1 | /** |
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2 | * @file |
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3 | * |
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4 | * @brief Surrender the Mutex |
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5 | * @ingroup ScoreMutex |
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6 | */ |
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7 | |
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8 | /* |
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9 | * COPYRIGHT (c) 1989-2006. |
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10 | * On-Line Applications Research Corporation (OAR). |
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11 | * |
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12 | * The license and distribution terms for this file may be |
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13 | * found in the file LICENSE in this distribution or at |
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14 | * http://www.rtems.org/license/LICENSE. |
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15 | */ |
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16 | |
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17 | #if HAVE_CONFIG_H |
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18 | #include "config.h" |
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19 | #endif |
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20 | |
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21 | #include <rtems/system.h> |
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22 | #include <rtems/score/isr.h> |
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23 | #include <rtems/score/coremuteximpl.h> |
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24 | #include <rtems/score/thread.h> |
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25 | |
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26 | CORE_mutex_Status _CORE_mutex_Do_surrender( |
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27 | CORE_mutex_Control *the_mutex, |
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28 | #if defined(RTEMS_MULTIPROCESSING) |
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29 | Thread_queue_MP_callout mp_callout, |
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30 | #endif |
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31 | ISR_lock_Context *lock_context |
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32 | ) |
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33 | { |
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34 | Thread_Control *the_thread; |
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35 | Thread_Control *holder; |
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36 | |
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37 | holder = the_mutex->holder; |
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38 | |
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39 | /* |
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40 | * The following code allows a thread (or ISR) other than the thread |
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41 | * which acquired the mutex to release that mutex. This is only |
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42 | * allowed when the mutex in quetion is FIFO or simple Priority |
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43 | * discipline. But Priority Ceiling or Priority Inheritance mutexes |
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44 | * must be released by the thread which acquired them. |
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45 | */ |
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46 | |
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47 | if ( the_mutex->Attributes.only_owner_release ) { |
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48 | if ( !_Thread_Is_executing( holder ) ) { |
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49 | _ISR_lock_ISR_enable( lock_context ); |
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50 | return CORE_MUTEX_STATUS_NOT_OWNER_OF_RESOURCE; |
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51 | } |
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52 | } |
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53 | |
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54 | _Thread_queue_Acquire_critical( &the_mutex->Wait_queue, lock_context ); |
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55 | |
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56 | /* XXX already unlocked -- not right status */ |
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57 | |
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58 | if ( !the_mutex->nest_count ) { |
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59 | _Thread_queue_Release( &the_mutex->Wait_queue, lock_context ); |
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60 | return CORE_MUTEX_STATUS_SUCCESSFUL; |
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61 | } |
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62 | |
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63 | the_mutex->nest_count--; |
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64 | |
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65 | if ( the_mutex->nest_count != 0 ) { |
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66 | /* |
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67 | * All error checking is on the locking side, so if the lock was |
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68 | * allowed to acquired multiple times, then we should just deal with |
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69 | * that. The RTEMS_DEBUG is just a validation. |
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70 | */ |
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71 | #if defined(RTEMS_DEBUG) |
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72 | switch ( the_mutex->Attributes.lock_nesting_behavior ) { |
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73 | case CORE_MUTEX_NESTING_ACQUIRES: |
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74 | _Thread_queue_Release( &the_mutex->Wait_queue, lock_context ); |
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75 | return CORE_MUTEX_STATUS_SUCCESSFUL; |
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76 | #if defined(RTEMS_POSIX_API) |
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77 | case CORE_MUTEX_NESTING_IS_ERROR: |
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78 | /* should never occur */ |
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79 | _Thread_queue_Release( &the_mutex->Wait_queue, lock_context ); |
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80 | return CORE_MUTEX_STATUS_NESTING_NOT_ALLOWED; |
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81 | #endif |
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82 | case CORE_MUTEX_NESTING_BLOCKS: |
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83 | /* Currently no API exercises this behavior. */ |
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84 | break; |
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85 | } |
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86 | #else |
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87 | _Thread_queue_Release( &the_mutex->Wait_queue, lock_context ); |
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88 | /* must be CORE_MUTEX_NESTING_ACQUIRES or we wouldn't be here */ |
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89 | return CORE_MUTEX_STATUS_SUCCESSFUL; |
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90 | #endif |
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91 | } |
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92 | |
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93 | /* |
