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:: partitions |
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8 | |
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9 | Partition Manager |
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10 | ***************** |
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11 | |
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12 | Introduction |
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13 | ============ |
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14 | |
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15 | The partition manager provides facilities to dynamically allocate memory in |
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16 | fixed-size units. The directives provided by the partition manager are: |
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17 | |
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18 | - rtems_partition_create_ - Create a partition |
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19 | |
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20 | - rtems_partition_ident_ - Get ID of a partition |
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21 | |
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22 | - rtems_partition_delete_ - Delete a partition |
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23 | |
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24 | - rtems_partition_get_buffer_ - Get buffer from a partition |
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25 | |
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26 | - rtems_partition_return_buffer_ - Return buffer to a partition |
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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 | .. index:: partition, definition |
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32 | |
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33 | Partition Manager Definitions |
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34 | ----------------------------- |
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35 | |
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36 | A partition is a physically contiguous memory area divided into fixed-size |
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37 | buffers that can be dynamically allocated and deallocated. |
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38 | |
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39 | .. index:: buffers, definition |
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40 | |
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41 | Partitions are managed and maintained as a list of buffers. Buffers are |
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42 | obtained from the front of the partition's free buffer chain and returned to |
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43 | the rear of the same chain. When a buffer is on the free buffer chain, RTEMS |
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44 | uses two pointers of memory from each buffer as the free buffer chain. When a |
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45 | buffer is allocated, the entire buffer is available for application use. |
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46 | Therefore, modifying memory that is outside of an allocated buffer could |
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47 | destroy the free buffer chain or the contents of an adjacent allocated buffer. |
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48 | |
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49 | .. index:: partition attribute set, building |
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50 | |
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51 | Building a Partition Attribute Set |
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52 | ---------------------------------- |
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53 | |
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54 | In general, an attribute set is built by a bitwise OR of the desired attribute |
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55 | components. The set of valid partition attributes is provided in the following |
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56 | table: |
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57 | |
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58 | .. list-table:: |
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59 | :class: rtems-table |
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60 | |
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61 | * - ``RTEMS_LOCAL`` |
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62 | - local partition (default) |
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63 | * - ``RTEMS_GLOBAL`` |
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64 | - global partition |
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65 | |
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66 | Attribute values are specifically designed to be mutually exclusive, therefore |
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67 | bitwise OR and addition operations are equivalent as long as each attribute |
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68 | appears exactly once in the component list. An attribute listed as a default |
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69 | is not required to appear in the attribute list, although it is a good |
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70 | programming practice to specify default attributes. If all defaults are |
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71 | desired, the attribute ``RTEMS_DEFAULT_ATTRIBUTES`` should be specified on this |
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72 | call. The attribute_set parameter should be ``RTEMS_GLOBAL`` to indicate that |
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73 | the partition is to be known globally. |
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74 | |
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75 | Operations |
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76 | ========== |
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77 | |
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78 | Creating a Partition |
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79 | -------------------- |
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80 | |
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81 | The ``rtems_partition_create`` directive creates a partition with a |
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82 | user-specified name. The partition's name, starting address, length and buffer |
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83 | size are all specified to the ``rtems_partition_create`` directive. RTEMS |
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84 | allocates a Partition Control Block (PTCB) from the PTCB free list. This data |
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85 | structure is used by RTEMS to manage the newly created partition. The number |
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86 | of buffers in the partition is calculated based upon the specified partition |
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87 | length and buffer size. If successful,the unique partition ID is returned to |
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88 | the calling task. |
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89 | |
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90 | Obtaining Partition IDs |
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91 | ----------------------- |
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92 | |
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93 | When a partition is created, RTEMS generates a unique partition ID and assigned |
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94 | it to the created partition until it is deleted. The partition ID may be |
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95 | obtained by either of two methods. First, as the result of an invocation of |
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96 | the ``rtems_partition_create`` directive, the partition ID is stored in a user |
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97 | provided location. Second, the partition ID may be obtained later using the |
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98 | ``rtems_partition_ident`` directive. The partition ID is used by other |
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99 | partition manager directives to access this partition. |
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100 | |
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101 | Acquiring a Buffer |
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102 | ------------------ |
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103 | |
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104 | A buffer can be obtained by calling the ``rtems_partition_get_buffer`` |
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105 | directive. If a buffer is available, then it is returned immediately with a |
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106 | successful return code. Otherwise, an unsuccessful return code is returned |
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107 | immediately to the caller. Tasks cannot block to wait for a buffer to become |
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108 | available. |
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109 | |
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110 | Releasing a Buffer |
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111 | ------------------ |
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112 | |
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113 | Buffers are returned to a partition's free buffer chain with the |
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114 | ``rtems_partition_return_buffer`` directive. This directive returns an error |
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115 | status code if the returned buffer was not previously allocated from this |
