jdk8-mips64-public/hotspot: src/share/vm/memory/blockOffsetTable.inline.hpp@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

     1 /*

     2  * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  *

    23  */

    25 //////////////////////////////////////////////////////////////////////////

    26 // BlockOffsetTable inlines

    27 //////////////////////////////////////////////////////////////////////////

    28 inline HeapWord* BlockOffsetTable::block_start(const void* addr) const {

    29   if (addr >= _bottom && addr < _end) {

    30     return block_start_unsafe(addr);

    31   } else {

    32     return NULL;

    33   }

    34 }

    36 //////////////////////////////////////////////////////////////////////////

    37 // BlockOffsetSharedArray inlines

    38 //////////////////////////////////////////////////////////////////////////

    39 inline size_t BlockOffsetSharedArray::index_for(const void* p) const {

    40   char* pc = (char*)p;

    41   assert(pc >= (char*)_reserved.start() &&

    42          pc <  (char*)_reserved.end(),

    43          "p not in range.");

    44   size_t delta = pointer_delta(pc, _reserved.start(), sizeof(char));

    45   size_t result = delta >> LogN;

    46   assert(result < _vs.committed_size(), "bad index from address");

    47   return result;

    48 }

    50 inline HeapWord* BlockOffsetSharedArray::address_for_index(size_t index) const {

    51   assert(index < _vs.committed_size(), "bad index");

    52   HeapWord* result = _reserved.start() + (index << LogN_words);

    53   assert(result >= _reserved.start() && result < _reserved.end(),

    54          "bad address from index");

    55   return result;

    56 }

    58 inline void BlockOffsetSharedArray::check_reducing_assertion(bool reducing) {

    59     assert(reducing || !SafepointSynchronize::is_at_safepoint() || init_to_zero() ||

    60            Thread::current()->is_VM_thread() ||

    61            Thread::current()->is_ConcurrentGC_thread() ||

    62            ((!Thread::current()->is_ConcurrentGC_thread()) &&

    63             ParGCRareEvent_lock->owned_by_self()), "Crack");

    64 }

    66 //////////////////////////////////////////////////////////////////////////

    67 // BlockOffsetArrayNonContigSpace inlines

    68 //////////////////////////////////////////////////////////////////////////

    69 inline void BlockOffsetArrayNonContigSpace::freed(HeapWord* blk,

    70                                                   size_t size) {

    71   freed(blk, blk + size);

    72 }

    74 inline void BlockOffsetArrayNonContigSpace::freed(HeapWord* blk_start,

    75                                                   HeapWord* blk_end) {

    76   // Verify that the BOT shows [blk_start, blk_end) to be one block.

    77   verify_single_block(blk_start, blk_end);

    78   // adjust _unallocated_block upward or downward

    79   // as appropriate

    80   if (BlockOffsetArrayUseUnallocatedBlock) {

    81     assert(_unallocated_block <= _end,

    82            "Inconsistent value for _unallocated_block");

    83     if (blk_end >= _unallocated_block && blk_start <= _unallocated_block) {

    84       // CMS-specific note: a block abutting _unallocated_block to

    85       // its left is being freed, a new block is being added or

    86       // we are resetting following a compaction

    87       _unallocated_block = blk_start;

    88     }

    89   }

    90 }

Mercurial > jdk8-mips64-public > hotspot / file revision

src/share/vm/memory/blockOffsetTable.inline.hpp@be3f9c242c9d

src/share/vm/memory/blockOffsetTable.inline.hpp