1 /*

     2  * Copyright (c) 2017, 2018, 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_JFR_LEAKPROFILER_CHAINS_OBJECTSAMPLEMARKER_HPP

    26 #define SHARE_VM_JFR_LEAKPROFILER_CHAINS_OBJECTSAMPLEMARKER_HPP

    27 

    28 #include "memory/allocation.hpp"

    29 #include "oops/markOop.hpp"

    30 #include "utilities/growableArray.hpp"

    31 //

    32 // This class will save the original mark oop of a object sample object.

    33 // It will then install an "identifier" mark oop to be used for

    34 // identification purposes in the search for reference chains.

    35 // The destructor will restore each modified oop with its original mark oop.

    36 //

    37 class ObjectSampleMarker : public StackObj {

    38  private:

    39   class ObjectSampleMarkOop : public ResourceObj {

    40     friend class ObjectSampleMarker;

    41    private:

    42     oop _obj;

    43     markOop _mark_oop;

    44     ObjectSampleMarkOop(const oop obj,

    45                         const markOop mark_oop) : _obj(obj),

    46                                                   _mark_oop(mark_oop) {}

    47    public:

    48     ObjectSampleMarkOop() : _obj(NULL), _mark_oop(NULL) {}

    49   };

    50 

    51   GrowableArray<ObjectSampleMarkOop>* _store;

    52 

    53  public:

    54   ObjectSampleMarker() :

    55        _store(new GrowableArray<ObjectSampleMarkOop>(16)) {}

    56   ~ObjectSampleMarker() {

    57     assert(_store != NULL, "invariant");

    58     // restore the saved, original, markOop for sample objects

    59     while (_store->is_nonempty()) {

    60       ObjectSampleMarkOop sample_oop = _store->pop();

    61       sample_oop._obj->set_mark(sample_oop._mark_oop);

    62       assert(sample_oop._obj->mark() == sample_oop._mark_oop, "invariant");

    63     }

    64   }

    65 

    66   void mark(oop obj) {

    67     assert(obj != NULL, "invariant");

    68     // save the original markOop

    69     _store->push(ObjectSampleMarkOop(obj, obj->mark()));

    70     // now we will "poison" the mark word of the sample object

    71     // to the intermediate monitor INFLATING state.

    72     // This is an "impossible" state during a safepoint,

    73     // hence we will use it to quickly identify sample objects

    74     // during the reachability search from gc roots.

    75     assert(NULL == markOopDesc::INFLATING(), "invariant");

    76     obj->set_mark(markOopDesc::INFLATING());

    77     assert(NULL == obj->mark(), "invariant");

    78   }

    79 };

    80 

    81 #endif // SHARE_VM_JFR_LEAKPROFILER_CHAINS_OBJECTSAMPLEMARKER_HPP