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 : Fri Nov 6 07:42:13 2020 |
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13 | // Update Count : 54 |
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14 | // |
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15 | |
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16 | #define __cforall_thread__ |
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17 | |
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18 | #include "preemption.hfa" |
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19 | #include <assert.h> |
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20 | |
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21 | #include <errno.h> |
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22 | #include <stdio.h> |
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23 | #include <string.h> |
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24 | #include <unistd.h> |
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25 | #include <limits.h> // PTHREAD_STACK_MIN |
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26 | |
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27 | #include "bits/signal.hfa" |
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28 | #include "kernel_private.hfa" |
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29 | |
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30 | #if !defined(__CFA_DEFAULT_PREEMPTION__) |
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31 | #define __CFA_DEFAULT_PREEMPTION__ 10`ms |
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32 | #endif |
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33 | |
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34 | Duration default_preemption() __attribute__((weak)) { |
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35 | return __CFA_DEFAULT_PREEMPTION__; |
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36 | } |
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37 | |
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38 | // FwdDeclarations : timeout handlers |
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39 | static void preempt( processor * this ); |
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40 | static void timeout( $thread * this ); |
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41 | |
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42 | // FwdDeclarations : Signal handlers |
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43 | static void sigHandler_ctxSwitch( __CFA_SIGPARMS__ ); |
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44 | static void sigHandler_alarm ( __CFA_SIGPARMS__ ); |
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45 | static void sigHandler_segv ( __CFA_SIGPARMS__ ); |
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46 | static void sigHandler_ill ( __CFA_SIGPARMS__ ); |
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47 | static void sigHandler_fpe ( __CFA_SIGPARMS__ ); |
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48 | static void sigHandler_abort ( __CFA_SIGPARMS__ ); |
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49 | |
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50 | // FwdDeclarations : alarm thread main |
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51 | static void * alarm_loop( __attribute__((unused)) void * args ); |
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52 | |
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53 | // Machine specific register name |
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54 | #if defined( __i386 ) |
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55 | #define CFA_REG_IP gregs[REG_EIP] |
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56 | #elif defined( __x86_64 ) |
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57 | #define CFA_REG_IP gregs[REG_RIP] |
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58 | #elif defined( __arm__ ) |
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59 | #define CFA_REG_IP arm_pc |
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60 | #elif defined( __aarch64__ ) |
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61 | #define CFA_REG_IP pc |
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62 | #else |
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63 | #error unsupported hardware architecture |
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64 | #endif |
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65 | |
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66 | KERNEL_STORAGE(event_kernel_t, event_kernel); // private storage for event kernel |
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67 | event_kernel_t * event_kernel; // kernel public handle to even kernel |
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68 | static pthread_t alarm_thread; // pthread handle to alarm thread |
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69 | static void * alarm_stack; // pthread stack for alarm thread |
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70 | |
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71 | static void ?{}(event_kernel_t & this) with( this ) { |
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72 | alarms{}; |
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73 | lock{}; |
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74 | } |
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75 | |
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76 | enum { |
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77 | PREEMPT_NORMAL = 0, |
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78 | PREEMPT_TERMINATE = 1, |
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79 | }; |
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80 | |
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81 | //============================================================================================= |
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82 | // Kernel Preemption logic |
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83 | //============================================================================================= |
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84 | |
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85 | // Get next expired node |
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86 | static inline alarm_node_t * get_expired( alarm_list_t * alarms, Time currtime ) { |
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87 | if( ! & (*alarms)`first ) return 0p; // If no alarms return null |
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88 | if( (*alarms)`first.alarm >= currtime ) return 0p; // If alarms head not expired return null |
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89 | return pop(alarms); // Otherwise just pop head |
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90 | } |
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91 | |
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92 | // Tick one frame of the Discrete Event Simulation for alarms |
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93 | static void tick_preemption(void) { |
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94 | alarm_node_t * node = 0p; // Used in the while loop but cannot be declared in the while condition |
