8370846: Support execution of mlvm testing with test thread factory

Reviewed-by: cjplummer

src/hotspot/cpu/ppc/ppc.ad

@@ -6335,8 +6335,36 @@ instruct loadConD_Ex(regD dst, immD src) %{
 // Prefetch instructions.
 // Must be safe to execute with invalid address (cannot fault).
 
+// Special prefetch versions which use the dcbz instruction.
+instruct prefetch_alloc_zero(indirectMemory mem, iRegLsrc src) %{
+  match(PrefetchAllocation (AddP mem src));
+  predicate(AllocatePrefetchStyle == 3);
+  ins_cost(MEMORY_REF_COST);
+
+  format %{ "PREFETCH $mem, 2, $src \t// Prefetch write-many with zero" %}
+  size(4);
+  ins_encode %{
+    __ dcbz($src$$Register, $mem$$base$$Register);
+  %}
+  ins_pipe(pipe_class_memory);
+%}
+
+instruct prefetch_alloc_zero_no_offset(indirectMemory mem) %{
+  match(PrefetchAllocation mem);
+  predicate(AllocatePrefetchStyle == 3);
+  ins_cost(MEMORY_REF_COST);
+
+  format %{ "PREFETCH $mem, 2 \t// Prefetch write-many with zero" %}
+  size(4);
+  ins_encode %{
+    __ dcbz($mem$$base$$Register);
+  %}
+  ins_pipe(pipe_class_memory);
+%}
+
 instruct prefetch_alloc(indirectMemory mem, iRegLsrc src) %{
   match(PrefetchAllocation (AddP mem src));
+  predicate(AllocatePrefetchStyle != 3);
   ins_cost(MEMORY_REF_COST);
 
   format %{ "PREFETCH $mem, 2, $src \t// Prefetch write-many" %}
@@ -6349,6 +6377,7 @@ instruct prefetch_alloc(indirectMemory mem, iRegLsrc src) %{
 
 instruct prefetch_alloc_no_offset(indirectMemory mem) %{
   match(PrefetchAllocation mem);
+  predicate(AllocatePrefetchStyle != 3);
   ins_cost(MEMORY_REF_COST);
 
   format %{ "PREFETCH $mem, 2 \t// Prefetch write-many" %}

src/hotspot/share/gc/shared/threadLocalAllocBuffer.cpp

@@ -37,6 +37,7 @@
 #include "utilities/copy.hpp"
 
 size_t       ThreadLocalAllocBuffer::_max_size = 0;
+int          ThreadLocalAllocBuffer::_reserve_for_allocation_prefetch = 0;
 unsigned int ThreadLocalAllocBuffer::_target_refills = 0;
 
 ThreadLocalAllocBuffer::ThreadLocalAllocBuffer() :
@@ -224,6 +225,30 @@ void ThreadLocalAllocBuffer::startup_initialization() {
   // abort during VM initialization.
   _target_refills = MAX2(_target_refills, 2U);
 
+#ifdef COMPILER2
+  // If the C2 compiler is present, extra space is needed at the end of
+  // TLABs, otherwise prefetching instructions generated by the C2
+  // compiler will fault (due to accessing memory outside of heap).
+  // The amount of space is the max of the number of lines to
+  // prefetch for array and for instance allocations. (Extra space must be
+  // reserved to accommodate both types of allocations.)
+  //
+  // Only SPARC-specific BIS instructions are known to fault. (Those
+  // instructions are generated if AllocatePrefetchStyle==3 and
+  // AllocatePrefetchInstr==1). To be on the safe side, however,
+  // extra space is reserved for all combinations of
+  // AllocatePrefetchStyle and AllocatePrefetchInstr.
+  //
+  // If the C2 compiler is not present, no space is reserved.
+
+  // +1 for rounding up to next cache line, +1 to be safe
+  if (CompilerConfig::is_c2_or_jvmci_compiler_enabled()) {
+    int lines =  MAX2(AllocatePrefetchLines, AllocateInstancePrefetchLines) + 2;
+    _reserve_for_allocation_prefetch = (AllocatePrefetchDistance + AllocatePrefetchStepSize * lines) /
+                                       (int)HeapWordSize;
+  }
+#endif
+
   // During jvm startup, the main thread is initialized
   // before the heap is initialized.  So reinitialize it now.
   guarantee(Thread::current()->is_Java_thread(), "tlab initialization thread not Java thread");
@@ -429,7 +454,8 @@ void ThreadLocalAllocStats::publish() {
 }
 
