1 | .. comment SPDX-License-Identifier: CC-BY-SA-4.0 |
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2 | |
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3 | .. COMMENT: COPYRIGHT (c) 1988-2008. |
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4 | .. COMMENT: On-Line Applications Research Corporation (OAR). |
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5 | .. COMMENT: All rights reserved. |
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6 | |
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7 | .. index:: user extensions |
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8 | |
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9 | .. _User Extensions Manager: |
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10 | |
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11 | User Extensions Manager |
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12 | *********************** |
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13 | |
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14 | Introduction |
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15 | ============ |
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16 | |
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17 | The user extensions manager allows the application developer to augment the |
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18 | executive by allowing them to supply extension routines which are invoked at |
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19 | critical system events. The directives provided by the user extensions manager |
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20 | are: |
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21 | |
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22 | - rtems_extension_create_ - Create an extension set |
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23 | |
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24 | - rtems_extension_ident_ - Get ID of an extension set |
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25 | |
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26 | - rtems_extension_delete_ - Delete an extension set |
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27 | |
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28 | Background |
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29 | ========== |
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30 | |
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31 | User extensions (call-back functions) are invoked by the system when the |
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32 | following events occur |
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33 | |
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34 | - thread creation, |
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35 | |
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36 | - thread start, |
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37 | |
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38 | - thread restart, |
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39 | |
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40 | - thread switch, |
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41 | |
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42 | - thread begin, |
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43 | |
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44 | - thread exitted (return from thread entry function), |
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45 | |
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46 | - thread termination, |
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47 | |
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48 | - thread deletion, and |
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49 | |
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50 | - fatal error detection (system termination). |
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51 | |
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52 | The user extensions have event-specific arguments, invocation orders and |
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53 | execution contexts. Extension sets can be installed at run-time via |
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54 | :ref:`rtems_extension_create() <rtems_extension_create>` (dynamic extension |
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55 | sets) or at link-time via the application configuration option |
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56 | :ref:`CONFIGURE_INITIAL_EXTENSIONS <CONFIGURE_INITIAL_EXTENSIONS>` (initial |
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57 | extension sets). |
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58 | |
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59 | The execution context of user extensions varies. Some user extensions are |
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60 | invoked with ownership of the allocator mutex. The allocator mutex protects |
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61 | dynamic memory allocations and object creation/deletion. Some user extensions |
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62 | are invoked with thread dispatching disabled. The fatal error extension is |
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63 | invoked in an arbitrary context. |
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64 | |
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65 | .. index:: user extension set |
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66 | .. index:: rtems_extensions_table |
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67 | |
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68 | Extension Sets |
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69 | -------------- |
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70 | |
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71 | User extensions are maintained as a set. All user extensions are optional and |
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72 | may be `NULL`. Together a set of these user extensions typically performs a |
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73 | specific functionality such as performance monitoring or debugger support. The |
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74 | extension set is defined via the following structure. |
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75 | |
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76 | .. code-block:: c |
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77 | |
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78 | typedef struct { |
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79 | rtems_task_create_extension thread_create; |
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80 | rtems_task_start_extension thread_start; |
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81 | rtems_task_restart_extension thread_restart; |
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82 | rtems_task_delete_extension thread_delete; |
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83 | rtems_task_switch_extension thread_switch; |
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84 | rtems_task_begin_extension thread_begin; |
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85 | rtems_task_exitted_extension thread_exitted; |
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86 | rtems_fatal_extension fatal; |
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87 | rtems_task_terminate_extension thread_terminate; |
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88 | } rtems_extensions_table; |
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89 | |
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90 | .. index:: TCB extension area |
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91 | |
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92 | TCB Extension Area |
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93 | ------------------ |
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94 | |
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95 | There is no system-provided storage for the initial extension sets. |
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96 | |
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97 | The task control block (TCB) contains a pointer for each dynamic extension set. |
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98 | The pointer is initialized to `NULL` during thread initialization before the |
