1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
|
/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_GC_REFERENCE_QUEUE_H_
#define ART_RUNTIME_GC_REFERENCE_QUEUE_H_
#include <iosfwd>
#include <string>
#include <vector>
#include "atomic.h"
#include "base/mutex.h"
#include "base/timing_logger.h"
#include "globals.h"
#include "jni.h"
#include "object_callbacks.h"
#include "offsets.h"
#include "thread_pool.h"
namespace art {
namespace mirror {
class Reference;
} // namespace mirror
namespace gc {
namespace collector {
class GarbageCollector;
} // namespace collector
class Heap;
// Used to temporarily store java.lang.ref.Reference(s) during GC and prior to queueing on the
// appropriate java.lang.ref.ReferenceQueue. The linked list is maintained as an unordered,
// circular, and singly-linked list using the pendingNext fields of the java.lang.ref.Reference
// objects.
class ReferenceQueue {
public:
explicit ReferenceQueue(Mutex* lock);
// Enqueue a reference if it is unprocessed. Thread safe to call from multiple
// threads since it uses a lock to avoid a race between checking for the references presence and
// adding it.
void AtomicEnqueueIfNotEnqueued(Thread* self, mirror::Reference* ref)
REQUIRES_SHARED(Locks::mutator_lock_) REQUIRES(!*lock_);
// Enqueue a reference. The reference must be unprocessed.
// Not thread safe, used when mutators are paused to minimize lock overhead.
void EnqueueReference(mirror::Reference* ref) REQUIRES_SHARED(Locks::mutator_lock_);
// Dequeue a reference from the queue and return that dequeued reference.
mirror::Reference* DequeuePendingReference() REQUIRES_SHARED(Locks::mutator_lock_);
// Enqueues finalizer references with white referents. White referents are blackened, moved to
// the zombie field, and the referent field is cleared.
void EnqueueFinalizerReferences(ReferenceQueue* cleared_references,
collector::GarbageCollector* collector)
REQUIRES_SHARED(Locks::mutator_lock_);
// Walks the reference list marking any references subject to the reference clearing policy.
// References with a black referent are removed from the list. References with white referents
// biased toward saving are blackened and also removed from the list.
void ForwardSoftReferences(MarkObjectVisitor* visitor)
REQUIRES_SHARED(Locks::mutator_lock_);
// Unlink the reference list clearing references objects with white referents. Cleared references
// registered to a reference queue are scheduled for appending by the heap worker thread.
void ClearWhiteReferences(ReferenceQueue* cleared_references,
collector::GarbageCollector* collector)
REQUIRES_SHARED(Locks::mutator_lock_);
void Dump(std::ostream& os) const REQUIRES_SHARED(Locks::mutator_lock_);
size_t GetLength() const REQUIRES_SHARED(Locks::mutator_lock_);
bool IsEmpty() const {
return list_ == nullptr;
}
void Clear() {
list_ = nullptr;
}
mirror::Reference* GetList() REQUIRES_SHARED(Locks::mutator_lock_) {
return list_;
}
// Visits list_, currently only used for the mark compact GC.
void UpdateRoots(IsMarkedVisitor* visitor)
REQUIRES_SHARED(Locks::mutator_lock_);
private:
// Lock, used for parallel GC reference enqueuing. It allows for multiple threads simultaneously
// calling AtomicEnqueueIfNotEnqueued.
Mutex* const lock_;
// The actual reference list. Only a root for the mark compact GC since it will be null for other
// GC types.
mirror::Reference* list_;
DISALLOW_IMPLICIT_CONSTRUCTORS(ReferenceQueue);
};
} // namespace gc
} // namespace art
#endif // ART_RUNTIME_GC_REFERENCE_QUEUE_H_
|