 size_t ThreadLocalAllocBuffer::end_reserve() {
-  return CollectedHeap::lab_alignment_reserve();
+  size_t reserve_size = CollectedHeap::lab_alignment_reserve();
+  return MAX2(reserve_size, (size_t)_reserve_for_allocation_prefetch);
 }
 
 const HeapWord* ThreadLocalAllocBuffer::start_relaxed() const {

src/hotspot/share/gc/shared/threadLocalAllocBuffer.hpp

@@ -58,6 +58,7 @@ private:
   size_t    _allocated_before_last_gc;           // total bytes allocated up until the last gc
 
   static size_t   _max_size;                          // maximum size of any TLAB
+  static int      _reserve_for_allocation_prefetch;   // Reserve at the end of the TLAB
   static unsigned _target_refills;                    // expected number of refills between GCs
 
   unsigned  _number_of_refills;

src/hotspot/share/opto/macro.cpp

@@ -1914,7 +1914,8 @@ Node* PhaseMacroExpand::prefetch_allocation(Node* i_o, Node*& needgc_false,
       transform_later(cache_adr);
       cache_adr = new CastP2XNode(needgc_false, cache_adr);
       transform_later(cache_adr);
-      // Address is aligned to execute prefetch to the beginning of cache line size.
+      // Address is aligned to execute prefetch to the beginning of cache line size
+      // (it is important when BIS instruction is used on SPARC as prefetch).
       Node* mask = _igvn.MakeConX(~(intptr_t)(step_size-1));
       cache_adr = new AndXNode(cache_adr, mask);
       transform_later(cache_adr);

src/hotspot/share/runtime/vmStructs.cpp

@@ -353,6 +353,7 @@
   nonstatic_field(ThreadLocalAllocBuffer,      _pf_top,                                       HeapWord*)                             \
   nonstatic_field(ThreadLocalAllocBuffer,      _desired_size,                                 size_t)                                \
   nonstatic_field(ThreadLocalAllocBuffer,      _refill_waste_limit,                           size_t)                                \
+     static_field(ThreadLocalAllocBuffer,      _reserve_for_allocation_prefetch,              int)                                   \
      static_field(ThreadLocalAllocBuffer,      _target_refills,                               unsigned)                              \
   nonstatic_field(ThreadLocalAllocBuffer,      _number_of_refills,                            unsigned)                              \
   nonstatic_field(ThreadLocalAllocBuffer,      _refill_waste,                                 unsigned)                              \

src/java.base/share/classes/java/lang/reflect/Field.java

@@ -367,7 +367,7 @@ class Field extends AccessibleObject implements Member {
      * @jls 8.3.1 Field Modifiers
      */
     public String toString() {
-        int mod = getModifiers();
+        int mod = getModifiers() & Modifier.fieldModifiers();
         return (((mod == 0) ? "" : (Modifier.toString(mod) + " "))
             + getType().getTypeName() + " "
             + getDeclaringClass().getTypeName() + "."
@@ -400,7 +400,7 @@ class Field extends AccessibleObject implements Member {
      * @jls 8.3.1 Field Modifiers
      */
     public String toGenericString() {
-        int mod = getModifiers();
+        int mod = getModifiers() & Modifier.fieldModifiers();
         Type fieldType = getGenericType();
         return (((mod == 0) ? "" : (Modifier.toString(mod) + " "))
             + fieldType.getTypeName() + " "

src/java.base/share/classes/java/lang/reflect/Parameter.java

@@ -126,7 +126,7 @@ public final class Parameter implements AnnotatedElement {
         final Type type = getParameterizedType();
         final String typename = type.getTypeName();
 
