1 | // |
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2 | // Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo |
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3 | // |
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4 | // The contents of this file are covered under the licence agreement in the |
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5 | // file "LICENCE" distributed with Cforall. |
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6 | // |
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7 | // signal.c -- |
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8 | // |
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9 | // Author : Thierry Delisle |
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10 | // Created On : Mon Jun 5 14:20:42 2017 |
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11 | // Last Modified By : Peter A. Buhr |
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12 | // Last Modified On : Tue Mar 27 11:28:51 2018 |
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13 | // Update Count : 24 |
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14 | // |
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15 | |
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16 | #include "preemption.h" |
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17 | |
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18 | extern "C" { |
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19 | #include <errno.h> |
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20 | #include <stdio.h> |
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21 | #include <string.h> |
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22 | #include <unistd.h> |
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23 | } |
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24 | |
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25 | #include "bits/cfatime.h" |
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26 | #include "bits/signal.h" |
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27 | |
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28 | #if !defined(__CFA_DEFAULT_PREEMPTION__) |
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29 | #define __CFA_DEFAULT_PREEMPTION__ 10`ms |
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30 | #endif |
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31 | |
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32 | Duration default_preemption() __attribute__((weak)) { |
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33 | return __CFA_DEFAULT_PREEMPTION__; |
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34 | } |
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35 | |
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36 | // FwdDeclarations : timeout handlers |
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37 | static void preempt( processor * this ); |
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38 | static void timeout( thread_desc * this ); |
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39 | |
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40 | // FwdDeclarations : Signal handlers |
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41 | void sigHandler_ctxSwitch( __CFA_SIGPARMS__ ); |
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42 | void sigHandler_segv ( __CFA_SIGPARMS__ ); |
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43 | void sigHandler_ill ( __CFA_SIGPARMS__ ); |
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44 | void sigHandler_fpe ( __CFA_SIGPARMS__ ); |
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45 | void sigHandler_abort ( __CFA_SIGPARMS__ ); |
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46 | |
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47 | // FwdDeclarations : alarm thread main |
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48 | void * alarm_loop( __attribute__((unused)) void * args ); |
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49 | |
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50 | // Machine specific register name |
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51 | #if defined( __i386 ) |
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52 | #define CFA_REG_IP gregs[REG_EIP] |
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53 | #elif defined( __x86_64 ) |
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54 | #define CFA_REG_IP gregs[REG_RIP] |
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55 | #elif defined( __ARM_ARCH ) |
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56 | #define CFA_REG_IP arm_pc |
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57 | #else |
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58 | #error unknown hardware architecture |
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59 | #endif |
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60 | |
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61 | KERNEL_STORAGE(event_kernel_t, event_kernel); // private storage for event kernel |
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62 | event_kernel_t * event_kernel; // kernel public handle to even kernel |
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63 | static pthread_t alarm_thread; // pthread handle to alarm thread |
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64 | |
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65 | void ?{}(event_kernel_t & this) with( this ) { |
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66 | alarms{}; |
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67 | lock{}; |
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68 | } |
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69 | |
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70 | enum { |
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71 | PREEMPT_NORMAL = 0, |
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72 | PREEMPT_TERMINATE = 1, |
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73 | }; |
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74 | |
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75 | //============================================================================================= |
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76 | // Kernel Preemption logic |
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77 | //============================================================================================= |
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78 | |
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79 | // Get next expired node |
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80 | static inline alarm_node_t * get_expired( alarm_list_t * alarms, Time currtime ) { |
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81 | if( !alarms->head ) return NULL; // If no alarms return null |
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82 | if( alarms->head->alarm >= currtime ) return NULL; // If alarms head not expired return null |
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83 | return pop(alarms); // Otherwise just pop head |
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84 | } |
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85 | |
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86 | // Tick one frame of the Discrete Event Simulation for alarms |
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87 | void tick_preemption() { |
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88 | alarm_node_t * node = NULL; // Used in the while loop but cannot be declared in the while condition |
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89 | alarm_list_t * alarms = &event_kernel->alarms; // Local copy for ease of reading |
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90 | Time currtime = __kernel_get_time(); // Check current time once so we everything "happens at once" |
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91 | |
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92 | //Loop throught every thing expired |
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93 | while( node = get_expired( alarms, currtime ) ) { |
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94 | |
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95 | // Check if this is a kernel |
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96 | if( node->kernel_alarm ) { |
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97 | preempt( node->proc ); |
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98 | } |
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99 | else { |
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100 | timeout( node->thrd ); |
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101 | } |
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102 | |
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103 | // Check if this is a periodic alarm |
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104 | Duration period = node->period; |
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105 | if( period > 0 ) { |
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106 | node->alarm = currtime + period; // Alarm is periodic, add currtime to it (used cached current time) |
