1 /*
2 * Copyright (c) 2024, 2025, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2017, 2022, Red Hat, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
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24 */
25
26 #include "code/codeCache.hpp"
27 #include "code/nmethod.hpp"
28 #include "gc/shared/classUnloadingContext.hpp"
29 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
30 #include "gc/shenandoah/shenandoahEvacOOMHandler.inline.hpp"
31 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
32 #include "gc/shenandoah/shenandoahNMethod.inline.hpp"
33 #include "gc/shenandoah/shenandoahUtils.hpp"
34 #include "memory/resourceArea.hpp"
35 #include "memory/universe.hpp"
36 #include "runtime/atomicAccess.hpp"
37 #include "utilities/powerOfTwo.hpp"
38
39
40 ShenandoahNMethodTable* ShenandoahCodeRoots::_nmethod_table;
41 int ShenandoahCodeRoots::_disarmed_value = 1;
42
43 bool ShenandoahCodeRoots::use_nmethod_barriers_for_mark() {
44 // Continuations need nmethod barriers for scanning stack chunk nmethods.
45 if (Continuations::enabled()) return true;
46
47 // Concurrent class unloading needs nmethod barriers.
48 // When a nmethod is about to be executed, we need to make sure that all its
49 // metadata are marked. The alternative is to remark thread roots at final mark
50 // pause, which would cause latency issues.
51 if (ShenandoahHeap::heap()->unload_classes()) return true;
52
53 // Otherwise, we can go without nmethod barriers.
54 return false;
55 }
56
57 void ShenandoahCodeRoots::initialize() {
58 _nmethod_table = new ShenandoahNMethodTable();
59 }
60
61 void ShenandoahCodeRoots::register_nmethod(nmethod* nm) {
62 assert(CodeCache_lock->owned_by_self(), "Must have CodeCache_lock held");
63 _nmethod_table->register_nmethod(nm);
64 }
65
66 void ShenandoahCodeRoots::unregister_nmethod(nmethod* nm) {
67 assert_locked_or_safepoint(CodeCache_lock);
68 _nmethod_table->unregister_nmethod(nm);
69 }
70
71 void ShenandoahCodeRoots::arm_nmethods_for_mark() {
72 if (use_nmethod_barriers_for_mark()) {
73 BarrierSet::barrier_set()->barrier_set_nmethod()->arm_all_nmethods();
74 }
75 }
76
77 void ShenandoahCodeRoots::arm_nmethods_for_evac() {
78 BarrierSet::barrier_set()->barrier_set_nmethod()->arm_all_nmethods();
79 }
80
81 class ShenandoahDisarmNMethodClosure : public NMethodClosure {
82 private:
83 BarrierSetNMethod* const _bs;
84
85 public:
86 ShenandoahDisarmNMethodClosure() :
87 _bs(BarrierSet::barrier_set()->barrier_set_nmethod()) {
88 }
89
90 virtual void do_nmethod(nmethod* nm) {
91 _bs->disarm(nm);
92 }
93 };
94
95 class ShenandoahDisarmNMethodsTask : public WorkerTask {
96 private:
97 ShenandoahDisarmNMethodClosure _cl;
98 ShenandoahConcurrentNMethodIterator _iterator;
99
100 public:
101 ShenandoahDisarmNMethodsTask() :
102 WorkerTask("Shenandoah Disarm NMethods"),
103 _iterator(ShenandoahCodeRoots::table()) {
104 assert(SafepointSynchronize::is_at_safepoint(), "Only at a safepoint");
105 }
106
107 virtual void work(uint worker_id) {
108 ShenandoahParallelWorkerSession worker_session(worker_id);
109 _iterator.nmethods_do(&_cl);
110 }
111 };
112
113 void ShenandoahCodeRoots::disarm_nmethods() {
114 if (use_nmethod_barriers_for_mark()) {
