[PATCH] signal latency improvement

This further optimizes the 'kick wakeup' scheduler feature:

 - do not kick any CPU on UP

 - no need to mark the target task for reschedule - it's enough to send an
   interrupt to that CPU, that will initiate a signal processing pass.

kernel/sched.c

@@ -500,9 +500,12 @@ static int try_to_wake_up(task_t * p, unsigned int state, int sync, int kick)
 					resched_task(rq->curr);
 			}
 			success = 1;
-		} else
-			if (unlikely(kick) && task_running(rq, p))
-				resched_task(rq->curr);
+		}
+#if CONFIG_SMP
+	       	else
+			if (unlikely(kick) && task_running(rq, p) && (p->thread_info->cpu != smp_processor_id()))
+				smp_send_reschedule(p->thread_info->cpu);
+#endif
 		p->state = TASK_RUNNING;
 	}
 	task_rq_unlock(rq, &flags);