8312174: missing JVMTI events from vthreads parked during JVMTI attach

Reviewed-by: lmesnik, amenkov

src/hotspot/share/prims/jvmtiEventController.cpp

@@ -309,6 +309,8 @@ public:
   static void clear_to_frame_pop(JvmtiEnvThreadState *env_thread, JvmtiFramePop fpop);
   static void change_field_watch(jvmtiEvent event_type, bool added);
 
+  static bool is_any_thread_filtered_event_enabled_globally();
+  static void recompute_thread_filtered(JvmtiThreadState *state);
   static void thread_started(JavaThread *thread);
   static void thread_ended(JavaThread *thread);
 
@@ -730,6 +732,20 @@ JvmtiEventControllerPrivate::recompute_enabled() {
   EC_TRACE(("[-] # recompute enabled - after " JULONG_FORMAT_X, any_env_thread_enabled));
 }
 
+bool
+JvmtiEventControllerPrivate::is_any_thread_filtered_event_enabled_globally() {
+  julong global_thread_events = JvmtiEventController::_universal_global_event_enabled.get_bits() & THREAD_FILTERED_EVENT_BITS;
+  return global_thread_events != 0L;
+}
+
+void
+JvmtiEventControllerPrivate::recompute_thread_filtered(JvmtiThreadState *state) {
+  assert(Threads::number_of_threads() == 0 || JvmtiThreadState_lock->is_locked(), "sanity check");
+
+  if (is_any_thread_filtered_event_enabled_globally()) {
+    JvmtiEventControllerPrivate::recompute_thread_enabled(state);
+  }
+}
 
 void
 JvmtiEventControllerPrivate::thread_started(JavaThread *thread) {
@@ -739,17 +755,11 @@ JvmtiEventControllerPrivate::thread_started(JavaThread *thread) {
   EC_TRACE(("[%s] # thread started", JvmtiTrace::safe_get_thread_name(thread)));
 
   // if we have any thread filtered events globally enabled, create/update the thread state
-  if ((JvmtiEventController::_universal_global_event_enabled.get_bits() & THREAD_FILTERED_EVENT_BITS) != 0) {
-    MutexLocker mu(JvmtiThreadState_lock);
-    // create the thread state if missing
-    JvmtiThreadState *state = JvmtiThreadState::state_for_while_locked(thread);
-    if (state != nullptr) {    // skip threads with no JVMTI thread state
-      recompute_thread_enabled(state);
-    }
+  if (is_any_thread_filtered_event_enabled_globally()) { // intentionally racy
+    JvmtiThreadState::state_for(thread);
   }
 }
 
-
 void
 JvmtiEventControllerPrivate::thread_ended(JavaThread *thread) {
   // Removes the JvmtiThreadState associated with the specified thread.
@@ -1115,6 +1125,11 @@ JvmtiEventController::change_field_watch(jvmtiEvent event_type, bool added) {
   JvmtiEventControllerPrivate::change_field_watch(event_type, added);
 }
 
+void
+JvmtiEventController::recompute_thread_filtered(JvmtiThreadState *state) {
+  JvmtiEventControllerPrivate::recompute_thread_filtered(state);
+}
+
 void
 JvmtiEventController::thread_started(JavaThread *thread) {
   // operates only on the current thread

src/hotspot/share/prims/jvmtiEventController.hpp

@@ -234,6 +234,7 @@ public:
 
   static void change_field_watch(jvmtiEvent event_type, bool added);
 
+  static void recompute_thread_filtered(JvmtiThreadState *state);
   static void thread_started(JavaThread *thread);
   static void thread_ended(JavaThread *thread);
 

src/hotspot/share/prims/jvmtiExport.cpp

@@ -417,6 +417,15 @@ JvmtiExport::get_jvmti_interface(JavaVM *jvm, void **penv, jint version) {
   }
 }
 
