net/http: fix scheduling race resulting in flaky test

The test was measuring something, assuming other goroutines had
already scheduled.

Fixes #10427

Change-Id: I2a4d3906f9d4b5ea44b57d972e303bbe2b0b1cde
Reviewed-on: https://go-review.googlesource.com/9561
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/src/net/http/export_test.go b/src/net/http/export_test.go
index b656aa9731..0457be50da 100644
--- a/src/net/http/export_test.go
+++ b/src/net/http/export_test.go
@@ -10,9 +10,17 @@ package http
 import (
 	"net"
 	"net/url"
+	"sync"
 	"time"
 )
 
+func init() {
+	// We only want to pay for this cost during testing.
+	// When not under test, these values are always nil
+	// and never assigned to.
+	testHookMu = new(sync.Mutex)
+}
+
 func NewLoggingConn(baseName string, c net.Conn) net.Conn {
 	return newLoggingConn(baseName, c)
 }
@@ -86,6 +94,12 @@ func SetEnterRoundTripHook(f func()) {
 	testHookEnterRoundTrip = f
 }
 
+func SetReadLoopBeforeNextReadHook(f func()) {
+	testHookMu.Lock()
+	defer testHookMu.Unlock()
+	testHookReadLoopBeforeNextRead = f
+}
+
 func NewTestTimeoutHandler(handler Handler, ch <-chan time.Time) Handler {
 	f := func() <-chan time.Time {
 		return ch