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 : Mon Apr 9 13:52:39 2018 |
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13 | // Update Count : 36 |
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14 | // |
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15 | |
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16 | #include "preemption.h" |
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17 | #include <assert.h> |
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18 | |
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19 | extern "C" { |
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20 | #include <errno.h> |
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21 | #include <stdio.h> |
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22 | #include <string.h> |
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23 | #include <unistd.h> |
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24 | } |
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25 | |
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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 | // __cfaabi_dbg_print_buffer_decl( " KERNEL: preemption tick.\n" ); |
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95 | |
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96 | // Check if this is a kernel |
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97 | if( node->kernel_alarm ) { |
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98 | preempt( node->proc ); |
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99 | } |
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100 | else { |
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101 | timeout( node->thrd ); |
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102 | } |
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103 | |
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104 | // Check if this is a periodic alarm |
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105 | Duration period = node->period; |
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106 | if( period > 0 ) { |
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107 | // __cfaabi_dbg_print_buffer_local( " KERNEL: alarm period is %lu.\n", period.tv ); |
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108 | node->alarm = currtime + period; // Alarm is periodic, add currtime to it (used cached current time) |
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109 | insert( alarms, node ); // Reinsert the node for the next time it triggers |
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110 | } |
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111 | else { |
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112 | node->set = false; // Node is one-shot, just mark it as not pending |
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113 | } |
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114 | } |
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115 | |
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116 | // If there are still alarms pending, reset the timer |
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117 | if( alarms->head ) { |
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118 | __cfaabi_dbg_print_buffer_decl( " KERNEL: @%lu(%lu) resetting alarm to %lu.\n", currtime.tv, __kernel_get_time().tv, (alarms->head->alarm - currtime).tv); |
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119 | Duration delta = alarms->head->alarm - currtime; |
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120 | Duration caped = max(delta, 50`us); |
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121 | // itimerval tim = { caped }; |
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122 | // __cfaabi_dbg_print_buffer_local( " Values are %lu, %lu, %lu %lu.\n", delta.tv, caped.tv, tim.it_value.tv_sec, tim.it_value.tv_usec); |
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123 | |
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124 | __kernel_set_timer( caped ); |
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125 | } |
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126 | } |
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127 | |
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128 | // Update the preemption of a processor and notify interested parties |
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129 | void update_preemption( processor * this, Duration duration ) { |
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130 | alarm_node_t * alarm = this->preemption_alarm; |
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131 | |
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132 | // Alarms need to be enabled |
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133 | if ( duration > 0 && ! alarm->set ) { |
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134 | alarm->alarm = __kernel_get_time() + duration; |
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135 | alarm->period = duration; |
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136 | register_self( alarm ); |
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137 | } |
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138 | // Zero duration but alarm is set |
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139 | else if ( duration == 0 && alarm->set ) { |
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140 | unregister_self( alarm ); |
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141 | alarm->alarm = 0; |
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142 | alarm->period = 0; |
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143 | } |
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144 | // If alarm is different from previous, change it |
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145 | else if ( duration > 0 && alarm->period != duration ) { |
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146 | unregister_self( alarm ); |
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147 | alarm->alarm = __kernel_get_time() + duration; |
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148 | alarm->period = duration; |
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149 | register_self( alarm ); |
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150 | } |
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151 | } |
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152 | |
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153 | //============================================================================================= |
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154 | // Kernel Signal Tools |
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155 | //============================================================================================= |
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156 | |
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157 | __cfaabi_dbg_debug_do( static thread_local void * last_interrupt = 0; ) |
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158 | |
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159 | extern "C" { |
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160 | // Disable interrupts by incrementing the counter |
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161 | void disable_interrupts() { |
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162 | with( kernelTLS.preemption_state ) { |
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163 | static_assert(__atomic_always_lock_free(sizeof(enabled), &enabled), "Must be lock-free"); |
