Fix new lua threads not breaking scheduler out of futures resumption

src/lune/scheduler/impl_runner.rs

@@ -89,12 +89,25 @@ where
     async fn run_futures(&self) -> bool {
         let mut resumed_any = false;
 
-        let mut futs = self
-            .futures
-            .try_lock()
-            .expect("Failed to lock futures queue");
-        while futs.next().await.is_some() {
-            resumed_any = true;
+        loop {
+            let mut rx = self.new_thread_ready.subscribe();
+
+            let mut futs = self
+                .futures
+                .try_lock()
+                .expect("Failed to lock futures queue");
+
+            // Wait until we either get a new lua thread or a future completes
+            tokio::select! {
+                _res = rx.recv() => break,
+                res = futs.next() => {
+                    match res {
+                        Some(_) => resumed_any = true,
+                        None => break,
+                    }
+                },
+            }
+
             if self.has_thread() {
                 break;
             }

src/lune/scheduler/impl_threads.rs

@@ -57,6 +57,12 @@ where
             .context("Failed to borrow threads vec")?
             .push_front(thread);
 
+        // NOTE: We might be resuming futures, need to signal that a
+        // new lua thread is ready to break out of futures resumption
+        if self.new_thread_ready.receiver_count() > 0 {
+            self.new_thread_ready.send(()).ok();
+        }
+
         Ok(())
     }
 
@@ -84,6 +90,12 @@ where
             .borrow_mut()
             .insert(thread_id, SchedulerThreadSender::new(1));
 
+        // NOTE: We might be resuming futures, need to signal that a
+        // new lua thread is ready to break out of futures resumption
+        if self.new_thread_ready.receiver_count() > 0 {
+            self.new_thread_ready.send(()).ok();
+        }
+
         Ok(thread_id)
     }
 
@@ -111,6 +123,12 @@ where
             .borrow_mut()
             .insert(thread_id, SchedulerThreadSender::new(1));
 
+        // NOTE: We might be resuming futures, need to signal that a
+        // new lua thread is ready to break out of futures resumption
+        if self.new_thread_ready.receiver_count() > 0 {
+            self.new_thread_ready.send(()).ok();
+        }
+
         Ok(thread_id)
     }
 

src/lune/scheduler/mod.rs

@@ -7,7 +7,10 @@ use std::{
 
 use futures_util::{stream::FuturesUnordered, Future};
 use mlua::prelude::*;
-use tokio::sync::Mutex as AsyncMutex;
+use tokio::sync::{
+    broadcast::{channel, Sender},
+    Mutex as AsyncMutex,
+};
 
 mod state;
 mod thread;
@@ -40,16 +43,20 @@ pub(crate) struct Scheduler<'lua, 'fut> {
     threads: Arc<RefCell<VecDeque<SchedulerThread>>>,
     thread_senders: Arc<RefCell<HashMap<SchedulerThreadId, SchedulerThreadSender>>>,
     futures: Arc<AsyncMutex<FuturesUnordered<SchedulerFuture<'fut>>>>,
+    new_thread_ready: Sender<()>,
 }
 
 impl<'lua, 'fut> Scheduler<'lua, 'fut> {
     pub fn new(lua: &'lua Lua) -> Self {
+        let (new_thread_ready, _) = channel(1);
+
         let this = Self {
             lua,
             state: Arc::new(SchedulerState::new()),
             threads: Arc::new(RefCell::new(VecDeque::new())),
             thread_senders: Arc::new(RefCell::new(HashMap::new())),
             futures: Arc::new(AsyncMutex::new(FuturesUnordered::new())),
+            new_thread_ready,
         };
 
         // Propagate errors given to the scheduler back to their lua threads