runtime: fix race in yield_defers_until_park test (#6809)

tokio/tests/rt_common.rs

@@ -785,9 +785,9 @@ rt_test! {
             barrier.wait();
 
             let (fail_test, fail_test_recv) = oneshot::channel::<()>();
-
+            let flag_clone = flag.clone();
             let jh = tokio::spawn(async move {
-                // Create a TCP litener
+                // Create a TCP listener
                 let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
                 let addr = listener.local_addr().unwrap();
 
@@ -798,7 +798,7 @@ rt_test! {
 
                         // Yield until connected
                         let mut cnt = 0;
-                        while !flag.load(SeqCst){
+                        while !flag_clone.load(SeqCst){
                             tokio::task::yield_now().await;
                             cnt += 1;
 
@@ -814,7 +814,7 @@ rt_test! {
                     },
                     async {
                         let _ = listener.accept().await.unwrap();
-                        flag.store(true, SeqCst);
+                        flag_clone.store(true, SeqCst);
                     }
                 );
             });
@@ -824,6 +824,11 @@ rt_test! {
             let success = fail_test_recv.await.is_err();
 
             if success {
+                // Setting flag to true ensures that the tasks we spawned at
+                // the beginning of the test will exit.
+                // If we don't do this, the test will hang since the runtime waits
+                // for all spawned tasks to finish when dropping.
+                flag.store(true, SeqCst);
                 // Check for panics in spawned task.
                 jh.abort();
                 jh.await.unwrap();