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164 | |
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165 | // Set enabled flag to false |
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166 | // should be atomic to avoid preemption in the middle of the operation. |
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167 | // use memory order RELAXED since there is no inter-thread on this variable requirements |
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168 | __atomic_store_n(&enabled, false, __ATOMIC_RELAXED); |
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169 | |
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170 | // Signal the compiler that a fence is needed but only for signal handlers |
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171 | __atomic_signal_fence(__ATOMIC_ACQUIRE); |
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172 | |
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173 | __attribute__((unused)) unsigned short new_val = disable_count + 1; |
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174 | disable_count = new_val; |
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175 | verify( new_val < 65_000u ); // If this triggers someone is disabling interrupts without enabling them |
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176 | } |
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177 | } |
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178 | |
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179 | // Enable interrupts by decrementing the counter |
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180 | // If counter reaches 0, execute any pending CtxSwitch |
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181 | void enable_interrupts( __cfaabi_dbg_ctx_param ) { |
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182 | processor * proc = kernelTLS.this_processor; // Cache the processor now since interrupts can start happening after the atomic store |
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183 | thread_desc * thrd = kernelTLS.this_thread; // Cache the thread now since interrupts can start happening after the atomic store |
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184 | |
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185 | with( kernelTLS.preemption_state ){ |
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186 | unsigned short prev = disable_count; |
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187 | disable_count -= 1; |
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188 | verify( prev != 0u ); // If this triggers someone is enabled already enabled interruptsverify( prev != 0u ); |
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189 | |
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190 | // Check if we need to prempt the thread because an interrupt was missed |
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191 | if( prev == 1 ) { |
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192 | static_assert(__atomic_always_lock_free(sizeof(enabled), &enabled), "Must be lock-free"); |
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193 | |
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194 | // Set enabled flag to true |
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195 | // should be atomic to avoid preemption in the middle of the operation. |
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196 | // use memory order RELAXED since there is no inter-thread on this variable requirements |
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197 | __atomic_store_n(&enabled, true, __ATOMIC_RELAXED); |
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198 | |
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199 | // Signal the compiler that a fence is needed but only for signal handlers |
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200 | __atomic_signal_fence(__ATOMIC_RELEASE); |
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201 | if( proc->pending_preemption ) { |
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202 | proc->pending_preemption = false; |
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203 | BlockInternal( thrd ); |
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204 | } |
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205 | } |
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206 | } |
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207 | |
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208 | // For debugging purposes : keep track of the last person to enable the interrupts |
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209 | __cfaabi_dbg_debug_do( proc->last_enable = caller; ) |
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210 | } |
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211 | |
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212 | // Disable interrupts by incrementint the counter |
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213 | // Don't execute any pending CtxSwitch even if counter reaches 0 |
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214 | void enable_interrupts_noPoll() { |
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215 | unsigned short prev = kernelTLS.preemption_state.disable_count; |
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216 | kernelTLS.preemption_state.disable_count -= 1; |
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217 | verifyf( prev != 0u, "Incremented from %u\n", prev ); // If this triggers someone is enabled already enabled interrupts |
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218 | if( prev == 1 ) { |
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219 | static_assert(__atomic_always_lock_free(sizeof(kernelTLS.preemption_state.enabled), &kernelTLS.preemption_state.enabled), "Must be lock-free"); |
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220 | // Set enabled flag to true |
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221 | // should be atomic to avoid preemption in the middle of the operation. |
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222 | // use memory order RELAXED since there is no inter-thread on this variable requirements |
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223 | __atomic_store_n(&kernelTLS.preemption_state.enabled, true, __ATOMIC_RELAXED); |
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224 | |
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225 | // Signal the compiler that a fence is needed but only for signal handlers |
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226 | __atomic_signal_fence(__ATOMIC_RELEASE); |
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227 | } |
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228 | } |
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229 | } |
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230 | |
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231 | // sigprocmask wrapper : unblock a single signal |
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232 | static inline void signal_unblock( int sig ) { |
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233 | sigset_t mask; |
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234 | sigemptyset( &mask ); |
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235 | sigaddset( &mask, sig ); |
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236 | |
