Ejemplo n.º 1
0
func lock(l *mutex) {
	gp := getg()

	if gp.m.locks < 0 {
		throw("runtime·lock: lock count")
	}
	gp.m.locks++

	// Speculative grab for lock.
	v := atomic.Xchg(key32(&l.key), mutex_locked)
	if v == mutex_unlocked {
		return
	}

	// wait is either MUTEX_LOCKED or MUTEX_SLEEPING
	// depending on whether there is a thread sleeping
	// on this mutex. If we ever change l->key from
	// MUTEX_SLEEPING to some other value, we must be
	// careful to change it back to MUTEX_SLEEPING before
	// returning, to ensure that the sleeping thread gets
	// its wakeup call.
	wait := v

	// On uniprocessors, no point spinning.
	// On multiprocessors, spin for ACTIVE_SPIN attempts.
	spin := 0
	if ncpu > 1 {
		spin = active_spin
	}
	for {
		// Try for lock, spinning.
		for i := 0; i < spin; i++ {
			for l.key == mutex_unlocked {
				if atomic.Cas(key32(&l.key), mutex_unlocked, wait) {
					return
				}
			}
			procyield(active_spin_cnt)
		}

		// Try for lock, rescheduling.
		for i := 0; i < passive_spin; i++ {
			for l.key == mutex_unlocked {
				if atomic.Cas(key32(&l.key), mutex_unlocked, wait) {
					return
				}
			}
			osyield()
		}

		// Sleep.
		v = atomic.Xchg(key32(&l.key), mutex_sleeping)
		if v == mutex_unlocked {
			return
		}
		wait = mutex_sleeping
		futexsleep(key32(&l.key), mutex_sleeping, -1)
	}
}
Ejemplo n.º 2
0
// Called to receive the next queued signal.
// Must only be called from a single goroutine at a time.
//go:linkname signal_recv os/signal.signal_recv
func signal_recv() uint32 {
	for {
		// Serve any signals from local copy.
		for i := uint32(0); i < _NSIG; i++ {
			if sig.recv[i/32]&(1<<(i&31)) != 0 {
				sig.recv[i/32] &^= 1 << (i & 31)
				return i
			}
		}

		// Wait for updates to be available from signal sender.
	Receive:
		for {
			switch atomic.Load(&sig.state) {
			default:
				throw("signal_recv: inconsistent state")
			case sigIdle:
				if atomic.Cas(&sig.state, sigIdle, sigReceiving) {
					notetsleepg(&sig.note, -1)
					noteclear(&sig.note)
					break Receive
				}
			case sigSending:
				if atomic.Cas(&sig.state, sigSending, sigIdle) {
					break Receive
				}
			}
		}

		// Incorporate updates from sender into local copy.
		for i := range sig.mask {
			sig.recv[i] = atomic.Xchg(&sig.mask[i], 0)
		}
	}
}
Ejemplo n.º 3
0
func notewakeup(n *note) {
	old := atomic.Xchg(key32(&n.key), 1)
	if old != 0 {
		print("notewakeup - double wakeup (", old, ")\n")
		throw("notewakeup - double wakeup")
	}
	futexwakeup(key32(&n.key), 1)
}
Ejemplo n.º 4
0
Archivo: proc.go Proyecto: kraj/gcc
// newextram allocates m's and puts them on the extra list.
// It is called with a working local m, so that it can do things
// like call schedlock and allocate.
func newextram() {
	c := atomic.Xchg(&extraMWaiters, 0)
	if c > 0 {
		for i := uint32(0); i < c; i++ {
			oneNewExtraM()
		}
	} else {
		// Make sure there is at least one extra M.
		mp := lockextra(true)
		unlockextra(mp)
		if mp == nil {
			oneNewExtraM()
		}
	}
}
Ejemplo n.º 5
0
func unlock(l *mutex) {
	v := atomic.Xchg(key32(&l.key), mutex_unlocked)
	if v == mutex_unlocked {
		throw("unlock of unlocked lock")
	}
	if v == mutex_sleeping {
		futexwakeup(key32(&l.key), 1)
	}

	gp := getg()
	gp.m.locks--
	if gp.m.locks < 0 {
		throw("runtime·unlock: lock count")
	}
	if gp.m.locks == 0 && gp.preempt { // restore the preemption request in case we've cleared it in newstack
		gp.stackguard0 = stackPreempt
	}
}