view src/share/vm/gc_implementation/concurrentMarkSweep/freeChunk.cpp @ 452:00b023ae2d78

6722113: CMS: Incorrect overflow handling during precleaning of Reference lists Summary: When we encounter marking stack overflow during precleaning of Reference lists, we were using the overflow list mechanism, which can cause problems on account of mutating the mark word of the header because of conflicts with mutator accesses and updates of that field. Instead we should use the usual mechanism for overflow handling in concurrent phases, namely dirtying of the card on which the overflowed object lies. Since precleaning effectively does a form of discovered list processing, albeit with discovery enabled, we needed to adjust some code to be correct in the face of interleaved processing and discovery. Reviewed-by: apetrusenko, jcoomes
author ysr
date Thu, 20 Nov 2008 12:27:41 -0800
parents d1605aabd0a1
children e018e6884bd8
line wrap: on
line source

/*
 * Copyright 2001-2008 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 */

# include "incls/_precompiled.incl"
# include "incls/_freeChunk.cpp.incl"

#ifndef PRODUCT

#define baadbabeHeapWord badHeapWordVal
#define deadbeefHeapWord 0xdeadbeef

size_t const FreeChunk::header_size() {
  return sizeof(FreeChunk)/HeapWordSize;
}

void FreeChunk::mangleAllocated(size_t size) {
  // mangle all but the header of a just-allocated block
  // of storage
  assert(size >= MinChunkSize, "smallest size of object");
  // we can't assert that _size == size because this may be an
  // allocation out of a linear allocation block
  assert(sizeof(FreeChunk) % HeapWordSize == 0,
         "shouldn't write beyond chunk");
  HeapWord* addr = (HeapWord*)this;
  size_t hdr = header_size();
  Copy::fill_to_words(addr + hdr, size - hdr, baadbabeHeapWord);
}

void FreeChunk::mangleFreed(size_t sz) {
  assert(baadbabeHeapWord != deadbeefHeapWord, "Need distinct patterns");
  // mangle all but the header of a just-freed block of storage
  // just prior to passing it to the storage dictionary
  assert(sz >= MinChunkSize, "smallest size of object");
  assert(sz == size(), "just checking");
  HeapWord* addr = (HeapWord*)this;
  size_t hdr = header_size();
  Copy::fill_to_words(addr + hdr, sz - hdr, deadbeefHeapWord);
}

void FreeChunk::verifyList() const {
  FreeChunk* nextFC = next();
  if (nextFC != NULL) {
    assert(this == nextFC->prev(), "broken chain");
    assert(size() == nextFC->size(), "wrong size");
    nextFC->verifyList();
  }
}
#endif