Explore the intricacies of futexes in this 27-minute Linux Foundation conference talk. Delve into the challenges posed by the FUTEX API design, which has led to limited kernel knowledge about futex locations and permissions. Examine the regular cases handled by kernel code and the numerous corner cases that arise. Learn how these issues particularly impact real-time (-RT) systems and discover the improvements made to benefit both RT and non-RT users. Gain insights into the process of identifying and addressing these challenges, presented by Sebastian Siewior from Linutronix GmbH, a long-time maintainer of the Preempt-RT patchset. Ideal for RT users and developers, this talk builds upon Siewior's previous presentation on maintaining the -RT patchset in relation to mainline Linux development.