Tasks make updates requested by calling tasks to a shared resource serially in a first come first served manner, atomically, but not necessarily synchronously, such that a current task holding an exclusive lock on the shared resource makes the updates on behalf of one or more calling tasks queued on the lock. Updates waiting in a queue on the lock to the shared resource may be made while the lock is held, and others deferred for post processing after the lock is released. Some update requests may also, at the calling application's option, be executed synchronously. Provision is made for nested asynchronous locking. Data structures (wait_elements) describing update requests may queued in a wait queue for update requests awaiting execution by a current task, other than the calling task, currently holding an exclusive lock on the shared resource. Other queues are provided for queuing data structures removed from the wait queue but not yet processed; data structures for requests to unlock or downgrade a lock; data structures for requests which have been processed and need to be returned to free storage; and data structures for requests that need to be awakened or that describe post processing routines that are to be run while the lock is not held.