diff --git a/miosix/kernel/scheduler/control/control_scheduler.cpp b/miosix/kernel/scheduler/control/control_scheduler.cpp
index a774893f404c3581610776ea79e700de2d9f047d..8952dc4f7100d4891a5c5c2d29e735cadc982371 100644
--- a/miosix/kernel/scheduler/control/control_scheduler.cpp
+++ b/miosix/kernel/scheduler/control/control_scheduler.cpp
@@ -200,7 +200,8 @@ long long ControlScheduler::IRQgetNextPreemption()
 // Should be called when the current thread is the idle thread
 static inline void IRQsetNextPreemptionForIdle(){
     if (sleepingList->empty())
-        //normally should happen unless an IRQ is set!
+        //normally should not happen unless an IRQ is already set and able to
+        //preempt idle thread
         nextPreemption = numeric_limits<long long>::max(); 
     else
         nextPreemption = sleepingList->front()->wakeup_time;
diff --git a/miosix/kernel/scheduler/control/control_scheduler_types.h b/miosix/kernel/scheduler/control/control_scheduler_types.h
index 3b4231563a9c8741f3e7922ef0d678fe9280b30e..bcf35f9975c0a945cbdccc154319461ad2b9dd16 100755
--- a/miosix/kernel/scheduler/control/control_scheduler_types.h
+++ b/miosix/kernel/scheduler/control/control_scheduler_types.h
@@ -125,13 +125,15 @@ private:
 
 inline bool operator <(ControlSchedulerPriority a, ControlSchedulerPriority b)
 {
-    return (b.getRealtime() == 1 && a.getRealtime() != 1) ||
-            (a.getRealtime() != 1 && b.getRealtime() != 1 && a.get() < b.get());
+    //rule 1) Idle thread should be always preempted by any thread!
+    //rule 2) Only REALTIME_PRIORITY_IMMEDIATE threads can preempt other threads
+    //right away, for other real-time priorities, the scheduler does not
+    //require to be called before the end of the current burst!
+    return a.get()==-1 || (a.getRealtime() != 1 && b.getRealtime() == 1);
 }
 
 inline bool operator>(ControlSchedulerPriority a, ControlSchedulerPriority b){
-    return (a.getRealtime() == 1 && b.getRealtime() != 1) ||
-            (a.getRealtime() != 1 && b.getRealtime() != 1 && a.get() > b.get());
+    return b.get()==-1 || (a.getRealtime() == 1 && b.getRealtime() != 1);
 }
 
 inline bool operator ==(ControlSchedulerPriority a, ControlSchedulerPriority b)