/*

 * Copyright (c) 2015, 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

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 */

#include "precompiled.hpp"

#include "aot/aotLoader.hpp"

#include "classfile/classLoaderDataGraph.hpp"

#include "classfile/stringTable.hpp"

#include "classfile/systemDictionary.hpp"

#include "code/codeCache.hpp"

#include "gc/g1/g1BarrierSet.hpp"

#include "gc/g1/g1CodeBlobClosure.hpp"

#include "gc/g1/g1CollectedHeap.inline.hpp"

#include "gc/g1/g1CollectorState.hpp"

#include "gc/g1/g1GCPhaseTimes.hpp"

#include "gc/g1/g1ParScanThreadState.inline.hpp"

#include "gc/g1/g1Policy.hpp"

#include "gc/g1/g1RootClosures.hpp"

#include "gc/g1/g1RootProcessor.hpp"

#include "gc/g1/heapRegion.inline.hpp"

#include "gc/shared/referenceProcessor.hpp"

#include "memory/allocation.inline.hpp"

#include "memory/universe.hpp"

#include "runtime/mutex.hpp"

#include "services/management.hpp"

#include "utilities/macros.hpp"

void G1RootProcessor::worker_has_discovered_all_strong_nmethods() {

  assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");

  uint new_value = (uint)Atomic::add(1, &_n_workers_discovered_strong_classes);

  if (new_value == n_workers()) {

    // This thread is last. Notify the others.

    MonitorLocker ml(&_lock, Mutex::_no_safepoint_check_flag);

    _lock.notify_all();

  }

}

void G1RootProcessor::wait_until_all_strong_nmethods_discovered() {

  assert(ClassUnloadingWithConcurrentMark, "Currently only needed when doing G1 Class Unloading");

  if ((uint)_n_workers_discovered_strong_classes != n_workers()) {

    MonitorLocker ml(&_lock, Mutex::_no_safepoint_check_flag);

    while ((uint)_n_workers_discovered_strong_classes != n_workers()) {

      ml.wait(0);

    }

  }

}

G1RootProcessor::G1RootProcessor(G1CollectedHeap* g1h, uint n_workers) :

    _g1h(g1h),

    _process_strong_tasks(G1RP_PS_NumElements),

    _srs(n_workers),

    _lock(Mutex::leaf, "G1 Root Scan barrier lock", false, Mutex::_safepoint_check_never),

    _n_workers_discovered_strong_classes(0) {}

void G1RootProcessor::evacuate_roots(G1ParScanThreadState* pss, uint worker_id) {

  G1GCPhaseTimes* phase_times = _g1h->phase_times();

  G1EvacPhaseTimesTracker timer(phase_times, pss, G1GCPhaseTimes::ExtRootScan, worker_id);

  G1EvacuationRootClosures* closures = pss->closures();

  process_java_roots(closures, phase_times, worker_id, closures->trace_metadata() /* notify_claimed_nmethods_done */);

  process_vm_roots(closures, phase_times, worker_id);

  {

    // Now the CM ref_processor roots.

    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CMRefRoots, worker_id);

    if (_process_strong_tasks.try_claim_task(G1RP_PS_refProcessor_oops_do)) {

      // We need to treat the discovered reference lists of the

      // concurrent mark ref processor as roots and keep entries

      // (which are added by the marking threads) on them live

      // until they can be processed at the end of marking.

      _g1h->ref_processor_cm()->weak_oops_do(closures->strong_oops());

    }

  }

  if (closures->trace_metadata()) {

    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::WaitForStrongRoots, worker_id);

    // Wait to make sure all workers passed the strong nmethods phase.

    wait_until_all_strong_nmethods_discovered();

  }

  _process_strong_tasks.all_tasks_completed(n_workers());

}

// Adaptor to pass the closures to the strong roots in the VM.

class StrongRootsClosures : public G1RootClosures {

  OopClosure* _roots;

  CLDClosure* _clds;

  CodeBlobClosure* _blobs;

public:

  StrongRootsClosures(OopClosure* roots, CLDClosure* clds, CodeBlobClosure* blobs) :

      _roots(roots), _clds(clds), _blobs(blobs) {}

  OopClosure* weak_oops()   { return NULL; }

  OopClosure* strong_oops() { return _roots; }

  CLDClosure* weak_clds()        { return NULL; }

  CLDClosure* strong_clds()      { return _clds; }

  CodeBlobClosure* strong_codeblobs() { return _blobs; }

};

void G1RootProcessor::process_strong_roots(OopClosure* oops,

                                           CLDClosure* clds,

                                           CodeBlobClosure* blobs) {

  StrongRootsClosures closures(oops, clds, blobs);

  process_java_roots(&closures, NULL, 0);

  process_vm_roots(&closures, NULL, 0);

  _process_strong_tasks.all_tasks_completed(n_workers());

}

// Adaptor to pass the closures to all the roots in the VM.

class AllRootsClosures : public G1RootClosures {

  OopClosure* _roots;

  CLDClosure* _clds;

public:

  AllRootsClosures(OopClosure* roots, CLDClosure* clds) :

      _roots(roots), _clds(clds) {}

  OopClosure* weak_oops() { return _roots; }

  OopClosure* strong_oops() { return _roots; }

  // By returning the same CLDClosure for both weak and strong CLDs we ensure

  // that a single walk of the CLDG will invoke the closure on all CLDs i the

  // system.