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116 | partition. |
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117 | |
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118 | Deleting a Partition |
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119 | -------------------- |
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120 | |
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121 | The ``rtems_partition_delete`` directive allows a partition to be removed and |
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122 | returned to RTEMS. When a partition is deleted, the PTCB for that partition is |
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123 | returned to the PTCB free list. A partition with buffers still allocated |
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124 | cannot be deleted. Any task attempting to do so will be returned an error |
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125 | status code. |
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126 | |
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127 | Directives |
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128 | ========== |
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129 | |
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130 | This section details the partition manager's directives. A subsection is |
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131 | dedicated to each of this manager's directives and describes the calling |
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132 | sequence, related constants, usage, and status codes. |
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133 | |
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134 | .. raw:: latex |
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135 | |
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136 | \clearpage |
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137 | |
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138 | .. index:: create a partition |
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139 | .. index:: rtems_partition_create |
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140 | |
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141 | .. _rtems_partition_create: |
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142 | |
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143 | PARTITION_CREATE - Create a partition |
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144 | ------------------------------------- |
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145 | |
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146 | CALLING SEQUENCE: |
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147 | .. code-block:: c |
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148 | |
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149 | rtems_status_code rtems_partition_create( |
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150 | rtems_name name, |
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151 | void *starting_address, |
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152 | uintptr_t length, |
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153 | size_t buffer_size, |
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154 | rtems_attribute attribute_set, |
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155 | rtems_id *id |
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156 | ); |
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157 | |
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158 | DIRECTIVE STATUS CODES: |
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159 | .. list-table:: |
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160 | :class: rtems-table |
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161 | |
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162 | * - ``RTEMS_SUCCESSFUL`` |
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163 | - partition created successfully |
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164 | * - ``RTEMS_INVALID_NAME`` |
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165 | - invalid partition ``name`` |
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166 | * - ``RTEMS_TOO_MANY`` |
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167 | - too many partitions created |
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168 | * - ``RTEMS_INVALID_ADDRESS`` |
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169 | - ``starting_address`` is not on a pointer size boundary |
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170 | * - ``RTEMS_INVALID_ADDRESS`` |
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171 | - ``starting_address`` is NULL |
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172 | * - ``RTEMS_INVALID_ADDRESS`` |
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173 | - ``id`` is NULL |
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174 | * - ``RTEMS_INVALID_SIZE`` |
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175 | - ``length`` or ``buffer_size`` is 0 |
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176 | * - ``RTEMS_INVALID_SIZE`` |
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177 | - ``length`` is less than the ``buffer_size`` |
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178 | * - ``RTEMS_INVALID_SIZE`` |
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179 | - ``buffer_size`` is not an integral multiple of the pointer size |
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180 | * - ``RTEMS_INVALID_SIZE`` |
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181 | - ``buffer_size`` is less than two times the pointer size |
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182 | * - ``RTEMS_MP_NOT_CONFIGURED`` |
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183 | - multiprocessing not configured |
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184 | * - ``RTEMS_TOO_MANY`` |
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185 | - too many global objects |
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186 | |
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187 | DESCRIPTION: |
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188 | This directive creates a partition of fixed size buffers from a physically |
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189 | contiguous memory space which starts at starting_address and is length |
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190 | bytes in size. Each allocated buffer is to be of ``buffer_size`` in bytes. |
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191 | The assigned partition id is returned in ``id``. This partition id is used |
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192 | to access the partition with other partition related directives. For |
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193 | control and maintenance of the partition, RTEMS allocates a PTCB from the |
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194 | local PTCB free pool and initializes it. |
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195 | |
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196 | NOTES: |
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197 | This directive will not cause the calling task to be preempted. |
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198 | |
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199 | The partition buffer area specified by the ``starting_address`` must be |
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200 | properly aligned. It must be possible to directly store target |
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201 | architecture pointers and the also the user data. For example, if the user |
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202 | data contains some long double or vector data types, the partition buffer |
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203 | area and the buffer size must take the alignment of these types into |
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204 | account which is usually larger than the pointer alignment. A cache line |
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205 | alignment may be also a factor. |
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206 | |
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207 | The ``buffer_size`` parameter must be an integral multiple of the pointer |
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208 | size on the target architecture. Additionally, ``buffer_size`` must be |
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209 | large enough to hold two pointers on the target architecture. This is |
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210 | required for RTEMS to manage the buffers when they are free. |
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211 | |
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212 | Memory from the partition is not used by RTEMS to store the Partition |
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213 | Control Block. |
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214 | |
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215 | The following partition attribute constants are defined by RTEMS: |
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216 | |
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217 | .. list-table:: |
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218 | :class: rtems-table |
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219 | |
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220 | * - ``RTEMS_LOCAL`` |
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221 | - local partition (default) |
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222 | * - ``RTEMS_GLOBAL`` |
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223 | - global partition |
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224 | |
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225 | The PTCB for a global partition is allocated on the local node. The memory |
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226 | space used for the partition must reside in shared memory. Partitions |
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227 | should not be made global unless remote tasks must interact with the |
