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1 //========================================================================== |
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2 // |
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3 // sync/mutex.cxx |
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4 // |
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5 // Mutex and condition variable 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, jlarmour |
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34 // Date: 1999-02-17 |
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35 // Purpose: Mutex implementation |
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36 // Description: This file contains the implementations of the mutex |
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37 // and condition variable classes. |
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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/mutex.hxx> // our header |
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51 |
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52 #include <cyg/kernel/thread.inl> // thread inlines |
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53 #include <cyg/kernel/sched.inl> // scheduler inlines |
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54 #include <cyg/kernel/clock.inl> // clock inlines |
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55 |
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56 |
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57 // ------------------------------------------------------------------------- |
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58 // Constructor |
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59 |
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60 Cyg_Mutex::Cyg_Mutex() |
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61 { |
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62 CYG_REPORT_FUNCTION(); |
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63 |
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64 locked = false; |
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65 owner = NULL; |
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66 |
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67 CYG_REPORT_RETURN(); |
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68 } |
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69 |
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70 // ------------------------------------------------------------------------- |
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71 // Destructor |
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72 |
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73 Cyg_Mutex::~Cyg_Mutex() |
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74 { |
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75 CYG_REPORT_FUNCTION(); |
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76 |
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77 CYG_ASSERT( owner == NULL, "Deleting mutex with owner"); |
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78 CYG_ASSERT( queue.empty(), "Deleting mutex with waiting threads"); |
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79 CYG_REPORT_RETURN(); |
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80 } |
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81 |
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82 // ------------------------------------------------------------------------- |
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83 |
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84 #ifdef CYGDBG_USE_ASSERTS |
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85 |
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86 bool |
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87 Cyg_Mutex::check_this( cyg_assert_class_zeal zeal) const |
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88 { |
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89 // CYG_REPORT_FUNCTION(); |
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90 |
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91 // check that we have a non-NULL pointer first |
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92 if( this == NULL ) return false; |
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93 |
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94 switch( zeal ) |
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95 { |
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96 case cyg_system_test: |
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97 case cyg_extreme: |
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98 case cyg_thorough: |
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99 case cyg_quick: |
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100 case cyg_trivial: |
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101 if( locked && owner == NULL ) return false; |
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102 if( !locked && owner != NULL ) return false; |
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103 case cyg_none: |
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104 default: |
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105 break; |
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106 }; |
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107 |
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108 return true; |
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109 } |
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110 |
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111 #endif |
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112 |
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113 // ------------------------------------------------------------------------- |
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114 // Lock and/or wait |
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115 |
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116 cyg_bool |
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117 Cyg_Mutex::lock(void) |
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118 { |
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119 CYG_REPORT_FUNCTYPE("returning %d"); |
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120 |
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121 cyg_bool result = true; |
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122 Cyg_Thread *self = Cyg_Thread::self(); |
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123 |
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124 // Prevent preemption |
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125 Cyg_Scheduler::lock(); |
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126 |
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127 CYG_ASSERTCLASS( this, "Bad this pointer"); |
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128 |
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129 CYG_INSTRUMENT_MUTEX(LOCK, this, 0); |
