First try of removing LockingMode

src/hotspot/share/prims/whitebox.cpp

@@ -85,6 +85,7 @@
 #include "runtime/javaCalls.hpp"
 #include "runtime/javaThread.inline.hpp"
 #include "runtime/jniHandles.inline.hpp"
+#include "runtime/lightweightSynchronizer.hpp"
 #include "runtime/lockStack.hpp"
 #include "runtime/os.hpp"
 #include "runtime/stackFrameStream.inline.hpp"
@@ -1902,6 +1903,20 @@ WB_ENTRY(jboolean, WB_IsMonitorInflated(JNIEnv* env, jobject wb, jobject obj))
   return (jboolean) obj_oop->mark().has_monitor();
 WB_END
 
+WB_ENTRY(void, WB_ForceInflateMonitorLockedObject(JNIEnv* env, jobject wb, jobject obj))
+  oop obj_oop = JNIHandles::resolve(obj);
+  if (obj_oop->mark().has_monitor()) {
+    return; // Already inflated
+  }
+  ObjectSynchronizer::InflateCause cause = ObjectSynchronizer::InflateCause::inflate_cause_vm_internal;
+  JavaThread* current = JavaThread::current();
+  if (LockingMode == LM_LIGHTWEIGHT) {
+    LightweightSynchronizer::inflate_fast_locked_object(obj_oop, cause, current, current);
+  } else {
+    ObjectSynchronizer::inflate(current, obj_oop, cause);
+  }
+WB_END
+
 WB_ENTRY(jboolean, WB_IsAsanEnabled(JNIEnv* env))
   return (jboolean) WhiteBox::is_asan_enabled();
 WB_END
@@ -2906,6 +2921,7 @@ static JNINativeMethod methods[] = {
                                                       (void*)&WB_AddModuleExportsToAll },
   {CC"deflateIdleMonitors", CC"()Z",                  (void*)&WB_DeflateIdleMonitors },
   {CC"isMonitorInflated0", CC"(Ljava/lang/Object;)Z", (void*)&WB_IsMonitorInflated  },
+  {CC"forceInflateMonitorLockedObject0", CC"(Ljava/lang/Object;)V", (void*)&WB_ForceInflateMonitorLockedObject },
   {CC"isAsanEnabled", CC"()Z",                        (void*)&WB_IsAsanEnabled },
   {CC"isUbsanEnabled", CC"()Z",                       (void*)&WB_IsUbsanEnabled },
   {CC"getInUseMonitorCount", CC"()J", (void*)&WB_getInUseMonitorCount  },

src/hotspot/share/runtime/arguments.cpp

@@ -1836,7 +1836,7 @@ bool Arguments::check_vm_args_consistency() {
 
 #ifndef _LP64
   if (LockingMode == LM_LEGACY) {
-    FLAG_SET_CMDLINE(LockingMode, LM_LIGHTWEIGHT);
+    LockingMode = LM_LIGHTWEIGHT;
     // Self-forwarding in bit 3 of the mark-word conflicts
     // with 4-byte-aligned stack-locks.
     warning("Legacy locking not supported on this platform");

src/hotspot/share/runtime/globals.hpp

@@ -1953,13 +1953,6 @@ const int ObjectAlignmentInBytes = 8;
              "Mark all threads after a safepoint, and clear on a modify "   \
              "fence. Add cleanliness checks.")                              \
                                                                             \
-  product(int, LockingMode, LM_LIGHTWEIGHT,                                 \
-          "(Deprecated) Select locking mode: "                              \
-          "0: (Deprecated) monitors only (LM_MONITOR), "                    \
-          "1: (Deprecated) monitors & legacy stack-locking (LM_LEGACY), "   \
-          "2: monitors & new lightweight locking (LM_LIGHTWEIGHT, default)") \
-          range(0, 2)                                                       \
-                                                                            \
   product(bool, UseObjectMonitorTable, false, DIAGNOSTIC,                   \
           "With Lightweight Locking mode, use a table to record inflated "  \
           "monitors rather than the first word of the object.")             \

src/hotspot/share/utilities/globalDefinitions.cpp

@@ -56,6 +56,8 @@ int LogMinObjAlignmentInBytes  = -1;
 // Oop encoding heap max
 uint64_t OopEncodingHeapMax = 0;
 
+int LockingMode = LM_LIGHTWEIGHT;
+
 // Something to help porters sleep at night
 
 #ifdef ASSERT

src/hotspot/share/utilities/globalDefinitions.hpp

@@ -1009,6 +1009,8 @@ enum LockingMode {
   LM_LIGHTWEIGHT = 2
 };
 
+extern int LockingMode;
+
 //----------------------------------------------------------------------------------------------------
 // Special constants for debugging
 

