Post Syndicated from corbet original https://lwn.net/Articles/940944/

The Linux fast user-space mutex (“futex”) subsystem debuted with the 2.6.0
kernel; it provides a mechanism that can be used to implement user-space
locking. Since futexes avoid calling into the kernel whenever possible,
they can indeed be fast, especially in the uncontended case. The API used
to access futexes has never been seen as one of Linux’s strongest points,
though, so there has long been a desire to improve it. This patch
series from Peter Zijlstra shows what the future of futexes may look
like.