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
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
|
/*
* 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.
*/
#include "reference_queue.h"
#include "accounting/card_table-inl.h"
#include "collector/concurrent_copying.h"
#include "heap.h"
#include "mirror/class-inl.h"
#include "mirror/object-inl.h"
#include "mirror/reference-inl.h"
namespace art {
namespace gc {
ReferenceQueue::ReferenceQueue(Mutex* lock) : lock_(lock), list_(nullptr) {
}
void ReferenceQueue::AtomicEnqueueIfNotEnqueued(Thread* self, mirror::Reference* ref) {
DCHECK(ref != nullptr);
MutexLock mu(self, *lock_);
if (ref->IsUnprocessed()) {
EnqueueReference(ref);
}
}
void ReferenceQueue::EnqueueReference(mirror::Reference* ref) {
DCHECK(ref != nullptr);
CHECK(ref->IsUnprocessed());
if (IsEmpty()) {
// 1 element cyclic queue, ie: Reference ref = ..; ref.pendingNext = ref;
list_ = ref;
} else {
// The list is owned by the GC, everything that has been inserted must already be at least
// gray.
mirror::Reference* head = list_->GetPendingNext<kWithoutReadBarrier>();
DCHECK(head != nullptr);
ref->SetPendingNext(head);
}
// Add the reference in the middle to preserve the cycle.
list_->SetPendingNext(ref);
}
mirror::Reference* ReferenceQueue::DequeuePendingReference() {
DCHECK(!IsEmpty());
mirror::Reference* ref = list_->GetPendingNext<kWithoutReadBarrier>();
DCHECK(ref != nullptr);
// Note: the following code is thread-safe because it is only called from ProcessReferences which
// is single threaded.
if (list_ == ref) {
list_ = nullptr;
} else {
mirror::Reference* next = ref->GetPendingNext<kWithoutReadBarrier>();
list_->SetPendingNext(next);
}
ref->SetPendingNext(nullptr);
Heap* heap = Runtime::Current()->GetHeap();
if (kUseBakerOrBrooksReadBarrier && heap->CurrentCollectorType() == kCollectorTypeCC &&
heap->ConcurrentCopyingCollector()->IsActive()) {
// Change the gray ptr we left in ConcurrentCopying::ProcessMarkStackRef() to white.
// We check IsActive() above because we don't want to do this when the zygote compaction
// collector (SemiSpace) is running.
CHECK(ref != nullptr);
collector::ConcurrentCopying* concurrent_copying = heap->ConcurrentCopyingCollector();
mirror::Object* rb_ptr = ref->GetReadBarrierPointer();
if (rb_ptr == ReadBarrier::GrayPtr()) {
ref->AtomicSetReadBarrierPointer(ReadBarrier::GrayPtr(), ReadBarrier::WhitePtr());
CHECK_EQ(ref->GetReadBarrierPointer(), ReadBarrier::WhitePtr());
} else {
// In ConcurrentCopying::ProcessMarkStackRef() we may leave a white reference in the queue and
// find it here, which is OK.
CHECK_EQ(rb_ptr, ReadBarrier::WhitePtr()) << "ref=" << ref << " rb_ptr=" << rb_ptr;
mirror::Object* referent = ref->GetReferent<kWithoutReadBarrier>();
// The referent could be null if it's cleared by a mutator (Reference.clear()).
if (referent != nullptr) {
CHECK(concurrent_copying->IsInToSpace(referent))
<< "ref=" << ref << " rb_ptr=" << ref->GetReadBarrierPointer()
<< " referent=" << referent;
}
}
}
return ref;
}
void ReferenceQueue::Dump(std::ostream& os) const {
mirror::Reference* cur = list_;
os << "Reference starting at list_=" << list_ << "\n";
if (cur == nullptr) {
return;
}
do {
mirror::Reference* pending_next = cur->GetPendingNext();
os << "Reference= " << cur << " PendingNext=" << pending_next;
if (cur->IsFinalizerReferenceInstance()) {
os << " Zombie=" << cur->AsFinalizerReference()->GetZombie();
}
os << "\n";
cur = pending_next;
} while (cur != list_);
}
size_t ReferenceQueue::GetLength() const {
size_t count = 0;
mirror::Reference* cur = list_;
if (cur != nullptr) {
do {
++count;
cur = cur->GetPendingNext();
} while (cur != list_);
}
return count;
}
void ReferenceQueue::ClearWhiteReferences(ReferenceQueue* cleared_references,
collector::GarbageCollector* collector) {
while (!IsEmpty()) {
mirror::Reference* ref = DequeuePendingReference();
mirror::HeapReference<mirror::Object>* referent_addr = ref->GetReferentReferenceAddr();
if (referent_addr->AsMirrorPtr() != nullptr &&
!collector->IsMarkedHeapReference(referent_addr)) {
// Referent is white, clear it.
if (Runtime::Current()->IsActiveTransaction()) {
ref->ClearReferent<true>();
} else {
ref->ClearReferent<false>();
}
cleared_references->EnqueueReference(ref);
}
}
}
void ReferenceQueue::EnqueueFinalizerReferences(ReferenceQueue* cleared_references,
collector::GarbageCollector* collector) {
while (!IsEmpty()) {
mirror::FinalizerReference* ref = DequeuePendingReference()->AsFinalizerReference();
mirror::HeapReference<mirror::Object>* referent_addr = ref->GetReferentReferenceAddr();
if (referent_addr->AsMirrorPtr() != nullptr &&
!collector->IsMarkedHeapReference(referent_addr)) {
mirror::Object* forward_address = collector->MarkObject(referent_addr->AsMirrorPtr());
// Move the updated referent to the zombie field.
if (Runtime::Current()->IsActiveTransaction()) {
ref->SetZombie<true>(forward_address);
ref->ClearReferent<true>();
} else {
ref->SetZombie<false>(forward_address);
ref->ClearReferent<false>();
}
cleared_references->EnqueueReference(ref);
}
}
}
void ReferenceQueue::ForwardSoftReferences(MarkObjectVisitor* visitor) {
if (UNLIKELY(IsEmpty())) {
return;
}
mirror::Reference* const head = list_;
mirror::Reference* ref = head;
do {
mirror::HeapReference<mirror::Object>* referent_addr = ref->GetReferentReferenceAddr();
if (referent_addr->AsMirrorPtr() != nullptr) {
visitor->MarkHeapReference(referent_addr);
}
ref = ref->GetPendingNext();
} while (LIKELY(ref != head));
}
void ReferenceQueue::UpdateRoots(IsMarkedVisitor* visitor) {
if (list_ != nullptr) {
list_ = down_cast<mirror::Reference*>(visitor->IsMarked(list_));
}
}
} // namespace gc
} // namespace art
|
