56 lines
1.8 KiB
C++
56 lines
1.8 KiB
C++
/*
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* Copyright (C) 2020 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <pthread.h>
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#include <android-base/macros.h>
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#include <android-base/thread_annotations.h>
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// As of the end of May 2020, std::shared_mutex is *not* simply a pthread_rwlock, but rather a
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// combination of std::mutex and std::condition variable, which is obviously less efficient. This
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// immitates what std::shared_mutex should be doing and is compatible with RAII thread wrappers.
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class SHARED_CAPABILITY("mutex") RwLock {
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public:
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RwLock() {}
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~RwLock() {}
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void lock() ACQUIRE() { pthread_rwlock_wrlock(&rwlock_); }
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void lock_shared() ACQUIRE_SHARED() { pthread_rwlock_rdlock(&rwlock_); }
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void unlock() RELEASE() { pthread_rwlock_unlock(&rwlock_); }
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private:
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pthread_rwlock_t rwlock_ = PTHREAD_RWLOCK_INITIALIZER;
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};
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// std::shared_lock does not have thread annotations, so we need our own.
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class SCOPED_CAPABILITY SharedLock {
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public:
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SharedLock(RwLock& lock) ACQUIRE_SHARED(lock) : lock_(lock) { lock_.lock_shared(); }
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~SharedLock() RELEASE() { lock_.unlock(); }
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void lock_shared() ACQUIRE_SHARED() { lock_.lock_shared(); }
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void unlock() RELEASE() { lock_.unlock(); }
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DISALLOW_IMPLICIT_CONSTRUCTORS(SharedLock);
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private:
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RwLock& lock_;
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};
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