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95 | alarm_list_t * alarms = &event_kernel->alarms; // Local copy for ease of reading |
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96 | Time currtime = __kernel_get_time(); // Check current time once so everything "happens at once" |
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97 | |
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98 | //Loop throught every thing expired |
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99 | while( node = get_expired( alarms, currtime ) ) { |
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100 | // __cfaabi_dbg_print_buffer_decl( " KERNEL: preemption tick.\n" ); |
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101 | Duration period = node->period; |
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102 | if( period == 0) { |
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103 | node->set = false; // Node is one-shot, just mark it as not pending |
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104 | } |
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105 | |
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106 | // Check if this is a kernel |
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107 | if( node->type == Kernel ) { |
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108 | preempt( node->proc ); |
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109 | } |
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110 | else if( node->type == User ) { |
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111 | timeout( node->thrd ); |
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112 | } |
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113 | else { |
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114 | node->callback(*node); |
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115 | } |
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116 | |
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117 | // Check if this is a periodic alarm |
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118 | if( period > 0 ) { |
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119 | // __cfaabi_dbg_print_buffer_local( " KERNEL: alarm period is %lu.\n", period.tv ); |
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120 | node->alarm = currtime + period; // Alarm is periodic, add currtime to it (used cached current time) |
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121 | insert( alarms, node ); // Reinsert the node for the next time it triggers |
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122 | } |
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123 | } |
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124 | |
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125 | // If there are still alarms pending, reset the timer |
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126 | if( & (*alarms)`first ) { |
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127 | __cfadbg_print_buffer_decl(preemption, " KERNEL: @%ju(%ju) resetting alarm to %ju.\n", currtime.tv, __kernel_get_time().tv, (alarms->head->alarm - currtime).tv); |
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128 | Duration delta = (*alarms)`first.alarm - currtime; |
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129 | Duration capped = max(delta, 50`us); |
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130 | // itimerval tim = { caped }; |
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131 | // __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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132 | |
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133 | __kernel_set_timer( capped ); |
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134 | } |
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135 | } |
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136 | |
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137 | // Update the preemption of a processor and notify interested parties |
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138 | void update_preemption( processor * this, Duration duration ) { |
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139 | alarm_node_t * alarm = this->preemption_alarm; |
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140 | |
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141 | // Alarms need to be enabled |
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142 | if ( duration > 0 && ! alarm->set ) { |
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143 | alarm->alarm = __kernel_get_time() + duration; |
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144 | alarm->period = duration; |
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145 | register_self( alarm ); |
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146 | } |
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147 | // Zero duration but alarm is set |
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148 | else if ( duration == 0 && alarm->set ) { |
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149 | unregister_self( alarm ); |
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150 | alarm->alarm = 0; |
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151 | alarm->period = 0; |
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152 | } |
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153 | // If alarm is different from previous, change it |
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154 | else if ( duration > 0 && alarm->period != duration ) { |
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155 | unregister_self( alarm ); |
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156 | alarm->alarm = __kernel_get_time() + duration; |
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157 | alarm->period = duration; |
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158 | register_self( alarm ); |
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159 | } |
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160 | } |
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161 | |
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162 | //============================================================================================= |
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163 | // Kernel Signal Tools |
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164 | //============================================================================================= |
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165 | // In a user-level threading system, there are handful of thread-local variables where this problem occurs on the ARM. |
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166 | // |
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167 | // For each kernel thread running user-level threads, there is a flag variable to indicate if interrupts are |
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168 | // enabled/disabled for that kernel thread. Therefore, this variable is made thread local. |
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169 | // |
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170 | // For example, this code fragment sets the state of the "interrupt" variable in thread-local memory. |
