1 | /* |
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2 | * Copyright (c) 2014, 2016 embedded brains GmbH. All rights reserved. |
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3 | * |
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4 | * embedded brains GmbH |
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5 | * Dornierstr. 4 |
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6 | * 82178 Puchheim |
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7 | * Germany |
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8 | * <rtems@embedded-brains.de> |
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9 | * |
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10 | * The license and distribution terms for this file may be |
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11 | * found in the file LICENSE in this distribution or at |
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12 | * http://www.rtems.org/license/LICENSE. |
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13 | */ |
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14 | |
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15 | #ifndef _RTEMS_SCORE_SCHEDULERNODE_H |
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16 | #define _RTEMS_SCORE_SCHEDULERNODE_H |
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17 | |
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18 | #include <rtems/score/basedefs.h> |
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19 | #include <rtems/score/chain.h> |
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20 | #include <rtems/score/priority.h> |
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21 | #include <rtems/score/smplockseq.h> |
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22 | |
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23 | struct _Thread_Control; |
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24 | |
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25 | #ifdef __cplusplus |
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26 | extern "C" { |
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27 | #endif /* __cplusplus */ |
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28 | |
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29 | #if defined(RTEMS_SMP) |
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30 | /** |
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31 | * @brief State to indicate potential help for other threads. |
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32 | * |
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33 | * @dot |
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34 | * digraph state { |
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35 | * y [label="HELP YOURSELF"]; |
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36 | * ao [label="HELP ACTIVE OWNER"]; |
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37 | * ar [label="HELP ACTIVE RIVAL"]; |
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38 | * |
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39 | * y -> ao [label="obtain"]; |
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40 | * y -> ar [label="wait for obtain"]; |
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41 | * ao -> y [label="last release"]; |
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42 | * ao -> r [label="wait for obtain"]; |
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43 | * ar -> r [label="timeout"]; |
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44 | * ar -> ao [label="timeout"]; |
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45 | * } |
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46 | * @enddot |
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47 | */ |
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48 | typedef enum { |
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49 | /** |
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50 | * @brief This scheduler node is solely used by the owner thread. |
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51 | * |
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52 | * This thread owns no resources using a helping protocol and thus does not |
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53 | * take part in the scheduler helping protocol. No help will be provided for |
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54 | * other thread. |
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55 | */ |
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56 | SCHEDULER_HELP_YOURSELF, |
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57 | |
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58 | /** |
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59 | * @brief This scheduler node is owned by a thread actively owning a resource. |
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60 | * |
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61 | * This scheduler node can be used to help out threads. |
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62 | * |
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63 | * In case this scheduler node changes its state from ready to scheduled and |
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64 | * the thread executes using another node, then an idle thread will be |
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65 | * provided as a user of this node to temporarily execute on behalf of the |
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66 | * owner thread. Thus lower priority threads are denied access to the |
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67 | * processors of this scheduler instance. |
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68 | * |
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69 | * In case a thread actively owning a resource performs a blocking operation, |
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70 | * then an idle thread will be used also in case this node is in the |
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71 | * scheduled state. |
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72 | */ |
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73 | SCHEDULER_HELP_ACTIVE_OWNER, |
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74 | |
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75 | /** |
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76 | * @brief This scheduler node is owned by a thread actively obtaining a |
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77 | * resource currently owned by another thread. |
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78 | * |
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79 | * This scheduler node can be used to help out threads. |
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80 | * |
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81 | * The thread owning this node is ready and will give away its processor in |
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82 | * case the thread owning the resource asks for help. |
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83 | */ |
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84 | SCHEDULER_HELP_ACTIVE_RIVAL, |
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85 | |
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86 | /** |
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87 | * @brief This scheduler node is owned by a thread obtaining a |
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88 | * resource currently owned by another thread. |
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89 | * |
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90 | * This scheduler node can be used to help out threads. |
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91 | * |
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92 | * The thread owning this node is blocked. |
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93 | */ |
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94 | SCHEDULER_HELP_PASSIVE |
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95 | } Scheduler_Help_state; |
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96 | #endif |
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97 | |
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98 | /** |
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99 | * @brief Scheduler node for per-thread data. |
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100 | */ |
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101 | typedef struct Scheduler_Node { |
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102 | #if defined(RTEMS_SMP) |
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103 | /** |
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104 | * @brief Chain node for usage in various scheduler data structures. |
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105 | * |
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106 | * Strictly this is the wrong place for this field since the data structures |
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107 | * to manage scheduler nodes belong to the particular scheduler |
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108 | * implementation. Currently all SMP scheduler implementations use chains. |