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130 |
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131 // Loop while the mutex is locked, sleeping each time around |
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132 // the loop. This copes with the possibility of a higher priority |
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133 // thread grabbing the mutex between the wakeup in unlock() and |
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134 // this thread actually starting. |
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135 |
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136 while( locked && result ) |
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137 { |
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138 CYG_ASSERT( self != owner, "Locking mutex I already own"); |
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139 |
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140 self->set_sleep_reason( Cyg_Thread::WAIT ); |
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141 |
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142 self->sleep(); |
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143 |
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144 queue.enqueue( self ); |
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145 |
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146 #ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INHERITANCE |
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147 |
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148 owner->inherit_priority(self); |
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149 |
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150 #endif |
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151 |
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152 CYG_INSTRUMENT_MUTEX(WAIT, this, 0); |
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153 |
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154 CYG_ASSERT( Cyg_Scheduler::get_sched_lock() == 1, "Called with non-zero scheduler lock"); |
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155 |
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156 // Unlock scheduler and allow other threads |
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157 // to run |
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158 Cyg_Scheduler::unlock(); |
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159 Cyg_Scheduler::lock(); |
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160 |
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161 CYG_ASSERTCLASS( this, "Bad this pointer"); |
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162 |
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163 switch( self->get_wake_reason() ) |
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164 { |
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165 case Cyg_Thread::DESTRUCT: |
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166 case Cyg_Thread::BREAK: |
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167 result = false; |
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168 break; |
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169 |
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170 case Cyg_Thread::EXIT: |
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171 self->exit(); |
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172 break; |
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173 |
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174 default: |
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175 break; |
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176 } |
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177 |
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178 } |
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179 |
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180 if( result ) |
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181 { |
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182 locked = true; |
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183 owner = self; |
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184 |
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185 #ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INHERITANCE |
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186 |
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187 self->count_mutex(); |
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188 |
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189 #endif |
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190 |
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191 CYG_INSTRUMENT_MUTEX(LOCKED, this, 0); |
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192 } |
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193 |
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194 // Unlock the scheduler and maybe switch threads |
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195 Cyg_Scheduler::unlock(); |
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196 |
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197 CYG_ASSERTCLASS( this, "Bad this pointer"); |
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198 |
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199 CYG_REPORT_RETVAL(result); |
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200 |
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201 return result; |
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202 } |
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203 |
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204 // ------------------------------------------------------------------------- |
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205 // Try to lock and return success |
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206 |
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207 cyg_bool |
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208 Cyg_Mutex::trylock(void) |
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209 { |
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210 CYG_REPORT_FUNCTYPE("returning %d"); |
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211 |
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212 CYG_ASSERTCLASS( this, "Bad this pointer"); |
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213 |
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214 cyg_bool result = true; |
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215 |
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216 // Prevent preemption |
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217 Cyg_Scheduler::lock(); |
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218 |
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219 // If the mutex is not locked, grab it |
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220 // for ourself. Otherwise return failure. |
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221 if( !locked ) |
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222 { |
