runtime: map iterators: always use intrabucket randomess

Fixes #8688

LGTM=rsc
R=golang-codereviews, bradfitz, rsc, khr
CC=golang-codereviews
https://golang.org/cl/135660043

1 files changed, 23 insertions, 20 deletions

diff --git a/src/runtime/map_test.go b/src/runtime/map_test.go
index 2e87a94a03..e2f1481ad5 100644
--- a/src/runtime/map_test.go
+++ b/src/runtime/map_test.go
@@ -412,30 +412,33 @@ func TestMapNanGrowIterator(t *testing.T) {
 
 func TestMapIterOrder(t *testing.T) {
 	for _, n := range [...]int{3, 7, 9, 15} {
-		// Make m be {0: true, 1: true, ..., n-1: true}.
-		m := make(map[int]bool)
-		for i := 0; i < n; i++ {
-			m[i] = true
-		}
-		// Check that iterating over the map produces at least two different orderings.
-		ord := func() []int {
-			var s []int
-			for key := range m {
-				s = append(s, key)
+		for i := 0; i < 1000; i++ {
+			// Make m be {0: true, 1: true, ..., n-1: true}.
+			m := make(map[int]bool)
+			for i := 0; i < n; i++ {
+				m[i] = true
 			}
-			return s
-		}
-		first := ord()
-		ok := false
-		for try := 0; try < 100; try++ {
-			if !reflect.DeepEqual(first, ord()) {
-				ok = true
+			// Check that iterating over the map produces at least two different orderings.
+			ord := func() []int {
+				var s []int
+				for key := range m {
+					s = append(s, key)
+				}
+				return s
+			}
+			first := ord()
+			ok := false
+			for try := 0; try < 100; try++ {
+				if !reflect.DeepEqual(first, ord()) {
+					ok = true
+					break
+				}
+			}
+			if !ok {
+				t.Errorf("Map with n=%d elements had consistent iteration order: %v", n, first)
 				break
 			}
 		}
-		if !ok {
-			t.Errorf("Map with n=%d elements had consistent iteration order: %v", n, first)
-		}
 	}
 }