Landing a New syscall, part 1: What is Futex?

Over the past 18 months, Collabora has been on a roller-coaster ride developing futex2, a new set of system calls. As part of this prolonged effort, the futex_waitv() syscall has now successfully landed in Linux 5.16. A followup of the initial futex syscall, this new interface aims to overcome long term issues that have been limiting the way applications use the Linux kernel. But what exactly is futex? This series of posts will help answer that and other questions around this tricky function.