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 public:
  69   virtual bool is_unloading(CompiledMethod* method) const {
  70     nmethod* const nm = method->as_nmethod();
  71     ZReentrantLock* const lock = ZNMethod::lock_for_nmethod(nm);
  72     ZLocker<ZReentrantLock> locker(lock);
  73     ZIsUnloadingOopClosure cl;
  74     nm->oops_do(&cl, true /* allow_zombie */);
  75     return cl.is_unloading();
  76   }
  77 };
  78 
  79 class ZCompiledICProtectionBehaviour : public CompiledICProtectionBehaviour {
  80 public:
  81   virtual bool lock(CompiledMethod* method) {
  82     nmethod* const nm = method->as_nmethod();
  83     ZReentrantLock* const lock = ZNMethod::lock_for_nmethod(nm);
  84     lock->lock();
  85     return true;
  86   }
  87 
  88   virtual void unlock(CompiledMethod* method) {
  89     nmethod* const nm = method->as_nmethod();
  90     ZReentrantLock* const lock = ZNMethod::lock_for_nmethod(nm);
  91     lock->unlock();
  92   }
  93 
  94   virtual bool is_safe(CompiledMethod* method) {
  95     if (SafepointSynchronize::is_at_safepoint()) {
  96       return true;
  97     }
  98 
  99     nmethod* const nm = method->as_nmethod();
 100     ZReentrantLock* const lock = ZNMethod::lock_for_nmethod(nm);
 101     return lock->is_owned();
 102   }
 103 };
 104 
 105 ZUnload::ZUnload(ZWorkers* workers) :
 106     _workers(workers) {
 107 
 108   if (!ClassUnloading) {
 109     return;
 110   }
 111 
 112   static ZIsUnloadingBehaviour is_unloading_behaviour;
 113   IsUnloadingBehaviour::set_current(&is_unloading_behaviour);
 114 
 115   static ZCompiledICProtectionBehaviour ic_protection_behaviour;
 116   CompiledICProtectionBehaviour::set_current(&ic_protection_behaviour);
 117 }
 118 
 119 void ZUnload::prepare() {
 120   if (!ClassUnloading) {
 121     return;
 122   }
 123 
 124   CodeCache::increment_unloading_cycle();
 125   DependencyContext::cleaning_start();
 126 }
 127 
 128 void ZUnload::unlink() {
 129   SuspendibleThreadSetJoiner sts;
 130   bool unloading_occurred;
 131 
 132   {
 133     MutexLockerEx ml(ClassLoaderDataGraph_lock);
 134     unloading_occurred = SystemDictionary::do_unloading(ZStatPhase::timer());
 135   }
 136 
 137   Klass::clean_weak_klass_links(unloading_occurred);
 138 
 139   ZNMethod::unlink(_workers, unloading_occurred);
 140 
 141   DependencyContext::cleaning_end();
 142 }
 143 
 144 void ZUnload::purge() {
 145   {
 146     SuspendibleThreadSetJoiner sts;
 147     ZNMethod::purge(_workers);
 148   }
 149 
 150   ClassLoaderDataGraph::purge();
 151   CodeCache::purge_exception_caches();
 152 }
 153 
 154 class ZUnloadRendezvousClosure : public ThreadClosure {
 155 public:
 156   void do_thread(Thread* thread) {}
 157 };
 158 
 159 void ZUnload::unload() {
 160   if (!ClassUnloading) {
 161     return;
 162   }
 163 
 164   ZStatTimer timer(ZSubPhaseConcurrentClassesUnload);
 165 
 166   // Unlink stale metadata and nmethods
 167   unlink();
 168 
 169   // Make sure stale metadata and nmethods are no longer observable
 170   ZUnloadRendezvousClosure cl;
 171   Handshake::execute(&cl);
 172 
 173   // Purge stale metadata and nmethods that were unlinked
 174   purge();
 175 }
 176 
 177 void ZUnload::finish() {
 178   // Resize and verify metaspace
 179   MetaspaceGC::compute_new_size();
 180   MetaspaceUtils::verify_metrics();
 181 }