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
|
/*
* 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 <time.h>
#include <cutils/atomic.h>
#include <utils/Log.h>
#include "StateQueue.h"
namespace android {
// 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)
{
}
template<typename T> StateQueue<T>::~StateQueue()
{
}
// Observer APIs
template<typename T> const T* StateQueue<T>::poll()
{
const T *next = (const T *) android_atomic_acquire_load((volatile int32_t *) &mNext);
if (next != mCurrent) {
mAck = next; // no additional barrier needed
mCurrent = next;
}
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");
if (mIsDirty) {
// wait for prior push to be acknowledged
if (mExpecting != NULL) {
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;
}
nanosleep(&req, NULL);
}
}
// publish
android_atomic_release_store((int32_t) mMutating, (volatile int32_t *) &mNext);
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) {
for (;;) {
const T *ack = (const T *) mAck; // no additional barrier needed
if (ack == mExpecting) {
mExpecting = NULL;
break;
}
nanosleep(&req, NULL);
}
}
}
return true;
}
} // namespace android
// hack for gcc
#ifdef STATE_QUEUE_INSTANTIATIONS
#include STATE_QUEUE_INSTANTIATIONS
#endif
|
