view src/share/vm/memory/restore.cpp @ 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
line wrap: on
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/*
 * Copyright (c) 2003, 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.
 *
 */

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


// Closure for serializing initialization data in from a data area
// (oop_array) read from the shared file.

class ReadClosure : public SerializeOopClosure {
private:
  oop** _oop_array;

  inline oop nextOop() {
    return *(*_oop_array)++;
  }

public:
  ReadClosure(oop** oop_array) { _oop_array = oop_array; }

  void do_oop(oop* p) {
    assert(SharedSkipVerify || *p == NULL || *p == Universe::klassKlassObj(),
           "initializing previously initialized oop.");
    oop obj = nextOop();
    assert(SharedSkipVerify || (intptr_t)obj >= 0 || (intptr_t)obj < -100,
           "hit tag while initializing oops.");
    assert(SharedSkipVerify || obj->is_oop_or_null(), "invalid oop");
    *p = obj;
  }

  void do_oop(narrowOop* p) { ShouldNotReachHere(); }

  void do_ptr(void** p) {
    assert(*p == NULL, "initializing previous initialized pointer.");
    void* obj = nextOop();
    assert((intptr_t)obj >= 0 || (intptr_t)obj < -100,
           "hit tag while initializing ptrs.");
    *p = obj;
  }

  void do_ptr(HeapWord** p) { do_ptr((void **) p); }

  void do_int(int* p) {
    *p = (int)(intptr_t)nextOop();
  }

  void do_size_t(size_t* p) {
    // Assumes that size_t and pointers are the same size.
    *p = (size_t)nextOop();
  }

  void do_tag(int tag) {
    int old_tag;
    do_int(&old_tag);
    FileMapInfo::assert_mark(tag == old_tag);
  }

  void do_region(u_char* start, size_t size) {
    assert((intptr_t)start % sizeof(oop) == 0, "bad alignment");
    assert(size % sizeof(oop) == 0, "bad size");
    do_tag((int)size);
    while (size > 0) {
      *(oop*)start = nextOop();
      start += sizeof(oop);
      size -= sizeof(oop);
    }
  }

  bool reading() const { return true; }
};


// Read the oop and miscellaneous data from the shared file, and
// serialize it out to its various destinations.

void CompactingPermGenGen::initialize_oops() {
  FileMapInfo *mapinfo = FileMapInfo::current_info();

  char* buffer = mapinfo->region_base(md);

  // Skip over (reserve space for) a list of addresses of C++ vtables
  // for Klass objects.  They get filled in later.

  // Skip over (reserve space for) dummy C++ vtables Klass objects.
  // They are used as is.

  void** vtbl_list = (void**)buffer;
  buffer += vtbl_list_size * sizeof(void*);
  intptr_t vtable_size = *(intptr_t*)buffer;
  buffer += sizeof(intptr_t);
  buffer += vtable_size;

  // Create the symbol table using the bucket array at this spot in the
  // misc data space.  Since the symbol table is often modified, this
  // region (of mapped pages) will be copy-on-write.

  int symbolTableLen = *(intptr_t*)buffer;
  buffer += sizeof(intptr_t);
  int number_of_entries = *(intptr_t*)buffer;
  buffer += sizeof(intptr_t);
  SymbolTable::create_table((HashtableBucket*)buffer, symbolTableLen,
                            number_of_entries);
  buffer += symbolTableLen;

  // Create the string table using the bucket array at this spot in the
  // misc data space.  Since the string table is often modified, this
  // region (of mapped pages) will be copy-on-write.

  int stringTableLen = *(intptr_t*)buffer;
  buffer += sizeof(intptr_t);
  number_of_entries = *(intptr_t*)buffer;
  buffer += sizeof(intptr_t);
  StringTable::create_table((HashtableBucket*)buffer, stringTableLen,
                            number_of_entries);
  buffer += stringTableLen;

  // Create the shared dictionary using the bucket array at this spot in
  // the misc data space.  Since the shared dictionary table is never
  // modified, this region (of mapped pages) will be (effectively, if
  // not explicitly) read-only.

  int sharedDictionaryLen = *(intptr_t*)buffer;
  buffer += sizeof(intptr_t);
  number_of_entries = *(intptr_t*)buffer;
  buffer += sizeof(intptr_t);
  SystemDictionary::set_shared_dictionary((HashtableBucket*)buffer,
                                          sharedDictionaryLen,
                                          number_of_entries);
  buffer += sharedDictionaryLen;

  // Create the package info table using the bucket array at this spot in
  // the misc data space.  Since the package info table is never
  // modified, this region (of mapped pages) will be (effectively, if
  // not explicitly) read-only.

  int pkgInfoLen = *(intptr_t*)buffer;
  buffer += sizeof(intptr_t);
  number_of_entries = *(intptr_t*)buffer;
  buffer += sizeof(intptr_t);
  ClassLoader::create_package_info_table((HashtableBucket*)buffer, pkgInfoLen,
                                         number_of_entries);
  buffer += pkgInfoLen;
  ClassLoader::verify();

  // The following data in the shared misc data region are the linked
  // list elements (HashtableEntry objects) for the symbol table, string
  // table, and shared dictionary.  The heap objects refered to by the
  // symbol table, string table, and shared dictionary are permanent and
  // unmovable.  Since new entries added to the string and symbol tables
  // are always added at the beginning of the linked lists, THESE LINKED
  // LIST ELEMENTS ARE READ-ONLY.

  int len = *(intptr_t*)buffer; // skip over symbol table entries
  buffer += sizeof(intptr_t);
  buffer += len;

  len = *(intptr_t*)buffer;     // skip over string table entries
  buffer += sizeof(intptr_t);
  buffer += len;

  len = *(intptr_t*)buffer;     // skip over shared dictionary entries
  buffer += sizeof(intptr_t);
  buffer += len;

  len = *(intptr_t*)buffer;     // skip over package info table entries
  buffer += sizeof(intptr_t);
  buffer += len;

  len = *(intptr_t*)buffer;     // skip over package info table char[] arrays.
  buffer += sizeof(intptr_t);
  buffer += len;

  oop* oop_array = (oop*)buffer;
  ReadClosure rc(&oop_array);
  serialize_oops(&rc);
}