instanceRefKlass.cpp revision 8413:92457dfb91bd 
1/*
2 * Copyright (c) 1997, 2015, 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.
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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 "classfile/javaClasses.hpp"
27#include "classfile/systemDictionary.hpp"
28#include "gc/shared/collectedHeap.inline.hpp"
29#include "gc/shared/genCollectedHeap.hpp"
30#include "gc/shared/specialized_oop_closures.hpp"
31#include "oops/instanceRefKlass.inline.hpp"
32#include "oops/oop.inline.hpp"
33#include "utilities/macros.hpp"
34#include "utilities/preserveException.hpp"
35
36PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
37
38void InstanceRefKlass::update_nonstatic_oop_maps(Klass* k) {
39  // Clear the nonstatic oop-map entries corresponding to referent
40  // and nextPending field.  They are treated specially by the
41  // garbage collector.
42  // The discovered field is used only by the garbage collector
43  // and is also treated specially.
44  InstanceKlass* ik = InstanceKlass::cast(k);
45
46  // Check that we have the right class
47  debug_only(static bool first_time = true);
48  assert(k == SystemDictionary::Reference_klass() && first_time,
49         "Invalid update of maps");
50  debug_only(first_time = false);
51  assert(ik->nonstatic_oop_map_count() == 1, "just checking");
52
53  OopMapBlock* map = ik->start_of_nonstatic_oop_maps();
54
55  // Check that the current map is (2,4) - currently points at field with
56  // offset 2 (words) and has 4 map entries.
57  debug_only(int offset = java_lang_ref_Reference::referent_offset);
58  debug_only(unsigned int count = ((java_lang_ref_Reference::discovered_offset -
59    java_lang_ref_Reference::referent_offset)/heapOopSize) + 1);
60
61  if (UseSharedSpaces) {
62    assert(map->offset() == java_lang_ref_Reference::queue_offset &&
63           map->count() == 1, "just checking");
64  } else {
65    assert(map->offset() == offset && map->count() == count,
66           "just checking");
67
68    // Update map to (3,1) - point to offset of 3 (words) with 1 map entry.
69    map->set_offset(java_lang_ref_Reference::queue_offset);
70    map->set_count(1);
71  }
72}
73
74
75// Verification
76
77void InstanceRefKlass::oop_verify_on(oop obj, outputStream* st) {
78  InstanceKlass::oop_verify_on(obj, st);
79  // Verify referent field
80  oop referent = java_lang_ref_Reference::referent(obj);
81  if (referent != NULL) {
82    guarantee(referent->is_oop(), "referent field heap failed");
83  }
84  // Verify next field
85  oop next = java_lang_ref_Reference::next(obj);
86  if (next != NULL) {
87    guarantee(next->is_oop(), "next field verify failed");
88    guarantee(next->is_instanceRef(), "next field verify failed");
89  }
90}
91
92bool InstanceRefKlass::owns_pending_list_lock(JavaThread* thread) {
93  if (java_lang_ref_Reference::pending_list_lock() == NULL) return false;
94  Handle h_lock(thread, java_lang_ref_Reference::pending_list_lock());
95  return ObjectSynchronizer::current_thread_holds_lock(thread, h_lock);
96}
97
98void InstanceRefKlass::acquire_pending_list_lock(BasicLock *pending_list_basic_lock) {
99  // we may enter this with pending exception set
100  PRESERVE_EXCEPTION_MARK;  // exceptions are never thrown, needed for TRAPS argument
101
102  // Create a HandleMark in case we retry a GC multiple times.
103  // Each time we attempt the GC, we allocate the handle below
104  // to hold the pending list lock. We want to free this handle.
105  HandleMark hm;
106
107  Handle h_lock(THREAD, java_lang_ref_Reference::pending_list_lock());
108  ObjectSynchronizer::fast_enter(h_lock, pending_list_basic_lock, false, THREAD);
109  assert(ObjectSynchronizer::current_thread_holds_lock(
110           JavaThread::current(), h_lock),
111         "Locking should have succeeded");
112  if (HAS_PENDING_EXCEPTION) CLEAR_PENDING_EXCEPTION;
113}
114
115void InstanceRefKlass::release_and_notify_pending_list_lock(
116  BasicLock *pending_list_basic_lock) {
117  // we may enter this with pending exception set
118  PRESERVE_EXCEPTION_MARK;  // exceptions are never thrown, needed for TRAPS argument
119
120  // Create a HandleMark in case we retry a GC multiple times.
121  // Each time we attempt the GC, we allocate the handle below
122  // to hold the pending list lock. We want to free this handle.
123  HandleMark hm;
124
125  Handle h_lock(THREAD, java_lang_ref_Reference::pending_list_lock());
126  assert(ObjectSynchronizer::current_thread_holds_lock(
127           JavaThread::current(), h_lock),
128         "Lock should be held");
129  // Notify waiters on pending lists lock if there is any reference.
130  if (java_lang_ref_Reference::pending_list() != NULL) {
131    ObjectSynchronizer::notifyall(h_lock, THREAD);
132  }
133  ObjectSynchronizer::fast_exit(h_lock(), pending_list_basic_lock, THREAD);
134  if (HAS_PENDING_EXCEPTION) CLEAR_PENDING_EXCEPTION;
135}
136