runtime: re-enable ignored io shutdown tests in rt_handle_block_on (#8404)

These tests were added in #3569 (2021) but immediately marked
`#[ignore]` because of a then-known bug where shutting down the io
driver while concurrently registering new resources was unsound.

That bug class was resolved by the io driver rewrite in #5833, which
replaced the slab-based registration with a `RegistrationSet` guarded by
a mutex-protected `Synced`. Allocating a new registration now checks
`is_shutdown` under the lock and returns a proper error instead of
racing, so binding a resource after (or concurrently with) runtime
shutdown fails deterministically.

Re-enable the 7 ignored tests (across the 3 scheduler configurations).
Five of them pass unchanged. The two `unix_listener_shutdown_after_*`
tests asserted the old `"reactor gone"` message; #5833 unified that path
onto the single `RUNTIME_SHUTTING_DOWN_ERROR` string, so update those two
assertions to the current message.

tokio/tests/rt_handle_block_on.rs

@@ -1,12 +1,6 @@
 #![warn(rust_2018_idioms)]
 #![cfg(feature = "full")]
 
-// All io tests that deal with shutdown is currently ignored because there are known bugs in with
-// shutting down the io driver while concurrently registering new resources. See
-// https://github.com/tokio-rs/tokio/pull/3569#pullrequestreview-612703467 for more details.
-//
-// When this has been fixed we want to re-enable these tests.
-
 use std::time::Duration;
 use tokio::runtime::{Handle, Runtime};
 use tokio::sync::mpsc;
@@ -250,8 +244,6 @@ rt_test! {
             .unwrap();
     }
 
-    // All io tests are ignored for now. See above why that is.
-    #[ignore]
     #[test]
     fn tcp_listener_connect_after_shutdown() {
         let rt = rt();
@@ -263,15 +255,9 @@ rt_test! {
             .block_on(net::TcpListener::bind("127.0.0.1:0"))
             .unwrap_err();
 
-        assert_eq!(err.kind(), std::io::ErrorKind::Other);
-        assert_eq!(
-            err.get_ref().unwrap().to_string(),
-            "A Tokio 1.x context was found, but it is being shutdown.",
-        );
+        assert!(tokio::runtime::is_rt_shutdown_err(&err));
     }
 
-    // All io tests are ignored for now. See above why that is.
-    #[ignore]
     #[test]
     fn tcp_listener_connect_before_shutdown() {
         let rt = rt();
@@ -283,11 +269,7 @@ rt_test! {
 
         let err = Handle::current().block_on(bind_future).unwrap_err();
 
-        assert_eq!(err.kind(), std::io::ErrorKind::Other);
-        assert_eq!(
-            err.get_ref().unwrap().to_string(),
-            "A Tokio 1.x context was found, but it is being shutdown.",
-        );
+        assert!(tokio::runtime::is_rt_shutdown_err(&err));
     }
 
     #[test]
@@ -301,8 +283,7 @@ rt_test! {
             .unwrap();
     }
 
-    // All io tests are ignored for now. See above why that is.
-    #[ignore]
+    #[cfg_attr(miri, ignore)] // No UDP sockets in miri.
     #[test]
     fn udp_stream_bind_after_shutdown() {
         let rt = rt();
@@ -314,15 +295,10 @@ rt_test! {
             .block_on(net::UdpSocket::bind("127.0.0.1:0"))
             .unwrap_err();
 
-        assert_eq!(err.kind(), std::io::ErrorKind::Other);
-        assert_eq!(
-            err.get_ref().unwrap().to_string(),
-            "A Tokio 1.x context was found, but it is being shutdown.",
-        );
+        assert!(tokio::runtime::is_rt_shutdown_err(&err));
     }
 
-    // All io tests are ignored for now. See above why that is.
-    #[ignore]
+    #[cfg_attr(miri, ignore)] // No UDP sockets in miri.
     #[test]
     fn udp_stream_bind_before_shutdown() {
         let rt = rt();
@@ -334,15 +310,10 @@ rt_test! {
 
         let err = Handle::current().block_on(bind_future).unwrap_err();
 
-        assert_eq!(err.kind(), std::io::ErrorKind::Other);
-        assert_eq!(
-            err.get_ref().unwrap().to_string(),
-            "A Tokio 1.x context was found, but it is being shutdown.",
-        );
+        assert!(tokio::runtime::is_rt_shutdown_err(&err));
     }
 
-    // All io tests are ignored for now. See above why that is.
-    #[ignore]
+    #[cfg_attr(miri, ignore)] // No Unix domain sockets in miri.
     #[cfg(unix)]
     #[test]
     fn unix_listener_bind_after_shutdown() {
@@ -356,15 +327,10 @@ rt_test! {
 
         let err = net::UnixListener::bind(path).unwrap_err();
 
-        assert_eq!(err.kind(), std::io::ErrorKind::Other);
-        assert_eq!(
-            err.get_ref().unwrap().to_string(),
-            "A Tokio 1.x context was found, but it is being shutdown.",
-        );
+        assert!(tokio::runtime::is_rt_shutdown_err(&err));
     }
 
-    // All io tests are ignored for now. See above why that is.
-    #[ignore]
+    #[cfg_attr(miri, ignore)] // No Unix domain sockets in miri.
     #[cfg(unix)]
     #[test]
     fn unix_listener_shutdown_after_bind() {
@@ -381,12 +347,10 @@ rt_test! {
         // this should not timeout but fail immediately since the runtime has been shutdown
         let err = Handle::current().block_on(listener.accept()).unwrap_err();
 
-        assert_eq!(err.kind(), std::io::ErrorKind::Other);
-        assert_eq!(err.get_ref().unwrap().to_string(), "reactor gone");
+        assert!(tokio::runtime::is_rt_shutdown_err(&err));
     }
 
-    // All io tests are ignored for now. See above why that is.
-    #[ignore]
+    #[cfg_attr(miri, ignore)] // No Unix domain sockets in miri.
     #[cfg(unix)]
     #[test]
     fn unix_listener_shutdown_after_accept() {
@@ -405,8 +369,7 @@ rt_test! {
         // this should not timeout but fail immediately since the runtime has been shutdown
         let err = Handle::current().block_on(accept_future).unwrap_err();
 
-        assert_eq!(err.kind(), std::io::ErrorKind::Other);
-        assert_eq!(err.get_ref().unwrap().to_string(), "reactor gone");
+        assert!(tokio::runtime::is_rt_shutdown_err(&err));
     }
 
     // ==== nesting ======