-        sb.append(Modifier.toString(getModifiers()));
+        sb.append(Modifier.toString(getModifiers() & Modifier.parameterModifiers() ));
 
         if(0 != modifiers)
             sb.append(' ');

src/java.base/share/classes/java/util/concurrent/ThreadPoolExecutor.java

@@ -1426,23 +1426,6 @@ public class ThreadPoolExecutor extends AbstractExecutorService {
         }
     }
 
-    // Override without "throws Throwable" for compatibility with subclasses
-    // whose finalize method invokes super.finalize() (as is recommended).
-    // Before JDK 11, finalize() had a non-empty method body.
-
-    /**
-     * @implNote Previous versions of this class had a finalize method
-     * that shut down this executor, but in this version, finalize
-     * does nothing.
-     *
-     * @deprecated Finalization has been deprecated for removal.  See
-     * {@link java.lang.Object#finalize} for background information and details
-     * about migration options.
-     */
-    @Deprecated(since="9", forRemoval=true)
-    @SuppressWarnings("removal")
-    protected void finalize() {}
-
     /**
      * Sets the thread factory used to create new threads.
      *

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

@@ -76,9 +76,10 @@ public class ThreadLocalAllocBuffer extends VMObject {
 
   private long endReserve() {
     long labAlignmentReserve = VM.getVM().getLabAlignmentReserve();
+    long reserveForAllocationPrefetch = VM.getVM().getReserveForAllocationPrefetch();
     long heapWordSize = VM.getVM().getHeapWordSize();
 
-    return labAlignmentReserve * heapWordSize;
+    return Math.max(labAlignmentReserve, reserveForAllocationPrefetch) * heapWordSize;
   }
 
   /** Support for iteration over heap -- not sure how this will

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

@@ -123,6 +123,7 @@ public class VM {
   private int          invocationEntryBCI;
   private ReversePtrs  revPtrs;
   private VMRegImpl    vmregImpl;
+  private int          reserveForAllocationPrefetch;
   private int          labAlignmentReserve;
 
   // System.getProperties from debuggee VM
@@ -446,6 +447,8 @@ public class VM {
     boolType = (CIntegerType) db.lookupType("bool");
 
     Type threadLocalAllocBuffer = db.lookupType("ThreadLocalAllocBuffer");
+    CIntegerField reserveForAllocationPrefetchField = threadLocalAllocBuffer.getCIntegerField("_reserve_for_allocation_prefetch");
+    reserveForAllocationPrefetch = (int)reserveForAllocationPrefetchField.getCInteger(intType);
 
     Type collectedHeap = db.lookupType("CollectedHeap");
     CIntegerField labAlignmentReserveField = collectedHeap.getCIntegerField("_lab_alignment_reserve");
@@ -912,6 +915,10 @@ public class VM {
     return vmInternalInfo;
   }
 
+  public int getReserveForAllocationPrefetch() {
+    return reserveForAllocationPrefetch;
+  }
+
   public int getLabAlignmentReserve() {
     return labAlignmentReserve;
   }

src/jdk.jdwp.agent/share/native/libjdwp/threadControl.c

@@ -170,6 +170,10 @@ setThreadLocalStorage(jthread thread, ThreadNode *node)
             return;
         }
     }
+    if (error == JVMTI_ERROR_WRONG_PHASE && gdata->vmDead && isVThread(thread)) {
+        // Just return. This can happen with vthreads when the vm is exiting.
+        return;
+    }
     if (error != JVMTI_ERROR_NONE) {
         // The jthread object must be valid, so this must be a fatal error.
         EXIT_ERROR(error, "cannot set thread local storage");

test/hotspot/jtreg/vmTestbase/vm/mlvm/share/jdi/JDIBreakpointTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 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
@@ -28,6 +28,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+import jdk.test.lib.thread.TestThreadFactory;
 import nsk.share.jdi.Binder;
 import nsk.share.jdi.Debugee;
 import vm.mlvm.share.Env;
@@ -437,10 +438,22 @@ public abstract class JDIBreakpointTest extends MlvmTest {
         for (StackFrame f : frames) {
             Location l = f.location();
 
