cred: initialize V8 inside its Tokio executor and verify concurrent limits

host/src/cred/v8.rs

@@ -51,6 +51,12 @@ fn evaluate(
         .max_memory_bytes
         .unwrap_or(8 * 1024 * 1024)
         .clamp(256 * 1024, 32 * 1024 * 1024);
+    // V8 uses Tokio for internal delayed tasks, even without guest extensions.
+    let executor = tokio::runtime::Builder::new_current_thread()
+        .enable_time()
+        .build()
+        .map_err(|_| failure(ErrorKind::Engine))?;
+    let _entered = executor.enter();
     let mut runtime = JsRuntime::new(RuntimeOptions {
         // Bootstrap before imposing the caller's budget: V8 cannot recover from
         // bootstrap OOM because the runtime cannot install its callback yet.
@@ -160,10 +166,7 @@ fn evaluate(
             })),
         }
     };
-    let result = tokio::runtime::Builder::new_current_thread()
-        .build()
-        .map_err(|_| failure(ErrorKind::Engine))?
-        .block_on(task);
+    let result = executor.block_on(task);
     let _ = done.send(());
     let _ = watchdog.join();
     if limited.load(Ordering::SeqCst) {

host/tests/cred_v8.rs

@@ -132,6 +132,8 @@ fn sandbox_and_isolation() {
 }
 #[test]
 fn independent_deadlines() {
+    // Exclude the process-wide platform initialization from the overlap check.
+    assert_eq!(run("export default ()=>true").unwrap(), "true");
     let barrier = std::sync::Arc::new(std::sync::Barrier::new(2));
     let other = barrier.clone();
     let runaway = std::thread::spawn(move || {
@@ -152,9 +154,12 @@ fn independent_deadlines() {
         );
     });
     barrier.wait();
-    let start = Instant::now();
+    // The quick call keeps its default 100 ms execution deadline.
     assert_eq!(run("export default ()=>true").unwrap(), "true");
-    assert!(start.elapsed() < Duration::from_millis(500));
+    assert!(
+        !runaway.is_finished(),
+        "the quick call must finish before the runaway call"
+    );
     runaway.join().unwrap();
 }