Merge pull request #22 from danielnelson/fix-data-race

Fix data race between timer Reset and Add; unlock before gosched

Author: benbjohnson

clock.go

@@ -272,8 +272,8 @@ func (t *Timer) Reset(d time.Duration) bool {
 		return t.timer.Reset(d)
 	}
 
-	t.next = t.mock.now.Add(d)
 	t.mock.mu.Lock()
+	t.next = t.mock.now.Add(d)
 	defer t.mock.mu.Unlock()
 
 	registered := !t.stopped
@@ -296,9 +296,8 @@ func (t *internalTimer) Tick(now time.Time) {
 	}
 	t.mock.removeClockTimer((*internalTimer)(t))
 	t.mock.mu.Lock()
-	defer t.mock.mu.Unlock()
-
 	t.stopped = true
+	t.mock.mu.Unlock()
 	gosched()
 }
 

clock_test.go

@@ -211,6 +211,30 @@ func TestClock_Timer_Reset(t *testing.T) {
 	}
 }
 
+// Ensure reset can be called immediately after reading channel
+func TestClock_Timer_Reset_Unlock(t *testing.T) {
+	clock := NewMock()
+	timer := clock.Timer(1 * time.Second)
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+
+		select {
+		case <-timer.C:
+			timer.Reset(1 * time.Second)
+		}
+
+		select {
+		case <-timer.C:
+		}
+	}()
+
+	clock.Add(2 * time.Second)
+	wg.Wait()
+}
+
 // Ensure that the mock's After channel sends at the correct time.
 func TestMock_After(t *testing.T) {
 	var ok int32