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

@@ -222,29 +222,18 @@ private JavaThread owningThreadFromMonitor(Address o) {
 
     public JavaThread owningThreadFromMonitor(ObjectMonitor monitor) {
         if (monitor.isOwnedAnonymous()) {
-            if (VM.getVM().getCommandLineFlag("LockingMode").getInt() == LockingMode.getLightweight()) {
-                OopHandle object = monitor.object();
-                for (int i = 0; i < getNumberOfThreads(); i++) {
-                    JavaThread thread = getJavaThreadAt(i);
-                    if (thread.isLockOwned(object)) {
-                        return thread;
-                     }
-                }
-                // We should have found the owner, however, as the VM could be in any state, including the middle
-                // of performing GC, it is not always possible to do so. Just return null if we can't locate it.
-                System.out.println("Warning: We failed to find a thread that owns an anonymous lock. This is likely");
-                System.out.println("due to the JVM currently running a GC. Locking information may not be accurate.");
-                return null;
-            } else {
-                assert(VM.getVM().getCommandLineFlag("LockingMode").getInt() == LockingMode.getLegacy());
-                Address o = (Address)monitor.stackLocker();
-                for (int i = 0; i < getNumberOfThreads(); i++) {
-                    JavaThread thread = getJavaThreadAt(i);
-                    if (thread.isLockOwned(o))
-                        return thread;
-                }
-                return null;
+            OopHandle object = monitor.object();
+            for (int i = 0; i < getNumberOfThreads(); i++) {
+                JavaThread thread = getJavaThreadAt(i);
+                if (thread.isLockOwned(object)) {
+                    return thread;
+                 }
             }
+            // We should have found the owner, however, as the VM could be in any state, including the middle
+            // of performing GC, it is not always possible to do so. Just return null if we can't locate it.
+            System.out.println("Warning: We failed to find a thread that owns an anonymous lock. This is likely");
+            System.out.println("due to the JVM currently running a GC. Locking information may not be accurate.");
+            return null;
         } else {
             return owningThreadFromMonitor(monitor.owner());
         }

test/hotspot/jtreg/compiler/locks/TestSynchronizeWithEmptyBlock.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2024, 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
@@ -26,9 +26,6 @@
  * @bug 8337660
  * @summary Test that C2 does not remove blocks with BoxLock nodes that are
  *          otherwise empty.
- * @run main/othervm -Xbatch -XX:LockingMode=1
- *                   -XX:CompileOnly=compiler.locks.TestSynchronizeWithEmptyBlock::*
- *                   compiler.locks.TestSynchronizeWithEmptyBlock
  * @run main/othervm -Xbatch
  *                   -XX:CompileOnly=compiler.locks.TestSynchronizeWithEmptyBlock::*
  *                   compiler.locks.TestSynchronizeWithEmptyBlock

test/hotspot/jtreg/gtest/LockStackGtests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 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
@@ -23,10 +23,10 @@
  */
 
 /* @test
- * @summary Run LockStack gtests with LockingMode=2
+ * @summary Run LockStack gtests
  * @library /test/lib
  * @modules java.base/jdk.internal.misc
  *          java.xml
  * @requires vm.flagless
- * @run main/native GTestWrapper --gtest_filter=LockStackTest* -XX:LockingMode=2
+ * @run main/native GTestWrapper --gtest_filter=LockStackTest*
  */

test/hotspot/jtreg/runtime/Monitor/ConcurrentDeflation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 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
@@ -24,6 +24,7 @@
 import jdk.test.lib.process.OutputAnalyzer;
 import jdk.test.lib.Platform;
 import jdk.test.lib.process.ProcessTools;
+import jdk.test.whitebox.WhiteBox;
 
 import java.lang.management.ManagementFactory;
 import java.lang.management.ThreadInfo;
@@ -33,11 +34,14 @@
  * @test
  * @bug 8318757
  * @summary Test concurrent monitor deflation by MonitorDeflationThread and thread dumping
- * @library /test/lib
- * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:GuaranteedAsyncDeflationInterval=2000 -XX:LockingMode=0 ConcurrentDeflation
+ * @library /test/lib /
+ * @build jdk.test.whitebox.WhiteBox
+ * @run driver jdk.test.lib.helpers.ClassFileInstaller jdk.test.whitebox.WhiteBox
+ * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:GuaranteedAsyncDeflationInterval=2000 -XX:+WhiteBoxAPI ConcurrentDeflation
  */
 
 public class ConcurrentDeflation {
+    static final WhiteBox WB = WhiteBox.getWhiteBox();
     public static final long TOTAL_RUN_TIME_NS = 10_000_000_000L;
     public static Object[] monitors = new Object[1000];
     public static int monitorCount;
@@ -73,6 +77,7 @@ static private void createMonitors() {
             index = index++ % 1000;
             monitors[index] = new Object();
             synchronized (monitors[index]) {
+                WB.forceInflateMonitorLockedObject(monitors[index]);
                 monitorCount++;
             }
         }