+JvmtiThreadState*
+JvmtiExport::get_jvmti_thread_state(JavaThread *thread) {
+  assert(thread == JavaThread::current(), "must be current thread");
+  if (thread->is_vthread_mounted() && thread->jvmti_thread_state() == nullptr) {
+    JvmtiEventController::thread_started(thread);
+  }
+  return thread->jvmti_thread_state();
+}
+
 void
 JvmtiExport::add_default_read_edges(Handle h_module, TRAPS) {
   if (!Universe::is_module_initialized()) {
@@ -920,7 +929,7 @@ class JvmtiClassFileLoadHookPoster : public StackObj {
     _has_been_modified = false;
 
     assert(!_thread->is_in_any_VTMS_transition(), "CFLH events are not allowed in any VTMS transition");
-    _state = _thread->jvmti_thread_state();
+    _state = JvmtiExport::get_jvmti_thread_state(_thread);
     if (_state != nullptr) {
       _class_being_redefined = _state->get_class_being_redefined();
       _load_kind = _state->get_class_load_kind();
@@ -1212,7 +1221,7 @@ void JvmtiExport::post_raw_breakpoint(JavaThread *thread, Method* method, addres
   HandleMark hm(thread);
   methodHandle mh(thread, method);
 
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -1310,7 +1319,7 @@ void JvmtiExport::at_single_stepping_point(JavaThread *thread, Method* method, a
   methodHandle mh(thread, method);
 
   // update information about current location and post a step event
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -1329,7 +1338,7 @@ void JvmtiExport::at_single_stepping_point(JavaThread *thread, Method* method, a
 
 
 void JvmtiExport::expose_single_stepping(JavaThread *thread) {
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state != nullptr) {
     state->clear_hide_single_stepping();
   }
@@ -1337,7 +1346,7 @@ void JvmtiExport::expose_single_stepping(JavaThread *thread) {
 
 
 bool JvmtiExport::hide_single_stepping(JavaThread *thread) {
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state != nullptr && state->is_enabled(JVMTI_EVENT_SINGLE_STEP)) {
     state->set_hide_single_stepping();
     return true;
@@ -1352,7 +1361,7 @@ void JvmtiExport::post_class_load(JavaThread *thread, Klass* klass) {
   }
   HandleMark hm(thread);
 
-  JvmtiThreadState* state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -1390,7 +1399,7 @@ void JvmtiExport::post_class_prepare(JavaThread *thread, Klass* klass) {
   }
   HandleMark hm(thread);
 
-  JvmtiThreadState* state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -1519,7 +1528,7 @@ void JvmtiExport::post_thread_end(JavaThread *thread) {
   EVT_TRIG_TRACE(JVMTI_EVENT_THREAD_END, ("[%s] Trg Thread End event triggered",
                       JvmtiTrace::safe_get_thread_name(thread)));
 
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -1567,7 +1576,7 @@ void JvmtiExport::post_vthread_start(jobject vthread) {
   EVT_TRIG_TRACE(JVMTI_EVENT_VIRTUAL_THREAD_START, ("[%p] Trg Virtual Thread Start event triggered", vthread));
 
   JavaThread *cur_thread = JavaThread::current();
-  JvmtiThreadState *state = cur_thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(cur_thread);
   if (state == nullptr) {
     return;
   }
@@ -1601,7 +1610,7 @@ void JvmtiExport::post_vthread_end(jobject vthread) {
   EVT_TRIG_TRACE(JVMTI_EVENT_VIRTUAL_THREAD_END, ("[%p] Trg Virtual Thread End event triggered", vthread));
 
   JavaThread *cur_thread = JavaThread::current();
-  JvmtiThreadState *state = cur_thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(cur_thread);
   if (state == nullptr) {
     return;
   }
@@ -1636,7 +1645,7 @@ void JvmtiExport::post_vthread_mount(jobject vthread) {
   HandleMark hm(thread);
   EVT_TRIG_TRACE(EXT_EVENT_VIRTUAL_THREAD_MOUNT, ("[%p] Trg Virtual Thread Mount event triggered", vthread));
 
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -1671,7 +1680,7 @@ void JvmtiExport::post_vthread_unmount(jobject vthread) {
   HandleMark hm(thread);
   EVT_TRIG_TRACE(EXT_EVENT_VIRTUAL_THREAD_UNMOUNT, ("[%p] Trg Virtual Thread Unmount event triggered", vthread));
 