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223 Cyg_Thread *self = Cyg_Thread::self(); |
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224 |
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225 locked = true; |
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226 owner = self; |
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227 |
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228 #ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INHERITANCE |
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229 |
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230 self->count_mutex(); |
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231 |
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232 #endif |
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233 } |
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234 else result = false; |
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235 |
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236 CYG_INSTRUMENT_MUTEX(TRY, this, result); |
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237 |
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238 // Unlock the scheduler and maybe switch threads |
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239 Cyg_Scheduler::unlock(); |
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240 |
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241 CYG_REPORT_RETVAL(result); |
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242 return result; |
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243 } |
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244 |
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245 // ------------------------------------------------------------------------- |
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246 // unlock |
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247 |
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248 void |
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249 Cyg_Mutex::unlock(void) |
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250 { |
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251 CYG_REPORT_FUNCTION(); |
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252 |
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253 // Prevent preemption |
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254 Cyg_Scheduler::lock(); |
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255 |
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256 CYG_INSTRUMENT_MUTEX(UNLOCK, this, 0); |
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257 |
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258 CYG_ASSERTCLASS( this, "Bad this pointer"); |
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259 CYG_ASSERT( locked, "Unlock mutex that is not locked"); |
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260 CYG_ASSERT( owner == Cyg_Thread::self(), "Unlock mutex I do not own"); |
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261 |
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262 #ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INHERITANCE |
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263 |
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264 owner->uncount_mutex(); |
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265 owner->disinherit_priority(); |
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266 |
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267 #endif |
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268 |
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269 locked = false; |
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270 owner = NULL; |
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271 |
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272 if( !queue.empty() ) { |
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273 |
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274 // The queue is non-empty, so grab the next |
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275 // thread from it and wake it up. |
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276 |
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277 Cyg_Thread *thread = queue.dequeue(); |
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278 |
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279 CYG_ASSERTCLASS( thread, "Bad thread pointer"); |
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280 |
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281 thread->set_wake_reason( Cyg_Thread::DONE ); |
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282 |
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283 thread->wake(); |
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284 |
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285 CYG_INSTRUMENT_MUTEX(WAKE, this, thread); |
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286 |
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287 } |
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288 |
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289 CYG_ASSERTCLASS( this, "Bad this pointer"); |
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290 |
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291 // Unlock the scheduler and maybe switch threads |
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292 Cyg_Scheduler::unlock(); |
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293 |
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294 CYG_REPORT_RETURN(); |
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295 } |
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296 |
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297 // ------------------------------------------------------------------------- |
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298 // Release all waiting threads. |
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299 |
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300 void Cyg_Mutex::release() |
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301 { |
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302 CYG_REPORT_FUNCTION(); |
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303 |
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304 // Prevent preemption |
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305 Cyg_Scheduler::lock(); |
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306 |
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307 CYG_INSTRUMENT_MUTEX(RELEASE, this, 0); |
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308 |
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309 CYG_ASSERTCLASS( this, "Bad this pointer"); |
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310 |
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311 while( !queue.empty() ) |
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312 { |
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313 // The queue is non-empty, so grab each |
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314 // thread from it and release it. |
