1 /*
2 * Copyright (c) 2015, 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.
22 */
23
24 #include "precompiled.hpp"
25 #include "gc/z/zBarrier.inline.hpp"
26 #include "gc/z/zHeap.inline.hpp"
27 #include "gc/z/zOop.inline.hpp"
28 #include "gc/z/zOopClosures.inline.hpp"
29 #include "oops/oop.inline.hpp"
30 #include "runtime/safepoint.hpp"
31 #include "utilities/debug.hpp"
32
33 bool ZBarrier::during_mark() {
34 return ZGlobalPhase == ZPhaseMark;
35 }
36
37 bool ZBarrier::during_relocate() {
38 return ZGlobalPhase == ZPhaseRelocate;
39 }
40
41 template <bool finalizable>
42 bool ZBarrier::should_mark_through(uintptr_t addr) {
43 // Finalizable marked oops can still exists on the heap after marking
44 // has completed, in which case we just want to convert this into a
45 // good oop and not push it on the mark stack.
46 if (!during_mark()) {
47 assert(ZAddress::is_marked(addr), "Should be marked");
48 assert(ZAddress::is_finalizable(addr), "Should be finalizable");
49 return false;
50 }
51
52 // During marking, we mark through already marked oops to avoid having
53 // some large part of the object graph hidden behind a pushed, but not
54 // yet flushed, entry on a mutator mark stack. Always marking through
55 // allows the GC workers to proceed through the object graph even if a
56 // mutator touched an oop first, which in turn will reduce the risk of
57 // having to flush mark stacks multiple times to terminate marking.
58 //
59 // However, when doing finalizable marking we don't always want to mark
60 // through. First, marking through an already strongly marked oop would
61 // be wasteful, since we will then proceed to do finalizable marking on
62 // an object which is, or will be, marked strongly. Second, marking
63 // through an already finalizable marked oop would also be wasteful,
64 // since such oops can never end up on a mutator mark stack and can
65 // therefore not hide some part of the object graph from GC workers.
66 if (finalizable) {
67 return !ZAddress::is_marked(addr);
68 }
69
70 // Mark through
71 return true;
72 }
73
74 template <bool finalizable, bool publish>
75 uintptr_t ZBarrier::mark(uintptr_t addr) {
76 uintptr_t good_addr;
77
78 if (ZAddress::is_marked(addr)) {
79 // Already marked, but try to mark though anyway
80 good_addr = ZAddress::good(addr);
81 } else if (ZAddress::is_remapped(addr)) {
82 // Already remapped, but also needs to be marked
83 good_addr = ZAddress::good(addr);
84 } else {
85 // Needs to be both remapped and marked
86 good_addr = remap(addr);
87 }
88
89 // Mark
90 if (should_mark_through<finalizable>(addr)) {
91 ZHeap::heap()->mark_object<finalizable, publish>(good_addr);
92 }
93
94 return good_addr;
95 }
96
97 uintptr_t ZBarrier::remap(uintptr_t addr) {
98 assert(!ZAddress::is_good(addr), "Should not be good");
99 assert(!ZAddress::is_weak_good(addr), "Should not be weak good");
100
101 if (ZHeap::heap()->is_relocating(addr)) {
102 // Forward
103 return ZHeap::heap()->forward_object(addr);
104 }
105
106 // Remap
107 return ZAddress::good(addr);
108 }
109
110 uintptr_t ZBarrier::relocate(uintptr_t addr) {
111 assert(!ZAddress::is_good(addr), "Should not be good");
112 assert(!ZAddress::is_weak_good(addr), "Should not be weak good");
113
114 if (ZHeap::heap()->is_relocating(addr)) {
115 // Relocate
116 return ZHeap::heap()->relocate_object(addr);
117 }
118
119 // Remap
120 return ZAddress::good(addr);
121 }
122
123 uintptr_t ZBarrier::relocate_or_mark(uintptr_t addr) {
124 return during_relocate() ? relocate(addr) : mark<Strong, Publish>(addr);
125 }
126
127 uintptr_t ZBarrier::relocate_or_remap(uintptr_t addr) {
128 return during_relocate() ? relocate(addr) : remap(addr);
129 }
130
131 //
132 // Load barrier
133 //
134 uintptr_t ZBarrier::load_barrier_on_oop_slow_path(uintptr_t addr) {
135 return relocate_or_mark(addr);
136 }
137
138 void ZBarrier::load_barrier_on_oop_fields(oop o) {
139 assert(ZOop::is_good(o), "Should be good");
140 ZLoadBarrierOopClosure cl;
141 o->oop_iterate(&cl);
142 }
143
144 //
145 // Weak load barrier
146 //
