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 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
37
38 void 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
77 void 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
92 bool 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
98 void 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
115 void 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 }