1 /*
  2  * Copyright (c) 2019, 2021, Red Hat, Inc. 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 
 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/gcBehaviours.hpp"
 33 #include "gc/shared/classUnloadingContext.hpp"
 34 #include "gc/shared/suspendibleThreadSet.hpp"
 35 #include "gc/shenandoah/shenandoahNMethod.inline.hpp"
 36 #include "gc/shenandoah/shenandoahLock.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     // TODO: In non-generational mode, this should still be complete_marking_context()
 54     _marking_context(ShenandoahHeap::heap()->marking_context()),
 55     _is_unloading(false) {
 56   }
 57 
 58   virtual void do_oop(oop* p) {
 59     if (_is_unloading) {
 60       return;
 61     }
 62 
 63     const oop o = RawAccess<>::oop_load(p);
 64     if (!CompressedOops::is_null(o) &&
 65         !_marking_context->is_marked(o)) {
 66       _is_unloading = true;
 67     }
 68   }
 69 
 70   virtual void do_oop(narrowOop* p) {
 71     ShouldNotReachHere();
 72   }
 73 
 74   bool is_unloading() const {
 75     return _is_unloading;
 76   }
 77 };
 78 
 79 class ShenandoahIsUnloadingBehaviour : public IsUnloadingBehaviour {
 80 public:
 81   virtual bool has_dead_oop(CompiledMethod* method) const {
 82     nmethod* const nm = method->as_nmethod();
 83     assert(ShenandoahHeap::heap()->is_concurrent_weak_root_in_progress(), "Only for this phase");
 84     ShenandoahNMethod* data = ShenandoahNMethod::gc_data(nm);
 85     ShenandoahReentrantLocker locker(data->lock());
 86     ShenandoahIsUnloadingOopClosure cl;
 87     data->oops_do(&cl);
 88     return  cl.is_unloading();
 89   }
 90 };
 91 
 92 class ShenandoahCompiledICProtectionBehaviour : public CompiledICProtectionBehaviour {
 93 public:
 94   virtual bool lock(CompiledMethod* method) {
 95     nmethod* const nm = method->as_nmethod();
 96     ShenandoahReentrantLock* const lock = ShenandoahNMethod::lock_for_nmethod(nm);
 97     assert(lock != nullptr, "Not yet registered?");
 98     lock->lock();
 99     return true;
100   }
101 
102   virtual void unlock(CompiledMethod* method) {
103     nmethod* const nm = method->as_nmethod();
104     ShenandoahReentrantLock* const lock = ShenandoahNMethod::lock_for_nmethod(nm);
105     assert(lock != nullptr, "Not yet registered?");
106     lock->unlock();
107   }
108 
109   virtual bool is_safe(CompiledMethod* method) {
110     if (SafepointSynchronize::is_at_safepoint() || method->is_unloading()) {
111       return true;
112     }
113 
114     nmethod* const nm = method->as_nmethod();
115     ShenandoahReentrantLock* const lock = ShenandoahNMethod::lock_for_nmethod(nm);
116     assert(lock != nullptr, "Not yet registered?");
117     return lock->owned_by_self();
118   }
119 };
120 
121 ShenandoahUnload::ShenandoahUnload() {
122   if (ClassUnloading) {
123     static ShenandoahIsUnloadingBehaviour is_unloading_behaviour;
124     IsUnloadingBehaviour::set_current(&is_unloading_behaviour);
125 
126     static ShenandoahCompiledICProtectionBehaviour ic_protection_behaviour;
127     CompiledICProtectionBehaviour::set_current(&ic_protection_behaviour);
128   }
129 }
130 
131 void ShenandoahUnload::prepare() {
132   assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");
133   assert(ClassUnloading, "Sanity");
134   CodeCache::increment_unloading_cycle();
135   DependencyContext::cleaning_start();
136 }
137 
138 void ShenandoahUnload::unload() {
139   ShenandoahHeap* heap = ShenandoahHeap::heap();
140   assert(ClassUnloading, "Filtered by caller");
141   assert(heap->is_concurrent_weak_root_in_progress(), "Filtered by caller");
142 
143   ClassUnloadingContext ctx(heap->workers()->active_workers(),
144                             true /* unregister_nmethods_during_purge */,
145                             true /* lock_codeblob_free_separately */);
146 
147   // Unlink stale metadata and nmethods
148   {
149     ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_unlink);
150 
151     SuspendibleThreadSetJoiner sts;
152     bool unloadingOccurred;
153     {
154       ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_unlink_sd);
155       MutexLocker cldgMl(ClassLoaderDataGraph_lock);
156       unloadingOccurred = SystemDictionary::do_unloading(heap->gc_timer());
157     }
158 
159     {
160       ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_unlink_weak_klass);
161       Klass::clean_weak_klass_links(unloadingOccurred);
162     }
163 
164     {
165       ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_unlink_code_roots);
166       ShenandoahCodeRoots::unlink(heap->workers(), unloadingOccurred);
167     }
168 
169     DependencyContext::cleaning_end();
170   }
171 
172   // Make sure stale metadata and nmethods are no longer observable
173   {
174     ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_rendezvous);
175     heap->rendezvous_threads();
176   }
177 
178   // Purge stale metadata and nmethods that were unlinked
179   {
180     ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_purge);
181 
182     {
183       ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_purge_coderoots);
184       SuspendibleThreadSetJoiner sts;
185       ShenandoahCodeRoots::purge();
186     }
187 
188     {
189       ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_purge_cldg);
190       ClassLoaderDataGraph::purge(false /* at_safepoint */);
191     }
192 
193     {
194       ShenandoahTimingsTracker t(ShenandoahPhaseTimings::conc_class_unload_purge_ec);
195       CodeCache::purge_exception_caches();
196     }
197   }
198 }
199 
200 void ShenandoahUnload::finish() {
201   MetaspaceGC::compute_new_size();
202   DEBUG_ONLY(MetaspaceUtils::verify();)
203 }
--- EOF ---