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237 | if ( pthread_sigmask( SIG_UNBLOCK, &mask, NULL ) == -1 ) { |
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238 | abort( "internal error, pthread_sigmask" ); |
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239 | } |
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240 | } |
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241 | |
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242 | // sigprocmask wrapper : block a single signal |
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243 | static inline void signal_block( int sig ) { |
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244 | sigset_t mask; |
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245 | sigemptyset( &mask ); |
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246 | sigaddset( &mask, sig ); |
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247 | |
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248 | if ( pthread_sigmask( SIG_BLOCK, &mask, NULL ) == -1 ) { |
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249 | abort( "internal error, pthread_sigmask" ); |
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250 | } |
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251 | } |
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252 | |
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253 | // kill wrapper : signal a processor |
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254 | static void preempt( processor * this ) { |
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255 | sigval_t value = { PREEMPT_NORMAL }; |
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256 | pthread_sigqueue( this->kernel_thread, SIGUSR1, value ); |
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257 | } |
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258 | |
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259 | // kill wrapper : signal a processor |
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260 | void terminate(processor * this) { |
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261 | this->do_terminate = true; |
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262 | sigval_t value = { PREEMPT_TERMINATE }; |
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263 | pthread_sigqueue( this->kernel_thread, SIGUSR1, value ); |
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264 | } |
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265 | |
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266 | // reserved for future use |
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267 | static void timeout( thread_desc * this ) { |
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268 | //TODO : implement waking threads |
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269 | } |
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270 | |
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271 | // KERNEL ONLY |
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272 | // Check if a CtxSwitch signal handler shoud defer |
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273 | // If true : preemption is safe |
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274 | // If false : preemption is unsafe and marked as pending |
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275 | static inline bool preemption_ready() { |
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276 | // Check if preemption is safe |
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277 | bool ready = kernelTLS.preemption_state.enabled && ! kernelTLS.preemption_state.in_progress; |
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278 | |
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279 | // Adjust the pending flag accordingly |
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280 | kernelTLS.this_processor->pending_preemption = !ready; |
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281 | return ready; |
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282 | } |
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283 | |
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284 | //============================================================================================= |
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285 | // Kernel Signal Startup/Shutdown logic |
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286 | //============================================================================================= |
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287 | |
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288 | // Startup routine to activate preemption |
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289 | // Called from kernel_startup |
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290 | void kernel_start_preemption() { |
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291 | __cfaabi_dbg_print_safe( "Kernel : Starting preemption\n" ); |
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292 | |
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293 | // Start with preemption disabled until ready |
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294 | kernelTLS.preemption_state.enabled = false; |
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295 | kernelTLS.preemption_state.disable_count = 1; |
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296 | |
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297 | // Initialize the event kernel |
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298 | event_kernel = (event_kernel_t *)&storage_event_kernel; |
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299 | (*event_kernel){}; |
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300 | |
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301 | // Setup proper signal handlers |
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302 | __cfaabi_sigaction( SIGUSR1, sigHandler_ctxSwitch, SA_SIGINFO | SA_RESTART ); // CtxSwitch handler |
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303 | |
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304 | signal_block( SIGALRM ); |
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305 | |
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306 | pthread_create( &alarm_thread, NULL, alarm_loop, NULL ); |
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307 | } |
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308 | |
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309 | // Shutdown routine to deactivate preemption |
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310 | // Called from kernel_shutdown |
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311 | void kernel_stop_preemption() { |
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312 | __cfaabi_dbg_print_safe( "Kernel : Preemption stopping\n" ); |
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313 | |
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314 | // Block all signals since we are already shutting down |
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315 | sigset_t mask; |
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316 | sigfillset( &mask ); |
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317 | sigprocmask( SIG_BLOCK, &mask, NULL ); |
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318 | |
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319 | // Notify the alarm thread of the shutdown |
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320 | sigval val = { 1 }; |
