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      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 
     26 Mutex* QuasiAtomic::GetSwapMutex(const volatile int64_t* addr) {
     27   return (*gSwapMutexes)[(reinterpret_cast<uintptr_t>(addr) >> 3U) % kSwapMutexCount];
     28 }
     29 
     30 void QuasiAtomic::Startup() {
     31   if (NeedSwapMutexes(kRuntimeISA)) {
     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 
     39 void QuasiAtomic::Shutdown() {
     40   if (NeedSwapMutexes(kRuntimeISA)) {
     41     STLDeleteElements(gSwapMutexes);
     42     delete gSwapMutexes;
     43   }
     44 }
     45 
     46 int64_t QuasiAtomic::SwapMutexRead64(volatile const int64_t* addr) {
     47   MutexLock mu(Thread::Current(), *GetSwapMutex(addr));
     48   return *addr;
     49 }
     50 
     51 void QuasiAtomic::SwapMutexWrite64(volatile int64_t* addr, int64_t value) {
     52   MutexLock mu(Thread::Current(), *GetSwapMutex(addr));
     53   *addr = value;
     54 }
     55 
     56 
     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