ceph/src/boost/libs/smart_ptr/include/boost/smart_ptr/detail/spinlock_std_atomic.hpp

   1 #ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_STD_ATOMIC_HPP_INCLUDED
   2 #define BOOST_SMART_PTR_DETAIL_SPINLOCK_STD_ATOMIC_HPP_INCLUDED
   3
   4 // MS compatible compilers support #pragma once
   5
   6 #if defined(_MSC_VER) && (_MSC_VER >= 1020)
   7 # pragma once
   8 #endif
   9
  10 //
  11 //  Copyright (c) 2014 Peter Dimov
  12 //
  13 //  Distributed under the Boost Software License, Version 1.0.
  14 //  See accompanying file LICENSE_1_0.txt or copy at
  15 //  http://www.boost.org/LICENSE_1_0.txt)
  16 //
  17
  18 #include <boost/smart_ptr/detail/yield_k.hpp>
  19 #include <atomic>
  20
  21 namespace boost
  22 {
  23
  24 namespace detail
  25 {
  26
  27 class spinlock
  28 {
  29 public:
  30
  31     std::atomic_flag v_;
  32
  33 public:
  34
  35     bool try_lock()
  36     {
  37         return !v_.test_and_set( std::memory_order_acquire );
  38     }
  39
  40     void lock()
  41     {
  42         for( unsigned k = 0; !try_lock(); ++k )
  43         {
  44             boost::detail::yield( k );
  45         }
  46     }
  47
  48     void unlock()
  49     {
  50         v_ .clear( std::memory_order_release );
  51     }
  52
  53 public:
  54
  55     class scoped_lock
  56     {
  57     private:
  58
  59         spinlock & sp_;
  60
  61         scoped_lock( scoped_lock const & );
  62         scoped_lock & operator=( scoped_lock const & );
  63
  64     public:
  65
  66         explicit scoped_lock( spinlock & sp ): sp_( sp )
  67         {
  68             sp.lock();
  69         }
  70
  71         ~scoped_lock()
  72         {
  73             sp_.unlock();
  74         }
  75     };
  76 };
  77
  78 } // namespace detail
  79 } // namespace boost
  80
  81 #define BOOST_DETAIL_SPINLOCK_INIT { ATOMIC_FLAG_INIT }
  82
  83 #endif // #ifndef BOOST_SMART_PTR_DETAIL_SPINLOCK_STD_ATOMIC_HPP_INCLUDED