Use futures_util mutex instead of flume for sending flush lock wakeups

packages/core/src/global_context.rs

@@ -1,5 +1,5 @@
 use crate::{runtime::Runtime, Element, ScopeId, Task};
-use futures_util::{future::poll_fn, Future};
+use futures_util::Future;
 use std::sync::Arc;
 
 /// Get the current scope id
@@ -257,13 +257,11 @@ pub fn after_render(f: impl FnMut() + 'static) {
 /// Effects rely on this to ensure that they only run effects after the DOM has been updated. Without flush_sync effects
 /// are run immediately before diffing the DOM, which causes all sorts of out-of-sync weirdness.
 pub async fn flush_sync() {
-    // if flushing() {
-    //      return;
-    // }
-
-    _ = Runtime::with(|rt| rt.flush.clone())
+    // Wait for the flush lock to be available
+    // We release it immediately, so it's impossible for the lock to be held longer than this function
+    Runtime::with(|rt| rt.flush_mutex.clone())
         .unwrap()
-        .recv_async()
+        .lock()
         .await;
 }