[c81ebf9] | 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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[6b0b624] | 11 | // Last Modified By : Peter A. Buhr |
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[2b8bc41] | 12 | // Last Modified On : Tue Feb 6 15:00:36 2018 |
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| 13 | // Update Count : 10 |
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[c81ebf9] | 14 | // |
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| 15 | |
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| 16 | #include "preemption.h" |
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| 17 | |
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[b158d8f] | 18 | #define ftype `ftype` |
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[c81ebf9] | 19 | extern "C" { |
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[82ff5845] | 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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[c81ebf9] | 24 | } |
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[b158d8f] | 25 | #undef ftype |
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[c81ebf9] | 26 | |
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[dbe9b08] | 27 | #include "bits/signal.h" |
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[82ff5845] | 28 | |
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[969b3fe] | 29 | //TODO move to defaults |
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[82ff5845] | 30 | #define __CFA_DEFAULT_PREEMPTION__ 10000 |
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[c81ebf9] | 31 | |
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[969b3fe] | 32 | //TODO move to defaults |
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[c81ebf9] | 33 | __attribute__((weak)) unsigned int default_preemption() { |
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| 34 | return __CFA_DEFAULT_PREEMPTION__; |
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| 35 | } |
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| 36 | |
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[969b3fe] | 37 | // FwdDeclarations : timeout handlers |
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[c81ebf9] | 38 | static void preempt( processor * this ); |
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| 39 | static void timeout( thread_desc * this ); |
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| 40 | |
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[969b3fe] | 41 | // FwdDeclarations : Signal handlers |
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[82ff5845] | 42 | void sigHandler_ctxSwitch( __CFA_SIGPARMS__ ); |
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[1c273d0] | 43 | void sigHandler_segv ( __CFA_SIGPARMS__ ); |
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[2b8bc41] | 44 | void sigHandler_ill ( __CFA_SIGPARMS__ ); |
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| 45 | void sigHandler_fpe ( __CFA_SIGPARMS__ ); |
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[1c273d0] | 46 | void sigHandler_abort ( __CFA_SIGPARMS__ ); |
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[82ff5845] | 47 | |
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[969b3fe] | 48 | // FwdDeclarations : alarm thread main |
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| 49 | void * alarm_loop( __attribute__((unused)) void * args ); |
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| 50 | |
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| 51 | // Machine specific register name |
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[b158d8f] | 52 | #if defined(__x86_64__) |
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[b2b44d8] | 53 | #define CFA_REG_IP gregs[REG_RIP] |
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[b158d8f] | 54 | #elif defined(__i386__) |
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[b2b44d8] | 55 | #define CFA_REG_IP gregs[REG_EIP] |
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[b158d8f] | 56 | #elif defined(__ARM_ARCH__) |
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[b2b44d8] | 57 | #define CFA_REG_IP arm_pc |
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[cd17862] | 58 | #endif |
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| 59 | |
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[969b3fe] | 60 | KERNEL_STORAGE(event_kernel_t, event_kernel); // private storage for event kernel |
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| 61 | event_kernel_t * event_kernel; // kernel public handle to even kernel |
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| 62 | static pthread_t alarm_thread; // pthread handle to alarm thread |
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| 63 | |
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[65deb18] | 64 | void ?{}(event_kernel_t & this) with( this ) { |
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| 65 | alarms{}; |
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| 66 | lock{}; |
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[969b3fe] | 67 | } |
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[82ff5845] | 68 | |
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[c81ebf9] | 69 | //============================================================================================= |
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| 70 | // Kernel Preemption logic |
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| 71 | //============================================================================================= |
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| 72 | |
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[969b3fe] | 73 | // Get next expired node |
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| 74 | static inline alarm_node_t * get_expired( alarm_list_t * alarms, __cfa_time_t currtime ) { |
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| 75 | if( !alarms->head ) return NULL; // If no alarms return null |
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| 76 | if( alarms->head->alarm >= currtime ) return NULL; // If alarms head not expired return null |
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| 77 | return pop(alarms); // Otherwise just pop head |
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| 78 | } |
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| 79 | |
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| 80 | // Tick one frame of the Discrete Event Simulation for alarms |
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[c81ebf9] | 81 | void tick_preemption() { |
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[969b3fe] | 82 | alarm_node_t * node = NULL; // Used in the while loop but cannot be declared in the while condition |
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| 83 | alarm_list_t * alarms = &event_kernel->alarms; // Local copy for ease of reading |
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| 84 | __cfa_time_t currtime = __kernel_get_time(); // Check current time once so we everything "happens at once" |
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[8cb529e] | 85 | |
