<tteras> old kernels have only eventfd()
<tteras> they noticed uh oh, we need add a new parameter
<tteras> so there's eventfd2() syscall
<tteras> when it was added to glibc
<tteras> eventfd2 was already there
<tteras> so the glibc call got name eventfd() even though it had signature of syscall eventfd2()
<ncopa> so they picked eventfd()
<tteras> yeah
<ncopa> doh

Requires 2.6.27+ kernel. The old eventfd() syscall, is not really usable
and emulation is not feasible.