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228 | partition. This is to avoid the overhead incurred by the creation of a |
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229 | global partition. When a global partition is created, the partition's name |
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230 | and id must be transmitted to every node in the system for insertion in the |
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231 | local copy of the global object table. |
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232 | |
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233 | The total number of global objects, including partitions, is limited by the |
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234 | maximum_global_objects field in the Configuration Table. |
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235 | |
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236 | EXAMPLE: |
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237 | .. code-block:: c |
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238 | |
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239 | #include <rtems.h> |
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240 | #include <rtems/chain.h> |
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241 | |
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242 | #include <assert.h> |
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243 | |
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244 | typedef struct { |
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245 | char less; |
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246 | short more; |
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247 | } item; |
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248 | |
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249 | union { |
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250 | item data; |
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251 | rtems_chain_node node; |
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252 | } items[ 13 ]; |
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253 | |
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254 | rtems_id create_partition(void) |
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255 | { |
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256 | rtems_id id; |
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257 | rtems_status_code sc; |
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258 | |
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259 | sc = rtems_partition_create( |
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260 | rtems_build_name( 'P', 'A', 'R', 'T' ), |
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261 | items, |
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262 | sizeof( items ), |
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263 | sizeof( items[ 0 ] ), |
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264 | RTEMS_DEFAULT_ATTRIBUTES, |
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265 | &id |
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266 | ); |
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267 | assert(sc == RTEMS_SUCCESSFUL); |
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268 | |
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269 | return id; |
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270 | } |
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271 | |
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272 | .. raw:: latex |
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273 | |
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274 | \clearpage |
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275 | |
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276 | .. index:: get ID of a partition |
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277 | .. index:: obtain ID of a partition |
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278 | .. index:: rtems_partition_ident |
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279 | |
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280 | .. _rtems_partition_ident: |
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281 | |
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282 | PARTITION_IDENT - Get ID of a partition |
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283 | --------------------------------------- |
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284 | |
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285 | CALLING SEQUENCE: |
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286 | .. code-block:: c |
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287 | |
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288 | rtems_status_code rtems_partition_ident( |
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289 | rtems_name name, |
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290 | uint32_t node, |
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291 | rtems_id *id |
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292 | ); |
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293 | |
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294 | DIRECTIVE STATUS CODES: |
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295 | .. list-table:: |
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296 | :class: rtems-table |
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297 | |
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298 | * - ``RTEMS_SUCCESSFUL`` |
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299 | - partition identified successfully |
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300 | * - ``RTEMS_INVALID_ADDRESS`` |
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301 | - ``id`` is NULL |
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302 | * - ``RTEMS_INVALID_NAME`` |
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303 | - partition name not found |
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304 | * - ``RTEMS_INVALID_NODE`` |
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305 | - invalid node id |
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306 | |
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307 | DESCRIPTION: |
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308 | This directive obtains the partition id associated with the partition name. |
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309 | If the partition name is not unique, then the partition id will match one |
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310 | of the partitions with that name. However, this partition id is not |
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311 | guaranteed to correspond to the desired partition. The partition id is |
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312 | used with other partition related directives to access the partition. |
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313 | |
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314 | NOTES: |
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315 | This directive will not cause the running task to be preempted. |
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316 | |
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317 | If node is ``RTEMS_SEARCH_ALL_NODES``, all nodes are searched with the |
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318 | local node being searched first. All other nodes are searched with the |
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319 | lowest numbered node searched first. |
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320 | |
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321 | If node is a valid node number which does not represent the local node, |
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322 | then only the partitions exported by the designated node are searched. |
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323 | |
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324 | This directive does not generate activity on remote nodes. It accesses |
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325 | only the local copy of the global object table. |
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326 | |
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327 | .. raw:: latex |
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328 | |
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329 | \clearpage |
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330 | |
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331 | .. index:: delete a partition |
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332 | .. index:: rtems_partition_delete |
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333 | |
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334 | .. _rtems_partition_delete: |
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335 | |
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336 | PARTITION_DELETE - Delete a partition |
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337 | ------------------------------------- |
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338 | |
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339 | CALLING SEQUENCE: |
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340 | .. code-block:: c |
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341 | |
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342 | rtems_status_code rtems_partition_delete( |
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343 | rtems_id id |
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344 | ); |
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345 | |
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346 | DIRECTIVE STATUS CODES: |
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347 | .. list-table:: |
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348 | :class: rtems-table |
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349 | |
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350 | * - ``RTEMS_SUCCESSFUL`` |
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351 | - partition deleted successfully |
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352 | * - ``RTEMS_INVALID_ID`` |
