1 /*
2 * Copyright (c) 2024, 2025, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2019, 2021, 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.
23 *
24 */
25
26
27 #include "classfile/classLoaderDataGraph.hpp"
28 #include "classfile/systemDictionary.hpp"
29 #include "code/codeBehaviours.hpp"
30 #include "code/codeCache.hpp"
31 #include "code/dependencyContext.hpp"
32 #include "gc/shared/classUnloadingContext.hpp"
33 #include "gc/shared/gcBehaviours.hpp"
34 #include "gc/shared/suspendibleThreadSet.hpp"
35 #include "gc/shenandoah/shenandoahLock.hpp"
36 #include "gc/shenandoah/shenandoahNMethod.inline.hpp"
37 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
38 #include "gc/shenandoah/shenandoahRootProcessor.hpp"
39 #include "gc/shenandoah/shenandoahUnload.hpp"
40 #include "gc/shenandoah/shenandoahVerifier.hpp"
41 #include "memory/iterator.hpp"
42 #include "memory/metaspaceUtils.hpp"
43 #include "memory/resourceArea.hpp"
44 #include "oops/access.inline.hpp"
45
46 class ShenandoahIsUnloadingOopClosure : public OopClosure {
47 private:
48 ShenandoahMarkingContext* const _marking_context;
49 bool _is_unloading;
50
51 public:
52 ShenandoahIsUnloadingOopClosure() :
53 _marking_context(ShenandoahHeap::heap()->global_generation()->complete_marking_context()),
54 _is_unloading(false) {
55 }
56
57 virtual void do_oop(oop* p) {
58 if (_is_unloading) {
59 return;
60 }
61
62 const oop o = RawAccess<>::oop_load(p);
63 if (!CompressedOops::is_null(o) &&
64 !_marking_context->is_marked(o)) {
65 _is_unloading = true;
66 }
67 }
68
69 virtual void do_oop(narrowOop* p) {
70 ShouldNotReachHere();
71 }
72
73 bool is_unloading() const {
74 return _is_unloading;
75 }
76 };
77
78 class ShenandoahIsUnloadingBehaviour : public IsUnloadingBehaviour {
79 public:
80 virtual bool has_dead_oop(nmethod* nm) const {
81 assert(ShenandoahHeap::heap()->is_concurrent_weak_root_in_progress(), "Only for this phase");
82 ShenandoahNMethod* data = ShenandoahNMethod::gc_data(nm);
83 ShenandoahNMethodLocker locker(data->lock());
84 ShenandoahIsUnloadingOopClosure cl;
85 data->oops_do(&cl, /* fix_relocations = */ false, /* icic = */ nullptr);
86 return cl.is_unloading();
87 }
88 };
89
90 class ShenandoahCompiledICProtectionBehaviour : public CompiledICProtectionBehaviour {
91 public:
92 virtual bool lock(nmethod* nm) {
93 ShenandoahNMethodLock* const lock = ShenandoahNMethod::ic_lock_for_nmethod(nm);
94 assert(lock != nullptr, "Not yet registered?");
95 lock->lock();
96 return true;
97 }
98
99 virtual void unlock(nmethod* nm) {
100 ShenandoahNMethodLock* const lock = ShenandoahNMethod::ic_lock_for_nmethod(nm);
101 assert(lock != nullptr, "Not yet registered?");
102 lock->unlock();
103 }
104
105 virtual bool is_safe(nmethod* nm) {
106 if (SafepointSynchronize::is_at_safepoint() || nm->is_unloading() || (NMethodState_lock->owned_by_self() && nm->is_not_installed())) {
107 return true;
108 }
109
110 ShenandoahNMethodLock* const lock = ShenandoahNMethod::ic_lock_for_nmethod(nm);
111 assert(lock != nullptr, "Not yet registered?");
112 return lock->owned_by_self();
113 }
114 };
115
116 ShenandoahUnload::ShenandoahUnload() {
117 if (ClassUnloading) {
118 static ShenandoahIsUnloadingBehaviour is_unloading_behaviour;
119 IsUnloadingBehaviour::set_current(&is_unloading_behaviour);
120
121 static ShenandoahCompiledICProtectionBehaviour ic_protection_behaviour;
122 CompiledICProtectionBehaviour::set_current(&ic_protection_behaviour);
123 }
124 }
125
126 void ShenandoahUnload::prepare() {
127 assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");
128 assert(ClassUnloading, "Sanity");
129 CodeCache::increment_unloading_cycle();
130 DependencyContext::cleaning_start();
131 }
132
133 void ShenandoahUnload::unload() {
134 ShenandoahHeap* heap = ShenandoahHeap::heap();
135 assert(ClassUnloading, "Filtered by caller");
136 assert(heap->is_concurrent_weak_root_in_progress(), "Filtered by caller");
137
138 ClassUnloadingContext ctx(heap->workers()->active_workers(),
139 true /* unregister_nmethods_during_purge */,
140 true /* lock_nmethod_free_separately */);
141
142 // Unlink stale metadata and nmethods
143 {
144 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_unlink);
145
146 SuspendibleThreadSetJoiner sts;
147 bool unloadingOccurred;
148 {
149 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_unlink_sd);
150 MutexLocker cldgMl(ClassLoaderDataGraph_lock);
151 unloadingOccurred = SystemDictionary::do_unloading(heap->gc_timer());
152 }
153
154 {
155 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_unlink_weak_klass);
156 Klass::clean_weak_klass_links(unloadingOccurred);
157 }
158
159 {
160 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_unlink_code_roots);
161 ShenandoahCodeRoots::unlink(heap->workers(), unloadingOccurred);
162 }
163
164 DependencyContext::cleaning_end();
165 }
166
167 // Make sure stale metadata and nmethods are no longer observable
168 {
169 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_rendezvous);
170 heap->rendezvous_threads("Shenandoah Class Unloading");
171 }
172
173 // Purge stale metadata and nmethods that were unlinked
174 {
175 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_purge);
176
177 {
178 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_purge_coderoots);
179 SuspendibleThreadSetJoiner sts;
180 ShenandoahCodeRoots::purge();
181 }
182
183 {
184 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_purge_cldg);
185 ClassLoaderDataGraph::purge(false /* at_safepoint */);
186 }
187
188 {
189 ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_purge_ec);
190 CodeCache::purge_exception_caches();
191 }
192 }
193 }
194
195 void ShenandoahUnload::finish() {
196 MetaspaceGC::compute_new_size();
197 DEBUG_ONLY(MetaspaceUtils::verify();)
198 }