Assigning Priorities for Fixed Priority Preemption Threshold Scheduling

Algorithm 1

Pseudo code for (a) TRAVERSE( ) [13] and (b) SEARCH( ) [1].

(1) TRAVERSE (Γ: set of tasks)

(2)   return  _TRAVERSE(1, Γ, Γ);

(3) _TRAVERSE (prio: priority, UnAssigned: set of tasks, Γ: set of tasks)

(4)   if (UnAssigned = ) return OPT-ASSIGN-THRESHOLD(Γ);

(5)   foreach ()

(6)     ;

(7)     if (_TRAVERSE(prio + 1, UnAssigned −  , Γ) = success) return success;

(8)    // end-foreach

(9)   return  fail;

(a) TRAVERSE( ) [13]

(1) SEARCH (Γ: set of tasks)

(2)   return _SEARCH(1, Γ, Γ);

(3) _SEARCH (prio: priority, UnAssigned: set of tasks, Γ: set of tasks)

(4)   if (UnAssigned = ) return OPT-ASSIGN-THRESHOLD(Γ);

(5)   foreach ()

      // WCRT(, prio): with () under fully preemptive fixed priority scheduling

      //       assuming all tasks in UnAssigned have the highest priority.

(6)     (, prio) −  ;

(7)     if ()

(8)     ;

(9)     return _SEARCH(prio + 1, UnAssigned −  , Γ);

(10)      // end-if

(11)   // end-foreach

(12)  SortedList ← ascendingSort(UnAssigned, );

(13)  RefinedList ← Refine(SortedList); // eliminating infeasible tasks even with the highest preemption threshold

(14)  foreach ()

(15)     ;

(16)     if (_SEARCH(prio + 1, UnAssigned −  , Γ) = success) return success;

(17)   // end-foreach

(18)  return  fail;

(b) SEARCH( ) [1]