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[969b3fe] | 86 | //Loop throught every thing expired |
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| 87 | while( node = get_expired( alarms, currtime ) ) { |
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[1c273d0] | 88 | |
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[969b3fe] | 89 | // Check if this is a kernel |
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[c81ebf9] | 90 | if( node->kernel_alarm ) { |
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| 91 | preempt( node->proc ); |
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| 92 | } |
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| 93 | else { |
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| 94 | timeout( node->thrd ); |
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| 95 | } |
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| 96 | |
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[969b3fe] | 97 | // Check if this is a periodic alarm |
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[8cb529e] | 98 | __cfa_time_t period = node->period; |
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| 99 | if( period > 0 ) { |
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[969b3fe] | 100 | node->alarm = currtime + period; // Alarm is periodic, add currtime to it (used cached current time) |
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| 101 | insert( alarms, node ); // Reinsert the node for the next time it triggers |
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[c81ebf9] | 102 | } |
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| 103 | else { |
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[969b3fe] | 104 | node->set = false; // Node is one-shot, just mark it as not pending |
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[c81ebf9] | 105 | } |
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| 106 | } |
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| 107 | |
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[969b3fe] | 108 | // If there are still alarms pending, reset the timer |
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| 109 | if( alarms->head ) { __kernel_set_timer( alarms->head->alarm - currtime ); } |
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[c81ebf9] | 110 | } |
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| 111 | |
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[969b3fe] | 112 | // Update the preemption of a processor and notify interested parties |
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[c81ebf9] | 113 | void update_preemption( processor * this, __cfa_time_t duration ) { |
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| 114 | alarm_node_t * alarm = this->preemption_alarm; |
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| 115 | |
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| 116 | // Alarms need to be enabled |
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| 117 | if ( duration > 0 && !alarm->set ) { |
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| 118 | alarm->alarm = __kernel_get_time() + duration; |
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| 119 | alarm->period = duration; |
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| 120 | register_self( alarm ); |
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| 121 | } |
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| 122 | // Zero duraction but alarm is set |
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| 123 | else if ( duration == 0 && alarm->set ) { |
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| 124 | unregister_self( alarm ); |
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| 125 | alarm->alarm = 0; |
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| 126 | alarm->period = 0; |
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| 127 | } |
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| 128 | // If alarm is different from previous, change it |
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| 129 | else if ( duration > 0 && alarm->period != duration ) { |
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| 130 | unregister_self( alarm ); |
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| 131 | alarm->alarm = __kernel_get_time() + duration; |
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| 132 | alarm->period = duration; |
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| 133 | register_self( alarm ); |
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| 134 | } |
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| 135 | } |
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| 136 | |
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| 137 | //============================================================================================= |
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[cd17862] | 138 | // Kernel Signal Tools |
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[c81ebf9] | 139 | //============================================================================================= |
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| 140 | |
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[36982fc] | 141 | __cfaabi_dbg_debug_do( static thread_local void * last_interrupt = 0; ) |
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[b227f68] | 142 | |
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[82ff5845] | 143 | extern "C" { |
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[969b3fe] | 144 | // Disable interrupts by incrementing the counter |
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[82ff5845] | 145 | void disable_interrupts() { |
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[d0a045c7] | 146 | preemption_enabled = false; |
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| 147 | __attribute__((unused)) unsigned short new_val = disable_preempt_count + 1; |
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| 148 | disable_preempt_count = new_val; |
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[969b3fe] | 149 | verify( new_val < 65_000u ); // If this triggers someone is disabling interrupts without enabling them |
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[82ff5845] | 150 | } |
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| 151 | |
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[969b3fe] | 152 | // Enable interrupts by decrementing the counter |
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| 153 | // If counter reaches 0, execute any pending CtxSwitch |
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[36982fc] | 154 | void enable_interrupts( __cfaabi_dbg_ctx_param ) { |
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[65deb18] | 155 | processor * proc = this_processor; // Cache the processor now since interrupts can start happening after the atomic add |
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[969b3fe] | 156 | thread_desc * thrd = this_thread; // Cache the thread now since interrupts can start happening after the atomic add |
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| 157 | |