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -1704,7 +1713,7 @@ void JvmtiExport::continuation_yield_cleanup(JavaThread* thread, jint continuati
   }
 
   assert(thread == JavaThread::current(), "must be");
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -1798,7 +1807,7 @@ void JvmtiExport::post_method_entry(JavaThread *thread, Method* method, frame cu
   HandleMark hm(thread);
   methodHandle mh(thread, method);
 
-  JvmtiThreadState* state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr || !state->is_interp_only_mode()) {
     // for any thread that actually wants method entry, interp_only_mode is set
     return;
@@ -1838,7 +1847,7 @@ void JvmtiExport::post_method_exit(JavaThread* thread, Method* method, frame cur
   HandleMark hm(thread);
   methodHandle mh(thread, method);
 
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
 
   if (state == nullptr || !state->is_interp_only_mode()) {
     // for any thread that actually wants method exit, interp_only_mode is set
@@ -1959,7 +1968,7 @@ void JvmtiExport::post_single_step(JavaThread *thread, Method* method, address l
   HandleMark hm(thread);
   methodHandle mh(thread, method);
 
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -2001,7 +2010,7 @@ void JvmtiExport::post_exception_throw(JavaThread *thread, Method* method, addre
   // ensure the stack is sufficiently processed.
   KeepStackGCProcessedMark ksgcpm(thread);
 
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -2089,7 +2098,7 @@ void JvmtiExport::notice_unwind_due_to_exception(JavaThread *thread, Method* met
   methodHandle mh(thread, method);
   Handle exception_handle(thread, exception);
 
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -2205,7 +2214,7 @@ void JvmtiExport::post_field_access(JavaThread *thread, Method* method,
   HandleMark hm(thread);
   methodHandle mh(thread, method);
 
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -2361,7 +2370,7 @@ void JvmtiExport::post_field_modification(JavaThread *thread, Method* method,
   HandleMark hm(thread);
   methodHandle mh(thread, method);
 
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -2603,7 +2612,7 @@ void JvmtiExport::post_dynamic_code_generated_while_holding_locks(const char* na
   // jvmti thread state.
   // The collector and/or state might be null if JvmtiDynamicCodeEventCollector
   // has been initialized while JVMTI_EVENT_DYNAMIC_CODE_GENERATED was disabled.
-  JvmtiThreadState* state = thread->jvmti_thread_state();
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state != nullptr) {
     JvmtiDynamicCodeEventCollector *collector = state->get_dynamic_code_event_collector();
     if (collector != nullptr) {
@@ -2722,7 +2731,10 @@ void JvmtiExport::post_data_dump() {
 
 void JvmtiExport::post_monitor_contended_enter(JavaThread *thread, ObjectMonitor *obj_mntr) {
   oop object = obj_mntr->object();
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  HandleMark hm(thread);
+  Handle h(thread, object);
+
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -2730,9 +2742,6 @@ void JvmtiExport::post_monitor_contended_enter(JavaThread *thread, ObjectMonitor
     return; // no events should be posted if thread is in any VTMS transition
   }
 
-  HandleMark hm(thread);
-  Handle h(thread, object);
-
   EVT_TRIG_TRACE(JVMTI_EVENT_MONITOR_CONTENDED_ENTER,
                      ("[%s] monitor contended enter event triggered",
                       JvmtiTrace::safe_get_thread_name(thread)));
@@ -2755,7 +2764,10 @@ void JvmtiExport::post_monitor_contended_enter(JavaThread *thread, ObjectMonitor
 
 void JvmtiExport::post_monitor_contended_entered(JavaThread *thread, ObjectMonitor *obj_mntr) {
   oop object = obj_mntr->object();
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  HandleMark hm(thread);
+  Handle h(thread, object);
+
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -2763,9 +2775,6 @@ void JvmtiExport::post_monitor_contended_entered(JavaThread *thread, ObjectMonit
     return; // no events should be posted if thread is in any VTMS transition
   }
 
