8303916: ThreadLists.java inconsistent results

Reviewed-by: cjplummer, dholmes, lmesnik

Author: kevinjwalls

test/jdk/java/lang/management/ThreadMXBean/ThreadLists.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2004, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2004, 2023, 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
@@ -30,10 +30,26 @@
  * @run main/othervm ThreadLists
  */
 import java.lang.management.ManagementFactory;
+import java.lang.management.ThreadInfo;
 import java.lang.management.ThreadMXBean;
 import java.util.Map;
+import java.util.Set;
+import java.util.TreeSet;
 
 public class ThreadLists {
+
+    // Thread names permitted to appear during test:
+    public static final String [] permittedThreadNames = { "ForkJoinPool", "JVMCI" };
+
+    public static boolean isPermittedNewThread(String name) {
+        for (String s : permittedThreadNames) {
+            if (name.contains(s)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     public static void main(String args[]) {
 
         // Bug id : JDK-8151797
@@ -50,44 +66,81 @@ public static void main(String args[]) {
         } while (parent != null);
 
         // get the thread count
-        int activeCount = top.activeCount();
+        int tgActiveCount = top.activeCount();
 
         // Now enumerate to see if we find any extras yet.
-        // Ensure the array is big enough for a few extras.
-        Thread[] threads = new Thread[activeCount * 2];
-        int newCount = top.enumerate(threads);
-        if (newCount != activeCount) {
-            System.out.println("Found different threads after enumeration:");
-        } else {
-            System.out.println("Initial set of enumerated threads:");
+        // Ensure array is big enough for a few extras.
+        Thread[] tgThreads = new Thread[tgActiveCount * 2];
+        int tgNewCount = top.enumerate(tgThreads);
+        Map<Thread, StackTraceElement[]> stackTraces = Thread.getAllStackTraces();
+
+        if (tgNewCount != tgActiveCount) {
+            System.out.println("Found different Thread Group thread count after enumeration: tgActiveCount="
+                               + tgActiveCount + " enumerated=" + tgNewCount);
         }
-        for (int i = 0; i < newCount; i++) {
-            System.out.println(" - Thread: " + threads[i].getName());
+        if (tgNewCount != stackTraces.size()) {
+            System.out.println("Found difference in counts: thread group new count="
+                               + tgNewCount + " stackTraces.size()=" + stackTraces.size());
+        }
+        System.out.println("Initial set of enumerated threads:");
+        for (int i = 0; i < tgNewCount; i++) {
+            System.out.println(" - Thread: " + tgThreads[i].getName());
         }
 
-        Map<Thread, StackTraceElement[]> stackTraces = Thread.getAllStackTraces();
-
+        // Get Threads from MXBean.  Retry to ensure count and id count match.
         ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();
-        int threadCount = threadBean.getThreadCount();
-        long[] threadIds = threadBean.getAllThreadIds();
+        int threadCountBean = 0;
+        long[] threadIdsBean = null;
+        do {
+            System.out.println("Gathering Thread info from MXBean...");
+            threadCountBean = threadBean.getThreadCount();
+            threadIdsBean = threadBean.getAllThreadIds();
+        } while (threadCountBean != threadIdsBean.length);
 
-        System.out.println("ThreadGroup: " + activeCount + " active thread(s)");
-        System.out.println("Thread: " + stackTraces.size() + " stack trace(s) returned");
-        System.out.println("ThreadMXBean: " + threadCount + " live threads(s)");
-        System.out.println("ThreadMXBean: " + threadIds.length + " thread Id(s)");
+        System.out.println("ThreadGroup:              " + tgActiveCount + " active thread(s)");
+        System.out.println("Thread.getAllStackTraces: " + stackTraces.size() + " stack trace(s) returned");
+        System.out.println("ThreadMXBean:             " + threadCountBean + " live threads(s)");
+        System.out.println("ThreadMXBean:             " + threadIdsBean.length + " thread Id(s)");
+
+        if (threadIdsBean.length > tgActiveCount) {
+            // Find the new Threads: some Thead names are permitted to appear: ignore them.
+            Set<Long> seenTids = new TreeSet<>();
+            for (Thread t : stackTraces.keySet()) {
+                if (t != null) {
+                    seenTids.add(t.getId());
+                }
+            }
+            for (long tid : threadIdsBean) {
+                if (!seenTids.contains(tid)) {
+                    // New Thread from MBean, compared to Thread Group:
+                    ThreadInfo threadInfo = threadBean.getThreadInfo(tid);
+                    if (threadInfo != null && isPermittedNewThread(threadInfo.getThreadName())) {
+                        System.out.print("New thread permitted: " + threadInfo);
+                        threadCountBean--;
+                    }
+                }
+            }
+        }
 
         // check results are consistent
         boolean failed = false;
-        if (activeCount != stackTraces.size()) failed = true;
-        if (activeCount != threadCount) failed = true;
-        if (activeCount != threadIds.length) failed = true;
+        if (tgActiveCount != stackTraces.size()) failed = true;
+        if (tgActiveCount != threadCountBean) failed = true;
+        // We know threadCountBean == threadIdsBean.length
 
         if (failed) {
-            System.out.println("Set of stack-traced threads:");
+            System.out.println("Failed.");
+            System.out.println("Set of Threads from getAllStackTraces:");
             for (Thread t : stackTraces.keySet()) {
                 System.out.println(" - Thread: " +
                                    (t != null ? t.getName() : "null!"));
             }
+            System.out.println("Set of Thread IDs from MXBean:");
+            for (long tid : threadIdsBean) {
+                System.out.print(tid + " ");
+                ThreadInfo threadInfo = threadBean.getThreadInfo(tid);
+                System.out.println(threadInfo != null ? threadInfo.getThreadName() : "");
+            }
             throw new RuntimeException("inconsistent results");
         }
     }