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171 | // |
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172 | // _Thread_local volatile int interrupts; |
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173 | // int main() { |
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174 | // interrupts = 0; // disable interrupts } |
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175 | // |
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176 | // which generates the following code on the ARM |
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177 | // |
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178 | // (gdb) disassemble main |
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179 | // Dump of assembler code for function main: |
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180 | // 0x0000000000000610 <+0>: mrs x1, tpidr_el0 |
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181 | // 0x0000000000000614 <+4>: mov w0, #0x0 // #0 |
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182 | // 0x0000000000000618 <+8>: add x1, x1, #0x0, lsl #12 |
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183 | // 0x000000000000061c <+12>: add x1, x1, #0x10 |
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184 | // 0x0000000000000620 <+16>: str wzr, [x1] |
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185 | // 0x0000000000000624 <+20>: ret |
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186 | // |
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187 | // The mrs moves a pointer from coprocessor register tpidr_el0 into register x1. Register w0 is set to 0. The two adds |
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188 | // increase the TLS pointer with the displacement (offset) 0x10, which is the location in the TSL of variable |
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189 | // "interrupts". Finally, 0 is stored into "interrupts" through the pointer in register x1 that points into the |
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190 | // TSL. Now once x1 has the pointer to the location of the TSL for kernel thread N, it can be be preempted at a |
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191 | // user-level and the user thread is put on the user-level ready-queue. When the preempted thread gets to the front of |
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192 | // the user-level ready-queue it is run on kernel thread M. It now stores 0 into "interrupts" back on kernel thread N, |
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193 | // turning off interrupt on the wrong kernel thread. |
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194 | // |
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195 | // On the x86, the following code is generated for the same code fragment. |
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196 | // |
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197 | // (gdb) disassemble main |
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198 | // Dump of assembler code for function main: |
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199 | // 0x0000000000400420 <+0>: movl $0x0,%fs:0xfffffffffffffffc |
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200 | // 0x000000000040042c <+12>: xor %eax,%eax |
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201 | // 0x000000000040042e <+14>: retq |
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202 | // |
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203 | // and there is base-displacement addressing used to atomically reset variable "interrupts" off of the TSL pointer in |
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204 | // register "fs". |
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205 | // |
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206 | // Hence, the ARM has base-displacement address for the general purpose registers, BUT not to the coprocessor |
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207 | // registers. As a result, generating the address for the write into variable "interrupts" is no longer atomic. |
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208 | // |
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209 | // Note this problem does NOT occur when just using multiple kernel threads because the preemption ALWAYS restarts the |
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210 | // thread on the same kernel thread. |
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211 | // |
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212 | // The obvious question is why does ARM use a coprocessor register to store the TSL pointer given that coprocessor |
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213 | // registers are second-class registers with respect to the instruction set. One possible answer is that they did not |
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214 | // want to dedicate one of the general registers to hold the TLS pointer and there was a free coprocessor register |
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215 | // available. |
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216 | |
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217 | //----------------------------------------------------------------------------- |
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218 | // Some assembly required |
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219 | #define __cfaasm_label(label, when) when: asm volatile goto(".global __cfaasm_" #label "_" #when "\n" "__cfaasm_" #label "_" #when ":":::"memory":when) |
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220 | |
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221 | //---------- |
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222 | // special case for preemption since used often |
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223 | bool __preemption_enabled() { |
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224 | // create a assembler label before |
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225 | // marked as clobber all to avoid movement |
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226 | __cfaasm_label(check, before); |
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227 | |
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228 | // access tls as normal |
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229 | bool enabled = __cfaabi_tls.preemption_state.enabled; |
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230 | |
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231 | // create a assembler label after |
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232 | // marked as clobber all to avoid movement |
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233 | __cfaasm_label(check, after); |
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234 | return enabled; |
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235 | } |
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236 | |
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237 | struct asm_region { |
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238 | void * before; |
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239 | void * after; |
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240 | }; |
