1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ART_RUNTIME_GC_REFERENCE_PROCESSOR_H_
18#define ART_RUNTIME_GC_REFERENCE_PROCESSOR_H_
19
20#include "base/mutex.h"
21#include "globals.h"
22#include "jni.h"
23#include "object_callbacks.h"
24#include "reference_queue.h"
25
26namespace art {
27
28class TimingLogger;
29
30namespace mirror {
31class Class;
32class FinalizerReference;
33class Object;
34class Reference;
35}  // namespace mirror
36
37namespace gc {
38
39namespace collector {
40class GarbageCollector;
41}  // namespace collector
42
43class Heap;
44
45// Used to process java.lang.ref.Reference instances concurrently or paused.
46class ReferenceProcessor {
47 public:
48  explicit ReferenceProcessor();
49  void ProcessReferences(bool concurrent,
50                         TimingLogger* timings,
51                         bool clear_soft_references,
52                         gc::collector::GarbageCollector* collector)
53      REQUIRES_SHARED(Locks::mutator_lock_)
54      REQUIRES(Locks::heap_bitmap_lock_)
55      REQUIRES(!Locks::reference_processor_lock_);
56  // The slow path bool is contained in the reference class object, can only be set once
57  // Only allow setting this with mutators suspended so that we can avoid using a lock in the
58  // GetReferent fast path as an optimization.
59  void EnableSlowPath() REQUIRES_SHARED(Locks::mutator_lock_);
60  void BroadcastForSlowPath(Thread* self);
61  // Decode the referent, may block if references are being processed.
62  ObjPtr<mirror::Object> GetReferent(Thread* self, ObjPtr<mirror::Reference> reference)
63      REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(!Locks::reference_processor_lock_);
64  void EnqueueClearedReferences(Thread* self) REQUIRES(!Locks::mutator_lock_);
65  void DelayReferenceReferent(ObjPtr<mirror::Class> klass,
66                              ObjPtr<mirror::Reference> ref,
67                              collector::GarbageCollector* collector)
68      REQUIRES_SHARED(Locks::mutator_lock_);
69  void UpdateRoots(IsMarkedVisitor* visitor)
70      REQUIRES_SHARED(Locks::mutator_lock_, Locks::heap_bitmap_lock_);
71  // Make a circular list with reference if it is not enqueued. Uses the finalizer queue lock.
72  bool MakeCircularListIfUnenqueued(ObjPtr<mirror::FinalizerReference> reference)
73      REQUIRES_SHARED(Locks::mutator_lock_)
74      REQUIRES(!Locks::reference_processor_lock_,
75               !Locks::reference_queue_finalizer_references_lock_);
76  void ClearReferent(ObjPtr<mirror::Reference> ref)
77      REQUIRES_SHARED(Locks::mutator_lock_)
78      REQUIRES(!Locks::reference_processor_lock_);
79
80 private:
81  bool SlowPathEnabled() REQUIRES_SHARED(Locks::mutator_lock_);
82  // Called by ProcessReferences.
83  void DisableSlowPath(Thread* self) REQUIRES(Locks::reference_processor_lock_)
84      REQUIRES_SHARED(Locks::mutator_lock_);
85  // If we are preserving references it means that some dead objects may become live, we use start
86  // and stop preserving to block mutators using GetReferrent from getting access to these
87  // referents.
88  void StartPreservingReferences(Thread* self) REQUIRES(!Locks::reference_processor_lock_);
89  void StopPreservingReferences(Thread* self) REQUIRES(!Locks::reference_processor_lock_);
90  // Wait until reference processing is done.
91  void WaitUntilDoneProcessingReferences(Thread* self)
92      REQUIRES_SHARED(Locks::mutator_lock_)
93      REQUIRES(Locks::reference_processor_lock_);
94  // Collector which is clearing references, used by the GetReferent to return referents which are
95  // already marked.
96  collector::GarbageCollector* collector_ GUARDED_BY(Locks::reference_processor_lock_);
97  // Boolean for whether or not we are preserving references (either soft references or finalizers).
98  // If this is true, then we cannot return a referent (see comment in GetReferent).
99  bool preserving_references_ GUARDED_BY(Locks::reference_processor_lock_);
100  // Condition that people wait on if they attempt to get the referent of a reference while
101  // processing is in progress.
102  ConditionVariable condition_ GUARDED_BY(Locks::reference_processor_lock_);
103  // Reference queues used by the GC.
104  ReferenceQueue soft_reference_queue_;
105  ReferenceQueue weak_reference_queue_;
106  ReferenceQueue finalizer_reference_queue_;
107  ReferenceQueue phantom_reference_queue_;
108  ReferenceQueue cleared_references_;
109
110  DISALLOW_COPY_AND_ASSIGN(ReferenceProcessor);
111};
112
113}  // namespace gc
114}  // namespace art
115
116#endif  // ART_RUNTIME_GC_REFERENCE_PROCESSOR_H_
117