8242425: JVMTI monitor operations should use Thread-Local Handshakes

Reviewed-by: sspitsyn, dholmes

Author: YaSuenag

src/hotspot/share/prims/jvmtiEnv.cpp

@@ -1200,21 +1200,19 @@ JvmtiEnv::GetThreadInfo(jthread thread, jvmtiThreadInfo* info_ptr) {
 jvmtiError
 JvmtiEnv::GetOwnedMonitorInfo(JavaThread* java_thread, jint* owned_monitor_count_ptr, jobject** owned_monitors_ptr) {
   jvmtiError err = JVMTI_ERROR_NONE;
-  JavaThread* calling_thread = JavaThread::current();
 
   // growable array of jvmti monitors info on the C-heap
   GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors_list =
       new (ResourceObj::C_HEAP, mtInternal) GrowableArray<jvmtiMonitorStackDepthInfo*>(1, true);
 
   // It is only safe to perform the direct operation on the current
-  // thread. All other usage needs to use a vm-safepoint-op for safety.
-  if (java_thread == calling_thread) {
-    err = get_owned_monitors(calling_thread, java_thread, owned_monitors_list);
+  // thread. All other usage needs to use a direct handshake for safety.
+  if (java_thread == JavaThread::current()) {
+    err = get_owned_monitors(java_thread, owned_monitors_list);
   } else {
-    // JVMTI get monitors info at safepoint. Do not require target thread to
-    // be suspended.
-    VM_GetOwnedMonitorInfo op(this, calling_thread, java_thread, owned_monitors_list);
-    VMThread::execute(&op);
+    // get owned monitors info with handshake
+    GetOwnedMonitorInfoClosure op(this, owned_monitors_list);
+    Handshake::execute_direct(&op, java_thread);
     err = op.result();
   }
   jint owned_monitor_count = owned_monitors_list->length();
@@ -1246,21 +1244,19 @@ JvmtiEnv::GetOwnedMonitorInfo(JavaThread* java_thread, jint* owned_monitor_count
 jvmtiError
 JvmtiEnv::GetOwnedMonitorStackDepthInfo(JavaThread* java_thread, jint* monitor_info_count_ptr, jvmtiMonitorStackDepthInfo** monitor_info_ptr) {
   jvmtiError err = JVMTI_ERROR_NONE;
-  JavaThread* calling_thread  = JavaThread::current();
 
   // growable array of jvmti monitors info on the C-heap
   GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors_list =
          new (ResourceObj::C_HEAP, mtInternal) GrowableArray<jvmtiMonitorStackDepthInfo*>(1, true);
 
   // It is only safe to perform the direct operation on the current
-  // thread. All other usage needs to use a vm-safepoint-op for safety.
-  if (java_thread == calling_thread) {
-    err = get_owned_monitors(calling_thread, java_thread, owned_monitors_list);
+  // thread. All other usage needs to use a direct handshake for safety.
+  if (java_thread == JavaThread::current()) {
+    err = get_owned_monitors(java_thread, owned_monitors_list);
   } else {
-    // JVMTI get owned monitors info at safepoint. Do not require target thread to
-    // be suspended.
-    VM_GetOwnedMonitorInfo op(this, calling_thread, java_thread, owned_monitors_list);
-    VMThread::execute(&op);
+    // get owned monitors info with handshake
+    GetOwnedMonitorInfoClosure op(this, owned_monitors_list);
+    Handshake::execute_direct(&op, java_thread);
     err = op.result();
   }
 
@@ -1295,16 +1291,15 @@ JvmtiEnv::GetOwnedMonitorStackDepthInfo(JavaThread* java_thread, jint* monitor_i
 jvmtiError
 JvmtiEnv::GetCurrentContendedMonitor(JavaThread* java_thread, jobject* monitor_ptr) {
   jvmtiError err = JVMTI_ERROR_NONE;
-  JavaThread* calling_thread  = JavaThread::current();
 
