8348347: Cleanup JavaThread subclass support in SA

Reviewed-by: kevinw, sspitsyn

Author: plummercj

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/AttachListenerThread.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2025, 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
@@ -65,8 +65,17 @@ public CompilerThread(Address addr) {
  super(addr);
  }
 
- public boolean isJavaThread() { return false; }
- public boolean isHiddenFromExternalView() { return true; }
- public boolean isCompilerThread() { return true; }
+ @Override
+ public boolean isHiddenFromExternalView() {
+ /*
+ * See JDK-8348317. CompilerThreads are sometimes hidden and sometimes not. They
+ * are not when JVMCI is enabled and a compiler implemented in java is running
+ * on the CompilerThread. This is hard for SA to determine, and not something a customer
+ * is likely to ever run across or care about, so by default all CompilerThreads
+ * are considered to be hidden. However, we allow this behaviour to be overridden
+ * in case the user has a need to make the CompilerThreads visible.
+ */
+ return !Boolean.getBoolean("sun.jvm.hotspot.runtime.CompilerThread.visible");
+ }
 
 }

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/CompilerThread.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2025, 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
@@ -26,11 +26,13 @@
 
 import sun.jvm.hotspot.debugger.Address;
 
-public class StringDedupThread extends JavaThread {
- public StringDedupThread(Address addr) {
+public class HiddenJavaThread extends JavaThread {
+
+ public HiddenJavaThread(Address addr) {
  super(addr);
  }
 
- public boolean isJavaThread() { return false; }
+ @Override
  public boolean isHiddenFromExternalView() { return true; }
+
 }

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/DeoptimizeObjectsALotThread.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2025, 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
@@ -33,13 +33,6 @@
 import sun.jvm.hotspot.utilities.Observable;
 import sun.jvm.hotspot.utilities.Observer;
 
-/** This is an abstract class because there are certain OS- and
- CPU-specific operations (like the setting and getting of the last
- Java frame pointer) which need to be factored out. These
- operations are implemented by, for example,
- SolarisSPARCJavaThread, and the concrete subclasses are
- instantiated by the JavaThreadFactory in the Threads class. */
-
 public class JavaThread extends Thread {
  private static final boolean DEBUG = System.getProperty("sun.jvm.hotspot.runtime.JavaThread.DEBUG") != null;
 
@@ -58,6 +51,7 @@ public class JavaThread extends Thread {
  private static CIntegerField monitorOwnerIDField;
  private static long oopPtrSize;
 
+ // For accessing platform dependent functionality
  private static JavaThreadPDAccess access;
 
  // JavaThreadStates read from underlying process
@@ -133,16 +127,6 @@ void setThreadPDAccess(JavaThreadPDAccess access) {
  this.access = access;
  }
 
- /** NOTE: for convenience, this differs in definition from the underlying VM.
- Only "pure" JavaThreads return true; CompilerThreads,
- JVMDIDebuggerThreads return false.
- FIXME:
- consider encapsulating platform-specific functionality in an
- object instead of using inheritance (which is the primary reason
- we can't traverse CompilerThreads, etc; didn't want to have, for
- example, "SolarisSPARCCompilerThread".) */
- public boolean isJavaThread() { return true; }
-
  public boolean isExiting () {
  return (getTerminated() == EXITING) || isTerminated();
  }

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/StringDedupThread.java renamed to src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/HiddenJavaThread.java

@@ -80,16 +80,7 @@ public long allocatedBytes() {
  }
 
  public boolean isVMThread() { return false; }
- public boolean isJavaThread() { return false; }
- public boolean isCompilerThread() { return false; }
- public boolean isCodeCacheSweeperThread() { return false; }
  public boolean isHiddenFromExternalView() { return false; }
- public boolean isJvmtiAgentThread() { return false; }
- public boolean isWatcherThread() { return false; }
- public boolean isServiceThread() { return false; }
- public boolean isMonitorDeflationThread() { return false; }
- public boolean isAttachListenerThread() { return false; }
- public boolean isDeoptimizeObjectsALotThread() { return false; }
 
  /** Memory operations */
  public void oopsDo(AddressVisitor oopVisitor) {