/* Up or "V" operation on a semaphore. Increments SEMA's value
and wakes up one thread of those waiting for SEMA, if any.
This function may be called from an interrupt handler.
Within an interrupt context, sema_up () always returns. */
void
sema_up (struct semaphore *sema)
{
enum intr_level old_level;
bool yield = false;
ASSERT (sema != NULL);
old_level = intr_disable ();
if (!list_empty (&sema->waiters))
{
struct thread *t = list_entry (list_pop_front (&sema->waiters),
struct thread, elem);
thread_unblock (t);
/* Yield to the newly unblocked thread if it has higher priority. */
if (t->priority > thread_current ()->priority)
yield = true;
}
sema->value++;
intr_set_level (old_level);
if (yield)
{
if (!intr_context ())
thread_yield ();
else
intr_yield_on_return ();
}
}
/* Called by the timer interrupt handler at each timer tick.
Thus, this function runs in an external interrupt context. */
void
thread_tick (void)
{
struct thread *t = thread_current ();
/* Update statistics. */
if (t == idle_thread)
idle_ticks++;
#ifdef USERPROG
else if (t->pagedir != NULL)
user_ticks++;
#endif
else
kernel_ticks++;
/* Enforce preemption. */
if (++thread_ticks >= TIME_SLICE)
intr_yield_on_return ();
}
/* Up or "V" operation on a semaphore. Increments SEMA's value
and wakes up one thread of those waiting for SEMA, if any.
This function may be called from an interrupt handler. */
void
sema_up (struct semaphore *sema)
{
enum intr_level old_level;
ASSERT (sema != NULL);
struct thread *t=NULL;
old_level = intr_disable ();
if (!list_empty (&sema->waiters)) {
struct list_elem *e=list_max(&sema->waiters, thread_max_priority,NULL);
t= list_entry(e, struct thread, elem);
list_remove(e);
thread_unblock(t);
//thread_unblock (list_entry (list_pop_front (&sema->waiters),struct thread, elem));
}
sema->value++;
intr_set_level (old_level);
if(t && t->priority>thread_current()->priority){
if(intr_context()) intr_yield_on_return();
else thread_yield();
}
}
