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1 //========================================================================== |
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2 // |
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3 // sync/bin_sem.cxx |
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4 // |
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5 // Binary semaphore implementation |
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6 // |
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7 //========================================================================== |
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8 //####COPYRIGHTBEGIN#### |
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9 // |
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10 // ------------------------------------------- |
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11 // The contents of this file are subject to the Cygnus eCos Public License |
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12 // Version 1.0 (the "License"); you may not use this file except in |
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13 // compliance with the License. You may obtain a copy of the License at |
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14 // http://sourceware.cygnus.com/ecos |
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15 // |
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16 // Software distributed under the License is distributed on an "AS IS" |
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17 // basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the |
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18 // License for the specific language governing rights and limitations under |
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19 // the License. |
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20 // |
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21 // The Original Code is eCos - Embedded Cygnus Operating System, released |
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22 // September 30, 1998. |
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23 // |
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24 // The Initial Developer of the Original Code is Cygnus. Portions created |
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25 // by Cygnus are Copyright (C) 1998,1999 Cygnus Solutions. All Rights Reserved. |
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26 // ------------------------------------------- |
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27 // |
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28 //####COPYRIGHTEND#### |
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29 //========================================================================== |
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30 //#####DESCRIPTIONBEGIN#### |
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31 // |
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32 // Author(s): nickg |
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33 // Contributors: nickg |
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34 // Date: 1997-09-24 |
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35 // Purpose: Cyg_Binary_Semaphore implementation |
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36 // Description: This file contains the implementations of the binary semaphore |
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37 // class. |
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38 // |
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39 //####DESCRIPTIONEND#### |
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40 // |
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41 //========================================================================== |
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42 |
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43 #include <pkgconf/kernel.h> |
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44 |
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45 #include <cyg/kernel/ktypes.h> // base kernel types |
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46 #include <cyg/infra/cyg_trac.h> // tracing macros |
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47 #include <cyg/infra/cyg_ass.h> // assertion macros |
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48 #include <cyg/kernel/instrmnt.h> // instrumentation |
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49 |
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50 #include <cyg/kernel/thread.inl> // Cyg_Thread inlines |
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51 |
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52 #include <cyg/kernel/sema.hxx> // our header |
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53 |
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54 #include <cyg/kernel/sched.inl> // scheduler inlines |
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55 |
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56 // ------------------------------------------------------------------------- |
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57 |
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58 Cyg_Binary_Semaphore::Cyg_Binary_Semaphore ( |
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59 cyg_bool init_state |
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60 ) |
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61 { |
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62 state = init_state; |
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63 } |
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64 |
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65 // ------------------------------------------------------------------------- |
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66 |
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67 Cyg_Binary_Semaphore::~Cyg_Binary_Semaphore ( ) |
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68 { |
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69 } |
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70 |
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71 // ------------------------------------------------------------------------- |
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72 |
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73 cyg_bool Cyg_Binary_Semaphore::wait() |
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74 { |
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75 cyg_bool result = true; |
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76 Cyg_Thread *self = Cyg_Thread::self(); |
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77 |
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78 // Prevent preemption |
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79 Cyg_Scheduler::lock(); |
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80 |
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81 CYG_INSTRUMENT_BINSEM( CLAIM, this, state ); |
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82 |
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83 while( !state && result ) |
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84 { |
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85 self->set_sleep_reason( Cyg_Thread::WAIT ); |
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86 |
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87 self->sleep(); |
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88 |
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89 queue.enqueue( self ); |
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90 |
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91 CYG_INSTRUMENT_BINSEM( WAIT, this, 0 ); |
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92 |
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93 CYG_ASSERT( Cyg_Scheduler::get_sched_lock() == 1, "Called with non-zero scheduler lock"); |
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94 |
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95 Cyg_Scheduler::unlock(); |
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96 Cyg_Scheduler::lock(); |
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97 |
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98 CYG_INSTRUMENT_BINSEM( WOKE, this, state ); |
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99 |
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100 switch( self->get_wake_reason() ) |
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101 { |
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102 case Cyg_Thread::DESTRUCT: |
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103 case Cyg_Thread::BREAK: |
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104 result = false; |
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105 break; |
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106 |
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107 case Cyg_Thread::EXIT: |
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108 self->exit(); |
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109 break; |
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110 |
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111 default: |
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112 break; |
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113 } |
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114 |
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115 } |
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116 |
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117 if( result ) state = false; |
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118 |
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119 // Unlock the scheduler and maybe switch threads |
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120 Cyg_Scheduler::unlock(); |
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121 |
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122 return result; |
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123 } |
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124 |
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125 // ------------------------------------------------------------------------- |
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126 |
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127 cyg_bool Cyg_Binary_Semaphore::trywait() |
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128 { |
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129 cyg_bool result = true; |
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130 |
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131 // Prevent preemption |
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132 Cyg_Scheduler::lock(); |
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133 |
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134 if( state ) state = false; |
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135 else result = false; |
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136 |
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137 CYG_INSTRUMENT_BINSEM( TRY, this, result ); |
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138 |
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139 // Unlock the scheduler and maybe switch threads |
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140 Cyg_Scheduler::unlock(); |
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141 |
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142 return result; |
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143 } |
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144 |
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145 // ------------------------------------------------------------------------- |
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146 |
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147 void Cyg_Binary_Semaphore::post() |
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148 { |
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149 // Prevent preemption |
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150 Cyg_Scheduler::lock(); |
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151 |
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152 CYG_INSTRUMENT_BINSEM( POST, this, 0 ); |
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153 |
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154 state = true; |
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155 |
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156 if( !queue.empty() ) { |
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157 |
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158 // The queue is non-empty, so grab the next |
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159 // thread from it and wake it up. The waiter |
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160 // will clear the flag. |
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161 |
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162 Cyg_Thread *thread = queue.dequeue(); |
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163 |
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164 thread->set_wake_reason( Cyg_Thread::DONE ); |
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165 |
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166 thread->wake(); |
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167 |
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168 CYG_INSTRUMENT_BINSEM( WAKE, this, thread ); |
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169 } |
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170 |
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171 // Unlock the scheduler and maybe switch threads |
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172 Cyg_Scheduler::unlock(); |
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173 |
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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 cyg_bool Cyg_Binary_Semaphore::posted() |
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179 { |
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180 // This is a single read of the value of state. |
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181 // This is already atomic, hence there is no need |
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182 // to lock the scheduler. |
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183 |
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184 return state; |
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185 } |
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186 |
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187 // ------------------------------------------------------------------------- |
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188 // EOF sync/bin_sem.cxx |
