/*

 * Copyright (c) 2018, 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/symbolTable.hpp"

#include "classfile/stringTable.hpp"

#include "code/codeCache.hpp"

#include "gc/shared/parallelCleaning.hpp"

#include "memory/resourceArea.hpp"

#include "logging/log.hpp"

StringCleaningTask::StringCleaningTask(BoolObjectClosure* is_alive, StringDedupUnlinkOrOopsDoClosure* dedup_closure, bool process_strings) :

  AbstractGangTask("String Unlinking"),

  _is_alive(is_alive),

  _dedup_closure(dedup_closure),

  _par_state_string(StringTable::weak_storage()),

  _initial_string_table_size((int) StringTable::the_table()->table_size()),

  _process_strings(process_strings), _strings_processed(0), _strings_removed(0) {

  if (process_strings) {

    StringTable::reset_dead_counter();

  }

}

StringCleaningTask::~StringCleaningTask() {

  log_info(gc, stringtable)(

      "Cleaned string table, "

      "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",

      strings_processed(), strings_removed());

  if (_process_strings) {

    StringTable::finish_dead_counter();

  }

}

void StringCleaningTask::work(uint worker_id) {

  if (_process_strings) {

    StringTable::possibly_parallel_unlink(&_par_state_string, _is_alive, &strings_processed, &strings_removed);

    Atomic::add(strings_processed, &_strings_processed);

    Atomic::add(strings_removed, &_strings_removed);

  }

  if (_dedup_closure != NULL) {

    StringDedup::parallel_unlink(_dedup_closure, worker_id);

  }

}

CodeCacheUnloadingTask::CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :

      _is_alive(is_alive),

      _unloading_occurred(unloading_occurred),

      _num_workers(num_workers),

      _first_nmethod(NULL),

      _claimed_nmethod(NULL),

      _postponed_list(NULL),

      _num_entered_barrier(0) {

  CompiledMethod::increase_unloading_clock();

  // Get first alive nmethod

  CompiledMethodIterator iter = CompiledMethodIterator();

  if(iter.next_alive()) {

    _first_nmethod = iter.method();

  }

  _claimed_nmethod = _first_nmethod;

}

CodeCacheUnloadingTask::~CodeCacheUnloadingTask() {

  CodeCache::verify_clean_inline_caches();

  CodeCache::set_needs_cache_clean(false);

  guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");

  CodeCache::verify_icholder_relocations();

}

Monitor* CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);

void CodeCacheUnloadingTask::add_to_postponed_list(CompiledMethod* nm) {

  CompiledMethod* old;

  do {

    old = _postponed_list;

    nm->set_unloading_next(old);

  } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);

}

void CodeCacheUnloadingTask::clean_nmethod(CompiledMethod* nm) {

  bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);

  if (postponed) {

    // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.

    add_to_postponed_list(nm);

  }

  // Mark that this nmethod has been cleaned/unloaded.

  // After this call, it will be safe to ask if this nmethod was unloaded or not.

  nm->set_unloading_clock(CompiledMethod::global_unloading_clock());

}

void CodeCacheUnloadingTask::clean_nmethod_postponed(CompiledMethod* nm) {

  nm->do_unloading_parallel_postponed();

}

void CodeCacheUnloadingTask::claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {

  CompiledMethod* first;

  CompiledMethodIterator last;

  do {

    *num_claimed_nmethods = 0;

    first = _claimed_nmethod;

    last = CompiledMethodIterator(first);

    if (first != NULL) {

      for (int i = 0; i < MaxClaimNmethods; i++) {

        if (!last.next_alive()) {

          break;

        }

        claimed_nmethods[i] = last.method();

        (*num_claimed_nmethods)++;

      }

    }

  } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);

}

CompiledMethod* CodeCacheUnloadingTask::claim_postponed_nmethod() {

  CompiledMethod* claim;

  CompiledMethod* next;

  do {

    claim = _postponed_list;

    if (claim == NULL) {

      return NULL;

