src/hotspot/share/gc/shared/parallelCleaning.cpp

/*
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 * 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
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#include "classfile/stringTable.hpp"
#include "classfile/symbolTable.hpp"
#include "code/codeCache.hpp"
#include "gc/shared/parallelCleaning.hpp"
#include "logging/log.hpp"
#include "memory/resourceArea.hpp"
#include "runtime/atomic.hpp"

CodeCacheUnloadingTask::CodeCacheUnloadingTask(uint num_workers, bool unloading_occurred) :
  _unloading_occurred(unloading_occurred),
  _num_workers(num_workers),
  _first_nmethod(nullptr),
  _claimed_nmethod(nullptr) {
  // Get first alive nmethod
  NMethodIterator iter(NMethodIterator::all);
  if(iter.next()) {
    _first_nmethod = iter.method();
  }
  _claimed_nmethod = _first_nmethod;
}

CodeCacheUnloadingTask::~CodeCacheUnloadingTask() {
  CodeCache::verify_clean_inline_caches();
}

void CodeCacheUnloadingTask::claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
  nmethod* first;
  NMethodIterator last(NMethodIterator::all);

  do {
    *num_claimed_nmethods = 0;

    first = _claimed_nmethod;
    last = NMethodIterator(NMethodIterator::all, first);

    if (first != nullptr) {

      for (int i = 0; i < MaxClaimNmethods; i++) {
        if (!last.next()) {
          break;
        }
        claimed_nmethods[i] = last.method();
        (*num_claimed_nmethods)++;
      }
    }

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

void CodeCacheUnloadingTask::work(uint worker_id) {
  // The first nmethods is claimed by the first worker.
  if (worker_id == 0 && _first_nmethod != nullptr) {
    _first_nmethod->do_unloading(_unloading_occurred);
    _first_nmethod = nullptr;
  }

  int num_claimed_nmethods;
  nmethod* 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++) {
      claimed_nmethods[i]->do_unloading(_unloading_occurred);
    }
  }
}

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(&_clean_klass_tree_claimed, 0, 1) == 0;
}

InstanceKlass* KlassCleaningTask::claim_next_klass() {
  Klass* klass;
  do {
    klass =_klass_iterator.next_klass();
  } while (klass != nullptr && !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()) != nullptr) {
    clean_klass(klass);
  }
}