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94 | * Formally release the mutex before possibly transferring it to a |
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95 | * blocked thread. |
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96 | */ |
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97 | if ( _CORE_mutex_Is_inherit_priority( &the_mutex->Attributes ) || |
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98 | _CORE_mutex_Is_priority_ceiling( &the_mutex->Attributes ) ) { |
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99 | holder->resource_count--; |
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100 | } |
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101 | the_mutex->holder = NULL; |
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102 | |
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103 | /* |
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104 | * Now we check if another thread was waiting for this mutex. If so, |
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105 | * transfer the mutex to that thread. |
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106 | */ |
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107 | if ( |
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108 | ( the_thread = _Thread_queue_First_locked( |
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109 | &the_mutex->Wait_queue, |
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110 | the_mutex->operations |
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111 | ) |
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112 | ) |
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113 | ) { |
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114 | bool unblock; |
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115 | |
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116 | the_mutex->holder = the_thread; |
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117 | the_mutex->nest_count = 1; |
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118 | |
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119 | /* |
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120 | * We must extract the thread now since this will restore its default |
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121 | * thread lock. This is necessary to avoid a deadlock in the |
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122 | * _Thread_Change_priority() below due to a recursive thread queue lock |
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123 | * acquire. |
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124 | */ |
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125 | unblock = _Thread_queue_Extract_locked( |
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126 | &the_mutex->Wait_queue.Queue, |
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127 | the_mutex->operations, |
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128 | the_thread, |
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129 | mp_callout |
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130 | ); |
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131 | |
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132 | #if defined(RTEMS_MULTIPROCESSING) |
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133 | if ( _Objects_Is_local_id( the_thread->Object.id ) ) |
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134 | #endif |
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135 | { |
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136 | switch ( the_mutex->Attributes.discipline ) { |
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137 | case CORE_MUTEX_DISCIPLINES_FIFO: |
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138 | case CORE_MUTEX_DISCIPLINES_PRIORITY: |
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139 | break; |
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140 | case CORE_MUTEX_DISCIPLINES_PRIORITY_INHERIT: |
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141 | the_thread->resource_count++; |
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142 | _Thread_queue_Boost_priority( &the_mutex->Wait_queue.Queue, the_thread ); |
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143 | break; |
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144 | case CORE_MUTEX_DISCIPLINES_PRIORITY_CEILING: |
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145 | the_thread->resource_count++; |
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146 | _Thread_Raise_priority( |
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147 | the_thread, |
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148 | the_mutex->Attributes.priority_ceiling |
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149 | ); |
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150 | break; |
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151 | } |
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152 | } |
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153 | |
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154 | _Thread_queue_Unblock_critical( |
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155 | unblock, |
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156 | &the_mutex->Wait_queue.Queue, |
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157 | the_thread, |
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158 | lock_context |
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159 | ); |
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160 | } else { |
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161 | _Thread_queue_Release( &the_mutex->Wait_queue, lock_context ); |
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162 | } |
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163 | |
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164 | /* |
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165 | * Whether or not someone is waiting for the mutex, an |
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166 | * inherited priority must be lowered if this is the last |
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167 | * mutex (i.e. resource) this task has. |
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168 | */ |
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169 | if ( !_Thread_Owns_resources( holder ) ) { |
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170 | /* |
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171 | * Ensure that the holder resource count is visible to all other processors |
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172 | * and that we read the latest priority restore hint. |
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173 | */ |
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174 | _Atomic_Fence( ATOMIC_ORDER_ACQ_REL ); |
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175 | |
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176 | if ( holder->priority_restore_hint ) { |
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177 | Per_CPU_Control *cpu_self; |
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178 | |
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179 | cpu_self = _Thread_Dispatch_disable(); |
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180 | _Thread_Restore_priority( holder ); |
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181 | _Thread_Dispatch_enable( cpu_self ); |
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182 | } |
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183 | } |
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184 | |
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185 | return CORE_MUTEX_STATUS_SUCCESSFUL; |
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186 | } |
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