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241 | |
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242 | static inline bool __cfaasm_in( void * ip, struct asm_region & region ) { |
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243 | return ip >= region.before && ip <= region.after; |
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244 | } |
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245 | |
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246 | |
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247 | //---------- |
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248 | // Get data from the TLS block |
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249 | // struct asm_region __cfaasm_get; |
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250 | uintptr_t __cfatls_get( unsigned long int offset ) __attribute__((__noinline__)); //no inline to avoid problems |
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251 | uintptr_t __cfatls_get( unsigned long int offset ) { |
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252 | // create a assembler label before |
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253 | // marked as clobber all to avoid movement |
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254 | __cfaasm_label(get, before); |
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255 | |
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256 | // access tls as normal (except for pointer arithmetic) |
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257 | uintptr_t val = *(uintptr_t*)((uintptr_t)&__cfaabi_tls + offset); |
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258 | |
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259 | // create a assembler label after |
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260 | // marked as clobber all to avoid movement |
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261 | __cfaasm_label(get, after); |
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262 | return val; |
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263 | } |
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264 | |
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265 | extern "C" { |
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266 | // Disable interrupts by incrementing the counter |
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267 | void disable_interrupts() { |
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268 | // create a assembler label before |
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269 | // marked as clobber all to avoid movement |
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270 | __cfaasm_label(dsable, before); |
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271 | |
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272 | with( __cfaabi_tls.preemption_state ) { |
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273 | #if GCC_VERSION > 50000 |
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274 | static_assert(__atomic_always_lock_free(sizeof(enabled), &enabled), "Must be lock-free"); |
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275 | #endif |
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276 | |
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277 | // Set enabled flag to false |
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278 | // should be atomic to avoid preemption in the middle of the operation. |
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279 | // use memory order RELAXED since there is no inter-thread on this variable requirements |
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280 | __atomic_store_n(&enabled, false, __ATOMIC_RELAXED); |
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281 | |
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282 | // Signal the compiler that a fence is needed but only for signal handlers |
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283 | __atomic_signal_fence(__ATOMIC_ACQUIRE); |
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284 | |
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285 | __attribute__((unused)) unsigned short new_val = disable_count + 1; |
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286 | disable_count = new_val; |
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287 | verify( new_val < 65_000u ); // If this triggers someone is disabling interrupts without enabling them |
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288 | } |
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289 | |
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290 | // create a assembler label after |
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291 | // marked as clobber all to avoid movement |
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292 | __cfaasm_label(dsable, after); |
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293 | |
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294 | } |
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295 | |
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296 | // Enable interrupts by decrementing the counter |
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297 | // If counter reaches 0, execute any pending __cfactx_switch |
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298 | void enable_interrupts( __cfaabi_dbg_ctx_param ) { |
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299 | // Cache the processor now since interrupts can start happening after the atomic store |
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300 | processor * proc = __cfaabi_tls.this_processor; |
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301 | /* paranoid */ verify( proc ); |
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302 | |
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303 | with( __cfaabi_tls.preemption_state ){ |
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304 | unsigned short prev = disable_count; |
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305 | disable_count -= 1; |
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306 | |
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307 | // If this triggers someone is enabled already enabled interruptsverify( prev != 0u ); |
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308 | /* paranoid */ verify( prev != 0u ); |
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309 | |
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310 | // Check if we need to prempt the thread because an interrupt was missed |
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311 | if( prev == 1 ) { |
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312 | #if GCC_VERSION > 50000 |
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313 | static_assert(__atomic_always_lock_free(sizeof(enabled), &enabled), "Must be lock-free"); |
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314 | #endif |
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315 | |
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316 | // Set enabled flag to true |
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317 | // should be atomic to avoid preemption in the middle of the operation. |
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318 | // use memory order RELAXED since there is no inter-thread on this variable requirements |
