testing/race: fixing intermittent test failure

dfava · Bryan C. Mills · commit aaed6cbced23 · 2021-02-23T22:14:38.000Z
Test NoRaceMutexPureHappensBefore in runtime/race/testdata/mutex_test.go expects the second spawned goroutine to run after the first. The test attempts to force this scheduling with a 10 millisecond wait. Following a suggestion by Bryan Mills, we force this scheduling using a shared variable whose access take place within the existing mutex. Fixes golang#35745. Change-Id: Ib23ec51492ecfeed4752e020401dd25755a669ed Reviewed-on: https://go-review.googlesource.com/c/go/+/291292 Reviewed-by: Bryan C. Mills <bcmills@google.com> Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Trust: Bryan C. Mills <bcmills@google.com> Run-TryBot: Bryan C. Mills <bcmills@google.com> TryBot-Result: Go Bot <gobot@golang.org>
diff --git a/src/runtime/race/testdata/mutex_test.go b/src/runtime/race/testdata/mutex_test.go
@@ -78,16 +78,23 @@ func TestNoRaceMutexPureHappensBefore(t *testing.T) {
 	var mu sync.Mutex
 	var x int16 = 0
 	_ = x
+	written := false
 	ch := make(chan bool, 2)
 	go func() {
 		x = 1
 		mu.Lock()
+		written = true
 		mu.Unlock()
 		ch <- true
 	}()
 	go func() {
-		<-time.After(1e5)
+		time.Sleep(100 * time.Microsecond)
 		mu.Lock()
+		for !written {
+			mu.Unlock()
+			time.Sleep(100 * time.Microsecond)
+			mu.Lock()
+		}
 		mu.Unlock()
 		x = 1
 		ch <- true
