In Rust, a conditional variable is implemented using a combination of a Mutex and a Condvar from the std::sync module. Here is an example implementation using semaphores and mutexes:

```rust

use std::sync::{Arc, Mutex, Condvar};
use std::thread;

fn main() {
    let data = Arc::new((Mutex::new(false), Condvar::new()));

    let data_clone = data.clone();
    let thread_one = thread::spawn(move || {
        let (lock, cvar) = &*data_clone;
        let mut started = lock.lock().unwrap();
        while !*started {
            started = cvar.wait(started).unwrap();
        }
        println!("Thread one started!");
    });

    let data_clone = data.clone();
    let thread_two = thread::spawn(move || {
        let (lock, cvar) = &*data_clone;
        let mut started = lock.lock().unwrap();
        *started = true;
        cvar.notify_all();
        println!("Thread two started!");
    });

    thread_one.join().unwrap();
    thread_two.join().unwrap();
}
```

In this example, we create a shared data structure data that consists of a `Mutex` and a `Condvar`. The `Mutex` is used to synchronize access to the shared boolean started, while the `Condvar` is used to notify waiting threads when the boolean is set to true.

We then create two threads, thread_one and thread_two. thread_one waits on the Condvar until the boolean started is set to true, while thread_two sets the boolean to true and notifies all waiting threads on the `Condvar`.

Note that we use Arc to share ownership of the data structure between threads, and move closures to transfer ownership of the Arc to each thread.
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