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.
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 "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
36 void InstanceRefKlass::update_nonstatic_oop_maps(Klass* k) {
37 // Clear the nonstatic oop-map entries corresponding to referent
38 // and nextPending field. They are treated specially by the
39 // garbage collector.
40 // The discovered field is used only by the garbage collector
41 // and is also treated specially.
42 InstanceKlass* ik = InstanceKlass::cast(k);
43
44 // Check that we have the right class
45 debug_only(static bool first_time = true);
46 assert(k == SystemDictionary::Reference_klass() && first_time,
47 "Invalid update of Reference maps");
48 debug_only(first_time = false);
49 assert(ik->nonstatic_oop_map_count() == 1, "just checking");
50
51 OopMapBlock* map = ik->start_of_nonstatic_oop_maps();
52
53 // Check that the current map is (2,4) - currently points at field with
54 // offset 2 (words) and has 4 map entries.
55 debug_only(int offset = java_lang_ref_Reference::referent_offset);
56 debug_only(unsigned int count = ((java_lang_ref_Reference::discovered_offset -
57 java_lang_ref_Reference::referent_offset)/heapOopSize) + 1);
58
59 if (UseSharedSpaces) {
60 assert(map->offset() == java_lang_ref_Reference::queue_offset &&
61 map->count() == 1, "just checking");
62 } else {
63 assert(map->offset() == offset && map->count() == count,
64 "just checking");
65
66 // Update map to (3,1) - point to offset of 3 (words) with 1 map entry.
67 map->set_offset(java_lang_ref_Reference::queue_offset);
68 map->set_count(1);
69 }
70 }
71
72 void InstanceRefKlass::update_nonstatic_ephemeron_oop_maps(Klass* k) {
73 // Clear the nonstatic oop-map entry corresponding to value field.
74 // It is treated specially by the garbage collector.
75 InstanceKlass* ik = InstanceKlass::cast(k);
76
77 // Check that we have the right class
78 debug_only(static bool first_time = true);
79 assert(k == SystemDictionary::Ephemeron_klass() && first_time,
80 "Invalid update of Ephemeron maps");
81 debug_only(first_time = false);
82 assert(ik->nonstatic_oop_map_count() == 2, "just checking");
83
84 // skip 1st map as it's the copy of the augmented Reference's map
85 OopMapBlock* map = ik->start_of_nonstatic_oop_maps() + 1;
86
87 debug_only(int offset = java_lang_ref_Ephemeron::value_offset);
88
89 if (UseSharedSpaces) {
90 assert(map->offset() == offset && map->count() == 0,
91 "just checking");
92 } else {
93 assert(map->offset() == offset && map->count() == 1,
94 "just checking");
95
96 // Update map to have 0 oops.
97 map->set_count(0);
98 }
99 }
100
101
102 // Verification
103
104 void InstanceRefKlass::oop_verify_on(oop obj, outputStream* st) {
105 InstanceKlass::oop_verify_on(obj, st);
106 // Verify referent field
107 oop referent = java_lang_ref_Reference::referent(obj);
108 if (referent != NULL) {
109 guarantee(referent->is_oop(), "referent field heap failed");
110 }
111 // Verify next field
112 oop next = java_lang_ref_Reference::next(obj);
113 if (next != NULL) {
114 guarantee(next->is_oop(), "next field should be an oop");
115 guarantee(next->is_instance(), "next field should be an instance");
116 guarantee(InstanceKlass::cast(next->klass())->is_reference_instance_klass(), "next field verify failed");
117 }
118 }
119
120 bool InstanceRefKlass::owns_pending_list_lock(JavaThread* thread) {
121 if (java_lang_ref_Reference::pending_list_lock() == NULL) return false;
122 Handle h_lock(thread, java_lang_ref_Reference::pending_list_lock());
123 return ObjectSynchronizer::current_thread_holds_lock(thread, h_lock);
124 }
125
126 void InstanceRefKlass::acquire_pending_list_lock(BasicLock *pending_list_basic_lock) {
127 // we may enter this with pending exception set
128 PRESERVE_EXCEPTION_MARK; // exceptions are never thrown, needed for TRAPS argument
129
130 // Create a HandleMark in case we retry a GC multiple times.
131 // Each time we attempt the GC, we allocate the handle below
132 // to hold the pending list lock. We want to free this handle.
133 HandleMark hm;
134
135 Handle h_lock(THREAD, java_lang_ref_Reference::pending_list_lock());
136 ObjectSynchronizer::fast_enter(h_lock, pending_list_basic_lock, false, THREAD);
137 assert(ObjectSynchronizer::current_thread_holds_lock(
138 JavaThread::current(), h_lock),
139 "Locking should have succeeded");
140 if (HAS_PENDING_EXCEPTION) CLEAR_PENDING_EXCEPTION;
141 }
142
143 void InstanceRefKlass::release_and_notify_pending_list_lock(
144 BasicLock *pending_list_basic_lock) {
145 // we may enter this with pending exception set
146 PRESERVE_EXCEPTION_MARK; // exceptions are never thrown, needed for TRAPS argument
147
148 // Create a HandleMark in case we retry a GC multiple times.
149 // Each time we attempt the GC, we allocate the handle below
150 // to hold the pending list lock. We want to free this handle.
151 HandleMark hm;
152
153 Handle h_lock(THREAD, java_lang_ref_Reference::pending_list_lock());
154 assert(ObjectSynchronizer::current_thread_holds_lock(
155 JavaThread::current(), h_lock),
156 "Lock should be held");
157 // Notify waiters on pending lists lock if there is any reference.
158 if (java_lang_ref_Reference::pending_list() != NULL) {
159 ObjectSynchronizer::notifyall(h_lock, THREAD);
160 }
161 ObjectSynchronizer::fast_exit(h_lock(), pending_list_basic_lock, THREAD);
162 if (HAS_PENDING_EXCEPTION) CLEAR_PENDING_EXCEPTION;
163 }