1 /*
2 * Copyright (c) 2015, 2019, 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 "aot/aotLoader.hpp"
27 #include "classfile/classLoaderDataGraph.hpp"
28 #include "classfile/stringTable.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "code/codeCache.hpp"
31 #include "gc/g1/g1BarrierSet.hpp"
32 #include "gc/g1/g1CodeBlobClosure.hpp"
33 #include "gc/g1/g1CollectedHeap.inline.hpp"
34 #include "gc/g1/g1CollectorState.hpp"
35 #include "gc/g1/g1GCPhaseTimes.hpp"
36 #include "gc/g1/g1ParScanThreadState.inline.hpp"
37 #include "gc/g1/g1Policy.hpp"
38 #include "gc/g1/g1RootClosures.hpp"
39 #include "gc/g1/g1RootProcessor.hpp"
40 #include "gc/g1/heapRegion.inline.hpp"
41 #include "gc/shared/referenceProcessor.hpp"
42 #include "memory/allocation.inline.hpp"
43 #include "memory/universe.hpp"
44 #include "runtime/mutexLocker.inline.hpp"
45 #include "services/management.hpp"
46 #include "utilities/macros.hpp"
47
48 void G1RootProcessor::worker_has_discovered_all_strong_nmethods() {
49 assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");
50
51 uint new_value = (uint)Atomic::add(1, &_n_workers_discovered_strong_classes);
52 if (new_value == n_workers()) {
53 // This thread is last. Notify the others.
54 MonitorLocker ml(&_lock, Mutex::_no_safepoint_check_flag);
55 _lock.notify_all();
56 }
57 }
58
59 void G1RootProcessor::wait_until_all_strong_nmethods_discovered() {
60 assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");
61
62 if ((uint)_n_workers_discovered_strong_classes != n_workers()) {
63 MonitorLocker ml(&_lock, Mutex::_no_safepoint_check_flag);
64 while ((uint)_n_workers_discovered_strong_classes != n_workers()) {
65 ml.wait(0);
66 }
67 }
68 }
69
70 G1RootProcessor::G1RootProcessor(G1CollectedHeap* g1h, uint n_workers) :
71 _g1h(g1h),
72 _process_strong_tasks(G1RP_PS_NumElements),
73 _srs(n_workers),
74 _lock(Mutex::leaf, "G1 Root Scan barrier lock", false, Mutex::_safepoint_check_never),
75 _n_workers_discovered_strong_classes(0) {}
76
77 void G1RootProcessor::evacuate_roots(G1ParScanThreadState* pss, uint worker_id) {
78 G1GCPhaseTimes* phase_times = _g1h->phase_times();
79
80 G1EvacPhaseTimesTracker timer(phase_times, pss, G1GCPhaseTimes::ExtRootScan, worker_id);
81
82 G1EvacuationRootClosures* closures = pss->closures();
83 process_java_roots(closures, phase_times, worker_id, closures->trace_metadata() /* notify_claimed_nmethods_done */);
84
85 process_vm_roots(closures, phase_times, worker_id);
86
87 {
88 // Now the CM ref_processor roots.
89 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CMRefRoots, worker_id);
90 if (_process_strong_tasks.try_claim_task(G1RP_PS_refProcessor_oops_do)) {
91 // We need to treat the discovered reference lists of the
92 // concurrent mark ref processor as roots and keep entries
93 // (which are added by the marking threads) on them live
94 // until they can be processed at the end of marking.
95 _g1h->ref_processor_cm()->weak_oops_do(closures->strong_oops());
96 }
97 }
98
99 if (closures->trace_metadata()) {
100 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::WaitForStrongRoots, worker_id);
101 // Wait to make sure all workers passed the strong nmethods phase.
102 wait_until_all_strong_nmethods_discovered();
103 }
104
105 _process_strong_tasks.all_tasks_completed(n_workers());
106 }
107
108 // Adaptor to pass the closures to the strong roots in the VM.
109 class StrongRootsClosures : public G1RootClosures {
110 OopClosure* _roots;
111 CLDClosure* _clds;
112 CodeBlobClosure* _blobs;
113 public:
114 StrongRootsClosures(OopClosure* roots, CLDClosure* clds, CodeBlobClosure* blobs) :
115 _roots(roots), _clds(clds), _blobs(blobs) {}
116
117 OopClosure* weak_oops() { return NULL; }
118 OopClosure* strong_oops() { return _roots; }
119
120 CLDClosure* weak_clds() { return NULL; }
121 CLDClosure* strong_clds() { return _clds; }
122
123 CodeBlobClosure* strong_codeblobs() { return _blobs; }
124 };
125
126 void G1RootProcessor::process_strong_roots(OopClosure* oops,
127 CLDClosure* clds,
128 CodeBlobClosure* blobs) {
129 StrongRootsClosures closures(oops, clds, blobs);
130
131 process_java_roots(&closures, NULL, 0);
132 process_vm_roots(&closures, NULL, 0);
133
134 _process_strong_tasks.all_tasks_completed(n_workers());
135 }
136
137 // Adaptor to pass the closures to all the roots in the VM.
138 class AllRootsClosures : public G1RootClosures {
139 OopClosure* _roots;
140 CLDClosure* _clds;
141 public:
142 AllRootsClosures(OopClosure* roots, CLDClosure* clds) :
143 _roots(roots), _clds(clds) {}
144
145 OopClosure* weak_oops() { return _roots; }
146 OopClosure* strong_oops() { return _roots; }
147
148 // By returning the same CLDClosure for both weak and strong CLDs we ensure
149 // that a single walk of the CLDG will invoke the closure on all CLDs i the
150 // system.