test/hotspot/jtreg/runtime/Monitor/StressWrapper_TestRecursiveLocking_36M.java

@@ -33,21 +33,6 @@
  * @run main/othervm/timeout=240 -Xbootclasspath/a:.
  *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
  *     -Xint
- *     -XX:LockingMode=0
- *     -Xms256m -Xmx256m
- *     TestRecursiveLocking 120 1
- *
- * @run main/othervm/timeout=240 -Xbootclasspath/a:.
- *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
- *     -Xint
- *     -XX:LockingMode=1
- *     -Xms256m -Xmx256m
- *     TestRecursiveLocking 120 1
- *
- * @run main/othervm/timeout=240 -Xbootclasspath/a:.
- *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
- *     -Xint
- *     -XX:LockingMode=2
  *     -Xms256m -Xmx256m
  *     TestRecursiveLocking 120 1
  */
@@ -63,21 +48,6 @@
  * @run main/othervm/timeout=240 -Xbootclasspath/a:.
  *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
  *     -Xint
- *     -XX:LockingMode=0
- *     -Xms256m -Xmx256m
- *     TestRecursiveLocking 120 2
- *
- * @run main/othervm/timeout=240 -Xbootclasspath/a:.
- *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
- *     -Xint
- *     -XX:LockingMode=1
- *     -Xms256m -Xmx256m
- *     TestRecursiveLocking 120 2
- *
- * @run main/othervm/timeout=240 -Xbootclasspath/a:.
- *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
- *     -Xint
- *     -XX:LockingMode=2
  *     -Xms256m -Xmx256m
  *     TestRecursiveLocking 120 2
  */
@@ -94,21 +64,6 @@
  * @run main/othervm/timeout=240 -Xbootclasspath/a:.
  *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
  *     -XX:TieredStopAtLevel=1
- *     -XX:LockingMode=0
- *     -Xms256m -Xmx256m
- *     TestRecursiveLocking 120 1
- *
- * @run main/othervm/timeout=240 -Xbootclasspath/a:.
- *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
- *     -XX:TieredStopAtLevel=1
- *     -XX:LockingMode=1
- *     -Xms256m -Xmx256m
- *     TestRecursiveLocking 120 1
- *
- * @run main/othervm/timeout=240 -Xbootclasspath/a:.
- *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
- *     -XX:TieredStopAtLevel=1
- *     -XX:LockingMode=2
  *     -Xms256m -Xmx256m
  *     TestRecursiveLocking 120 1
  */
@@ -125,21 +80,6 @@
  * @run main/othervm/timeout=240 -Xbootclasspath/a:.
  *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
  *     -XX:TieredStopAtLevel=1
- *     -XX:LockingMode=0
- *     -Xms256m -Xmx256m
- *     TestRecursiveLocking 120 2
- *
- * @run main/othervm/timeout=240 -Xbootclasspath/a:.
- *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
- *     -XX:TieredStopAtLevel=1
- *     -XX:LockingMode=1
- *     -Xms256m -Xmx256m
- *     TestRecursiveLocking 120 2
- *
- * @run main/othervm/timeout=240 -Xbootclasspath/a:.
- *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
- *     -XX:TieredStopAtLevel=1
- *     -XX:LockingMode=2
  *     -Xms256m -Xmx256m
  *     TestRecursiveLocking 120 2
  */
@@ -156,21 +96,6 @@
  * @run main/othervm/timeout=240 -Xbootclasspath/a:.
  *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
  *     -XX:-EliminateNestedLocks
- *     -XX:LockingMode=0
- *     -Xms256m -Xmx256m
- *     TestRecursiveLocking 120 1
- *
- * @run main/othervm/timeout=240 -Xbootclasspath/a:.
- *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
- *     -XX:-EliminateNestedLocks
- *     -XX:LockingMode=1
- *     -Xms256m -Xmx256m
- *     TestRecursiveLocking 120 1
- *
- * @run main/othervm/timeout=240 -Xbootclasspath/a:.
- *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
- *     -XX:-EliminateNestedLocks
- *     -XX:LockingMode=2
  *     -Xms256m -Xmx256m
  *     TestRecursiveLocking 120 1
  */
@@ -182,25 +107,10 @@
  * @summary Tests recursive locking in C2 in alternate A and B mode.
  * @library /testlibrary /test/lib
  * @build jdk.test.whitebox.WhiteBox
- *
  * @run driver jdk.test.lib.helpers.ClassFileInstaller jdk.test.whitebox.WhiteBox
- * @run main/othervm/timeout=240 -Xbootclasspath/a:.
- *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
- *     -XX:LockingMode=0
- *     -XX:-EliminateNestedLocks
- *     -Xms256m -Xmx256m
- *     TestRecursiveLocking 120 2
- *
- * @run main/othervm/timeout=240 -Xbootclasspath/a:.
- *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
- *     -XX:LockingMode=1
- *     -XX:-EliminateNestedLocks
- *     -Xms256m -Xmx256m
- *     TestRecursiveLocking 120 2
  *
  * @run main/othervm/timeout=240 -Xbootclasspath/a:.
  *     -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
- *     -XX:LockingMode=2
  *     -XX:-EliminateNestedLocks
  *     -Xms256m -Xmx256m
  *     TestRecursiveLocking 120 2