A new futex API

"Futexes are cursed" as I recall was basically about the difficulty of fixing them in the kernel, and "Pthread Condvars" was about the difficulty of fixing them in glibc. Problems, as described by the reliably excellent LWN article, were false (misordered) wakeups and no ability to implement priority inheritance. The root cause is too fee bits to indicate state, as is so often the case for older APIs. Recently I have thought that it's too bad that the kernel chose not to break the futex() ABI at the same time it essentially forced distros to switch to 64-bit time.