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315 |
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316 Cyg_Thread *thread = queue.dequeue(); |
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317 |
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318 CYG_ASSERTCLASS( thread, "Bad thread pointer"); |
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319 |
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320 thread->release(); |
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321 |
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322 CYG_INSTRUMENT_MUTEX(RELEASED, this, thread); |
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323 |
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324 } |
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325 |
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326 CYG_ASSERTCLASS( this, "Bad this pointer"); |
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327 |
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328 // Unlock the scheduler and maybe switch threads |
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329 Cyg_Scheduler::unlock(); |
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330 |
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331 CYG_REPORT_RETURN(); |
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332 } |
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333 |
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334 //========================================================================== |
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335 // Condition variables |
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336 |
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337 Cyg_Condition_Variable::Cyg_Condition_Variable( |
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338 Cyg_Mutex &mx // linked mutex |
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339 ) |
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340 { |
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341 CYG_REPORT_FUNCTION(); |
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342 |
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343 mutex = &mx; |
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344 |
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345 CYG_ASSERTCLASS( mutex, "Invalid mutex argument"); |
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346 |
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347 CYG_REPORT_RETURN(); |
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348 } |
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349 |
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350 // ------------------------------------------------------------------------- |
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351 // Destructor |
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352 |
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353 Cyg_Condition_Variable::~Cyg_Condition_Variable() |
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354 { |
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355 CYG_REPORT_FUNCTION(); |
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356 |
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357 CYG_ASSERT( queue.empty(), "Deleting condvar with waiting threads"); |
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358 |
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359 CYG_REPORT_RETURN(); |
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360 } |
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361 |
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362 // ------------------------------------------------------------------------- |
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363 |
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364 #ifdef CYGDBG_USE_ASSERTS |
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365 |
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366 bool |
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367 Cyg_Condition_Variable::check_this( cyg_assert_class_zeal zeal) const |
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368 { |
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369 bool result = true; |
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370 |
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371 CYG_REPORT_FUNCTYPE("returning %d"); |
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372 CYG_REPORT_FUNCARG1("zeal = %d", zeal); |
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373 |
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374 // check that we have a non-NULL pointer first |
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375 if( this == NULL ) |
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376 result = false; |
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377 else { |
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378 |
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379 switch( zeal ) |
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380 { |
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381 case cyg_system_test: |
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382 case cyg_extreme: |
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383 case cyg_thorough: |
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384 if( !mutex->check_this(zeal) ) |
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385 result = false; |
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386 case cyg_quick: |
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387 case cyg_trivial: |
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388 case cyg_none: |
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389 default: |
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390 break; |
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391 } |
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392 } |
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393 |
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394 CYG_REPORT_RETVAL(result); |
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395 return result; |
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396 } |
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397 |
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398 #endif |
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399 |
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400 // ------------------------------------------------------------------------- |
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401 // Wait for condition to be true |
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402 // Note: if this function is entered with the scheduler locked (e.g. to |
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403 // suspend DSR processing) then there is no need to take the lock. Also |
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404 // in this case, exit with the scheduler locked, which allows this function |
