Time not advancing with spawn_blocking from a LocalSet

[mcches]

Version
List the versions of all tokio crates you are using. The easiest way to get
this information is using cargo tree subcommand:

cargo tree | grep tokio

tokio = { version = "1", features = ["full"] }

Platform
The output of uname -a (UNIX), or version and 32 or 64-bit (Windows)

uname -a
Darwin 6c7e67b9eeac 22.6.0 Darwin Kernel Version 22.6.0: Thu Nov  2 07:43:25 PDT 2023; root:xnu-8796.141.3.701.17~6/RELEASE_ARM64_T6020 arm64

Description
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One way to structure the description:

Time does not advance with a paused runtime when a spawn_blocking task is running (or blocking).

This seems related to: #5115

I tried this code:

#[test]
fn spawn_blocking() {
    let rt = tokio::runtime::Builder::new_current_thread()
        .enable_time()
        .start_paused(true)
        .build()
        .unwrap();

    let _g = rt.enter();

    let ls = tokio::task::LocalSet::new();
    ls.spawn_local(async {
        tokio::task::spawn_blocking(|| {
            println!("{:?}: parking...", std::thread::current().name());
            std::thread::park()
        });
    });

    rt.block_on(async {
        println!("{:?}: run_until for 10ms", std::thread::current().name());
        ls.run_until(tokio::time::sleep(Duration::from_millis(10)))
            .await;

        println!("run_until done");
    });
}

I expected to see this happen: I'd expect the run_until to complete, albeit instantaneously,

Instead, this happened: "run_until done" never emits

[Darksonn]

It's because time is paused. Time does not advance if there are any spawn_blocking tasks.

[Darksonn]

Closing as working-as-intended.