From e5faa0d34aaaa06ebbb3bbbc81d2398d0c24b012 Mon Sep 17 00:00:00 2001
From: Ro Santalla <roberto@santalla.io>
Date: Tue, 9 Jul 2024 17:26:00 +0200
Subject: [PATCH] heartbeat: lock ForkLock for reading

Circumvents https://github.com/golang/go/issues/22315
---
 testutil/heartbeat.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/testutil/heartbeat.go b/testutil/heartbeat.go
index 706c7e0..d02a93f 100644
--- a/testutil/heartbeat.go
+++ b/testutil/heartbeat.go
@@ -7,6 +7,7 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
+	"syscall"
 	"testing"
 	"time"
 )
@@ -36,6 +37,12 @@ type Heartbeat struct {
 func NewHeartbeat(t *testing.T) Heartbeat {
 	t.Helper()
 
+	// Lock ForkLock whenever we are writing to a file that will execute shortly after, to prevent its FD from leaking
+	// into a forked process and thus making exec fail with ETXBSY.
+	// https://github.com/golang/go/issues/22315
+	syscall.ForkLock.RLock()
+	defer syscall.ForkLock.RUnlock()
+
 	dir := t.TempDir()
 	scriptFile, err := os.OpenFile(filepath.Join(dir, "heartbeat.sh"), os.O_CREATE|os.O_TRUNC|os.O_RDWR, os.FileMode(0o700))
 	if err != nil {