view src/share/vm/memory/barrierSet.inline.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 c18cbe5936b8
children f95d63e2154a
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/*
 * Copyright (c) 2001, 2008, 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.
 *
 */

// Inline functions of BarrierSet, which de-virtualize certain
// performance-critical calls when the barrier is the most common
// card-table kind.

template <class T> void BarrierSet::write_ref_field_pre(T* field, oop new_val) {
  if (kind() == CardTableModRef) {
    ((CardTableModRefBS*)this)->inline_write_ref_field_pre(field, new_val);
  } else {
    write_ref_field_pre_work(field, new_val);
  }
}

void BarrierSet::write_ref_field(void* field, oop new_val) {
  if (kind() == CardTableModRef) {
    ((CardTableModRefBS*)this)->inline_write_ref_field(field, new_val);
  } else {
    write_ref_field_work(field, new_val);
  }
}

// count is number of array elements being written
void BarrierSet::write_ref_array(HeapWord* start, size_t count) {
  assert(count <= (size_t)max_intx, "count too large");
  HeapWord* end = (HeapWord*)((char*)start + (count*heapOopSize));
  // In the case of compressed oops, start and end may potentially be misaligned;
  // so we need to conservatively align the first downward (this is not
  // strictly necessary for current uses, but a case of good hygiene and,
  // if you will, aesthetics) and the second upward (this is essential for
  // current uses) to a HeapWord boundary, so we mark all cards overlapping
  // this write. If this evolves in the future to calling a
  // logging barrier of narrow oop granularity, like the pre-barrier for G1
  // (mentioned here merely by way of example), we will need to change this
  // interface, so it is "exactly precise" (if i may be allowed the adverbial
  // redundancy for emphasis) and does not include narrow oop slots not
  // included in the original write interval.
  HeapWord* aligned_start = (HeapWord*)align_size_down((uintptr_t)start, HeapWordSize);
  HeapWord* aligned_end   = (HeapWord*)align_size_up  ((uintptr_t)end,   HeapWordSize);
  // If compressed oops were not being used, these should already be aligned
  assert(UseCompressedOops || (aligned_start == start && aligned_end == end),
         "Expected heap word alignment of start and end");
#if 0
  warning("Post:\t" INTPTR_FORMAT "[" SIZE_FORMAT "] : [" INTPTR_FORMAT","INTPTR_FORMAT")\t",
                   start,            count,              aligned_start,   aligned_end);
#endif
  write_ref_array_work(MemRegion(aligned_start, aligned_end));
}


void BarrierSet::write_region(MemRegion mr) {
  if (kind() == CardTableModRef) {
    ((CardTableModRefBS*)this)->inline_write_region(mr);
  } else {
    write_region_work(mr);
  }
}