jdk8-mips64-public/hotspot: src/share/vm/oops/arrayOop.hpp@e1162778c1c8 (annotated)

src/share/vm/oops/arrayOop.hpp@e1162778c1c8 (annotated)

src/share/vm/oops/arrayOop.hpp

Thu, 07 Apr 2011 09:53:20 -0700

author: johnc
date: Thu, 07 Apr 2011 09:53:20 -0700
changeset 2781: e1162778c1c8
parent 2314: f95d63e2154a
child 3266: 6fd81579526f
permissions: -rw-r--r--

7009266: G1: assert(obj->is_oop_or_null(true )) failed: Error
Summary: A referent object that is only weakly reachable at the start of concurrent marking but is re-attached to the strongly reachable object graph during marking may not be marked as live. This can cause the reference object to be processed prematurely and leave dangling pointers to the referent object. Implement a read barrier for the java.lang.ref.Reference::referent field by intrinsifying the Reference.get() method, and intercepting accesses though JNI, reflection, and Unsafe, so that when a non-null referent object is read it is also logged in an SATB buffer.
Reviewed-by: kvn, iveresov, never, tonyp, dholmes

 /*
  * Copyright (c) 1997, 2010, 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.
  *
  */
 #ifndef SHARE_VM_OOPS_ARRAYOOP_HPP
 #define SHARE_VM_OOPS_ARRAYOOP_HPP
 #include "memory/universe.inline.hpp"
 #include "oops/oop.hpp"
 // arrayOopDesc is the abstract baseclass for all arrays.  It doesn't
 // declare pure virtual to enforce this because that would allocate a vtbl
 // in each instance, which we don't want.
 // The layout of array Oops is:
 //
 //  markOop
 //  klassOop  // 32 bits if compressed but declared 64 in LP64.
 //  length    // shares klass memory or allocated after declared fields.
 class arrayOopDesc : public oopDesc {
   friend class VMStructs;
   // Interpreter/Compiler offsets
   // Header size computation.
   // The header is considered the oop part of this type plus the length.
   // Returns the aligned header_size_in_bytes.  This is not equivalent to
   // sizeof(arrayOopDesc) which should not appear in the code.
   static int header_size_in_bytes() {
     size_t hs = align_size_up(length_offset_in_bytes() + sizeof(int),
                               HeapWordSize);
 #ifdef ASSERT
     // make sure it isn't called before UseCompressedOops is initialized.
     static size_t arrayoopdesc_hs = 0;
     if (arrayoopdesc_hs == 0) arrayoopdesc_hs = hs;
     assert(arrayoopdesc_hs == hs, "header size can't change");
 #endif // ASSERT
     return (int)hs;
   }
  public:
   // The _length field is not declared in C++.  It is allocated after the
   // declared nonstatic fields in arrayOopDesc if not compressed, otherwise
   // it occupies the second half of the _klass field in oopDesc.
   static int length_offset_in_bytes() {
     return UseCompressedOops ? klass_gap_offset_in_bytes() :
                                sizeof(arrayOopDesc);
   }
   // Returns the offset of the first element.
   static int base_offset_in_bytes(BasicType type) {
     return header_size(type) * HeapWordSize;
   }
   // Returns the address of the first element.
   void* base(BasicType type) const {
     return (void*) (((intptr_t) this) + base_offset_in_bytes(type));
   }
   // Tells whether index is within bounds.
   bool is_within_bounds(int index) const        { return 0 <= index && index < length(); }
   // Accessors for instance variable which is not a C++ declared nonstatic
   // field.
   int length() const {
     return *(int*)(((intptr_t)this) + length_offset_in_bytes());
   }
   void set_length(int length) {
     *(int*)(((intptr_t)this) + length_offset_in_bytes()) = length;
   }
   // Should only be called with constants as argument
   // (will not constant fold otherwise)
   // Returns the header size in words aligned to the requirements of the
   // array object type.
   static int header_size(BasicType type) {
     size_t typesize_in_bytes = header_size_in_bytes();
     return (int)(Universe::element_type_should_be_aligned(type)
       ? align_object_offset(typesize_in_bytes/HeapWordSize)
       : typesize_in_bytes/HeapWordSize);
   }
   // Return the maximum length of an array of BasicType.  The length can passed
   // to typeArrayOop::object_size(scale, length, header_size) without causing an
   // overflow.
   static int32_t max_array_length(BasicType type) {
     assert(type >= 0 && type < T_CONFLICT, "wrong type");
     assert(type2aelembytes(type) != 0, "wrong type");
     const int bytes_per_element = type2aelembytes(type);
     if (bytes_per_element < HeapWordSize) {
       return max_jint;
     }
     const int32_t max_words = align_size_down(max_jint, MinObjAlignment);
     const int32_t max_element_words = max_words - header_size(type);
     const int32_t words_per_element = bytes_per_element >> LogHeapWordSize;
     return max_element_words / words_per_element;
   }
 };
 #endif // SHARE_VM_OOPS_ARRAYOOP_HPP

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src/share/vm/oops/arrayOop.hpp@e1162778c1c8 (annotated)

src/share/vm/oops/arrayOop.hpp