8268285: vmTestbase/nsk/jvmti/GetThreadState/thrstat002 failed with "Wrong thread "thr1" (...) state after SuspendThread"

Reviewed-by: lmesnik, amenkov, dholmes

Author: Serguei Spitsyn

test/hotspot/jtreg/vmTestbase/nsk/jvmti/GetThreadState/thrstat002.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2004, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2004, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -158,8 +158,11 @@ public void run() {
             }
             System.out.println("thrstat002a.run after blockingMonitor lock");
 
+            System.out.println("thrstat002a.run before runningBarrier unlock");
             thrstat002.runningBarrier.unlock();
-            System.out.println("thrstat002a.run after runningBarrier unlock");
+
+            // Don't do println's from this point until we have exited the loop,
+            // else we can suspend in the println in an unexpected state.
             int i = 0;
             int n = 1000;
             while (flag) {

test/hotspot/jtreg/vmTestbase/nsk/jvmti/GetThreadState/thrstat002/thrstat002.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2004, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2004, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -355,6 +355,7 @@ Java_nsk_jvmti_GetThreadState_thrstat002_checkStatus(JNIEnv *env, jclass cls,
             result = STATUS_FAILED;
         }
     }
+    fflush(0);
 }
 
 JNIEXPORT jint JNICALL