-  HandleMark hm(thread);
-  Handle h(thread, object);
-
   EVT_TRIG_TRACE(JVMTI_EVENT_MONITOR_CONTENDED_ENTERED,
                      ("[%s] monitor contended entered event triggered",
                       JvmtiTrace::safe_get_thread_name(thread)));
@@ -2789,7 +2798,10 @@ void JvmtiExport::post_monitor_contended_entered(JavaThread *thread, ObjectMonit
 
 void JvmtiExport::post_monitor_wait(JavaThread *thread, oop object,
                                           jlong timeout) {
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  HandleMark hm(thread);
+  Handle h(thread, object);
+
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -2797,9 +2809,6 @@ void JvmtiExport::post_monitor_wait(JavaThread *thread, oop object,
     return; // no events should be posted if thread is in any VTMS transition
   }
 
-  HandleMark hm(thread);
-  Handle h(thread, object);
-
   EVT_TRIG_TRACE(JVMTI_EVENT_MONITOR_WAIT,
                      ("[%s] monitor wait event triggered",
                       JvmtiTrace::safe_get_thread_name(thread)));
@@ -2823,7 +2832,10 @@ void JvmtiExport::post_monitor_wait(JavaThread *thread, oop object,
 
 void JvmtiExport::post_monitor_waited(JavaThread *thread, ObjectMonitor *obj_mntr, jboolean timed_out) {
   oop object = obj_mntr->object();
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  HandleMark hm(thread);
+  Handle h(thread, object);
+
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -2831,9 +2843,6 @@ void JvmtiExport::post_monitor_waited(JavaThread *thread, ObjectMonitor *obj_mnt
     return; // no events should be posted if thread is in any VTMS transition
   }
 
-  HandleMark hm(thread);
-  Handle h(thread, object);
-
   EVT_TRIG_TRACE(JVMTI_EVENT_MONITOR_WAITED,
                      ("[%s] monitor waited event triggered",
                       JvmtiTrace::safe_get_thread_name(thread)));
@@ -2886,7 +2895,10 @@ void JvmtiExport::post_vm_object_alloc(JavaThread *thread, oop object) {
 }
 
 void JvmtiExport::post_sampled_object_alloc(JavaThread *thread, oop object) {
-  JvmtiThreadState *state = thread->jvmti_thread_state();
+  HandleMark hm(thread);
+  Handle h(thread, object);
+
+  JvmtiThreadState *state = get_jvmti_thread_state(thread);
   if (state == nullptr) {
     return;
   }
@@ -2896,8 +2908,6 @@ void JvmtiExport::post_sampled_object_alloc(JavaThread *thread, oop object) {
   if (thread->is_in_any_VTMS_transition()) {
     return; // no events should be posted if thread is in any VTMS transition
   }
-  HandleMark hm(thread);
-  Handle h(thread, object);
 
   EVT_TRIG_TRACE(JVMTI_EVENT_SAMPLED_OBJECT_ALLOC,
                  ("[%s] Trg sampled object alloc triggered",

src/hotspot/share/prims/jvmtiExport.hpp

@@ -298,6 +298,11 @@ class JvmtiExport : public AllStatic {
   static void decode_version_values(jint version, int * major, int * minor,
                                     int * micro) NOT_JVMTI_RETURN;
 
+  // If the jvmti_thread_state is absent and any thread filtered event
+  // is enabled globally then it is created.
+  // Otherwise, the thread->jvmti_thread_state() is returned.
+  static JvmtiThreadState* get_jvmti_thread_state(JavaThread *thread);
+
   // single stepping management methods
   static void at_single_stepping_point(JavaThread *thread, Method* method, address location) NOT_JVMTI_RETURN;
   static void expose_single_stepping(JavaThread *thread) NOT_JVMTI_RETURN;

src/hotspot/share/prims/jvmtiThreadState.hpp

@@ -465,9 +465,12 @@ class JvmtiThreadState : public CHeapObj<mtInternal> {
 
   // already holding JvmtiThreadState_lock - retrieve or create JvmtiThreadState
   // Can return null if JavaThread is exiting.
+  // Callers are responsible to call recompute_thread_filtered() to update event bits
+  // if thread-filtered events are enabled globally.
   static JvmtiThreadState *state_for_while_locked(JavaThread *thread, oop thread_oop = nullptr);
   // retrieve or create JvmtiThreadState
   // Can return null if JavaThread is exiting.
+  // Calls recompute_thread_filtered() to update event bits if thread-filtered events are enabled globally.
   static JvmtiThreadState *state_for(JavaThread *thread, Handle thread_handle = Handle());
 
