1 /*
   2  * Copyright (c) 2019, Red Hat, Inc. All rights reserved.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This code is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  11  * version 2 for more details (a copy is included in the LICENSE file that
  12  * accompanied this code).
  13  *
  14  * You should have received a copy of the GNU General Public License version
  15  * 2 along with this work; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  19  * or visit www.oracle.com if you need additional information or have any
  20  * questions.
  21  *
  22  */
  23 
  24 #include "precompiled.hpp"
  25 
  26 #include "classfile/classLoaderDataGraph.hpp"
  27 #include "classfile/systemDictionary.hpp"
  28 #include "code/codeBehaviours.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/dependencyContext.hpp"
  31 #include "gc/shared/gcBehaviours.hpp"
  32 #include "gc/shared/suspendibleThreadSet.hpp"
  33 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
  34 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
  35 #include "gc/shenandoah/shenandoahConcurrentRoots.hpp"
  36 #include "gc/shenandoah/shenandoahNMethod.inline.hpp"
  37 #include "gc/shenandoah/shenandoahLock.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/resourceArea.hpp"
  43 #include "oops/access.inline.hpp"
  44 
  45 class ShenandoahIsUnloadingOopClosure : public OopClosure {
  46 private:
  47   ShenandoahMarkingContext*    _marking_context;
  48   bool                         _is_unloading;
  49 
  50 public:
  51   ShenandoahIsUnloadingOopClosure() :
  52     _marking_context(ShenandoahHeap::heap()->marking_context()),
  53     _is_unloading(false) {
  54   }
  55 
  56   virtual void do_oop(oop* p) {
  57     if (_is_unloading) {
  58       return;
  59     }
  60 
  61     const oop o = RawAccess<>::oop_load(p);
  62     if (!CompressedOops::is_null(o) &&
  63         _marking_context->is_complete() &&
  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 is_unloading(CompiledMethod* method) const {
  81     nmethod* const nm = method->as_nmethod();
  82     guarantee(ShenandoahHeap::heap()->is_evacuation_in_progress(), "Only this phase");
  83     ShenandoahNMethod* data = ShenandoahNMethod::gc_data(nm);
  84     ShenandoahReentrantLocker locker(data->lock());
  85     ShenandoahIsUnloadingOopClosure cl;
  86     data->oops_do(&cl);
  87     return  cl.is_unloading();
  88   }
  89 };
  90 
  91 class ShenandoahCompiledICProtectionBehaviour : public CompiledICProtectionBehaviour {
  92 public:
  93   virtual bool lock(CompiledMethod* method) {
  94     nmethod* const nm = method->as_nmethod();
  95     ShenandoahReentrantLock* const lock = ShenandoahNMethod::lock_for_nmethod(nm);
  96     assert(lock != NULL, "Not yet registered?");
  97     lock->lock();
  98     return true;
  99   }
 100 
 101   virtual void unlock(CompiledMethod* method) {
 102     nmethod* const nm = method->as_nmethod();
 103     ShenandoahReentrantLock* const lock = ShenandoahNMethod::lock_for_nmethod(nm);
 104     assert(lock != NULL, "Not yet registered?");
 105     lock->unlock();
 106   }
 107 
 108   virtual bool is_safe(CompiledMethod* method) {
 109     if (SafepointSynchronize::is_at_safepoint()) {
 110       return true;
 111     }
 112 
 113     nmethod* const nm = method->as_nmethod();
 114     ShenandoahReentrantLock* const lock = ShenandoahNMethod::lock_for_nmethod(nm);
 115     assert(lock != NULL, "Not yet registered?");
 116     return lock->owned_by_self();
 117   }
 118 };
 119 
 120 ShenandoahUnload::ShenandoahUnload() {
 121   if (ShenandoahConcurrentRoots::can_do_concurrent_class_unloading()) {
 122     static ShenandoahIsUnloadingBehaviour is_unloading_behaviour;
 123     IsUnloadingBehaviour::set_current(&is_unloading_behaviour);
 124 
 125     static ShenandoahCompiledICProtectionBehaviour ic_protection_behaviour;
 126     CompiledICProtectionBehaviour::set_current(&ic_protection_behaviour);
 127   }
 128 }
 129 
 130 void ShenandoahUnload::prepare() {
 131   assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");
 132   assert(ShenandoahConcurrentRoots::can_do_concurrent_class_unloading(), "Sanity");
 133   CodeCache::increment_unloading_cycle();
 134   DependencyContext::cleaning_start();
 135 }
 136 
 137 void ShenandoahUnload::unlink() {
 138   SuspendibleThreadSetJoiner sts;
 139   bool unloading_occurred;
 140   ShenandoahHeap* const heap = ShenandoahHeap::heap();
 141   {
 142     MutexLocker cldg_ml(ClassLoaderDataGraph_lock);
 143     unloading_occurred = SystemDictionary::do_unloading(heap->gc_timer());
 144   }
 145 
 146   Klass::clean_weak_klass_links(unloading_occurred);
 147   ShenandoahCodeRoots::unlink(ShenandoahHeap::heap()->workers(), unloading_occurred);
 148   DependencyContext::cleaning_end();
 149 }
 150 
 151 void ShenandoahUnload::purge() {
 152   {
 153     SuspendibleThreadSetJoiner sts;
 154     ShenandoahCodeRoots::purge(ShenandoahHeap::heap()->workers());
 155   }
 156 
 157   ClassLoaderDataGraph::purge();
 158   CodeCache::purge_exception_caches();
 159 }
 160 
 161 class ShenandoahUnloadRendezvousClosure : public ThreadClosure {
 162 public:
 163   void do_thread(Thread* thread) {}
 164 };
 165 
 166 void ShenandoahUnload::unload() {
 167   assert(ShenandoahConcurrentRoots::can_do_concurrent_class_unloading(), "Why we here?");
 168   if (!ShenandoahHeap::heap()->is_evacuation_in_progress()) {
 169     return;
 170   }
 171 
 172   // Unlink stale metadata and nmethods
 173   unlink();
 174 
 175   // Make sure stale metadata and nmethods are no longer observable
 176   ShenandoahUnloadRendezvousClosure cl;
 177   Handshake::execute(&cl);
 178 
 179   // Purge stale metadata and nmethods that were unlinked
 180   purge();
 181 }
 182 
 183 void ShenandoahUnload::finish() {
 184   MetaspaceGC::compute_new_size();
 185   MetaspaceUtils::verify_metrics();
 186 }