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319 | __atomic_store_n(&enabled, true, __ATOMIC_RELAXED); |
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320 | |
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321 | // Signal the compiler that a fence is needed but only for signal handlers |
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322 | __atomic_signal_fence(__ATOMIC_RELEASE); |
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323 | if( proc->pending_preemption ) { |
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324 | proc->pending_preemption = false; |
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325 | force_yield( __POLL_PREEMPTION ); |
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326 | } |
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327 | } |
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328 | } |
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329 | |
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330 | // For debugging purposes : keep track of the last person to enable the interrupts |
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331 | __cfaabi_dbg_debug_do( proc->last_enable = caller; ) |
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332 | } |
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333 | |
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334 | // Disable interrupts by incrementint the counter |
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335 | // Don't execute any pending __cfactx_switch even if counter reaches 0 |
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336 | void enable_interrupts_noPoll() { |
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337 | unsigned short prev = __cfaabi_tls.preemption_state.disable_count; |
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338 | __cfaabi_tls.preemption_state.disable_count -= 1; |
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339 | // If this triggers someone is enabled already enabled interrupts |
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340 | /* paranoid */ verifyf( prev != 0u, "Incremented from %u\n", prev ); |
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341 | if( prev == 1 ) { |
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342 | #if GCC_VERSION > 50000 |
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343 | static_assert(__atomic_always_lock_free(sizeof(__cfaabi_tls.preemption_state.enabled), &__cfaabi_tls.preemption_state.enabled), "Must be lock-free"); |
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344 | #endif |
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345 | // Set enabled flag to true |
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346 | // should be atomic to avoid preemption in the middle of the operation. |
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347 | // use memory order RELAXED since there is no inter-thread on this variable requirements |
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348 | __atomic_store_n(&__cfaabi_tls.preemption_state.enabled, true, __ATOMIC_RELAXED); |
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349 | |
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350 | // Signal the compiler that a fence is needed but only for signal handlers |
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351 | __atomic_signal_fence(__ATOMIC_RELEASE); |
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352 | } |
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353 | } |
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354 | } |
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355 | |
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356 | //----------------------------------------------------------------------------- |
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357 | // Kernel Signal Debug |
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358 | void __cfaabi_check_preemption() { |
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359 | bool ready = __preemption_enabled(); |
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360 | if(!ready) { abort("Preemption should be ready"); } |
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361 | |
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362 | __cfaasm_label(debug, before); |
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363 | |
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364 | sigset_t oldset; |
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365 | int ret; |
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366 | ret = pthread_sigmask(0, ( const sigset_t * ) 0p, &oldset); // workaround trac#208: cast should be unnecessary |
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367 | if(ret != 0) { abort("ERROR sigprocmask returned %d", ret); } |
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368 | |
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369 | ret = sigismember(&oldset, SIGUSR1); |
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370 | if(ret < 0) { abort("ERROR sigismember returned %d", ret); } |
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371 | if(ret == 1) { abort("ERROR SIGUSR1 is disabled"); } |
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372 | |
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373 | ret = sigismember(&oldset, SIGALRM); |
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374 | if(ret < 0) { abort("ERROR sigismember returned %d", ret); } |
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375 | if(ret == 0) { abort("ERROR SIGALRM is enabled"); } |
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376 | |
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377 | ret = sigismember(&oldset, SIGTERM); |
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378 | if(ret < 0) { abort("ERROR sigismember returned %d", ret); } |
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379 | if(ret == 1) { abort("ERROR SIGTERM is disabled"); } |
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380 | |
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381 | __cfaasm_label(debug, after); |
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382 | } |
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383 | |
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384 | #ifdef __CFA_WITH_VERIFY__ |
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385 | bool __cfaabi_dbg_in_kernel() { |
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386 | return !__preemption_enabled(); |
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387 | } |
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388 | #endif |
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389 | |
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390 | #undef __cfaasm_label |
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391 | |
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392 | //----------------------------------------------------------------------------- |
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393 | // Signal handling |
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394 | |
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395 | // sigprocmask wrapper : unblock a single signal |
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396 | static inline void signal_unblock( int sig ) { |
