1 /*
  2  * Copyright (c) 2018, 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 "classfile/classLoaderDataGraph.hpp"
 26 #include "classfile/systemDictionary.hpp"
 27 #include "code/codeBehaviours.hpp"
 28 #include "code/codeCache.hpp"
 29 #include "code/dependencyContext.hpp"
 30 #include "gc/shared/gcBehaviours.hpp"
 31 #include "gc/shared/suspendibleThreadSet.hpp"
 32 #include "gc/z/zLock.inline.hpp"
 33 #include "gc/z/zNMethod.hpp"
 34 #include "gc/z/zOopClosures.hpp"
 35 #include "gc/z/zStat.hpp"
 36 #include "gc/z/zUnload.hpp"
 37 #include "oops/access.inline.hpp"
 38 
 39 static const ZStatSubPhase ZSubPhaseConcurrentClassesUnload("Concurrent Classes Unload");
 40 
 41 class ZIsUnloadingOopClosure : public OopClosure {
 42 private:
 43   ZPhantomIsAliveObjectClosure _is_alive;
 44   bool                         _is_unloading;
 45 
 46 public:
 47   ZIsUnloadingOopClosure() :
 48       _is_alive(),
 49       _is_unloading(false) {}
 50 
 51   virtual void do_oop(oop* p) {
 52     const oop o = RawAccess<>::oop_load(p);
 53     if (o != NULL && !_is_alive.do_object_b(o)) {
 54       _is_unloading = true;
 55     }
 56   }
 57 
 58   virtual void do_oop(narrowOop* p) {
 59     ShouldNotReachHere();
 60   }
 61 
 62   bool is_unloading() const {
 63     return _is_unloading;
 64   }
 65 };
 66 
 67 class ZIsUnloadingBehaviour : public IsUnloadingBehaviour {
 68 private:
 69   bool is_unloading(nmethod* nm) const {
 70     ZIsUnloadingOopClosure cl;
 71     nm->oops_do(&cl, true /* allow_zombie */);
 72     return cl.is_unloading();
 73   }
 74 
 75 public:
 76   virtual bool is_unloading(CompiledMethod* method) const {
 77     nmethod* const nm = method->as_nmethod();
 78     ZReentrantLock* const lock = ZNMethod::lock_for_nmethod(nm);
 79     if (lock == NULL) {
 80       return is_unloading(nm);
 81     } else {
 82       ZLocker<ZReentrantLock> locker(lock);
 83       return is_unloading(nm);
 84     }
 85   }
 86 };
 87 
 88 class ZCompiledICProtectionBehaviour : public CompiledICProtectionBehaviour {
 89 public:
 90   virtual bool lock(CompiledMethod* method) {
 91     nmethod* const nm = method->as_nmethod();
 92     ZReentrantLock* const lock = ZNMethod::lock_for_nmethod(nm);
 93     if (lock != NULL) {
 94       lock->lock();
 95     }
 96     return true;
 97   }
 98 
 99   virtual void unlock(CompiledMethod* method) {
100     nmethod* const nm = method->as_nmethod();
101     ZReentrantLock* const lock = ZNMethod::lock_for_nmethod(nm);
102     if (lock != NULL) {
103       lock->unlock();
104     }
105   }
106 
107   virtual bool is_safe(CompiledMethod* method) {
108     if (SafepointSynchronize::is_at_safepoint()) {
109       return true;
110     }
111 
112     nmethod* const nm = method->as_nmethod();
113     ZReentrantLock* const lock = ZNMethod::lock_for_nmethod(nm);
114     return lock == NULL || lock->is_owned();
115   }
116 };
117 
118 ZUnload::ZUnload(ZWorkers* workers) :
119     _workers(workers) {
120 
121   if (!ClassUnloading) {
122     return;
123   }
124 
125   static ZIsUnloadingBehaviour is_unloading_behaviour;
126   IsUnloadingBehaviour::set_current(&is_unloading_behaviour);
127 
128   static ZCompiledICProtectionBehaviour ic_protection_behaviour;
129   CompiledICProtectionBehaviour::set_current(&ic_protection_behaviour);
130 }
131 
132 void ZUnload::prepare() {
133   if (!ClassUnloading) {
134     return;
135   }
136 
137   CodeCache::increment_unloading_cycle();
138   DependencyContext::cleaning_start();
139 }
140 
141 void ZUnload::unlink() {
142   SuspendibleThreadSetJoiner sts;
143   bool unloading_occurred;
144 
145   {
146     MutexLockerEx ml(ClassLoaderDataGraph_lock);
147     unloading_occurred = SystemDictionary::do_unloading(ZStatPhase::timer());
148   }
149 
150   Klass::clean_weak_klass_links(unloading_occurred);
151 
152   ZNMethod::unlink(_workers, unloading_occurred);
153 
154   DependencyContext::cleaning_end();
155 }
156 
157 void ZUnload::purge() {
158   {
159     SuspendibleThreadSetJoiner sts;
160     ZNMethod::purge(_workers);
161   }
162 
163   ClassLoaderDataGraph::purge();
164   CodeCache::purge_exception_caches();
165 }
166 
167 class ZUnloadRendezvousClosure : public ThreadClosure {
168 public:
169   void do_thread(Thread* thread) {}
170 };
171 
172 void ZUnload::unload() {
173   if (!ClassUnloading) {
174     return;
175   }
176 
177   ZStatTimer timer(ZSubPhaseConcurrentClassesUnload);
178 
179   // Unlink stale metadata and nmethods
180   unlink();
181 
182   // Make sure stale metadata and nmethods are no longer observable
183   ZUnloadRendezvousClosure cl;
184   Handshake::execute(&cl);
185 
186   // Purge stale metadata and nmethods that were unlinked
187   purge();
188 }
189 
190 void ZUnload::finish() {
191   // Resize and verify metaspace
192   MetaspaceGC::compute_new_size();
193   MetaspaceUtils::verify_metrics();
194 }