   // JVMTI ForceEarlyReturn support

src/hotspot/share/prims/jvmtiThreadState.inline.hpp

@@ -109,6 +109,7 @@ inline JvmtiThreadState* JvmtiThreadState::state_for(JavaThread *thread, Handle
     MutexLocker mu(JvmtiThreadState_lock);
     // check again with the lock held
     state = state_for_while_locked(thread, thread_handle());
+    JvmtiEventController::recompute_thread_filtered(state);
   } else {
     // Check possible safepoint even if state is non-null.
     // (Note: the thread argument isn't the current thread)

test/hotspot/jtreg/serviceability/jvmti/vthread/VThreadEventTest/VThreadEventTest.java

@@ -0,0 +1,210 @@
+/*
+ * Copyright (c) 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test
+ * @bug 8312174
+ * @summary missing JVMTI events from vthreads parked during JVMTI attach
+ * @requires vm.continuations
+ * @requires vm.jvmti
+ * @requires vm.compMode != "Xcomp"
+ * @run main/othervm/native
+ *     -Djdk.virtualThreadScheduler.parallelism=9
+ *     -Djdk.attach.allowAttachSelf=true -XX:+EnableDynamicAgentLoading VThreadEventTest attach
+ */
+
+import com.sun.tools.attach.VirtualMachine;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.locks.LockSupport;
+import java.util.List;
+import java.util.ArrayList;
+
+/*
+ * The test uses custom implementation of the CountDownLatch class.
+ * The reason is we want the state of tested thread to be predictable.
+ * With java.util.concurrent.CountDownLatch it is not clear what thread state is expected.
+ */
+class CountDownLatch {
+    private int count = 0;
+
+    CountDownLatch(int count) {
+        this.count = count;
+    }
+
+    public synchronized void countDown() {
+        count--;
+        notify();
+    }
+
+    public synchronized void await() throws InterruptedException {
+        while (count > 0) {
+            wait(1);
+        }
+    }
+}
+
+public class VThreadEventTest {
+    static final int TCNT1 = 10;
+    static final int TCNT2 = 4;
+    static final int TCNT3 = 4;
+    static final int THREAD_CNT = TCNT1 + TCNT2 + TCNT3;
+
+    private static void log(String msg) { System.out.println(msg); }
+
+    private static native int threadEndCount();
+    private static native int threadMountCount();
+    private static native int threadUnmountCount();
+
+    private static volatile boolean attached;
+    private static boolean failed;
+    private static List<Thread> test1Threads = new ArrayList(TCNT1);
+
+    private static CountDownLatch ready0 = new CountDownLatch(THREAD_CNT);
+    private static CountDownLatch ready1 = new CountDownLatch(TCNT1);
+    private static CountDownLatch ready2 = new CountDownLatch(THREAD_CNT);
+    private static CountDownLatch mready = new CountDownLatch(1);
+
+    private static void await(CountDownLatch dumpedLatch) {
+        try {
+            dumpedLatch.await();
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    // The test1 vthreads are kept unmounted until interrupted after agent attach.
+    static final Runnable test1 = () -> {
+        synchronized (test1Threads) {
+            test1Threads.add(Thread.currentThread());
+        }
+        log("test1 vthread started");
+        ready0.countDown();
+        await(mready);
+        ready1.countDown(); // to guaranty state is not State.WAITING after await(mready)
+        try {
+            Thread.sleep(20000); // big timeout to keep unmounted until interrupted
+        } catch (InterruptedException ex) {
+            // it is expected, ignore
+        }
+        ready2.countDown();
+    };
+
+    // The test2 vthreads are kept mounted until agent attach.
+    static final Runnable test2 = () -> {
+        log("test2 vthread started");
+        ready0.countDown();
+        await(mready);
