libthreads.cc

   1 #include <string.h>
   2 #include <stdlib.h>
   3
   4 #include "libthreads.h"
   5 #include "schedule.h"
   6 #include "common.h"
   7 #include "threads_internal.h"
   8
   9 /* global "model" object */
  10 #include "model.h"
  11
  12 #define STACK_SIZE (1024 * 1024)
  13
  14 static void *stack_allocate(size_t size)
  15 {
  16         return malloc(size);
  17 }
  18
  19 static void stack_free(void *stack)
  20 {
  21         free(stack);
  22 }
  23
  24 static int create_context(struct thread *t)
  25 {
  26         int ret;
  27
  28         memset(&t->context, 0, sizeof(t->context));
  29         ret = getcontext(&t->context);
  30         if (ret)
  31                 return ret;
  32
  33         /* t->start_routine == NULL means this is our initial context */
  34         if (!t->start_routine)
  35                 return 0;
  36
  37         /* Initialize new managed context */
  38         t->stack = stack_allocate(STACK_SIZE);
  39         t->context.uc_stack.ss_sp = t->stack;
  40         t->context.uc_stack.ss_size = STACK_SIZE;
  41         t->context.uc_stack.ss_flags = 0;
  42         t->context.uc_link = &model->system_thread->context;
  43         makecontext(&t->context, t->start_routine, 1, t->arg);
  44
  45         return 0;
  46 }
  47
  48 static int create_initial_thread(struct thread *t)
  49 {
  50         memset(t, 0, sizeof(*t));
  51         model->assign_id(t);
  52         return create_context(t);
  53 }
  54
  55 static int thread_swap(struct thread *t1, struct thread *t2)
  56 {
  57         return swapcontext(&t1->context, &t2->context);
  58 }
  59
  60 static void thread_dispose(struct thread *t)
  61 {
  62         DEBUG("completed thread %d\n", thread_current()->id);
  63         t->state = THREAD_COMPLETED;
  64         stack_free(t->stack);
  65 }
  66
  67 /*
  68  * Return 1 if found next thread, 0 otherwise
  69  */
  70 static int thread_system_next(void)
  71 {
  72         struct thread *curr, *next;
  73
  74         curr = thread_current();
  75         if (curr) {
  76                 if (curr->state == THREAD_READY)
  77                         model->scheduler->add_thread(curr);
  78                 else if (curr->state == THREAD_RUNNING)
  79                         /* Stopped while running; i.e., completed */
  80                         thread_dispose(curr);
  81                 else
  82                         DEBUG("ERROR: current thread in unexpected state??\n");
  83         }
  84         next = model->scheduler->next_thread();
  85         if (next)
  86                 next->state = THREAD_RUNNING;
  87         DEBUG("(%d, %d)\n", curr ? curr->id : -1, next ? next->id : -1);
  88         if (!next)
  89                 return 1;
  90         return thread_swap(model->system_thread, next);
  91 }
  92
  93 static void thread_wait_finish(void)
  94 {
  95
  96         DBG();
  97
  98         while (!thread_system_next());
  99 }
 100
 101 int thread_switch_to_master()
 102 {
 103         struct thread *old, *next;
 104
 105         DBG();
 106         old = thread_current();
 107         old->state = THREAD_READY;
 108         next = model->system_thread;
 109         return thread_swap(old, next);
 110 }
 111
 112 /*
 113  * User program API functions
 114  */
 115 int thread_create(struct thread *t, void (*start_routine)(), void *arg)
 116 {
 117         int ret = 0;
 118
 119         DBG();
 120
 121         memset(t, 0, sizeof(*t));
 122         model->assign_id(t);
 123         DEBUG("create thread %d\n", t->id);
 124
 125         t->start_routine = start_routine;
 126         t->arg = arg;
 127
 128         /* Initialize state */
 129         ret = create_context(t);
 130         if (ret)
 131                 return ret;
 132
 133         t->state = THREAD_CREATED;
 134
 135         model->scheduler->add_thread(t);
 136         return 0;
 137 }
 138
 139 void thread_join(struct thread *t)
 140 {
 141         int ret = 0;
 142         while (t->state != THREAD_COMPLETED && !ret)
 143                 ret = thread_switch_to_master();
 144 }
 145
 146 int thread_yield(void)
 147 {
 148         return thread_switch_to_master();
 149 }
 150
 151 struct thread *thread_current(void)
 152 {
 153         return model->scheduler->get_current_thread();
 154 }
 155
 156 /*
 157  * Main system function
 158  */
 159 int main()
 160 {
 161         struct thread user_thread;
 162         struct thread *main_thread;
 163
 164         model = new ModelChecker();
 165
 166         main_thread = (struct thread *)myMalloc(sizeof(*main_thread));
 167         create_initial_thread(main_thread);
 168         model->add_system_thread(main_thread);
 169
 170         /* Start user program */
 171         thread_create(&user_thread, &user_main, NULL);
 172
 173         /* Wait for all threads to complete */
 174         thread_wait_finish();
 175
 176         delete model;
 177         myFree(main_thread);
 178
 179         DEBUG("Exiting\n");
 180         return 0;
 181 }