threads.cc

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