view src/share/vm/shark/sharkCodeBuffer.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 d2ede61b7a12
children f95d63e2154a
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/*
 * Copyright (c) 1999, 2007, Oracle and/or its affiliates. All rights reserved.
 * Copyright 2009 Red Hat, Inc.
 * 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 SharkCodeBuffer : public StackObj {
 public:
  SharkCodeBuffer(MacroAssembler* masm)
    : _masm(masm), _base_pc(NULL) {}

 private:
  MacroAssembler* _masm;
  llvm::Value*    _base_pc;

 private:
  MacroAssembler* masm() const {
    return _masm;
  }

 public:
  llvm::Value* base_pc() const {
    return _base_pc;
  }
  void set_base_pc(llvm::Value* base_pc) {
    assert(_base_pc == NULL, "only do this once");
    _base_pc = base_pc;
  }

  // Allocate some space in the buffer and return its address.
  // This buffer will have been relocated by the time the method
  // is installed, so you can't inline the result in code.
 public:
  void* malloc(size_t size) const {
    masm()->align(BytesPerWord);
    void *result = masm()->pc();
    masm()->advance(size);
    return result;
  }

  // Create a unique offset in the buffer.
 public:
  int create_unique_offset() const {
    int offset = masm()->offset();
    masm()->advance(1);
    return offset;
  }

  // Inline an oop into the buffer and return its offset.
 public:
  int inline_oop(jobject object) const {
    masm()->align(BytesPerWord);
    int offset = masm()->offset();
    masm()->store_oop(object);
    return offset;
  }

  // Inline a block of non-oop data into the buffer and return its offset.
 public:
  int inline_data(void *src, size_t size) const {
    masm()->align(BytesPerWord);
    int offset = masm()->offset();
    void *dst = masm()->pc();
    masm()->advance(size);
    memcpy(dst, src, size);
    return offset;
  }
};