/*

 * Copyright (c) 2019, Red Hat, Inc. All rights reserved.

 *

 * 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/shenandoah/shenandoahClosures.inline.hpp"

#include "gc/shenandoah/shenandoahCodeRoots.hpp"

#include "gc/shenandoah/shenandoahConcurrentRoots.hpp"

#include "gc/shenandoah/shenandoahNMethod.inline.hpp"

#include "gc/shenandoah/shenandoahLock.hpp"

#include "gc/shenandoah/shenandoahRootProcessor.hpp"

#include "gc/shenandoah/shenandoahUnload.hpp"

#include "gc/shenandoah/shenandoahVerifier.hpp"

#include "memory/iterator.hpp"

#include "memory/resourceArea.hpp"

#include "oops/access.inline.hpp"

class ShenandoahIsUnloadingOopClosure : public OopClosure {

private:

  ShenandoahMarkingContext*    _marking_context;

  bool                         _is_unloading;

public:

  ShenandoahIsUnloadingOopClosure() :

    _marking_context(ShenandoahHeap::heap()->marking_context()),

    _is_unloading(false) {

  }

  virtual void do_oop(oop* p) {

    if (_is_unloading) {

      return;

    }

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

    if (!CompressedOops::is_null(o) &&

        _marking_context->is_complete() &&

        !_marking_context->is_marked(o)) {

      _is_unloading = true;

    }

  }

  virtual void do_oop(narrowOop* p) {

    ShouldNotReachHere();

  }

  bool is_unloading() const {

    return _is_unloading;

  }

};

class ShenandoahIsUnloadingBehaviour : public IsUnloadingBehaviour {

public:

  virtual bool is_unloading(CompiledMethod* method) const {

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

    guarantee(ShenandoahHeap::heap()->is_evacuation_in_progress(), "Only this phase");

    ShenandoahNMethod* data = ShenandoahNMethod::gc_data(nm);

    ShenandoahReentrantLocker locker(data->lock());

    ShenandoahIsUnloadingOopClosure cl;

    data->oops_do(&cl);

    return  cl.is_unloading();

  }

};

class ShenandoahCompiledICProtectionBehaviour : public CompiledICProtectionBehaviour {

public:

  virtual bool lock(CompiledMethod* method) {

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

    ShenandoahReentrantLock* const lock = ShenandoahNMethod::lock_for_nmethod(nm);

    assert(lock != NULL, "Not yet registered?");

    lock->lock();

    return true;

  }

  virtual void unlock(CompiledMethod* method) {

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

    ShenandoahReentrantLock* const lock = ShenandoahNMethod::lock_for_nmethod(nm);

    assert(lock != NULL, "Not yet registered?");

    lock->unlock();

  }

  virtual bool is_safe(CompiledMethod* method) {

    if (SafepointSynchronize::is_at_safepoint()) {

      return true;

    }

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

    ShenandoahReentrantLock* const lock = ShenandoahNMethod::lock_for_nmethod(nm);

    assert(lock != NULL, "Not yet registered?");

    return lock->owned_by_self();

  }

};

ShenandoahUnload::ShenandoahUnload() {

  if (ShenandoahConcurrentRoots::can_do_concurrent_class_unloading()) {

    static ShenandoahIsUnloadingBehaviour is_unloading_behaviour;

    IsUnloadingBehaviour::set_current(&is_unloading_behaviour);

    static ShenandoahCompiledICProtectionBehaviour ic_protection_behaviour;

    CompiledICProtectionBehaviour::set_current(&ic_protection_behaviour);

  }

}

void ShenandoahUnload::prepare() {

  assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");

  assert(ShenandoahConcurrentRoots::can_do_concurrent_class_unloading(), "Sanity");

  CodeCache::increment_unloading_cycle();

  DependencyContext::cleaning_start();

}

void ShenandoahUnload::unlink() {

  SuspendibleThreadSetJoiner sts;

  bool unloading_occurred;

  ShenandoahHeap* const heap = ShenandoahHeap::heap();

  {

    MutexLocker cldg_ml(ClassLoaderDataGraph_lock);

    unloading_occurred = SystemDictionary::do_unloading(heap->gc_timer());

  }

  Klass::clean_weak_klass_links(unloading_occurred);

  ShenandoahCodeRoots::unlink(ShenandoahHeap::heap()->workers(), unloading_occurred);

  DependencyContext::cleaning_end();

}

void ShenandoahUnload::purge() {

  {

    SuspendibleThreadSetJoiner sts;

    ShenandoahCodeRoots::purge(ShenandoahHeap::heap()->workers());

  }

  ClassLoaderDataGraph::purge();

  CodeCache::purge_exception_caches();

}

class ShenandoahUnloadRendezvousClosure : public ThreadClosure {

public:

  void do_thread(Thread* thread) {}

};

void ShenandoahUnload::unload() {

  assert(ShenandoahConcurrentRoots::can_do_concurrent_class_unloading(), "Why we here?");

  if (!ShenandoahHeap::heap()->is_evacuation_in_progress()) {

    return;

  }

  // Unlink stale metadata and nmethods

  unlink();

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

  ShenandoahUnloadRendezvousClosure cl;

  Handshake::execute(&cl);

  // Purge stale metadata and nmethods that were unlinked

  purge();

}

void ShenandoahUnload::finish() {

  MetaspaceGC::compute_new_size();

  MetaspaceUtils::verify_metrics();

}