1 | // -*- Mode: CFA -*-
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2 | //
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3 | // Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
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4 | //
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5 | // The contents of this file are covered under the licence agreement in the
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6 | // file "LICENCE" distributed with Cforall.
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7 | //
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8 | // kernel.c --
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9 | //
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10 | // Author : Thierry Delisle
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11 | // Created On : Tue Jan 17 12:27:26 2017
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12 | // Last Modified By : Thierry Delisle
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13 | // Last Modified On : --
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14 | // Update Count : 0
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15 | //
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16 |
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17 | //Start and stop routine for the kernel, declared first to make sure they run first
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18 | void kernel_startup(void) __attribute__((constructor(101)));
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19 | void kernel_shutdown(void) __attribute__((destructor(101)));
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20 |
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21 | //Header
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22 | #include "kernel_private.h"
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23 |
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24 | //C Includes
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25 | #include <stddef.h>
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26 | extern "C" {
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27 | #include <fenv.h>
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28 | #include <sys/resource.h>
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29 | }
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30 |
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31 | //CFA Includes
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32 | #include "libhdr.h"
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33 |
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34 | //Private includes
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35 | #define __CFA_INVOKE_PRIVATE__
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36 | #include "invoke.h"
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37 |
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38 | //-----------------------------------------------------------------------------
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39 | // Kernel storage
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40 | #define KERNEL_STORAGE(T,X) static char X##_storage[sizeof(T)]
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41 |
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42 | KERNEL_STORAGE(processorCtx_t, systemProcessorCtx);
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43 | KERNEL_STORAGE(cluster, systemCluster);
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44 | KERNEL_STORAGE(processor, systemProcessor);
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45 | KERNEL_STORAGE(thread_desc, mainThread);
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46 | KERNEL_STORAGE(machine_context_t, mainThread_context);
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47 |
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48 | cluster * systemCluster;
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49 | processor * systemProcessor;
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50 | thread_desc * mainThread;
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51 |
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52 | //-----------------------------------------------------------------------------
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53 | // Global state
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54 |
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55 | thread_local processor * this_processor;
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56 |
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57 | coroutine_desc * this_coroutine(void) {
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58 | return this_processor->current_coroutine;
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59 | }
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60 |
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61 | thread_desc * this_thread(void) {
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62 | return this_processor->current_thread;
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63 | }
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64 |
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65 | //-----------------------------------------------------------------------------
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66 | // Main thread construction
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67 | struct current_stack_info_t {
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68 | machine_context_t ctx;
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69 | unsigned int size; // size of stack
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70 | void *base; // base of stack
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71 | void *storage; // pointer to stack
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72 | void *limit; // stack grows towards stack limit
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73 | void *context; // address of cfa_context_t
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74 | void *top; // address of top of storage
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75 | };
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76 |
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77 | void ?{}( current_stack_info_t * this ) {
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78 | CtxGet( &this->ctx );
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79 | this->base = this->ctx.FP;
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80 | this->storage = this->ctx.SP;
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81 |
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82 | rlimit r;
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83 | getrlimit( RLIMIT_STACK, &r);
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84 | this->size = r.rlim_cur;
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85 |
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86 | this->limit = (void *)(((intptr_t)this->base) - this->size);
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87 | this->context = &mainThread_context_storage;
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88 | this->top = this->base;
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89 | }
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90 |
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91 | void ?{}( coStack_t * this, current_stack_info_t * info) {
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92 | this->size = info->size;
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93 | this->storage = info->storage;
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94 | this->limit = info->limit;
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95 | this->base = info->base;
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96 | this->context = info->context;
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97 | this->top = info->top;
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98 | this->userStack = true;
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99 | }
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100 |
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101 | void ?{}( coroutine_desc * this, current_stack_info_t * info) {
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102 | (&this->stack){ info };
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103 | this->name = "Main Thread";
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104 | this->errno_ = 0;
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105 | this->state = Start;
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106 | }
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107 |
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108 | void ?{}( thread_desc * this, current_stack_info_t * info) {
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109 | (&this->cor){ info };
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110 | }
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111 |
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112 | //-----------------------------------------------------------------------------
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113 | // Processor coroutine
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114 | void ?{}(processorCtx_t * this, processor * proc) {
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115 | (&this->__cor){};
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116 | this->proc = proc;
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117 | proc->runner = this;
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118 | }
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119 |
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120 | void ?{}(processorCtx_t * this, processor * proc, current_stack_info_t * info) {
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121 | (&this->__cor){ info };
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122 | this->proc = proc;
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123 | proc->runner = this;
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124 | }
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125 |
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126 | void ?{}(processor * this) {
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127 | this{ systemCluster };
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128 | }
