runtime: deflake TestGoroutineProfileTrivial

Failed at https://storage.googleapis.com/go-build-log/9875de36/nacl-amd64p32_931ba6cf.log

Change-Id: I2bc204ed58da543ee2534b69c29c8e8485d54683
Reviewed-on: https://go-review.googlesource.com/19155
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/runtime/runtime_test.go b/src/runtime/runtime_test.go
index 581f52bcb085a50120d668701e7963684e315533..a6150a77ee9502b99b9673af7d7d86272d75024e 100644 (file)
--- a/src/runtime/runtime_test.go
+++ b/src/runtime/runtime_test.go
@@ -310,13 +310,22 @@ func TestAppendSliceGrowth(t *testing.T) {
 }
 
 func TestGoroutineProfileTrivial(t *testing.T) {
-       n1, ok := GoroutineProfile(nil) // should fail, there's at least 1 goroutine
-       if n1 < 1 || ok {
-               t.Fatalf("GoroutineProfile(nil) = %d, %v, want >0, false", n1, ok)
-       }
-
-       n2, ok := GoroutineProfile(make([]StackRecord, n1))
-       if n2 != n1 || !ok {
-               t.Fatalf("GoroutineProfile(%d) = %d, %v, want %d, true", n1, n2, ok, n1)
+       // Calling GoroutineProfile twice in a row should find the same number of goroutines,
+       // but it's possible there are goroutines just about to exit, so we might end up
+       // with fewer in the second call. Try a few times; it should converge once those
+       // zombies are gone.
+       for i := 0; ; i++ {
+               n1, ok := GoroutineProfile(nil) // should fail, there's at least 1 goroutine
+               if n1 < 1 || ok {
+                       t.Fatalf("GoroutineProfile(nil) = %d, %v, want >0, false", n1, ok)
+               }
+               n2, ok := GoroutineProfile(make([]StackRecord, n1))
+               if n2 == n1 && ok {
+                       break
+               }
+               t.Logf("GoroutineProfile(%d) = %d, %v, want %d, true", n1, n2, ok, n1)
+               if i >= 10 {
+                       t.Fatalf("GoroutineProfile not converging")
+               }
        }
 }