1 /*
2  * Copyright (C) 2010 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #include "atomic.h"
18 #include "base/mutex.h"
19 #include "base/stl_util.h"
20 #include "thread-inl.h"
21 
22 namespace art {
23 
24 std::vector<Mutex*>* QuasiAtomic::gSwapMutexes = nullptr;
25 
GetSwapMutex(const volatile int64_t * addr)26 Mutex* QuasiAtomic::GetSwapMutex(const volatile int64_t* addr) {
27   return (*gSwapMutexes)[(reinterpret_cast<uintptr_t>(addr) >> 3U) % kSwapMutexCount];
28 }
29 
Startup()30 void QuasiAtomic::Startup() {
31   if (kNeedSwapMutexes) {
32     gSwapMutexes = new std::vector<Mutex*>;
33     for (size_t i = 0; i < kSwapMutexCount; ++i) {
34       gSwapMutexes->push_back(new Mutex("QuasiAtomic stripe", kSwapMutexesLock));
35     }
36   }
37 }
38 
Shutdown()39 void QuasiAtomic::Shutdown() {
40   if (kNeedSwapMutexes) {
41     STLDeleteElements(gSwapMutexes);
42     delete gSwapMutexes;
43   }
44 }
45 
SwapMutexRead64(volatile const int64_t * addr)46 int64_t QuasiAtomic::SwapMutexRead64(volatile const int64_t* addr) {
47   MutexLock mu(Thread::Current(), *GetSwapMutex(addr));
48   return *addr;
49 }
50 
SwapMutexWrite64(volatile int64_t * addr,int64_t value)51 void QuasiAtomic::SwapMutexWrite64(volatile int64_t* addr, int64_t value) {
52   MutexLock mu(Thread::Current(), *GetSwapMutex(addr));
53   *addr = value;
54 }
55 
56 
SwapMutexCas64(int64_t old_value,int64_t new_value,volatile int64_t * addr)57 bool QuasiAtomic::SwapMutexCas64(int64_t old_value, int64_t new_value, volatile int64_t* addr) {
58   MutexLock mu(Thread::Current(), *GetSwapMutex(addr));
59   if (*addr == old_value) {
60     *addr = new_value;
61     return true;
62   }
63   return false;
64 }
65 
66 }  // namespace art
67