54 lines
2.0 KiB
C++
54 lines
2.0 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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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/LICENSE-2.0
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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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#include <folly/SharedMutex.h>
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#include <folly/Indestructible.h>
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namespace folly {
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// Explicitly instantiate SharedMutex here:
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template class SharedMutexImpl<true>;
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template class SharedMutexImpl<false>;
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namespace shared_mutex_detail {
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std::unique_lock<std::mutex> annotationGuard(void* ptr) {
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if (folly::kIsSanitizeThread) {
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// On TSAN builds, we have an array of mutexes and index into them based on
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// the address. If the array is of prime size things will work out okay
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// without a complicated hash function.
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static constexpr std::size_t kNumAnnotationMutexes = 251;
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static Indestructible<std::array<std::mutex, kNumAnnotationMutexes>>
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kAnnotationMutexes;
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auto index = reinterpret_cast<uintptr_t>(ptr) % kNumAnnotationMutexes;
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return std::unique_lock<std::mutex>((*kAnnotationMutexes)[index]);
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} else {
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return std::unique_lock<std::mutex>();
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}
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}
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uint32_t getMaxDeferredReadersSlow(std::atomic<uint32_t>& cache) {
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uint32_t maxDeferredReaders = std::min(
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static_cast<uint32_t>(
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folly::nextPowTwo(CacheLocality::system().numCpus) << 1),
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shared_mutex_detail::kMaxDeferredReadersAllocated);
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// maxDeferredReaders must be a power of 2
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assert(!(maxDeferredReaders & (maxDeferredReaders - 1)));
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cache.store(maxDeferredReaders, std::memory_order_release);
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return maxDeferredReaders;
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}
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} // namespace shared_mutex_detail
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} // namespace folly
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