SharedMutex.cpp

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/*
 * Copyright 2015-present Facebook, Inc.
 *
 * 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/LICENSE-2.0
 *
 * 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.
 */

#include <folly/SharedMutex.h>

namespace folly {
// Explicitly instantiate SharedMutex here:
template class SharedMutexImpl<true>;
template class SharedMutexImpl<false>;

namespace detail {
std::unique_lock<std::mutex> sharedMutexAnnotationGuard(void* ptr) {
  if (folly::kIsSanitizeThread) {
    // On TSAN builds, we have an array of mutexes and index into them based on
    // the address. If the array is of prime size things will work out okay
    // without a complicated hash function.
    static constexpr std::size_t kNumAnnotationMutexes = 251;
    static std::array<std::mutex, kNumAnnotationMutexes> kAnnotationMutexes{};
    auto index = reinterpret_cast<uintptr_t>(ptr) % kNumAnnotationMutexes;
    return std::unique_lock<std::mutex>(kAnnotationMutexes[index]);
  } else {
    return std::unique_lock<std::mutex>();
  }
}
} // namespace detail

} // namespace folly