Fix broken demand calculation

Felipe Cerqueira reported incorrect QPA results. The root cause was
a corner case in the demand calculation. This patch fixes the
underestimation of demand if time == deadline and adds a test case
discovered by Felipe that triggered the bug.

2 files changed, 17 insertions, 1 deletions

diff --git a/native/include/tasks.h b/native/include/tasks.h
index 092e21a..0f53060 100644
--- a/native/include/tasks.h
+++ b/native/include/tasks.h
@@ -69,7 +69,7 @@ class Task
 
     void bound_demand(const integral_t &time, integral_t &demand) const
     {
-        if (time <= deadline)
+        if (time < deadline)
             demand = 0;
         else
         {
diff --git a/tests/edf.py b/tests/edf.py
index ee388ee..3dffb6d 100644
--- a/tests/edf.py
+++ b/tests/edf.py
@@ -171,3 +171,19 @@ class Test_QPA(unittest.TestCase):
     def test_edf_schedulable(self):
         self.ts.append(tasks.SporadicTask(   10,    100, deadline=15))
         self.assertFalse(edf.is_schedulable(1, self.ts))
+
+    def test_qpa_known_unschedulable(self):
+        qpa = edf.native.QPATest(1)
+        ts1 = tasks.TaskSystem([
+            tasks.SporadicTask(331, 15000, deadline=2688),
+            tasks.SporadicTask(3654, 77000, deadline=3849)
+            ])
+        self.assertFalse(qpa.is_schedulable(sched.get_native_taskset(ts1)))
+
+        ts2 =  tasks.TaskSystem([tasks.SporadicTask(331, 15000, deadline=2688),
+            tasks.SporadicTask(413, 34000, deadline=1061),
+            tasks.SporadicTask(3654, 77000, deadline=3849),
+            tasks.SporadicTask(349, 70000, deadline=20189),
+            tasks.SporadicTask(1113, 83000, deadline=10683),
+            ])
+        self.assertFalse(qpa.is_schedulable(sched.get_native_taskset(ts2)))