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