+            String sourcePath;
+            try {
+                sourcePath = l.sourcePath();
+            } catch (AbsentInformationException aie) {
+               // Test Thread Factory support has generated methods in MainWrapper class.
+               if (TestThreadFactory.isTestThreadFactorySet()) {
+                   sourcePath = "unknown";
+               } else {
+                   throw aie;
+               }
+            }
+
             buf.append(String.format("#%-4d", frameNum))
                .append(l.method())
                .append("\n        source: ")
-               .append(l.sourcePath())
+               .append(sourcePath)
                .append(":")
                .append(l.lineNumber())
                .append("; bci=")

test/jdk/ProblemList-jvmti-stress-agent.txt

@@ -21,22 +21,6 @@
 # questions.
 #
 
-#############################################################################
-#
-# List of quarantined tests failing with jvmti stress agent in any mode.
-#
-#############################################################################
-
-
-sun/security/ssl/SSLEngineImpl/SSLEngineKeyLimit.java                       8362658 generic-all
-sun/security/ssl/SSLSessionImpl/MultiNSTClient.java                         8362658 generic-all
-sun/security/ssl/SSLSessionImpl/MultiNSTNoSessionCreation.java              8362658 generic-all
-sun/security/ssl/SSLSessionImpl/MultiNSTParallel.java                       8362658 generic-all
-sun/security/ssl/SSLSessionImpl/MultiNSTSequence.java                       8362658 generic-all
-sun/security/ssl/SSLSessionImpl/ResumptionUpdateBoundValues.java            8362658 generic-all
-sun/security/ssl/SSLSocketImpl/SSLSocketKeyLimit.java                       8362658 generic-all
-
-
 # List of tests incompatible with jvmti stress agent or requiring more investigation
 
 com/sun/jdi/EATests.java#id0                                                0000000 generic-all

test/jdk/java/lang/reflect/Modifier/toStringTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 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
@@ -23,36 +23,71 @@
 
 /**
  * @test
- * @bug 4394937 8051382
+ * @bug 4394937 8051382 8373125
  * @summary tests the toString method of reflect.Modifier
  */
 
 import java.lang.reflect.Modifier;
+import static java.lang.reflect.Modifier.*;
 
 public class toStringTest {
 
     static void testString(int test, String expected) {
-        if(!Modifier.toString(test).equals(expected))
-            throw new RuntimeException(test +
-                                          " yields incorrect toString result");
+        String result = Modifier.toString(test);
+        if(!expected.equals(result)) {
+            System.err.println("For input 0x" + Integer.toHexString(test));
+            System.err.println("expected:\t" + expected + "\ngot\t\t" + result);
+
+            throw new RuntimeException();
+        }
     }
 
-    public static void main(String [] argv) {
-        int allMods = Modifier.PUBLIC | Modifier.PROTECTED | Modifier.PRIVATE |
-            Modifier.ABSTRACT | Modifier.STATIC | Modifier.FINAL |
-            Modifier.TRANSIENT | Modifier.VOLATILE | Modifier.SYNCHRONIZED |
-            Modifier.NATIVE | Modifier.STRICT | Modifier.INTERFACE;
+    public static void main(String... argv) {
+        int allMods = PUBLIC    | PROTECTED | PRIVATE |
+                      ABSTRACT  | STATIC    | FINAL |
+                      TRANSIENT | VOLATILE  | SYNCHRONIZED |
+                      NATIVE    | STRICT    | INTERFACE;
 
         String allModsString = "public protected private abstract static " +
             "final transient volatile synchronized native strictfp interface";
 
-        /* zero should have an empty string */
+        final int ALL_ONES = ~0;
+
+        // zero should have an empty string
         testString(0, "");
 
-        /* test to make sure all modifiers print out in the proper order */
+        // test to make sure all modifiers print out in the proper order
         testString(allMods, allModsString);
 
