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