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321 | pthread_sigqueue( alarm_thread, SIGALRM, val ); |
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322 | |
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323 | // Wait for the preemption thread to finish |
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324 | pthread_join( alarm_thread, NULL ); |
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325 | |
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326 | // Preemption is now fully stopped |
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327 | |
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328 | __cfaabi_dbg_print_safe( "Kernel : Preemption stopped\n" ); |
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329 | } |
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330 | |
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331 | // Raii ctor/dtor for the preemption_scope |
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332 | // Used by thread to control when they want to receive preemption signals |
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333 | void ?{}( preemption_scope & this, processor * proc ) { |
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334 | (this.alarm){ proc, (Time){ 0 }, 0`s }; |
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335 | this.proc = proc; |
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336 | this.proc->preemption_alarm = &this.alarm; |
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337 | |
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338 | update_preemption( this.proc, this.proc->cltr->preemption_rate ); |
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339 | } |
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340 | |
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341 | void ^?{}( preemption_scope & this ) { |
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342 | disable_interrupts(); |
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343 | |
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344 | update_preemption( this.proc, 0`s ); |
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345 | } |
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346 | |
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347 | //============================================================================================= |
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348 | // Kernel Signal Handlers |
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349 | //============================================================================================= |
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350 | |
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351 | // Context switch signal handler |
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352 | // Receives SIGUSR1 signal and causes the current thread to yield |
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353 | void sigHandler_ctxSwitch( __CFA_SIGPARMS__ ) { |
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354 | __cfaabi_dbg_debug_do( last_interrupt = (void *)(cxt->uc_mcontext.CFA_REG_IP); ) |
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355 | |
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356 | // SKULLDUGGERY: if a thread creates a processor and the immediately deletes it, |
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357 | // the interrupt that is supposed to force the kernel thread to preempt might arrive |
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358 | // before the kernel thread has even started running. When that happens an iterrupt |
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359 | // we a null 'this_processor' will be caught, just ignore it. |
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360 | if(! kernelTLS.this_processor ) return; |
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361 | |
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362 | choose(sfp->si_value.sival_int) { |
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363 | case PREEMPT_NORMAL : ;// Normal case, nothing to do here |
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364 | case PREEMPT_TERMINATE: verify( kernelTLS.this_processor->do_terminate); |
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365 | default: |
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366 | abort( "internal error, signal value is %d", sfp->si_value.sival_int ); |
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367 | } |
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368 | |
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369 | // Check if it is safe to preempt here |
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370 | if( !preemption_ready() ) { return; } |
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371 | |
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372 | __cfaabi_dbg_print_buffer_decl( " KERNEL: preempting core %p (%p @ %p).\n", kernelTLS.this_processor, kernelTLS.this_thread, (void *)(cxt->uc_mcontext.CFA_REG_IP) ); |
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373 | |
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374 | // Sync flag : prevent recursive calls to the signal handler |
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375 | kernelTLS.preemption_state.in_progress = true; |
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376 | |
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377 | // Clear sighandler mask before context switching. |
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378 | static_assert( sizeof( sigset_t ) == sizeof( cxt->uc_sigmask ), "Expected cxt->uc_sigmask to be of sigset_t" ); |
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379 | if ( pthread_sigmask( SIG_SETMASK, (sigset_t *)&(cxt->uc_sigmask), NULL ) == -1 ) { |
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380 | abort( "internal error, sigprocmask" ); |
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381 | } |
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382 | |
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383 | // TODO: this should go in finish action |
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384 | // Clear the in progress flag |
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385 | kernelTLS.preemption_state.in_progress = false; |
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386 | |
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387 | // Preemption can occur here |
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388 | |
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389 | BlockInternal( kernelTLS.this_thread ); // Do the actual CtxSwitch |
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390 | } |
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391 | |
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392 | // Main of the alarm thread |
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393 | // Waits on SIGALRM and send SIGUSR1 to whom ever needs it |
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394 | void * alarm_loop( __attribute__((unused)) void * args ) { |
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395 | // Block sigalrms to control when they arrive |
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396 | sigset_t mask; |
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397 | sigfillset(&mask); |
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398 | if ( pthread_sigmask( SIG_BLOCK, &mask, NULL ) == -1 ) { |