151 CLDClosure* weak_clds() { return _clds; }
152 CLDClosure* strong_clds() { return _clds; }
153
154 // We don't want to visit code blobs more than once, so we return NULL for the
155 // strong case and walk the entire code cache as a separate step.
156 CodeBlobClosure* strong_codeblobs() { return NULL; }
157 };
158
159 void G1RootProcessor::process_all_roots(OopClosure* oops,
160 CLDClosure* clds,
161 CodeBlobClosure* blobs) {
162 AllRootsClosures closures(oops, clds);
163
164 process_java_roots(&closures, NULL, 0);
165 process_vm_roots(&closures, NULL, 0);
166
167 process_code_cache_roots(blobs, NULL, 0);
168
169 _process_strong_tasks.all_tasks_completed(n_workers());
170 }
171
172 void G1RootProcessor::process_java_roots(G1RootClosures* closures,
173 G1GCPhaseTimes* phase_times,
174 uint worker_id,
175 bool notify_claimed_nmethods_done) {
176 // We need to make make sure that the "strong" nmethods are processed first
177 // using the strong closure. Only after that we process the weakly reachable
178 // nmethods.
179 // We need to strictly separate the strong and weak nmethod processing because
180 // any processing claims that nmethod, i.e. will not be iterated again.
181 // Which means if an nmethod is processed first and claimed, the strong processing
182 // will not happen, and the oops reachable by that nmethod will not be marked
183 // properly.
184 //
185 // That is why we process strong nmethods first, synchronize all threads via a
186 // barrier, and only then allow weak processing. To minimize the wait time at
187 // that barrier we do the strong nmethod processing first, and immediately after-
188 // wards indicate that that thread is done. Hopefully other root processing after
189 // nmethod processing is enough so there is no need to wait.
190 //
191 // This is only required in the concurrent start pause with class unloading enabled.
192 {
193 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ThreadRoots, worker_id);
194 bool is_par = n_workers() > 1;
195 Threads::possibly_parallel_oops_do(is_par,
196 closures->strong_oops(),
197 closures->strong_codeblobs());
198 }
199
200 // This is the point where this worker thread will not find more strong nmethods.
201 // Report this so G1 can synchronize the strong and weak CLDs/nmethods processing.
202 if (notify_claimed_nmethods_done) {
203 worker_has_discovered_all_strong_nmethods();
204 }
205
206 {
207 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CLDGRoots, worker_id);
208 if (_process_strong_tasks.try_claim_task(G1RP_PS_ClassLoaderDataGraph_oops_do)) {
209 ClassLoaderDataGraph::roots_cld_do(closures->strong_clds(), closures->weak_clds());
210 }
211 }
212 }
213
214 void G1RootProcessor::process_vm_roots(G1RootClosures* closures,
215 G1GCPhaseTimes* phase_times,
216 uint worker_id) {
217 OopClosure* strong_roots = closures->strong_oops();
218
219 {
220 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::UniverseRoots, worker_id);
221 if (_process_strong_tasks.try_claim_task(G1RP_PS_Universe_oops_do)) {
222 Universe::oops_do(strong_roots);
223 }
224 }
225
226 {
227 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JNIRoots, worker_id);
228 if (_process_strong_tasks.try_claim_task(G1RP_PS_JNIHandles_oops_do)) {
229 JNIHandles::oops_do(strong_roots);
230 }
231 }
232
233 {
234 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ObjectSynchronizerRoots, worker_id);
235 if (_process_strong_tasks.try_claim_task(G1RP_PS_ObjectSynchronizer_oops_do)) {
236 ObjectSynchronizer::oops_do(strong_roots);
237 }
238 }
239
240 {
241 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ManagementRoots, worker_id);
242 if (_process_strong_tasks.try_claim_task(G1RP_PS_Management_oops_do)) {
243 Management::oops_do(strong_roots);
244 }
245 }
246
247 {
248 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JVMTIRoots, worker_id);
249 if (_process_strong_tasks.try_claim_task(G1RP_PS_jvmti_oops_do)) {
250 JvmtiExport::oops_do(strong_roots);
251 }
252 }
253
254 #if INCLUDE_AOT
255 if (UseAOT) {
256 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::AOTCodeRoots, worker_id);
257 if (_process_strong_tasks.try_claim_task(G1RP_PS_aot_oops_do)) {
258 AOTLoader::oops_do(strong_roots);
259 }
260 }
261 #endif
262
263 {
264 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::SystemDictionaryRoots, worker_id);
265 if (_process_strong_tasks.try_claim_task(G1RP_PS_SystemDictionary_oops_do)) {
266 SystemDictionary::oops_do(strong_roots);
267 }
268 }
269 }
270
271 void G1RootProcessor::process_code_cache_roots(CodeBlobClosure* code_closure,
272 G1GCPhaseTimes* phase_times,
273 uint worker_id) {
274 if (_process_strong_tasks.try_claim_task(G1RP_PS_CodeCache_oops_do)) {
275 CodeCache::blobs_do(code_closure);
276 }
277 }
278
279 uint G1RootProcessor::n_workers() const {
280 return _srs.n_threads();
281 }