Function futex_wait 

pub fn futex_wait(
    futex: &Atomic<u32>,
    expected: u32,
    timeout: Option<Duration>,
) -> bool

Available on Android or FreeBSD or Linux only.

Waits for a futex_wake operation to wake us.

Returns directly if the futex doesn’t hold the expected value.

Returns false on timeout, and true in all other cases.