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 | #ifdef __RTEMS_STRICT_ORDER_MUTEX__ |
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27 | static inline void _CORE_mutex_Push_priority( |
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28 | CORE_mutex_Control *mutex, |
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29 | Thread_Control *thread |
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30 | ) |
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31 | { |
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32 | _Chain_Prepend_unprotected( |
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33 | &thread->lock_mutex, |
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34 | &mutex->queue.lock_queue |
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35 | ); |
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36 | mutex->queue.priority_before = thread->current_priority; |
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37 | } |
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38 | |
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39 | static inline CORE_mutex_Status _CORE_mutex_Pop_priority( |
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40 | CORE_mutex_Control *mutex, |
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41 | Thread_Control *holder |
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42 | ) |
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43 | { |
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44 | /* |
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45 | * Check whether the holder release the mutex in LIFO order if not return |
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46 | * error code. |
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47 | */ |
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48 | if ( _Chain_First( &holder->lock_mutex ) != &mutex->queue.lock_queue ) { |
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49 | mutex->nest_count++; |
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50 | |
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51 | return CORE_MUTEX_RELEASE_NOT_ORDER; |
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52 | } |
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53 | |
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54 | /* |
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55 | * This pops the first node from the list. |
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56 | */ |
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57 | _Chain_Get_first_unprotected( &holder->lock_mutex ); |
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58 | |
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59 | if ( mutex->queue.priority_before != holder->current_priority ) |
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60 | _Thread_Change_priority( holder, mutex->queue.priority_before, true ); |
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61 | |
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62 | return CORE_MUTEX_STATUS_SUCCESSFUL; |
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63 | } |
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64 | #else |
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65 | #define _CORE_mutex_Push_priority( mutex, thread ) ((void) 0) |
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66 | |
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67 | #define _CORE_mutex_Pop_priority( mutex, thread ) \ |
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68 | CORE_MUTEX_STATUS_SUCCESSFUL |
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69 | #endif |
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70 | |
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71 | /* |
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72 | * _CORE_mutex_Surrender |
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73 | * |
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74 | * This routine frees a unit to the mutex. If a task was blocked waiting for |
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75 | * a unit from this mutex, then that task will be readied and the unit |
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76 | * given to that task. Otherwise, the unit will be returned to the mutex. |
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77 | * |
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78 | * Input parameters: |
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79 | * the_mutex - the mutex to be flushed |
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80 | * id - id of parent mutex |
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81 | * api_mutex_mp_support - api dependent MP support actions |
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82 | * |
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83 | * Output parameters: |
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84 | * CORE_MUTEX_STATUS_SUCCESSFUL - if successful |
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85 | * core error code - if unsuccessful |
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86 | */ |
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87 | |
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88 | CORE_mutex_Status _CORE_mutex_Surrender( |
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89 | CORE_mutex_Control *the_mutex, |
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90 | #if defined(RTEMS_MULTIPROCESSING) |
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91 | Objects_Id id, |
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92 | CORE_mutex_API_mp_support_callout api_mutex_mp_support, |
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93 | #else |
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94 | Objects_Id id RTEMS_UNUSED, |
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95 | CORE_mutex_API_mp_support_callout api_mutex_mp_support RTEMS_UNUSED, |
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96 | #endif |
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97 | ISR_lock_Context *lock_context |
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98 | ) |
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99 | { |
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100 | Thread_Control *the_thread; |
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101 | Thread_Control *holder; |
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102 | |
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103 | holder = the_mutex->holder; |
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104 | |
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105 | /* |
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106 | * The following code allows a thread (or ISR) other than the thread |
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107 | * which acquired the mutex to release that mutex. This is only |
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108 | * allowed when the mutex in quetion is FIFO or simple Priority |
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109 | * discipline. But Priority Ceiling or Priority Inheritance mutexes |
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110 | * must be released by the thread which acquired them. |
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111 | */ |
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112 | |
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113 | if ( the_mutex->Attributes.only_owner_release ) { |
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114 | if ( !_Thread_Is_executing( holder ) ) { |
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115 | _ISR_lock_ISR_enable( lock_context ); |
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116 | return CORE_MUTEX_STATUS_NOT_OWNER_OF_RESOURCE; |
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117 | } |
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118 | } |
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119 | |
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120 | _Thread_queue_Acquire_critical( &the_mutex->Wait_queue, lock_context ); |
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121 | |
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122 | /* XXX already unlocked -- not right status */ |
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123 | |
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124 | if ( !the_mutex->nest_count ) { |
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125 | _Thread_queue_Release( &the_mutex->Wait_queue, lock_context ); |
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126 | return CORE_MUTEX_STATUS_SUCCESSFUL; |
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127 | } |
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128 | |
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129 | the_mutex->nest_count--; |
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130 | |
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131 | if ( the_mutex->nest_count != 0 ) { |
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132 | /* |
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133 | * All error checking is on the locking side, so if the lock was |
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134 | * allowed to acquired multiple times, then we should just deal with |
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135 | * that. The RTEMS_DEBUG is just a validation. |
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136 | */ |
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137 | #if defined(RTEMS_DEBUG) |
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138 | switch ( the_mutex->Attributes.lock_nesting_behavior ) { |
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139 | case CORE_MUTEX_NESTING_ACQUIRES: |
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140 | _Thread_queue_Release( &the_mutex->Wait_queue, lock_context ); |
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141 | return CORE_MUTEX_STATUS_SUCCESSFUL; |
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142 | #if defined(RTEMS_POSIX_API) |
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143 | case CORE_MUTEX_NESTING_IS_ERROR: |
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144 | /* should never occur */ |
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145 | _Thread_queue_Release( &the_mutex->Wait_queue, lock_context ); |
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146 | return CORE_MUTEX_STATUS_NESTING_NOT_ALLOWED; |
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147 | #endif |
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148 | case CORE_MUTEX_NESTING_BLOCKS: |
