markOop.cpp revision 2721:f08d439fab8c 
1/*
2 * Copyright (c) 1997, 2010, 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
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23 */
24
25#include "precompiled.hpp"
26#include "oops/markOop.hpp"
27#ifdef TARGET_OS_FAMILY_linux
28# include "thread_linux.inline.hpp"
29#endif
30#ifdef TARGET_OS_FAMILY_solaris
31# include "thread_solaris.inline.hpp"
32#endif
33#ifdef TARGET_OS_FAMILY_windows
34# include "thread_windows.inline.hpp"
35#endif
36#ifdef TARGET_OS_FAMILY_bsd
37# include "thread_bsd.inline.hpp"
38#endif
39
40
41void markOopDesc::print_on(outputStream* st) const {
42  if (is_locked()) {
43    st->print("locked(0x%lx)->", value());
44    markOop(*(markOop*)value())->print_on(st);
45  } else {
46    assert(is_unlocked() || has_bias_pattern(), "just checking");
47    st->print("mark(");
48    if (has_bias_pattern())  st->print("biased,");
49    st->print("hash %#lx,", hash());
50    st->print("age %d)", age());
51  }
52}
53
54
55// Give advice about whether the oop that contains this markOop
56// should be cached or not.
57bool markOopDesc::should_not_be_cached() const {
58  // the cast is because decode_pointer() isn't marked const
59  if (is_marked() && ((markOopDesc *)this)->decode_pointer() != NULL) {
60    // If the oop containing this markOop is being forwarded, then
61    // we are in the middle of GC and we do not want the containing
62    // oop to be added to a cache. We have no way of knowing whether
63    // the cache has already been visited by the current GC phase so
64    // we don't know whether the forwarded oop will be properly
65    // processed in this phase. If the forwarded oop is not properly
66    // processed, then we'll see strange crashes or asserts during
67    // the next GC run because the markOop will contain an unexpected
68    // value.
69    //
70    // This situation has been seen when we are GC'ing a methodOop
71    // because we use the methodOop while we're GC'ing it. Scary
72    // stuff. Some of the uses the methodOop cause the methodOop to
73    // be added to the OopMapCache in the instanceKlass as a side
74    // effect. This check lets the cache maintainer know when a
75    // cache addition would not be safe.
76    return true;
77  }
78
79  // caching the containing oop should be just fine
80  return false;
81}
82