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99 | thread create extension is invoked. The pointer may be used by the dynamic |
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100 | extension set to maintain thread-specific data. |
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101 | |
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102 | The TCB extension is an array of pointers in the TCB. The index into the table |
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103 | can be obtained from the extension identifier returned when the extension |
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104 | object is created: |
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105 | |
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106 | .. index:: rtems extensions table index |
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107 | |
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108 | .. code-block:: c |
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109 | |
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110 | index = rtems_object_id_get_index( extension_id ); |
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111 | |
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112 | The number of pointers in the area is the same as the number of dynamic user |
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113 | extension sets configured. This allows an application to augment the TCB with |
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114 | user-defined information. For example, an application could implement task |
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115 | profiling by storing timing statistics in the TCB's extended memory area. When |
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116 | a task context switch is being executed, the thread switch extension could read |
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117 | a real-time clock to calculate how long the task being swapped out has run as |
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118 | well as timestamp the starting time for the task being swapped in. |
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119 | |
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120 | If used, the extended memory area for the TCB should be allocated and the TCB |
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121 | extension pointer should be set at the time the task is created or started by |
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122 | either the thread create or thread start extension. The application is |
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123 | responsible for managing this extended memory area for the TCBs. The memory |
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124 | may be reinitialized by the thread restart extension and should be deallocated |
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125 | by the thread delete extension when the task is deleted. Since the TCB |
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126 | extension buffers would most likely be of a fixed size, the RTEMS partition |
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127 | manager could be used to manage the application's extended memory area. The |
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128 | application could create a partition of fixed size TCB extension buffers and |
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129 | use the partition manager's allocation and deallocation directives to obtain |
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130 | and release the extension buffers. |
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131 | |
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132 | Order of Invocation |
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133 | ------------------- |
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134 | |
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135 | The user extensions are invoked in either `forward` or `reverse` order. In |
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136 | forward order, the user extensions of initial extension sets are invoked before |
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137 | the user extensions of the dynamic extension sets. The forward order of |
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138 | initial extension sets is defined by the initial extension sets table index. |
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139 | The forward order of dynamic extension sets is defined by the order in which |
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140 | the dynamic extension sets were created. The reverse order is defined |
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141 | accordingly. By invoking the user extensions in this order, extensions can be |
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142 | built upon one another. At the following system events, the user extensions |
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143 | are invoked in `forward` order |
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144 | |
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145 | - thread creation, |
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146 | |
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147 | - thread start, |
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148 | |
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149 | - thread restart, |
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150 | |
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151 | - thread switch, |
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152 | |
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153 | - thread begin, |
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154 | |
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155 | - thread exitted (return from thread entry function), and |
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156 | |
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157 | - fatal error detection. |
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158 | |
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159 | At the following system events, the user extensions are invoked in `reverse` |
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160 | order: |
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161 | |
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162 | - thread termination, and |
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163 | |
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164 | - thread deletion. |
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165 | |
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166 | At these system events, the user extensions are invoked in reverse order to insure |
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167 | that if an extension set is built upon another, the more complicated user extension |
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168 | is invoked before the user extension it is built upon. An example is use of the |
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169 | thread delete extension by the Standard C Library. Extension sets which are |
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170 | installed after the Standard C Library will operate correctly even if they |
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171 | utilize the C Library because the C Library's thread delete extension is |
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172 | invoked after that of the other thread delete extensions. |
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173 | |
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174 | .. index:: rtems_task_create_extension |
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175 | |
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176 | Thread Create Extension |
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177 | ----------------------- |
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178 | |
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179 | The thread create extension is invoked during thread creation, for example |
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180 | via :ref:`rtems_task_create() <rtems_task_create>` or :c:func:`pthread_create`. |
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181 | The thread create extension is defined as follows. |
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182 | |
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183 | .. code-block:: c |
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184 | |
