runtime/pprof: eliminate arbitrary deadline in testCPUProfile

The testCPUProfile helper function iterates until the profile contains
enough samples. However, in general very slow builders may need longer
to complete tests, and may have less-responsive schedulers (leading to
longer durations required to collect profiles with enough samples).
To compensate, slower builders generally run tests with longer timeouts.

Since this test helper already dynamically scales the profile duration
based on the collected samples, allow it to continue to retry and
rescale until it would exceed the test's deadline.

Fixes #52656 (hopefully).

Change-Id: I4561e721927503f33a6d23336efa979bb9d3221f
Reviewed-on: https://go-review.googlesource.com/c/go/+/406614
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
Run-TryBot: Bryan Mills <[email protected]>
Auto-Submit: Bryan Mills <[email protected]>

Author: Bryan C. Mills

src/runtime/pprof/pprof_test.go

@@ -437,10 +437,14 @@ func testCPUProfile(t *testing.T, matches profileMatchFunc, f func(dur time.Dura
 
 	broken := cpuProfilingBroken()
 
-	maxDuration := 5 * time.Second
-	if testing.Short() && broken {
-		// If it's expected to be broken, no point waiting around.
-		maxDuration /= 10
+	deadline, ok := t.Deadline()
+	if broken || !ok {
+		if broken && testing.Short() {
+			// If it's expected to be broken, no point waiting around.
+			deadline = time.Now().Add(1 * time.Second)
+		} else {
+			deadline = time.Now().Add(10 * time.Second)
+		}
 	}
 
 	// If we're running a long test, start with a long duration
@@ -455,7 +459,7 @@ func testCPUProfile(t *testing.T, matches profileMatchFunc, f func(dur time.Dura
 	// several others under go test std. If a test fails in a way
 	// that could mean it just didn't run long enough, try with a
 	// longer duration.
-	for duration <= maxDuration {
+	for {
 		var prof bytes.Buffer
 		if err := StartCPUProfile(&prof); err != nil {
 			t.Fatal(err)
@@ -468,9 +472,10 @@ func testCPUProfile(t *testing.T, matches profileMatchFunc, f func(dur time.Dura
 		}
 
 		duration *= 2
-		if duration <= maxDuration {
-			t.Logf("retrying with %s duration", duration)
+		if time.Until(deadline) < duration {
+			break
 		}
+		t.Logf("retrying with %s duration", duration)
 	}
 
 	if broken {