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109 | * The node is here to simplify things, just like the object node in the |
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110 | * thread control block. It may be replaced with a union to add a red-black |
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111 | * tree node in the future. |
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112 | */ |
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113 | Chain_Node Node; |
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114 | |
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115 | /** |
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116 | * @brief The thread using this node. |
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117 | */ |
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118 | struct _Thread_Control *user; |
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119 | |
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120 | /** |
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121 | * @brief The help state of this node. |
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122 | */ |
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123 | Scheduler_Help_state help_state; |
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124 | |
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125 | /** |
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126 | * @brief The idle thread claimed by this node in case the help state is |
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127 | * SCHEDULER_HELP_ACTIVE_OWNER. |
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128 | * |
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129 | * Active owners will lend their own node to an idle thread in case they |
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130 | * execute currently using another node or in case they perform a blocking |
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131 | * operation. This is necessary to ensure the priority ceiling protocols |
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132 | * work across scheduler boundaries. |
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133 | */ |
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134 | struct _Thread_Control *idle; |
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135 | |
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136 | /** |
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137 | * @brief The thread accepting help by this node in case the help state is |
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138 | * not SCHEDULER_HELP_YOURSELF. |
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139 | */ |
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140 | struct _Thread_Control *accepts_help; |
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141 | |
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142 | /** |
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143 | * @brief Block to register and manage this scheduler node in the thread |
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144 | * control block of the owner of this scheduler node. |
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145 | */ |
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146 | struct { |
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147 | /** |
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148 | * @brief Node to add this scheduler node to |
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149 | * Thread_Control::Scheduler::Wait_nodes. |
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150 | */ |
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151 | Chain_Node Wait_node; |
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152 | } Thread; |
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153 | #endif |
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154 | |
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155 | /** |
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156 | * @brief Thread wait support block. |
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157 | */ |
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158 | struct { |
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159 | Priority_Aggregation Priority; |
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160 | } Wait; |
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161 | |
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162 | /** |
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163 | * @brief The thread owning this node. |
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164 | */ |
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165 | struct _Thread_Control *owner; |
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166 | |
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167 | /** |
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168 | * @brief The thread priority information used by the scheduler. |
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169 | * |
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170 | * The thread priority is manifest in two independent areas. One area is the |
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171 | * user visible thread priority along with a potential thread queue. The |
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172 | * other is the scheduler. During a thread priority change, the user visible |
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173 | * thread priority and the thread queue are first updated and the thread |
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174 | * priority value here is changed. Once this is done the scheduler is |
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175 | * notified via the update priority operation, so that it can update its |
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176 | * internal state and honour a new thread priority value. |
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177 | */ |
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178 | struct { |
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179 | /** |
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180 | * @brief The thread priority value of this scheduler node. |
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181 | * |
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182 | * The producer of this value is _Thread_Change_priority(). The consumer |
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183 | * is the scheduler via the unblock and update priority operations. |
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184 | */ |
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185 | Priority_Control value; |
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186 | |
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187 | #if defined(RTEMS_SMP) |
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188 | /** |
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189 | * @brief Sequence lock to synchronize priority value updates. |
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190 | */ |
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191 | SMP_sequence_lock_Control Lock; |
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192 | #endif |
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193 | |
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194 | /** |
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195 | * @brief In case a priority update is necessary and this is true, then |
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196 | * enqueue the thread as the first of its priority group, otherwise enqueue |
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197 | * the thread as the last of its priority group. |
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198 | */ |
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199 | bool prepend_it; |
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200 | } Priority; |
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201 | } Scheduler_Node; |
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202 | |
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203 | #if defined(RTEMS_SMP) |
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204 | /** |
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205 | * @brief The size of a scheduler node. |
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206 | * |
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207 | * This value is provided via <rtems/confdefs.h>. |
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208 | */ |
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209 | extern const size_t _Scheduler_Node_size; |
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210 | #endif |
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211 | |
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212 | #ifdef __cplusplus |
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213 | } |
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214 | #endif /* __cplusplus */ |
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215 | |
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216 | #endif /* _RTEMS_SCORE_SCHEDULERNODE_H */ |
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