1 /*
2 * Copyright (c) 2022, Red Hat, Inc. 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 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHOBJECTUTILS_INLINE_HPP
26 #define SHARE_GC_SHENANDOAH_SHENANDOAHOBJECTUTILS_INLINE_HPP
27
28 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
29 #include "gc/shenandoah/shenandoahObjectUtils.hpp"
30 #include "oops/klass.hpp"
31 #include "oops/markWord.inline.hpp"
32 #include "oops/oop.inline.hpp"
33 #include "runtime/objectMonitor.inline.hpp"
34 #include "runtime/thread.hpp"
35
36 // This is a variant of oopDesc::actual_mark(), which does the same thing, but also
37 // handles forwarded objects. This is intended to be used by concurrent evacuation only. No other
38 // code is supposed to observe from-space objects.
39 #ifdef _LP64
40 markWord ShenandoahObjectUtils::stable_mark(oop obj) {
41 assert(UseCompactObjectHeaders, "only used with compact object headers");
42 ShenandoahHeap* heap = ShenandoahHeap::heap();
43 assert(heap->is_in(obj), "object not in heap: " PTR_FORMAT, p2i(obj));
44 markWord mark = obj->mark_acquire();
45
46 assert(!mark.is_being_inflated(), "can not be inflating");
47 assert(!mark.has_locker(), "can not be stack-locked");
48
49 // The mark can be in one of the following states:
50 // * Marked - object is forwarded, try again on forwardee
51 // * Inflated - just return mark from inflated monitor
52 // * Fast-locked - return mark
53 // * Neutral - return mark
54
55 // Most common cases first.
56 if (mark.is_neutral() || mark.is_fast_locked()) {
57 return mark;
58 }
59
60 // If object is already forwarded, then resolve it, and try again.
61 if (mark.is_marked()) {
62 if (heap->is_full_gc_move_in_progress()) {
63 // In these cases, we want to return the header as-is: the Klass* would not be overloaded.
64 return mark;
65 }
66 obj = cast_to_oop(mark.decode_pointer());
67 return stable_mark(obj);
68 }
69
70 // CASE: inflated
71 assert(mark.has_monitor(), "must be monitor-locked at this point");
72 // It is safe to access the object monitor because all Java and GC worker threads
73 // participate in the monitor deflation protocol (i.e, they react to handshakes and STS requests).
74 ObjectMonitor* inf = mark.monitor();
75 markWord dmw = inf->header();
76 assert(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT ", original mark: " INTPTR_FORMAT, dmw.value(), mark.value());
77 return dmw;
78 }
79 #endif
80
81 Klass* ShenandoahObjectUtils::klass(oop obj) {
82 if (!UseCompactObjectHeaders) {
83 return obj->klass();
84 }
85 #ifdef _LP64
86 markWord header = stable_mark(obj);
87 assert(header.narrow_klass() != 0, "klass must not be NULL: " INTPTR_FORMAT, header.value());
88 return header.klass();
89 #else
90 return obj->klass();
91 #endif
92 }
93
94 size_t ShenandoahObjectUtils::size(oop obj) {
95 if (!UseCompactObjectHeaders) {
96 return obj->size();
97 }
98 Klass* kls = klass(obj);
99 return obj->size_given_klass(kls);
100 }
101
102 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHOBJECTUTILS_HPP