November 11, 2009 This article was contributed by Darren Hart The futex [PDF] mechanism, introduced in 2.5.7 by Rusty Russell, Hubertus Franke, and Mathew Kirkwood, is a fast, lightweight kernel-assisted locking primitive for user-space applications. It provides for very fast uncontended lock acquisition and release. The futex state is stored in a user-space variable (an unsigned 32-bit integer on