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353 | - invalid partition id |
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354 | * - ``RTEMS_RESOURCE_IN_USE`` |
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355 | - buffers still in use |
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356 | * - ``RTEMS_ILLEGAL_ON_REMOTE_OBJECT`` |
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357 | - cannot delete remote partition |
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358 | |
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359 | DESCRIPTION: |
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360 | This directive deletes the partition specified by id. The partition cannot |
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361 | be deleted if any of its buffers are still allocated. The PTCB for the |
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362 | deleted partition is reclaimed by RTEMS. |
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363 | |
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364 | NOTES: |
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365 | This directive will not cause the calling task to be preempted. |
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366 | |
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367 | The calling task does not have to be the task that created the partition. |
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368 | Any local task that knows the partition id can delete the partition. |
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369 | |
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370 | When a global partition is deleted, the partition id must be transmitted to |
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371 | every node in the system for deletion from the local copy of the global |
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372 | object table. |
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373 | |
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374 | The partition must reside on the local node, even if the partition was |
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375 | created with the ``RTEMS_GLOBAL`` option. |
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376 | |
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377 | .. raw:: latex |
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378 | |
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379 | \clearpage |
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380 | |
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381 | .. index:: get buffer from partition |
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382 | .. index:: obtain buffer from partition |
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383 | .. index:: rtems_partition_get_buffer |
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384 | |
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385 | .. _rtems_partition_get_buffer: |
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386 | |
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387 | PARTITION_GET_BUFFER - Get buffer from a partition |
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388 | -------------------------------------------------- |
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389 | |
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390 | CALLING SEQUENCE: |
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391 | .. code-block:: c |
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392 | |
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393 | rtems_status_code rtems_partition_get_buffer( |
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394 | rtems_id id, |
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395 | void **buffer |
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396 | ); |
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397 | |
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398 | DIRECTIVE STATUS CODES: |
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399 | .. list-table:: |
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400 | :class: rtems-table |
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401 | |
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402 | * - ``RTEMS_SUCCESSFUL`` |
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403 | - buffer obtained successfully |
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404 | * - ``RTEMS_INVALID_ADDRESS`` |
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405 | - ``buffer`` is NULL |
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406 | * - ``RTEMS_INVALID_ID`` |
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407 | - invalid partition id |
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408 | * - ``RTEMS_UNSATISFIED`` |
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409 | - all buffers are allocated |
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410 | |
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411 | DESCRIPTION: |
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412 | This directive allows a buffer to be obtained from the partition specified |
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413 | in id. The address of the allocated buffer is returned in buffer. |
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414 | |
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415 | NOTES: |
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416 | This directive will not cause the running task to be preempted. |
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417 | |
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418 | All buffers begin on a four byte boundary. |
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419 | |
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420 | A task cannot wait on a buffer to become available. |
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421 | |
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422 | Getting a buffer from a global partition which does not reside on the local |
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423 | node will generate a request telling the remote node to allocate a buffer |
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424 | from the specified partition. |
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425 | |
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426 | .. raw:: latex |
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427 | |
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428 | \clearpage |
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429 | |
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430 | .. index:: return buffer to partitition |
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431 | .. index:: rtems_partition_return_buffer |
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432 | |
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433 | .. _rtems_partition_return_buffer: |
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434 | |
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435 | PARTITION_RETURN_BUFFER - Return buffer to a partition |
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436 | ------------------------------------------------------ |
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437 | |
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438 | CALLING SEQUENCE: |
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439 | .. code-block:: c |
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440 | |
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441 | rtems_status_code rtems_partition_return_buffer( |
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442 | rtems_id id, |
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443 | void *buffer |
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444 | ); |
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445 | |
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446 | DIRECTIVE STATUS CODES: |
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447 | .. list-table:: |
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448 | :class: rtems-table |
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449 | |
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450 | * - ``RTEMS_SUCCESSFUL`` |
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451 | - buffer returned successfully |
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452 | * - ``RTEMS_INVALID_ADDRESS`` |
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453 | - ``buffer`` is NULL |
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454 | * - ``RTEMS_INVALID_ID`` |
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455 | - invalid partition id |
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456 | * - ``RTEMS_INVALID_ADDRESS`` |
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457 | - buffer address not in partition |
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458 | |
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459 | DESCRIPTION: |
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460 | This directive returns the buffer specified by buffer to the partition |
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461 | specified by id. |
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462 | |
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463 | NOTES: |
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464 | This directive will not cause the running task to be preempted. |
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465 | |
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466 | Returning a buffer to a global partition which does not reside on the local |
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467 | node will generate a request telling the remote node to return the buffer |
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468 | to the specified partition. |
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469 | |
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470 | Returning a buffer multiple times is an error. It will corrupt the |
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471 | internal state of the partition. |
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