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129 |
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130 | void ?{}(processor * this, cluster * cltr) {
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131 | this->cltr = cltr;
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132 | this->current_coroutine = NULL;
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133 | this->current_thread = NULL;
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134 | (&this->terminated){};
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135 | this->is_terminated = false;
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136 |
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137 | start( this );
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138 | }
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139 |
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140 | void ?{}(processor * this, cluster * cltr, processorCtx_t * runner) {
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141 | this->cltr = cltr;
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142 | this->current_coroutine = NULL;
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143 | this->current_thread = NULL;
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144 | (&this->terminated){};
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145 | this->is_terminated = false;
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146 |
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147 | this->runner = runner;
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148 | LIB_DEBUG_PRINTF("Kernel : constructing processor context %p\n", runner);
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149 | runner{ this };
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150 | }
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151 |
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152 | void ^?{}(processor * this) {
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153 | if( ! this->is_terminated ) {
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154 | LIB_DEBUG_PRINTF("Kernel : core %p signaling termination\n", this);
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155 | this->is_terminated = true;
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156 | wait( &this->terminated );
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157 | }
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158 | }
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159 |
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160 | void ?{}(cluster * this) {
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161 | ( &this->ready_queue ){};
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162 | ( &this->lock ){};
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163 | }
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164 |
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165 | void ^?{}(cluster * this) {
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166 |
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167 | }
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168 |
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169 | //=============================================================================================
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170 | // Kernel Scheduling logic
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171 | //=============================================================================================
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172 | //Main of the processor contexts
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173 | void main(processorCtx_t * runner) {
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174 | processor * this = runner->proc;
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175 | LIB_DEBUG_PRINTF("Kernel : core %p starting\n", this);
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176 |
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177 | thread_desc * readyThread = NULL;
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178 | for( unsigned int spin_count = 0; ! this->is_terminated; spin_count++ )
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179 | {
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180 | readyThread = nextThread( this->cltr );
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181 |
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182 | if(readyThread)
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183 | {
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184 | runThread(this, readyThread);
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185 |
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186 | //Some actions need to be taken from the kernel
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187 | finishRunning(this);
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188 |
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189 | spin_count = 0;
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190 | }
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191 | else
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192 | {
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193 | spin(this, &spin_count);
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194 | }
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195 | }
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196 |
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197 | LIB_DEBUG_PRINTF("Kernel : core %p unlocking thread\n", this);
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198 | signal( &this->terminated );
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199 | LIB_DEBUG_PRINTF("Kernel : core %p terminated\n", this);
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200 | }
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201 |
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202 | // runThread runs a thread by context switching
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203 | // from the processor coroutine to the target thread
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204 | void runThread(processor * this, thread_desc * dst) {
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205 | coroutine_desc * proc_cor = get_coroutine(this->runner);
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206 | coroutine_desc * thrd_cor = get_coroutine(dst);
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207 |
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208 | //Reset the terminating actions here
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209 | this->finish.action_code = No_Action;
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210 |
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211 | //Update global state
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212 | this->current_thread = dst;
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213 |
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214 | // Context Switch to the thread
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215 | ThreadCtxSwitch(proc_cor, thrd_cor);
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216 | // when ThreadCtxSwitch returns we are back in the processor coroutine
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217 | }
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218 |
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219 | // Once a thread has finished running, some of
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220 | // its final actions must be executed from the kernel
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221 | void finishRunning(processor * this) {
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222 | if( this->finish.action_code == Release ) {
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223 | unlock( this->finish.lock );
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224 | }
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225 | else if( this->finish.action_code == Schedule ) {
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226 | ScheduleThread( this->finish.thrd );
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227 | }
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228 | else if( this->finish.action_code == Release_Schedule ) {
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229 | unlock( this->finish.lock );
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230 | ScheduleThread( this->finish.thrd );
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231 | }
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232 | else {
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233 | assert(this->finish.action_code == No_Action);
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234 | }
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235 | }
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236 |
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237 | // Handles spinning logic
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238 | // TODO : find some strategy to put cores to sleep after some time
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239 | void spin(processor * this, unsigned int * spin_count) {
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240 | (*spin_count)++;
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241 | }
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242 |
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243 | // Context invoker for processors
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244 | // This is the entry point for processors (kernel threads)
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245 | // It effectively constructs a coroutine by stealing the pthread stack
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246 | void * CtxInvokeProcessor(void * arg) {
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247 | processor * proc = (processor *) arg;
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248 | this_processor = proc;
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249 | // SKULLDUGGERY: We want to create a context for the processor coroutine
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250 | // which is needed for the 2-step context switch. However, there is no reason
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251 | // to waste the perfectly valid stack create by pthread.
