1 /*
   2  * Copyright (c) 2001, 2008, 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  */
  24 
  25 // Methods of protected closure types
  26 
  27 template <class T>
  28 inline void DefNewGeneration::KeepAliveClosure::do_oop_work(T* p) {
  29 #ifdef ASSERT
  30   {
  31     // We never expect to see a null reference being processed
  32     // as a weak reference.
  33     assert (!oopDesc::is_null(*p), "expected non-null ref");
  34     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
  35     assert (obj->is_oop(), "expected an oop while scanning weak refs");
  36   }
  37 #endif // ASSERT
  38 
  39   _cl->do_oop_nv(p);
  40 
  41   // Card marking is trickier for weak refs.
  42   // This oop is a 'next' field which was filled in while we
  43   // were discovering weak references. While we might not need
  44   // to take a special action to keep this reference alive, we
  45   // will need to dirty a card as the field was modified.
  46   //
  47   // Alternatively, we could create a method which iterates through
  48   // each generation, allowing them in turn to examine the modified
  49   // field.
  50   //
  51   // We could check that p is also in an older generation, but
  52   // dirty cards in the youngest gen are never scanned, so the
  53   // extra check probably isn't worthwhile.
  54   if (Universe::heap()->is_in_reserved(p)) {
  55     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
  56     _rs->inline_write_ref_field_gc(p, obj);
  57   }
  58 }
  59 
  60 template <class T>
  61 inline void DefNewGeneration::FastKeepAliveClosure::do_oop_work(T* p) {
  62 #ifdef ASSERT
  63   {
  64     // We never expect to see a null reference being processed
  65     // as a weak reference.
  66     assert (!oopDesc::is_null(*p), "expected non-null ref");
  67     oop obj = oopDesc::load_decode_heap_oop_not_null(p);
  68     assert (obj->is_oop(), "expected an oop while scanning weak refs");
  69   }
  70 #endif // ASSERT
  71 
  72   _cl->do_oop_nv(p);
  73 
  74   // Optimized for Defnew generation if it's the youngest generation:
  75   // we set a younger_gen card if we have an older->youngest
  76   // generation pointer.
  77   oop obj = oopDesc::load_decode_heap_oop_not_null(p);
  78   if (((HeapWord*)obj < _boundary) && Universe::heap()->is_in_reserved(p)) {
  79     _rs->inline_write_ref_field_gc(p, obj);
  80   }
  81 }