1).Start some amount of threads. 2).Each thread simultaneously with others obtains lock through LockService#getLock then performs tryLock with timeout. For example with timeout equal to 1 second. 3).After successful lock the thread tries to increment an accessible by all threads counter. 4).Thread sleeps for some time. For example for 100ms. 5).Thread decrements the counter. 6).Thread performs unlock. 7).Each thread works during some time. Problem: in normal case the counter should have value 0 right after successful tryLock but sometimes it has value 1 meaning that some other thread modifies the counter at the same time.