1 /*
   2  * Copyright (c) 1997, 2008, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 # include "incls/_precompiled.incl"
  26 # include "incls/_markOop.cpp.incl"
  27 
  28 
  29 void markOopDesc::print_on(outputStream* st) const {
  30   if (is_locked()) {
  31     st->print("locked(0x%lx)->", value());
  32     markOop(*(markOop*)value())->print_on(st);
  33   } else {
  34     assert(is_unlocked() || has_bias_pattern(), "just checking");
  35     st->print("mark(");
  36     if (has_bias_pattern())  st->print("biased,");
  37     st->print("hash %#lx,", hash());
  38     st->print("age %d)", age());
  39   }
  40 }
  41 
  42 
  43 // Give advice about whether the oop that contains this markOop
  44 // should be cached or not.
  45 bool markOopDesc::should_not_be_cached() const {
  46   // the cast is because decode_pointer() isn't marked const
  47   if (is_marked() && ((markOopDesc *)this)->decode_pointer() != NULL) {
  48     // If the oop containing this markOop is being forwarded, then
  49     // we are in the middle of GC and we do not want the containing
  50     // oop to be added to a cache. We have no way of knowing whether
  51     // the cache has already been visited by the current GC phase so
  52     // we don't know whether the forwarded oop will be properly
  53     // processed in this phase. If the forwarded oop is not properly
  54     // processed, then we'll see strange crashes or asserts during
  55     // the next GC run because the markOop will contain an unexpected
  56     // value.
  57     //
  58     // This situation has been seen when we are GC'ing a methodOop
  59     // because we use the methodOop while we're GC'ing it. Scary
  60     // stuff. Some of the uses the methodOop cause the methodOop to
  61     // be added to the OopMapCache in the instanceKlass as a side
  62     // effect. This check lets the cache maintainer know when a
  63     // cache addition would not be safe.
  64     return true;
  65   }
  66 
  67   // caching the containing oop should be just fine
  68   return false;
  69 }