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397 | sigset_t mask; |
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398 | sigemptyset( &mask ); |
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399 | sigaddset( &mask, sig ); |
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400 | |
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401 | if ( pthread_sigmask( SIG_UNBLOCK, &mask, 0p ) == -1 ) { |
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402 | abort( "internal error, pthread_sigmask" ); |
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403 | } |
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404 | } |
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405 | |
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406 | // sigprocmask wrapper : block a single signal |
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407 | static inline void signal_block( int sig ) { |
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408 | sigset_t mask; |
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409 | sigemptyset( &mask ); |
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410 | sigaddset( &mask, sig ); |
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411 | |
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412 | if ( pthread_sigmask( SIG_BLOCK, &mask, 0p ) == -1 ) { |
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413 | abort( "internal error, pthread_sigmask" ); |
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414 | } |
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415 | } |
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416 | |
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417 | // kill wrapper : signal a processor |
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418 | static void preempt( processor * this ) { |
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419 | sigval_t value = { PREEMPT_NORMAL }; |
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420 | pthread_sigqueue( this->kernel_thread, SIGUSR1, value ); |
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421 | } |
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422 | |
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423 | // reserved for future use |
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424 | static void timeout( $thread * this ) { |
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425 | unpark( this ); |
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426 | } |
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427 | |
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428 | //----------------------------------------------------------------------------- |
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429 | // Some assembly required |
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430 | #if defined( __i386 ) |
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431 | #ifdef __PIC__ |
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432 | #define RELOC_PRELUDE( label ) \ |
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433 | "calll .Lcfaasm_prelude_" #label "$pb\n\t" \ |
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434 | ".Lcfaasm_prelude_" #label "$pb:\n\t" \ |
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435 | "popl %%eax\n\t" \ |
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436 | ".Lcfaasm_prelude_" #label "_end:\n\t" \ |
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437 | "addl $_GLOBAL_OFFSET_TABLE_+(.Lcfaasm_prelude_" #label "_end-.Lcfaasm_prelude_" #label "$pb), %%eax\n\t" |
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438 | #define RELOC_PREFIX "" |
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439 | #define RELOC_SUFFIX "@GOT(%%eax)" |
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440 | #else |
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441 | #define RELOC_PREFIX "$" |
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442 | #define RELOC_SUFFIX "" |
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443 | #endif |
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444 | #define __cfaasm_label( label ) struct asm_region label = \ |
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445 | ({ \ |
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446 | struct asm_region region; \ |
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447 | asm( \ |
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448 | RELOC_PRELUDE( label ) \ |
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449 | "movl " RELOC_PREFIX "__cfaasm_" #label "_before" RELOC_SUFFIX ", %[vb]\n\t" \ |
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450 | "movl " RELOC_PREFIX "__cfaasm_" #label "_after" RELOC_SUFFIX ", %[va]\n\t" \ |
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451 | : [vb]"=r"(region.before), [va]"=r"(region.after) \ |
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452 | ); \ |
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453 | region; \ |
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454 | }); |
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455 | #elif defined( __x86_64 ) |
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456 | #ifdef __PIC__ |
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457 | #define RELOC_PREFIX "" |
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458 | #define RELOC_SUFFIX "@GOTPCREL(%%rip)" |
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459 | #else |
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460 | #define RELOC_PREFIX "$" |
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461 | #define RELOC_SUFFIX "" |
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462 | #endif |
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463 | #define __cfaasm_label( label ) struct asm_region label = \ |
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464 | ({ \ |
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465 | struct asm_region region; \ |
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466 | asm( \ |
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467 | "movq " RELOC_PREFIX "__cfaasm_" #label "_before" RELOC_SUFFIX ", %[vb]\n\t" \ |
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468 | "movq " RELOC_PREFIX "__cfaasm_" #label "_after" RELOC_SUFFIX ", %[va]\n\t" \ |
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469 | : [vb]"=r"(region.before), [va]"=r"(region.after) \ |
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470 | ); \ |
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471 | region; \ |
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472 | }); |
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473 | #elif defined( __aarch64__ ) |
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474 | #ifdef __PIC__ |
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475 | // Note that this works only for gcc |
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476 | #define __cfaasm_label( label ) struct asm_region label = \ |
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477 | ({ \ |
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478 | struct asm_region region; \ |
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479 | asm( \ |
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480 | "adrp %[vb], _GLOBAL_OFFSET_TABLE_" "\n\t" \ |
