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net/http: synchronize tests that use reqNum counters 

This suppresses the race reported in #62638.

I am not 100% certain how that race happens, but here is my theory.
The increment of reqNum happens before the server writes the response
headers, and the server necessarily writes the headers before the
client receives them. However, that write/read pair occurs through I/O
syscalls rather than Go synchronization primitives, so it doesn't
necessarily create a “happens before” relationship as defined by the
Go memory model: although we can establish a sequence of events, that
sequence is not visible to the race detector, nor to the compiler.

Fixes #62638.

Change-Id: I90d66ec3fc32b9b8e1f9bbf0bc2eb289b964b99b
Reviewed-on: https://go-review.googlesource.com/c/go/+/528475
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
This commit is contained in:
Bryan C. Mills 2023-09-14 09:03:37 -04:00 committed by Gopher Robot
parent 65c53a1833
commit 09300d89e9
1 changed files with 16 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
src/net/http/serve_test.go
View File

@ -658,10 +658,9 @@ func testServerTimeouts(t *testing.T, mode testMode) {
}
func testServerTimeoutsWithTimeout(t *testing.T, timeout time.Duration, mode testMode) error {
reqNum := 0
var reqNum atomic.Int32
ts := newClientServerTest(t, mode, HandlerFunc(func(res ResponseWriter, req *Request) {
reqNum++
fmt.Fprintf(res, "req=%d", reqNum)
fmt.Fprintf(res, "req=%d", reqNum.Add(1))
}), func(ts *httptest.Server) {
ts.Config.ReadTimeout = timeout
ts.Config.WriteTimeout = timeout
@ -861,13 +860,15 @@ func TestWriteDeadlineEnforcedPerStream(t *testing.T) {
}
func testWriteDeadlineEnforcedPerStream(t *testing.T, mode testMode, timeout time.Duration) error {
reqNum := 0
firstRequest := make(chan bool, 1)
ts := newClientServerTest(t, mode, HandlerFunc(func(res ResponseWriter, req *Request) {
reqNum++
if reqNum == 1 {
return // first request succeeds
select {
case firstRequest <- true:
// first request succeeds
default:
// second request times out
time.Sleep(timeout)
}
time.Sleep(timeout) // second request times out
}), func(ts *httptest.Server) {
ts.Config.WriteTimeout = timeout / 2
}).ts
@ -917,13 +918,15 @@ func TestNoWriteDeadline(t *testing.T) {
}
func testNoWriteDeadline(t *testing.T, mode testMode, timeout time.Duration) error {
reqNum := 0
firstRequest := make(chan bool, 1)
ts := newClientServerTest(t, mode, HandlerFunc(func(res ResponseWriter, req *Request) {
reqNum++
if reqNum == 1 {
return // first request succeeds
select {
case firstRequest <- true:
// first request succeeds
default:
// second request times out
time.Sleep(timeout)
}
time.Sleep(timeout) // second request timesout
})).ts
c := ts.Client()