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149 | /* Currently no API exercises this behavior. */ |
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150 | break; |
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151 | } |
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152 | #else |
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153 | _Thread_queue_Release( &the_mutex->Wait_queue, lock_context ); |
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154 | /* must be CORE_MUTEX_NESTING_ACQUIRES or we wouldn't be here */ |
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155 | return CORE_MUTEX_STATUS_SUCCESSFUL; |
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156 | #endif |
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157 | } |
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158 | |
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159 | /* |
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160 | * Formally release the mutex before possibly transferring it to a |
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161 | * blocked thread. |
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162 | */ |
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163 | if ( _CORE_mutex_Is_inherit_priority( &the_mutex->Attributes ) || |
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164 | _CORE_mutex_Is_priority_ceiling( &the_mutex->Attributes ) ) { |
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165 | CORE_mutex_Status pop_status = |
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166 | _CORE_mutex_Pop_priority( the_mutex, holder ); |
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167 | |
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168 | if ( pop_status != CORE_MUTEX_STATUS_SUCCESSFUL ) { |
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169 | _Thread_queue_Release( &the_mutex->Wait_queue, lock_context ); |
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170 | return pop_status; |
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171 | } |
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172 | |
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173 | holder->resource_count--; |
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174 | } |
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175 | the_mutex->holder = NULL; |
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176 | |
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177 | /* |
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178 | * Now we check if another thread was waiting for this mutex. If so, |
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179 | * transfer the mutex to that thread. |
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180 | */ |
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181 | if ( |
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182 | ( the_thread = _Thread_queue_First_locked( |
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183 | &the_mutex->Wait_queue, |
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184 | the_mutex->operations |
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185 | ) |
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186 | ) |
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187 | ) { |
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188 | bool unblock; |
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189 | |
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190 | /* |
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191 | * We must extract the thread now since this will restore its default |
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192 | * thread lock. This is necessary to avoid a deadlock in the |
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193 | * _Thread_Change_priority() below due to a recursive thread queue lock |
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194 | * acquire. |
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195 | */ |
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196 | unblock = _Thread_queue_Extract_locked( |
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197 | &the_mutex->Wait_queue.Queue, |
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198 | the_mutex->operations, |
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199 | the_thread |
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200 | ); |
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201 | |
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202 | #if defined(RTEMS_MULTIPROCESSING) |
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203 | _Thread_Dispatch_disable(); |
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204 | |
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205 | if ( _Objects_Is_local_id( the_thread->Object.id ) ) |
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206 | #endif |
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207 | { |
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208 | the_mutex->holder = the_thread; |
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209 | the_mutex->nest_count = 1; |
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210 | |
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211 | switch ( the_mutex->Attributes.discipline ) { |
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212 | case CORE_MUTEX_DISCIPLINES_FIFO: |
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213 | case CORE_MUTEX_DISCIPLINES_PRIORITY: |
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214 | break; |
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215 | case CORE_MUTEX_DISCIPLINES_PRIORITY_INHERIT: |
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216 | _CORE_mutex_Push_priority( the_mutex, the_thread ); |
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217 | the_thread->resource_count++; |
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218 | _Thread_queue_Boost_priority( &the_mutex->Wait_queue.Queue, the_thread ); |
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219 | break; |
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220 | case CORE_MUTEX_DISCIPLINES_PRIORITY_CEILING: |
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221 | _CORE_mutex_Push_priority( the_mutex, the_thread ); |
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222 | the_thread->resource_count++; |
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223 | _Thread_Raise_priority( |
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224 | the_thread, |
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225 | the_mutex->Attributes.priority_ceiling |
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226 | ); |
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227 | break; |
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228 | } |
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229 | } |
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230 | |
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231 | _Thread_queue_Unblock_critical( |
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232 | unblock, |
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233 | &the_mutex->Wait_queue.Queue, |
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234 | the_thread, |
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235 | lock_context |
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236 | ); |
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237 | |
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238 | #if defined(RTEMS_MULTIPROCESSING) |
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239 | if ( !_Objects_Is_local_id( the_thread->Object.id ) ) { |
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240 | |
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241 | the_mutex->holder = NULL; |
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242 | the_mutex->nest_count = 1; |
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243 | |
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244 | ( *api_mutex_mp_support)( the_thread, id ); |
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245 | |
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246 | } |
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247 | |
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248 | _Thread_Dispatch_enable( _Per_CPU_Get() ); |
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249 | #endif |
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250 | } else { |
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251 | _Thread_queue_Release( &the_mutex->Wait_queue, lock_context ); |
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252 | } |
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253 | |
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254 | /* |
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255 | * Whether or not someone is waiting for the mutex, an |
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256 | * inherited priority must be lowered if this is the last |
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257 | * mutex (i.e. resource) this task has. |
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258 | */ |
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259 | if ( !_Thread_Owns_resources( holder ) ) { |
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260 | /* |
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261 | * Ensure that the holder resource count is visible to all other processors |
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262 | * and that we read the latest priority restore hint. |
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263 | */ |
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264 | _Atomic_Fence( ATOMIC_ORDER_ACQ_REL ); |
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265 | |
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266 | if ( holder->priority_restore_hint ) { |
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267 | Per_CPU_Control *cpu_self; |
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268 | |
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269 | cpu_self = _Thread_Dispatch_disable(); |
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270 | _Thread_Restore_priority( holder ); |
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271 | _Thread_Dispatch_enable( cpu_self ); |
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272 | } |
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273 | } |
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274 | |
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275 | return CORE_MUTEX_STATUS_SUCCESSFUL; |
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276 | } |
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