Fix microtask signaling and improve tests

modules/microtasks.go

@@ -260,6 +260,14 @@ func microTaskScheduler() {
 		return
 	}
 
+	// Debugging: Print current amount of microtasks.
+	// go func() {
+	// 	for {
+	// 		time.Sleep(1 * time.Second)
+	// 		log.Debugf("modules: microtasks: %d", atomic.LoadInt32(microTasks))
+	// 	}
+	// }()
+
 	for {
 		if shutdownFlag.IsSet() {
 			go microTaskShutdownScheduler()
@@ -338,6 +346,7 @@ func getMediumPriorityClearance(maxDelay time.Duration) {
 		case <-time.After(maxDelay):
 			// Start without clearance and increase microtask counter.
 			atomic.AddInt32(microTasks, 1)
+			return
 		}
 	}
 	// Wait for signal to start.
@@ -347,9 +356,9 @@ func getMediumPriorityClearance(maxDelay time.Duration) {
 		select {
 		case <-signal:
 		case <-time.After(maxDelay):
-			// TODO: Creating the timer two times could lead to 2x max delay.
-			// Start without clearance and increase microtask counter.
-			atomic.AddInt32(microTasks, 1)
+			// Don't keep waiting for signal forever.
+			// Don't increase microtask counter, as the signal was already submitted
+			// and the counter will be increased by the scheduler.
 		}
 	}
 }
@@ -365,6 +374,7 @@ func getLowPriorityClearance(maxDelay time.Duration) {
 		case <-time.After(maxDelay):
 			// Start without clearance and increase microtask counter.
 			atomic.AddInt32(microTasks, 1)
+			return
 		}
 	}
 	// Wait for signal to start.
@@ -374,9 +384,9 @@ func getLowPriorityClearance(maxDelay time.Duration) {
 		select {
 		case <-signal:
 		case <-time.After(maxDelay):
-			// TODO: Creating the timer two times could lead to 2x max delay.
-			// Start without clearance and increase microtask counter.
-			atomic.AddInt32(microTasks, 1)
+			// Don't keep waiting for signal forever.
+			// Don't increase microtask counter, as the signal was already submitted
+			// and the counter will be increased by the scheduler.
 		}
 	}
 }

modules/microtasks_test.go

@@ -21,6 +21,11 @@ func init() {
 
 func TestMicroTaskWaiting(t *testing.T) { //nolint:paralleltest // Too much interference expected.
 
+	// Check if the state is clean.
+	if atomic.LoadInt32(microTasks) != 0 {
+		t.Fatalf("cannot start test with dirty state: %d microtasks", atomic.LoadInt32(microTasks))
+	}
+
 	// skip
 	if testing.Short() {
 		t.Skip("skipping test in short mode, as it is not fully deterministic")
@@ -108,6 +113,12 @@ func TestMicroTaskWaiting(t *testing.T) { //nolint:paralleltest // Too much inte
 	if completeOutput != mtwExpectedOutput {
 		t.Errorf("MicroTask waiting test failed, expected sequence %s, got %s", mtwExpectedOutput, completeOutput)
 	}
+
+	// Check if the state is clean.
+	time.Sleep(10 * time.Millisecond)
+	if atomic.LoadInt32(microTasks) != 0 {
+		t.Fatalf("test ends with dirty state: %d microtasks", atomic.LoadInt32(microTasks))
+	}
 }
 
 // Test Microtask ordering.
@@ -189,6 +200,12 @@ func lowPrioSignalledTaskTester() {
 }
 
 func TestMicroTaskOrdering(t *testing.T) { //nolint:paralleltest // Too much interference expected.
+
+	// Check if the state is clean.
+	if atomic.LoadInt32(microTasks) != 0 {
+		t.Fatalf("cannot start test with dirty state: %d microtasks", atomic.LoadInt32(microTasks))
+	}
+
 	// skip
 	if testing.Short() {
 		t.Skip("skipping test in short mode, as it is not fully deterministic")
@@ -243,4 +260,10 @@ func TestMicroTaskOrdering(t *testing.T) { //nolint:paralleltest // Too much int
 		!strings.Contains(completeOutput, "22222") {
 		t.Errorf("MicroTask ordering test failed, output was %s. This happens occasionally, please run the test multiple times to verify", completeOutput)
 	}
+
+	// Check if the state is clean.
+	time.Sleep(10 * time.Millisecond)
+	if atomic.LoadInt32(microTasks) != 0 {
+		t.Fatalf("test ends with dirty state: %d microtasks", atomic.LoadInt32(microTasks))
+	}
 }

modules/start.go

@@ -36,8 +36,8 @@ func Start() error {
 	defer mgmtLock.Unlock()
 
 	// start microtask scheduler
-	go microTaskScheduler()
 	SetMaxConcurrentMicroTasks(runtime.GOMAXPROCS(0))
+	go microTaskScheduler()
 
 	// inter-link modules
 	err := initDependencies()