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[d0a045c7] | 158 | unsigned short prev = disable_preempt_count; |
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| 159 | disable_preempt_count -= 1; |
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[969b3fe] | 160 | verify( prev != 0u ); // If this triggers someone is enabled already enabled interruptsverify( prev != 0u ); |
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| 161 | |
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| 162 | // Check if we need to prempt the thread because an interrupt was missed |
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[d0a045c7] | 163 | if( prev == 1 ) { |
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| 164 | preemption_enabled = true; |
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| 165 | if( proc->pending_preemption ) { |
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| 166 | proc->pending_preemption = false; |
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| 167 | BlockInternal( thrd ); |
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| 168 | } |
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[82ff5845] | 169 | } |
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[4e6fb8e] | 170 | |
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[969b3fe] | 171 | // For debugging purposes : keep track of the last person to enable the interrupts |
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[36982fc] | 172 | __cfaabi_dbg_debug_do( proc->last_enable = caller; ) |
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[82ff5845] | 173 | } |
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[969b3fe] | 174 | |
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| 175 | // Disable interrupts by incrementint the counter |
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| 176 | // Don't execute any pending CtxSwitch even if counter reaches 0 |
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| 177 | void enable_interrupts_noPoll() { |
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[d0a045c7] | 178 | unsigned short prev = disable_preempt_count; |
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| 179 | disable_preempt_count -= 1; |
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[2e9aed4] | 180 | verifyf( prev != 0u, "Incremented from %u\n", prev ); // If this triggers someone is enabled already enabled interrupts |
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[d0a045c7] | 181 | if( prev == 1 ) { |
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| 182 | preemption_enabled = true; |
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| 183 | } |
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[969b3fe] | 184 | } |
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[82ff5845] | 185 | } |
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| 186 | |
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[969b3fe] | 187 | // sigprocmask wrapper : unblock a single signal |
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[1c273d0] | 188 | static inline void signal_unblock( int sig ) { |
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[82ff5845] | 189 | sigset_t mask; |
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| 190 | sigemptyset( &mask ); |
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[1c273d0] | 191 | sigaddset( &mask, sig ); |
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[82ff5845] | 192 | |
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[47ecf2b] | 193 | if ( pthread_sigmask( SIG_UNBLOCK, &mask, NULL ) == -1 ) { |
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| 194 | abortf( "internal error, pthread_sigmask" ); |
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[cd17862] | 195 | } |
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[82ff5845] | 196 | } |
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| 197 | |
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[969b3fe] | 198 | // sigprocmask wrapper : block a single signal |
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[cd17862] | 199 | static inline void signal_block( int sig ) { |
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| 200 | sigset_t mask; |
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| 201 | sigemptyset( &mask ); |
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| 202 | sigaddset( &mask, sig ); |
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[47ecf2b] | 203 | |
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[cd17862] | 204 | if ( pthread_sigmask( SIG_BLOCK, &mask, NULL ) == -1 ) { |
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| 205 | abortf( "internal error, pthread_sigmask" ); |
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| 206 | } |
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| 207 | } |
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[47ecf2b] | 208 | |
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[969b3fe] | 209 | // kill wrapper : signal a processor |
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[cd17862] | 210 | static void preempt( processor * this ) { |
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| 211 | pthread_kill( this->kernel_thread, SIGUSR1 ); |
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[1c273d0] | 212 | } |
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[82ff5845] | 213 | |
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[969b3fe] | 214 | // reserved for future use |
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[cd17862] | 215 | static void timeout( thread_desc * this ) { |
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| 216 | //TODO : implement waking threads |
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| 217 | } |
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| 218 | |
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[969b3fe] | 219 | |
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| 220 | // Check if a CtxSwitch signal handler shoud defer |
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| 221 | // If true : preemption is safe |
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| 222 | // If false : preemption is unsafe and marked as pending |
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| 223 | static inline bool preemption_ready() { |
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[d0a045c7] | 224 | bool ready = preemption_enabled && !preemption_in_progress; // Check if preemption is safe |
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[969b3fe] | 225 | this_processor->pending_preemption = !ready; // Adjust the pending flag accordingly |
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| 226 | return ready; |
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| 227 | } |
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| 228 | |
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[cd17862] | 229 | //============================================================================================= |
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| 230 | // Kernel Signal Startup/Shutdown logic |