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185 | typedef bool ( *rtems_task_create_extension )( |
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186 | rtems_tcb *executing, |
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187 | rtems_tcb *created |
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188 | ); |
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189 | |
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190 | The :c:data:`executing` is a pointer to the TCB of the currently executing |
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191 | thread. The :c:data:`created` is a pointer to the TCB of the created thread. |
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192 | The created thread is completely initialized with respect to the operating |
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193 | system. |
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194 | |
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195 | The executing thread is the owner of the allocator mutex except during creation |
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196 | of the idle threads. Since the allocator mutex allows nesting the normal |
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197 | memory allocation routines can be used. |
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198 | |
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199 | A thread create extension will frequently attempt to allocate resources. If |
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200 | this allocation fails, then the thread create extension must return |
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201 | :c:data:`false` and the entire thread create operation will fail, otherwise it |
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202 | must return :c:data:`true`. |
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203 | |
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204 | The thread create extension is invoked in forward order with thread dispatching |
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205 | enabled (except during system initialization). |
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206 | |
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207 | .. index:: rtems_task_start_extension |
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208 | |
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209 | Thread Start Extension |
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210 | ---------------------- |
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211 | |
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212 | The thread start extension is invoked during a thread start, for example |
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213 | via :ref:`rtems_task_start() <rtems_task_start>` or :c:func:`pthread_create`. |
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214 | The thread start extension is defined as follows. |
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215 | |
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216 | .. code-block:: c |
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217 | |
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218 | typedef void ( *rtems_task_start_extension )( |
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219 | rtems_tcb *executing, |
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220 | rtems_tcb *started |
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221 | ); |
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222 | |
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223 | The :c:data:`executing` is a pointer to the TCB of the currently executing |
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224 | thread. The :c:data:`started` is a pointer to the TCB of the started thread. |
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225 | It is invoked after the environment of the started thread has been loaded and the |
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226 | started thread has been made ready. So, in SMP configurations, the thread may |
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227 | already run on another processor before the thread start extension is actually |
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228 | invoked. Thread switch and thread begin extensions may run before or in |
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229 | parallel with the thread start extension in SMP configurations. |
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230 | |
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231 | The thread start extension is invoked in forward order with thread dispatching |
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232 | disabled. |
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233 | |
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234 | .. index:: rtems_task_restart_extension |
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235 | |
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236 | Thread Restart Extension |
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237 | ------------------------ |
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238 | |
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239 | The thread restart extension is invoked during a thread restart, for example |
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240 | via :ref:`rtems_task_restart() <rtems_task_start>`. |
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241 | The thread restart extension is defined as follows. |
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242 | |
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243 | .. code-block:: c |
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244 | |
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245 | typedef void ( *rtems_task_restart_extension )( |
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246 | rtems_tcb *executing, |
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247 | rtems_tcb *restarted |
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248 | ); |
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249 | |
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250 | Both :c:data:`executing` and :c:data:`restarted` are pointers the TCB of the |
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251 | currently executing thread. It is invoked in the context of the executing |
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252 | thread right before the execution context is reloaded. The thread stack |
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253 | reflects the previous execution context. |
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254 | |
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255 | The thread restart extension is invoked in forward order with thread |
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256 | dispatching enabled (except during system initialization). The thread life is |
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257 | protected. Thread restart and delete requests issued by thread restart |
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258 | extensions lead to recursion. The POSIX cleanup handlers, POSIX key |
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259 | destructors and thread-local object destructors run in this context. |
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260 | |
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261 | .. index:: rtems_task_switch_extension |
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262 | |
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263 | Thread Switch Extension |
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264 | ----------------------- |
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265 | |
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266 | The thread switch extension is invoked before the context switch from the |
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267 | currently executing thread to the heir thread. The thread switch extension is |
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268 | defined as follows. |
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269 | |
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270 | .. code-block:: c |
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271 | |
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272 | typedef void ( *rtems_task_switch_extension )( |
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273 | rtems_tcb *executing, |
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274 | rtems_tcb *heir |