    }

    next = claim->unloading_next();

  } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);

  return claim;

}

void CodeCacheUnloadingTask::barrier_mark(uint worker_id) {

  MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);

  _num_entered_barrier++;

  if (_num_entered_barrier == _num_workers) {

    ml.notify_all();

  }

}

void CodeCacheUnloadingTask::barrier_wait(uint worker_id) {

  if (_num_entered_barrier < _num_workers) {

    MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);

    while (_num_entered_barrier < _num_workers) {

        ml.wait(Mutex::_no_safepoint_check_flag, 0, false);

    }

  }

}

void CodeCacheUnloadingTask::work_first_pass(uint worker_id) {

  // The first nmethods is claimed by the first worker.

  if (worker_id == 0 && _first_nmethod != NULL) {

    clean_nmethod(_first_nmethod);

    _first_nmethod = NULL;

  }

  int num_claimed_nmethods;

  CompiledMethod* claimed_nmethods[MaxClaimNmethods];

  while (true) {

    claim_nmethods(claimed_nmethods, &num_claimed_nmethods);

    if (num_claimed_nmethods == 0) {

      break;

    }

    for (int i = 0; i < num_claimed_nmethods; i++) {

      clean_nmethod(claimed_nmethods[i]);

    }

  }

}

void CodeCacheUnloadingTask::work_second_pass(uint worker_id) {

  CompiledMethod* nm;

  // Take care of postponed nmethods.

  while ((nm = claim_postponed_nmethod()) != NULL) {

    clean_nmethod_postponed(nm);

  }

}

KlassCleaningTask::KlassCleaningTask() :

  _clean_klass_tree_claimed(0),

  _klass_iterator() {

}

bool KlassCleaningTask::claim_clean_klass_tree_task() {

  if (_clean_klass_tree_claimed) {

    return false;

  }

  return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;

}

InstanceKlass* KlassCleaningTask::claim_next_klass() {

  Klass* klass;

  do {

    klass =_klass_iterator.next_klass();

  } while (klass != NULL && !klass->is_instance_klass());

  // this can be null so don't call InstanceKlass::cast

  return static_cast<InstanceKlass*>(klass);

}

void KlassCleaningTask::work() {

  ResourceMark rm;

  // One worker will clean the subklass/sibling klass tree.

  if (claim_clean_klass_tree_task()) {

    Klass::clean_subklass_tree();

  }

  // All workers will help cleaning the classes,

  InstanceKlass* klass;

  while ((klass = claim_next_klass()) != NULL) {

    clean_klass(klass);

  }

}

ParallelCleaningTask::ParallelCleaningTask(BoolObjectClosure* is_alive,

  StringDedupUnlinkOrOopsDoClosure* dedup_closure, uint num_workers, bool unloading_occurred) :

  AbstractGangTask("Parallel Cleaning"),

  _unloading_occurred(unloading_occurred),

  _string_task(is_alive, StringDedup::is_enabled() ? dedup_closure : NULL, true),

  _code_cache_task(num_workers, is_alive, unloading_occurred),

  _klass_cleaning_task() {

}

// The parallel work done by all worker threads.

void ParallelCleaningTask::work(uint worker_id) {

    // Do first pass of code cache cleaning.

    _code_cache_task.work_first_pass(worker_id);

    // Let the threads mark that the first pass is done.

    _code_cache_task.barrier_mark(worker_id);

    // Clean the Strings and Symbols.

    _string_task.work(worker_id);

    // Wait for all workers to finish the first code cache cleaning pass.

    _code_cache_task.barrier_wait(worker_id);

    // Do the second code cache cleaning work, which realize on

    // the liveness information gathered during the first pass.

    _code_cache_task.work_second_pass(worker_id);

  // Clean all klasses that were not unloaded.

  // The weak metadata in klass doesn't need to be

  // processed if there was no unloading.

  if (_unloading_occurred) {

    _klass_cleaning_task.work();

  }

}