From 5f7432f7b1ca52941b717fd35a929c91fbdd276d Mon Sep 17 00:00:00 2001
From: Serguei Spitsyn <sspitsyn@openjdk.org>
Date: Tue, 26 Mar 2024 02:21:47 +0000
Subject: [PATCH] 8328758: GetCurrentContendedMonitor function should use
 JvmtiHandshake

Reviewed-by: lmesnik, pchilanomate
---
 src/hotspot/share/prims/jvmtiEnv.cpp     | 42 ++++--------------------
 src/hotspot/share/prims/jvmtiEnvBase.cpp | 10 ++++++
 src/hotspot/share/prims/jvmtiEnvBase.hpp | 17 +++++-----
 3 files changed, 25 insertions(+), 44 deletions(-)

diff --git a/src/hotspot/share/prims/jvmtiEnv.cpp b/src/hotspot/share/prims/jvmtiEnv.cpp
index c6ddc501d1a..43f372b3a28 100644
--- a/src/hotspot/share/prims/jvmtiEnv.cpp
+++ b/src/hotspot/share/prims/jvmtiEnv.cpp
@@ -1463,44 +1463,14 @@ JvmtiEnv::GetOwnedMonitorStackDepthInfo(jthread thread, jint* monitor_info_count
 // monitor_ptr - pre-checked for null
 jvmtiError
 JvmtiEnv::GetCurrentContendedMonitor(jthread thread, jobject* monitor_ptr) {
-  JavaThread* calling_thread = JavaThread::current();
-  HandleMark hm(calling_thread);
+  JavaThread* current = JavaThread::current();
 
-  JvmtiVTMSTransitionDisabler disabler(thread);
-  ThreadsListHandle tlh(calling_thread);
+  *monitor_ptr = nullptr;
 
-  JavaThread* java_thread = nullptr;
-  oop thread_oop = nullptr;
-  jvmtiError err = get_threadOop_and_JavaThread(tlh.list(), thread, &java_thread, &thread_oop);
-  if (err != JVMTI_ERROR_NONE) {
-    return err;
-  }
-
-  if (java_lang_VirtualThread::is_instance(thread_oop)) {
-    // There is no monitor info to collect if target virtual thread is unmounted.
-    if (java_thread != nullptr) {
-      GetCurrentContendedMonitorClosure op(calling_thread, this, monitor_ptr, /* is_virtual */ true);
-      Handshake::execute(&op, java_thread);
-      err = op.result();
-    } else {
-      *monitor_ptr = nullptr;
-      if (!JvmtiEnvBase::is_vthread_alive(thread_oop)) {
-        err = JVMTI_ERROR_THREAD_NOT_ALIVE;
-      }
-    }
-    return err;
-  }
-  if (java_thread == calling_thread) {
-    // It is only safe to make a direct call on the current thread.
-    // All other usage needs to use a direct handshake for safety.
-    err = get_current_contended_monitor(calling_thread, java_thread, monitor_ptr, /* is_virtual */ false);
-  } else {
-    // get contended monitor information with handshake
-    GetCurrentContendedMonitorClosure op(calling_thread, this, monitor_ptr, /* is_virtual */ false);
-    Handshake::execute(&op, java_thread);
-    err = op.result();
-  }
-  return err;
+  // get contended monitor information with handshake
+  GetCurrentContendedMonitorClosure op(this, current, monitor_ptr);
+  JvmtiHandshake::execute(&op, thread);
+  return op.result();
 } /* end GetCurrentContendedMonitor */
 
 
diff --git a/src/hotspot/share/prims/jvmtiEnvBase.cpp b/src/hotspot/share/prims/jvmtiEnvBase.cpp
index 44b1acf8043..e06b118d2f3 100644
--- a/src/hotspot/share/prims/jvmtiEnvBase.cpp
+++ b/src/hotspot/share/prims/jvmtiEnvBase.cpp
@@ -2497,6 +2497,16 @@ GetCurrentContendedMonitorClosure::do_thread(Thread *target) {
   }
 }
 
+void
+GetCurrentContendedMonitorClosure::do_vthread(Handle target_h) {
+  if (_target_jt == nullptr) {
+    _result = JVMTI_ERROR_NONE; // target virtual thread is unmounted
+    return;
+  }
+  // mounted virtual thread case
+  do_thread(_target_jt);
+}
+
 void
 GetStackTraceClosure::do_thread(Thread *target) {
   Thread* current = Thread::current();
diff --git a/src/hotspot/share/prims/jvmtiEnvBase.hpp b/src/hotspot/share/prims/jvmtiEnvBase.hpp
index fedd447490a..25e7d5c371b 100644
--- a/src/hotspot/share/prims/jvmtiEnvBase.hpp
+++ b/src/hotspot/share/prims/jvmtiEnvBase.hpp
@@ -593,21 +593,22 @@ public:
 };
 
 // HandshakeClosure to get current contended monitor. It is used for both platform and virtual threads.
-class GetCurrentContendedMonitorClosure : public JvmtiHandshakeClosure {
+class GetCurrentContendedMonitorClosure : public JvmtiUnitedHandshakeClosure {
 private:
-  JavaThread *_calling_thread;
   JvmtiEnv *_env;
+  JavaThread *_calling_thread;
   jobject *_owned_monitor_ptr;
-  bool _is_virtual;
 
 public:
-  GetCurrentContendedMonitorClosure(JavaThread* calling_thread, JvmtiEnv *env, jobject *mon_ptr, bool is_virtual)
-    : JvmtiHandshakeClosure("GetCurrentContendedMonitor"),
-      _calling_thread(calling_thread),
+  GetCurrentContendedMonitorClosure(JvmtiEnv *env,
+                                    JavaThread* calling_thread,
+                                    jobject *owned_monitor_ptr)
+    : JvmtiUnitedHandshakeClosure("GetCurrentContendedMonitor"),
       _env(env),
-      _owned_monitor_ptr(mon_ptr),
-      _is_virtual(is_virtual) {}
+      _calling_thread(calling_thread),
+      _owned_monitor_ptr(owned_monitor_ptr) {}
   void do_thread(Thread *target);
+  void do_vthread(Handle target_h);
 };
 
 // HandshakeClosure to get stack trace.