115 ShenandoahDisarmNMethodsTask task;
116 ShenandoahHeap::heap()->workers()->run_task(&task);
117 }
118 }
119
120 class ShenandoahNMethodUnlinkClosure : public NMethodClosure {
121 private:
122 bool _unloading_occurred;
123 ShenandoahHeap* const _heap;
124 BarrierSetNMethod* const _bs;
125
126 public:
127 ShenandoahNMethodUnlinkClosure(bool unloading_occurred) :
128 _unloading_occurred(unloading_occurred),
129 _heap(ShenandoahHeap::heap()),
130 _bs(ShenandoahBarrierSet::barrier_set()->barrier_set_nmethod()) {}
131
132 virtual void do_nmethod(nmethod* nm) {
133 assert(_heap->is_concurrent_weak_root_in_progress(), "Only this phase");
134
135 ShenandoahNMethod* nm_data = ShenandoahNMethod::gc_data(nm);
136 assert(!nm_data->is_unregistered(), "Should not see unregistered entry");
137
138 if (nm->is_unloading()) {
139 ShenandoahNMethodLocker locker(nm_data->lock());
140 nm->unlink();
141 return;
142 }
143
144 {
145 ShenandoahNMethodLocker locker(nm_data->lock());
146
147 // Heal oops
148 if (_bs->is_armed(nm)) {
149 ShenandoahEvacOOMScope oom_evac_scope;
150 ShenandoahNMethod::heal_nmethod_metadata(nm_data);
151 // Must remain armed to complete remaining work in nmethod entry barrier
152 assert(_bs->is_armed(nm), "Should remain armed");
153 }
154 }
155
156 // Clear compiled ICs and exception caches
157 ShenandoahNMethodLocker locker(nm_data->ic_lock());
158 nm->unload_nmethod_caches(_unloading_occurred);
159 }
160 };
161
162 class ShenandoahUnlinkTask : public WorkerTask {
163 private:
164 ShenandoahNMethodUnlinkClosure _cl;
165 ShenandoahConcurrentNMethodIterator _iterator;
166
167 public:
168 ShenandoahUnlinkTask(bool unloading_occurred) :
169 WorkerTask("Shenandoah Unlink NMethods"),
170 _cl(unloading_occurred),
171 _iterator(ShenandoahCodeRoots::table()) {}
172
173 virtual void work(uint worker_id) {
174 _iterator.nmethods_do(&_cl);
175 }
176 };
177
178 void ShenandoahCodeRoots::unlink(WorkerThreads* workers, bool unloading_occurred) {
179 assert(ShenandoahHeap::heap()->unload_classes(), "Only when running concurrent class unloading");
180
181 ShenandoahUnlinkTask task(unloading_occurred);
182 workers->run_task(&task);
183 }
184
185 void ShenandoahCodeRoots::purge() {
186 assert(ShenandoahHeap::heap()->unload_classes(), "Only when running concurrent class unloading");
187
188 ClassUnloadingContext::context()->purge_and_free_nmethods();
189 }
190
191 ShenandoahCodeRootsIterator::ShenandoahCodeRootsIterator() :
192 _table_snapshot(nullptr) {
193 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint");
194 MutexLocker locker(CodeCache_lock, Mutex::_no_safepoint_check_flag);
195 _table_snapshot = ShenandoahCodeRoots::table()->snapshot_for_iteration();
196 }
197
198 ShenandoahCodeRootsIterator::~ShenandoahCodeRootsIterator() {
199 MonitorLocker locker(CodeCache_lock, Mutex::_no_safepoint_check_flag);
200 ShenandoahCodeRoots::table()->finish_iteration(_table_snapshot);
201 _table_snapshot = nullptr;
202 locker.notify_all();
203 }
204
205 void ShenandoahCodeRootsIterator::possibly_parallel_nmethods_do(NMethodClosure *f) {
206 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint");
207 assert(_table_snapshot != nullptr, "Sanity");
208 _table_snapshot->parallel_nmethods_do(f);
209 }