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252 | current_stack_info_t info;
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253 | machine_context_t ctx;
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254 | info.context = &ctx;
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255 | processorCtx_t proc_cor_storage = { proc, &info };
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256 |
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257 | LIB_DEBUG_PRINTF("Coroutine : created stack %p\n", proc_cor_storage.__cor.stack.base);
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258 |
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259 | //Set global state
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260 | proc->current_coroutine = &proc->runner->__cor;
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261 | proc->current_thread = NULL;
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262 |
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263 | //We now have a proper context from which to schedule threads
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264 | LIB_DEBUG_PRINTF("Kernel : core %p created (%p, %p)\n", proc, proc->runner, &ctx);
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265 |
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266 | // SKULLDUGGERY: Since the coroutine doesn't have its own stack, we can't
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267 | // resume it to start it like it normally would, it will just context switch
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268 | // back to here. Instead directly call the main since we already are on the
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269 | // appropriate stack.
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270 | proc_cor_storage.__cor.state = Active;
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271 | main( &proc_cor_storage );
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272 | proc_cor_storage.__cor.state = Halted;
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273 |
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274 | // Main routine of the core returned, the core is now fully terminated
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275 | LIB_DEBUG_PRINTF("Kernel : core %p main ended (%p)\n", proc, proc->runner);
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276 |
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277 | return NULL;
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278 | }
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279 |
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280 | void start(processor * this) {
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281 | LIB_DEBUG_PRINTF("Kernel : Starting core %p\n", this);
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282 |
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283 | // pthread_attr_t attributes;
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284 | // pthread_attr_init( &attributes );
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285 |
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286 | pthread_create( &this->kernel_thread, NULL, CtxInvokeProcessor, (void*)this );
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287 |
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288 | // pthread_attr_destroy( &attributes );
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289 |
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290 | LIB_DEBUG_PRINTF("Kernel : core %p started\n", this);
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291 | }
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292 |
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293 | //-----------------------------------------------------------------------------
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294 | // Scheduler routines
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295 | void ScheduleThread( thread_desc * thrd ) {
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296 | assertf( thrd->next == NULL, "Expected null got %p", thrd->next );
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297 |
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298 | lock( &systemProcessor->cltr->lock );
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299 | append( &systemProcessor->cltr->ready_queue, thrd );
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300 | unlock( &systemProcessor->cltr->lock );
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301 | }
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302 |
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303 | thread_desc * nextThread(cluster * this) {
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304 | lock( &this->lock );
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305 | thread_desc * head = pop_head( &this->ready_queue );
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306 | unlock( &this->lock );
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307 | return head;
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308 | }
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309 |
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310 | void ScheduleInternal() {
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311 | suspend();
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312 | }
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313 |
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314 | void ScheduleInternal( spinlock * lock ) {
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315 | this_processor->finish.action_code = Release;
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316 | this_processor->finish.lock = lock;
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317 | suspend();
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318 | }
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319 |
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320 | void ScheduleInternal( thread_desc * thrd ) {
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321 | this_processor->finish.action_code = Schedule;
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322 | this_processor->finish.thrd = thrd;
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323 | suspend();
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324 | }
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325 |
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326 | void ScheduleInternal( spinlock * lock, thread_desc * thrd ) {
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327 | this_processor->finish.action_code = Release_Schedule;
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328 | this_processor->finish.lock = lock;
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329 | this_processor->finish.thrd = thrd;
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330 | suspend();
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331 | }
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332 |
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333 | //-----------------------------------------------------------------------------
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334 | // Kernel boot procedures
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335 | void kernel_startup(void) {
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336 | LIB_DEBUG_PRINTF("Kernel : Starting\n");
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337 |
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338 | // Start by initializing the main thread
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339 | // SKULLDUGGERY: the mainThread steals the process main thread
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340 | // which will then be scheduled by the systemProcessor normally
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341 | mainThread = (thread_desc *)&mainThread_storage;
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342 | current_stack_info_t info;
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343 | mainThread{ &info };
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344 |
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345 | // Initialize the system cluster
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346 | systemCluster = (cluster *)&systemCluster_storage;
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347 | systemCluster{};
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348 |
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349 | // Initialize the system processor and the system processor ctx
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350 | // (the coroutine that contains the processing control flow)
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351 | systemProcessor = (processor *)&systemProcessor_storage;
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352 | systemProcessor{ systemCluster, (processorCtx_t *)&systemProcessorCtx_storage };
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353 |
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354 | // Add the main thread to the ready queue
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355 | // once resume is called on systemProcessor->ctx the mainThread needs to be scheduled like any normal thread
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356 | ScheduleThread(mainThread);
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357 |
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358 | //initialize the global state variables
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359 | this_processor = systemProcessor;
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360 | this_processor->current_thread = mainThread;
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361 | this_processor->current_coroutine = &mainThread->cor;
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362 |
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363 | // SKULLDUGGERY: Force a context switch to the system processor to set the main thread's context to the current UNIX
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364 | // context. Hence, the main thread does not begin through CtxInvokeThread, like all other threads. The trick here is that
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365 | // mainThread is on the ready queue when this call is made.