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275 | ); |
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276 | |
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277 | The :c:data:`executing` is a pointer to the TCB of the currently executing |
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278 | thread. The :c:data:`heir` is a pointer to the TCB of the heir thread. |
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279 | |
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280 | The thread switch extension is invoked in forward order with thread dispatching |
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281 | disabled. In SMP configurations, interrupts are disabled and the per-processor |
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282 | SMP lock is owned. Thread switch extensions may run in parallel on multiple |
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283 | processors. It is recommended to use thread-local or per-processor data |
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284 | structures in SMP configurations for thread switch extensions. A global SMP |
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285 | lock should be avoided for performance reasons. |
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286 | |
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287 | The context switches initiated through the multitasking start are not covered |
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288 | by the thread switch extension. |
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289 | |
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290 | .. index:: rtems_task_begin_extension |
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291 | |
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292 | Thread Begin Extension |
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293 | ---------------------- |
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294 | |
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295 | The thread begin extension is invoked during a thread begin before the thread |
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296 | entry function is called. The thread begin extension is defined as follows. |
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297 | |
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298 | .. code-block:: c |
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299 | |
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300 | typedef void ( *rtems_task_begin_extension )( |
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301 | rtems_tcb *executing |
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302 | ); |
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303 | |
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304 | The :c:data:`executing` is a pointer to the TCB of the currently executing |
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305 | thread. The thread begin extension executes in a normal thread context and may |
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306 | allocate resources for the executing thread. In particular, it has access to |
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307 | thread-local storage of the executing thread. |
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308 | |
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309 | The thread begin extension is invoked in forward order with thread dispatching |
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310 | enabled. The thread switch extension may be called multiple times for this |
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311 | thread before or during the thread begin extension is invoked. |
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312 | |
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313 | .. index:: rtems_task_exitted_extension |
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314 | |
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315 | Thread Exitted Extension |
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316 | ------------------------ |
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317 | |
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318 | The thread exitted extension is invoked once the thread entry function returns. |
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319 | The thread exitted extension is defined as follows. |
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320 | |
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321 | .. code-block:: c |
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322 | |
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323 | typedef void ( *rtems_task_exitted_extension )( |
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324 | rtems_tcb *executing |
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325 | ); |
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326 | |
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327 | The :c:data:`executing` is a pointer to the TCB of the currently executing |
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328 | thread. |
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329 | |
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330 | This extension is invoked in forward order with thread dispatching enabled. |
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331 | |
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332 | .. index:: rtems_task_terminate_extension |
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333 | |
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334 | Thread Termination Extension |
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335 | ---------------------------- |
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336 | |
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337 | The thread termination extension is invoked in case a termination request is |
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338 | recognized by the currently executing thread. Termination requests may result |
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339 | due to calls of :ref:`rtems_task_delete() <rtems_task_delete>`, |
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340 | :c:func:`pthread_exit`, or :c:func:`pthread_cancel`. The thread termination |
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341 | extension is defined as follows. |
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342 | |
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343 | .. code-block:: c |
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344 | |
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345 | typedef void ( *rtems_task_terminate_extension )( |
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346 | rtems_tcb *executing |
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347 | ); |
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348 | |
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349 | The :c:data:`executing` is a pointer to the TCB of the currently executing |
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350 | thread. |
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351 | |
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352 | It is invoked in the context of the terminated thread right before the thread |
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353 | dispatch to the heir thread. The POSIX cleanup handlers, POSIX key destructors |
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354 | and thread-local object destructors run in this context. Depending on the |
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355 | order, the thread termination extension has access to thread-local storage and |
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356 | thread-specific data of POSIX keys. |
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357 | |
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358 | The thread terminate extension is invoked in reverse order with thread |
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359 | dispatching enabled. The thread life is protected. Thread restart and delete |
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360 | requests issued by thread terminate extensions lead to recursion. |
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361 | |
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362 | .. index:: rtems_task_delete_extension |
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363 | |
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364 | Thread Delete Extension |
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365 | ----------------------- |