   // It is only safe to perform the direct operation on the current
-  // thread. All other usage needs to use a vm-safepoint-op for safety.
-  if (java_thread == calling_thread) {
-    err = get_current_contended_monitor(calling_thread, java_thread, monitor_ptr);
+  // thread. All other usage needs to use a direct handshake for safety.
+  if (java_thread == JavaThread::current()) {
+    err = get_current_contended_monitor(java_thread, monitor_ptr);
   } else {
-    // get contended monitor information at safepoint.
-    VM_GetCurrentContendedMonitor op(this, calling_thread, java_thread, monitor_ptr);
-    VMThread::execute(&op);
+    // get contended monitor information with handshake
+    GetCurrentContendedMonitorClosure op(this, monitor_ptr);
+    Handshake::execute_direct(&op, java_thread);
     err = op.result();
   }
   return err;

src/hotspot/share/prims/jvmtiEnvBase.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2020, 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
@@ -647,13 +647,11 @@ JvmtiEnvBase::count_locked_objects(JavaThread *java_thread, Handle hobj) {
 
 
 jvmtiError
-JvmtiEnvBase::get_current_contended_monitor(JavaThread *calling_thread, JavaThread *java_thread, jobject *monitor_ptr) {
-#ifdef ASSERT
-  uint32_t debug_bits = 0;
-#endif
-  assert((SafepointSynchronize::is_at_safepoint() ||
-          java_thread->is_thread_fully_suspended(false, &debug_bits)),
-         "at safepoint or target thread is suspended");
+JvmtiEnvBase::get_current_contended_monitor(JavaThread *java_thread, jobject *monitor_ptr) {
+  JavaThread *current_jt = JavaThread::current();
+  assert(current_jt == java_thread ||
+         current_jt == java_thread->active_handshaker(),
+         "call by myself or at direct handshake");
   oop obj = NULL;
   ObjectMonitor *mon = java_thread->current_waiting_monitor();
   if (mon == NULL) {
@@ -675,23 +673,21 @@ JvmtiEnvBase::get_current_contended_monitor(JavaThread *calling_thread, JavaThre
     *monitor_ptr = NULL;
   } else {
     HandleMark hm;
-    Handle     hobj(Thread::current(), obj);
-    *monitor_ptr = jni_reference(calling_thread, hobj);
+    Handle     hobj(current_jt, obj);
+    *monitor_ptr = jni_reference(current_jt, hobj);
   }
   return JVMTI_ERROR_NONE;
 }
 
 
 jvmtiError
-JvmtiEnvBase::get_owned_monitors(JavaThread *calling_thread, JavaThread* java_thread,
+JvmtiEnvBase::get_owned_monitors(JavaThread* java_thread,
                                  GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors_list) {
   jvmtiError err = JVMTI_ERROR_NONE;
-#ifdef ASSERT
-  uint32_t debug_bits = 0;
-#endif
-  assert((SafepointSynchronize::is_at_safepoint() ||
-          java_thread->is_thread_fully_suspended(false, &debug_bits)),
-         "at safepoint or target thread is suspended");
+  JavaThread *current_jt = JavaThread::current();
+  assert(current_jt == java_thread ||
+         current_jt == java_thread->active_handshaker(),
+         "call by myself or at direct handshake");
 
   if (java_thread->has_last_Java_frame()) {
     ResourceMark rm;
@@ -703,7 +699,7 @@ JvmtiEnvBase::get_owned_monitors(JavaThread *calling_thread, JavaThread* java_th
          jvf = jvf->java_sender()) {
       if (MaxJavaStackTraceDepth == 0 || depth++ < MaxJavaStackTraceDepth) {  // check for stack too deep
         // add locked objects for this frame into list
-        err = get_locked_objects_in_frame(calling_thread, java_thread, jvf, owned_monitors_list, depth-1);
+        err = get_locked_objects_in_frame(current_jt, java_thread, jvf, owned_monitors_list, depth-1);
         if (err != JVMTI_ERROR_NONE) {
           return err;
         }
@@ -712,7 +708,7 @@ JvmtiEnvBase::get_owned_monitors(JavaThread *calling_thread, JavaThread* java_th
   }
 
