/*

 * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

#include "precompiled.hpp"

#include "classfile/classLoaderDataGraph.hpp"

#include "classfile/systemDictionary.hpp"

#include "code/codeBehaviours.hpp"

#include "code/codeCache.hpp"

#include "code/dependencyContext.hpp"

#include "gc/shared/gcBehaviours.hpp"

#include "gc/shared/suspendibleThreadSet.hpp"

#include "gc/z/zLock.inline.hpp"

#include "gc/z/zNMethod.hpp"

#include "gc/z/zOopClosures.hpp"

#include "gc/z/zStat.hpp"

#include "gc/z/zUnload.hpp"

#include "oops/access.inline.hpp"

static const ZStatSubPhase ZSubPhaseConcurrentClassesUnload("Concurrent Classes Unload");

class ZIsUnloadingOopClosure : public OopClosure {

private:

  ZPhantomIsAliveObjectClosure _is_alive;

  bool                         _is_unloading;

public:

  ZIsUnloadingOopClosure() :

      _is_alive(),

      _is_unloading(false) {}

  virtual void do_oop(oop* p) {

    const oop o = RawAccess<>::oop_load(p);

    if (o != NULL && !_is_alive.do_object_b(o)) {

      _is_unloading = true;

    }

  }

  virtual void do_oop(narrowOop* p) {

    ShouldNotReachHere();

  }

  bool is_unloading() const {

    return _is_unloading;

  }

};

class ZIsUnloadingBehaviour : public IsUnloadingBehaviour {

public:

  virtual bool is_unloading(CompiledMethod* method) const {

    nmethod* const nm = method->as_nmethod();

    ZReentrantLock* const lock = ZNMethod::lock_for_nmethod(nm);

    ZLocker<ZReentrantLock> locker(lock);

    ZIsUnloadingOopClosure cl;

    ZNMethod::nmethod_oops_do(nm, &cl);

    return cl.is_unloading();

  }

};

class ZCompiledICProtectionBehaviour : public CompiledICProtectionBehaviour {

public:

  virtual bool lock(CompiledMethod* method) {

    nmethod* const nm = method->as_nmethod();

    ZReentrantLock* const lock = ZNMethod::lock_for_nmethod(nm);

    lock->lock();

    return true;

  }

  virtual void unlock(CompiledMethod* method) {

    nmethod* const nm = method->as_nmethod();

    ZReentrantLock* const lock = ZNMethod::lock_for_nmethod(nm);

    lock->unlock();

  }

  virtual bool is_safe(CompiledMethod* method) {

    if (SafepointSynchronize::is_at_safepoint()) {

      return true;

    }

    nmethod* const nm = method->as_nmethod();

    ZReentrantLock* const lock = ZNMethod::lock_for_nmethod(nm);

    return lock->is_owned();

  }

};

ZUnload::ZUnload(ZWorkers* workers) :

    _workers(workers) {

  if (!ClassUnloading) {

    return;

  }

  static ZIsUnloadingBehaviour is_unloading_behaviour;

  IsUnloadingBehaviour::set_current(&is_unloading_behaviour);

  static ZCompiledICProtectionBehaviour ic_protection_behaviour;

  CompiledICProtectionBehaviour::set_current(&ic_protection_behaviour);

}

void ZUnload::prepare() {

  if (!ClassUnloading) {

    return;

  }

  CodeCache::increment_unloading_cycle();

  DependencyContext::cleaning_start();

}

void ZUnload::unlink() {

  SuspendibleThreadSetJoiner sts;

  bool unloading_occurred;

  {

    MutexLocker ml(ClassLoaderDataGraph_lock);

    unloading_occurred = SystemDictionary::do_unloading(ZStatPhase::timer());

  }

  Klass::clean_weak_klass_links(unloading_occurred);

  ZNMethod::unlink(_workers, unloading_occurred);

  DependencyContext::cleaning_end();

}

void ZUnload::purge() {

  {

    SuspendibleThreadSetJoiner sts;

    ZNMethod::purge(_workers);

  }

  ClassLoaderDataGraph::purge();

  CodeCache::purge_exception_caches();

}

class ZUnloadRendezvousClosure : public ThreadClosure {

public:

  void do_thread(Thread* thread) {}

};

void ZUnload::unload() {

  if (!ClassUnloading) {

    return;

  }

  ZStatTimer timer(ZSubPhaseConcurrentClassesUnload);

  // Unlink stale metadata and nmethods

  unlink();

  // Make sure stale metadata and nmethods are no longer observable

  ZUnloadRendezvousClosure cl;

  Handshake::execute(&cl);

  // Purge stale metadata and nmethods that were unlinked

  purge();

}

void ZUnload::finish() {

  // Resize and verify metaspace

  MetaspaceGC::compute_new_size();

  MetaspaceUtils::verify_metrics();

}