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107 | insert( alarms, node ); // Reinsert the node for the next time it triggers |
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108 | } |
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109 | else { |
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110 | node->set = false; // Node is one-shot, just mark it as not pending |
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111 | } |
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112 | } |
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113 | |
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114 | // If there are still alarms pending, reset the timer |
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115 | if( alarms->head ) { __kernel_set_timer( alarms->head->alarm - currtime ); } |
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116 | } |
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117 | |
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118 | // Update the preemption of a processor and notify interested parties |
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119 | void update_preemption( processor * this, Duration duration ) { |
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120 | alarm_node_t * alarm = this->preemption_alarm; |
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121 | |
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122 | // Alarms need to be enabled |
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123 | if ( duration > 0 && ! alarm->set ) { |
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124 | alarm->alarm = __kernel_get_time() + duration; |
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125 | alarm->period = duration; |
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126 | register_self( alarm ); |
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127 | } |
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128 | // Zero duraction but alarm is set |
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129 | else if ( duration == 0 && alarm->set ) { |
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130 | unregister_self( alarm ); |
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131 | alarm->alarm = 0; |
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132 | alarm->period = 0; |
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133 | } |
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134 | // If alarm is different from previous, change it |
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135 | else if ( duration > 0 && alarm->period != duration ) { |
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136 | unregister_self( alarm ); |
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137 | alarm->alarm = __kernel_get_time() + duration; |
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138 | alarm->period = duration; |
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139 | register_self( alarm ); |
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140 | } |
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141 | } |
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142 | |
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143 | //============================================================================================= |
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144 | // Kernel Signal Tools |
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145 | //============================================================================================= |
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146 | |
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147 | __cfaabi_dbg_debug_do( static thread_local void * last_interrupt = 0; ) |
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148 | |
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149 | extern "C" { |
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150 | // Disable interrupts by incrementing the counter |
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151 | void disable_interrupts() { |
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152 | preemption_state.enabled = false; |
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153 | __attribute__((unused)) unsigned short new_val = preemption_state.disable_count + 1; |
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154 | preemption_state.disable_count = new_val; |
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155 | verify( new_val < 65_000u ); // If this triggers someone is disabling interrupts without enabling them |
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156 | } |
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157 | |
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158 | // Enable interrupts by decrementing the counter |
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159 | // If counter reaches 0, execute any pending CtxSwitch |
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160 | void enable_interrupts( __cfaabi_dbg_ctx_param ) { |
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161 | processor * proc = this_processor; // Cache the processor now since interrupts can start happening after the atomic add |
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162 | thread_desc * thrd = this_thread; // Cache the thread now since interrupts can start happening after the atomic add |
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163 | |
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164 | unsigned short prev = preemption_state.disable_count; |
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165 | preemption_state.disable_count -= 1; |
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166 | verify( prev != 0u ); // If this triggers someone is enabled already enabled interruptsverify( prev != 0u ); |
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167 | |
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168 | // Check if we need to prempt the thread because an interrupt was missed |
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169 | if( prev == 1 ) { |
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170 | preemption_state.enabled = true; |
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171 | if( proc->pending_preemption ) { |
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172 | proc->pending_preemption = false; |
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173 | BlockInternal( thrd ); |
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174 | } |
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175 | } |
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176 | |
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177 | // For debugging purposes : keep track of the last person to enable the interrupts |
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178 | __cfaabi_dbg_debug_do( proc->last_enable = caller; ) |
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179 | } |
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180 | |
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181 | // Disable interrupts by incrementint the counter |
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182 | // Don't execute any pending CtxSwitch even if counter reaches 0 |
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183 | void enable_interrupts_noPoll() { |
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184 | unsigned short prev = preemption_state.disable_count; |
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185 | preemption_state.disable_count -= 1; |
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186 | verifyf( prev != 0u, "Incremented from %u\n", prev ); // If this triggers someone is enabled already enabled interrupts |
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187 | if( prev == 1 ) { |
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188 | preemption_state.enabled = true; |
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189 | } |
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190 | } |
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191 | } |
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192 | |
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193 | // sigprocmask wrapper : unblock a single signal |
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194 | static inline void signal_unblock( int sig ) { |
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195 | sigset_t mask; |
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196 | sigemptyset( &mask ); |
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197 | sigaddset( &mask, sig ); |
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198 | |
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199 | if ( pthread_sigmask( SIG_UNBLOCK, &mask, NULL ) == -1 ) { |
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200 | abort( "internal error, pthread_sigmask" ); |
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201 | } |
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202 | } |
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203 | |
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204 | // sigprocmask wrapper : block a single signal |
