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
189
190
191
192
193
194
195
196
197
198
199
|
/*
* Copyright (C) 2012 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.
*/
#define LOG_TAG "StateQueue"
//#define LOG_NDEBUG 0
#include "Configuration.h"
#include <time.h>
#include <cutils/atomic.h>
#include <utils/Log.h>
#include "StateQueue.h"
namespace android {
#ifdef STATE_QUEUE_DUMP
void StateQueueObserverDump::dump(int fd)
{
fdprintf(fd, "State queue observer: stateChanges=%u\n", mStateChanges);
}
void StateQueueMutatorDump::dump(int fd)
{
fdprintf(fd, "State queue mutator: pushDirty=%u pushAck=%u blockedSequence=%u\n",
mPushDirty, mPushAck, mBlockedSequence);
}
#endif
// Constructor and destructor
template<typename T> StateQueue<T>::StateQueue() :
mNext(NULL), mAck(NULL), mCurrent(NULL),
mMutating(&mStates[0]), mExpecting(NULL),
mInMutation(false), mIsDirty(false), mIsInitialized(false)
#ifdef STATE_QUEUE_DUMP
, mObserverDump(&mObserverDummyDump), mMutatorDump(&mMutatorDummyDump)
#endif
{
}
template<typename T> StateQueue<T>::~StateQueue()
{
}
// Observer APIs
template<typename T> const T* StateQueue<T>::poll()
{
#ifdef __LP64__
const T *next = (const T *) android_atomic_acquire_load64((volatile int64_t *) &mNext);
#else
const T *next = (const T *) android_atomic_acquire_load((volatile int32_t *) &mNext);
#endif
if (next != mCurrent) {
mAck = next; // no additional barrier needed
mCurrent = next;
#ifdef STATE_QUEUE_DUMP
mObserverDump->mStateChanges++;
#endif
}
return next;
}
// Mutator APIs
template<typename T> T* StateQueue<T>::begin()
{
ALOG_ASSERT(!mInMutation, "begin() called when in a mutation");
mInMutation = true;
return mMutating;
}
template<typename T> void StateQueue<T>::end(bool didModify)
{
ALOG_ASSERT(mInMutation, "end() called when not in a mutation");
ALOG_ASSERT(mIsInitialized || didModify, "first end() must modify for initialization");
if (didModify) {
mIsDirty = true;
mIsInitialized = true;
}
mInMutation = false;
}
template<typename T> bool StateQueue<T>::push(StateQueue<T>::block_t block)
{
#define PUSH_BLOCK_ACK_NS 3000000L // 3 ms: time between checks for ack in push()
// FIXME should be configurable
static const struct timespec req = {0, PUSH_BLOCK_ACK_NS};
ALOG_ASSERT(!mInMutation, "push() called when in a mutation");
#ifdef STATE_QUEUE_DUMP
if (block == BLOCK_UNTIL_ACKED) {
mMutatorDump->mPushAck++;
}
#endif
if (mIsDirty) {
#ifdef STATE_QUEUE_DUMP
mMutatorDump->mPushDirty++;
#endif
// wait for prior push to be acknowledged
if (mExpecting != NULL) {
#ifdef STATE_QUEUE_DUMP
unsigned count = 0;
#endif
for (;;) {
const T *ack = (const T *) mAck; // no additional barrier needed
if (ack == mExpecting) {
// unnecessary as we're about to rewrite
//mExpecting = NULL;
break;
}
if (block == BLOCK_NEVER) {
return false;
}
#ifdef STATE_QUEUE_DUMP
if (count == 1) {
mMutatorDump->mBlockedSequence++;
}
++count;
#endif
nanosleep(&req, NULL);
}
#ifdef STATE_QUEUE_DUMP
if (count > 1) {
mMutatorDump->mBlockedSequence++;
}
#endif
}
// publish
#ifdef __LP64__
android_atomic_release_store64((int64_t) mMutating, (volatile int64_t *) &mNext);
#else
android_atomic_release_store((int32_t) mMutating, (volatile int32_t *) &mNext);
#endif
mExpecting = mMutating;
// copy with circular wraparound
if (++mMutating >= &mStates[kN]) {
mMutating = &mStates[0];
}
*mMutating = *mExpecting;
mIsDirty = false;
}
// optionally wait for this push or a prior push to be acknowledged
if (block == BLOCK_UNTIL_ACKED) {
if (mExpecting != NULL) {
#ifdef STATE_QUEUE_DUMP
unsigned count = 0;
#endif
for (;;) {
const T *ack = (const T *) mAck; // no additional barrier needed
if (ack == mExpecting) {
mExpecting = NULL;
break;
}
#ifdef STATE_QUEUE_DUMP
if (count == 1) {
mMutatorDump->mBlockedSequence++;
}
++count;
#endif
nanosleep(&req, NULL);
}
#ifdef STATE_QUEUE_DUMP
if (count > 1) {
mMutatorDump->mBlockedSequence++;
}
#endif
}
}
return true;
}
} // namespace android
// hack for gcc
#ifdef STATE_QUEUE_INSTANTIATIONS
#include STATE_QUEUE_INSTANTIATIONS
#endif
|
