I am quite new to concurrent programming, threads, shared memory, message passing and so on.
In my example certain events are not handled (messages are not printed) and I don’t understand why.
To motivate my code a little: The problem I want to solve (currently) is only a simple blinking LED connected to a Raspberry Pi. The main thread is a web server (axum) that handles messages and changes the led-state accordingly. I want to run the LED-control-code in another thread that listens to messages sent over a channel:

enum ThreadControl {
    Quit,
    LedMessage(LedState),
}

enum LedState {
    Off,
    On,
    BlinkOnOff { period_ms: u16 },
    // BreathInOutLinear { period_ms: u16 },
    // BreathInOutLogarithmic { period_ms: u16 },
    // FallingSawtoothLinear { period_ms: u16 },
    // RisingSawtoothLinear { period_ms: u16 },
    // AttackDecay { attack_ms: u16, decay_ms: u16 },
    // ... more mindblowing blink-stuff that might 
    // become complicated and should run independently
}

Next I define a function that controls the LED in a loop and listens to ThreadControl-messages sent over a message-passing-channel and spawn that function in a thread. While the led-control-thread is running, I start another thread that sends ThreadControl-messages to change the LED’s behavior or request the function to stop the loop. (Maybe I don’t need another thread to send messages, I’m not sure).

use std::{
    sync::mpsc::{channel, Receiver},
    thread::{self, sleep, spawn},
    time::{Duration, Instant},
};

fn run_led_thread(rx: Receiver<ThreadControl>) {
    println!("hello from led control thread");

    let mut pin_state = false; // later will be the actual GPIO pin
    let mut led_state = LedState::Off;
    let mut now = Instant::now();
    let mut keep_running = true;

    loop {
        rx.iter().for_each(|msg| match msg {
            ThreadControl::LedMessage(new_led_state) => {
                println!("Handling led message");
                led_state = new_led_state;
            }
            ThreadControl::Quit => {
                println!("Quitting thread");
                keep_running = false;
            }
        });

        if keep_running {
            match led_state {
                LedState::Off => {
                    pin_state = false;
                    println!("off")
                }
                LedState::On => {
                    pin_state = true;
                    println!("on")
                }
                LedState::BlinkOnOff { period_ms: value } => {
                    if now.elapsed() > Duration::from_millis((value as u64) / 2) {
                        pin_state = !pin_state;
                        now = Instant::now();
                        match pin_state {
                            true => println!("blink: on"),
                            false => println!("blink: off"),
                        }
                    }
                }
            }
            // avoid thread running at 100%
            // sleep arbitrary duration
            // maybe there's a better solution?
            sleep(Duration::from_millis(5))
        } else {
            break;
        }
    }
}

When I run this example I don’t get the expected output. I get:

hello from led control thread
Handling led message
Handling led message
Handling led message
Quitting thread

What I would expect is

hello from led control thread
Handling led message
on
Handling led message
off
Handling led message
blink: on
blink: off
blink: on
... // and so on
Quitting thread

Somehow that second match (which matches LedState) is not working as no messages are printed.
What am I doing wrong?

Also:
Is this a clever solution in the first place, or is it rather stupid for this kind of problem. I noticed that receiver seems to have a kind of queue. In my case LED-example I don’t expect the queue to mostly be one item (or none at all).
In Rust there is also shared state with Arc<Mutex< ... >> which I also considered. But somewhere I read “don’t communicate via shared memory”.