Waker

    const Waker = struct {
        sleeper: Sleeper = undefined,
        futex: *Futex,
        ptr: *const u32,
        max_waiters: u32,

        fn remove(context: ?*anyopaque) callconv(.c) void {
            const waker: *Waker = @ptrCast(@alignCast(context));
            const futex = waker.futex;
            const ptr = waker.ptr;
            const max_waiters = waker.max_waiters;

            var num_removed: usize = 0;
            var next_node = futex.waiters.first;
            while (num_removed < max_waiters) {
                const waiter: *Waiter = @fieldParentPtr("node", next_node orelse break);
                next_node = waiter.node.next;
                if (waiter.ptr != ptr) {
                    @branchHint(.unlikely);
                    continue;
                }
                waiter.tryRemove() catch |err| switch (err) {
                    error.CancelRequested => continue,
                };
                num_removed += 1;
            }
            assert(@atomicRmw(usize, &futex.num_waiters, .Sub, num_removed, .monotonic) >= num_removed);

            var sleeper = waker.sleeper;
            waker.* = undefined;
            Sleeper.wake(&sleeper);
        }
    }