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366 | resume(systemProcessor->runner);
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367 |
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368 |
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369 |
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370 | // THE SYSTEM IS NOW COMPLETELY RUNNING
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371 | LIB_DEBUG_PRINTF("Kernel : Started\n--------------------------------------------------\n\n");
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372 | }
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373 |
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374 | void kernel_shutdown(void) {
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375 | LIB_DEBUG_PRINTF("\n--------------------------------------------------\nKernel : Shutting down\n");
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376 |
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377 | // SKULLDUGGERY: Notify the systemProcessor it needs to terminates.
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378 | // When its coroutine terminates, it return control to the mainThread
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379 | // which is currently here
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380 | systemProcessor->is_terminated = true;
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381 | suspend();
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382 |
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383 | // THE SYSTEM IS NOW COMPLETELY STOPPED
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384 |
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385 | // Destroy the system processor and its context in reverse order of construction
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386 | // These were manually constructed so we need manually destroy them
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387 | ^(systemProcessor->runner){};
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388 | ^(systemProcessor){};
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389 |
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390 | // Final step, destroy the main thread since it is no longer needed
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391 | // Since we provided a stack to this taxk it will not destroy anything
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392 | ^(mainThread){};
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393 |
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394 | LIB_DEBUG_PRINTF("Kernel : Shutdown complete\n");
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395 | }
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396 |
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397 | //-----------------------------------------------------------------------------
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398 | // Locks
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399 | void ?{}( spinlock * this ) {
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400 | this->lock = 0;
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401 | }
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402 | void ^?{}( spinlock * this ) {
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403 |
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404 | }
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405 |
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406 | void lock( spinlock * this ) {
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407 | for ( unsigned int i = 1;; i += 1 ) {
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408 | if ( this->lock == 0 && __sync_lock_test_and_set_4( &this->lock, 1 ) == 0 ) break;
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409 | }
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410 | }
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411 |
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412 | void unlock( spinlock * this ) {
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413 | __sync_lock_release_4( &this->lock );
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414 | }
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415 |
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416 | void ?{}( signal_once * this ) {
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417 | this->condition = false;
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418 | }
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419 | void ^?{}( signal_once * this ) {
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420 |
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421 | }
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422 |
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423 | void wait( signal_once * this ) {
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424 | lock( &this->lock );
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425 | if( !this->condition ) {
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426 | append( &this->blocked, this_thread() );
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427 | ScheduleInternal( &this->lock );
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428 | lock( &this->lock );
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429 | }
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430 | unlock( &this->lock );
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431 | }
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432 |
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433 | void signal( signal_once * this ) {
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434 | lock( &this->lock );
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435 | {
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436 | this->condition = true;
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437 |
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438 | thread_desc * it;
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439 | while( it = pop_head( &this->blocked) ) {
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440 | ScheduleThread( it );
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441 | }
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442 | }
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443 | unlock( &this->lock );
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444 | }
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445 |
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446 | //-----------------------------------------------------------------------------
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447 | // Queues
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448 | void ?{}( simple_thread_list * this ) {
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449 | this->head = NULL;
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450 | this->tail = &this->head;
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451 | }
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452 |
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453 | void append( simple_thread_list * this, thread_desc * t ) {
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454 | assert(this->tail != NULL);
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455 | *this->tail = t;
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456 | this->tail = &t->next;
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457 | }
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458 |
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459 | thread_desc * pop_head( simple_thread_list * this ) {
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460 | thread_desc * head = this->head;
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461 | if( head ) {
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462 | this->head = head->next;
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463 | if( !head->next ) {
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464 | this->tail = &this->head;
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465 | }
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466 | head->next = NULL;
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467 | }
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468 | return head;
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469 | }
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470 | // Local Variables: //
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471 | // mode: c //
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472 | // tab-width: 4 //
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473 | // End: //
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