   // Get off stack monitors. (e.g. acquired via jni MonitorEnter).
-  JvmtiMonitorClosure jmc(java_thread, calling_thread, owned_monitors_list, this);
+  JvmtiMonitorClosure jmc(java_thread, current_jt, owned_monitors_list, this);
   ObjectSynchronizer::monitors_iterate(&jmc);
   err = jmc.error();
 
@@ -1542,24 +1538,13 @@ VM_SetFramePop::doit() {
 }
 
 void
-VM_GetOwnedMonitorInfo::doit() {
-  _result = JVMTI_ERROR_THREAD_NOT_ALIVE;
-  ThreadsListHandle tlh;
-  if (_java_thread != NULL && tlh.includes(_java_thread)
-      && !_java_thread->is_exiting() && _java_thread->threadObj() != NULL) {
-    _result = ((JvmtiEnvBase *)_env)->get_owned_monitors(_calling_thread, _java_thread,
-                                                          _owned_monitors_list);
-  }
+GetOwnedMonitorInfoClosure::do_thread(Thread *target) {
+  _result = ((JvmtiEnvBase *)_env)->get_owned_monitors((JavaThread *)target, _owned_monitors_list);
 }
 
 void
-VM_GetCurrentContendedMonitor::doit() {
-  _result = JVMTI_ERROR_THREAD_NOT_ALIVE;
-  ThreadsListHandle tlh;
-  if (_java_thread != NULL && tlh.includes(_java_thread)
-      && !_java_thread->is_exiting() && _java_thread->threadObj() != NULL) {
-    _result = ((JvmtiEnvBase *)_env)->get_current_contended_monitor(_calling_thread,_java_thread,_owned_monitor_ptr);
-  }
+GetCurrentContendedMonitorClosure::do_thread(Thread *target) {
+  _result = ((JvmtiEnvBase *)_env)->get_current_contended_monitor((JavaThread *)target, _owned_monitor_ptr);
 }
 
 void

src/hotspot/share/prims/jvmtiEnvBase.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2020, 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
@@ -292,7 +292,8 @@ class JvmtiEnvBase : public CHeapObj<mtInternal> {
   // get a field descriptor for the specified class and field
   static bool get_field_descriptor(Klass* k, jfieldID field, fieldDescriptor* fd);
 
-  // JVMTI API helper functions which are called at safepoint or thread is suspended.
+  // JVMTI API helper functions which are called when target thread is suspended
+  // or at safepoint / thread local handshake.
   jvmtiError get_frame_count(JvmtiThreadState *state, jint *count_ptr);
   jvmtiError get_frame_location(JavaThread* java_thread, jint depth,
                                               jmethodID* method_ptr, jlocation* location_ptr);
@@ -301,11 +302,10 @@ class JvmtiEnvBase : public CHeapObj<mtInternal> {
   jvmtiError get_stack_trace(JavaThread *java_thread,
                                            jint stack_depth, jint max_count,
                                            jvmtiFrameInfo* frame_buffer, jint* count_ptr);
-  jvmtiError get_current_contended_monitor(JavaThread *calling_thread,
-                                                         JavaThread *java_thread,
-                                                         jobject *monitor_ptr);
-  jvmtiError get_owned_monitors(JavaThread *calling_thread, JavaThread* java_thread,
-                          GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors_list);
+  jvmtiError get_current_contended_monitor(JavaThread *java_thread,
+                                           jobject *monitor_ptr);
+  jvmtiError get_owned_monitors(JavaThread* java_thread,
+                                GrowableArray<jvmtiMonitorStackDepthInfo*> *owned_monitors_list);
   jvmtiError check_top_frame(JavaThread* current_thread, JavaThread* java_thread,
                              jvalue value, TosState tos, Handle* ret_ob_h);
   jvmtiError force_early_return(JavaThread* java_thread, jvalue value, TosState tos);
@@ -376,27 +376,21 @@ class VM_SetFramePop : public VM_Operation {
 };
 
