Kernel: Fix timer deadline issues in scheduler

Don't wake up threads when getting the next timer deadline.
If we are idling this can: remove thread from block list, get the
deadline for the next blocked thread, return to idle thread. This will
end up sleeping until the next wake up condition which in the worst
case would be rebalance, or indefinitely when not running SMP.

Make sure we always set the next timer deadline. I was not doing that if
the timer interrupt did not lead to a yield

kernel/kernel/Scheduler.cpp

@@ -326,8 +326,6 @@ namespace Kernel
 		if (!interrupt_controller.is_using_apic())
 			return;
 
-		wake_up_sleeping_threads();
-
 		uint64_t deadline_ns = m_next_reschedule_ns;
 		if (!m_block_queue.empty())
 			deadline_ns = BAN::Math::min(deadline_ns, m_block_queue.front()->wake_time_ns);
@@ -368,8 +366,12 @@ namespace Kernel
 
 		wake_up_sleeping_threads();
 
+		// NOTE: yield will update the timer deadline, but if we do not yield make sure
+		//       we set the next deadline or we won't get another timer interrupt
 		if (is_idle() || SystemTimer::get().ns_since_boot() >= m_next_reschedule_ns)
 			Processor::yield();
+		else
+			update_wake_up_deadline();
 	}
 
 	void Scheduler::unblock_thread(SchedulerQueue::Node* node)