view src/share/vm/oops/cpCacheKlass.hpp @ 1716:be3f9c242c9d

6948538: CMS: BOT walkers can fall into object allocation and initialization cracks Summary: GC workers now recognize an intermediate transient state of blocks which are allocated but have not yet completed initialization. blk_start() calls do not attempt to determine the size of a block in the transient state, rather waiting for the block to become initialized so that it is safe to query its size. Audited and ensured the order of initialization of object fields (klass, free bit and size) to respect block state transition protocol. Also included some new assertion checking code enabled in debug mode. Reviewed-by: chrisphi, johnc, poonam
author ysr
date Mon, 16 Aug 2010 15:58:42 -0700
parents 126ea7725993
children f95d63e2154a
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/*
 * Copyright (c) 1998, 2009, 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.
 *
 */

class constantPoolCacheKlass: public Klass {
  juint    _alloc_size;        // allocation profiling support
 public:
  // Dispatched klass operations
  bool oop_is_constantPoolCache() const          { return true; }
  int  oop_size(oop obj) const;
  int  klass_oop_size() const                    { return object_size(); }

  // Allocation
  DEFINE_ALLOCATE_PERMANENT(constantPoolCacheKlass);
  constantPoolCacheOop allocate(int length, bool is_conc_safe, TRAPS);
  static klassOop create_klass(TRAPS);

  // Casting from klassOop
  static constantPoolCacheKlass* cast(klassOop k) {
    assert(k->klass_part()->oop_is_constantPoolCache(), "cast to constantPoolCacheKlass");
    return (constantPoolCacheKlass*)k->klass_part();
  }

  // Sizing
  static int header_size()       { return oopDesc::header_size() + sizeof(constantPoolCacheKlass)/HeapWordSize; }
  int object_size() const        { return align_object_size(header_size()); }

  // Garbage collection
  void oop_follow_contents(oop obj);
  int oop_adjust_pointers(oop obj);
  virtual bool oop_is_conc_safe(oop obj) const;

  // Parallel Scavenge and Parallel Old
  PARALLEL_GC_DECLS

  // Iterators
  int oop_oop_iterate(oop obj, OopClosure* blk);
  int oop_oop_iterate_m(oop obj, OopClosure* blk, MemRegion mr);

  // Allocation profiling support
  juint alloc_size() const              { return _alloc_size; }
  void set_alloc_size(juint n)          { _alloc_size = n; }

  // Printing
  void oop_print_value_on(oop obj, outputStream* st);
  void oop_print_on(oop obj, outputStream* st);

  // Verification
  const char* internal_name() const;
  void oop_verify_on(oop obj, outputStream* st);
};