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
|
/*
* Copyright (C) 2011 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_LOCK_WORD_H_
#define ART_RUNTIME_LOCK_WORD_H_
#include <iosfwd>
#include <stdint.h>
#include "base/logging.h"
#include "utils.h"
namespace art {
namespace mirror {
class Object;
} // namespace mirror
class Monitor;
/* The lock value itself as stored in mirror::Object::monitor_. The two most significant bits of
* the state. The three possible states are fat locked, thin/unlocked, and hash code.
* When the lock word is in the "thin" state and its bits are formatted as follows:
*
* |33|22222222221111|1111110000000000|
* |10|98765432109876|5432109876543210|
* |00| lock count |thread id owner |
*
* When the lock word is in the "fat" state and its bits are formatted as follows:
*
* |33|222222222211111111110000000000|
* |10|987654321098765432109876543210|
* |01| MonitorId |
*
* When the lock word is in hash state and its bits are formatted as follows:
*
* |33|222222222211111111110000000000|
* |10|987654321098765432109876543210|
* |10| HashCode |
*/
class LockWord {
public:
enum {
// Number of bits to encode the state, currently just fat or thin/unlocked or hash code.
kStateSize = 2,
// Number of bits to encode the thin lock owner.
kThinLockOwnerSize = 16,
// Remaining bits are the recursive lock count.
kThinLockCountSize = 32 - kThinLockOwnerSize - kStateSize,
// Thin lock bits. Owner in lowest bits.
kThinLockOwnerShift = 0,
kThinLockOwnerMask = (1 << kThinLockOwnerSize) - 1,
// Count in higher bits.
kThinLockCountShift = kThinLockOwnerSize + kThinLockOwnerShift,
kThinLockCountMask = (1 << kThinLockCountShift) - 1,
kThinLockMaxCount = kThinLockCountMask,
// State in the highest bits.
kStateShift = kThinLockCountSize + kThinLockCountShift,
kStateMask = (1 << kStateSize) - 1,
kStateThinOrUnlocked = 0,
kStateFat = 1,
kStateHash = 2,
kStateForwardingAddress = 3,
// When the state is kHashCode, the non-state bits hold the hashcode.
kHashShift = 0,
kHashSize = 32 - kStateSize,
kHashMask = (1 << kHashSize) - 1,
};
static LockWord FromThinLockId(uint32_t thread_id, uint32_t count) {
CHECK_LE(thread_id, static_cast<uint32_t>(kThinLockOwnerMask));
return LockWord((thread_id << kThinLockOwnerShift) | (count << kThinLockCountShift) |
(kStateThinOrUnlocked << kStateShift));
}
static LockWord FromForwardingAddress(size_t target) {
DCHECK(IsAligned < 1 << kStateSize>(target));
return LockWord((target >> kStateSize) | (kStateForwardingAddress << kStateShift));
}
static LockWord FromHashCode(uint32_t hash_code) {
CHECK_LE(hash_code, static_cast<uint32_t>(kHashMask));
return LockWord((hash_code << kHashShift) | (kStateHash << kStateShift));
}
enum LockState {
kUnlocked, // No lock owners.
kThinLocked, // Single uncontended owner.
kFatLocked, // See associated monitor.
kHashCode, // Lock word contains an identity hash.
kForwardingAddress, // Lock word contains the forwarding address of an object.
};
LockState GetState() const {
if (UNLIKELY(value_ == 0)) {
return kUnlocked;
} else {
uint32_t internal_state = (value_ >> kStateShift) & kStateMask;
switch (internal_state) {
case kStateThinOrUnlocked:
return kThinLocked;
case kStateHash:
return kHashCode;
case kStateForwardingAddress:
return kForwardingAddress;
default:
DCHECK_EQ(internal_state, static_cast<uint32_t>(kStateFat));
return kFatLocked;
}
}
}
// Return the owner thin lock thread id.
uint32_t ThinLockOwner() const;
// Return the number of times a lock value has been locked.
uint32_t ThinLockCount() const;
// Return the Monitor encoded in a fat lock.
Monitor* FatLockMonitor() const;
// Return the forwarding address stored in the monitor.
size_t ForwardingAddress() const;
// Default constructor with no lock ownership.
LockWord();
// Constructor a lock word for inflation to use a Monitor.
explicit LockWord(Monitor* mon);
bool operator==(const LockWord& rhs) const {
return GetValue() == rhs.GetValue();
}
// Return the hash code stored in the lock word, must be kHashCode state.
int32_t GetHashCode() const;
uint32_t GetValue() const {
return value_;
}
private:
explicit LockWord(uint32_t val) : value_(val) {}
// Only Object should be converting LockWords to/from uints.
friend class mirror::Object;
// The encoded value holding all the state.
uint32_t value_;
};
std::ostream& operator<<(std::ostream& os, const LockWord::LockState& code);
} // namespace art
#endif // ART_RUNTIME_LOCK_WORD_H_
|