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405 // to be used in a totally thread-safe manner. |
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406 |
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407 void |
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408 Cyg_Condition_Variable::wait(void) |
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409 { |
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410 CYG_REPORT_FUNCTION(); |
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411 |
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412 Cyg_Thread *self = Cyg_Thread::self(); |
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413 |
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414 cyg_int32 current_lock = Cyg_Scheduler::get_sched_lock(); |
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415 |
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416 if (current_lock == 0) |
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417 // Prevent preemption |
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418 Cyg_Scheduler::lock(); |
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419 |
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420 CYG_ASSERTCLASS( this, "Bad this pointer"); |
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421 CYG_ASSERTCLASS( mutex, "Corrupt mutex"); |
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422 CYG_ASSERTCLASS( self, "Bad self thread"); |
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423 |
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424 CYG_INSTRUMENT_CONDVAR(WAIT, this, 0); |
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425 |
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426 mutex->unlock(); |
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427 |
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428 self->set_sleep_reason( Cyg_Thread::WAIT ); |
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429 |
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430 self->sleep(); |
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431 |
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432 queue.enqueue( self ); |
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433 |
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434 CYG_ASSERT( Cyg_Scheduler::get_sched_lock() == 1, "Called with non-zero scheduler lock"); |
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435 |
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436 // Unlock the scheduler and switch threads |
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437 Cyg_Scheduler::unlock(); |
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438 |
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439 CYG_INSTRUMENT_CONDVAR(WOKE, this, self->get_wake_reason()); |
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440 |
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441 CYG_ASSERTCLASS( this, "Bad this pointer"); |
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442 CYG_ASSERTCLASS( mutex, "Corrupt mutex"); |
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443 |
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444 switch( self->get_wake_reason() ) |
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445 { |
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446 case Cyg_Thread::EXIT: |
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447 self->exit(); |
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448 break; |
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449 |
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450 default: |
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451 break; |
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452 } |
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453 |
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454 |
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455 // When we awake, we must re-acquire the mutex. Note that while |
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456 // it is essential to release the mutex and queue on the CV |
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457 // atomically relative to other threads, to avoid races, it is not |
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458 // necessary for us to re-acquire the mutex in the same atomic |
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459 // action. Hence we can do it after unlocking the scheduler. |
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460 // We need to loop here in case the thread is released while waiting |
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461 // for the mutex. It is essential that we exit this function with the |
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462 // mutex claimed. |
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463 |
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464 while ( !mutex->lock() ) |
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465 continue; |
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466 |
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467 CYG_ASSERTCLASS( this, "Bad this pointer"); |
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468 CYG_ASSERTCLASS( mutex, "Corrupt mutex"); |
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469 CYG_ASSERT( mutex->owner == self, "Not mutex owner"); |
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470 |
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471 CYG_REPORT_RETURN(); |
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472 |
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473 if (current_lock) |
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474 // Reacquire the DSR pseudo lock |
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475 Cyg_Scheduler::lock(); |
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476 } |
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477 |
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478 // ------------------------------------------------------------------------- |
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479 // Wake one thread |
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480 |
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2
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481 void |
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482 Cyg_Condition_Variable::signal(void) |
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483 { |
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484 CYG_REPORT_FUNCTION(); |
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485 |
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486 CYG_ASSERTCLASS( this, "Bad this pointer"); |
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487 CYG_ASSERTCLASS( mutex, "Corrupt mutex"); |
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488 |
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489 // Prevent preemption |
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490 Cyg_Scheduler::lock(); |
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491 |
