1/*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
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24
25#ifndef SHARE_JFR_LEAKPROFILER_CHAINS_OBJECTSAMPLEMARKER_HPP
26#define SHARE_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//
37class 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_JFR_LEAKPROFILER_CHAINS_OBJECTSAMPLEMARKER_HPP
82