// Custom "wait group with timeout" for waiting for fakeServer calls in a goroutine to finish
type WaitGroup struct {
	count int32
	done  chan struct{}
}

func NewWaitGroup() *WaitGroup {
	return &WaitGroup{
		done: make(chan struct{}),
	}
}

func NewWaitForNCalls(t *testing.T, n int32) (*WaitGroup, func()) {
	wg := &WaitGroup{
		done: make(chan struct{}),
	}

	wg.Add(n)
	return wg, func() {

func (sys *NotificationSys) StorageInfo(objLayer ObjectLayer, metrics bool) StorageInfo {
	var storageInfo StorageInfo
	replies := make([]StorageInfo, len(sys.peerClients))

	var wg sync.WaitGroup
	for i, client := range sys.peerClients {
		if client == nil {
			continue
		}
		wg.Add(1)
		go func(client *peerRESTClient, idx int) {
			defer wg.Done()

// - Non-healing disks
// - Healing disks (if inclHealing is true)
func (er erasureObjects) getOnlineDisksWithHealingAndInfo(inclHealing bool) (newDisks []StorageAPI, newInfos []DiskInfo, healing int) {
	var wg sync.WaitGroup
	disks := er.getDisks()
	infos := make([]DiskInfo, len(disks))
	r := rand.New(rand.NewSource(time.Now().UnixNano()))
	for _, i := range r.Perm(len(disks)) {
		i := i
		wg.Add(1)
		go func() {

	return err
}

// WaitPipe implements wait-group backend io.Pipe to provide
// synchronization between read() end with write() end.
func WaitPipe() (*PipeReader, *PipeWriter) {
	r, w := io.Pipe()
	var wg sync.WaitGroup
	wg.Add(1)
	return &PipeReader{
			PipeReader: r,
			wait:       wg.Wait,
		}, &PipeWriter{
			PipeWriter: w,
			done:       wg.Done,
		}

	globalLocalDrivesMu.RLock()
	localDrives := cloneDrives(globalLocalDrives)
	globalLocalDrivesMu.RUnlock()

	// Initialize sync waitgroup.
	g := errgroup.WithNErrs(len(localDrives))

	// Disk states slices
	beforeState := make([]string, len(localDrives))
	afterState := make([]string, len(localDrives))

type streamingBitrotWriter struct {
	iow          io.WriteCloser
	closeWithErr func(err error) error
	h            hash.Hash
	shardSize    int64
	canClose     *sync.WaitGroup
}

func (b *streamingBitrotWriter) Write(p []byte) (int, error) {
	if len(p) == 0 {
		return 0, nil
	}
	b.h.Reset()
	b.h.Write(p)
	hashBytes := b.h.Sum(nil)
	_, err := b.iow.Write(hashBytes)

// and re-arranges the disks in proper position.
func (s *erasureSets) connectDisks() {
	defer func() {
		s.lastConnectDisksOpTime = time.Now()
	}()

	var wg sync.WaitGroup
	diskMap := s.getDiskMap()
	for _, endpoint := range s.endpoints.Endpoints {
		cdisk := diskMap[endpoint]
		if cdisk != nil && cdisk.IsOnline() {
			if s.lastConnectDisksOpTime.IsZero() {
				continue
			}

func selfSpeedTest(ctx context.Context, opts speedTestOpts) (SpeedTestResult, error) {
	objAPI := newObjectLayerFn()
	if objAPI == nil {
		return SpeedTestResult{}, errServerNotInitialized
	}

	var wg sync.WaitGroup
	var errOnce sync.Once
	var retError string
	var totalBytesWritten uint64
	var totalBytesRead uint64

	objCountPerThread := make([]uint64, opts.concurrency)

		// TOTAL
		time.Sleep(2 * testDrwMutexAcquireTimeout)
		// fmt.Println("Unlocking dm1")

		dm1st.Unlock(context.Background())
	}()
	expect += 2 * testDrwMutexAcquireTimeout

	var wg sync.WaitGroup
	wg.Add(2)

	go func() {
		defer wg.Done()

		dm2nd.Lock(id, source)

		// Release lock after 10 seconds
		go func() {
			time.Sleep(2 * testDrwMutexAcquireTimeout)

		}
	}
}

func TestReaderAtConcurrent(t *testing.T) {
	// Test for the race detector, to verify ReadAt doesn't mutate
	// any state.
	r := NewReader([]byte("0123456789"))
	var wg sync.WaitGroup
	for i := 0; i < 5; i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()
			var buf [1]byte
			r.ReadAt(buf[:], int64(i))
		}(i)
	}
	wg.Wait()
}