threads.cc

   1 #include <stdlib.h>
   2
   3 #include "libthreads.h"
   4 #include "schedule.h"
   5 #include "common.h"
   6 #include "threads.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 Thread::Thread(thrd_t *t, void (*func)(), void *a) {
  64         int ret;
  65
  66         user_thread = t;
  67         start_routine = func;
  68         arg = a;
  69
  70         /* Initialize state */
  71         ret = create_context();
  72         if (ret)
  73                 printf("Error in create_context\n");
  74
  75         state = THREAD_CREATED;
  76         id = model->get_next_id();
  77         *user_thread = id;
  78 }
  79
  80 Thread::Thread(thrd_t *t) {
  81         /* system thread */
  82         user_thread = t;
  83         start_routine = NULL;
  84         arg = NULL;
  85
  86         state = THREAD_CREATED;
  87         id = model->get_next_id();
  88         *user_thread = id;
  89         create_context();
  90         model->add_system_thread(this);
  91 }
  92
  93 thread_id_t Thread::get_id()
  94 {
  95         return id;
  96 }
  97
  98 /*
  99  * Return 1 if found next thread, 0 otherwise
 100  */
 101 static int thread_system_next(void)
 102 {
 103         Thread *curr, *next;
 104
 105         curr = thread_current();
 106         model->check_current_action();
 107         if (curr) {
 108                 if (curr->get_state() == THREAD_READY)
 109                         model->scheduler->add_thread(curr);
 110                 else if (curr->get_state() == THREAD_RUNNING)
 111                         /* Stopped while running; i.e., completed */
 112                         curr->dispose();
 113                 else
 114                         DEBUG("ERROR: current thread in unexpected state??\n");
 115         }
 116         next = model->scheduler->next_thread();
 117         if (next)
 118                 next->set_state(THREAD_RUNNING);
 119         DEBUG("(%d, %d)\n", curr ? curr->get_id() : -1, next ? next->get_id() : -1);
 120         if (!next)
 121                 return 1;
 122         return model->system_thread->swap(next);
 123 }
 124
 125 static void thread_wait_finish(void)
 126 {
 127
 128         DBG();
 129
 130         while (!thread_system_next());
 131 }
 132
 133 /*
 134  * Main system function
 135  */
 136 int main()
 137 {
 138         thrd_t user_thread, main_thread;
 139         Thread *th;
 140
 141         model = new ModelChecker();
 142
 143         th = new Thread(&main_thread);
 144
 145         do {
 146                 /* Start user program */
 147                 thrd_create(&user_thread, &user_main, NULL);
 148
 149                 /* Wait for all threads to complete */
 150                 thread_wait_finish();
 151
 152                 model->print_trace();
 153         } while (model->next_execution());
 154
 155         delete th;
 156         delete model;
 157
 158         DEBUG("Exiting\n");
 159         return 0;
 160 }