//
// All init functions are run on the startup thread. Calling LockOSThread
// from an init function will cause the main function to be invoked on
// that thread.
//
// A goroutine should call LockOSThread before calling OS services or
// non-Go library functions that depend on per-thread state.
//
//go:nosplit
func LockOSThread() {
	if atomic.Load(&newmHandoff.haveTemplateThread) == 0 && GOOS != "plan9" {

		err   error
	}
	ch := make(chan result) // unbuffered
	go func() {
		if err := acquireThread(ctx); err != nil {
			ch <- result{err: mapErr(err)}
			return
		}
		defer releaseThread()
		runtime.LockOSThread()
		defer runtime.UnlockOSThread()
		proto, err := getprotobyname(name)
		select {
		case ch <- result{proto: proto, err: err}:
		case <-ctx.Done():
		}
	}()
	select {
	case r := <-ch:

	}
}

func TestCallbackGC(t *testing.T) {
	nestedCall(t, runtime.GC)
}

func TestCallbackPanicLocked(t *testing.T) {
	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	if !runtime.LockedOSThread() {
		t.Fatal("runtime.LockOSThread didn't")
	}
	defer func() {
		s := recover()
		if s == nil {
			t.Fatal("did not panic")
		}
		if s.(string) != "callback panic" {

func startProcess(argv0 string, argv []string, attr *ProcAttr) (pid int, err error) {
	type forkRet struct {
		pid int
		err error
	}

	forkc := make(chan forkRet, 1)
	go func() {
		runtime.LockOSThread()
		var ret forkRet

		ret.pid, ret.err = forkExec(argv0, argv, attr)
		// If fork fails there is nothing to wait for.
		if ret.err != nil || ret.pid == 0 {
			forkc <- ret
			return
		}

	Size        int // Size.
}

type SysProcAttr struct {
	Chroot     string      // Chroot.
	Credential *Credential // Credential.
	// Ptrace tells the child to call ptrace(PTRACE_TRACEME).
	// Call runtime.LockOSThread before starting a process with this set,
	// and don't call UnlockOSThread until done with PtraceSyscall calls.
	Ptrace bool
	Setsid bool // Create session.
	// Setpgid sets the process group ID of the child to Pgid,

	lockedg       guintptr
	createstack   [32]uintptr // stack that created this thread, it's used for StackRecord.Stack0, so it must align with it.
	lockedExt     uint32      // tracking for external LockOSThread
	lockedInt     uint32      // tracking for internal lockOSThread
	nextwaitm     muintptr    // next m waiting for lock

	mLockProfile mLockProfile // fields relating to runtime.lock contention

			if i%2 == 1 {
				// On Plan 9, after calling LockOSThread, the goroutines
				// run on different processes which don't share the working
				// directory. This used to be an issue because Go expects
				// the working directory to be program-wide.
				// See issue 9428.
				runtime.LockOSThread()
			}
			select {
			case <-done:
				return
			case <-hold:
			}

	disableSigChan = make(chan uint32)
	enableSigChan = make(chan uint32)
	go func() {
		// Signal masks are per-thread, so make sure this goroutine stays on one
		// thread.
		LockOSThread()
		defer UnlockOSThread()
		// The sigBlocked mask contains the signals not active for os/signal,
		// initially all signals except the essential. When signal.Notify()/Stop is called,

			},
		)
	} else {
		t.Log(`skipping "use_mklink_cmd" test, mklink does not supports directory symbolic links`)
	}

	// The rest of these test requires SeCreateSymbolicLinkPrivilege to be held.
	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	err := windows.ImpersonateSelf(windows.SecurityImpersonation)
	if err != nil {
		t.Fatal(err)
	}
	defer windows.RevertToSelf()

	// will become invalid after a thread switch. This test
	// checks that the bad caching doesn't happen.

	ch := make(chan int)
	go func(ch chan int) {
		ch <- 5
		LockOSThread()
	}(ch)

	g1 := getg()

	// Block on a receive. This is likely to get us a thread
	// switch. If we yield to the sender goroutine, it will
	// lock the thread, forcing us to resume on a different