1/*
2 * Copyright (C) 2014 Apple Inc. All rights reserved.
3 * Copyright (C) 2018 Yusuke Suzuki <utatane.tea@gmail.com>.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
15 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
17 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
18 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
19 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
20 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
21 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
22 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#pragma once
28
29#include "BAssert.h"
30#include <atomic>
31#include <mutex>
32#include <thread>
33
34// A fast replacement for std::mutex.
35
36namespace bmalloc {
37
38class Mutex {
39public:
40 constexpr Mutex() = default;
41
42 void lock();
43 bool try_lock();
44 void unlock();
45
46private:
47 BEXPORT void lockSlowCase();
48
49 std::atomic<bool> m_flag { false };
50 std::atomic<bool> m_isSpinning { false };
51};
52
53static inline void sleep(
54 std::unique_lock<Mutex>& lock, std::chrono::milliseconds duration)
55{
56 if (duration == std::chrono::milliseconds(0))
57 return;
58
59 lock.unlock();
60 std::this_thread::sleep_for(duration);
61 lock.lock();
62}
63
64static inline void waitUntilFalse(
65 std::unique_lock<Mutex>& lock, std::chrono::milliseconds sleepDuration,
66 bool& condition)
67{
68 while (condition) {
69 condition = false;
70 sleep(lock, sleepDuration);
71 }
72}
73
74inline bool Mutex::try_lock()
75{
76 return !m_flag.exchange(true, std::memory_order_acquire);
77}
78
79inline void Mutex::lock()
80{
81 if (!try_lock())
82 lockSlowCase();
83}
84
85inline void Mutex::unlock()
86{
87 m_flag.store(false, std::memory_order_release);
88}
89
90} // namespace bmalloc
91