This is exactly the scenario that Simon Peyton Jones used to motivate Software Transactional Memory (STM) in his 2007 "Beautiful Concurrency" paper: http://res

This is exactly the scenario that Simon Peyton Jones used to motivate Software Transactional Memory (STM) in his 2007 "Beautiful Concurrency" paper: http://research.microsoft.com/pubs/74063/beautiful.pdf http://research.microsoft.com/pubs/74063/beautiful.pdf or we push locking up the chain to their users That's still prone to deadlock. Suppose each account has its own lock. Then to transfer from account A to B, the code might look like A.lock(); B.lock(); A.withdraw( amount ); B.deposit( amount ); B.unlock(); A.unlock(); If another transfer occurs in the reverse direction at exactly the same time, the code deadlocks in the middle of the first line. SPJ explains this and other cases pretty well.