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 FinalizerReference;
32class Object;
33class Reference;
34}  // namespace mirror
35
36namespace gc {
37
38class Heap;
39
40// Used to process java.lang.References concurrently or paused.
41class ReferenceProcessor {
42 public:
43  explicit ReferenceProcessor();
44  static bool PreserveSoftReferenceCallback(mirror::HeapReference<mirror::Object>* obj, void* arg)
45      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
46  void ProcessReferences(bool concurrent, TimingLogger* timings, bool clear_soft_references,
47                         IsHeapReferenceMarkedCallback* is_marked_callback,
48                         MarkObjectCallback* mark_object_callback,
49                         ProcessMarkStackCallback* process_mark_stack_callback, void* arg)
50      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
51      EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_)
52      LOCKS_EXCLUDED(Locks::reference_processor_lock_);
53  // The slow path bool is contained in the reference class object, can only be set once
54  // Only allow setting this with mutators suspended so that we can avoid using a lock in the
55  // GetReferent fast path as an optimization.
56  void EnableSlowPath() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
57  // Decode the referent, may block if references are being processed.
58  mirror::Object* GetReferent(Thread* self, mirror::Reference* reference)
59      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) LOCKS_EXCLUDED(Locks::reference_processor_lock_);
60  void EnqueueClearedReferences(Thread* self) LOCKS_EXCLUDED(Locks::mutator_lock_);
61  void DelayReferenceReferent(mirror::Class* klass, mirror::Reference* ref,
62                              IsHeapReferenceMarkedCallback* is_marked_callback, void* arg)
63      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
64  void UpdateRoots(IsMarkedCallback* callback, void* arg)
65      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_, Locks::heap_bitmap_lock_);
66  // Make a circular list with reference if it is not enqueued. Uses the finalizer queue lock.
67  bool MakeCircularListIfUnenqueued(mirror::FinalizerReference* reference)
68      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
69      LOCKS_EXCLUDED(Locks::reference_processor_lock_,
70                     Locks::reference_queue_finalizer_references_lock_);
71
72 private:
73  class ProcessReferencesArgs {
74   public:
75    ProcessReferencesArgs(IsHeapReferenceMarkedCallback* is_marked_callback,
76                          MarkObjectCallback* mark_callback, void* arg)
77        : is_marked_callback_(is_marked_callback), mark_callback_(mark_callback), arg_(arg) {
78    }
79
80    // The is marked callback is null when the args aren't set up.
81    IsHeapReferenceMarkedCallback* is_marked_callback_;
82    MarkObjectCallback* mark_callback_;
83    void* arg_;
84
85   private:
86    DISALLOW_IMPLICIT_CONSTRUCTORS(ProcessReferencesArgs);
87  };
88  bool SlowPathEnabled() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
89  // Called by ProcessReferences.
90  void DisableSlowPath(Thread* self) EXCLUSIVE_LOCKS_REQUIRED(Locks::reference_processor_lock_)
91      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
92  // If we are preserving references it means that some dead objects may become live, we use start
93  // and stop preserving to block mutators using GetReferrent from getting access to these
94  // referents.
95  void StartPreservingReferences(Thread* self) LOCKS_EXCLUDED(Locks::reference_processor_lock_);
96  void StopPreservingReferences(Thread* self) LOCKS_EXCLUDED(Locks::reference_processor_lock_);
97  // Process args, used by the GetReferent to return referents which are already marked.
98  ProcessReferencesArgs process_references_args_ GUARDED_BY(Locks::reference_processor_lock_);
99  // Boolean for whether or not we are preserving references (either soft references or finalizers).
100  // If this is true, then we cannot return a referent (see comment in GetReferent).
101  bool preserving_references_ GUARDED_BY(Locks::reference_processor_lock_);
102  // Condition that people wait on if they attempt to get the referent of a reference while
103  // processing is in progress.
104  ConditionVariable condition_ GUARDED_BY(Locks::reference_processor_lock_);
105  // Reference queues used by the GC.
106  ReferenceQueue soft_reference_queue_;
107  ReferenceQueue weak_reference_queue_;
108  ReferenceQueue finalizer_reference_queue_;
109  ReferenceQueue phantom_reference_queue_;
110  ReferenceQueue cleared_references_;
111
112  DISALLOW_COPY_AND_ASSIGN(ReferenceProcessor);
113};
114
115}  // namespace gc
116}  // namespace art
117
118#endif  // ART_RUNTIME_GC_REFERENCE_PROCESSOR_H_
119