1 /*
   2  * Copyright (c) 2006, 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  */
  24 
  25 #ifndef SHARE_VM_OOPS_MARKOOP_INLINE_HPP
  26 #define SHARE_VM_OOPS_MARKOOP_INLINE_HPP
  27 
  28 #include "oops/klass.hpp"
  29 #include "oops/klassOop.hpp"
  30 #include "oops/markOop.hpp"
  31 #include "runtime/globals.hpp"
  32 
  33 // Should this header be preserved during GC?
  34 inline bool markOopDesc::must_be_preserved_with_bias(oop obj_containing_mark) const {
  35   assert(UseBiasedLocking, "unexpected");
  36   if (has_bias_pattern()) {
  37     // Will reset bias at end of collection
  38     // Mark words of biased and currently locked objects are preserved separately
  39     return false;
  40   }
  41   markOop prototype_header = prototype_for_object(obj_containing_mark);
  42   if (prototype_header->has_bias_pattern()) {
  43     // Individual instance which has its bias revoked; must return
  44     // true for correctness
  45     return true;
  46   }
  47   return (!is_unlocked() || !has_no_hash());
  48 }
  49 
  50 inline bool markOopDesc::must_be_preserved(oop obj_containing_mark) const {
  51   if (!UseBiasedLocking)
  52     return (!is_unlocked() || !has_no_hash());
  53   return must_be_preserved_with_bias(obj_containing_mark);
  54 }
  55 
  56 // Should this header (including its age bits) be preserved in the
  57 // case of a promotion failure during scavenge?
  58 inline bool markOopDesc::must_be_preserved_with_bias_for_promotion_failure(oop obj_containing_mark) const {
  59   assert(UseBiasedLocking, "unexpected");
  60   // We don't explicitly save off the mark words of biased and
  61   // currently-locked objects during scavenges, so if during a
  62   // promotion failure we encounter either a biased mark word or a
  63   // klass which still has a biasable prototype header, we have to
  64   // preserve the mark word. This results in oversaving, but promotion
  65   // failures are rare, and this avoids adding more complex logic to
  66   // the scavengers to call new variants of
  67   // BiasedLocking::preserve_marks() / restore_marks() in the middle
  68   // of a scavenge when a promotion failure has first been detected.
  69   if (has_bias_pattern() ||
  70       prototype_for_object(obj_containing_mark)->has_bias_pattern()) {
  71     return true;
  72   }
  73   return (this != prototype());
  74 }
  75 
  76 inline bool markOopDesc::must_be_preserved_for_promotion_failure(oop obj_containing_mark) const {
  77   if (!UseBiasedLocking)
  78     return (this != prototype());
  79   return must_be_preserved_with_bias_for_promotion_failure(obj_containing_mark);
  80 }
  81 
  82 
  83 // Should this header (including its age bits) be preserved in the
  84 // case of a scavenge in which CMS is the old generation?
  85 inline bool markOopDesc::must_be_preserved_with_bias_for_cms_scavenge(klassOop klass_of_obj_containing_mark) const {
  86   assert(UseBiasedLocking, "unexpected");
  87   // CMS scavenges preserve mark words in similar fashion to promotion failures; see above
  88   if (has_bias_pattern() ||
  89       klass_of_obj_containing_mark->klass_part()->prototype_header()->has_bias_pattern()) {
  90     return true;
  91   }
  92   return (this != prototype());
  93 }
  94 inline bool markOopDesc::must_be_preserved_for_cms_scavenge(klassOop klass_of_obj_containing_mark) const {
  95   if (!UseBiasedLocking)
  96     return (this != prototype());
  97   return must_be_preserved_with_bias_for_cms_scavenge(klass_of_obj_containing_mark);
  98 }
  99 
 100 inline markOop markOopDesc::prototype_for_object(oop obj) {
 101 #ifdef ASSERT
 102   markOop prototype_header = obj->klass()->klass_part()->prototype_header();
 103   assert(prototype_header == prototype() || prototype_header->has_bias_pattern(), "corrupt prototype header");
 104 #endif
 105   return obj->klass()->klass_part()->prototype_header();
 106 }
 107 
 108 #endif // SHARE_VM_OOPS_MARKOOP_INLINE_HPP