+        while (!attached) {
+            // keep mounted
+        }
+        ready2.countDown();
+    };
+
+    // The test3 vthreads are kept mounted until agent attach.
+    static final Runnable test3 = () -> {
+        log("test3 vthread started");
+        ready0.countDown();
+        await(mready);
+        while (!attached) {
+            // keep mounted
+        }
+        LockSupport.parkNanos(10_000_000L); // will cause extra mount and unmount
+        ready2.countDown();
+    };
+
+    public static void main(String[] args) throws Exception {
+        if (Runtime.getRuntime().availableProcessors() < 8) {
+            log("WARNING: test expects at least 8 processors.");
+        }
+        try (ExecutorService executorService = Executors.newVirtualThreadPerTaskExecutor()) {
+            for (int i = 0; i < TCNT1; i++) {
+                executorService.execute(test1);
+            }
+            for (int i = 0; i < TCNT2; i++) {
+                executorService.execute(test2);
+            }
+            for (int i = 0; i < TCNT3; i++) {
+                executorService.execute(test3);
+            }
+            await(ready0);
+            mready.countDown();
+            await(ready1); // to guaranty state is not State.WAITING after await(mready) in test1()
+            // wait for test1 threads to reach WAITING state in sleep()
+            for (Thread t : test1Threads) {
+                Thread.State state = t.getState();
+                log("DBG: state: " + state);
+                while (state != Thread.State.WAITING) {
+                    Thread.sleep(10);
+                    state = t.getState();
+                    log("DBG: state: " + state);
+                }
+            }
+
+            VirtualMachine vm = VirtualMachine.attach(String.valueOf(ProcessHandle.current().pid()));
+            vm.loadAgentLibrary("VThreadEventTest");
+            Thread.sleep(200); // to allow the agent to get ready
+
+            attached = true;
+            for (Thread t : test1Threads) {
+                 t.interrupt();
+            }
+            ready2.await();
+        }
+        // wait until all VirtualThreadEnd events have been sent
+        for (int sleepNo = 1; threadEndCount() < THREAD_CNT; sleepNo++) {
+            Thread.sleep(100);
+            if (sleepNo % 100 == 0) { // 10 sec period of waiting
+                log("main: waited seconds: " + sleepNo/10);
+            }
+        }
+        int threadEndCnt = threadEndCount();
+        int threadMountCnt = threadMountCount();
+        int threadUnmountCnt = threadUnmountCount();
+        int threadEndExp = THREAD_CNT;
+        int threadMountExp = THREAD_CNT - TCNT2;
+        int threadUnmountExp = THREAD_CNT + TCNT3;
+
+        log("ThreadEnd cnt: "     + threadEndCnt     + " (expected: " + threadEndExp + ")");
+        log("ThreadMount cnt: "   + threadMountCnt   + " (expected: " + threadMountExp + ")");
+        log("ThreadUnmount cnt: " + threadUnmountCnt + " (expected: " + threadUnmountExp + ")");
+
+        if (threadEndCnt != threadEndExp) {
+            log("FAILED: unexpected count of ThreadEnd events");
+            failed = true;
+        }
+        if (threadMountCnt != threadMountExp) {
+            log("FAILED: unexpected count of ThreadMount events");
+            failed = true;
+        }
+        if (threadUnmountCnt != threadUnmountExp) {
+            log("FAILED: unexpected count of ThreadUnmount events");
+            failed = true;
+        }
+        if (failed) {
+            throw new RuntimeException("FAILED: event count is wrong");
+        }
+    }
+
+}
+

test/hotspot/jtreg/serviceability/jvmti/vthread/VThreadEventTest/libVThreadEventTest.cpp

