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/* -*- mode: c++; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 4 -*- */
#ifndef ATOMIC_QUEUE_SPIN_LOCK_H_INCLUDED
#define ATOMIC_QUEUE_SPIN_LOCK_H_INCLUDED
// Copyright (c) 2019 Maxim Egorushkin. MIT License. See the full licence in file LICENSE.
#include "defs.h"
#include <atomic>
#include <cstdlib>
#include <mutex>
#include <pthread.h>
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
namespace atomic_queue {
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
class Spinlock {
pthread_spinlock_t s_;
public:
using scoped_lock = std::lock_guard<Spinlock>;
Spinlock() noexcept {
if(ATOMIC_QUEUE_UNLIKELY(::pthread_spin_init(&s_, 0)))
std::abort();
}
Spinlock(Spinlock const&) = delete;
Spinlock& operator=(Spinlock const&) = delete;
~Spinlock() noexcept {
::pthread_spin_destroy(&s_);
}
void lock() noexcept {
if(ATOMIC_QUEUE_UNLIKELY(::pthread_spin_lock(&s_)))
std::abort();
}
void unlock() noexcept {
if(ATOMIC_QUEUE_UNLIKELY(::pthread_spin_unlock(&s_)))
std::abort();
}
};
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
class TicketSpinlock {
alignas(CACHE_LINE_SIZE) std::atomic<unsigned> ticket_{0};
alignas(CACHE_LINE_SIZE) std::atomic<unsigned> next_{0};
public:
class LockGuard {
TicketSpinlock* const m_;
unsigned const ticket_;
public:
LockGuard(TicketSpinlock& m) noexcept
: m_(&m)
, ticket_(m.lock())
{}
LockGuard(LockGuard const&) = delete;
LockGuard& operator=(LockGuard const&) = delete;
~LockGuard() noexcept {
m_->unlock(ticket_);
}
};
using scoped_lock = LockGuard;
TicketSpinlock() noexcept = default;
TicketSpinlock(TicketSpinlock const&) = delete;
TicketSpinlock& operator=(TicketSpinlock const&) = delete;
ATOMIC_QUEUE_NOINLINE unsigned lock() noexcept {
auto ticket = ticket_.fetch_add(1, std::memory_order_relaxed);
for(;;) {
auto position = ticket - next_.load(std::memory_order_acquire);
if(ATOMIC_QUEUE_LIKELY(!position))
break;
do
spin_loop_pause();
while(--position);
}
return ticket;
}
void unlock() noexcept {
unlock(next_.load(std::memory_order_relaxed) + 1);
}
void unlock(unsigned ticket) noexcept {
next_.store(ticket + 1, std::memory_order_release);
}
};
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
class UnfairSpinlock {
std::atomic<unsigned> lock_{0};
public:
using scoped_lock = std::lock_guard<UnfairSpinlock>;
UnfairSpinlock(UnfairSpinlock const&) = delete;
UnfairSpinlock& operator=(UnfairSpinlock const&) = delete;
void lock() noexcept {
for(;;) {
if(!lock_.load(std::memory_order_relaxed) && !lock_.exchange(1, std::memory_order_acquire))
return;
spin_loop_pause();
}
}
void unlock() noexcept {
lock_.store(0, std::memory_order_release);
}
};
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// class SpinlockHle {
// int lock_ = 0;
// #ifdef __gcc__
// static constexpr int HLE_ACQUIRE = __ATOMIC_HLE_ACQUIRE;
// static constexpr int HLE_RELEASE = __ATOMIC_HLE_RELEASE;
// #else
// static constexpr int HLE_ACQUIRE = 0;
// static constexpr int HLE_RELEASE = 0;
// #endif
// public:
// using scoped_lock = std::lock_guard<Spinlock>;
// SpinlockHle(SpinlockHle const&) = delete;
// SpinlockHle& operator=(SpinlockHle const&) = delete;
// void lock() noexcept {
// for(int expected = 0;
// !__atomic_compare_exchange_n(&lock_, &expected, 1, false, __ATOMIC_ACQUIRE | HLE_ACQUIRE, __ATOMIC_RELAXED);
// expected = 0)
// spin_loop_pause();
// }
// void unlock() noexcept {
// __atomic_store_n(&lock_, 0, __ATOMIC_RELEASE | HLE_RELEASE);
// }
// };
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// class AdaptiveMutex {
// pthread_mutex_t m_;
// public:
// using scoped_lock = std::lock_guard<AdaptiveMutex>;
// AdaptiveMutex() noexcept {
// pthread_mutexattr_t a;
// if(ATOMIC_QUEUE_UNLIKELY(::pthread_mutexattr_init(&a)))
// std::abort();
// if(ATOMIC_QUEUE_UNLIKELY(::pthread_mutexattr_settype(&a, PTHREAD_MUTEX_ADAPTIVE_NP)))
// std::abort();
// if(ATOMIC_QUEUE_UNLIKELY(::pthread_mutex_init(&m_, &a)))
// std::abort();
// if(ATOMIC_QUEUE_UNLIKELY(::pthread_mutexattr_destroy(&a)))
// std::abort();
// m_.__data.__spins = 32767;
// }
// AdaptiveMutex(AdaptiveMutex const&) = delete;
// AdaptiveMutex& operator=(AdaptiveMutex const&) = delete;
// ~AdaptiveMutex() noexcept {
// if(ATOMIC_QUEUE_UNLIKELY(::pthread_mutex_destroy(&m_)))
// std::abort();
// }
// void lock() noexcept {
// if(ATOMIC_QUEUE_UNLIKELY(::pthread_mutex_lock(&m_)))
// std::abort();
// }
// void unlock() noexcept {
// if(ATOMIC_QUEUE_UNLIKELY(::pthread_mutex_unlock(&m_)))
// std::abort();
// }
// };
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
} // namespace atomic_queue
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#endif // ATOMIC_QUEUE_SPIN_LOCK_H_INCLUDED
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