59 lines
1.0 KiB
C++
59 lines
1.0 KiB
C++
//
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2018
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#pragma once
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#include "td/utils/port/thread.h"
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#include <atomic>
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namespace td {
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class SpinLock {
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struct Unlock {
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void operator()(SpinLock *ptr) {
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ptr->unlock();
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}
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};
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class InfBackoff {
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int cnt = 0;
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public:
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bool next() {
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cnt++;
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if (cnt < 50) {
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return true;
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} else {
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td::this_thread::yield();
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return true;
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}
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}
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};
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public:
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using Lock = std::unique_ptr<SpinLock, Unlock>;
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Lock lock() {
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InfBackoff backoff;
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while (!try_lock()) {
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backoff.next();
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}
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return Lock(this);
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}
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bool try_lock() {
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return !flag_.test_and_set(std::memory_order_acquire);
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}
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private:
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std::atomic_flag flag_ = ATOMIC_FLAG_INIT;
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void unlock() {
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flag_.clear(std::memory_order_release);
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}
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};
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} // namespace td
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