MIT6.s081: lab7thread

struct thread {

  char       stack[STACK_SIZE]; /* the thread's stack */

  int        state;             /* FREE, RUNNING, RUNNABLE */

  char       context[4096]; //for context save. 这里的 context 实际上是 char * 类型，也就是 4096 字节的地址空间。

};

void 

thread_create(void (*func)())

{

  struct thread *t;

  for (t = all_thread; t < all_thread + MAX_THREAD; t++) {

    if (t->state == FREE) break;

  }

  t->state = RUNNABLE;

  // YOUR CODE HERE

  *(uint64*)(t->context) = (uint64)func; // 这个就是使用 func

  *(uint64*)(t->context + 8) = (uint64)(t->stack+STACK_SIZE);

}

void 

thread_schedule(void)

{

  struct thread *t, *next_thread;

  /* Find another runnable thread. */

  next_thread = 0;

  t = current_thread + 1;

  for(int i = 0; i < MAX_THREAD; i++){

    if(t >= all_thread + MAX_THREAD)

      t = all_thread;

    if(t->state == RUNNABLE) {

      next_thread = t;

      break;

    }

    t = t + 1;

  }

  if (next_thread == 0) {

    printf("thread_schedule: no runnable threads\n");

    exit(-1);

  }

  if (current_thread != next_thread) {         /* switch threads?  */

    next_thread->state = RUNNING;

    t = current_thread;

    current_thread = next_thread;

    thread_switch((uint64)t->context, (uint64)current_thread->context);    

    /* YOUR CODE HERE

     * Invoke thread_switch to switch from t to next_thread:

     * thread_switch(??, ??);

     */

  } else

    next_thread = 0;

}