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| 231 | //============================================================================================= |
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| 232 | |
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[969b3fe] | 233 | // Startup routine to activate preemption |
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| 234 | // Called from kernel_startup |
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[cd17862] | 235 | void kernel_start_preemption() { |
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[36982fc] | 236 | __cfaabi_dbg_print_safe("Kernel : Starting preemption\n"); |
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[969b3fe] | 237 | |
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| 238 | // Start with preemption disabled until ready |
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[d0a045c7] | 239 | preemption_enabled = false; |
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[969b3fe] | 240 | disable_preempt_count = 1; |
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| 241 | |
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| 242 | // Initialize the event kernel |
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| 243 | event_kernel = (event_kernel_t *)&storage_event_kernel; |
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[9236060] | 244 | (*event_kernel){}; |
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[969b3fe] | 245 | |
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| 246 | // Setup proper signal handlers |
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[2b8bc41] | 247 | __cfaabi_sigaction( SIGUSR1, sigHandler_ctxSwitch, SA_SIGINFO | SA_RESTART ); // CtxSwitch handler |
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[cd17862] | 248 | |
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| 249 | signal_block( SIGALRM ); |
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| 250 | |
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| 251 | pthread_create( &alarm_thread, NULL, alarm_loop, NULL ); |
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| 252 | } |
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| 253 | |
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[969b3fe] | 254 | // Shutdown routine to deactivate preemption |
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| 255 | // Called from kernel_shutdown |
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[cd17862] | 256 | void kernel_stop_preemption() { |
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[36982fc] | 257 | __cfaabi_dbg_print_safe("Kernel : Preemption stopping\n"); |
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[d6ff3ff] | 258 | |
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[969b3fe] | 259 | // Block all signals since we are already shutting down |
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[cd17862] | 260 | sigset_t mask; |
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| 261 | sigfillset( &mask ); |
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| 262 | sigprocmask( SIG_BLOCK, &mask, NULL ); |
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| 263 | |
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[969b3fe] | 264 | // Notify the alarm thread of the shutdown |
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[a0b3e32] | 265 | sigval val = { 1 }; |
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| 266 | pthread_sigqueue( alarm_thread, SIGALRM, val ); |
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[969b3fe] | 267 | |
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| 268 | // Wait for the preemption thread to finish |
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[cd17862] | 269 | pthread_join( alarm_thread, NULL ); |
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[969b3fe] | 270 | |
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| 271 | // Preemption is now fully stopped |
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| 272 | |
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[36982fc] | 273 | __cfaabi_dbg_print_safe("Kernel : Preemption stopped\n"); |
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[cd17862] | 274 | } |
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| 275 | |
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[969b3fe] | 276 | // Raii ctor/dtor for the preemption_scope |
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| 277 | // Used by thread to control when they want to receive preemption signals |
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[242a902] | 278 | void ?{}( preemption_scope & this, processor * proc ) { |
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[9236060] | 279 | (this.alarm){ proc, zero_time, zero_time }; |
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[242a902] | 280 | this.proc = proc; |
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| 281 | this.proc->preemption_alarm = &this.alarm; |
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[969b3fe] | 282 | |
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[9236060] | 283 | update_preemption( this.proc, from_us(this.proc->cltr->preemption) ); |
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[cd17862] | 284 | } |
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| 285 | |
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[242a902] | 286 | void ^?{}( preemption_scope & this ) { |
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[cd17862] | 287 | disable_interrupts(); |
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| 288 | |
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[9236060] | 289 | update_preemption( this.proc, zero_time ); |
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[cd17862] | 290 | } |
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| 291 | |
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| 292 | //============================================================================================= |
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| 293 | // Kernel Signal Handlers |
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| 294 | //============================================================================================= |
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[47ecf2b] | 295 | |
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[969b3fe] | 296 | // Context switch signal handler |
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| 297 | // Receives SIGUSR1 signal and causes the current thread to yield |
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[1c273d0] | 298 | void sigHandler_ctxSwitch( __CFA_SIGPARMS__ ) { |
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[b2b44d8] | 299 | __cfaabi_dbg_debug_do( last_interrupt = (void *)(cxt->uc_mcontext.CFA_REG_IP); ) |
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[969b3fe] | 300 | |
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[b2b44d8] | 301 | // Check if it is safe to preempt here |
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[969b3fe] | 302 | if( !preemption_ready() ) { return; } |
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| 303 | |
