smart_ptr/detail/spinlock_std_atomic.hpp

0001 #ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_STD_ATOMIC_HPP_INCLUDED
0002 #define BOOST_SMART_PTR_DETAIL_SPINLOCK_STD_ATOMIC_HPP_INCLUDED
0003
0004 // MS compatible compilers support #pragma once
0005
0006 #if defined(_MSC_VER) && (_MSC_VER >= 1020)
0007 # pragma once
0008 #endif
0009
0010 //
0011 //  Copyright (c) 2014 Peter Dimov
0012 //
0013 //  Distributed under the Boost Software License, Version 1.0.
0014 //  See accompanying file LICENSE_1_0.txt or copy at
0015 //  http://www.boost.org/LICENSE_1_0.txt)
0016 //
0017
0018 #include <boost/smart_ptr/detail/yield_k.hpp>
0019 #include <atomic>
0020
0021 #if defined(BOOST_SP_REPORT_IMPLEMENTATION)
0022
0023 #include <boost/config/pragma_message.hpp>
0024 BOOST_PRAGMA_MESSAGE("Using std::atomic spinlock")
0025
0026 #endif
0027
0028 namespace boost
0029 {
0030
0031 namespace detail
0032 {
0033
0034 class spinlock
0035 {
0036 public:
0037
0038     std::atomic_flag v_;
0039
0040 public:
0041
0042     bool try_lock() noexcept
0043     {
0044         return !v_.test_and_set( std::memory_order_acquire );
0045     }
0046
0047     void lock() noexcept
0048     {
0049         for( unsigned k = 0; !try_lock(); ++k )
0050         {
0051             boost::detail::yield( k );
0052         }
0053     }
0054
0055     void unlock() noexcept
0056     {
0057         v_ .clear( std::memory_order_release );
0058     }
0059
0060 public:
0061
0062     class scoped_lock
0063     {
0064     private:
0065
0066         spinlock & sp_;
0067
0068         scoped_lock( scoped_lock const & );
0069         scoped_lock & operator=( scoped_lock const & );
0070
0071     public:
0072
0073         explicit scoped_lock( spinlock & sp ) noexcept: sp_( sp )
0074         {
0075             sp.lock();
0076         }
0077
0078         ~scoped_lock() /*noexcept*/
0079         {
0080             sp_.unlock();
0081         }
0082     };
0083 };
0084
0085 } // namespace detail
0086 } // namespace boost
0087
0088 #define BOOST_DETAIL_SPINLOCK_INIT { ATOMIC_FLAG_INIT }
0089
0090 #endif // #ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_STD_ATOMIC_HPP_INCLUDED