 
-// VM operation to get monitor information with stack depth.
-class VM_GetOwnedMonitorInfo : public VM_Operation {
+// HandshakeClosure to get monitor information with stack depth.
+class GetOwnedMonitorInfoClosure : public HandshakeClosure {
 private:
   JvmtiEnv *_env;
-  JavaThread* _calling_thread;
-  JavaThread *_java_thread;
   jvmtiError _result;
   GrowableArray<jvmtiMonitorStackDepthInfo*> *_owned_monitors_list;
 
 public:
-  VM_GetOwnedMonitorInfo(JvmtiEnv* env, JavaThread* calling_thread,
-                                   JavaThread* java_thread,
-                                   GrowableArray<jvmtiMonitorStackDepthInfo*>* owned_monitor_list) {
-    _env = env;
-    _calling_thread = calling_thread;
-    _java_thread = java_thread;
-    _owned_monitors_list = owned_monitor_list;
-    _result = JVMTI_ERROR_NONE;
-  }
-  VMOp_Type type() const { return VMOp_GetOwnedMonitorInfo; }
-  void doit();
+  GetOwnedMonitorInfoClosure(JvmtiEnv* env,
+                             GrowableArray<jvmtiMonitorStackDepthInfo*>* owned_monitor_list)
+    : HandshakeClosure("GetOwnedMonitorInfo"),
+      _env(env),
+      _result(JVMTI_ERROR_NONE),
+      _owned_monitors_list(owned_monitor_list) {}
+  void do_thread(Thread *target);
   jvmtiError result() { return _result; }
 };
 
@@ -425,25 +419,21 @@ class VM_GetObjectMonitorUsage : public VM_Operation {
 
 };
 
-// VM operation to get current contended monitor.
-class VM_GetCurrentContendedMonitor : public VM_Operation {
+// HandshakeClosure to get current contended monitor.
+class GetCurrentContendedMonitorClosure : public HandshakeClosure {
 private:
   JvmtiEnv *_env;
-  JavaThread *_calling_thread;
-  JavaThread *_java_thread;
   jobject *_owned_monitor_ptr;
   jvmtiError _result;
 
 public:
-  VM_GetCurrentContendedMonitor(JvmtiEnv *env, JavaThread *calling_thread, JavaThread *java_thread, jobject *mon_ptr) {
-    _env = env;
-    _calling_thread = calling_thread;
-    _java_thread = java_thread;
-    _owned_monitor_ptr = mon_ptr;
-  }
-  VMOp_Type type() const { return VMOp_GetCurrentContendedMonitor; }
+  GetCurrentContendedMonitorClosure(JvmtiEnv *env, jobject *mon_ptr)
+    : HandshakeClosure("GetCurrentContendedMonitor"),
+      _env(env),
+      _owned_monitor_ptr(mon_ptr),
+      _result(JVMTI_ERROR_THREAD_NOT_ALIVE) {}
   jvmtiError result() { return _result; }
-  void doit();
+  void do_thread(Thread *target);
 };
 
 // VM operation to get stack trace at safepoint.

src/hotspot/share/runtime/vmOperations.hpp

@@ -80,9 +80,7 @@
   template(RedefineClasses)                       \
   template(UpdateForPopTopFrame)                  \
   template(SetFramePop)                           \
-  template(GetOwnedMonitorInfo)                   \
   template(GetObjectMonitorUsage)                 \
-  template(GetCurrentContendedMonitor)            \
   template(GetStackTrace)                         \
   template(GetMultipleStackTraces)                \
   template(GetAllStackTraces)                     \