@@ -0,0 +1,104 @@
+/*
+ * Copyright (c) 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#include <cstring>
+#include <jvmti.h>
+#include <atomic>
+#include "jvmti_common.h"
+
+extern "C" {
+
+static jvmtiEnv *jvmti = nullptr;
+static std::atomic<int> thread_end_cnt(0);
+static std::atomic<int> thread_unmount_cnt(0);
+static std::atomic<int> thread_mount_cnt(0);
+
+void JNICALL VirtualThreadEnd(jvmtiEnv *jvmti, JNIEnv* jni, jthread vthread) {
+  thread_end_cnt++;
+}
+
+void JNICALL VirtualThreadMount(jvmtiEnv* jvmti, ...) {
+  thread_mount_cnt++;
+}
+
+void JNICALL VirtualThreadUnmount(jvmtiEnv* jvmti, ...) {
+  thread_unmount_cnt++;
+}
+
+JNIEXPORT jint JNICALL
+Java_VThreadEventTest_threadEndCount(JNIEnv* jni, jclass clazz) {
+  return thread_end_cnt;
+}
+
+JNIEXPORT jint JNICALL
+Java_VThreadEventTest_threadMountCount(JNIEnv* jni, jclass clazz) {
+  return thread_mount_cnt;
+}
+
+JNIEXPORT jint JNICALL
+Java_VThreadEventTest_threadUnmountCount(JNIEnv* jni, jclass clazz) {
+  return thread_unmount_cnt;
+}
+
+JNIEXPORT jint JNICALL
+Agent_OnAttach(JavaVM *vm, char *options, void *reserved) {
+  jvmtiEventCallbacks callbacks;
+  jvmtiCapabilities caps;
+  jvmtiError err;
+
+  LOG("Agent_OnAttach started\n");
+  if (vm->GetEnv(reinterpret_cast<void **>(&jvmti), JVMTI_VERSION) != JNI_OK || !jvmti) {
+    LOG("Could not initialize JVMTI env\n");
+    return JNI_ERR;
+  }
+  memset(&caps, 0, sizeof(caps));
+  caps.can_support_virtual_threads = 1;
+  check_jvmti_error(jvmti->AddCapabilities(&caps), "AddCapabilities");
+
+  memset(&callbacks, 0, sizeof(callbacks));
+  callbacks.VirtualThreadEnd = &VirtualThreadEnd;
+
+  err = jvmti->SetEventCallbacks(&callbacks, (jint)sizeof(callbacks));
+  check_jvmti_error(err, "SetEventCallbacks");
+
+  err = set_ext_event_callback(jvmti, "VirtualThreadMount", VirtualThreadMount);
+  check_jvmti_error(err, "SetExtEventCallback for VirtualThreadMount");
+
+  err = set_ext_event_callback(jvmti, "VirtualThreadUnmount", VirtualThreadUnmount);
+  check_jvmti_error(err, "SetExtEventCallback for VirtualThreadUnmount");
+
+  err = jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_VIRTUAL_THREAD_END, nullptr);
+  check_jvmti_error(err, "SetEventNotificationMode for VirtualThreadEnd");
+
+  err = jvmti->SetEventNotificationMode(JVMTI_ENABLE, EXT_EVENT_VIRTUAL_THREAD_MOUNT, nullptr);
+  check_jvmti_error(err, "SetEventNotificationMode for VirtualThreadMount");
+
+  err = jvmti->SetEventNotificationMode(JVMTI_ENABLE, EXT_EVENT_VIRTUAL_THREAD_UNMOUNT, nullptr);
+  check_jvmti_error(err, "SetEventNotificationMode for VirtualThreadUnmount");
+
+  LOG("vthread events enabled\n");
+  return JVMTI_ERROR_NONE;
+}
+
+} // extern "C"
+

test/lib/jdk/test/lib/jvmti/jvmti_common.h

@@ -128,6 +128,13 @@ fatal(JNIEnv* jni, const char* msg) {
   jni->FatalError(msg);
 }
 
+static void
+check_jvmti_error(jvmtiError err, const char* msg) {
+  if (err != JVMTI_ERROR_NONE) {
+    LOG("check_jvmti_error: JVMTI function returned error: %s: %s(%d)\n", msg, TranslateError(err), err);
+    abort();
+  }
+}
 
 static void
 check_jvmti_status(JNIEnv* jni, jvmtiError err, const char* msg) {