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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you 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 "contrib/libs/apache/arrow_next/cpp/src/arrow/util/mutex.h"
#include <mutex>
#ifndef _WIN32
# include <pthread.h>
# include <atomic>
#endif
#include "contrib/libs/apache/arrow_next/src/arrow/util/config.h"
#include "contrib/libs/apache/arrow_next/cpp/src/arrow/util/logging.h"
namespace arrow20 {
namespace util {
struct Mutex::Impl {
std::mutex mutex_;
};
Mutex::Guard::Guard(Mutex* locked)
: locked_(locked, [](Mutex* locked) {
#ifdef ARROW_ENABLE_THREADING
DCHECK(!locked->impl_->mutex_.try_lock());
#endif
locked->impl_->mutex_.unlock();
}) {
}
Mutex::Guard Mutex::TryLock() {
DCHECK_NE(impl_, nullptr);
if (impl_->mutex_.try_lock()) {
return Guard{this};
}
return Guard{};
}
Mutex::Guard Mutex::Lock() {
DCHECK_NE(impl_, nullptr);
impl_->mutex_.lock();
return Guard{this};
}
Mutex::Mutex() : impl_(new Impl, [](Impl* impl) { delete impl; }) {}
#ifndef _WIN32
namespace {
struct AfterForkState {
// A global instance that will also register the atfork handler when
// constructed.
static AfterForkState instance;
// The mutex may be used at shutdown, so make it eternal.
// The leak (only in child processes) is a small price to pay for robustness.
Mutex* mutex = nullptr;
private:
AfterForkState() {
pthread_atfork(/*prepare=*/nullptr, /*parent=*/nullptr, /*child=*/&AfterFork);
}
static void AfterFork() { instance.mutex = new Mutex; }
};
AfterForkState AfterForkState::instance;
} // namespace
Mutex* GlobalForkSafeMutex() { return AfterForkState::instance.mutex; }
#endif // _WIN32
} // namespace util
} // namespace arrow20
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