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[2e9aed4] | 304 | __cfaabi_dbg_print_buffer_decl(" KERNEL: preempting core %p (%p).\n", this_processor, this_thread); |
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[05615ba] | 305 | |
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[969b3fe] | 306 | preemption_in_progress = true; // Sync flag : prevent recursive calls to the signal handler |
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| 307 | signal_unblock( SIGUSR1 ); // We are about to CtxSwitch out of the signal handler, let other handlers in |
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| 308 | preemption_in_progress = false; // Clear the in progress flag |
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| 309 | |
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| 310 | // Preemption can occur here |
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| 311 | |
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| 312 | BlockInternal( (thread_desc*)this_thread ); // Do the actual CtxSwitch |
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[c81ebf9] | 313 | } |
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| 314 | |
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[969b3fe] | 315 | // Main of the alarm thread |
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| 316 | // Waits on SIGALRM and send SIGUSR1 to whom ever needs it |
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[cd17862] | 317 | void * alarm_loop( __attribute__((unused)) void * args ) { |
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[969b3fe] | 318 | // Block sigalrms to control when they arrive |
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[cd17862] | 319 | sigset_t mask; |
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| 320 | sigemptyset( &mask ); |
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| 321 | sigaddset( &mask, SIGALRM ); |
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| 322 | |
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| 323 | if ( pthread_sigmask( SIG_BLOCK, &mask, NULL ) == -1 ) { |
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| 324 | abortf( "internal error, pthread_sigmask" ); |
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[82ff5845] | 325 | } |
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[c81ebf9] | 326 | |
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[969b3fe] | 327 | // Main loop |
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[cd17862] | 328 | while( true ) { |
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[969b3fe] | 329 | // Wait for a sigalrm |
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[a0b3e32] | 330 | siginfo_t info; |
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| 331 | int sig = sigwaitinfo( &mask, &info ); |
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[969b3fe] | 332 | |
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[e2f7bc3] | 333 | if( sig < 0 ) { |
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| 334 | //Error! |
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| 335 | int err = errno; |
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| 336 | switch( err ) { |
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| 337 | case EAGAIN : |
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| 338 | case EINTR : |
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| 339 | continue; |
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| 340 | case EINVAL : |
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| 341 | abortf("Timeout was invalid."); |
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| 342 | default: |
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| 343 | abortf("Unhandled error %d", err); |
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| 344 | } |
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| 345 | } |
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| 346 | |
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[969b3fe] | 347 | // If another signal arrived something went wrong |
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[8cb529e] | 348 | 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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| 349 | |
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[36982fc] | 350 | // __cfaabi_dbg_print_safe("Kernel : Caught alarm from %d with %d\n", info.si_code, info.si_value.sival_int ); |
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[969b3fe] | 351 | // Switch on the code (a.k.a. the sender) to |
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[8cb529e] | 352 | switch( info.si_code ) |
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[a0b3e32] | 353 | { |
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[969b3fe] | 354 | // Timers can apparently be marked as sent for the kernel |
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| 355 | // In either case, tick preemption |
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[8cb529e] | 356 | case SI_TIMER: |
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| 357 | case SI_KERNEL: |
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[36982fc] | 358 | // __cfaabi_dbg_print_safe("Kernel : Preemption thread tick\n"); |
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| 359 | lock( event_kernel->lock __cfaabi_dbg_ctx2 ); |
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[8cb529e] | 360 | tick_preemption(); |
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[ea7d2b0] | 361 | unlock( event_kernel->lock ); |
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[8cb529e] | 362 | break; |
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[969b3fe] | 363 | // Signal was not sent by the kernel but by an other thread |
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[8cb529e] | 364 | case SI_QUEUE: |
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[969b3fe] | 365 | // For now, other thread only signal the alarm thread to shut it down |
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| 366 | // If this needs to change use info.si_value and handle the case here |
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[8cb529e] | 367 | goto EXIT; |
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[cd17862] | 368 | } |
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| 369 | } |
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[a0b3e32] | 370 | |
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[8cb529e] | 371 | EXIT: |
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[36982fc] | 372 | __cfaabi_dbg_print_safe("Kernel : Preemption thread stopping\n"); |
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[a0b3e32] | 373 | return NULL; |
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[82ff5845] | 374 | } |
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| 375 | |
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[6b0b624] | 376 | // Local Variables: // |
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| 377 | // mode: c // |
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| 378 | // tab-width: 4 // |
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| 379 | // End: // |
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