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492 CYG_INSTRUMENT_CONDVAR(SIGNAL, this, 0); |
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493 |
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494 if( !queue.empty() ) |
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495 { |
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496 // The queue is non-empty, so grab the next |
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497 // thread from it and wake it up. |
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498 |
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499 Cyg_Thread *thread = queue.dequeue(); |
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500 |
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501 CYG_ASSERTCLASS( thread, "Bad thread pointer"); |
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502 |
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503 thread->set_wake_reason( Cyg_Thread::DONE ); |
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504 |
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505 thread->wake(); |
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506 |
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507 CYG_INSTRUMENT_CONDVAR(WAKE, this, thread); |
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508 |
|
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509 } |
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510 |
|
|
511 CYG_ASSERTCLASS( this, "Bad this pointer"); |
|
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512 CYG_ASSERTCLASS( mutex, "Corrupt mutex"); |
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513 |
|
|
514 // Unlock the scheduler and maybe switch threads |
|
|
515 Cyg_Scheduler::unlock(); |
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516 |
|
2
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517 CYG_REPORT_RETURN(); |
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0
|
518 } |
|
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519 |
|
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520 // ------------------------------------------------------------------------- |
|
|
521 // Set cond true, wake all threads |
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|
522 |
|
2
|
523 void |
|
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524 Cyg_Condition_Variable::broadcast(void) |
|
0
|
525 { |
|
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526 CYG_REPORT_FUNCTION(); |
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527 |
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528 CYG_ASSERTCLASS( this, "Bad this pointer"); |
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529 CYG_ASSERTCLASS( mutex, "Corrupt mutex"); |
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530 |
|
|
531 // Prevent preemption |
|
|
532 Cyg_Scheduler::lock(); |
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|
533 |
|
|
534 CYG_INSTRUMENT_CONDVAR(BROADCAST, this, 0); |
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535 |
|
|
536 // Grab all the threads from the queue and let them |
|
|
537 // go. |
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538 |
|
|
539 while( !queue.empty() ) |
|
|
540 { |
|
|
541 Cyg_Thread *thread = queue.dequeue(); |
|
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542 |
|
|
543 CYG_ASSERTCLASS( thread, "Bad thread pointer"); |
|
|
544 |
|
|
545 thread->set_wake_reason( Cyg_Thread::DONE ); |
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546 |
|
|
547 thread->wake(); |
|
|
548 |
|
|
549 CYG_INSTRUMENT_CONDVAR(WAKE, this, thread); |
|
|
550 } |
|
|
551 |
|
|
552 CYG_ASSERTCLASS( this, "Bad this pointer"); |
|
|
553 CYG_ASSERTCLASS( mutex, "Corrupt mutex"); |
|
|
554 |
|
|
555 // Unlock the scheduler and maybe switch threads |
|
|
556 Cyg_Scheduler::unlock(); |
|
2
|
557 |
|
|
558 CYG_REPORT_RETURN(); |
|
0
|
559 } |
|
|
560 |
|
|
561 // ------------------------------------------------------------------------- |
|
|
562 // Optional timed wait on a CV |
|
|
563 |
|
2
|
564 #if defined(CYGMFN_KERNEL_SYNCH_CONDVAR_TIMED_WAIT) |
|
0
|
565 |
|
2
|
566 cyg_bool |
|
|
567 Cyg_Condition_Variable::wait( cyg_tick_count timeout ) |
|
0
|
568 { |
|
2
|
569 CYG_REPORT_FUNCTYPE("returning %d"); |
|
|
570 CYG_REPORT_FUNCARG1("timeout = %d", timeout); |
|
0
|
571 |
|
|
572 CYG_ASSERTCLASS( this, "Bad this pointer"); |
|
|
573 CYG_ASSERTCLASS( mutex, "Corrupt mutex"); |
|
|
574 |
|
|
575 cyg_bool result = true; |
|
|
576 |
|
|
577 Cyg_Thread *self = Cyg_Thread::self(); |
|
|
578 |
|
|
579 CYG_ASSERTCLASS( self, "Bad self thread"); |
|
|
580 |
|
|
581 // Prevent preemption |
|
|
582 Cyg_Scheduler::lock(); |
|
|
583 |
|
|
584 CYG_INSTRUMENT_CONDVAR(TIMED_WAIT, this, 0 ); |
|
|
585 |
|
|
586 mutex->unlock(); |
|
|
587 |
|
|
588 // The ordering of sleep() and set_timer() here are |
|
|
589 // important. If the timeout is in the past, the thread |
|
|
590 // will be woken up immediately and will not sleep. |
|
|
591 |
|
|
592 self->sleep(); |
|
|
593 |
|
|
594 // Set the timer and sleep reason |
|
|
595 self->set_timer( timeout, Cyg_Thread::TIMEOUT ); |
|
|
596 |
|
|
597 // Only enqueue if the timeout has not already fired. |
|
|
598 if( self->get_wake_reason() == Cyg_Thread::NONE ) |
|
|
599 queue.enqueue( self ); |
|
|
600 |
|
|
601 CYG_ASSERT( Cyg_Scheduler::get_sched_lock() == 1, "Called with non-zero scheduler lock"); |
|
|
602 |
|
|
603 // Unlock the scheduler and switch threads |
|
|
604 Cyg_Scheduler::unlock(); |
|
|
605 |
|
|
606 CYG_ASSERTCLASS( this, "Bad this pointer"); |
|
|
607 CYG_ASSERTCLASS( mutex, "Corrupt mutex"); |
|
|
608 |
|
|
609 self->clear_timer(); |
|
|
610 |
|
|
611 CYG_INSTRUMENT_CONDVAR(WOKE, this, self->get_wake_reason()); |
|
|
612 |
|
|
613 switch( self->get_wake_reason() ) |
|
|
614 { |
|
|
615 case Cyg_Thread::TIMEOUT: |
|
|
616 case Cyg_Thread::DESTRUCT: // which, the cv or the mutex? |
|
|
617 case Cyg_Thread::BREAK: |
|
|
618 result = false; |
|
|
619 break; |
|
|
620 |
|
|
621 case Cyg_Thread::EXIT: |
|
|
622 self->exit(); |
|
|
623 break; |
|
|
624 |
|
|
625 default: |
|
|
626 break; |
|
|
627 } |
|
|
628 |
|
|
629 |
|
|
630 // When we awake, we must re-acquire the mutex. Note that while |
|
|
631 // it is essential to release the mutex and queue on the CV |
|
|
632 // atomically relative to other threads, to avoid races, it is not |
|
|
633 // necessary for us to re-acquire the mutex in the same atomic |
|
|
634 // action. Hence we can do it after unlocking the scheduler. |
|
|
635 |
|
2
|
636 // FIXME: what if we woke up above due to TIMEOUT/DESTRUCT/BREAK? |
|
|
637 // In that situation is it correct to not lock the mutex? |
|
|
638 if (false != result) |
|
|
639 result = mutex->lock(); |
|
0
|
640 |
|
|
641 CYG_ASSERTCLASS( this, "Bad this pointer"); |
|
|
642 CYG_ASSERTCLASS( mutex, "Corrupt mutex"); |
|
2
|
643 |
|
|
644 CYG_REPORT_RETVAL(result); |
|
0
|
645 |
|
|
646 return result; |
|
|
647 } |
|
|
648 |
|
|
649 #endif |
|
|
650 |
|
|
651 |
|
|
652 // ------------------------------------------------------------------------- |
|
|
653 // EOF sync/mutex.cxx |
