359 m_numWaitersBlocked--;
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360 }
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361 LeaveCriticalSection( &m_unblockLock );
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362 rc = ReleaseSemaphore( m_blockQueue, 1, null );
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363 assert( rc );
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364 }
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365 else
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366 {
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367 LeaveCriticalSection( &m_unblockLock );
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368 }
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369 }
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370
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371
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372 // NOTE: This implementation uses Algorithm 8c as described here:
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373 // http://groups.google.com/group/comp.programming.threads/
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374 // browse_frm/thread/1692bdec8040ba40/e7a5f9d40e86503a
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375 HANDLE m_blockLock; // auto-reset event (now semaphore)
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376 HANDLE m_blockQueue; // auto-reset event (now semaphore)
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377 Mutex m_assocMutex; // external mutex/CS
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378 CRITICAL_SECTION m_unblockLock; // internal mutex/CS
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379 int m_numWaitersGone = 0;
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380 int m_numWaitersBlocked = 0;
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381 int m_numWaitersToUnblock = 0;
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382 }
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383 else version( Posix )
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384 {
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385 pthread_cond_t m_hndl;
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386 pthread_mutex_t* m_mutexAddr;
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387 }
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388 }
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389
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390
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391 ////////////////////////////////////////////////////////////////////////////////
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392 // Unit Tests
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393 ////////////////////////////////////////////////////////////////////////////////
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394
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395
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396 debug( UnitTest )
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397 {
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398 private import tango.core.Thread;
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399 private import tango.core.sync.Mutex;
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400 private import tango.core.sync.Semaphore;
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401
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402
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403 void testNotify()
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404 {
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405 auto mutex = new Mutex;
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406 auto condReady = new Condition( mutex );
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407 auto semDone = new Semaphore;
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408 auto synLoop = new Object;
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409 int numWaiters = 10;
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410 int numTries = 10;
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411 int numReady = 0;
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412 int numTotal = 0;
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413 int numDone = 0;
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414 int numPost = 0;
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415
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416 void waiter()
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417 {
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418 for( int i = 0; i < numTries; ++i )
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419 {
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420 synchronized( mutex )
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421 {
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422 while( numReady < 1 )
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423 {
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424 condReady.wait();
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425 }
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426 --numReady;
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427 ++numTotal;
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428 }
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429
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430 synchronized( synLoop )
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431 {
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432 ++numDone;
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433 }
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434 semDone.wait();
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435 }
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436 }
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437
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438 auto group = new ThreadGroup;
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439
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440 for( int i = 0; i < numWaiters; ++i )
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441 group.create( &waiter );
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442
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443 for( int i = 0; i < numTries; ++i )
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444 {
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445 for( int j = 0; j < numWaiters; ++j )
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446 {
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447 synchronized( mutex )
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448 {
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449 ++numReady;
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450 condReady.notify();
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451 }
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452 }
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453 while( true )
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454 {
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455 synchronized( synLoop )
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456 {
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457 if( numDone >= numWaiters )
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458 break;
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459 }
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460 Thread.yield();
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461 }
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462 for( int j = 0; j < numWaiters; ++j )
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463 {
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464 semDone.notify();
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465 }
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466 }
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467
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468 group.joinAll();
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469 assert( numTotal == numWaiters * numTries );
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470 }
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471
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472
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473 void testNotifyAll()
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474 {
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475 auto mutex = new Mutex;
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476 auto condReady = new Condition( mutex );
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477 int numWaiters = 10;
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478 int numReady = 0;
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479 int numDone = 0;
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480 bool alert = false;
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481
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482 void waiter()
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483 {
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484 synchronized( mutex )
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485 {
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486 ++numReady;
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487 while( !alert )
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488 condReady.wait();
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489 ++numDone;
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490 }
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491 }
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492
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493 auto group = new ThreadGroup;
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494
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495 for( int i = 0; i < numWaiters; ++i )
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496 group.create( &waiter );
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497
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498 while( true )
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499 {
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500 synchronized( mutex )
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501 {
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502 if( numReady >= numWaiters )
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503 {
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504 alert = true;
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505 condReady.notifyAll();
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506 break;
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507 }
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508 }
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509 Thread.yield();
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510 }
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511 group.joinAll();
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512 assert( numReady == numWaiters && numDone == numWaiters );
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513 }
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|
514
|
|
|
515
|
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|
516 void testWaitTimeout()
|
|
|
517 {
|
|
|
518 auto mutex = new Mutex;
|
|
|
519 auto condReady = new Condition( mutex );
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|
|
520 bool waiting = false;
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|
|
521 bool alertedOne = true;
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|
|
522 bool alertedTwo = true;
|
|
|
523
|
|
|
524 void waiter()
|
|
|
525 {
|
|
|
526 synchronized( mutex )
|
|
|
527 {
|
|
|
528 waiting = true;
|
|
|
529 alertedOne = condReady.wait( 1 );
|
|
|
530 alertedTwo = condReady.wait( 1 );
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|
|
531 }
|
|
|
532 }
|
|
|
533
|
|
|
534 auto thread = new Thread( &waiter );
|
|
|
535 thread.start();
|
|
|
536
|
|
|
537 while( true )
|
|
|
538 {
|
|
|
539 synchronized( mutex )
|
|
|
540 {
|
|
|
541 if( waiting )
|
|
|
542 {
|
|
|
543 condReady.notify();
|
|
|
544 break;
|
|
|
545 }
|
|
|
546 }
|
|
|
547 Thread.yield();
|
|
|
548 }
|
|
|
549 thread.join();
|
|
|
550 assert( waiting && alertedOne && !alertedTwo );
|
|
|
551 }
|
|
|
552
|
|
|
553
|
|
|
554 unittest
|
|
|
555 {
|
|
|
556 testNotify();
|
|
|
557 testNotifyAll();
|
|
|
558 testWaitTimeout();
|
|
|
559 }
|
|
|
560 }
|