  CLDClosure* weak_clds() { return _clds; }

  CLDClosure* strong_clds() { return _clds; }

  // We don't want to visit code blobs more than once, so we return NULL for the

  // strong case and walk the entire code cache as a separate step.

  CodeBlobClosure* strong_codeblobs() { return NULL; }

};

void G1RootProcessor::process_all_roots(OopClosure* oops,

                                        CLDClosure* clds,

                                        CodeBlobClosure* blobs) {

  AllRootsClosures closures(oops, clds);

  process_java_roots(&closures, NULL, 0);

  process_vm_roots(&closures, NULL, 0);

  process_code_cache_roots(blobs, NULL, 0);

  _process_strong_tasks.all_tasks_completed(n_workers());

}

void G1RootProcessor::process_java_roots(G1RootClosures* closures,

                                         G1GCPhaseTimes* phase_times,

                                         uint worker_id,

                                         bool notify_claimed_nmethods_done) {

  // We need to make make sure that the "strong" nmethods are processed first

  // using the strong closure. Only after that we process the weakly reachable

  // nmethods.

  // We need to strictly separate the strong and weak nmethod processing because

  // any processing claims that nmethod, i.e. will not be iterated again.

  // Which means if an nmethod is processed first and claimed, the strong processing

  // will not happen, and the oops reachable by that nmethod will not be marked

  // properly.

  //

  // That is why we process strong nmethods first, synchronize all threads via a

  // barrier, and only then allow weak processing. To minimize the wait time at

  // that barrier we do the strong nmethod processing first, and immediately after-

  // wards indicate that that thread is done. Hopefully other root processing after

  // nmethod processing is enough so there is no need to wait.

  //

  // This is only required in the concurrent start pause with class unloading enabled.

  {

    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ThreadRoots, worker_id);

    bool is_par = n_workers() > 1;

    Threads::possibly_parallel_oops_do(is_par,

                                       closures->strong_oops(),

                                       closures->strong_codeblobs());

  }

  // This is the point where this worker thread will not find more strong nmethods.

  // Report this so G1 can synchronize the strong and weak CLDs/nmethods processing.

  if (notify_claimed_nmethods_done) {

    worker_has_discovered_all_strong_nmethods();

  }

  {

    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::CLDGRoots, worker_id);

    if (_process_strong_tasks.try_claim_task(G1RP_PS_ClassLoaderDataGraph_oops_do)) {

      ClassLoaderDataGraph::roots_cld_do(closures->strong_clds(), closures->weak_clds());

    }

  }

}

void G1RootProcessor::process_vm_roots(G1RootClosures* closures,

                                       G1GCPhaseTimes* phase_times,

                                       uint worker_id) {

  OopClosure* strong_roots = closures->strong_oops();

  {

    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::UniverseRoots, worker_id);

    if (_process_strong_tasks.try_claim_task(G1RP_PS_Universe_oops_do)) {

      Universe::oops_do(strong_roots);

    }

  }

  {

    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JNIRoots, worker_id);

    if (_process_strong_tasks.try_claim_task(G1RP_PS_JNIHandles_oops_do)) {

      JNIHandles::oops_do(strong_roots);

    }

  }

  {

    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ObjectSynchronizerRoots, worker_id);

    if (_process_strong_tasks.try_claim_task(G1RP_PS_ObjectSynchronizer_oops_do)) {

      ObjectSynchronizer::oops_do(strong_roots);

    }

  }

  {

    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::ManagementRoots, worker_id);

    if (_process_strong_tasks.try_claim_task(G1RP_PS_Management_oops_do)) {

      Management::oops_do(strong_roots);

    }

  }

  {

    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::JVMTIRoots, worker_id);

    if (_process_strong_tasks.try_claim_task(G1RP_PS_jvmti_oops_do)) {

      JvmtiExport::oops_do(strong_roots);

    }

  }

#if INCLUDE_AOT

  if (UseAOT) {

    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::AOTCodeRoots, worker_id);

    if (_process_strong_tasks.try_claim_task(G1RP_PS_aot_oops_do)) {

        AOTLoader::oops_do(strong_roots);

    }

  }

#endif

  {

    G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::SystemDictionaryRoots, worker_id);

    if (_process_strong_tasks.try_claim_task(G1RP_PS_SystemDictionary_oops_do)) {

      SystemDictionary::oops_do(strong_roots);

    }

  }

}

void G1RootProcessor::process_code_cache_roots(CodeBlobClosure* code_closure,

                                               G1GCPhaseTimes* phase_times,

                                               uint worker_id) {

  if (_process_strong_tasks.try_claim_task(G1RP_PS_CodeCache_oops_do)) {

    CodeCache::blobs_do(code_closure);

  }

}

uint G1RootProcessor::n_workers() const {

  return _srs.n_threads();

}