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399 | abort( "internal error, pthread_sigmask" ); |
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400 | } |
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401 | |
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402 | sigemptyset( &mask ); |
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403 | sigaddset( &mask, SIGALRM ); |
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404 | |
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405 | // Main loop |
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406 | while( true ) { |
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407 | // Wait for a sigalrm |
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408 | siginfo_t info; |
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409 | int sig = sigwaitinfo( &mask, &info ); |
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410 | |
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411 | if( sig < 0 ) { |
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412 | //Error! |
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413 | int err = errno; |
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414 | switch( err ) { |
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415 | case EAGAIN : |
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416 | case EINTR : |
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417 | {__cfaabi_dbg_print_buffer_decl( " KERNEL: Spurious wakeup %d.\n", err );} |
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418 | continue; |
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419 | case EINVAL : |
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420 | abort( "Timeout was invalid." ); |
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421 | default: |
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422 | abort( "Unhandled error %d", err); |
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423 | } |
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424 | } |
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425 | |
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426 | // If another signal arrived something went wrong |
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427 | 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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428 | |
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429 | // __cfaabi_dbg_print_safe( "Kernel : Caught alarm from %d with %d\n", info.si_code, info.si_value.sival_int ); |
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430 | // Switch on the code (a.k.a. the sender) to |
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431 | switch( info.si_code ) |
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432 | { |
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433 | // Timers can apparently be marked as sent for the kernel |
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434 | // In either case, tick preemption |
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435 | case SI_TIMER: |
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436 | case SI_KERNEL: |
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437 | // __cfaabi_dbg_print_safe( "Kernel : Preemption thread tick\n" ); |
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438 | lock( event_kernel->lock __cfaabi_dbg_ctx2 ); |
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439 | tick_preemption(); |
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440 | unlock( event_kernel->lock ); |
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441 | break; |
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442 | // Signal was not sent by the kernel but by an other thread |
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443 | case SI_QUEUE: |
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444 | // For now, other thread only signal the alarm thread to shut it down |
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445 | // If this needs to change use info.si_value and handle the case here |
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446 | goto EXIT; |
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447 | } |
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448 | } |
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449 | |
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450 | EXIT: |
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451 | __cfaabi_dbg_print_safe( "Kernel : Preemption thread stopping\n" ); |
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452 | return NULL; |
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453 | } |
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454 | |
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455 | //============================================================================================= |
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456 | // Kernel Signal Debug |
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457 | //============================================================================================= |
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458 | |
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459 | void __cfaabi_check_preemption() { |
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460 | bool ready = kernelTLS.preemption_state.enabled; |
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461 | if(!ready) { abort("Preemption should be ready"); } |
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462 | |
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463 | sigset_t oldset; |
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464 | int ret; |
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465 | ret = pthread_sigmask(0, NULL, &oldset); |
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466 | if(ret != 0) { abort("ERROR sigprocmask returned %d", ret); } |
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467 | |
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468 | ret = sigismember(&oldset, SIGUSR1); |
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469 | if(ret < 0) { abort("ERROR sigismember returned %d", ret); } |
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470 | if(ret == 1) { abort("ERROR SIGUSR1 is disabled"); } |
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471 | |
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472 | ret = sigismember(&oldset, SIGALRM); |
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473 | if(ret < 0) { abort("ERROR sigismember returned %d", ret); } |
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474 | if(ret == 0) { abort("ERROR SIGALRM is enabled"); } |
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475 | |
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476 | ret = sigismember(&oldset, SIGTERM); |
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477 | if(ret < 0) { abort("ERROR sigismember returned %d", ret); } |
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478 | if(ret == 1) { abort("ERROR SIGTERM is disabled"); } |
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479 | } |
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480 | |
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481 | // Local Variables: // |
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482 | // mode: c // |
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483 | // tab-width: 4 // |
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484 | // End: // |
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