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481 | "ldr %[vb], [%[vb], #:gotpage_lo15:__cfaasm_" #label "_before]" "\n\t" \ |
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482 | "adrp %[va], _GLOBAL_OFFSET_TABLE_" "\n\t" \ |
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483 | "ldr %[va], [%[va], #:gotpage_lo15:__cfaasm_" #label "_after]" "\n\t" \ |
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484 | : [vb]"=r"(region.before), [va]"=r"(region.after) \ |
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485 | ); \ |
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486 | region; \ |
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487 | }); |
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488 | #else |
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489 | #error this is not the right thing to do |
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490 | /* |
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491 | #define __cfaasm_label( label ) struct asm_region label = \ |
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492 | ({ \ |
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493 | struct asm_region region; \ |
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494 | asm( \ |
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495 | "adrp %[vb], __cfaasm_" #label "_before" "\n\t" \ |
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496 | "add %[vb], %[vb], :lo12:__cfaasm_" #label "_before" "\n\t" \ |
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497 | "adrp %[va], :got:__cfaasm_" #label "_after" "\n\t" \ |
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498 | "add %[va], %[va], :lo12:__cfaasm_" #label "_after" "\n\t" \ |
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499 | : [vb]"=r"(region.before), [va]"=r"(region.after) \ |
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500 | ); \ |
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501 | region; \ |
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502 | }); |
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503 | */ |
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504 | #endif |
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505 | #else |
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506 | #error unknown hardware architecture |
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507 | #endif |
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508 | |
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509 | // KERNEL ONLY |
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510 | // Check if a __cfactx_switch signal handler shoud defer |
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511 | // If true : preemption is safe |
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512 | // If false : preemption is unsafe and marked as pending |
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513 | static inline bool preemption_ready( void * ip ) { |
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514 | // Get all the region for which it is not safe to preempt |
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515 | __cfaasm_label( get ); |
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516 | __cfaasm_label( check ); |
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517 | __cfaasm_label( dsable ); |
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518 | __cfaasm_label( debug ); |
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519 | |
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520 | // Check if preemption is safe |
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521 | bool ready = true; |
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522 | if( __cfaasm_in( ip, get ) ) { ready = false; goto EXIT; }; |
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523 | if( __cfaasm_in( ip, check ) ) { ready = false; goto EXIT; }; |
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524 | if( __cfaasm_in( ip, dsable ) ) { ready = false; goto EXIT; }; |
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525 | if( __cfaasm_in( ip, debug ) ) { ready = false; goto EXIT; }; |
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526 | if( !__cfaabi_tls.preemption_state.enabled) { ready = false; goto EXIT; }; |
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527 | if( __cfaabi_tls.preemption_state.in_progress ) { ready = false; goto EXIT; }; |
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528 | |
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529 | EXIT: |
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530 | // Adjust the pending flag accordingly |
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531 | __cfaabi_tls.this_processor->pending_preemption = !ready; |
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532 | return ready; |
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533 | } |
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534 | |
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535 | //============================================================================================= |
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536 | // Kernel Signal Startup/Shutdown logic |
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537 | //============================================================================================= |
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538 | |
---|
539 | // Startup routine to activate preemption |
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540 | // Called from kernel_startup |
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541 | void __kernel_alarm_startup() { |
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542 | __cfaabi_dbg_print_safe( "Kernel : Starting preemption\n" ); |
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543 | |
---|
544 | // Start with preemption disabled until ready |
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545 | __cfaabi_tls.preemption_state.enabled = false; |
---|
546 | __cfaabi_tls.preemption_state.disable_count = 1; |
---|
547 | |
---|
548 | // Initialize the event kernel |
---|
549 | event_kernel = (event_kernel_t *)&storage_event_kernel; |
---|
550 | (*event_kernel){}; |
---|
551 | |
---|
552 | // Setup proper signal handlers |
---|
553 | __cfaabi_sigaction( SIGUSR1, sigHandler_ctxSwitch, SA_SIGINFO | SA_RESTART ); // __cfactx_switch handler |
---|
554 | __cfaabi_sigaction( SIGALRM, sigHandler_alarm , SA_SIGINFO | SA_RESTART ); // debug handler |
---|
555 | |
---|
556 | signal_block( SIGALRM ); |
---|
557 | |
---|
558 | alarm_stack = __create_pthread( &alarm_thread, alarm_loop, 0p ); |
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559 | } |
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560 | |
---|
561 | // Shutdown routine to deactivate preemption |
---|
562 | // Called from kernel_shutdown |
---|
563 | void __kernel_alarm_shutdown() { |
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564 | __cfaabi_dbg_print_safe( "Kernel : Preemption stopping\n" ); |
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565 | |
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566 | // Block all signals since we are already shutting down |
---|
567 | sigset_t mask; |
---|
568 | sigfillset( &mask ); |
---|
569 | sigprocmask( SIG_BLOCK, &mask, 0p ); |
---|
570 | |
