}
	wakeup := s.wakeup
	if raceenabled {
		racerelease(unsafe.Pointer(&s.lock))
	}
	unlock(&s.lock)
	<-wakeup
	s.timer.stop()
}

// wake awakens any goroutine sleeping on the timer.
//
// Safe for concurrent use with all other methods.
func (s *wakeableSleep) wake() {
	// Grab the wakeup channel, which may be nil if we're
	// racing with close.
	lock(&s.lock)

	}
}

//go:nosplit
func semasleep(ns int64) int32 {
	var start int64
	if ns >= 0 {
		start = nanotime()
	}
	g := getg()
	mp := g.m
	if g == mp.gsignal {
		// sema sleep/wakeup are implemented with pthreads, which are not async-signal-safe on Darwin.
		throw("semasleep on Darwin signal stack")
	}
	pthread_mutex_lock(&mp.mutex)
	for {
		if mp.count > 0 {
			mp.count--

// Intended use is provide a sleep and wakeup
// primitive that can be used in the contended case
// of other synchronization primitives.
// Thus it targets the same goal as Linux's futex,
// but it has much simpler semantics.
//
// That is, don't think of these as semaphores.
// Think of them as a way to implement sleep and wakeup
// such that every sleep is paired with a single wakeup,

}

// netpollBreak interrupts a port_getn wait.
func netpollBreak() {
	// Failing to cas indicates there is an in-flight wakeup, so we're done here.
	if !netpollWakeSig.CompareAndSwap(0, 1) {
		return
	}

	// Use port_alert to put portfd into alert mode.
	// This will wake up all threads sleeping in port_getn on portfd,
	// and cause their calls to port_getn to return immediately.

	// Sleep(0) sets G's status to Gwaiting, but then immediately returns leaving the status.
	// Then the goroutine calls e.g. new and falls down into the scheduler due to pending GC.
	// After the GC nobody wakes up the goroutine from Gwaiting status.
	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(4))
	c := make(chan bool)
	go func() {
		for i := 0; i < 100; i++ {
			runtime.GC()
		}
		c <- true
	}()

// Linux futex.
//
//	futexsleep(uint32 *addr, uint32 val)
//	futexwakeup(uint32 *addr)
//
// Futexsleep atomically checks if *addr == val and if so, sleeps on addr.
// Futexwakeup wakes up threads sleeping on addr.
// Futexsleep is allowed to wake up spuriously.

const (
	_FUTEX_PRIVATE_FLAG = 128
	_FUTEX_WAIT_PRIVATE = 0 | _FUTEX_PRIVATE_FLAG
	_FUTEX_WAKE_PRIVATE = 1 | _FUTEX_PRIVATE_FLAG
)

// Atomically,
//

	ts.lock()
	ts.cleanHead()
	t.lock()
	t.trace("maybeAdd")
	when := int64(0)
	wake := false
	if t.needsAdd() {
		t.state |= timerHeaped
		when = t.when
		wakeTime := ts.wakeTime()
		wake = wakeTime == 0 || when < wakeTime
		ts.addHeap(t)
	}
	t.unlock()
	ts.unlock()
	releasem(mp)
	if wake {
		wakeNetPoller(when)
	}
}

// reset resets the time when a timer should fire.

// previous notesleep has returned, e.g. it's disallowed
// to call noteclear straight after notewakeup.
//
// notetsleep is like notesleep but wakes up after
// a given number of nanoseconds even if the event
// has not yet happened.  if a goroutine uses notetsleep to
// wake up early, it must wait to call noteclear until it
// can be sure that no other goroutine is calling
// notewakeup.
//

				t.Logf("%d: %q", samples, stack)
			}
			t.Logf("CPU profile:\n%s", stderr)
		}
	})
}

func TestTraceFutileWakeup(t *testing.T) {
	testTraceProg(t, "futile-wakeup.go", func(t *testing.T, tb, _ []byte, _ bool) {
		// Check to make sure that no goroutine in the "special" trace region
		// ends up blocking, unblocking, then immediately blocking again.
		//

			} else {
				c.recvq.dequeueSudoG(sglist)
			}
		}
		sgnext = sglist.waitlink
		sglist.waitlink = nil
		releaseSudog(sglist)
		sglist = sgnext
	}

	if cas == nil {
		throw("selectgo: bad wakeup")
	}

	c = cas.c

	if debugSelect {
		print("wait-return: cas0=", cas0, " c=", c, " cas=", cas, " send=", casi < nsends, "\n")
	}

	if casi < nsends {
		if !caseSuccess {
			goto sclose