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366 | |
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367 | The thread delete extension is invoked in case a zombie thread is killed. A |
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368 | thread becomes a zombie thread after it terminated. The thread delete |
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369 | extension is defined as follows. |
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370 | |
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371 | .. code-block:: c |
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372 | |
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373 | typedef void ( *rtems_task_delete_extension )( |
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374 | rtems_tcb *executing, |
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375 | rtems_tcb *deleted |
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376 | ); |
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377 | |
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378 | The :c:data:`executing` is a pointer to the TCB of the currently executing |
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379 | thread. The :c:data:`deleted` is a pointer to the TCB of the deleted thread. |
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380 | The :c:data:`executing` and :c:data:`deleted` pointers are never equal. |
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381 | |
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382 | The executing thread is the owner of the allocator mutex. Since the allocator |
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383 | mutex allows nesting the normal memory allocation routines can be used. |
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384 | |
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385 | The thread delete extension is invoked in reverse order with thread dispatching |
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386 | enabled. |
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387 | |
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388 | Please note that a thread delete extension is not immediately invoked with a |
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389 | call to :ref:`rtems_task_delete() <rtems_task_delete>` or similar. The thread |
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390 | must first terminate and this may take some time. The thread delete extension |
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391 | is invoked by :ref:`rtems_task_create() <rtems_task_create>` or similar as a |
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392 | result of a lazy garbage collection of zombie threads. |
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393 | |
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394 | .. index:: rtems_fatal_extension |
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395 | |
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396 | Fatal Error Extension |
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397 | --------------------- |
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398 | |
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399 | The fatal error extension is invoked during :ref:`system termination |
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400 | <Terminate>`. The fatal error extension is defined as follows. |
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401 | |
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402 | .. code-block:: c |
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403 | |
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404 | typedef void( *rtems_fatal_extension )( |
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405 | rtems_fatal_source source, |
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406 | bool always_set_to_false, |
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407 | rtems_fatal_code code |
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408 | ); |
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409 | |
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410 | The :c:data:`source` parameter is the fatal source indicating the subsystem the |
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411 | fatal condition originated in. The :c:data:`always_set_to_false` parameter is |
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412 | always set to :c:data:`false` and provided only for backward compatibility |
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413 | reasons. The :c:data:`code` parameter is the fatal error code. This value |
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414 | must be interpreted with respect to the source. |
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415 | |
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416 | The fatal error extension is invoked in forward order. |
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417 | |
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418 | It is strongly advised to use initial extension sets to install a fatal error |
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419 | extension. Usually, the initial extension set of board support package |
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420 | provides a fatal error extension which resets the board. In this case, the |
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421 | dynamic fatal error extensions are not invoked. |
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422 | |
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423 | Directives |
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424 | ========== |
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425 | |
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426 | This section details the user extension manager's directives. A subsection is |
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427 | dedicated to each of this manager's directives and describes the calling |
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428 | sequence, related constants, usage, and status codes. |
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429 | |
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430 | .. raw:: latex |
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431 | |
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432 | \clearpage |
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433 | |
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434 | .. index:: create an extension set |
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435 | .. index:: rtems_extension_create |
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436 | |
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437 | .. _rtems_extension_create: |
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438 | |
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439 | EXTENSION_CREATE - Create a extension set |
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440 | ----------------------------------------- |
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441 | |
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442 | CALLING SEQUENCE: |
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443 | .. code-block:: c |
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444 | |
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445 | rtems_status_code rtems_extension_create( |
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446 | rtems_name name, |
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447 | const rtems_extensions_table *table, |
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448 | rtems_id *id |
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449 | ); |
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450 | |
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451 | DIRECTIVE STATUS CODES: |
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452 | .. list-table:: |
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453 | :class: rtems-table |
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454 | |
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455 | * - ``RTEMS_SUCCESSFUL`` |
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456 | - extension set created successfully |
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457 | * - ``RTEMS_INVALID_NAME`` |
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458 | - invalid extension set name |
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459 | * - ``RTEMS_TOO_MANY`` |
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460 | - too many extension sets created |
