This ladder locking is also known as lock-coupling in the database world.
It's a good solution when you have lots of tasks and need high concurrency,
and proven in a lot of literature. You might notice more overhead if you only
have a small number of tasks (e.g. 2-3) but it definitely scales better than
just holding onto one lock or a small number of locks.
--
-- Howard Chu
Chief Architect, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc
OpenLDAP Core Team http://www.openldap.org/project/