src/hotspot/share/services/threadService.cpp

rev 57232 : v2.00 -> v2.08 (CR8/v2.08/11-for-jdk14) patches combined into one; merge with jdk-14+25 snapshot; merge with jdk-14+26 snapshot.
rev 57233 : See CR8-to-CR9-changes; merge with 8230876.patch (2019.11.15); merge with jdk-14+25 snapshot; fuzzy merge with jdk-14+26 snapshot.

*** 206,225 ****
  // FIXME: JVMTI should call this function
  Handle ThreadService::get_current_contended_monitor(JavaThread* thread) {
    assert(thread != NULL, "should be non-NULL");
    debug_only(Thread::check_for_dangling_thread_pointer(thread);)
  
    ObjectMonitorHandle omh;
    ObjectMonitor *wait_obj = thread->current_waiting_monitor(&omh);
  
    oop obj = NULL;
    if (wait_obj != NULL) {
      // thread is doing an Object.wait() call
      obj = (oop) wait_obj->object();
      assert(obj != NULL, "Object.wait() should have an object");
    } else {
-     ObjectMonitorHandle omh;
      ObjectMonitor *enter_obj = thread->current_pending_monitor(&omh);
      if (enter_obj != NULL) {
        // thread is trying to enter() an ObjectMonitor.
        obj = (oop) enter_obj->object();
        assert(obj != NULL, "ObjectMonitor should have an associated object!");
--- 206,228 ----
  // FIXME: JVMTI should call this function
  Handle ThreadService::get_current_contended_monitor(JavaThread* thread) {
    assert(thread != NULL, "should be non-NULL");
    debug_only(Thread::check_for_dangling_thread_pointer(thread);)
  
+   // This function can be called on a target JavaThread that is not
+   // the caller and we are not at a safepoint. This ObjectMonitorHandle
+   // keeps the ObjectMonitor from being async deflated so the object
+   // reference we fetch remains non-NULL.
    ObjectMonitorHandle omh;
    ObjectMonitor *wait_obj = thread->current_waiting_monitor(&omh);
  
    oop obj = NULL;
    if (wait_obj != NULL) {
      // thread is doing an Object.wait() call
      obj = (oop) wait_obj->object();
      assert(obj != NULL, "Object.wait() should have an object");
    } else {
      ObjectMonitor *enter_obj = thread->current_pending_monitor(&omh);
      if (enter_obj != NULL) {
        // thread is trying to enter() an ObjectMonitor.
        obj = (oop) enter_obj->object();
        assert(obj != NULL, "ObjectMonitor should have an associated object!");
*** 362,371 ****
--- 365,376 ----
  DeadlockCycle* ThreadService::find_deadlocks_at_safepoint(ThreadsList * t_list, bool concurrent_locks) {
    assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
  
    // This code was modified from the original Threads::find_deadlocks code.
    int globalDfn = 0, thisDfn;
+   // This code is called at a safepoint so this ObjectMonitorHandle
+   // is not strictly necessary.
    ObjectMonitorHandle omh;
    ObjectMonitor* waitingToLockMonitor = NULL;
    JvmtiRawMonitor* waitingToLockRawMonitor = NULL;
    oop waitingToLockBlocker = NULL;
    bool blocked_on_monitor = false;
*** 983,992 ****
--- 988,999 ----
    JvmtiRawMonitor* waitingToLockRawMonitor;
    oop waitingToLockBlocker;
    int len = _threads->length();
    for (int i = 0; i < len; i++) {
      currentThread = _threads->at(i);
+     // This code is called at a safepoint so this ObjectMonitorHandle
+     // is not strictly necessary.
      ObjectMonitorHandle omh;
      ObjectMonitor* waitingToLockMonitor = currentThread->current_pending_monitor(&omh);
      waitingToLockRawMonitor = currentThread->current_pending_raw_monitor();
      waitingToLockBlocker = currentThread->current_park_blocker();
      st->cr();