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205 | static inline void signal_block( int sig ) { |
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206 | sigset_t mask; |
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207 | sigemptyset( &mask ); |
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208 | sigaddset( &mask, sig ); |
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209 | |
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210 | if ( pthread_sigmask( SIG_BLOCK, &mask, NULL ) == -1 ) { |
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211 | abort( "internal error, pthread_sigmask" ); |
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212 | } |
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213 | } |
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214 | |
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215 | // kill wrapper : signal a processor |
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216 | static void preempt( processor * this ) { |
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217 | sigval_t value = { PREEMPT_NORMAL }; |
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218 | pthread_sigqueue( this->kernel_thread, SIGUSR1, value ); |
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219 | } |
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220 | |
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221 | // kill wrapper : signal a processor |
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222 | void terminate(processor * this) { |
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223 | this->do_terminate = true; |
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224 | sigval_t value = { PREEMPT_TERMINATE }; |
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225 | pthread_sigqueue( this->kernel_thread, SIGUSR1, value ); |
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226 | } |
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227 | |
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228 | // reserved for future use |
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229 | static void timeout( thread_desc * this ) { |
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230 | //TODO : implement waking threads |
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231 | } |
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232 | |
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233 | |
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234 | // Check if a CtxSwitch signal handler shoud defer |
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235 | // If true : preemption is safe |
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236 | // If false : preemption is unsafe and marked as pending |
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237 | static inline bool preemption_ready() { |
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238 | bool ready = preemption_state.enabled && !preemption_state.in_progress; // Check if preemption is safe |
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239 | this_processor->pending_preemption = !ready; // Adjust the pending flag accordingly |
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240 | return ready; |
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241 | } |
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242 | |
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243 | //============================================================================================= |
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244 | // Kernel Signal Startup/Shutdown logic |
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245 | //============================================================================================= |
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246 | |
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247 | // Startup routine to activate preemption |
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248 | // Called from kernel_startup |
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249 | void kernel_start_preemption() { |
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250 | __cfaabi_dbg_print_safe( "Kernel : Starting preemption\n" ); |
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251 | |
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252 | // Start with preemption disabled until ready |
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253 | preemption_state.enabled = false; |
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254 | preemption_state.disable_count = 1; |
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255 | |
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256 | // Initialize the event kernel |
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257 | event_kernel = (event_kernel_t *)&storage_event_kernel; |
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258 | (*event_kernel){}; |
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259 | |
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260 | // Setup proper signal handlers |
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261 | __cfaabi_sigaction( SIGUSR1, sigHandler_ctxSwitch, SA_SIGINFO | SA_RESTART ); // CtxSwitch handler |
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262 | |
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263 | signal_block( SIGALRM ); |
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264 | |
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265 | pthread_create( &alarm_thread, NULL, alarm_loop, NULL ); |
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266 | } |
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267 | |
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268 | // Shutdown routine to deactivate preemption |
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269 | // Called from kernel_shutdown |
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270 | void kernel_stop_preemption() { |
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271 | __cfaabi_dbg_print_safe( "Kernel : Preemption stopping\n" ); |
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272 | |
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273 | // Block all signals since we are already shutting down |
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274 | sigset_t mask; |
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275 | sigfillset( &mask ); |
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276 | sigprocmask( SIG_BLOCK, &mask, NULL ); |
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277 | |
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278 | // Notify the alarm thread of the shutdown |
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279 | sigval val = { 1 }; |
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280 | pthread_sigqueue( alarm_thread, SIGALRM, val ); |
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281 | |
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282 | // Wait for the preemption thread to finish |
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283 | pthread_join( alarm_thread, NULL ); |
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284 | |
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285 | // Preemption is now fully stopped |
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286 | |
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287 | __cfaabi_dbg_print_safe( "Kernel : Preemption stopped\n" ); |
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288 | } |
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289 | |
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290 | // Raii ctor/dtor for the preemption_scope |
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291 | // Used by thread to control when they want to receive preemption signals |
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292 | void ?{}( preemption_scope & this, processor * proc ) { |
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293 | (this.alarm){ proc, (Time){ 0 }, 0`s }; |
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294 | this.proc = proc; |
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295 | this.proc->preemption_alarm = &this.alarm; |
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296 | |
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297 | update_preemption( this.proc, this.proc->cltr->preemption_rate ); |
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298 | } |
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299 | |
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300 | void ^?{}( preemption_scope & this ) { |
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301 | disable_interrupts(); |
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302 | |
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303 | update_preemption( this.proc, 0`s ); |
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304 | } |
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305 | |
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306 | //============================================================================================= |