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461 | |
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462 | DESCRIPTION: |
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463 | |
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464 | This directive creates an extension set object and initializes it using the |
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465 | specified extension set table. The assigned extension set identifier is |
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466 | returned in :c:data:`id`. This identifier is used to access the extension |
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467 | set with other user extension manager directives. For control and |
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468 | maintenance of the extension set, RTEMS allocates an Extension Set Control |
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469 | Block (ESCB) from the local ESCB free pool and initializes it. The |
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470 | user-specified :c:data:`name` is assigned to the ESCB and may be used to |
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471 | identify the extension set via |
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472 | :ref:`rtems_extension_ident() <rtems_extension_ident>`. The extension set |
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473 | specified by :c:data:`table` is copied to the ESCB. |
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474 | |
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475 | NOTES: |
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476 | |
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477 | This directive will not cause the calling task to be preempted. |
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478 | |
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479 | .. raw:: latex |
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480 | |
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481 | \clearpage |
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482 | |
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483 | .. index:: get ID of an extension set |
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484 | .. index:: obtain ID of an extension set |
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485 | .. index:: rtems_extension_ident |
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486 | |
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487 | .. _rtems_extension_ident: |
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488 | |
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489 | EXTENSION_IDENT - Get ID of a extension set |
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490 | ------------------------------------------- |
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491 | |
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492 | CALLING SEQUENCE: |
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493 | .. code-block:: c |
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494 | |
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495 | rtems_status_code rtems_extension_ident( |
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496 | rtems_name name, |
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497 | rtems_id *id |
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498 | ); |
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499 | |
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500 | DIRECTIVE STATUS CODES: |
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501 | .. list-table:: |
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502 | :class: rtems-table |
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503 | |
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504 | * - ``RTEMS_SUCCESSFUL`` |
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505 | - extension set identified successfully |
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506 | * - ``RTEMS_INVALID_NAME`` |
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507 | - extension set name not found |
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508 | |
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509 | DESCRIPTION: |
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510 | This directive obtains the extension set identifier associated with the |
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511 | extension set :c:data:`name` to be acquired and returns it in :c:data:`id`. |
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512 | If the extension set name is not unique, then the extension set identifier |
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513 | will match one of the extension sets with that name. However, this |
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514 | extension set identifier is not guaranteed to correspond to the desired |
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515 | extension set. The extension set identifier is used to access this |
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516 | extension set in other extension set related directives. |
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517 | |
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518 | NOTES: |
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519 | This directive will not cause the running task to be preempted. |
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520 | |
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521 | .. raw:: latex |
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522 | |
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523 | \clearpage |
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524 | |
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525 | .. index:: delete an extension set |
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526 | .. index:: rtems_extension_delete |
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527 | |
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528 | .. _rtems_extension_delete: |
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529 | |
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530 | EXTENSION_DELETE - Delete a extension set |
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531 | ----------------------------------------- |
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532 | |
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533 | CALLING SEQUENCE: |
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534 | .. code-block:: c |
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535 | |
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536 | rtems_status_code rtems_extension_delete( |
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537 | rtems_id id |
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538 | ); |
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539 | |
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540 | DIRECTIVE STATUS CODES: |
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541 | .. list-table:: |
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542 | :class: rtems-table |
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543 | |
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544 | * - ``RTEMS_SUCCESSFUL`` |
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545 | - extension set deleted successfully |
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546 | * - ``RTEMS_INVALID_ID`` |
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547 | - invalid extension set id |
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548 | |
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549 | DESCRIPTION: |
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550 | This directive deletes the extension set specified by :c:data:`id`. If the |
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551 | extension set is running, it is automatically canceled. The ESCB for the |
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552 | deleted extension set is reclaimed by RTEMS. |
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553 | |
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554 | NOTES: |
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555 | This directive will not cause the running task to be preempted. |
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556 | |
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557 | A extension set can be deleted by a task other than the task which created |
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558 | the extension set. |
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