147 uintptr_t ZBarrier::weak_load_barrier_on_oop_slow_path(uintptr_t addr) {
148 return ZAddress::is_weak_good(addr) ? ZAddress::good(addr) : relocate_or_remap(addr);
149 }
150
151 uintptr_t ZBarrier::weak_load_barrier_on_weak_oop_slow_path(uintptr_t addr) {
152 const uintptr_t good_addr = weak_load_barrier_on_oop_slow_path(addr);
153 if (ZHeap::heap()->is_object_strongly_live(good_addr)) {
154 return good_addr;
155 }
156
157 // Not strongly live
158 return 0;
159 }
160
161 uintptr_t ZBarrier::weak_load_barrier_on_phantom_oop_slow_path(uintptr_t addr) {
162 const uintptr_t good_addr = weak_load_barrier_on_oop_slow_path(addr);
163 if (ZHeap::heap()->is_object_live(good_addr)) {
164 return good_addr;
165 }
166
167 // Not live
168 return 0;
169 }
170
171 //
172 // Keep alive barrier
173 //
174 uintptr_t ZBarrier::keep_alive_barrier_on_weak_oop_slow_path(uintptr_t addr) {
175 const uintptr_t good_addr = weak_load_barrier_on_oop_slow_path(addr);
176 assert(ZHeap::heap()->is_object_strongly_live(good_addr), "Should be live");
177 return good_addr;
178 }
179
180 uintptr_t ZBarrier::keep_alive_barrier_on_phantom_oop_slow_path(uintptr_t addr) {
181 const uintptr_t good_addr = weak_load_barrier_on_oop_slow_path(addr);
182 assert(ZHeap::heap()->is_object_live(good_addr), "Should be live");
183 return good_addr;
184 }
185
186 //
187 // Mark barrier
188 //
189 uintptr_t ZBarrier::mark_barrier_on_oop_slow_path(uintptr_t addr) {
190 return mark<Strong, Overflow>(addr);
191 }
192
193 uintptr_t ZBarrier::mark_barrier_on_finalizable_oop_slow_path(uintptr_t addr) {
194 const uintptr_t good_addr = mark<Finalizable, Overflow>(addr);
195 if (ZAddress::is_good(addr)) {
196 // If the oop was already strongly marked/good, then we do
197 // not want to downgrade it to finalizable marked/good.
198 return good_addr;
199 }
200
201 // Make the oop finalizable marked/good, instead of normal marked/good.
202 // This is needed because an object might first becomes finalizable
203 // marked by the GC, and then loaded by a mutator thread. In this case,
204 // the mutator thread must be able to tell that the object needs to be
205 // strongly marked. The finalizable bit in the oop exists to make sure
206 // that a load of a finalizable marked oop will fall into the barrier
207 // slow path so that we can mark the object as strongly reachable.
208 return ZAddress::finalizable_good(good_addr);
209 }
210
211 uintptr_t ZBarrier::mark_barrier_on_root_oop_slow_path(uintptr_t addr) {
212 assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");
213 assert(during_mark(), "Invalid phase");
214
215 // Mark
216 return mark<Strong, Publish>(addr);
217 }
218
219 //
220 // Relocate barrier
221 //
222 uintptr_t ZBarrier::relocate_barrier_on_root_oop_slow_path(uintptr_t addr) {
223 assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");
224 assert(during_relocate(), "Invalid phase");
225
226 // Relocate
227 return relocate(addr);
228 }
229
230 //
231 // Narrow oop variants, never used.
232 //
233 oop ZBarrier::load_barrier_on_oop_field(volatile narrowOop* p) {
234 ShouldNotReachHere();
235 return NULL;
236 }
237
238 oop ZBarrier::load_barrier_on_oop_field_preloaded(volatile narrowOop* p, oop o) {
239 ShouldNotReachHere();
240 return NULL;
241 }
242
243 void ZBarrier::load_barrier_on_oop_array(volatile narrowOop* p, size_t length) {
244 ShouldNotReachHere();
245 }
246
247 oop ZBarrier::load_barrier_on_weak_oop_field_preloaded(volatile narrowOop* p, oop o) {
248 ShouldNotReachHere();
249 return NULL;
250 }
251
252 oop ZBarrier::load_barrier_on_phantom_oop_field_preloaded(volatile narrowOop* p, oop o) {
253 ShouldNotReachHere();
254 return NULL;
255 }
256
257 oop ZBarrier::weak_load_barrier_on_oop_field_preloaded(volatile narrowOop* p, oop o) {
258 ShouldNotReachHere();
259 return NULL;
260 }
261
262 oop ZBarrier::weak_load_barrier_on_weak_oop_field_preloaded(volatile narrowOop* p, oop o) {
263 ShouldNotReachHere();
264 return NULL;
265 }
266
267 oop ZBarrier::weak_load_barrier_on_phantom_oop_field_preloaded(volatile narrowOop* p, oop o) {
268 ShouldNotReachHere();
269 return NULL;
270 }