t.Fatalf("unexpected error: %v", err)
	}
	if err := ps.Subscribe(MaskAll, ch2, doneCh, nil); err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	ps.Lock()
	defer ps.Unlock()

	if len(ps.subs) != 2 || ps.NumSubscribers(MaskAll) != 2 || ps.Subscribers() != 2 {
		t.Fatalf("expected 2 subscribers")
	}
}

func TestNumSubscribersMask(t *testing.T) {
	ps := New[Maskable, Mask](2)

func (l *Init) Do(f func() error) error {
	if atomic.LoadUint32(&l.done) == 0 {
		return l.do(f)
	}
	return nil
}

func (l *Init) do(f func() error) error {
	l.m.Lock()
	defer l.m.Unlock()
	if atomic.LoadUint32(&l.done) == 0 {
		if err := f(); err != nil {
			return err
		}
		// Mark as done only when f() is successful
		atomic.StoreUint32(&l.done, 1)
	}
	return nil
}

func (c *connMgr) addConn(conn *ZtunnelConnection) {
	log.Debug("ztunnel connected")
	c.mu.Lock()
	defer c.mu.Unlock()
	c.connectionSet[conn] = struct{}{}
	c.latestConn = conn
	ztunnelConnected.RecordInt(int64(len(c.connectionSet)))
}

func (c *connMgr) LatestConn() *ZtunnelConnection {
	c.mu.Lock()
	defer c.mu.Unlock()
	return c.latestConn
}

func (c *connMgr) deleteConn(conn *ZtunnelConnection) {

		if t.updating.TryLock() {
			go func() {
				defer t.updating.Unlock()
				t.update(context.Background())
			}()
		}
		return *v, nil
	}

	// Get lock. Either we get it or we wait for it.
	t.updating.Lock()
	defer t.updating.Unlock()

	if time.Since(time.UnixMilli(t.lastUpdateMs.Load())) < ttl {
		// There is a new value, release lock and return it.

	xl.getDisks = func() []StorageAPI {
		for i := range erasureDisks[:6] {
			erasureDisks[i] = newNaughtyDisk(erasureDisks[i], nil, errFaultyDisk)
		}
		return erasureDisks
	}

	z.serverPools[0].erasureDisksMu.Unlock()
	_, err = obj.DeleteObject(ctx, bucket, object, ObjectOptions{})
	if !errors.Is(err, errErasureWriteQuorum) {
		t.Fatal(err)
	}

	// Create "obj" under "bucket".

call <i>n</i> of <code>l.Unlock()</code> is synchronized before call <i>m</i> of <code>l.Lock()</code> returns.
</p>

<p>
This program:
</p>

<pre>
var l sync.Mutex
var a string

func f() {
	a = "hello, world"
	l.Unlock()
}

func main() {
	l.Lock()
	go f()
	l.Lock()
	print(a)
}
</pre>

		// - xl.meta metadata is still verified for quorum under lock()
		//   however writing the response doesn't need to serialize
		//   concurrent writers
		unlockOnDefer = true
		nsUnlocker = func() { lock.RUnlock(lkctx) }
	}

	fi, metaArr, onlineDisks, err := er.getObjectFileInfo(ctx, bucket, object, opts, true)
	if err != nil {
		return nil, toObjectErr(err, bucket, object)
	}

	// This allows another goroutine to close the reader.
	pr.mu.Lock()
	defer pr.mu.Unlock()
	if pr.rc == nil {
		return 0, io.EOF
	}
	return pr.rc.Read(p)
}

func (pr *syncReadCloser) Close() error {
	pr.mu.Lock()
	defer pr.mu.Unlock()
	if pr.rc != nil {
		err := pr.rc.Close()
		pr.rc = nil
		return err
	}
	return nil

	currentMinute    serviceRTTMinuteStats
}

func (h *metrics) setConnSuccess(reqStartTime time.Time) {
	h.Lock()
	defer h.Unlock()
	h.LastCheckSuccess = reqStartTime
}

func (h *metrics) setConnFailure(reqStartTime time.Time) {
	h.Lock()
	defer h.Unlock()
	h.LastCheckFailure = reqStartTime
}

func (h *metrics) updateLastFullMinute(currReqMinute time.Time) {

	globalServiceFreezeMu.Lock()
	// If multiple calls, first one creates channel.
	globalServiceFreezeCnt++
	if globalServiceFreezeCnt == 1 {
		globalServiceFreeze.Store(make(chan struct{}))
	}
	globalServiceFreezeMu.Unlock()
}

// unfreezeServices will unfreeze all incoming S3 API calls.
// For each call, unfreezeServices must be called once.
func unfreezeServices() {
	// We need a lock since we need the 2 atomic values to remain in sync.