view src/share/vm/memory/restore.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 c18cbe5936b8
line wrap: on
line source

/*
 * Copyright 2003-2008 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/_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);
}