src/hotspot/share/runtime/vframe.cpp

rev 59077 : 8153224.v2.09b.patch combined with 8153224.v2.10.patch; merge with jdk-15+21.
rev 59078 : eosterlund v2.10 CR: reorganize deflate_monitor_using_JT() to use "early exit" style; dcubed - clarify/fix/rearrange a few comments in deflate_monitor_using_JT(); eosterlund v2.10 CR: simplify install_displaced_markword_in_object() and save_om_ptr(); save_om_ptr()'s call to install_displaced_markword_in_object() can race with the deflater thread's clearing of the object field so handle that; fold 8153224.OMHandle_experiment into 8153224.v2.11.patch; merge with jdk-15+21.

*** 1,7 ****
  /*
!  * Copyright (c) 1997, 2019, 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.
--- 1,7 ----
  /*
!  * Copyright (c) 1997, 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
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.
*** 120,131 ****
    GrowableArray<MonitorInfo*>* mons = monitors();
    GrowableArray<MonitorInfo*>* result = new GrowableArray<MonitorInfo*>(mons->length());
    if (mons->is_empty()) return result;
  
    bool found_first_monitor = false;
!   ObjectMonitor *pending_monitor = thread()->current_pending_monitor();
    ObjectMonitor *waiting_monitor = thread()->current_waiting_monitor();
    oop pending_obj = (pending_monitor != NULL ? (oop) pending_monitor->object() : (oop) NULL);
    oop waiting_obj = (waiting_monitor != NULL ? (oop) waiting_monitor->object() : (oop) NULL);
  
    for (int index = (mons->length()-1); index >= 0; index--) {
      MonitorInfo* monitor = mons->at(index);
--- 120,137 ----
    GrowableArray<MonitorInfo*>* mons = monitors();
    GrowableArray<MonitorInfo*>* result = new GrowableArray<MonitorInfo*>(mons->length());
    if (mons->is_empty()) return result;
  
    bool found_first_monitor = false;
!   // The ObjectMonitor* can't be async deflated since we are either
!   // at a safepoint or the calling thread is operating on itself so
!   // it cannot leave the underlying wait()/enter() call.
    ObjectMonitor *waiting_monitor = thread()->current_waiting_monitor();
+   ObjectMonitor *pending_monitor = NULL;
+   if (waiting_monitor == NULL) {
+     pending_monitor = thread()->current_pending_monitor();
+   }
    oop pending_obj = (pending_monitor != NULL ? (oop) pending_monitor->object() : (oop) NULL);
    oop waiting_obj = (waiting_monitor != NULL ? (oop) waiting_monitor->object() : (oop) NULL);
  
    for (int index = (mons->length()-1); index >= 0; index--) {
      MonitorInfo* monitor = mons->at(index);
*** 229,238 ****
--- 235,246 ----
            // monitor before, then we need to see if we have completed
            // the lock or if we are blocked trying to acquire it. Only
            // an inflated monitor that is first on the monitor list in
            // the first frame can block us on a monitor enter.
            markWord mark = monitor->owner()->mark();
+           // The first stage of async deflation does not affect any field
+           // used by this comparison so the ObjectMonitor* is usable here.
            if (mark.has_monitor() &&
                ( // we have marked ourself as pending on this monitor
                  mark.monitor() == thread()->current_pending_monitor() ||
                  // we are not the owner of this monitor
                  !mark.monitor()->is_entered(thread())