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307 | // Kernel Signal Handlers |
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308 | //============================================================================================= |
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309 | |
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310 | // Context switch signal handler |
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311 | // Receives SIGUSR1 signal and causes the current thread to yield |
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312 | void sigHandler_ctxSwitch( __CFA_SIGPARMS__ ) { |
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313 | __cfaabi_dbg_debug_do( last_interrupt = (void *)(cxt->uc_mcontext.CFA_REG_IP); ) |
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314 | |
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315 | // SKULLDUGGERY: if a thread creates a processor and the immediately deletes it, |
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316 | // the interrupt that is supposed to force the kernel thread to preempt might arrive |
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317 | // before the kernel thread has even started running. When that happens an iterrupt |
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318 | // we a null 'this_processor' will be caught, just ignore it. |
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319 | if(!this_processor) return; |
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320 | |
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321 | choose(sfp->si_value.sival_int) { |
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322 | case PREEMPT_NORMAL : ;// Normal case, nothing to do here |
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323 | case PREEMPT_TERMINATE: verify(this_processor->do_terminate); |
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324 | default: |
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325 | abort( "internal error, signal value is %d", sfp->si_value.sival_int ); |
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326 | } |
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327 | |
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328 | // Check if it is safe to preempt here |
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329 | if( !preemption_ready() ) { return; } |
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330 | |
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331 | __cfaabi_dbg_print_buffer_decl( " KERNEL: preempting core %p (%p).\n", this_processor, this_thread); |
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332 | |
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333 | preemption_state.in_progress = true; // Sync flag : prevent recursive calls to the signal handler |
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334 | signal_unblock( SIGUSR1 ); // We are about to CtxSwitch out of the signal handler, let other handlers in |
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335 | preemption_state.in_progress = false; // Clear the in progress flag |
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336 | |
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337 | // Preemption can occur here |
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338 | |
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339 | BlockInternal( (thread_desc*)this_thread ); // Do the actual CtxSwitch |
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340 | } |
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341 | |
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342 | // Main of the alarm thread |
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343 | // Waits on SIGALRM and send SIGUSR1 to whom ever needs it |
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344 | void * alarm_loop( __attribute__((unused)) void * args ) { |
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345 | // Block sigalrms to control when they arrive |
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346 | sigset_t mask; |
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347 | sigemptyset( &mask ); |
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348 | sigaddset( &mask, SIGALRM ); |
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349 | |
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350 | if ( pthread_sigmask( SIG_BLOCK, &mask, NULL ) == -1 ) { |
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351 | abort( "internal error, pthread_sigmask" ); |
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352 | } |
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353 | |
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354 | // Main loop |
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355 | while( true ) { |
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356 | // Wait for a sigalrm |
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357 | siginfo_t info; |
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358 | int sig = sigwaitinfo( &mask, &info ); |
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359 | |
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360 | if( sig < 0 ) { |
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361 | //Error! |
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362 | int err = errno; |
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363 | switch( err ) { |
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364 | case EAGAIN : |
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365 | case EINTR : |
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366 | continue; |
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367 | case EINVAL : |
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368 | abort( "Timeout was invalid." ); |
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369 | default: |
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370 | abort( "Unhandled error %d", err); |
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371 | } |
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372 | } |
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373 | |
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374 | // If another signal arrived something went wrong |
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375 | assertf(sig == SIGALRM, "Kernel Internal Error, sigwait: Unexpected signal %d (%d : %d)\n", sig, info.si_code, info.si_value.sival_int); |
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376 | |
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377 | // __cfaabi_dbg_print_safe( "Kernel : Caught alarm from %d with %d\n", info.si_code, info.si_value.sival_int ); |
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378 | // Switch on the code (a.k.a. the sender) to |
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379 | switch( info.si_code ) |
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380 | { |
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381 | // Timers can apparently be marked as sent for the kernel |
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382 | // In either case, tick preemption |
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383 | case SI_TIMER: |
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384 | case SI_KERNEL: |
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385 | // __cfaabi_dbg_print_safe( "Kernel : Preemption thread tick\n" ); |
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386 | lock( event_kernel->lock __cfaabi_dbg_ctx2 ); |
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387 | tick_preemption(); |
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388 | unlock( event_kernel->lock ); |
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389 | break; |
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390 | // Signal was not sent by the kernel but by an other thread |
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391 | case SI_QUEUE: |
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392 | // For now, other thread only signal the alarm thread to shut it down |
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393 | // If this needs to change use info.si_value and handle the case here |
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394 | goto EXIT; |
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395 | } |
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396 | } |
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397 | |
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398 | EXIT: |
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399 | __cfaabi_dbg_print_safe( "Kernel : Preemption thread stopping\n" ); |
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400 | return NULL; |
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401 | } |
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402 | |
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403 | // Local Variables: // |
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404 | // mode: c // |
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405 | // tab-width: 4 // |
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406 | // End: // |
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