signal

    pub fn signal(cond: *Condition, io: Io) void {
        var prev_state = cond.state.load(.monotonic);
        while (prev_state.waiters > prev_state.signals) {
            @branchHint(.unlikely);
            prev_state = cond.state.cmpxchgWeak(prev_state, .{
                .waiters = prev_state.waiters,
                .signals = prev_state.signals + 1,
            }, .release, .monotonic) orelse {
                // Update the epoch to tell the waiting threads that there are new signals for them.
                // Note that a waiting thread could miss a take if *exactly* (1<<32)-1 wakes happen
                // between it observing the epoch and sleeping on it, but this is extraordinarily
                // unlikely due to the precise number of calls required.
                _ = cond.epoch.fetchAdd(1, .release); // `.release` to ensure ordered after `state` update
                io.futexWake(u32, &cond.epoch.raw, 1);
                return;
            };
        }
    }