PintOS: schedule() Kernel Panic at ASSERT(is_thread(next))

Question

Schedule() in thread.c takes the current running thread and the next thread in the ready list, and does an ASSERT that the next thread is a thread (is_thread(t) checks that t != NULL and that t->magic == THREAD_MAGIC). I'm currently getting this error:

Kernel PANIC at ../../threads/thread.c:563 in schedule(): assertion 'is_thread(next)' failed.

I'm currently implementing timer_sleep so that it doesn't do busy waiting. Here is my timer_sleep function:

void
timer_sleep (int64_t ticks) 
{
  if (ticks > 0)
  {
    ASSERT (intr_get_level () == INTR_ON);
    enum intr_level old_level;
    old_level = intr_disable ();

    struct thread *current_thread;
    current_thread = thread_current();

    int64_t wake_tick = timer_ticks() + ticks;
    current_thread->wake_tick = wake_tick;

    list_insert_ordered (&sleep_list, &current_thread->timer_elem, cmp_wake_ticks, NULL);
    thread_block();

    intr_set_level(old_level);
  }
}

And my timer_interrupt:

static void
timer_interrupt (struct intr_frame *args UNUSED)
{
  enum intr_level old_level;
  old_level = intr_disable ();

  ticks++;
  thread_tick ();

  struct list_elem* sl_elem;
  struct thread* sl_thread;
  while(!list_empty(&sleep_list))
  {
    sl_elem = list_front(&sleep_list);
    sl_thread = list_entry(sl_elem, struct thread, timer_elem);

    if (sl_thread->wake_tick > ticks)
    {
      break;
    }

    thread_unblock(sl_thread);
    list_remove(sl_elem);
  }

  intr_set_level (old_level);
}

The only place where anything is being added to the ready_list is in thread_unblock, which also does an ASSERT is_thread, so I'm not sure where something that isn't a thread would ever be added to the ready list. I've not made any other changes to the base code other than adding the timer_elem to thread.h and the thread cmp_wake_ticks function.

Answer 1

In list_insert_ordered(), you use struct elem "timer_elem"

But see next_thread_run() function(call by is_thread())

Implement like this

list_entry (list_pop_front (&ready_list), struct thread, elem);

That means, blocked thread in ready_list use "timer_elem" but pop function use "elem"

So you unify your stuct elem to "elem"