Guidance on writing code that deadlocks for Dining Philosophers

[zmaril]

Is it possible to compile code that deadlocks in Rust? I'm trying to break the Dining Philosophers code and get it to deadlock but I can't seem to get it to freeze up. I've tried switching the forks of the last philosopher to 4,0 instead but it still all finishes. I know this is a storied problem with a long history and I'd like to see/write a partial solution and see what it looks like in Rust. However, I don't know if Rust is smart enough to stop me and is somehow mitigating all the deadlocks I am introducing.

[zmaril]

By introducing a small pause between reaching for the forks I was able to introduce a deadlock.

fn eat(&self, table: &Table){
    println!("{} is reaching for the {} fork",self.name,self.left);
    let _left = table.forks[self.left].lock().unwrap();
    println!("{} got the {} fork!",self.name, self.left);

    println!("{} pauses to compose themselves.", self.name);
    thread::sleep_ms(100);

    println!("{} is reaching for the {} fork",self.name,self.right);
    let _right = table.forks[self.right].lock().unwrap();
    println!("{} got the {} fork!", self.name,self.right);

    println!("{} got the forks! Time to eat.", self.name);
    thread::sleep_ms(1000);
    println!("{} is done eating.", self.name);
}

Knowing that I can write Rust deadlocks and then see how reversing the arguments fixes the deadlock helps me understand what Rust can and cannot do. Would folks be interested in a pull request expanding the Dining Philosophers page to include example that actually deadlocks?

[steveklabnik]

So, it introduces the possibility of deadlock, it doesn't guarantee that it will. As you've noticed. :)

We already have https://github.com/rust-lang/rust/issues/27932 open, and it hasn't been dealt with, so I'm going to give this ticket a close, as it's effectively a dup. I would take a PR with your explanation, as it would fix that issue too :)