-        /* verify no extraneous modifiers are printed */
-        testString(~0, allModsString);
+        // verify no extraneous modifiers are printed
+        testString(ALL_ONES, allModsString);
+
+        ModifierKindCase[] kindModifiers = {
+            new ModifierKindCase(classModifiers(),
+                                 "public protected private abstract " +
+                                 "static final strictfp"),
+
+            new ModifierKindCase(constructorModifiers(),"public protected private"),
+
+            new ModifierKindCase(fieldModifiers(),
+                                 "public protected private " +
+                                 "static final transient volatile"),
+
+            new ModifierKindCase(interfaceModifiers(),
+                                 "public protected private " +
+                                 "abstract static strictfp"),
+
+            new ModifierKindCase(methodModifiers(),
+                                 "public protected private abstract " +
+                                 "static final synchronized native strictfp"),
+
+            new ModifierKindCase(parameterModifiers(), "final"),
+        };
+
+        for (var modKindCase : kindModifiers) {
+            testString(ALL_ONES & modKindCase.mask(), modKindCase.expected());
+        }
     }
+
+    private record ModifierKindCase(int mask, String expected){}
 }

test/jdk/sun/security/ssl/SSLEngineImpl/SSLEngineKeyLimit.java

@@ -60,7 +60,6 @@ import java.util.Arrays;
 
 import jdk.test.lib.process.ProcessTools;
 import jdk.test.lib.process.OutputAnalyzer;
-import jdk.test.lib.Utils;
 
 public class SSLEngineKeyLimit extends SSLContextTemplate {
 
@@ -119,9 +118,7 @@ public class SSLEngineKeyLimit extends SSLContextTemplate {
                     System.getProperty("test.java.opts"));
 
             ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(
-                    Utils.addTestJavaOpts("SSLEngineKeyLimit", "p", args[1],
-                            args[2]));
-
+                    "SSLEngineKeyLimit", "p", args[1], args[2]);
             OutputAnalyzer output = ProcessTools.executeProcess(pb);
             try {
                 output.shouldContain(String.format(

test/jdk/sun/security/ssl/SSLSessionImpl/MultiNSTClient.java

@@ -37,7 +37,6 @@
  * @run main/othervm MultiNSTClient -Djdk.tls.client.protocols=TLSv1.2 -Djdk.tls.server.enableSessionTicketExtension=true -Djdk.tls.client.enableSessionTicketExtension=true
  */
 
-import jdk.test.lib.Utils;
 import jdk.test.lib.process.OutputAnalyzer;
 import jdk.test.lib.process.ProcessTools;
 
@@ -77,8 +76,7 @@ public class MultiNSTClient {
             System.out.println("test.java.opts: " +
                 System.getProperty("test.java.opts"));
 
-            ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(
-                Utils.addTestJavaOpts("MultiNSTClient", "p"));
+            ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder("MultiNSTClient", "p");
 
             OutputAnalyzer output = ProcessTools.executeProcess(pb);
             boolean pass = true;

test/jdk/sun/security/ssl/SSLSessionImpl/MultiNSTNoSessionCreation.java

@@ -31,7 +31,6 @@
  * @run main/othervm MultiNSTNoSessionCreation -Djdk.tls.client.protocols=TLSv1.2 -Djdk.tls.server.newSessionTicketCount=0
  */
 
-import jdk.test.lib.Utils;
 import jdk.test.lib.process.OutputAnalyzer;
 import jdk.test.lib.process.ProcessTools;
 
@@ -61,7 +60,7 @@ public class MultiNSTNoSessionCreation {
                 System.getProperty("test.java.opts"));
 
             ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(
-                Utils.addTestJavaOpts("MultiNSTNoSessionCreation", "p"));
+                    "MultiNSTNoSessionCreation", "p");
 
             OutputAnalyzer output = ProcessTools.executeProcess(pb);
             try {

test/jdk/sun/security/ssl/SSLSessionImpl/MultiNSTParallel.java

@@ -30,7 +30,6 @@
  * @run main/othervm MultiNSTParallel 10 -Djdk.tls.client.protocols=TLSv1.3
  */
 
-import jdk.test.lib.Utils;
 import jdk.test.lib.process.OutputAnalyzer;
 import jdk.test.lib.process.ProcessTools;
 
@@ -116,8 +115,7 @@ public class MultiNSTParallel {
             System.out.println("test.java.opts: " +
                 System.getProperty("test.java.opts"));
 
