container/init: call lockOSThread through dispatcher

This degrades test performance if not stubbed out.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/dispatcher.go

@@ -8,6 +8,7 @@ import (
 	"os/exec"
 	"os/signal"
 	"path/filepath"
+	"runtime"
 	"syscall"
 
 	"hakurei.app/container/seccomp"
@@ -21,6 +22,9 @@ type osFile interface {
 
 // syscallDispatcher provides methods that make state-dependent system calls as part of their behaviour.
 type syscallDispatcher interface {
+	// lockOSThread provides [runtime.LockOSThread].
+	lockOSThread()
+
 	// setPtracer provides [SetPtracer].
 	setPtracer(pid uintptr) error
 	// setDumpable provides [SetDumpable].
@@ -136,6 +140,8 @@ type syscallDispatcher interface {
 // direct implements syscallDispatcher on the current kernel.
 type direct struct{}
 
+func (direct) lockOSThread() { runtime.LockOSThread() }
+
 func (direct) setPtracer(pid uintptr) error       { return SetPtracer(pid) }
 func (direct) setDumpable(dumpable uintptr) error { return SetDumpable(dumpable) }
 func (direct) setNoNewPrivs() error               { return SetNoNewPrivs() }

container/dispatcher_test.go

@@ -315,6 +315,8 @@ func checkArgReflect(k *kstub, arg string, got any, n int) bool {
 	return true
 }
 
+func (k *kstub) lockOSThread() { k.expect("lockOSThread") }
+
 func (k *kstub) setPtracer(pid uintptr) error {
 	return k.expect("setPtracer").error(
 		checkArg(k, "pid", pid, 0))

container/init.go

@@ -6,7 +6,6 @@ import (
 	"os"
 	"os/exec"
 	"path"
-	"runtime"
 	"slices"
 	"strconv"
 	. "syscall"
@@ -81,11 +80,11 @@ type initParams struct {
 }
 
 func Init(prepareLogger func(prefix string), setVerbose func(verbose bool)) {
-	initEntrypoint(prepareLogger, setVerbose, direct{})
+	initEntrypoint(direct{}, prepareLogger, setVerbose)
 }
 
-func initEntrypoint(prepareLogger func(prefix string), setVerbose func(verbose bool), k syscallDispatcher) {
-	runtime.LockOSThread()
+func initEntrypoint(k syscallDispatcher, prepareLogger func(prefix string), setVerbose func(verbose bool)) {
+	k.lockOSThread()
 	prepareLogger("init")
 
 	if k.getpid() != 1 {