// Start tracing.
	if err := trace.Start(os.Stdout); err != nil {
		log.Fatalf("failed to start tracing: %v", err)
	}
	// Run GOMAXPROCS a bunch of times, up and down.
	for i := 1; i <= 16; i *= 2 {
		runtime.GOMAXPROCS(i)
		time.Sleep(1 * time.Millisecond)
	}
	for i := 16; i >= 1; i /= 2 {
		runtime.GOMAXPROCS(i)
		time.Sleep(1 * time.Millisecond)
	}
	// Stop tracing.
	trace.Stop()

apiVersion: release-notes/v2
kind: feature
area: installation
releaseNotes:
- |

[GOOS:aix] env CGO_ENABLED=0  # go.dev/issue/56896
env GOMAXPROCS=16
go build -a -o http16.o net/http
env GOMAXPROCS=17
go build -a -o http17.o net/http
cmp -q http16.o http17.o
env GOMAXPROCS=18
go build -a -o http18.o net/http
cmp -q http16.o http18.o

# Check that goroutine scheduling does not affect linker output.
env GOMAXPROCS=16
go build -a -o gofmt16.exe cmd/gofmt
env GOMAXPROCS=17
go build -a -o gofmt17.exe cmd/gofmt

			panic(fmt.Sprintf("wlock(%d)\n", n))
		}
		for i := 0; i < 100; i++ {
		}
		atomic.AddInt32(activity, -10000)
		rwm.Unlock()
	}
	cdone <- true
}

func HammerRWMutex(gomaxprocs, numReaders, num_iterations int) {
	GOMAXPROCS(gomaxprocs)
	// Number of active readers + 10000 * number of active writers.
	var activity int32
	var rwm RWMutex
	rwm.Init()
	cdone := make(chan bool)

	m.RLock()
	clocked <- true
	<-cunlock
	m.RUnlock()
	cdone <- true
}

func doTestParallelReaders(numReaders, gomaxprocs int) {
	runtime.GOMAXPROCS(gomaxprocs)
	var m RWMutex
	clocked := make(chan bool)
	cunlock := make(chan bool)
	cdone := make(chan bool)
	for i := 0; i < numReaders; i++ {
		go parallelReader(&m, clocked, cunlock, cdone)
	}

	}
}

func TestSemaHandoff1(t *testing.T) {
	if GOMAXPROCS(-1) <= 1 {
		t.Skip("GOMAXPROCS <= 1")
	}
	defer GOMAXPROCS(GOMAXPROCS(-1))
	GOMAXPROCS(1)
	TestSemaHandoff(t)
}

func TestSemaHandoff2(t *testing.T) {
	if GOMAXPROCS(-1) <= 2 {
		t.Skip("GOMAXPROCS <= 2")
	}
	defer GOMAXPROCS(GOMAXPROCS(-1))
	GOMAXPROCS(2)
	TestSemaHandoff(t)
}

func testSemaHandoff() bool {

		t.Skip("skipping during short test")
	}
	maxprocs := runtime.GOMAXPROCS(3)
	compl := make(chan bool, 2)
	go func() {
		for i := 0; i != 1000; i += 1 {
			runtime.GC()
		}
		compl <- true
	}()
	go func() {
		for i := 0; i != 1000; i += 1 {
			runtime.GOMAXPROCS(3)
		}
		compl <- true
	}()
	go perpetuumMobile()
	<-compl
	<-compl
	stop <- true
	runtime.GOMAXPROCS(maxprocs)
}

	register("LockOSThreadAlt", LockOSThreadAlt)
}

func LockOSThreadMain() {
	// This requires GOMAXPROCS=1 from the beginning to reliably
	// start a goroutine on the main thread.
	if runtime.GOMAXPROCS(-1) != 1 {
		println("requires GOMAXPROCS=1")
		os.Exit(1)
	}

	ready := make(chan bool, 1)
	go func() {
		// Because GOMAXPROCS=1, this *should* be on the main
		// thread. Stay there.
		runtime.LockOSThread()

	// checks that the runtime doesn't do anything terrible.

	// This requires GOMAXPROCS=1 from the beginning to reliably
	// start a goroutine on the main thread.
	if runtime.GOMAXPROCS(-1) != 1 {
		println("requires GOMAXPROCS=1")
		os.Exit(1)
	}

	ready := make(chan bool, 1)
	go func() {
		// Because GOMAXPROCS=1, this *should* be on the main
		// thread. Stay there.
		runtime.LockOSThread()

// a warm-up. The average number of allocations over the specified number of
// runs will then be measured and returned.
//
// AllocsPerRun sets GOMAXPROCS to 1 during its measurement and will restore
// it before returning.
func AllocsPerRun(runs int, f func()) (avg float64) {
	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(1))

	// Warm up the function
	f()

	// Measure the starting statistics
	var memstats runtime.MemStats