rev 49182 : 8198445: Access API for primitive/native arraycopy
rev 49183 : [mq]: 8198445-1.patch
1 /*
2 * Copyright (c) 2017, 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.
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23 */
24
25 #include "precompiled.hpp"
26 #include "accessBackend.inline.hpp"
27 #include "gc/shared/collectedHeap.hpp"
28 #include "oops/oop.inline.hpp"
29 #include "runtime/mutexLocker.hpp"
30 #include "runtime/vm_version.hpp"
31 #include "utilities/copy.hpp"
32
33 namespace AccessInternal {
34 // VM_Version::supports_cx8() is a surrogate for 'supports atomic long memory ops'.
35 //
36 // On platforms which do not support atomic compare-and-swap of jlong (8 byte)
37 // values we have to use a lock-based scheme to enforce atomicity. This has to be
38 // applied to all Unsafe operations that set the value of a jlong field. Even so
39 // the compareAndSwapLong operation will not be atomic with respect to direct stores
40 // to the field from Java code. It is important therefore that any Java code that
41 // utilizes these Unsafe jlong operations does not perform direct stores. To permit
42 // direct loads of the field from Java code we must also use Atomic::store within the
43 // locked regions. And for good measure, in case there are direct stores, we also
44 // employ Atomic::load within those regions. Note that the field in question must be
45 // volatile and so must have atomic load/store accesses applied at the Java level.
46 //
47 // The locking scheme could utilize a range of strategies for controlling the locking
48 // granularity: from a lock per-field through to a single global lock. The latter is
49 // the simplest and is used for the current implementation. Note that the Java object
50 // that contains the field, can not, in general, be used for locking. To do so can lead
51 // to deadlocks as we may introduce locking into what appears to the Java code to be a
52 // lock-free path.
53 //
54 // As all the locked-regions are very short and themselves non-blocking we can treat
55 // them as leaf routines and elide safepoint checks (ie we don't perform any thread
56 // state transitions even when blocking for the lock). Note that if we do choose to
57 // add safepoint checks and thread state transitions, we must ensure that we calculate
58 // the address of the field _after_ we have acquired the lock, else the object may have
59 // been moved by the GC
60
61 #ifndef SUPPORTS_NATIVE_CX8
62
63 // This is intentionally in the cpp file rather than the .inline.hpp file. It seems
64 // desirable to trade faster JDK build times (not propagating vm_version.hpp)
65 // for slightly worse runtime atomic jlong performance on 32 bit machines with
66 // support for 64 bit atomics.
67 bool wide_atomic_needs_locking() {
68 return !VM_Version::supports_cx8();
69 }
70
71 AccessLocker::AccessLocker() {
72 assert(!VM_Version::supports_cx8(), "why else?");
73 UnsafeJlong_lock->lock_without_safepoint_check();
74 }
75
76 AccessLocker::~AccessLocker() {
77 UnsafeJlong_lock->unlock();
78 }
79
80 #endif
81
82 // These forward copying calls to Copy without exposing the Copy type in headers unnecessarily
83
84 void arraycopy_arrayof_conjoint_oops(void* src, void* dst, size_t length) {
85 Copy::arrayof_conjoint_oops(reinterpret_cast<HeapWord*>(src),
86 reinterpret_cast<HeapWord*>(dst), length);
87 }
88
89 void arraycopy_conjoint_oops(oop* src, oop* dst, size_t length) {
90 Copy::conjoint_oops_atomic(src, dst, length);
91 }
92
93 void arraycopy_conjoint_oops(narrowOop* src, narrowOop* dst, size_t length) {
94 Copy::conjoint_oops_atomic(src, dst, length);
95 }
96
97 void arraycopy_disjoint_words(void* src, void* dst, size_t length) {
98 Copy::disjoint_words(reinterpret_cast<HeapWord*>(src),
99 reinterpret_cast<HeapWord*>(dst), length);
100 }
101
102 void arraycopy_disjoint_words_atomic(void* src, void* dst, size_t length) {
103 Copy::disjoint_words_atomic(reinterpret_cast<HeapWord*>(src),
104 reinterpret_cast<HeapWord*>(dst), length);
105 }
106
107 template<>
108 void arraycopy_conjoint<char>(char* src, char* dst, size_t length) {
109 Copy::conjoint_jbytes(src, dst, length);
110 }
111
112 template<>
113 void arraycopy_conjoint<jbyte>(jbyte* src, jbyte* dst, size_t length) {
114 Copy::conjoint_jbytes(src, dst, length);
115 }
116
117 template<>
118 void arraycopy_conjoint<jshort>(jshort* src, jshort* dst, size_t length) {
119 Copy::conjoint_jshorts_atomic(src, dst, length);
120 }
121
122 template<>
123 void arraycopy_conjoint<jint>(jint* src, jint* dst, size_t length) {
124 Copy::conjoint_jints_atomic(src, dst, length);
125 }
126
127 template<>
128 void arraycopy_conjoint<jlong>(jlong* src, jlong* dst, size_t length) {
129 Copy::conjoint_jlongs_atomic(src, dst, length);
130 }
131
132 template<>
133 void arraycopy_arrayof_conjoint<jbyte>(jbyte* src, jbyte* dst, size_t length) {
134 Copy::arrayof_conjoint_jbytes(reinterpret_cast<HeapWord*>(src),
135 reinterpret_cast<HeapWord*>(dst),
136 length);
137 }
138
139 template<>
140 void arraycopy_arrayof_conjoint<jshort>(jshort* src, jshort* dst, size_t length) {
141 Copy::arrayof_conjoint_jshorts(reinterpret_cast<HeapWord*>(src),
142 reinterpret_cast<HeapWord*>(dst),
143 length);
144 }
145
146 template<>
147 void arraycopy_arrayof_conjoint<jint>(jint* src, jint* dst, size_t length) {
148 Copy::arrayof_conjoint_jints(reinterpret_cast<HeapWord*>(src),
149 reinterpret_cast<HeapWord*>(dst),
150 length);
151 }
152
153 template<>
154 void arraycopy_arrayof_conjoint<jlong>(jlong* src, jlong* dst, size_t length) {
155 Copy::arrayof_conjoint_jlongs(reinterpret_cast<HeapWord*>(src),
156 reinterpret_cast<HeapWord*>(dst),
157 length);
158 }
159
160 template<>
161 void arraycopy_conjoint_atomic<jbyte>(jbyte* src, jbyte* dst, size_t length) {
162 Copy::conjoint_jbytes_atomic(src, dst, length);
163 }
164
165 template<>
166 void arraycopy_conjoint_atomic<jshort>(jshort* src, jshort* dst, size_t length) {
167 Copy::conjoint_jshorts_atomic(src, dst, length);
168 }
169
170 template<>
171 void arraycopy_conjoint_atomic<jint>(jint* src, jint* dst, size_t length) {
172 Copy::conjoint_jints_atomic(src, dst, length);
173 }
174
175 template<>
176 void arraycopy_conjoint_atomic<jlong>(jlong* src, jlong* dst, size_t length) {
177 Copy::conjoint_jlongs_atomic(src, dst, length);
178 }
179 }
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