runtime/testdata/testprog: increase GCFairness2 timeout to 1s

OpenBSD's scheduler causes preemption to take 20+ms, so 30ms is not
enough time for 3 goroutines to run. This change continues to sleep for
30ms, but if it finds that the 3 goroutines have not run, it sleeps for
an additional 1s before declaring failure.

Updates #17712

Change-Id: I3e886e40d05192b7cb71b4f242af195836ef62a8
Reviewed-on: https://go-review.googlesource.com/32634Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Quentin Smith <quentin@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/testdata/testprog/gc.go

@@ -98,12 +98,26 @@ func GCFairness2() {
 	// If the scheduling rules change, this may not be enough time
 	// to let all goroutines run, but for now we cycle through
 	// them rapidly.
+	//
+	// OpenBSD's scheduler makes every usleep() take at least
+	// 20ms, so we need a long time to ensure all goroutines have
+	// run. If they haven't run after 30ms, give it another 1000ms
+	// and check again.
 	time.Sleep(30 * time.Millisecond)
+	var fail bool
+	for i := range count {
+		if atomic.LoadInt64(&count[i]) == 0 {
+			fail = true
+		}
+	}
+	if fail {
+		time.Sleep(1 * time.Second)
 		for i := range count {
 			if atomic.LoadInt64(&count[i]) == 0 {
 				fmt.Printf("goroutine %d did not run\n", i)
 				return
 			}
 		}
+	}
 	fmt.Println("OK")
 }