1/*
2 * Copyright (c) 1997, 2018, 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 "oops/instanceRefKlass.inline.hpp"
29#include "oops/oop.inline.hpp"
30
31void InstanceRefKlass::update_nonstatic_oop_maps(Klass* k) {
32 // Clear the nonstatic oop-map entries corresponding to referent
33 // and discovered fields. They are treated specially by the
34 // garbage collector.
35 InstanceKlass* ik = InstanceKlass::cast(k);
36
37 // Check that we have the right class
38 debug_only(static bool first_time = true);
39 assert(k == SystemDictionary::Reference_klass() && first_time,
40 "Invalid update of maps");
41 debug_only(first_time = false);
42 assert(ik->nonstatic_oop_map_count() == 1, "just checking");
43
44 OopMapBlock* map = ik->start_of_nonstatic_oop_maps();
45
46#ifdef ASSERT
47 // Verify fields are in the expected places.
48 int referent_offset = java_lang_ref_Reference::referent_offset;
49 int queue_offset = java_lang_ref_Reference::queue_offset;
50 int next_offset = java_lang_ref_Reference::next_offset;
51 int discovered_offset = java_lang_ref_Reference::discovered_offset;
52 assert(referent_offset < queue_offset, "just checking");
53 assert(queue_offset < next_offset, "just checking");
54 assert(next_offset < discovered_offset, "just checking");
55 const unsigned int count =
56 1 + ((discovered_offset - referent_offset) / heapOopSize);
57 assert(count == 4, "just checking");
58#endif // ASSERT
59
60 // Updated map starts at "queue", covers "queue" and "next".
61 const int new_offset = java_lang_ref_Reference::queue_offset;
62 const unsigned int new_count = 2; // queue and next
63
64 // Verify existing map is as expected, and update if needed.
65 if (UseSharedSpaces) {
66 assert(map->offset() == new_offset, "just checking");
67 assert(map->count() == new_count, "just checking");
68 } else {
69 assert(map->offset() == referent_offset, "just checking");
70 assert(map->count() == count, "just checking");
71 map->set_offset(new_offset);
72 map->set_count(new_count);
73 }
74}
75
76
77// Verification
78
79void InstanceRefKlass::oop_verify_on(oop obj, outputStream* st) {
80 InstanceKlass::oop_verify_on(obj, st);
81 // Verify referent field
82 oop referent = java_lang_ref_Reference::referent(obj);
83 if (referent != NULL) {
84 guarantee(oopDesc::is_oop(referent), "referent field heap failed");
85 }
86 // Additional verification for next field, which must be a Reference or null
87 oop next = java_lang_ref_Reference::next(obj);
88 if (next != NULL) {
89 guarantee(oopDesc::is_oop(next), "next field should be an oop");
90 guarantee(next->is_instance(), "next field should be an instance");
91 guarantee(InstanceKlass::cast(next->klass())->is_reference_instance_klass(), "next field verify failed");
92 }
93}
94