*
 * <ul>
 *   <li>for an unnested {@code lock()} and {@code unlock()}, a cycle detecting lock takes 38ns as
 *       opposed to the 24ns taken by a plain lock.
 *   <li>for nested locking, the cost increases with the depth of the nesting:
 *       <ul>
 *         <li>2 levels: average of 64ns per lock()/unlock()
 *         <li>3 levels: average of 77ns per lock()/unlock()
 *         <li>4 levels: average of 99ns per lock()/unlock()

func (r *lockedRandSource) Int63() (n int64) {
	r.lk.Lock()
	n = r.src.Int63()
	r.lk.Unlock()
	return
}

// Seed uses the provided seed value to initialize the generator to a
// deterministic state.
func (r *lockedRandSource) Seed(seed int64) {
	r.lk.Lock()
	r.src.Seed(seed)
	r.lk.Unlock()

func SystemTargets() []Target {
	swapSystemMuRW.RLock()
	defer swapSystemMuRW.RUnlock()

	res := systemTargets
	return res
}

// AuditTargets returns active audit targets.
// Returned slice may not be modified in any way.
func AuditTargets() []Target {
	swapAuditMuRW.RLock()
	defer swapAuditMuRW.RUnlock()

	res := auditTargets
	return res
}

	r  io.Reader
	mu sync.Mutex
}

func (d *disconnectReader) Read(p []byte) (n int, err error) {
	d.mu.Lock()
	defer d.mu.Unlock()
	if d.r != nil {
		return d.r.Read(p)
	}
	return 0, errors.New("reader closed")
}

func (d *disconnectReader) Close() error {
	d.mu.Lock()
	d.r = nil
	d.mu.Unlock()
	return nil
}

	fw *flate.Writer
}

func (w *pooledFlateWriter) Write(p []byte) (n int, err error) {
	w.mu.Lock()
	defer w.mu.Unlock()
	if w.fw == nil {
		return 0, errors.New("Write after Close")
	}
	return w.fw.Write(p)
}

func (w *pooledFlateWriter) Close() error {
	w.mu.Lock()
	defer w.mu.Unlock()
	var err error
	if w.fw != nil {
		err = w.fw.Close()
		flateWriterPool.Put(w.fw)
		w.fw = nil
	}

	}
	ps.Lock()
	defer ps.Unlock()

	sub := &Sub[T]{ch: subCh, types: Mask(mask.Mask()), filter: filter}
	ps.subs = append(ps.subs, sub)

	// We hold a lock, so we are safe to update
	combined := Mask(atomic.LoadUint64(&ps.types))
	combined.Merge(Mask(mask.Mask()))
	atomic.StoreUint64(&ps.types, uint64(combined))

	go func() {
		<-doneCh

		ps.Lock()
		defer ps.Unlock()

		t.Fatal("Unexpected error", err)
	}
}

// Tests lock and unlock semantics.
func TestLockAndUnlock(t *testing.T) {
	f, err := os.CreateTemp("", "lock")
	if err != nil {
		t.Fatal(err)
	}
	f.Close()
	defer func() {
		err = os.Remove(f.Name())
		if err != nil {
			t.Fatal(err)
		}
	}()

	// lock the file
	l, err := LockedOpenFile(f.Name(), os.O_WRONLY, 0o600)
	if err != nil {

func (m *bucketMeasurement) updateExponentialMovingAverage(endTime time.Time) {
	// Calculate aggregate avg bandwidth and exp window avg
	m.lock.Lock()
	defer func() {
		m.startTime = endTime
		m.lock.Unlock()
	}()

	if m.startTime.IsZero() {
		return
	}

	if endTime.Before(m.startTime) {
		return
	}

	duration := endTime.Sub(m.startTime)

			return ctx.Err()
		}
		if opts.Limit > 0 && objsReturned >= opts.Limit {
			return nil
		}

		if s.walkMu != nil {
			s.walkMu.Lock()
		}
		entries, err := s.ListDir(ctx, "", opts.Bucket, current, -1)
		if s.walkMu != nil {
			s.walkMu.Unlock()
		}
		if err != nil {
			// Folder could have gone away in-between
			if err != errVolumeNotFound && err != errFileNotFound {

func (srv *Server) Shutdown() error {
	srv.listenerMutex.Lock()
	if srv.listener == nil {
		srv.listenerMutex.Unlock()
		return http.ErrServerClosed
	}
	srv.listenerMutex.Unlock()

	if atomic.AddUint32(&srv.inShutdown, 1) > 1 {
		// shutdown in progress
		return http.ErrServerClosed
	}

	// Close underneath HTTP listener.
	srv.listenerMutex.Lock()
	err := srv.listener.Close()
	srv.listenerMutex.Unlock()