| /* |
| * Copyright (C) 2020 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/LICENSE2.0 |
| * |
| * 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. |
| */ |
| |
| #pragma once |
| |
| #include <pthread.h> |
| |
| #include <android-base/macros.h> |
| #include <android-base/thread_annotations.h> |
| |
| // As of the end of May 2020, std::shared_mutex is *not* simply a pthread_rwlock, but rather a |
| // combination of std::mutex and std::condition variable, which is obviously less efficient. This |
| // immitates what std::shared_mutex should be doing and is compatible with RAII thread wrappers. |
| |
| class SHARED_CAPABILITY("mutex") RwLock { |
| public: |
| RwLock() {} |
| ~RwLock() {} |
| |
| void lock() ACQUIRE() { pthread_rwlock_wrlock(&rwlock_); } |
| void lock_shared() ACQUIRE_SHARED() { pthread_rwlock_rdlock(&rwlock_); } |
| |
| void unlock() RELEASE() { pthread_rwlock_unlock(&rwlock_); } |
| |
| private: |
| pthread_rwlock_t rwlock_ = PTHREAD_RWLOCK_INITIALIZER; |
| }; |
| |
| // std::shared_lock does not have thread annotations, so we need our own. |
| |
| class SCOPED_CAPABILITY SharedLock { |
| public: |
| explicit SharedLock(RwLock& lock) ACQUIRE_SHARED(lock) : lock_(lock) { lock_.lock_shared(); } |
| ~SharedLock() RELEASE() { lock_.unlock(); } |
| |
| void lock_shared() ACQUIRE_SHARED() { lock_.lock_shared(); } |
| void unlock() RELEASE() { lock_.unlock(); } |
| |
| DISALLOW_IMPLICIT_CONSTRUCTORS(SharedLock); |
| |
| private: |
| RwLock& lock_; |
| }; |