---|
571 | // Notify the alarm thread of the shutdown |
---|
572 | sigval val = { 1 }; |
---|
573 | pthread_sigqueue( alarm_thread, SIGALRM, val ); |
---|
574 | |
---|
575 | // Wait for the preemption thread to finish |
---|
576 | |
---|
577 | pthread_join( alarm_thread, 0p ); |
---|
578 | free( alarm_stack ); |
---|
579 | |
---|
580 | // Preemption is now fully stopped |
---|
581 | |
---|
582 | __cfaabi_dbg_print_safe( "Kernel : Preemption stopped\n" ); |
---|
583 | } |
---|
584 | |
---|
585 | // Raii ctor/dtor for the preemption_scope |
---|
586 | // Used by thread to control when they want to receive preemption signals |
---|
587 | void ?{}( preemption_scope & this, processor * proc ) { |
---|
588 | (this.alarm){ proc, (Time){ 0 }, 0`s }; |
---|
589 | this.proc = proc; |
---|
590 | this.proc->preemption_alarm = &this.alarm; |
---|
591 | |
---|
592 | update_preemption( this.proc, this.proc->cltr->preemption_rate ); |
---|
593 | } |
---|
594 | |
---|
595 | void ^?{}( preemption_scope & this ) { |
---|
596 | disable_interrupts(); |
---|
597 | |
---|
598 | update_preemption( this.proc, 0`s ); |
---|
599 | } |
---|
600 | |
---|
601 | //============================================================================================= |
---|
602 | // Kernel Signal Handlers |
---|
603 | //============================================================================================= |
---|
604 | __cfaabi_dbg_debug_do( static thread_local void * last_interrupt = 0; ) |
---|
605 | |
---|
606 | // Context switch signal handler |
---|
607 | // Receives SIGUSR1 signal and causes the current thread to yield |
---|
608 | static void sigHandler_ctxSwitch( __CFA_SIGPARMS__ ) { |
---|
609 | void * ip = (void *)(cxt->uc_mcontext.CFA_REG_IP); |
---|
610 | __cfaabi_dbg_debug_do( last_interrupt = ip; ) |
---|
611 | |
---|
612 | // SKULLDUGGERY: if a thread creates a processor and the immediately deletes it, |
---|
613 | // the interrupt that is supposed to force the kernel thread to preempt might arrive |
---|
614 | // before the kernel thread has even started running. When that happens, an interrupt |
---|
615 | // with a null 'this_processor' will be caught, just ignore it. |
---|
616 | if(! __cfaabi_tls.this_processor ) return; |
---|
617 | |
---|
618 | choose(sfp->si_value.sival_int) { |
---|
619 | case PREEMPT_NORMAL : ;// Normal case, nothing to do here |
---|
620 | case PREEMPT_TERMINATE: verify( __atomic_load_n( &__cfaabi_tls.this_processor->do_terminate, __ATOMIC_SEQ_CST ) ); |
---|
621 | default: |
---|
622 | abort( "internal error, signal value is %d", sfp->si_value.sival_int ); |
---|
623 | } |
---|
624 | |
---|
625 | // Check if it is safe to preempt here |
---|
626 | if( !preemption_ready( ip ) ) { return; } |
---|
627 | |
---|
628 | __cfaabi_dbg_print_buffer_decl( " KERNEL: preempting core %p (%p @ %p).\n", __cfaabi_tls.this_processor, __cfaabi_tls.this_thread, (void *)(cxt->uc_mcontext.CFA_REG_IP) ); |
---|
629 | |
---|
630 | // Sync flag : prevent recursive calls to the signal handler |
---|
631 | __cfaabi_tls.preemption_state.in_progress = true; |
---|
632 | |
---|
633 | // Clear sighandler mask before context switching. |
---|
634 | #if GCC_VERSION > 50000 |
---|
635 | static_assert( sizeof( sigset_t ) == sizeof( cxt->uc_sigmask ), "Expected cxt->uc_sigmask to be of sigset_t" ); |
---|
636 | #endif |
---|
637 | if ( pthread_sigmask( SIG_SETMASK, (sigset_t *)&(cxt->uc_sigmask), 0p ) == -1 ) { |
---|
638 | abort( "internal error, sigprocmask" ); |
---|
639 | } |
---|
640 | |
---|
641 | // Clear the in progress flag |
---|
642 | __cfaabi_tls.preemption_state.in_progress = false; |
---|
643 | |
---|
644 | // Preemption can occur here |
---|
645 | |
---|
646 | force_yield( __ALARM_PREEMPTION ); // Do the actual __cfactx_switch |
---|
647 | } |
---|
648 | |
---|
649 | static void sigHandler_alarm( __CFA_SIGPARMS__ ) { |
---|
650 | abort("SIGALRM should never reach the signal handler"); |
---|
651 | } |
---|
652 | |
---|
653 | #if !defined(__CFA_NO_STATISTICS__) |
---|
654 | int __print_alarm_stats = 0; |
---|
655 | #endif |
---|
656 | |
---|
657 | // Main of the alarm thread |
---|
658 | // Waits on SIGALRM and send SIGUSR1 to whom ever needs it |
---|
659 | static void * alarm_loop( __attribute__((unused)) void * args ) { |
---|
660 | __processor_id_t id; |
---|
661 | id.full_proc = false; |
---|
662 | id.id = doregister(&id); |
---|
663 | __cfaabi_tls.this_proc_id = &id; |
---|
664 | |
---|
665 | #if !defined(__CFA_NO_STATISTICS__) |
---|
666 | struct __stats_t local_stats; |
---|
667 | __cfaabi_tls.this_stats = &local_stats; |
---|
668 | __init_stats( &local_stats ); |
---|
669 | #endif |
---|
670 | |
---|
671 | // Block sigalrms to control when they arrive |
---|
672 | sigset_t mask; |
---|
673 | sigfillset(&mask); |
---|
674 | if ( pthread_sigmask( SIG_BLOCK, &mask, 0p ) == -1 ) { |
---|
675 | abort( "internal error, pthread_sigmask" ); |
---|
676 | } |
---|
677 | |
---|
678 | sigemptyset( &mask ); |
---|
679 | sigaddset( &mask, SIGALRM ); |
---|
680 | |
---|
681 | // Main loop |
---|
682 | while( true ) { |
---|
683 | // Wait for a sigalrm |
---|
684 | siginfo_t info; |
---|
685 | int sig = sigwaitinfo( &mask, &info ); |
---|
686 | |
---|
687 | if( sig < 0 ) { |
---|
688 | //Error! |
---|
689 | int err = errno; |
---|
690 | switch( err ) { |
---|
691 | case EAGAIN : |
---|
692 | case EINTR : |
---|
693 | {__cfaabi_dbg_print_buffer_decl( " KERNEL: Spurious wakeup %d.\n", err );} |
---|
694 | continue; |
---|
695 | case EINVAL : |
---|
696 | abort( "Timeout was invalid." ); |
---|
697 | default: |
---|
698 | abort( "Unhandled error %d", err); |
---|
699 | } |
---|
700 | } |
---|
701 | |
---|
702 | // If another signal arrived something went wrong |
---|
703 | assertf(sig == SIGALRM, "Kernel Internal Error, sigwait: Unexpected signal %d (%d : %d)\n", sig, info.si_code, info.si_value.sival_int); |
---|
704 | |
---|
705 | // __cfaabi_dbg_print_safe( "Kernel : Caught alarm from %d with %d\n", info.si_code, info.si_value.sival_int ); |
---|
706 | // Switch on the code (a.k.a. the sender) to |
---|
707 | switch( info.si_code ) |
---|
708 | { |
---|
709 | // Timers can apparently be marked as sent for the kernel |
---|
710 | // In either case, tick preemption |
---|
711 | case SI_TIMER: |
---|
712 | case SI_KERNEL: |
---|
713 | // __cfaabi_dbg_print_safe( "Kernel : Preemption thread tick\n" ); |
---|
714 | lock( event_kernel->lock __cfaabi_dbg_ctx2 ); |
---|
715 | tick_preemption(); |
---|
716 | unlock( event_kernel->lock ); |
---|
717 | break; |
---|
718 | // Signal was not sent by the kernel but by an other thread |
---|
719 | case SI_QUEUE: |
---|
720 | // For now, other thread only signal the alarm thread to shut it down |
---|
721 | // If this needs to change use info.si_value and handle the case here |
---|
722 | goto EXIT; |
---|
723 | } |
---|
724 | } |
---|
725 | |
---|
726 | EXIT: |
---|
727 | __cfaabi_dbg_print_safe( "Kernel : Preemption thread stopping\n" ); |
---|
728 | unregister(&id); |
---|
729 | |
---|
730 | #if !defined(__CFA_NO_STATISTICS__) |
---|
731 | if( 0 != __print_alarm_stats ) { |
---|
732 | __print_stats( &local_stats, __print_alarm_stats, "Alarm", "Thread", 0p ); |
---|
733 | } |
---|
734 | #endif |
---|
735 | return 0p; |
---|
736 | } |
---|
737 | |
---|
738 | // Local Variables: // |
---|
739 | // mode: c // |
---|
740 | // tab-width: 4 // |
---|
741 | // End: // |
---|