-            ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(
-                Utils.addTestJavaOpts("MultiNSTParallel", "p"));
+            ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder("MultiNSTParallel", "p");
 
             OutputAnalyzer output = ProcessTools.executeProcess(pb);
             try {

test/jdk/sun/security/ssl/SSLSessionImpl/MultiNSTSequence.java

@@ -30,7 +30,6 @@
  * @run main/othervm MultiNSTSequence -Djdk.tls.server.newSessionTicketCount=2
  */
 
-import jdk.test.lib.Utils;
 import jdk.test.lib.process.OutputAnalyzer;
 import jdk.test.lib.process.ProcessTools;
 
@@ -69,8 +68,7 @@ public class MultiNSTSequence {
             System.out.println("test.java.opts: " +
                 System.getProperty("test.java.opts"));
 
-            ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(
-                Utils.addTestJavaOpts("MultiNSTSequence", "p"));
+            ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder("MultiNSTSequence", "p");
 
             OutputAnalyzer output = ProcessTools.executeProcess(pb);
             boolean pass = true;

test/jdk/sun/security/ssl/SSLSessionImpl/ResumptionUpdateBoundValues.java

@@ -45,7 +45,6 @@ import javax.net.ssl.SSLSocketFactory;
 
 import jdk.test.lib.process.OutputAnalyzer;
 import jdk.test.lib.process.ProcessTools;
-import jdk.test.lib.Utils;
 
 public class ResumptionUpdateBoundValues extends SSLContextTemplate {
 
@@ -188,7 +187,7 @@ public class ResumptionUpdateBoundValues extends SSLContextTemplate {
                     System.getProperty("test.java.opts"));
 
             ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(
-                    Utils.addTestJavaOpts("ResumptionUpdateBoundValues", "p"));
+                    "ResumptionUpdateBoundValues", "p");
 
             OutputAnalyzer output = ProcessTools.executeProcess(pb);
             try {

test/jdk/sun/security/ssl/SSLSocketImpl/SSLSocketKeyLimit.java

@@ -68,7 +68,6 @@ import java.util.Arrays;
 
 import jdk.test.lib.process.OutputAnalyzer;
 import jdk.test.lib.process.ProcessTools;
-import jdk.test.lib.Utils;
 import jdk.test.lib.hexdump.HexPrinter;
 
 public class SSLSocketKeyLimit {
@@ -135,8 +134,7 @@ public class SSLSocketKeyLimit {
                     System.getProperty("test.java.opts"));
 
             ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(
-                    Utils.addTestJavaOpts("SSLSocketKeyLimit", "p", args[1],
-                            args[2]));
+                    "SSLSocketKeyLimit", "p", args[1], args[2]);
 
             OutputAnalyzer output = ProcessTools.executeProcess(pb);
             try {

test/lib/jdk/test/lib/thread/TestThreadFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 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
@@ -32,8 +32,27 @@ import java.util.concurrent.ThreadFactory;
 
 public class TestThreadFactory {
 
-    private static ThreadFactory threadFactory = "Virtual".equals(System.getProperty("test.thread.factory"))
-            ? virtualThreadFactory() : platformThreadFactory();
+    public enum TestThreadFactoryType {
+        NONE, VIRTUAL
+    }
+
+    private final static TestThreadFactoryType testThreadFactoryType =
+            "Virtual".equals(System.getProperty("test.thread.factory"))
+                    ? TestThreadFactoryType.VIRTUAL
+                    : TestThreadFactoryType.NONE;
+
+    private final static ThreadFactory threadFactory =
+            testThreadFactoryType == TestThreadFactoryType.VIRTUAL
+                    ? virtualThreadFactory()
+                    : platformThreadFactory();
+
+    public static TestThreadFactoryType testThreadFactoryType() {
+        return testThreadFactoryType;
+    }
+
+    public static boolean isTestThreadFactorySet() {
+        return !testThreadFactoryType.equals(TestThreadFactoryType.NONE);
+    }
 
     public static Thread newThread(Runnable task) {
         return threadFactory.newThread(task);