* always under a lock.
     */
    private static final class SupplantableFuture implements Cancellable {
      private final ReentrantLock lock;

      @GuardedBy("lock")
      private Future<@Nullable Void> currentFuture;

      SupplantableFuture(ReentrantLock lock, Future<@Nullable Void> currentFuture) {
        this.lock = lock;
        this.currentFuture = currentFuture;
      }

			Op:   "open",
			Path: path,
			Err:  syscall.EINVAL,
		}
	}

	lock := syscall.Flock_t{
		Start:  0,
		Len:    0,
		Pid:    0,
		Type:   lockType,
		Whence: 0,
	}

	f, err := os.OpenFile(path, flag, perm)
	if err != nil {
		return nil, err
	}

	if err = syscall.FcntlFlock(f.Fd(), rlockType, &lock); err != nil {
		f.Close()
		if err == syscall.EAGAIN {
			err = ErrAlreadyLocked
		}

			return
		}
	}
}

func (m *Monitor) updateMovingAvg() {
	m.mlock.Lock()
	defer m.mlock.Unlock()
	for _, bucketMeasurement := range m.bucketsMeasurement {
		bucketMeasurement.updateExponentialMovingAverage(time.Now())
	}
}

func (m *Monitor) init(opts BucketOptions) {
	m.mlock.Lock()
	defer m.mlock.Unlock()

	_, ok := m.bucketsMeasurement[opts]
	if !ok {

					}

					toUnLock = toUnLock[:0]
					for k, v := range l.lockMap {
						for _, lock := range v {
							toUnLock = append(toUnLock, dsync.LockArgs{Resources: []string{k}, UID: lock.UID, Owner: lock.Owner})
						}
					}
					start = time.Now()
					for _, lock := range toUnLock {
						ok, err := l.RUnlock(t.Context(), lock)
						if err != nil || !ok {
							t.Fatal(err)
						}
					}

		panic("Failed to acquire read lock")
	}
	// fmt.Println("1st read lock acquired, waiting...")

	drwm2 := NewDRWMutex(ds, "simplelock")
	ctx2, cancel2 := context.WithCancel(t.Context())
	if !drwm2.GetRLock(ctx2, cancel2, id, source, Options{Timeout: time.Second}) {
		panic("Failed to acquire read lock")
	}
	// fmt.Println("2nd read lock acquired, waiting...")

	go func() {

```sh
aws s3api put-object --bucket testbucket --key lockme --object-lock-mode GOVERNANCE --object-lock-retain-until-date "2019-11-20"  --body /etc/issue
```

    for (int i = 0; i < reps; i++) {
      lock.lock();
      lock.unlock();
    }
  }

  @Benchmark
  void orderedPlainLocks(int reps) {
    lockAndUnlockNested(plainLocks, reps);
  }

  @Benchmark
  void orderedCycleDetectingLocks(int reps) {
    lockAndUnlockNested(detectingLocks, reps);
  }

  private static void lockAndUnlockNested(Lock[] locks, int reps) {

     * error-prone code like:
     *
     * Striped<Lock> stripedLock = Striped.lazyWeakXXX(...)'
     * Iterable<Lock> locks = stripedLock.bulkGet(keys);
     * for (Lock lock : locks) {
     *   lock.lock();
     * }
     * operation();
     * for (Lock lock : locks) {
     *   lock.unlock();
     * }
     *

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

/** Forwarding wrapper around a {@code Lock}. */
@J2ktIncompatible
@GwtIncompatible
abstract class ForwardingLock implements Lock {
  abstract Lock delegate();

  @Override
  public void lock() {
    delegate().lock();
  }

  @Override
  public void lockInterruptibly() throws InterruptedException {

}

// RLock holds a read lock on lm.
//
// If one or more read lock are already in use, it will grant another lock.
// Otherwise the calling go routine blocks until the mutex is available.
func (lm *LRWMutex) RLock() {
	const isWriteLock = false
	lm.lockLoop(context.Background(), lm.id, lm.source, 1<<63-1, isWriteLock)
}

// GetRLock tries to get a read lock on lm before the timeout occurs.